Faculty Bibliography

Osteoarthritis (OA) is a highly prevalent, disabling joint disease with no existing therapies to slow or halt its progression. Cartilage degeneration hallmarks OA pathogenesis, and pannexin 3 (Panx3), a member of a novel family of channel proteins, is upregulated during this process. The function of Panx3 remains poorly understood, but we consistently observed a strong increase in Panx3 immunostaining in OA lesions in both mice and humans. Here, we developed and characterized the first global and conditional Panx3 knockout mice to investigate the role of Panx3 in OA. Interestingly, global Panx3 deletion produced no overt phenotype and had no obvious effect on early skeletal development. Mice lacking Panx3 specifically in the cartilage and global Panx3 knockout mice were markedly resistant to the development of OA following destabilization of medial meniscus surgery. These data indicate a specific catabolic role of Panx3 in articular cartilage and identify Panx3 as a potential therapeutic target for OA. Lastly, while Panx1 has been linked to over a dozen human pathologies, this is the first in vivo evidence for a role of Panx3 in disease. KEY MESSAGE: Panx3 is localized to cartilage lesions in mice and humans. Global Panx3 deletion does not result in any developmental abnormalities. Mice lacking Panx3 are resistant to the development of osteoarthritis. Panx3 is a novel therapeutic target for the treatment of osteoarthritis.

OBJECTIVE: Inflammatory mediators, such as PGE2 and IL-1beta, are produced by osteoarthritic joint tissues, where they may contribute to disease pathogenesis. We examined whether inflammation, reflected in plasma and peripheral blood leukocytes (PBLs) reflected presence of osteoarthritis (OA), progression or symptoms in patients with symptomatic knee osteoarthritis (SKOA). METHODS: SKOA patients were enrolled in a 24-month prospective study of radiographic progression. Standardized knee radiographs were obtained at baseline and 24 months. Biomarkers assessed at baseline included plasma lipids PGE2 and 15-HETE, and transcriptome analysis of PBLs by microarray and qPCR. RESULTS: Baseline PGE synthases (PGES) by PBL microarray gene expression, and plasma PGE2 distinguished SKOA patients from non-OA controls (AUCs 0.87 and 0.89 respectively, p<0.0001). Baseline plasma 15-HETE was significantly elevated in SKOA versus non-OA controls (p<0.019). In the 146 patients who completed the 24-month study, elevated baseline expression of IL-1beta, TNFalpha and COX-2 mRNA in PBLs predicted higher risk for radiographic progression by joint space narrowing (JSN). In a multivariate model, AUC point estimates of models containing COX-2 in combination with demographic traits overlap the confidence interval of the base model in two out of the three JSN outcome measures (JSN >0.0mm, >0.2mm and >0.5mm, AUC=0.62-0.67). CONCLUSION: Inflammatory plasma lipid biomarkers PGE2 and 15-HETE identify patients with SKOA. PBL inflammatory transcriptome identifies a subset of SKOA patients at higher risk for radiographic progression. These findings may reflect low-grade inflammation in OA and may be useful as diagnostic and prognostic biomarkers in clinical development of disease-modifying OA drugs

Purpose: We and others have demonstrated low grade inflammation exists in OA joint tissues, where it may contribute to disease pathogenesis. In the current studies we assessed whether inflammatory events occurring within joint tissues were reported in the peripheral blood leukocytes (PBLs) of patients with symptomatic knee OA (SKOA). Methods: PBL inflammatory gene expression (IL-1, TNFalpha, COX-2) was assessed in two independent cohorts of patients with SKOA, and a cohort of healthy control subjects: 1) 111 patients with tibiofemoral medial OA and 21 healthy volunteers from the NYUHJD Cohort, and 2) 200 patients from the OAI progression cohort who had "high quality radiographs", at both baseline and 24 months, and had KL2 or 3 in the signal knee at baseline. Radiographic progression was defined as narrowing of medial joint space width (JSW) in the signal knee between baseline and 24-months in each cohort. Radiographic progressors were defined as subjects who had JSN >0.0, 0.2 and 0.5mm over 24 months. For measuring predictive performance, we used the area under the curve (AUC) of a receiver operating characteristics (ROC). OAI SKOA subjects were dichotomized as radiographic non-progressors (JSN <0.0 mm) and progressors (JSN>0.0mm) for association studies. Results: Elevated PBL expression of IL-1, TNFalpha or COX-2 identified SKOA patients who were "fast progressors" (mean JSN 0= 0.71, 0.75 and 0.71 mm / 24 months, respectively) compared to patients with levels below the median. In a multivariable model, anthropometric traits alone (BMI, gender, age) did not predict progression, whereas addition of PBL gene expressions improved prediction of fast progressors (JSN>0.5mm). We next examined inflammatory gene expression in PBLs of radiographic progressors in the OAI cohort. Similar to the NYUHJD cohort, elevated expression of IL-1beta, TNFalpha and COX-2 mRNA distinguished radiographic progressors from non-progressors (Table 1). PBL IL-1beta expression found to be strongest predictor of all three radiographic progressors. In multivariate models that combine all three markers did not improve upon IL-1beta predictivity. We thus conclude that either the signal in TNFalpha and Cox-2 is already subsumed by IL-1beta and/or that it is not easy to capture the non-overlapping signals without increasing the sample size (i.e., fitting a stronger multivariate predictor will require more sample size). Conclusions: We identified, and confirmed in two cohorts, increased inflammatory gene expression (IL-1, TNFalpha or COX-2) by PBLs that predict radiographic progression in patients with SKOA. The data indicate that inflammatory events within joint tissues of patients with SKOA are reported in the peripheral blood. These PBL transcriptome signals of local joint inflammation merit further study as potential biomarkers for OA disease progression. (Table Presented)

We investigated the role of periostin, an extracellular matrix protein, in the pathophysiology of osteoarthritis (OA). In OA, dysregulated gene expression and phenotypic changes in articular chondrocytes culminate in progressive loss of cartilage from the joint surface. The molecular mechanisms underlying this process are poorly understood. We examined periostin expression by immunohistochemical analysis of lesional and nonlesional cartilage from human and rodent OA knee cartilage. In addition, we used small interfering (si)RNA and adenovirus transduction of chondrocytes to knock down and up-regulate periostin levels, respectively, and analyzed its effect on matrix metalloproteinase (MMP)-13, a disintegrin and MMP with thrombospondin motifs (ADAMTS)-4, and type II collagen expression. We found high periostin levels in human and rodent OA cartilage. Periostin increased MMP-13 expression dose [1-10 microg/ml (EC50 0.5-1 mug/ml)] and time (24-72 h) dependently, significantly enhanced expression of ADAMTS4 mRNA, and promoted cartilage degeneration through collagen and proteoglycan degradation. Periostin induction of MMP-13 expression was inhibited by CCT031374 hydrobromide, an inhibitor of the canonical Wnt/beta-catenin signaling pathway. In addition, siRNA-mediated knockdown of endogenous periostin blocked constitutive MMP-13 expression. These findings implicate periostin as a catabolic protein that promotes cartilage degeneration in OA by up-regulating MMP-13 through canonical Wnt signaling.-Attur, M., Yang, Q., Shimada, K., Tachida, Y., Nagase, H., Mignatti, P., Statman, L., Palmer, G., Thorsten, K., Beier, F., Abramson, A. B. Elevated expression of periostin in human osteoarthritic cartilage and its potential role in matrix degradation via matrix metalloproteinase-13.

The aims of this study are to compare plasma levels of IL17A, A/F, and F biomarkers in RA patients versus controls, and to determine responsiveness to methotrexate (MTX), anti-TNFs, and abatacept. We selected plasma samples from RA cohorts consisting of a cross-sectional RA cohort (N = 78) not receiving DMARDs at the time of sampling, as well as from longitudinal drug start cohorts (N = 71 patients) with pre/post samples including anti-TNF, abatacept, and MTX-treated patients. We assayed IL-17A, IL-17F, and IL17-A/F using a highly sensitive immunoassay system. Plasma levels of IL-17A, IL-17A/F, and IL-17F were all significantly increased in RA versus controls. The difference was largest in IL-17F, with median IL-17F levels in RA patients being approximately 18-fold higher than controls (81 pg/mL in RA vs. 4.4 pg/mL in controls, p < 0.001). Among the forms of IL-17, only IL-17F was decreased after therapy in the MTX cohort (p = 0.006), abatacept cohort (p < 0.001), and anti-TNF cohorts (p = 0.02), whereas IL-17A and IL-17A/F were not significantly decreased for any of the three drug cohorts. Synovial fluid analysis demonstrated higher IL-17F levels in RA (p = 0.016) than healthy controls. These results suggest a specific role for IL-17F in human RA pathogenesis and as a therapeutic target.

OBJECTIVE: To characterize the diversity and taxonomic relative abundance of the gut microbiota in patients with never-treated, recent-onset psoriatic arthritis (PsA). METHODS: High-throughput 16S ribosomal RNA pyrosequencing was utilized to compare the community composition of gut microbiota in patients with PsA (n = 16), patients with psoriasis of the skin (n = 15), and healthy, matched control subjects (n = 17). Samples were further assessed for the presence and levels of fecal and serum secretory IgA (sIgA), proinflammatory proteins, and fatty acids. RESULTS: The gut microbiota observed in patients with PsA and patients with skin psoriasis was less diverse when compared to that in healthy controls. This could be attributed to the reduced presence of several taxa. Samples from both patient groups showed a relative decrease in abundance of Coprococcus species, while samples from PsA patients were also characterized by a significant reduction in Akkermansia, Ruminococcus, and Pseudobutyrivibrio. Supernatants of fecal samples from PsA patients revealed an increase in sIgA levels and decrease in RANKL levels. Analysis of fatty acids revealed low fecal quantities of hexanoate and heptanoate in both patients with PsA and patients with psoriasis. CONCLUSION: Patients with PsA and patients with skin psoriasis had a lower relative abundance of multiple intestinal bacteria. Although some genera were concomitantly decreased in both conditions, PsA samples had a lower abundance of reportedly beneficial taxa. This gut microbiota profile in PsA was similar to that previously described in patients with inflammatory bowel disease and was associated with changes in specific inflammatory proteins unique to this group, and distinct from that in patients with skin psoriasis and healthy controls. Thus, the role of the gut microbiome in the continuum of psoriasis-PsA pathogenesis and the associated immune response merits further study.