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1.  Human airway xenograft models of epithelial cell regeneration 
Respiratory Research  2000;1(3):125-128.
Regeneration and restoration of the airway epithelium after mechanical, viral or bacterial injury have a determinant role in the evolution of numerous respiratory diseases such as chronic bronchitis, asthma and cystic fibrosis. The study in vivo of epithelial regeneration in animal models has shown that airway epithelial cells are able to dedifferentiate, spread, migrate over the denuded basement membrane and progressively redifferentiate to restore a functional respiratory epithelium after several weeks. Recently, human tracheal xenografts have been developed in immunodeficient severe combined immunodeficiency (SCID) and nude mice. In this review we recall that human airway cells implanted in such conditioned host grafts can regenerate a well-differentiated and functional human epithelium; we stress the interest in these humanized mice in assaying candidate progenitor and stem cells of the human airway mucosa.
PMCID: PMC59558  PMID: 11667974
airway cell differentiation; airway cell proliferation; human airway epithelium; nude mouse; regeneration; SCID mouse; stem cell; xenograft
2.  NOD-Like Receptors in Intestinal Homeostasis and Epithelial Tissue Repair 
The intestinal epithelium constitutes a dynamic physical barrier segregating the luminal content from the underlying mucosal tissue. Following injury, the epithelial integrity is restored by rapid migration of intestinal epithelial cells (IECs) across the denuded area in a process known as wound healing. Hence, through a sequence of events involving restitution, proliferation and differentiation of IECs the gap is resealed and homeostasis reestablished. Relapsing damage followed by healing of the inflamed mucosa is a hallmark of several intestinal disorders including inflammatory bowel diseases (IBD). While several regulatory peptides, growth factors and cytokines stimulate restitution of the epithelial layer after injury, recent evidence in the field underscores the contribution of innate immunity in controlling this process. In particular, nucleotide-binding and oligomerization domain-like receptors (NLRs) play critical roles in sensing the commensal microbiota, maintaining homeostasis, and regulating intestinal inflammation. Here, we review the process of intestinal epithelial tissue repair and we specifically focus on the impact of NLR-mediated signaling mechanisms involved in governing epithelial wound healing during disease.
PMCID: PMC4100112  PMID: 24886810
nucleotide-binding and oligomerization domain-like receptors (NLRs); intestinal epithelial cells (IECs); wound healing; colitis; inflammatory bowel diseases (IBD); inflammasome; growth factors; innate immunity; toll-like receptors (TLRs)
3.  Trefoil peptides promote epithelial migration through a transforming growth factor beta-independent pathway. 
Journal of Clinical Investigation  1994;94(1):376-383.
The trefoil peptides, a recently recognized family of protease-resistant peptides, expressed in a regional specific pattern throughout the normal gastrointestinal tract. Although these peptides have been hypothesized to act as growth factors, their functional properties are largely unknown. Addition of recombinant trefoil peptides human spasmolytic polypeptide (HSP), rat and human intestinal trefoil factor (RITF and HITF) to subconfluent nontransformed rat intestinal epithelial cell lines (IEC-6 and IEC-17), human colon cancer-derived cell lines (HT-29 and CaCO2) or nontransformed fibroblasts (NRK and BHK) had no significant effect on proliferation. However addition of the trefoil peptides to wounded monolayers of confluent IEC-6 cells in an in vitro model of epithelial restitution resulted in a 3-6-fold increase in the rate of epithelial migration into the wound. Stimulation of restitution by the trefoil peptide HSP was enhanced in a cooperative fashion by the addition of mucin glycoproteins purified from the colon or small intestine of either rat or man, achieving up to a 15-fold enhancement in restitution. No synergistic effect was observed by the addition of nonmucin glycoproteins. In contrast to cytokine stimulation of intestinal epithelial cell restitution which is mediated through enhanced TGF beta bioactivity, trefoil peptide, and trefoil peptide-mucin glycoprotein stimulation of restitution was not associated with alteration in concentrations of bioactive TGF-beta and was not affected by the presence of immunoneutralizing anti-TGF beta antiserum. Collectively, these findings suggest that the trefoil peptides which are secreted onto the lumenal surface of the gastrointestinal tract may act in conjunction with the mucin glycoprotein products of goblet cells to promote reestablishment of mucosal integrity after injury through mechanisms distinct from those which may act at the basolateral pole of the epithelium.
PMCID: PMC296319  PMID: 8040278
4.  Caveolin‐1 enhances rapid mucosal restitution by activating TRPC1‐mediated Ca2+ signaling 
Physiological Reports  2014;2(11):e12193.
Early rapid mucosal restitution occurs as a consequence of epithelial cell migration to reseal superficial wounds, a process independent of cell proliferation. Our previous studies revealed that the canonical transient receptor potential‐1 (TRPC1) functions as a store‐operated Ca2+ channel (SOCs) in intestinal epithelial cells (IECs) and regulates epithelial restitution after wounding, but the exact mechanism underlying TRPC1 activation remains elusive. Caveolin‐1 (Cav1) is a major component protein that is associated with caveolar lipid rafts in the plasma membrane and was recently identified as a regulator of store‐operated Ca2+ entry (SOCE). Here, we showed that Cav1 plays an important role in the regulation of mucosal restitution by activating TRPC1‐mediated Ca2+ signaling. Target deletion of Cav1 delayed gastric mucosal repair after exposure to hypertonic NaCl in mice, although it did not affect total levels of TRPC1 protein. In cultured IECs, Cav1 directly interacted with TRPC1 and formed Cav1/TRPC1 complex as measured by immunoprecipitation assays. Cav1 silencing in stable TRPC1‐transfected cells by transfection with siCav1 reduced SOCE without effect on the level of resting [Ca2+]cyt. Inhibition of Cav1 expression by siCav1 and subsequent decrease in Ca2+ influx repressed epithelial restitution, as indicated by a decrease in cell migration over the wounded area, whereas stable ectopic overexpression of Cav1 increased Cav1/TRPC1 complex, induced SOCE, and enhanced cell migration after wounding. These results indicate that Cav1 physically interacts with and activates TRPC1, thus stimulating TRPC1‐mediated Ca2+ signaling and rapid mucosal restitution after injury.
Early rapid mucosal restitution occurs as a consequence of epithelial cell migration to reseal superficial wounds, a process independent of cell proliferation. Caveolin‐1 (Cav1) is a major component protein that is associated with caveolar lipid rafts in the plasma membrane and was recently identified as a regulator of store‐operated Ca2+ entry (SOCE). Our results indicate that Cav1 physically interacts with and activates TRPC1, thus stimulating TRPC1‐mediated Ca2+ signaling and rapid mucosal restitution after injury.
PMCID: PMC4255804  PMID: 25367694
Ca2+ influx; Cav−/−mice; cell migration; cyclopiazonic acid; hypertonic NaCl injury; intracellular Ca2+; TRPC1
5.  Repair of damaged intestinal mucosa in a mouse model of sepsis 
The intestine is not only the main target attacked by sepsis but also the vital organ which mediated sepsis. The recovery of the damaged intestinal barrier structure and function is related to the occurrence and outcome of multiple organ dysfunction syndrome (MODS). How to protect and reduce the damage of the intestinal mucosa and how to promote the reconstruction of the intestinal mucosa have been the important topics in sepsis for many years. This study aimed to investigate the influential factors of intestinal mucosal reconstruction after intestinal epithelial injury in vivo in a mouse model of sepsis.
Mice were subjected to cecal ligation and puncture (CLP) for induction of sepsis to assess intestinal mucosal damage, epithelial cell apoptosis, and transformed number of goblet cells, and to detect the concentration of TNF-α, IL-1 and TGF-β1 and TFF3 (trefoil factor 3) expression in the small intestinal mucosa. All above were performed by HE staining, western blot, ELISA and immunohistochemistry respectively. The experimental animals were divided into a sepsis group and a sham-operation group. The animals with sepsis were separately killed at 6 (7 animals), 24 (7 animals) and 48 hours (7 animals) after CLP.
Injured intestinal mucosa was observed in the 3 groups under a light microscope, in which damage scores in the 24-hour and 48-hour groups were higher than in the 6-hour group and no difference was found between the two groups. Moreover, less of goblet cells or other epithelial cells adjacent to the injured surface migrated into the wound to cover the denuded area. The number of goblet cells was substantially decreased in the three CLP groups compared with the sham-operation group. Protein levels of IL-1 and TNF-α were significantly increased by 3–4 fold at all time points when compared with the sham-operation group, and cleaved caspase-3 by 4 fold. Although TFF3 expression was modestly increased for 6 hours after the onset of CLP, it appeared to decline at 24 hours and 48 hours as shown by Western blot. A similar tendency was observed upon TGF-β1, i.e. the protein level was not elevated at 24 hours and 48 hours, but increased modestly at 6 hours.
Sepsis from CLP shows less restitution on the surface of injured intestinal mucosa. There is evidence that both constant inflammatory reaction and epithelial cell apoptosis may affect mucosal reestablishment of the intestine at the onset of sepsis. Mucosa after severe sepsis showed the state of high inflammation, and declined goblet cell function and mucosal reconstruction, which affected the repair of damaged intestinal barrier. Constant inflammatory reaction, and declined goblet cell function and mucosal reconstruction ability may affect the reestablishment of intestinal mucosa at the onset of sepsis.
PMCID: PMC4129853  PMID: 25215123
Sepsis; Cecal ligation and puncture; Intestinal mucosa; Restitution; Goblet cells; Intestinal trefoil factor 3; Transforming growth factor β1; Cysteine-containing aspartate-specific proteases
6.  Budesonide and formoterol effects on rhinovirus replication and epithelial cell cytokine responses 
Respiratory Research  2013;14(1):98.
Combination therapy with budesonide and formoterol reduces exacerbations of asthma, which are closely associated with human rhinovirus (RV) infections in both children and adults. These data suggest that budesonide and formoterol inhibit virus-induced inflammatory responses of airway epithelial cells.
To test this hypothesis, bronchial epithelial (BE) cells were obtained from airway brushings of 8 subjects with moderate-to-severe allergic asthma and 9 with neither asthma nor respiratory allergies. Cultured BE cells were incubated for 24 hours with budesonide (1.77 μM), formoterol (0.1 μM), both, or neither, and then inoculated with RV-16 (5×106 plaque forming units [PFU]/mL). After 24 hours, viral replication (RV RNA), cytokine secretion (CXCL8, CXCL10, TNFα, IFN-β, IL-28) and mRNA expression (CXCL8, CXCL10, TNF, IFNB1, IL28A&B) were analyzed.
RV infection induced CXCL10 protein secretion and IFNB1 and IL28 mRNA expression. Drug treatments significantly inhibited secretion of CXCL10 in mock-infected, but not RV-infected, BE cells, and inhibited secretion of TNFα under both conditions. Neither budesonide nor formoterol, alone or in combination, significantly affected viral replication, nor did they inhibit RV-induced upregulation of IFNB1 and IL28 mRNA. Overall, RV replication was positively related to CXCL10 secretion and induction of IFNB1 and IL28 mRNA, but the positive relationship between RV RNA and CXCL10 secretion was stronger in normal subjects than in subjects with asthma.
Budesonide and formoterol can inhibit BE cell inflammatory responses in vitro without interfering with viral replication or production of interferons. These effects could potentially contribute to beneficial effects of budesonide/formoterol combination therapy in preventing RV-induced asthma exacerbations.
PMCID: PMC3851834  PMID: 24219422
Budesonide; Formoterol; Human rhinovirus; Bronchial epithelial cells; Asthma
7.  Prostaglandin-mediated closure of paracellular pathway and not restitution is the primary determinant of barrier recovery in acutely injured porcine ileum 
Small bowel epithelium is at the frontline of intestinal barrier function. Restitution is considered to be the major determinant of epithelial repair as function recovers in parallel with restitution after acute injury. As such, studies of intact mucosa have largely been replaced by migration assays of cultured epithelia. These latter studies fail to account for the simultaneous roles played by villous contraction and paracellular permeability in recovery of barrier function. Non-steroidal anti-inflammatory drugs (NSAID) result in increased intestinal permeability and disease exacerbation in patients with IBD. Thus, we examined the reparative attributes of endogenous prostaglandins (PG) after injury of ileal mucosa by deoxycholate (6 mM) in Ussing chambers. Recovery of transepithelial resistance (TER) from 20–40 Ω.cm2 was abolished by indomethacin (INDO), whereas restitution of 40–100% of the villous surface was unaffected despite concurrent arrest of villous contraction. In the presence of PG, resident crypt and migrating epithelial cells were tightly apposed. In tissues treated with INDO, crypt epithelial cells had dilated intercellular spaces that were accentuated in the migrating epithelium. TER was fully rescued from the effects of INDO by osmotic-driven collapse of the paracellular space and PG-mediated recovery was significantly impaired by blockade of Cl− secretion. These studies are the first to clearly distinguish the relative contribution of paracellular resistance versus restitution to acute recovery of epithelial barrier function. Restitution was ineffective in the absence of PG-mediated paracellular space closure. Failure of PG-mediated repair mechanisms may underlie barrier failure resulting from NSAID use in patients with underlying enteropathy.
PMCID: PMC2443786  PMID: 12801887
resistance; permeability; tight junction; deoxycholate
8.  Mechanical compression attenuates normal human bronchial epithelial wound healing 
Respiratory Research  2009;10(1):9.
Airway narrowing associated with chronic asthma results in the transmission of injurious compressive forces to the bronchial epithelium and promotes the release of pro-inflammatory mediators and the denudation of the bronchial epithelium. While the individual effects of compression or denudation are well characterized, there is no data to elucidate how these cells respond to the application of mechanical compression in the presence of a compromised epithelial layer.
Accordingly, differentiated normal human bronchial epithelial cells were exposed to one of four conditions: 1) unperturbed control cells, 2) single scrape wound only, 3) static compression (6 hours of 30 cmH2O), and 4) 6 hours of static compression after a scrape wound. Following treatment, wound closure rate was recorded, media was assayed for mediator content and the cytoskeletal network was fluorescently labeled.
We found that mechanical compression and scrape injury increase TGF-β2 and endothelin-1 secretion, while EGF content in the media is attenuated with both injury modes. The application of compression after a pre-existing scrape wound augmented these observations, and also decreased PGE2 media content. Compression stimulated depolymerization of the actin cytoskeleton and significantly attenuated wound healing. Closure rate was partially restored with the addition of exogenous PGE2, but not EGF.
Our results suggest that mechanical compression reduces the capacity of the bronchial epithelium to close wounds, and is, in part, mediated by PGE2 and a compromised cytoskeleton.
PMCID: PMC2672070  PMID: 19171062
9.  Cultured corneal epithelia for ocular surface disease. 
PURPOSE: To evaluate the potential efficacy for autologous and allogeneic expanded corneal epithelial cell transplants derived from harvested limbal corneal epithelial stem cells cultured in vitro for the management of ocular surface disease. METHODS: Human Subjects. Of the 19 human subjects included, 18 (20 procedures) underwent in vitro cultured corneal epithelial cell transplants using various carriers for the epithelial cells to determine the most efficacious approach. Sixteen patients (18 procedures on 17 eyes) received autologous transplants, and 2 patients (1 procedure each) received allogeneic sibling grafts. The presumed corneal epithelial stem cells from 1 patient did not grow in vitro. The carriers for the expanded corneal epithelial cells included corneal stroma, type 1 collagen (Vitrogen), soft contact lenses, collagen shields, and amniotic membrane for the autologous grafts and only amniotic membrane for the allogeneic sibling grafts. Histologic confirmation was reviewed on selected donor grafts. Amniotic membrane as carrier. Further studies were made to determine whether amniotic membrane might be the best carrier for the expanding corneal epithelial cells. Seventeen different combinations of tryspinization, sonication, scraping, and washing were studied to find the simplest, most effective method for removing the amniotic epithelium while still preserving the histologic appearance of the basement membrane of the amnion. Presumed corneal epithelial stem cells were harvested and expanded in vitro and applied to the amniotic membrane to create a composite graft. Thus, the composite graft consisted of the amniotic membrane from which the original epithelium had been removed without significant histologic damage to the basement membrane, and the expanded corneal epithelial stem cells, which had been applied to and had successfully adhered to the denuded amniotic membrane. Animal model. Twelve rabbits had the ocular surface of 1 eye damaged in a standard manner with direct removal of the presumed limbal stem cells, corneal epithelium, and related epithelium, followed by the application of n-heptanol for 60 seconds. After 6 weeks, all damaged eyes were epithelialized and vascularized. Two such treated eyes were harvested without further treatment, to be used for histologic study as damaged controls. The remaining 10 rabbits received composite grafts (consisting of amniotic membrane with expanded allogeneic rabbit corneal epithelial cell transplants) applied to the ocular surface in a standard manner followed by the application of a contact lens. At 16 days following transplantation, 5 of the rabbits were sacrificed and the corneal rims were removed for histologic study. At 28 days, the remaining rabbits were sacrificed and the previously damaged eyes were harvested for histologic and immunohistochemical study. RESULTS: Human subjects. Of the 19 total patients admitted to the study, the presumed corneal epithelial stem cells of 1 patient did not grow in vitro. Of the remaining 18 patients (20 procedures, 19 eyes), 3 patients had unsuccessful results (3 autologous procedures), 1 patient had a partially successful procedure (allogeneic procedure), and 1 patient had a procedure with an undetermined result at present (allogeneic procedure). One unsuccessful patient had entropion/trichiasis and mechanically removed the graft and eventually went into phthisis. The other 2 unsuccessful patients suffered presumed loss of autologous donor epithelium and recurrence of the ocular surface disease (pterygium). The partially successful patient receiving an allogeneic transplant had infectious keratitis delay of his re-epithelialization; he has only minimal visual improvement but has re-epithelialized. The patient receiving the second allogeneic graft lost his donor epithelium at day 4. Additional donor epithelium was reapplied, but the result is undetermined at present. Amniotic membrane as carrier. The in vitro preparation of the amniotic membrane with corneal epithelial stem cell graft overlay was successful.Histology documented removal of the amniotic epithelium and reapplication of corneal epithelial cells. Animal model. The 2 rabbits that had no reparative surgery following standard ocular surface injury had histology and immunopathology consistent with incomplete corneal epithelial stem cell failure with vascularization and scarring of the ocular surface. Light microscopy and immunohistologic staining with AE5 confirmed the conjunctival phenotype of the ocular surface repair but also documented the incomplete model. The allogeneic stern cell transplants had varying results. One rabbit had a suppurative infection and lost the graft. Reparative surgery failed in 2 of the rabbits, failed partially in 3 of the rabbits, was partially successful in 3 others, and was successful in 1 rabbit at 28 days. Histologic and immunopathologic study documented successful growth of corneal epithelium onto the recipient surface. CONCLUSIONS: 1. Presumed corneal epithelial stem cells can be harvested safely from the limbus and expanded successfully in vitro. 2. Expanded corneal epithelial cell cultures can be grown onto various carriers, but currently denuded amniotic membrane seems to be the best carrier for ocular surface repair. 3. Expanded corneal epithelial cell transplants appear to resurface damaged ocular surfaces successfully, but cellular tracking and further confirmation are required. 4. Expanded allogeneic corneal epithelial cell transplants are technically possible and may represent alternative treatment modalities for selected ocular surface problems. 5. These techniques potentially offer a new method of restoring a normal ocular surface while minimizing the threat of damage or depletion to the contralateral or sibling limbal corneal epithelial stem cells. 6. The rabbit model was probably incomplete and should be interpreted with caution. The complete eradication of all corneal epithelial stem cells from any eye is difficult, making confirmation of such work challenging. 7. The results of the rabbit model suggest that allogeneic grafts may restore a nearly normal ocular epithelial surface to certain ocular surface injuries.
PMCID: PMC1298283  PMID: 10703147
10.  Protective effect of budesonide/formoterol compared with formoterol, salbutamol and placebo on repeated provocations with inhaled AMP in patients with asthma: a randomised, double-blind, cross-over study 
Respiratory Research  2010;11(1):66.
The budesonide/formoterol combination is successfully used for fast relief of asthma symptoms in addition to its use as maintenance therapy. The temporarily increased corticosteroid dose during increasing inhaler use for symptom relief is likely to suppress any temporary increase in airway inflammation and may mitigate or prevent asthma exacerbations. The relative contribution of the budesonide and formoterol components to the improved asthma control is unclear.
The acute protective effect of inhaled budesonide was tested in a model of temporarily increased airway inflammation with repeated indirect airway challenges, mimicking an acute asthma exacerbation. A randomised, double-blind, cross-over study design was used. Asthmatic patients (n = 17, mean FEV1 95% of predicted) who previously demonstrated a ≥30% fall in forced expiratory volume in 1 second (FEV1) after inhaling adenosine 5'-monophosphate (AMP), were challenged on four consecutive test days, with the same dose of AMP (at 09:00, 12:00 and 16:00 hours). Within 1 minute of the maximal AMP-induced bronchoconstriction at 09:00 hours, the patients inhaled one dose of either budesonide/formoterol (160/4.5 μg), formoterol (4.5 μg), salbutamol (2 × 100 μg) or placebo. The protective effects of the randomised treatments were assessed by serial lung function measurements over the test day.
In the AMP provocations at 3 and 7 hours after inhalation, the budesonide/formoterol combination provided a greater protective effect against AMP-induced bronchoconstriction compared with formoterol alone, salbutamol and placebo. In addition all three active treatments significantly increased FEV1 within 3 minutes of administration, at a time when inhaled AMP had induced the 30% fall in FEV1.
A single dose of budesonide/formoterol provided a greater protective effect against inhaled AMP-induced bronchoconstriction than formoterol alone, both at 3 and at 7 hours after inhalation. The acute protection against subsequent bronchoconstrictor stimuli such as inhaled AMP and the rapid reversal of airway obstruction supports the use of budesonide/formoterol for both relief and prevention in the treatment of asthma.
Trial Registration number NCT00272753
PMCID: PMC2890647  PMID: 20509942
11.  Epithelial barrier formation by airway basal cells 
Thorax  1997;52(3):213-217.
BACKGROUND: Epithelial shedding processes in airway inflammation and defence may produce damaged areas where basal cells are the main remaining epithelial cell type. The present study examines the capacity of basal cells to form an epithelial barrier structure after loss of columnar epithelial cells. METHODS: A technique was developed which allows selective removal of columnar epithelial cells from isolated airways. A drop of tissue adhesive glue was applied on the mucosal surface shortly after excision of guinea pig trachea and human bronchus. Gentle removal of the glue, together with attached columnar cells, left a single layer of cobbled, solitary basal cells. The tissue was kept in culture media. Morphological changes of the basal cells were monitored by immuno-histochemistry and scanning and transmission electron microscopy at several time points. RESULTS: After 20 minutes the basal cells had undergone extensive flattening and established contact with each other. The basement membrane thus became covered by a poorly differentiated epithelium in both guinea pig and human airways. Abundant interdigitating cytoplasmic protrusions were observed at cell borders. CONCLUSIONS: Basal cells promptly flatten out to cover the basement membrane at loss of neighbouring columnar cells. These data may explain why the epithelial barrier function may be uncompromised in desquamative airway diseases. Furthermore, they suggest the possibility that sacrificial release of columnar epithelial cells and prompt creation of a barrier structure constitute important roles of basal cells in airway defence against severe insults. 

PMCID: PMC1758525  PMID: 9093334
12.  Randomised controlled trial of montelukast plus inhaled budesonide versus double dose inhaled budesonide in adult patients with asthma 
Thorax  2003;58(3):211-216.
Background: Inhaled corticosteroids (ICS) affect many inflammatory pathways in asthma but have little impact on cysteinyl leukotrienes. This may partly explain persistent airway inflammation during chronic ICS treatment and failure to achieve adequate asthma control in some patients. This double blind, randomised, parallel group, non-inferiority, multicentre 16 week study compared the clinical benefits of adding montelukast to budesonide with doubling the budesonide dose in adults with asthma.
Methods: After a 1 month single blind run in period, patients inadequately controlled on inhaled budesonide (800 µg/day) were randomised to receive montelukast 10 mg + inhaled budesonide 800 µg/day (n=448) or budesonide 1600 µg/day (n=441) for 12 weeks.
Results: Both groups showed progressive improvement in several measures of asthma control compared with baseline. Mean morning peak expiratory flow (AM PEF) improved similarly in the last 10 weeks of treatment compared with baseline in both the montelukast + budesonide group and in the double dose budesonide group (33.5 v 30.1 l/min). During days 1–3 after start of treatment, the change in AM PEF from baseline was significantly greater in the montelukast + budesonide group than in the double dose budesonide group (20.1 v 9.6 l/min, p<0.001), indicating faster onset of action in the montelukast group. Both groups showed similar improvements with respect to "as needed" ß agonist use, mean daytime symptom score, nocturnal awakenings, exacerbations, asthma free days, peripheral eosinophil counts, and asthma specific quality of life. Both montelukast + budesonide and double dose budesonide were generally well tolerated.
Conclusion: The addition of montelukast to inhaled budesonide is an effective and well tolerated alternative to doubling the dose of inhaled budesonide in adult asthma patients experiencing symptoms and inadequate control on budesonide alone.
PMCID: PMC1746596  PMID: 12612295
13.  Airway Epithelium Stimulates Smooth Muscle Proliferation 
Communication between the airway epithelium and stroma is evident during embryogenesis, and both epithelial shedding and increased smooth muscle proliferation are features of airway remodeling. Hence, we hypothesized that after injury the airway epithelium could modulate airway smooth muscle proliferation. Fully differentiated primary normal human bronchial epithelial (NHBE) cells at an air–liquid interface were co-cultured with serum-deprived normal primary human airway smooth muscle cells (HASM) using commercially available Transwells. In some co-cultures, the NHBE were repeatedly (×4) scrape-injured. An in vivo model of tracheal injury consisted of gently denuding the tracheal epithelium (×3) of a rabbit over 5 days and then examining the trachea by histology 3 days after the last injury. Our results show that HASM cell number increases 2.5-fold in the presence of NHBE, and 4.3-fold in the presence of injured NHBE compared with HASM alone after 8 days of in vitro co-culture. In addition, IL-6, IL-8, monocyte chemotactic protein (MCP)-1 and, more markedly, matrix metalloproteinase (MMP)-9 concentration increased in co-culture correlating with enhanced HASM growth. Inhibiting MMP-9 release significantly attenuated the NHBE-dependent HASM proliferation in co-culture. In vivo, the injured rabbit trachea demonstrated proliferation in the smooth muscle (trachealis) region and significant MMP-9 staining, which was absent in the uninjured control. The airway epithelium modulates smooth muscle cell proliferation via a mechanism that involves secretion of soluble mediators including potential smooth muscle mitogens such as IL-6, IL-8, and MCP-1, but also through a novel MMP-9–dependent mechanism.
PMCID: PMC2742749  PMID: 19151317
remodeling; NHBE; injury; MMP-9; HASM
14.  Role of acetylcholine and polyspecific cation transporters in serotonin-induced bronchoconstriction in the mouse 
Respiratory Research  2006;7(1):65.
It has been proposed that serotonin (5-HT)-mediated constriction of the murine trachea is largely dependent on acetylcholine (ACh) released from the epithelium. We recently demonstrated that ACh can be released from non-neuronal cells by corticosteroid-sensitive polyspecific organic cation transporters (OCTs), which are also expressed by airway epithelial cells. Hence, the hypothesis emerged that 5-HT evokes bronchoconstriction by inducing release of ACh from epithelial cells via OCTs.
We tested this hypothesis by analysing bronchoconstriction in precision-cut murine lung slices using OCT and muscarinic ACh receptor knockout mouse strains. Epithelial ACh content was measured by HPLC, and the tissue distribution of OCT isoforms was determined by immunohistochemistry.
Epithelial ACh content was significantly higher in OCT1/2 double-knockout mice (42 ± 10 % of the content of the epithelium-denuded trachea, n = 9) than in wild-type mice (16.8 ± 3.6 %, n = 11). In wild-type mice, 5-HT (1 μM) caused a bronchoconstriction that slightly exceeded that evoked by muscarine (1 μM) in intact bronchi but amounted to only 66% of the response to muscarine after epithelium removal. 5-HT-induced bronchoconstriction was undiminished in M2/M3 muscarinic ACh receptor double-knockout mice which were entirely unresponsive to muscarine. Corticosterone (1 μM) significantly reduced 5-HT-induced bronchoconstriction in wild-type and OCT1/2 double-knockout mice, but not in OCT3 knockout mice. This effect persisted after removal of the bronchial epithelium. Immunohistochemistry localized OCT3 to the bronchial smooth muscle.
The doubling of airway epithelial ACh content in OCT1/2-/- mice is consistent with the concept that OCT1 and/or 2 mediate ACh release from the respiratory epithelium. This effect, however, does not contribute to 5-HT-induced constriction of murine intrapulmonary bronchi. Instead, this activity involves 1) a non-cholinergic epithelium-dependent component, and 2) direct stimulation of bronchial smooth muscle cells, a response which is partly sensitive to acutely administered corticosterone acting on OCT3. These data provide new insights into the mechanisms involved in 5-HT-induced bronchoconstriction, including novel information about non-genomic, acute effects of corticosteroids on bronchoconstriction.
PMCID: PMC1468398  PMID: 16608531
15.  Free radical activity and pro-inflammatory effects of particulate air pollution (PM10) in vivo and in vitro. 
Thorax  1996;51(12):1216-1222.
BACKGROUND: Epidemiological evidence has implicated fine particulate air pollution, particularly particles less than 10 microns in diameter (PM10), in the development of exacerbations of asthma and chronic obstructive pulmonary disease (COPD) although the mechanism is unknown. The hypothesis that PM10 particles induce oxidant stress, causing inflammation and injury to airway epithelium, was tested. METHODS: The effects of intratracheal instillation of PM10 was assessed in rat lungs (three per group). Inflammatory cell influx was measured by bronchoalveolar lavage (BAL) and air space epithelial permeability was assessed as the total protein in BAL fluid in vivo. The oxidant properties of PM10 particles were determined by their ability to cause damage to plasmid DNA and by changes in reduced (GSH) and oxidised (GSSG) glutathione. The effects of PM10 particles were compared in some experiments with those of fine (CB) and ultrafine (ufCB) carbon black particles. RESULTS: Six hours after intratracheal instillation of PM10 there was an influx of neutrophils (up to 15% of total cells in BAL fluid) into the alveolar space, increased epithelial permeability, the mean (SE) total protein in the BAL fluid increasing from 0.39 (0.01) to 0.62 (0.01) mg/ml, and increased lactate dehydrogenase (LDH) concentrations in the BAL fluid. An even greater inflammatory response was seen following intratracheal instillation of ufCB but not following CB instillation. PM10 particles had free radical activity in vivo, as shown by a decrease in GSH levels in the BAL fluid from 0.36 (0.05) to 0.25 (0.01) nmol/ml following instillation. The free radical activity of PM10 was confirmed in vitro by its ability to deplete supercoiled plasmid DNA, an effect which could be reversed by mannitol, a specific hydroxyl radical scavenger. BAL fluid leucocytes from rats treated with PM10 produced greater amounts of nitric oxide (NO), measured as nitrite (control 3.07 (0.33), treated 4.45 (0.23) microM/1 x 10(6) cells), and tumour necrosis factor alpha (control 21.0 (3.1), treated 179.2 (29.4) units/l x 10(6) cells) in culture than those obtained from control animals. Since the PM10 preparation was contaminated with small amounts of filter fibres due to the extraction process, the effects of instillation of filter fibres alone was assessed. These studies showed that filter fibres did not account for the proinflammatory and injurious effects of the PM10 suspension. CONCLUSIONS: These findings provide evidence that PM10 has free radical activity and causes lung inflammation and epithelial injury. These data support the proposed hypothesis for the mechanism by which particulate air pollution causes adverse effects in patients with airways diseases.
PMCID: PMC472766  PMID: 8994518
16.  Budesonide suppresses pulmonary antibacterial host defense by down-regulating cathelicidin-related antimicrobial peptide in allergic inflammation mice and in lung epithelial cells 
BMC Immunology  2013;14:7.
Glucocorticoids are widely regarded as the most effective treatment for asthma. However, the direct impact of glucocorticoids on the innate immune system and antibacterial host defense during asthma remain unclear. Understanding the mechanisms underlying this process is critical to the clinical application of glucocorticoids for asthma therapy. After sensitization and challenge with ovalbumin (OVA), BALB/c mice were treated with inhaled budesonide and infected with Pseudomonas aeruginosa (P. aeruginosa). The number of viable bacteria in enflamed lungs was evaluated, and levels of interleukin-4 (IL-4) and interferon-γ (IFN-γ) in serum were measured. A lung epithelial cell line was pretreated with budesonide. Levels of cathelicidin-related antimicrobial peptide (CRAMP) were measured by immunohistochemistry and western blot analysis. Intracellular bacteria were observed in lung epithelial cells.
Inhaled budesonide enhanced lung infection in allergic mice exposed to P. aeruginosa and increased the number of viable bacteria in lung tissue. Higher levels of IL-4 and lower levels of IFN-γ were observed in the serum. Budesonide decreased the expression of CRAMP, increased the number of internalized P. aeruginosa in OVA-challenged mice and in lung epithelial cell lines. These data indicate that inhaled budesonide can suppress pulmonary antibacterial host defense by down-regulating CRAMP in allergic inflammation mice and in cells in vitro.
Inhaled budesonide suppressed pulmonary antibacterial host defense in an asthmatic mouse model and in lung epithelium cells in vitro. This effect was dependent on the down-regulation of CRAMP.
PMCID: PMC3583690  PMID: 23387852
Allergic airway inflammation; Antibacterial host defense; Cathelicidin; Budesonide
17.  Influenza Virus Infection Decreases Tracheal Mucociliary Velocity and Clearance of Streptococcus pneumoniae 
Influenza virus infections increase susceptibility to secondary bacterial infections, such as pneumococcal pneumonia, resulting in increased morbidity and mortality. Influenza-induced tissue damage is hypothesized to increase susceptibility to Streptococcus pneumoniae infection by increasing adherence to the respiratory epithelium. Using a mouse model of influenza infection followed by S. pneumoniae infection, we found that an influenza infection does not increase the number of pneumococci initially present within the trachea, but does inhibit pneumococcal clearance by 2 hours after infection. To determine whether influenza damage increases pneumococcal adherence, we developed a novel murine tracheal explant system to determine influenza-induced tissue damage and subsequent pneumococcal adherence. Murine tracheas were kept viable ex vivo as shown by microscopic examination of ciliary beating and cellular morphology using continuous media flow for up to 8 days. Tracheas were infected with influenza virus for 0.5–5 days ex vivo, and influenza-induced tissue damage and the early stages of repair to the epithelium were assessed histologically. A prior influenza infection did not increase pneumococcal adherence, even when the basement membrane was maximally denuded or during the repopulation of the basement membrane with undifferentiated epithelial cells. We measured mucociliary clearance in vivo and found it was decreased in influenza-infected mice. Together, our results indicate that exposure of the tracheal basement membrane contributes minimally to pneumococcal adherence. Instead, an influenza infection results in decreased tracheal mucociliary velocity and initial clearance of pneumococci, leading to an increased pneumococcal burden as early as 2 hours after pneumococcal infection.
PMCID: PMC2848738  PMID: 19520922
influenza virus; Streptococcus pneumoniae; mucociliary velocity; bacterial clearance and adherence; tracheal explants
18.  Bone morphogenetic proteins enhance an epithelial-mesenchymal transition in normal airway epithelial cells during restitution of a disrupted epithelium 
Respiratory Research  2013;14(1):36.
Mechanisms of airway repair are poorly understood. It has been proposed that, following injury, progenitor populations such as club cells (Clara) become undifferentiated, proliferate and re-differentiate to re-epithelialise the airway. The exact phenotype of such cells during repair is unknown however. We hypothesised that airway epithelial cells (AECs) undergo some degree of epithelial-mesenchymal transition (EMT) in order to migrate over a denuded airway and effect re-epithelialisation. Furthermore, based on our previous findings that BMP signalling is an early event in AECs following injury in vivo and that BMP4 down-regulates E-cadherin expression and enhances migration in AECs in vitro, we hypothesised that BMPs could play a role in inducing such a phenotypic switch.
Normal AECs were isolated from mouse lungs and analysed in a model of a disrupted epithelium. EMT marker expression and BMP signalling were examined by immunofluorescence, Western blotting and RT-PCR.
Following generation of a wound area, AECs at the wound edge migrated and acquired a mesenchymal-like morphology. E-cadherin expression was reduced in migrating cells while vimentin and α-smooth muscle actin (α-SMA) expression was increased. Re-expression of membrane E-cadherin was subsequently observed in some cells in the wound area following re-establishment of the monolayer. A transient increase in the incidence of nuclear phosphorylated Smad1/5/8 was observed in migrating cells compared with confluent cells, indicating active BMP signalling during migration. BMP antagonists noggin and gremlin inhibited cell migration, confirming the involvement of BMP signalling in migration and indicating autocrine signalling, possibly involving BMP7 or BMP4 which were expressed in AECs. Exogenous BMP2, BMP4 and BMP7 induced a mesenchymal-like morphology in AECs, enhanced the rate of cell migration and increased α-SMA protein expression in AECs.
Following disruption of an intact epithelium, migrating AECs at the wound edge acquire an EMT-like phenotype involving altered expression of E-cadherin, vimentin and α-SMA. BMP signalling is involved in AEC migration and is likely to mediate the switch towards an EMT-like phenotype by altering protein expression to facilitate cell migration and wound closure. We propose therefore that acquisition of an EMT-like phenotype by AECs is a normal aspect of wound repair. Furthermore, we suggest that diseases involving fibrosis may arise because the EMT phase of repair is prolonged by chronic injury/inflammation, rather than being caused by it, as is the current paradigm.
PMCID: PMC3607850  PMID: 23509993
Airway; Wound healing; Migration; BMP; EMT; Club cell (Clara)
19.  Systemic effects of high dose inhaled steroids: comparison of beclomethasone dipropionate and budesonide in healthy subjects. 
Thorax  1993;48(10):967-973.
ACKGROUND--Systemic absorption of inhaled corticosteroids may adversely influence the function of the hypothalamo-pituitary-adrenal axis, bone metabolism, and circulating leucocytes. These changes can be used to assess the safety of different types and modes of administration of these drugs. METHODS--The study was a randomised, double dummy, crossover design with nine healthy adults. It compared the effects of beclomethasone dipropionate and budesonide (given by metered dose aerosols with and without their respective large volume spacers (Volumatic and Nebuhaler) attached) on serum cortisol, 24 hour urinary free cortisol, and plasma osteocalcin concentrations, and circulating neutrophils and lymphocytes. Subjects inhaled the drug (1 mg) and matching placebo at 0900 and 2200 hours on each of six study days. Blood samples were taken hourly for six hours after the morning dose and at the end of the study period. RESULTS--All results were within the reference ranges. Both drugs caused similar reductions in serum cortisol four to six hours after inhalation. These changes were not affected by the use of a large spacer and did not persist at 24 hours. Use of spacers tended to increase the haematological effects of the steroids. Beclomethasone dipropionate inhaled through a Volumatic provoked a rise in circulating neutrophils compared with placebo although lymphocyte numbers were unaffected. Budesonide did not influence neutrophil numbers but did reduce circulating lymphocytes, numbers of which were further reduced when the Nebuhaler was used. There were no significant changes in plasma osteocalcin concentration or 24 hour urinary free cortisol excretion with budesonide, with or without a spacer. Beclomethasone dipropionate inhaled without a spacer reduced urinary cortisol and plasma osteocalcin at 24 hours; however, use of the Volumatic protected against these effects. CONCLUSIONS--Attaching a Volumatic reduces the systemic effects of 2 mg aerosol beclomethasone dipropionate on the hypothalamo-pituitary-adrenal axis and circulating osteocalcin concentrations. This study did not establish whether the Nebuhaler reduces the systemic effects of budesonide. When large spacers are used, 2 mg per day of beclomethasone dipropionate and budesonide seem to be equivalent in terms of unwanted effects.
PMCID: PMC464800  PMID: 8256242
20.  Epithelial restitution and wound healing in inflammatory bowel disease 
Inflammatory bowel disease is characterized by a chronic inflammation of the intestinal mucosa. The mucosal epithelium of the alimentary tract constitutes a key element of the mucosal barrier to a broad spectrum of deleterious substances present within the intestinal lumen including bacterial microorganisms, various dietary factors, gastrointestinal secretory products and drugs. In addition, this mucosal barrier can be disturbed in the course of various intestinal disorders including inflammatory bowel diseases. Fortunately, the integrity of the gastrointestinal surface epithelium is rapidly reestablished even after extensive destruction. Rapid resealing of the epithelial barrier following injuries is accomplished by a process termed epithelial restitution, followed by more delayed mechanisms of epithelial wound healing including increased epithelial cell proliferation and epithelial cell differentiation. Restitution of the intestinal surface epithelium is modulated by a range of highly divergent factors among them a broad spectrum of structurally distinct regulatory peptides, variously described as growth factors or cytokines. Several regulatory peptide factors act from the basolateral site of the epithelial surface and enhance epithelial cell restitution through TGF-β-dependent pathways. In contrast, members of the trefoil factor family (TFF peptides) appear to stimulate epithelial restitution in conjunction with mucin glycoproteins through a TGF-β-independent mechanism from the apical site of the intestinal epithelium. In addition, a number of other peptide molecules like extracellular matrix factors and blood clotting factors and also non-peptide molecules including phospholipids, short-chain fatty acids (SCFA), adenine nucleotides, trace elements and pharmacological agents modulate intestinal epithelial repair mechanisms. Repeated damage and injury of the intestinal surface are key features of various intestinal disorders including inflammatory bowel diseases and require constant repair of the epithelium. Enhancement of intestinal repair mechanisms by regulatory peptides or other modulatory factors may provide future approaches for the treatment of diseases that are characterized by injuries of the epithelial surface.
PMCID: PMC2679124  PMID: 18200658
Intestines; Wound healing; Inflammation; Restitution
21.  Th17 Immunity in Children with Allergic Asthma and Rhinitis: A Pharmacological Approach 
PLoS ONE  2013;8(4):e58892.
Th17 cells and IL-17A play a role in the development and progression of allergic diseases. We analyzed the IL-17A levels in sputum supernatants (Ss), nasal wash (NW) and plasma (P) from Healthy Controls (HC) and children with Asthma/Rhinitis. We tested the expression of IL-17A, RORγ(t) and FOXP3 in peripheral blood T-lymphocytes from intermittent and mild-moderate asthma. The effect of Budesonide and Formoterol was tested “in vitro” on IL-17A, RORγ(t) and FOXP3 expression in cultured T-lymphocytes from mild-moderate asthma/persistent rhinitis patients, and on nasal and bronchial epithelial cells stimulated with NW and Ss from mild-moderate asthma/persistent rhinitis. Further, the effect of 12 weeks of treatment with Budesonide and Formoterol was tested “in vivo” in T-lymphocytes from mild-moderate asthma/persistent rhinitis patients. IL-17A was increased in Ss, NW and P from children with mild-moderate asthma compared with intermittent and HC. In cultured T-lymphocytes IL-17A and RORγ(t) expression were higher in mild-moderate asthma/persistent rhinitis than in mild-moderate asthma/intermittent rhinitis, while FOXP3 was reduced. Budesonide with Formoterol reduced IL-17A and RORγ(t), while increased FOXP3 in cultured T-lymphocytes from mild-moderate asthma/persistent rhinitis, and reduced the IL-8 release mediated by IL-17A present in NW and Ss from mild-moderate asthma/persistent rhinitis in nasal and bronchial epithelial cells. Finally, Budesonide with Formoterol reduced IL-17A levels in P and Ss, CD4+IL-17A+T-cells, in naïve children with mild-moderate asthma/persistent rhinitis after 12 weeks of treatment. Th17 mediated immunity may be involved in the airway disease of children with allergic asthma and allergic rhinitis. Budesonide with Formoterol might be a useful tool for its therapeutic control.
PMCID: PMC3616002  PMID: 23573194
22.  Reparative Capacity of Airway Epithelium Impacts Deposition and Remodeling of Extracellular Matrix 
Defective epithelial repair in the setting of chronic lung disease has been suggested to contribute to uncontrolled extracellular matrix (ECM) deposition and development of fibrosis. We sought to directly test this hypothesis through gene expression profiling of total lung RNA isolated from mouse models of selective epithelial cell injury that are associated with either productive or abortive repair. Analysis of gene expression in repairing lungs of naphthalene-exposed mice revealed prominent clusters of up-regulated genes with putative roles in regulation of the extracellular matrix and cellular proliferation. Further analysis of tenascin C (Tnc), a representative matrix protein, in total lung RNA revealed a transient 4.5-fold increase in mRNA abundance 1 day after injury and a return to steady-state levels by Recovery Day 3. Tnc was deposited by the peribronchiolar mesenchyme immediately after injury and was remodeled to basement membrane subtending the bronchiolar epithelium during epithelial repair. Epithelial restitution was accompanied by a decrease in Tnc mRNA and protein expression to steady-state levels. In contrast, abortive repair using a transgenic model allowing ablation of all reparative cells led to a progressive increase in Tnc mRNA within lung tissue and accumulation of its gene product within the subepithelial mesenchyme of both conducting airways and alveoli. These data demonstrate that the ECM is dynamically remodeled in response to selective epithelial cell injury and that this process is activated without resolution in the setting of defective airway epithelial repair.
PMCID: PMC2689915  PMID: 18978301
airway epithelium; repair; Clara cell; extracellular matrix; fibrosis
23.  Lipopolysaccharide Binding Protein Enables Intestinal Epithelial Restitution Despite Lipopolysaccharide Exposure 
Intestinal epithelial restitution is the first part in the process of mucosal repair after injury in the intestine. Integrity of the intestinal mucosal barrier is important as a first line of defense against bacteria and endotoxin. Necrotizing enterocolitis (NEC) is a major cause of morbidity and mortality in extremely low birth weight infants, but its mechanisms are not well defined. Abnormal bacterial colonization, immature barrier function, innate immunity activation and inflammation likely play a role. Lipopolysaccharide (LPS) binding protein (LBP) is secreted by enterocytes in response to inflammatory stimuli and has concentration-dependent effects. At basal concentrations, LBP stimulates the inflammatory response by presenting LPS to its receptor. However, at high concentrations, LBP is able to neutralize LPS and prevent an exaggerated inflammatory response. We sought to determine how LBP would affect wound healing in an in vitro model of intestinal cell restitution and protect against intestinal injury in a rodent model of NEC. Immature intestinal epithelial cells (IEC-6) were seeded in poly-l-lysine coated 8 chamber slides and grown to confluence. A 500μm wound was created using a cell scraper mounted on the microscope to achieve uniform wounding. Media was replaced with media containing LPS +/− LBP. Slide wells were imaged after 0, 8, and 24 hours and then fixed. Cellular restitution was evaluated via digital images captured on an inverted microscope and wound closure was determined by automated analysis. TLR4 was determined by rtPCR after RNA isolation from wounded cells 24 hours after treatment. LPS alone attenuated wound healing in immature intestinal epithelium. This attenuation is reversed by 24 hours with increasing concentrations of LBP so that wound healing is equivalent to control (p< 0.001). TLR4 was increased with LPS alone but levels returned to that of control after addition of LBP in the higher concentrations. LBP had no effect on the development of intestinal injury when given during our rodent model of NEC. Abnormal bacterial colonization and activation of innate immunity by LPS are likely involved in the pathogenesis of NEC. The attentuation of wound healing was reversed when LBP was added to LPS but only in the higher concentrations. At these same concentrations of LBP, TLR4 was decreased to that of control. These results indicate that LBP may be a novel therapeutic strategy to facilitate wound healing after the acute phase of NEC and other forms of intestinal injury.
PMCID: PMC3288261  PMID: 22002480
These studies have shown that the bones of guinea pigs given daily injections of parathormone from the age of 2 to 7 days to the age of 110 to 120 days, show relatively very little effect after receiving 20 units daily during the last 65 to 87 days of treatment. But it is probable that their bones underwent decalcification early in the treatment and that subsequently the parathormone, continued at the same dosage, did not maintain the effects on the bones. Healing finally occurred despite it. The bones of guinea pigs treated with intermittent injections of large doses of parathormone from the time they were 1 week old to the age of 95 to 145 days also showed relatively few changes at the end of the treatment. The injections were given at intervals of 7 to 11 days, and were stepped up from 60 units to 140 units. From our previous experience (1) we infer that the earlier injections of parathormone produced very extensive bone changes which healed in the intervals between the injections. As the guinea pigs became older the injections of parathormone did not produce as severe effects. We have found in our studies of experimental hyperparathyroidism that the bone changes after a single large dose of parathormone in young guinea pigs are soon healed. The study of a series of animals shows that healing begins at about the 48th hour after injection, and proceeds rapidly. Between the 8th and 14 days, callus may be observed at the costochondral junctions, where fractures had occurred. Now the endosteum may be lined by osteoblasts and the vessel canals by new formed bone. In adult guinea pigs extremely large single doses had little effect on the bones in 48 hours, even though the dose killed the animal. It was only when three doses pyramided over a period of 48 hours and totaling 2580 units of parathormone were given, that moderately severe bone resorption could be demonstrated in the adult. The elevation of serum calcium may be considered as one of the indices of calcium mobilization in experimental hyperparathyroidism. When the rate of calcium excretion exceeds the rate of its mobilization, or when the animal is on a low calcium diet, hypercalcemia may be absent. It is possible to raise the serum calcium of adult guinea pigs by large single doses of parathormone, but the resulting rise is not as great as in the young (2). This is confirmatory evidence of the fact that calcium is mobilized much less rapidly from the bones of old animals than from those of young ones. Collip pointed out that young normal dogs are more susceptible to parathormone (6). This observation was corroborated by Morgan and Garrison (7). We found that the same difference held also in experimental hyperparathyroidism produced in dogs by repeated doses of parathormone (8). In man, clinical experience likewise indicates the necessity of using relatively large doses of parathormone to raise the serum calcium of adults. The serum calcium of middle-aged or old adults does not rise significantly unless as much as 100 units or more of parathormone are given daily for a number of days. Charts VI and VII, in a recent paper by Merritt and Bauer (9), support our findings of the relative difficulty of obtaining a significant elevation of serum calcium in adults. If adult guinea pigs are given daily injections of parathormone which are rapidly stepped up, the animals may be killed by the ensuing acute hyperparathyroidism, only slight bone changes being produced. However, a careful avoidance of the induction of acute hyperparathyroidism by gradual stepping up of the parathormone dose permits the employment of doses continued over a long period of time that could not possibly have been tolerated otherwise. Furthermore, healing of the lesions thus produced may occur, in spite of the continuance of parathormone at this level. It seems likely that the difference in response of young and old guinea pigs to single doses of parathormone, as indicated by the bone changes, as well as by the serum calcium and phosphorus, is related to the more rapid rate of mineral metabolism in the young, actively growing animals. The calcium mobilizing effect of parathormone is most prominent in actively growing young animals, the calcium being withdrawn from the most readily available stores—the regions of most active new bone formation and most active bone reconstruction (10). In the adult animal the calcium reserves (in the formed bone) are less susceptible to the calcium mobilizing effect of parathormone. The adult guinea pig will show relatively slight bone changes even as a result of extremely large, fatal doses of parathormone. Repeated doses, as is well known, will produce, by pyramiding, greater effects than the entire amount administered at one time. In this type of experiment the young again show greater susceptibility of the bone than the adult. In time, however, some compensation takes place, and the effects of the same doses are decreased until finally healing may occur in spite of the continued treatment. Increase of the dose, however, again elicits the parathormone effects upon the bone, as well as upon the serum calcium and phosphorus, without toxic changes (1, 8). It would seem that some compensation sets in which may be overcome by increasing the dose. This compensation is especially evident in the experiments in which the parathormone doses were stepped up gradually from small amounts. In addition to the compensation observed in young and adult animals as a result of repeated injections of parathormone, we must also consider the possibility that there is a compensating mechanism in adult animals more effective than in the young. That compensation occurs is unquestionable but its nature is not clear. Apparently it is less effective during pregnancy, doses of parathormone which produce only slight bone changes in ordinary adults causing very severe lesions in advanced pregnancy (11). Parathormone has been shown to produce only one primary effect on bone, and that is decalcification. This may come about as the result of a change in the circulating tissue fluids, the salts being dissolved out of the organic matrix, and the latter disappearing secondarily. The process is most rapid in the vicinity of most active bone formation. The osteoblasts disappear from the surfaces of bone where dissolution is occurring, and at the same time the marrow connective tissue proliferates. Fusion of cells produces osteoclasts (12), which then proceed to remove the decalcified organic matrix, with the production of the deep lacunae of Howship. Frequently leucocytes are also observed actively phagocyting the decalcified organic matrix, and often leucocytes are observed within the osteoclasts (12). Healing is associated with the complete reversal of the process. The osteoclasts disappear, the connective tissue diminishes, osteoblasts reappear, and bone formation is resumed. As we have previously stated (13), parathormone produces a more continuous effect than experimental acidosis and greater changes than are seen in experimental osteoporosis. A pronounced decalcification results from it which, with its sequelae, simulates von Recklinghausen's disease. The emphasis which the older pathologists laid on osteoclasts as a special feature of ostitis fibrosa cystica is justified, for in the experimental condition the appearance of great numbers of osteoclasts is a constant feature, whenever decalcification occurs (13). There seems to be no doubt that the giant cell tumors found in ostitis fibrosa cystica are expressions of the same pathological response. The other features of the bone changes of hyperparathyroidism—marrow hemorrhage, cysts, fractures, and osteoid proliferation—are secondary to the primary decalcification. Progress of the pathological changes leads to circulatory stasis and cyst formation. Stresses and strains exerted on the progressively weakening bone may result in microscopical or gross fractures. Osteoid tissue is, as we have previously pointed out (13), merely reparative in nature, being laid down as support to the weakened or fractured bone, or as a part of healing. Osteoid borders appear on bone surfaces 48 hours after one large dose of parathormone. The mosaic picture which we have observed in the bones of some of our animals is produced by short and irregularly disposed cement lines resulting from rapid bone transformation. Schmorl (14) recently emphasized the mosaic-like appearance of the newly formed lamellar bone in Paget's disease (ostitis fibrosa deformans). The mosaic-like appearance of bone has also been described in local bone conditions, as e.g. syphilitic periostitis, and in bone in the vicinity of cysts and giant cell tumors in von Recklinghausen's disease (ostitis fibrosa cystica). However, Schmorl claims that in no disease is the mosaic appearance so constant and the arrangement of the cement lines so irregular as in Paget's disease. In chronic experimental hyperparathyroidism (von Recklinghausen's disease), the mosaic structure is not a prominent feature because of the progressive decalcification. But the bones of our young guinea pigs which received intermittent injections showed a mosaic-like appearance indicative of the periodic decalcifications and restorations which they had undergone.
PMCID: PMC2132070  PMID: 19869973
25.  A Reconstituted Telomerase-Immortalized Human Corneal Epithelium In Vivo: A Pilot Study 
Current eye research  2011;36(8):706-712.
Telomerase-immortalized human corneal epithelial cells have been reported to stratify and differentiate in vitro similar to native tissue. The purpose of this study was to assess the ability of a telomerase-immortalized human corneal epithelial cell line to generate a full thickness epithelium in vivo in athymic mice.
Telomerized corneal epithelial cells were transduced with a retroviral vector encoding the herpes simplex thymidine kinase gene. Efficacy of the thymidine kinase suicide gene was confirmed using a live/dead assay. The epithelium was mechanically removed from athymic nude mice and remaining cells were treated with mitomycin C to prevent re-epithelialization. Telomerized corneal epithelial cells were seeded onto the denuded cornea and allowed to adhere for 4 and 24 hours. Cellular attachment was assessed using a fluorescent cell tracker. Stratification and differentiation were assessed after 7 days using phalloidin and a mouse monoclonal antibody to K3
Telomerized corneal epithelial cells were visualized across the denuded stromal surface at 4 and 24 hours, with multi-layering evident at the latter time point. No epithelium was present in the non-treated eye. 7 days post-transplantation cells stratified into a multilayered epithelium, with positive K3 expression in basal and suprabasal cells. Treatment with ganciclovir induced significant loss of viability in vitro.
The findings in this pilot study demonstrate that telomerized corneal epithelial cells possess the capacity to reconstitute a stratified corneal epithelium in vivo. The introduction of thymidine kinase allowed for the successful induction of cell death in proliferating cells in vitro. Collectively, these data suggest that a telomerase-immortalized corneal epithelial cell line transduced with thymidine kinase represents a potential model for studying differentiation and epithelial-niche interactions in vivo with potential applications in tissue engineering.
PMCID: PMC3149847  PMID: 21780919
cornea; epithelium; telomerase; differentiation; limbal niche

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