Faculty Bibliography

Purpose: A necessary step for the successful regeneration of cartilage lesions using stem cell-based therapies is the controlled differentiation of progenitor cells into a stable articular chondrocyte phenotype. Prostaglandin E2 (PGE2) has been shown to have an important role in both fracture healing and chondrocyte maturation during endochondral bone formation. This study investigates the effects of PGE2 on chondrocyte differentiation of adult, human mesenchymal stem cells (MSCs). Methods: Bone marrow-derived MSCs were isolated from the discarded tissues of patients undergoing hip replacement surgery. Chondrogenesis was induced by seeding MSCs in serum-free aggregate cultures supplemented with dexamethasone (10-7 M) and TGF-b1 (10 ng/ml). At various time points, RNA was extracted for gene expression analysis by semi-quantitative RT-PCR. PGE2 levels were determined by RIA. Results: Gene expression analysis of 4 patient samples revealed an order-of-magnitude increase in chondrogenic markers, col II, col X, MMP-13 and AP. In each case, expression was elevated by day 7 and persisted for the duration of the assay (21 d). To determine the effects of PGE2, aggregates were cocultured in the presence of exogenous PGE2 (10-6 M) and expression of chondrocyte markers determined after 14 d. PGE2 increased expression of col II (65%) and decreased expression of hypertrophic markers, col X (20%), MMP-13 (32 %) and AP (55%). Consistent with these observations, histological examination of treated aggregates after 21 d revealed fewer enlarged, hypertrophic chondrocytes following PGE2 treatment compared to control cultures. In aggregate cultures, PGE2 secretion was inhibited by the selective cox-2 inhibitor, celecoxib, approximately 50%, while cox-1 inhibition by treatment with SC-560 had no effect. Accordingly, celecoxib treatment of chondrogenic aggregates for 7 d decreased expression of sox-9 (80%) and col II (97%) compared non-treated controls. Cox-2 inhibition also increased expression of hypertrophic markers. Celecoxib treatment increased col X (95%) and AP (150%), but had no effect on MMP-13 levels. After 21 d, aggregates treated with celecoxib exhibited greater numbers of hypertrophic chondrocytes, and a modest decrease in proteoglycan staining. These findings suggest that cox-2 derived PGE2 has the capacity modulate chondrocyte differentiation of MSCs via differential regulation of chondrocyte marker genes. Conclusion: PGE2, via upregulation of type II collagen, or inhibition of chondrocyte hypertrophy, has the capacity to regulate chondrocyte phenotype during in vitro chondrogenesis of hMSCs. Further characterization should uncover novel PGE2 pathways that can be exploited to modulate chondrocyte phenotype for tissue regeneration therapies

Osteoarthritis is often a progressive and disabling disease, which occurs in the setting of a variety of risk factors--such as advancing age, obesity, and trauma--that conspire to incite a cascade of pathophysiologic events within joint tissues. An important emerging theme in osteoarthritis is a broadening of focus from a disease of cartilage to one of the 'whole joint'. The synovium, bone, and cartilage are each involved in pathologic processes that lead to progressive joint degeneration. Additional themes that have emerged over the past decade are novel mechanisms of cartilage degradation and repair, the relationship between biomechanics and biochemical pathways, the importance of inflammation, and the role played by genetics. In this review we summarize current scientific understanding of osteoarthritis and examine the pathobiologic mechanisms that contribute to progressive disease

OBJECTIVE:To examine effects of the COX-2 inhibitor market withdrawals on NSAID utilization among patients at increased risk of gastrointestinal (GI) and cardiovascular (CV) toxicities. METHODS:A prospective cohort study was conducted using patients enrolled in the Consortium of Rheumatology Researchers of North America (CORRONA) Registry. The study population included rheumatoid arthritis (RA) and psoriatic arthritis (PsA) patients prescribed NSAIDs by rheumatologists from 1/1/2003 to 12/31/2005. Three cohorts were defined based on calendar year. The primary outcome assessed whether or not an NSAID gastroprotective strategy was prescribed. Secondary outcomes included rates of COX-2 inhibitor utilization and gastroprotective co-therapy utilization, stratified by the presence of cardiac and GI risk factors. RESULTS:NSAID gastroprotection utilization decreased from 65.1% in 2003 to 47.7% (p<0.001) in 2005. COX-2 inhibitor use decreased from 55.1% to 29.2% (p<0.001), whereas nonselective NSAIDs (nsNSAIDs) use increased from 50.2% to 73.9% (p=<0.01). Among patients with two or more risk factors for NSAID related GI bleeding, gastroprotection decreased from 74.4% in 2003 to 60.9% (p<0.01). For patients with two or more CV risk factors from 2003 to 2005, COX-2 inhibitor utilization decreased significantly, whereas nsNSAID utilization increased significantly.CONCLUSIONS:The COX-2 inhibitor withdrawals resulted in a rapid decline in NSAID gastroprotection prescribed by participating U.S. rheumatologists despite the availability of other gastroprotective options. Channeling toward nsNSAID use was widespread, including among patients at increased CV risk. Longer term follow-up is required to determine the clinical significance of these changes in NSAID prescribing, particularly for NSAID-related GI and CV-related toxicities

Annexins are intracellular molecules implicated in the down-regulation of inflammation. Recently, annexin-1 has also been identified as a secreted molecule, suggesting it may have more complex effects on inflammation than previously appreciated. We studied the role of annexin-1 in mediating MMP-1 secretion from rheumatoid arthritis (RA) synovial fibroblasts (SF) stimulated with TNF-alpha. TNF-alpha induced a biphasic secretion of annexin-1 from RA SF. Early (< or = 60 min), cycloheximide-independent secretion from preformed intracellular pools was followed by late (24 h) cycloheximide-inhibitable secretion requiring new protein synthesis. Exogenous annexin-1 N-terminal peptide Ac2-26 stimulated MMP-1 secretion in a dose- (EC(50) approximately 25 microM) and time- (8-24 h) dependent manner; full-length annexin-1 had a similar effect. Down-regulation of annexin-1 using small interfering RNA resulted in decreased secretion of both annexin-1 and MMP-1, confirming that annexin-1 mediates TNF-alpha-stimulated MMP-1 secretion. Erk, Jnk, and NF-kappaB have been implicated in MMP-1 secretion. Erk, Jnk, and NF-kappaB inhibitors had no effect on annexin-1 secretion stimulated by TNF-alpha but inhibited MMP-1 secretion in response to Ac2-26, indicating that these molecules signal downstream of annexin-1. Annexin-1 stimulation of MMP-1 secretion was inhibited by both a formyl peptide receptor antagonist and pertussis toxin, suggesting that secreted annexin-1 acts via formyl peptide family receptors, most likely FPLR-1. In contrast to its commonly appreciated anti-inflammatory roles, our data indicate that annexin-1 is secreted by RA SF in response to TNF-alpha and acts in an autacoid manner to engage FPRL-1, activate Erk, Jnk, and NF-kappaB, and stimulate MMP-1 secretion

OBJECTIVE: Recommendations for screening for latent Mycobacterium tuberculosis (MTB) infection have been proposed but are not well studied in patients with rheumatoid arthritis (RA). We estimated the prevalence of anergy in RA and evaluated different methods to detect MTB exposure. METHODS: This was a prospective pilot study of 61 patients with RA and 42 healthy controls. Tuberculin skin test (TST) antigen, Candida, and tetanus toxoid were injected intradermally using the Mantoux method. Subjects negative for TST returned for a second-step test. Whole-blood interferon-gamma (IFN-gamma) release to mycobacterial antigens was evaluated with the first-generation QuantiFeron test (QIFN). RESULTS: Cutaneous anergy in patients with RA was not significantly different than healthy controls (p = 0.154), and was not affected by disease modifying antirheumatic drugs (p = 0.270). In patients with RA, 16.4% had positive TST with 10 mm cutoff vs 11.9% of controls. Using a 5 mm cutoff, 21.3% of patients with RA were positive, and this increased to 29.5% with a second-step TST. QIFN detected MTB exposure in 18% of patients with RA and 19% of controls (p = 0.897). However, indeterminate QIFN tests were higher in RA patients (11.5%) compared to controls (2.4%), demonstrating a lower sensitivity to detect latent MTB. CONCLUSION: Cutaneous anergy may be less common than previously reported in patients with RA. patients. However, the single-step TST and 10 mm cutoff may fail to detect all cases of latent exposure in RA patients. High rates of indeterminate results in QIFN testing suggest that QIFN should not be employed as an alternative, single-screening test in patients with RA. These pilot results require confirmation in larger studies to determine the optimal screening strategy in RA