This Round Table will host an open discussion about NIH support for shared resource facilities. NIH recently implemented a reorganization plan that eliminated the National Center for Research Resources (NCRR). Programs formerly administered by NCRR have been reassigned to other NIH Institutes and Centers. The Shared Instrumentation Grant (SIG) and High End Instrumentation (HEI) programs are now part of the NIH Office of the Director in DPCPSI, directed by James M. Anderson, MD, PhD. Dr. Anderson will present an overview of the role of his division and of NIH in supporting shared resource facilities. Before joining NIH, Dr. Anderson was Chair of the Department of Cell and Molecular Physiology in the School of Medicine of the University of North Carolina at Chapel Hill. He was responsible for the operation and management of a number of research core labs at UNC. He is a new voice of support for shared resource facilities that support NIH research. Abraham Levy, PhD, is the newly appointed Program Director responsible for the SIG and HEI programs. Dr. Levy worked for Dr. Marjorie Tingle in the NCRR SIG office for many years. He is highly qualified to be the new director of these important programs. Dr. Levy will discuss how SIG and HEI will be administered in their new home in DPCPSI. Time will be allowed for questions and discussion following the presentations of Drs. Anderson and Levy.
BACKGROUND AND OBJECTIVE:
Many thousands of patients die every year in the United States as a result of serious and largely preventable safety events or medical errors. Safety events are common in hospitalized children. We conducted a quality improvement initiative to implement cultural and system changes with the goal of reducing serious safety events (SSEs) by 80% within 4 years at our large, urban pediatric hospital.
A multidisciplinary SSE reduction team reviewed the safety literature, examined recent SSEs, interviewed internal leaders, and visited other leading organizations. Senior hospital leaders provided oversight, monitored progress, and helped to overcome barriers. Interventions focused on: (1) error prevention; (2) restructuring patient safety governance; (3) a new root cause analysis process and a common cause database; (4) a highly visible lessons learned program; and (5) specific tactical interventions for high-risk areas. Our outcome measures were the rate of SSEs and the change in patient safety culture.
SSEs per 10 000 adjusted patient-days decreased from a mean of 0.9 at baseline to 0.3 (P < .0001). The days between SSEs increased from a mean of 19.4 at baseline to 55.2 (P < .0001). After a worsening of patient safety culture outcomes in the first year of intervention, significant improvements were observed between 2007 and 2009.
Our multifaceted approach was associated with a significant and sustained reduction of SSEs and improvements in patient safety culture. Multisite studies are needed to better understand contextual factors and the significance of specific interventions.
patient safety; quality improvement; safety culture
Novel self-assembled monolayers (SAMs) designed to present homogenous surface chemistries were utilized to further investigate the material surface chemistry dependent macrophage and foreign body giant cell (FBGC) behaviors including macrophage adhesion, fusion, and apoptosis. Contact angle analysis revealed instabilities in the –CH3 and –COOH terminate SAM surfaces upon incubation in serum-free media at 37oC or under dry, room temperatureconditions. Further analysis indicated that the –CH3 terminated SAM surface degraded rapidly within 2 hours and loss of sufficient SAM units to be comparable to the gold (Au) control surface within 24 hours of incubation in serum-free media (SFM) at 37oC. After 5days of incubation in SFM at 37oC, the contact angles for the –COOH terminated SAMsurfaces increased markedly. AFM analysis confirmed the desorption of –CH3 terminated SAM molecules from the surface with increased roughness and marked appearance of peaks andvalleys within 2 hours. A decrease in the thickness of the –COOH terminated SAM surface also suggests molecular desorption over time. No significant changes in contact angle or AFM analyses were observed on the –OH terminated SAM surfaces. Cellular adhesion decreased morerapidly on the Au control and –CH3 terminated SAM surfaces in comparison to the other surfaces. However by day 10, cellular adhesion, fusion, and apoptosis were comparable on all SAM surfaces and the Au control . These studies suggest that SAM surfaces may not be suitable for long-term studies where material dependent properties are investigated.
self-assembled monolayers; instability; macrophage; foreign body giant cell; contact angles
Macrophages are phagocytic cells with great importance in guiding multiple stages of inflammation and tissue repair. By producing a large number of biologically active molecules, they can affect the behavior of other cells and events, such as the foreign body response and angiogenesis. Since protein adsorption to biomaterials is crucial for the inflammatory process, we addressed the ability of the pro-inflammatory molecule fibrinogen (Fg) to modulate macrophage behavior toward tissue repair/regeneration. For this purpose, we used chitosan (Ch) as a substrate for Fg adsorption. Freshly isolated human monocytes were seeded on Ch substrates alone or previously adsorbed with Fg, and allowed to differentiate into macrophages for 10 days. Cell adhesion and morphology, formation of foreign body giant cells (FBGC), and secretion of a total of 80 cytokines and growth factors were evaluated. Both substrates showed similar numbers of adherent macrophages along differentiation as compared with RGD-coated surfaces, which were used as positive controls. Fg did not potentiate FBGC formation. In addition, actin cytoskeleton staining revealed the presence of punctuate F-actin with more elongated and interconnecting cells on Ch substrates. Antibody array screening and quantification of inflammation- and wound-healing-related factors indicated an overall reduction in Ch-based substrates versus RGD-coated surfaces. At late times, most inflammatory agents were down-regulated in the presence of Fg, in contrast to growth factor production, which was stimulated by Fg. Importantly, on Ch+Fg substrates, fully differentiated macrophages produced significant amounts of macrophage inflammatory protein-1delta (MIP-1δ), platelet-derived growth factor-BB, bone morphogenetic protein (BMP)-5, and BMP-7 compared with Ch alone. In addition, other important factors involved in bone homeostasis and wound healing, such as growth hormone, transforming growth factor-β3, and insulin-like growth factor-binding proteins, as well as several angiogenic mediators, including endocrine gland-derived vascular endothelial factor, fibroblast growth factor-7, and placental growth factor, were significantly promoted by Fg. This work provides a new perspective on the inflammatory response in the context of bone repair/regeneration mediated by a pro-inflammatory protein (Fg) adsorbed onto a biomaterial (Ch) that does not otherwise exhibit osteogenic properties.
The role of lymphocytes in the biological response to synthetic polymers is poorly understood despite the transient appearance of lymphocytes at the biomaterial implant site. To investigate cytokines, chemokines, and extracellular matrix (ECM) proteins produced by lymphocytes and macrophages in response to biomaterial surfaces, human peripheral blood monocytes and lymphocytes were co-cultured on polyethylene terephthalate (PET)-based material surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic chemistries. Antibody array screening showed the majority of detected proteins are inflammatory mediators that guide the early inflammatory phases of wound healing. Proteomic ELISA quantification and adherent cell analysis were performed after 3, 7, and 10 days of culture. IL-2 and IFN-γ were not detected in any co-cultures suggesting lack of lymphocyte activation. The hydrophilic/neutral surfaces increased IL-8 relative to the hydrophobic PET surface (p<0.05). The hydrophilic/anionic surfaces promoted increased TNF-α over hydrophobic and cationic surfaces and increased MIP-1β compared to hydrophobic surfaces (p<0.05). Since enhanced macrophage fusion was observed on hydrophilic/anionic surfaces, the production of these cytokines likely plays an important role in the fusion process. The hydrophilic/cationic surface promoted IL-10 production and increased matrix metalloproteinase (MMP)-9/tissue inhibitor of MMP (TIMP) relative to hydrophilic/neutral and anionic surfaces (p<0.05). These results suggest hydrophilic/neutral and anionic surfaces promote pro-inflammatory responses and reduced degradation of the ECM, whereas the hydrophilic/cationic surfaces induce an anti-inflammatory response and greater MMP-9/TIMP with an enhanced potential for ECM breakdown. The study also underscores the usefulness of protein arrays in assessing the role of soluble mediators in the inflammatory response to biomaterials.
PET biomaterials; lymphocytes; macrophages; cytokines; matrix metalloproteinases
The role/s of T lymphocytes in the foreign body response has not been thoroughly elucidated. Lymphocytes are known to augment macrophage adhesion and fusion in vitro. Furthermore T lymphocytes are a possible source of the cytokines, IL-4 and IL-13 which induce macrophage fusion. In this study we used BALB/c mice and BALB/c (nu/nu) nude mice to investgate foreign body giant cell (FBGC) formation in a T cell deficient setting. Mice were implanted with Elasthane 80A (PEU), silicone rubber (SR) or poly(ethylene terephthalate) (PET) for 7, 14, or 21 days using the cage implant system. Exudate cells and IL-4 and IL-13 levels in exudate supernatants were analyzed by flow cytometry and a multiplex immunoassay, respectively, at days 7, 14, and 21. Macrophage adhesion and fusion on material surfaces were analyzed using optical microscopy. T cell deficient mice had lower total leukocyte concentrations at the biomaterial implant site at all time points. Adherent cell density was comparable between normal and T cell deficient mice except in the PEU group at day 21. However, percent fusion, average nuclei per FBGC, and FBGC morphology was comparable between normal and T cell deficient mice. IL-4 was not detected in any samples, but IL-13 levels were also comparable between normal and T cell deficient mice indicating Th2 polarized T cells are not the sole source of this cytokine. We have shown that there are pathways that do not require thymus-matured T lymphocytes which lead to a normal foreign body response to biomaterials in a murine model.
foreign body response; IL-4; IL-13; T lymphocyte; biomaterials
Lymphocytes have been shown to be involved in modulating monocyte and macrophage behavior in the foreign body reaction. Lymphocyte effects on biomaterial-adherent macrophage and foreign body giant cell (FBGC) behavior were further investigated by culturing monocytes alone or together with lymphocytes, either in direct co-cultures or indirectly in transwells, on a series of polyethylene terephthalate (PET)-based photograft co-polymerized material surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic chemistries. After periods of 3, 7, and 10 days, cytokine production was quantified by ELISA and normalized to adherent macrophage/FBGC density to yield a measure of adherent macrophage/FBGC activation. Interactions with lymphocytes enhanced adherent macrophage and FBGC production of pro-inflammatory IL-1β, TNF-α, IL-6, IL-8, and MIP-1β on the hydrophobic and hydrophilic/cationic surfaces but had no effect on anti-inflammatory IL-10 production indicating lymphocytes promote a pro-inflammatory response to biomaterials. Lymphocytes also did not significantly influence MMP-9, TIMP-1, and TIMP-2 production. Interactions through indirect (paracrine) signaling showed a significant effect in enhancing adherent macrophage/FBGC activation at early time points while interactions via direct (juxtacrine) mechanisms dominated at later time points. Biomaterial surface chemistries differentially affected the observed responses as hydrophilic/neutral and hydrophilic/anionic surfaces evoked the highest levels of activation relative to the other surfaces but did not facilitate lymphocyte enhancement of adherent macrophage/FBGC activation.
biomaterials; foreign body reaction; lymphocytes; macrophages; activation
In order to further elucidate the foreign body reaction, investigation of cytokines at biomaterial implant sites was carried out using a multiplex immunoassay and ELISA. Macrophage activation cytokines (IL-1β, IL-6, TNFα), cytokines important for macrophage fusion (IL-4, IL-13), anti-inflammatory cytokines (IL-10, TGFβ), chemokines (GRO/KC, MCP-1), and the T cell activation cytokine IL-2 were quantified at biomaterial implant sites. Empty cages (controls) or cages containing synthetic biomedical polymer (Elasthane 80A (PEU), Silicone rubber (SR), or polyethylene terephthalate (PET)) were implanted subcutaneously in Sprague Dawley rats for 4, 7, or 14 days, and cytokines in exudate supernatants and macrophage surface adhesion and fusion were quantified. The presence of a polymer implant did not affect the levels of IL-1β, TGFβ, and MCP-1 in comparison to the control group. IL-2 was not detected in virtually any of the samples. Although the levels of IL-4, IL-13, IL-10, and GRO/KC were affected by polymer implantation, but not dependent on a specific polymer, IL-6 and TNFα were significantly greater in those animals implanted with PEU and SR, materials that do not promote fusion. The results indicate differential material dependent cytokine profiles are produced by surface adherent macrophages and foreign body giant cells in vivo.
cage implant system; multiplex immunoassay; cytokines; synthetic biomaterials
An in vitro system of interleukin (IL)-4-induced foreign body giant cell (FBGC) formation was utilized to define the adhesion protein substrate(s) that promotes this aspect of the foreign body reaction on biomedical polymers. Human monocytes were cultured on cell culture polystyrene surfaces that had been pre-adsorbed with a synthetic arginine-glycine-aspartate (RGD) peptide previously found to support optimal FBGC formation, or with various concentrations of potential physiological protein substrates, i.e. complement C3bi, collagen types I or IV, fibrinogen, plasma fibronectin, fibroblast fibronectin, laminin, thrombospondin, vitronectin, or von Willebrand factor. Cultures were evaluated on days 0 (1.5 hr), 3, and 7 by May-Grünwald/Giemsa staining. Initial monocyte adhesion occurred on all adsorbed proteins. However, by day 7 of culture, only vitronectin was striking in its ability to support significant macrophage adhesion, development, and fusion leading to FBGC formation. Vitronectin supported high degrees of FBGC formation at an absorption concentration between 5 and 25 μg per ml. These findings suggest that adsorbed vitronectin is critical in the collective events that support and promote FBGC formation on biomedical polymers, and that the propensity for vitronectin adsorption may underlie the material surface chemistry dependency of FBGC formation.
adhesion; integrins; monocyte; macrophage fusion; biomedical polymers
Tiger sharks (Galecerdo cuvier) are apex predators characterized by their broad diet, large size and rapid growth. Tiger shark maximum size is typically between 380 & 450 cm Total Length (TL), with a few individuals reaching 550 cm TL, but the maximum size of tiger sharks in Hawaii waters remains uncertain. A previous study suggested tiger sharks grow rather slowly in Hawaii compared to other regions, but this may have been an artifact of the method used to estimate growth (unvalidated vertebral ring counts) compounded by small sample size and narrow size range. Since 1993, the University of Hawaii has conducted a research program aimed at elucidating tiger shark biology, and to date 420 tiger sharks have been tagged and 50 recaptured. All recaptures were from Hawaii except a single shark recaptured off Isla Jacques Cousteau (24°13′17″N 109°52′14″W), in the southern Gulf of California (minimum distance between tag and recapture sites = approximately 5,000 km), after 366 days at liberty (DAL). We used these empirical mark-recapture data to estimate growth rates and maximum size for tiger sharks in Hawaii. We found that tiger sharks in Hawaii grow twice as fast as previously thought, on average reaching 340 cm TL by age 5, and attaining a maximum size of 403 cm TL. Our model indicates the fastest growing individuals attain 400 cm TL by age 5, and the largest reach a maximum size of 444 cm TL. The largest shark captured during our study was 464 cm TL but individuals >450 cm TL were extremely rare (0.005% of sharks captured). We conclude that tiger shark growth rates and maximum sizes in Hawaii are generally consistent with those in other regions, and hypothesize that a broad diet may help them to achieve this rapid growth by maximizing prey consumption rates.
The foreign body reaction often interferes with the long-term functionality and performance of implanted biomedical devices through fibrous capsule formation. While many implant modification techniques have been adopted in attempts to control fibrous encapsulation, the outcomes remained sub-optimal. Nanofiber scaffold-mediated RNA interference may serve as an alternative approach through the localized and sustained delivery of siRNA at implant sites. In this study, we investigated the efficacy of siRNA-PCLEEP (poly(caprolactone-co-ethylethylene phosphate) nanofibers in controlling fibrous capsule formation through the down-regulation of Collagen type I (COL1A1) in vitro and in vivo. By encapsulating complexes of COL1A1 siRNA with a transfection reagent (Transit TKO) or cell penetrating peptides (CPPs), CADY or MPG, within the nanofibers (550–650 nm in diameter), a sustained release of siRNA was obtained for at least 28 days (loading efficiency ~ 60–67%). Scaffold-mediated transfection significantly enhanced cellular uptake of oligonucleotides and prolonged in vitro gene silencing duration by at least 2–3 times as compared to conventional bolus delivery of siRNA (14 days vs 5–7 days by bolus delivery). In vivo subcutaneous implantation of siRNA scaffolds revealed a significant decrease in fibrous capsule thickness at weeks 2 and 4 as compared to plain nanofibers (p < 0.05). Taken together, the results demonstrated the efficacy of scaffold-mediated siRNA gene-silencing in providing effective long-term control of fibrous capsule formation.
RNA interference; Gene knockdown; Scaffold-mediated transfection; Cell penetrating peptides; Electrospinning
Previous in vitro studies in our laboratory have shown that lymphocytes can influence macrophage adhesion and fusion on biomaterial surfaces. However, few studies have evaluated how material adherent macrophages can influence lymphocyte behavior, specifically T cells. In this study, we cultured human peripheral blood mononuclear cells from healthy donors on three synthetic non-biodegradable biomedical polymers: Elasthane 80A (PEU), Silicone rubber (SR), or polyethylene terephthalate (PET) and tissue culture polystyrene (TCPS). Upregulation of T cell surface activation markers (CD69 and CD25), lymphocyte proliferation, and interleukin-2 (IL-2) and interferon-γ (IFNγ) concentrations were evaluated by flow cytometry, carboxy-fluorescein diacetate, succinimydyl ester (CFSE) incorporation, and multiplex cytokine immunoassay, respectively, to assess T cell activation. Following 3 and 7 days of culture, CD4+ helper T cells from cultures of any of the material groups did not express the activation markers CD69 and CD25 and lymphocyte proliferation was not present. IL-2 and IFNγ levels were produced, but dependent on donor. These data indicate that T cells are not activated in response to clinically relevant synthetic biomaterials. The data also suggest that lymphocyte subsets exclusive of T cells are the source of the lymphokines, IL-2 and IFN-γ, in certain donors.
Lymphocyte activation; biomaterials; interferonγ; Interleukin-2
To characterize the effects of adherent macrophages and biomaterial surface chemistries on lymphocyte adhesion and activation, lymphocytes were co-cultured with monocytes alone and together, directly and separated by a porous membrane transwell on hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic biomaterial surfaces. Surface adherent cells were quantitatively analyzed after 3 days utilizing immunofluorescence and phase contrast imaging. After periods of 3, 7, and 10 days, secreted interferon-γ (IFN-γ) was quantified by ELISA. Limited direct biomaterial-adherent lymphocytes were identified regardless of the presence of macrophages or foreign body giant cells (FBGC). The majority of adherent lymphocytes, which were T cells (> 95%) rather than natural killer cells, predominantly interacted with adherent macrophages and FBGCs; greater than 90% were interacting on surfaces with higher levels of adherent macrophages and FBGCs and greater than 55% were interacting on surfaces with lower levels of macrophages and FBGCs. The hydrophilic/anionic surface promoted higher levels of macrophage- and FBGC-adherent lymphocytes but was nonselective for lymphocyte subtype interactions. The hydrophilic/neutral surface was selective for CD4+ T lymphocyte interactions while the hydrophobic surface was selective for CD8+ T lymphocyte interactions. IFN-γ was produced in direct and indirect co-cultures but not in lymphocyte- and monocyte-only cultures suggesting that lymphocytes are activated via macrophage-derived cytokines rather than direct biomaterial contact. Direct lymphocyte interactions with adherent macrophages/FBGCs enhanced IFN-γ production relative to indirect co-cultures. These results suggest that lymphocytes prefer interactions with adherent macrophages and FBGCs, resulting in lymphocyte activation, and these interactions can be influenced by biomaterial surface chemistries.
biomaterials; lymphocyte activation; adhesion; macrophages and foreign body giant cells; cytokines
The integrity of the tight junction barrier in epithelial and endothelial cells is critical to human health, but we still lack a detailed mechanistic knowledge of how the barrier is formed during development or responds to pathological and pharmacological insults. This limits our understanding of barrier dysfunction in disease and slows the development of therapeutic strategies. Recent studies confirm the long-maintained but previously unsupported view that the zonula occludens (ZO) proteins ZO-1 and ZO-2 are critical determinants of barrier formation. However, ZO proteins can also be components of adherens junctions, and recent studies suggest that ZO proteins may also promote the assembly and function of these junctions during epithelial morphogenesis. We review these studies and outline several recent observations that suggest that one role of ZO proteins is to regulate cytoskeletal dynamics at cell junctions. Finally, we propose a model by which the functional activities of ZO proteins in the adherens junction and tight junction are differentiated by a novel regulatory motif known as the U6 or acidic motif.
tight junction; adherens junction; zonula occludens; ZO-1; ZO-2; E-cadherin; cytoskeleton; MAGUK; PDZ; scaffold; permeability; epithelia; morphogenesis
This study reports on the use of a fibrinogen-derived peptide for the specific targeting and delivery of vancomycin to Staphylococcus epidermidis biofilms. One method by which S. epidermidis initially adheres to biomaterials uses the plasma protein fibrinogen as an intermediary, where the S. epidermidis surface protein SdrG binds to a short amino acid sequence near the amino terminus of the Bβ chain of fibrinogen. We mimicked this binding interaction and demonstrated the use of a synthetic fibrinogen-based β6-20 peptide to target and deliver vancomycin to S. epidermidis in vitro. The β6-20 peptide was synthesized and labeled with a nanogold probe, and its targeting capabilities were examined through the use of scanning electron microscopy. The Nanogold component was then replaced by vancomycin, utilizing a flexible, variable length poly(ethylene glycol) linker between the peptide and antibiotic to create the targeted vancomycin products, β6-20-PEGx-VAN. Initial binding to surface adherent S. epidermidis was increased in a concentration-dependent manner relative to vancomycin for all equivalent concentrations ≥4 μg/ml, with targeted vancomcyin content up to 22.9 times that of vancomycin alone. Retention of the targeted antibiotics was measured after an additional 24 hour incubation period, revealing levels 1.3 times that of vancomycin. The results demonstrate the improved targeting and retention of vancomycin within a biofilm due to the incorporation of a specific targeting motif.
Staphylococcus epidermidis; SdrG; β6-20 peptide; Targeted Delivery; Vancomycin
The two compositionally distinct extracellular cochlear fluids, endolymph and perilymph, are separated by tight junctions that outline the scala media and reticular lamina. Mutations in TRIC (also known as MARVELD2), which encodes a tricellular tight junction protein known as tricellulin, lead to nonsyndromic hearing loss (DFNB49). We generated a knockin mouse that carries a mutation orthologous to the TRIC coding mutation linked to DFNB49 hearing loss in humans. Tricellulin was absent from the tricellular junctions in the inner ear epithelia of the mutant animals, which developed rapidly progressing hearing loss accompanied by loss of mechanosensory cochlear hair cells, while the endocochlear potential and paracellular permeability of a biotin-based tracer in the stria vascularis were unaltered. Freeze-fracture electron microscopy revealed disruption of the strands of intramembrane particles connecting bicellular and tricellular junctions in the inner ear epithelia of tricellulin-deficient mice. These ultrastructural changes may selectively affect the paracellular permeability of ions or small molecules, resulting in a toxic microenvironment for cochlear hair cells. Consistent with this hypothesis, hair cell loss was rescued in tricellulin-deficient mice when generation of normal endolymph was inhibited by a concomitant deletion of the transcription factor, Pou3f4. Finally, comprehensive phenotypic screening showed a broader pathological phenotype in the mutant mice, which highlights the non-redundant roles played by tricellulin.
This review is intended to provide insight into the current state of understanding regarding the molecular and cellular mechanisms underlying the formation and function of various types of multinucleated giant cells.
Recent studies involving mainly osteoclasts and foreign body giant cells have revealed a number of common factors, e.g., vitronectin, an adhesion protein, dendritic cell-specific transmembrane protein (DC-STAMP), a fusion factor, and macrophage fusion receptor (MFR), that contribute to giant cell formation and function. Insight into common molecules, receptors, and mediators of the adhesion and fusion mechanisms of giant cell formation have been complicated by the wide diversity of species, models, and cell types utilized in these studies.
These recently identified factors together with the well-known osteoclast receptor, αvβ3, may serve as potential therapeutic targets for the modulation and inhibition of multinucleated giant cell formation and function. Further studies on intracellular and intercellular signaling mechanisms modulating multinucleated giant cell formation and function are necessary for the identification of therapeutic targets as well as a better understanding of giant cell biology.
Multinucleated Giant Cell; Foreign Body Giant Cell; Macrophage; Osteoclast
The foreign body reaction composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial. A brief, focused overview of events leading to the foreign body reaction is presented. The major focus of this review is on factors that modulate the interaction of macrophages and foreign body giant cells on synthetic surfaces where the chemical, physical, and morphological characteristics of the synthetic surface are considered to play a role in modulating cellular events. These events in the foreign body reaction include protein adsorption, monocyte/macrophage adhesion, macrophage fusion to form foreign body giant cells, consequences of the foreign body response on biomaterials, and cross-talk between macrophages/foreign body giant cells and inflammatory/wound healing cells. Biomaterial surface properties play an important role in modulating the foreign body reaction in the first two to four weeks following implantation of a medical device, even though the foreign body reaction at the tissue/material interface is present for the in vivo lifetime of the medical device. An understanding of the foreign body reaction is important as the foreign body reaction may impact the biocompatibility (safety) of the medical device, prosthesis, or implanted biomaterial and may significantly impact short- and long-term tissue responses with tissue-engineered constructs containing proteins, cells, and other biological components for use in tissue engineering and regenerative medicine. Our perspective has been on the inflammatory and wound healing response to implanted materials, devices, and tissue-engineered constructs. The incorporation of biological components of allogeneic or xenogeneic origin as well as stem cells into tissue-engineered or regenerative approaches opens up a myriad of other challenges. An in depth understanding of how the immune system interacts with these cells and how biomaterials or tissue-engineered constructs influences these interactions may prove pivotal to the safety, biocompatibility, and function of the device or system under consideration.
Foreign body reaction; Macrophages; Foreign body giant cells; Biodegradation; Cytokines; Biomaterials
To better understand the relationship between macrophage/foreign body giant cell adhesion and activation on surface-modified biomaterials, quantitative assessment of adherent cell density (cells per mm²) and cytokine production (pgs per mL) were determined by ELISA. Further analysis to identify cellular activation was carried out by normalizing the cytokine concentration data to provide a measure of cellular activation. This method of analysis demonstrated that hydrophobic surfaces provided statistically significantly greater adherent cell densities than hydrophilic/neutral surfaces. However, when cell activation parameters were determined by normalization to the adherent cell density, the hydrophilic/neutral surfaces demonstrated statistically significantly greater levels of activation and production of IL-10, IL-1β, IL-6, IL-8, and MIP-1β. With increasing time, production of the anti-inflammatory cytokine IL-10 increased, whereas IL-1β, IL-6, and IL-8 decreased and MIP-1β was relatively constant over the culture time period. This observed dichotomy or disparity between adhesion and activation may be related to surface-induced adherent cell apoptosis. Further evaluation of macrophage activation on biomaterial surfaces indicated that an apparent phenotypic switch in macrophage phenotype occurred over the course of the in vitro culture. Analysis of cytokine/chemokine profiles with surface-modified biomaterials revealed similarities between the classically activated macrophages and the biomaterial-adherent macrophages early (day 3) in culture, while at later timepoints the biomaterial-adherent macrophages produced profiles similar to alternatively activated macrophages. Classically activated macrophages are those commonly activated by LPS (lipopolysaccharide) or IFN-γ (interferon-γ) and alternatively activated macrophages are those activated by IL-4/IL-13 or IL-10. Surface modification of biomaterials offers an opportunity to control cellular activation and cytokine profiles in the phenotypic switch, and may provide a means by which macrophages can be induced to regulate particular secretory proteins that direct inflammation, the foreign body reaction, wound healing, and ultimately biocompatibility.
macrophages; adhesion; activation; hydrophilic, hydrophobic, and ionic surface chemistry; foreign body reaction
Foreign body-type multinucleated giant cells (FBGC), formed by macrophage fusion, are a prominent cell type on implanted biomaterials, although the roles they play at these and other sites of chronic inflammation are not understood. Why lymphocytes are present in this scenario and the effects of fusing macrophages/FBGC on subsequent lymphocyte responses are also unclear. To address the physiological significance of FBGC in this regard, we employed our in vitro system of interleukin (IL)-4-induced human monocyte-derived macrophage fusion/FBGC formation. Initially, we pursued the identities of lymphocyte co-stimulatory molecules on fusing macrophages/FBGC. In addition, we further compared the FBGC phenotype to that currently associated with osteoclasts and dendritic cells using recognized markers. Immunoblotting of cell lysates and immunochemistry of macrophages/FBGC in situ, revealed that IL-4-induced macrophages/FBGC strongly express HLA-DR, CD98, B7-2 (CD86), and B7-H1 (PD-L1), but not B7-1 (CD80) or B7-H2 (B7RP-1). Furthermore, molecules currently recognized to be expressed on osteoclasts (calcitonin receptor, tartrate-resistant acid phosphatase, RANK) or dendritic cells (CD1a, CD40, CD83, CD95/fas) are undetectable. In contrast, fusing macrophages/FBGC strongly express the macrophage markers αX integrin (CD11c), CD68, and dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), whereas CD14 is completely down-modulated with IL-4-induced macrophage fusion. These novel data demonstrate that IL-4-induction of macrophage multinucleation/FBGC formation features the acquisition of a CD14-negative phenotypic profile which is distinguishable from that of dendritic cells and osteoclasts, yet potentially exhibits multiple capacities for lymphocyte interactions with resultant lymphocyte down-modulation.
Biocompatibility; chronic inflammation; lymphocyte; macrophage; multinucleated giant cell
ETOC: Our study reveals that ZO proteins in fully polarized cells regulate the assembly and contractility of the perijunctional actomyosin ring associated with the adherens junction.
The structure and function of both adherens (AJ) and tight (TJ) junctions are dependent on the cortical actin cytoskeleton. The zonula occludens (ZO)-1 and -2 proteins have context-dependent interactions with both junction types and bind directly to F-actin and other cytoskeletal proteins, suggesting ZO-1 and -2 might regulate cytoskeletal activity at cell junctions. To address this hypothesis, we generated stable Madin-Darby canine kidney cell lines depleted of both ZO-1 and -2. Both paracellular permeability and the localization of TJ proteins are disrupted in ZO-1/-2–depleted cells. In addition, immunocytochemistry and electron microscopy revealed a significant expansion of the perijunctional actomyosin ring associated with the AJ. These structural changes are accompanied by a recruitment of 1-phosphomyosin light chain and Rho kinase 1, contraction of the actomyosin ring, and expansion of the apical domain. Despite these changes in the apical cytoskeleton, there are no detectable changes in cell polarity, localization of AJ proteins, or the organization of the basal and lateral actin cytoskeleton. We conclude that ZO proteins are required not only for TJ assembly but also for regulating the organization and functional activity of the apical cytoskeleton, particularly the perijunctional actomyosin ring, and we speculate that these activities are relevant both to cellular organization and epithelial morphogenesis.
The effect of polymorphonuclear leukocytes (PMNs) on the subsequent chronic phase macrophage-mediated foreign body reaction has not been previously investigated. Furthermore, while monocyte/macrophage-produced cytokines such as GM-CSF, G-CSF, or IL-1β have been shown to increase PMN survival in vitro, few studies have examined the impact of directly co-cultured monocytes/macrophages on PMN viability. To this end, we used our established in vitro system of interleukin (IL)-4-induced monocyte-derived macrophage fusion to examine the role of PMNs in the subsequent foreign body reaction. Monocytes were directly cultured with PMNs for 3 days prior to the addition of IL-4 to induce monocyte-derived macrophage fusion to facilitate foreign body giant cell (FBGC) formation by Day 7 and Day 10 of culture. Optical microscopy was used to quantitatively determine adherent monocyte density, percent macrophage fusion, and FBGC density. A colorimetric MTT assay was used to assess PMN viability for direct co-cultures of monocytes/macrophages and PMNs. Our results strongly suggest that the presence of PMNs inhibit IL-4-induced macrophage fusion and FBGC formation. Additionally, our findings demonstrate that co-cultures containing PMNs and monocytes/macrophages increases PMN survival with respect to PMN-only cultures in vitro.
foreign body reaction; polymorphonuclear leukocytes; monocytes; macrophages; foreign body giant cells
Biofilm formation plays an integral role in catheter-associated bloodstream infections caused by Candida albicans. Biofilms formed on catheters placed intravenously are exposed to shear stress caused by blood flow. In this study, we investigated whether shear stress affects the ability of C. albicans to form biofilms. Candida biofilms were formed on catheter discs and exposed to physiological levels of shear stress using a rotating disc system (RDS). Control biofilms were grown under conditions of no flow. Tetrazolium (XTT) assay and dry weight (DW) measurements were used to quantify metabolic activity and biofilm mass respectively. Confocal scanning laser microscopy (CSLM) was used to evaluate architecture and biofilm thickness. After 90 min, cells attached under no-flow exhibited significantly greater XTT activity and DW than those under shear. However, by 24 h, biofilms formed under both conditions had similar XTT activities and DW. Interestingly, thickness of biofilms formed under no-flow was significantly greater after 24 h than of those formed under shear stress, demonstrating that shear exposure results in thinner, but denser biofilms. These studies suggest that biofilm architecture is modulated by shear in a phase-dependent manner.
Candida albicans; biofilms; shear stress; catheter infections
We report a case of Histoplasma capsulatum endocarditis in which Histoplasma antigen assay and fungal blood cultures were negative. The diagnosis was made by microscopic examination and culture of the excised valve. Histoplasma capsulatum should be considered in the differential diagnosis of culture-negative endocarditis in regions where it is endemic and in travelers.
Pre-eclampsia (PE) is associated with profound changes in the maternal cardiovascular system. The aim of the present study was to assess whether alterations in the maternal arterial stiffness precede the onset of PE in at risk women.
This was a cross sectional study involving 70 pregnant women with normal and 70 women with abnormal uterine artery Doppler examination at 22–24 weeks of gestation. All women had their arterial stiffness (augmentation index and pulse wave velocity of the carotid-femoral and carotid-radial parts of the arterial tree) assessed by applanation tonometry in the second trimester of pregnancy, at the time of the uterine artery Doppler imaging. Among the 140 women participating in the study 29 developed PE (PE group) and 111 did not (non-PE group). Compared to the non-PE group, women that developed PE had higher central systolic (94.9±8.6 mmHg vs 104.3±11.1 mmHg; p = <0.01) and diastolic (64.0±6.0 vs 72.4±9.1; p<0.01) blood pressures. All the arterial stiffness indices were adjusted for possible confounders and expressed as multiples of the median (MoM) of the non-PE group. The adjusted median augmentation index was similar between the two groups (p = 0.84). The adjusted median pulse wave velocities were higher in the PE group compared to the non-PE group (carotid-femoral: 1.10±0.14 MoMs vs 0.99±0.11 MoMs; p<0.01 and carotid-radial: 1.08±0.12 MoMs vs 1.0±0.11 MoMs; p<0.01).
Increased maternal arterial stiffness, as assessed by pulse wave velocity, predates the development of PE in at risk women.