Lgr5-expressing secretory cells form a Wnt inhibitory niche in cartilage critical for chondrocyte identity.

Osteoarthritis is a degenerative joint disease that causes pain, degradation, and dysfunction. Excessive canonical Wnt signaling in osteoarthritis contributes to chondrocyte phenotypic instability and loss of cartilage homeostasis; however, the regulatory niche is unknown. Using the temporomandibular joint as a model in multiple species, we identify Lgr5-expressing secretory cells as forming a Wnt inhibitory niche that instruct Wnt-inactive chondroprogenitors to form the nascent synovial joint and regulate chondrocyte lineage and identity. Lgr5 ablation or suppression during joint development, aging, or osteoarthritis results in depletion of Wnt-inactive chondroprogenitors and a surge of Wnt-activated, phenotypically unstable chondrocytes with osteoblast-like properties. We recapitulate the cartilage niche and create StemJEL, an injectable hydrogel therapy combining hyaluronic acid and sclerostin. Local delivery of StemJEL to post-traumatic osteoarthritic jaw and knee joints in rabbit, rat, and mini-pig models restores cartilage homeostasis, chondrocyte identity, and joint function. We provide proof of principal that StemJEL preserves the chondrocyte niche and alleviates osteoarthritis.

Bridging gaps in oral health education in a medical school in the United States: a pilot study.

BACKGROUND: Oral health is an important component of medical education given its connection to overall health and quality of life; however, oral health is infrequently incorporated into medical school curricula in the United States. The aim of this study was to pilot a novel oral health care clerkship for United States medical students that implemented the Smiles for Life (SFL) curriculum, in-person clinical activities, and pre and post curricula assessments to assess knowledge acquisition, attitude change, and clinical skill development. METHODS: Third year medical students at Albert Einstein College of Medicine, Bronx, New York, volunteered (n = 37) for a clerkship in oral health. Students completed the Smiles For Life National Oral Health Curriculum and participated in three half-day clinical sessions in a hospital-based dental clinic. The participants were evaluated on knowledge acquisition, attitude change, and clinical skill development through a pre and post clerkship assessment in order to assess the efficacy of the intervention. RESULTS: There was a 23.4% increase in oral health knowledge (p < 0.001) following participation in the online modules and clerkship. Additionally, attitudes in the following domains showed improved familiarity and proficiency: causes and prevention of dental caries (78.4%, p < 0.001) and periodontal disease (83.8%, p < 0.001), provision of oral health information to patients (67.6%, p < 0.001), and ability to conduct an oral examination (62.2%, p < 0.001). CONCLUSIONS: Third year medical students who participated in a novel oral health clerkship demonstrated significant increases in basic oral health knowledge and reported increased comfort in providing oral examinations and anticipatory guidance to patients. The results support the feasibility of this approach to incorporating oral health education into a medical school curriculum in the United States.

Evidence of vasculature and chondrocyte to osteoblast transdifferentiation in craniofacial synovial joints: Implications for osteoarthritis diagnosis and therapy.

Temporomandibular joint osteoarthritis (TMJ OA) leads to permanent cartilage destruction, jaw dysfunction, and compromises the quality of life. However, the pathological mechanisms governing TMJ OA are poorly understood. Unlike appendicular articular cartilage, the TMJ has two distinct functions as the synovial joint of the craniofacial complex and also as the site for endochondral jaw bone growth. The established dogma of endochondral bone ossification is that hypertrophic chondrocytes undergo apoptosis, while invading vasculature with osteoprogenitors replace cartilage with bone. However, contemporary murine genetic studies support the direct differentiation of chondrocytes into osteoblasts and osteocytes in the TMJ. Here we sought to characterize putative vasculature and cartilage to bone transdifferentiation using healthy and diseased TMJ tissues from miniature pigs and humans. During endochondral ossification, the presence of fully formed vasculature expressing CD31+ endothelial cells and α-SMA+ vascular smooth muscle cells were detected within all cellular zones in growing miniature pigs. Arterial, endothelial, venous, angiogenic, and mural cell markers were significantly upregulated in miniature pig TMJ tissues relative to donor matched knee meniscus fibrocartilage tissue. Upon surgically creating TMJ OA in miniature pigs, we discovered increased vasculature and putative chondrocyte to osteoblast transformation dually marked by COL2 and BSP or RUNX2 within the vascular bundles. Pathological human TMJ tissues also exhibited increased vasculature, while isolated diseased human TMJ cells exhibited marked increased in vasculature markers relative to control 293T cells. Our study provides evidence to suggest that the TMJ in higher order species are in fact vascularized. There have been no reports of cartilage to bone transdifferentiation or vasculature in human-relevant TMJ OA large animal models or in human TMJ tissues and cells. Therefore, these findings may potentially alter the clinical management of TMJ OA by defining new drugs that target angiogenesis or block the cartilage to bone transformation.

Extracellular matrix turnover and inflammation in chemically-induced TMJ arthritis mouse models.

The temporomandibular joint (TMJ) is a fibrocartilaginous tissue critical for chewing and speaking. In patients with temporomandibular disorders (TMDs), permanent tissue loss can occur. Recapitulating the complexity of TMDs in animal models is difficult, yet critical for the advent of new therapies. Synovial fluid from diseased human samples revealed elevated levels of tumor necrosis factor alpha (TNF-alpha). Here, we propose to recapitulate these findings in mice by subjecting murine TMJs with TNF-alpha or CFA (Complete Freund's Adjuvant) in mandibular condyle explant cultures and by local delivery in vivo using TMJ intra-articular injections. Both TNF-alpha and CFA delivery to whole mandibular explants and in vivo increased extracellular matrix deposition and increased cartilage thickness, while TNF-alpha treated explants had increased expression of inflammatory cytokines and degradative enzymes. Moreover, the application of TNF-alpha or CFA in both models reduced cell number. CFA delivery in vivo caused soft tissue inflammation, including pannus formation. Our work provides two methods of chemically induced TMJ inflammatory arthritis through a condyle explant model and intra-articular injection model that replicate findings seen in synovial fluid of human patients, which can be used for further studies delineating the mechanisms underlying TMJ pathology.