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1.  Detecting cathepsin activity in human osteoarthritis via activity-based probes 
Lysosomal cathepsins have been reported to contribute to Osteoarthritis (OA) pathophysiology due to their increase in pro-inflammatory conditions. Given the causal role of cathepsins in OA, monitoring their specific activity could provide means for assessing OA severity. To this end, we herein sought to assess a cathepsin activity-based probe (ABP), GB123, in vitro and in vivo.
Protein levels and activity of cathepsins B and S were monitored by immunoblot analysis and GB123 labeling in cultured primary chondrocytes and conditioned media, following stimuli with tumor necrosis factor alpha (TNFα) and/or Interleukin 1 beta (IL-1β). Similarly, cathepsin activity was examined in sections of intact cartilage (IC) and degraded cartilage (DC) regions of OA. Finally, synovial fluid (SF) and serum from donors with no signs of diseases, early OA, late OA and rheumatoid arthritis (RA) patients were analyzed with GB123 to detect distinct activity levels of cathepsin B and S.
Cathepsin activity in cell lysates, conditioned media explants and DC sections showed enhanced enzymatic activity of cathepsins B and S. Further histological analysis revealed that cathepsin activity was found higher in superficial zones of DC than in IC. Examining serum and SF revealed that cathepsin B is significantly elevated with OA severity in serum and SF, yet levels of cathepsin S are more correlated with synovitis and RA.
Based on our data, cathepsin activity monitored by ABPs correlated well with OA severity and joint inflammation, directing towards a novel etiological target for OA, which possesses significant translational potential in developing means for non-invasive detection of early signs of OA.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0586-5) contains supplementary material, which is available to authorized users.
PMCID: PMC4415352  PMID: 25889265
2.  Evidence for the Adverse Effect of Starvation on Bone Quality: A Review of the Literature 
Malnutrition and starvation's possible adverse impacts on bone health and bone quality first came into the spotlight after the horrors of the Holocaust and the ghettos of World War II. Famine and food restrictions led to a mean caloric intake of 200–800 calories a day in the ghettos and concentration camps, resulting in catabolysis and starvation of the inhabitants and prisoners. Severely increased risks of fracture, poor bone mineral density, and decreased cortical strength were noted in several case series and descriptive reports addressing the medical issues of these individuals. A severe effect of severely diminished food intake and frequently concomitant calcium- and Vitamin D deficiencies was subsequently proven in both animal models and the most common cause of starvation in developed countries is anorexia nervosa. This review attempts to summarize the literature available on the impact of the metabolic response to Starvation on overall bone health and bone quality.
PMCID: PMC4355339  PMID: 25810719
3.  Stem cells for spine surgery 
World Journal of Stem Cells  2015;7(1):186-194.
In the past few years, stem cells have become the focus of research by regenerative medicine professionals and tissue engineers. Embryonic stem cells, although capable of differentiating into cell lineages of all three germ layers, are limited in their utilization due to ethical issues. In contrast, the autologous harvest and subsequent transplantation of adult stem cells from bone marrow, adipose tissue or blood have been experimentally utilized in the treatment of a wide variety of diseases ranging from myocardial infarction to Alzheimer’s disease. The physiologic consequences of stem cell transplantation and its impact on functional recovery have been studied in countless animal models and select clinical trials. Unfortunately, the bench to bedside translation of this research has been slow. Nonetheless, stem cell therapy has received the attention of spinal surgeons due to its potential benefits in the treatment of neural damage, muscle trauma, disk degeneration and its potential contribution to bone fusion.
PMCID: PMC4300930  PMID: 25621119
Stem cell; Spine surgery; Spinal cord injury; Peripheral nerve damage; Intervertebral disk regeneration; Fusion; Skeletal muscle regeneration
4.  Pediatric supracondylar humerus fractures: effect of bone–implant interface conditions on fracture stability 
Closed reduction and percutaneous fixation with Kirschner wires (KWs) is the standard of care of pediatric supra-condylar humerus fractures (SCHFs). Failure modes leading to loss of reduction are not clear and have not been quantified. Multiple factors may weaken the KW–bone interface bonding conditions. To the best of our knowledge, the possible effect of this decrease on different KW configurations and fracture stability has never been studied.
To investigate the effect of bone–KW friction conditions on SCHF post-operative mechanical stability and to formulate clinical guidelines for KW configuration under different conditions.
Finite element-based model of a fixated SCHF was used to simulate structure stability for two lateral divergent versus crossed lateral and medial KW configurations under varying KW–bone friction conditions.
Finite element simulations demonstrated that crossed KWs provide superior stability compared with the divergent configuration when KW–bone bonding is compromised. When KW–bone bonding conditions are adequate, crossed and divergent KW configurations provide similar, sufficient fracture stability.
Under normal bone–implant interface conditions, the two diverging lateral KW configuration offers satisfactory mechanical stability and may be the preferred choice of SCHF fixation. When KW–bone bonding is suboptimal, as when one or more of the lateral KWs are re-drilled, addition of a medial KW should be considered in order to improve stability despite risk to ulnar nerve.
PMCID: PMC3886359  PMID: 24432122
Pediatric; Supra-condylar; Finite elements; Kirschner wires
5.  75kDa SirT1 Blocks TNFα-Mediated Apoptosis in Human Osteoarthritic Chondrocytes 
Arthritis and Rheumatism  2012;64(3):718-728.
SirT1 has been previously implicated in the regulation of human cartilage homeostasis and chondrocyte survival. Exposing human osteoarthritic chondrocytes to TNFα generates a stable and enzymatically inactive 75kDa form of SirT1 (75SirT1) via Cathepsin B-mediated cleavage. Because 75SirT1 is resistant to further degradation, we assumed it has a distinct role in osteoarthritis (OA) pathology, which we sought out to identify in this study.
OA and normal human chondrocytes were analyzed for the presence of Cathepsin B and 75SirT1. Confocal imaging of SirT1 monitored its subcellular trafficking following TNFα stimulation. Co-immunofluorescent staining was carried out for Cathepsin B, mitochondrial Cox IV and Lysosome-associated membrane protein I (LAMP-I) together with SirT1. Human chondrocyte were tested for apoptosis via FACS analysis and immunoblotting for caspase 3 and 8. Human chondrocyte mitochondrial extracts were obtained and analyzed for 75SirT1/Cytochrome C association.
Confocal imaging and immunoblot analyses following TNFα challenge of human chondrocytes, demonstrated that 75SirT1 was exported to the cytoplasm and colocalized with the mitochondrial membrane. Consistently, immunoprecipitation and immunoblot analyses revealed that 75SirT1 is enriched in mitochondrial extracts and associates with Cytochrome C, following TNFα stimulation. Preventing nuclear export of 75SirT1 or reducing levels of FLSirT1 and 75SirT1 augmented chondrocyte apoptosis in the presence of TNFα Cathepsin B and 75SirT1 were elevated in OA vs. normal chondrocytes. Additional analyses shows that human chondrocytes exposed to OA-derived synovial fluid generate the 75SirT1 fragment.
These data suggest that 75SirT1 promotes chondrocyte survival following exposure to proinflammatory cytokines.
PMCID: PMC3269551  PMID: 21987377
6.  Reinforcing the role of the conventional C-arm - a novel method for simplified distal interlocking 
The common practice for insertion of distal locking screws of intramedullary nails is a freehand technique under fluoroscopic control. The process is technically demanding, time-consuming and afflicted to considerable radiation exposure of the patient and the surgical personnel. A new concept is introduced utilizing information from within conventional radiographic images to help accurately guide the surgeon to place the interlocking bolt into the interlocking hole. The newly developed technique was compared to conventional freehand in an operating room (OR) like setting on human cadaveric lower legs in terms of operating time and radiation exposure.
The proposed concept (guided freehand), generally based on the freehand gold standard, additionally guides the surgeon by means of visible landmarks projected into the C-arm image. A computer program plans the correct drilling trajectory by processing the lens-shaped hole projections of the interlocking holes from a single image. Holes can be drilled by visually aligning the drill to the planned trajectory. Besides a conventional C-arm, no additional tracking or navigation equipment is required.
Ten fresh frozen human below-knee specimens were instrumented with an Expert Tibial Nail (Synthes GmbH, Switzerland). The implants were distally locked by performing the newly proposed technique as well as the conventional freehand technique on each specimen. An orthopedic resident surgeon inserted four distal screws per procedure. Operating time, number of images and radiation time were recorded and statistically compared between interlocking techniques using non-parametric tests.
A 58% reduction in number of taken images per screw was found for the guided freehand technique (7.4 ± 3.4) (mean ± SD) compared to the freehand technique (17.6 ± 10.3) (p < 0.001). Total radiation time (all 4 screws) was 55% lower for the guided freehand technique compared to conventional freehand (p = 0.001). Operating time per screw (from first shot to screw tightened) was on average 22% reduced by guided freehand (p = 0.018).
In an experimental setting, the newly developed guided freehand technique for distal interlocking has proven to markedly reduce radiation exposure when compared to the conventional freehand technique. The method utilizes established clinical workflows and does not require cost intensive add-on devices or extensive training. The underlying principle carries potential to assist implant positioning in numerous other applications within orthopedics and trauma from screw insertions to placement of plates, nails or prostheses.
PMCID: PMC3305668  PMID: 22276698
Distal interlocking; Distal targeting; Nailing; Free-hand locking; Computer aided surgery
7.  The Induction of APC with a Distinct Tolerogenic Phenotype via Contact-Dependent STAT3 Activation 
PLoS ONE  2009;4(8):e6846.
Activation of the signal transducer and activator of transcription 3 (STAT3) within antigen presenting cells (APCs) is linked to abnormal APCs differentiation and function. We have previously shown that STAT3 is activated within APC by a novel contact-dependent mechanism, which plays a key role in mediating the immunomodulatory effects of hMSC. In order to better understand the underlying mechanisms that control APC maturation in a contact dependent manner, we extended our observation to tumor cells. Tumors were shown to secrete a variety of tumor-derived factors that activate STAT3 within infiltrating APCs. We now tested whether tumor cells can activate STAT3 within APC using the contact-dependent mechanism, in addition to soluble factors, and compared these two STAT3 activating pathways.
Principal Findings
We demonstrate that in addition to tumor-derived secreted factors tumor cells activate STAT3 by a mechanism that is based on cell-cell interaction. We further demonstrate that these two STAT3 activating mechanisms differ in their JAK usage and their susceptibility to JSI-124 inhibition thereby representing two distinct pathways. Significantly, although both pathways activate STAT3, they modulate DCs maturation in a different manner that results in disparate phenotypic outcomes. Whereas the soluble-dependent pathway results in an immature phenotype, the contact-dependent pathway results in an apparently mature phenotype. Albeit their mature-like phenotype these latter cells express the tolerogenic markers ILT3 and ILT4 and possess T cell inhibitory activity.
This data suggests that, in at least certain cellular microenvironments, cell:cell interactions represent a novel way to activate STAT3 signaling, uncouple APC activation events and consequently regulate immunity and tolerance. Significantly, we have now demonstrated that this contact-dependent signaling pathway differs from that mediated by soluble factors and cytokines, inducing disparate phenotypic outcome, suggesting these two mechanisms have different and possibly complementary biological functions.
PMCID: PMC2731174  PMID: 19718269
8.  Bipolar hip hemiarthroplasty in a patient with an above knee amputation: a case report 
The treatment of an above knee amputee who has sustained a fracture of femoral neck is a challenge for both the orthopaedic surgeon and the rehabilitation team. We present a case of such a patient and discuss different difficulties in his treatment.
PMCID: PMC2734558  PMID: 19646230
9.  Computerized Navigation for Treatment of Slipped Femoral Capital Epiphysis 
HSS Journal  2006;2(2):172-175.
In situ pinning with a single screw is the treatment of choice for symptomatic slipped capital femoral epiphysis (SCFE). Some technical features are critical and include proper screw entry point, screw direction in relation to the epiphysis, and the length of screw. These are complicated by the deformity created as a result of the posterior slip of the epiphysis. Fluoroscopic based computerized navigation system can increase precision in screw placement while performing the surgical task, and markedly reduce radiation. By using real fluoroscopy-based navigation, the screw can be placed with only two fluoroscopic images. Entry point, length, and precise direction can all be easily determined through this technique.
PMCID: PMC2488163  PMID: 18751832
slipped capital femoral epiphysis; computerized navigation; in situ pinning

Results 1-9 (9)