TET1 Regulates Skeletal Stem-Cell Mediated Cartilage Regeneration

Melatonin ameliorates Slc26a2-associated chondrodysplasias by attenuating endoplasmic reticulum stress and apoptosis of chondrocytes

Although the pathogenesis and mechanism of congenital skeletal dysplasia are better understood, progress in drug development and intervention research remains limited. Here we report that melatonin treatment elicits a mitigating effect on skeletal abnormalities caused by SLC26A2 deficiency. In addition to our previous finding of endoplasmic reticulum stress upon SLC26A2 deficiency, we found calcium (Ca2+) overload jointly contributed to SLC26A2-associated chondrodysplasias. Continuous endoplasmic reticulum stress and cytosolic Ca2+ overload in turn triggered apoptosis of growth plate chondrocytes. Melatonin, known for its anti-oxidant and anti-inflammatory properties, emerged as a promising therapeutic approach in our study, which enhanced survival, proliferation, and maturation of chondrocytes by attenuating endoplasmic reticulum stress and Ca2+ overload. Our findings not only demonstrated the efficacy of melatonin in ameliorating abnormal function and cell fate of SLC26A2-deficient chondrocytes in vitro but also underscored its role in partially alleviating the skeletal dysplasia seen in Col2a1-CreER T2 ; Slc26a2 fl/fl mice. As revealed by histology and micro-CT analyses, melatonin significantly improved retarded cartilage growth, defective trabecular bone formation, and tibial genu varum in vivo. Collectively, these data shed translational insights for drug development and support melatonin as a potential treatment for SLC26A2-related chondrodysplasias.

Melatonin promotes the proliferation and differentiation of antler chondrocytes via RUNX2 dependent on the interaction between NOTCH1 and SHH signaling pathways

Melatonin (MT), an endogenous hormone secreted by pineal gland, has the sedative, anti-inflammatory and antioxidant functions. However, there are few studies on whether MT affects the proliferation and differentiation of antler chondrocytes. The present study investigated the influences of MT on the proliferation and differentiation of antler chondrocytes, explored its regulation on runt-related transcription factor 2 (RUNX2), NOTCH1 and sonic hedgehog (SHH) signaling, and elucidated their interplays. The results showed that MT promoted the proliferation of antler chondrocytes and induced the differentiation of chondrocytes into hypertrophic chondrocytes as evidenced by the significant increase of collagen type X (COL X), alkaline phosphatase (ALP) and matrix metalloproteinase 13 (MMP13) expression and ALP activity, the well-established markers for hypertrophic chondrocytes, but this effectiveness was neutralized by the addition of MT receptor antagonist. Further analysis indicated that MT activated the NOTCH1 and SHH signaling whose blockage abrogated the inducement of MT on the proliferation and differentiation of antler chondrocytes. SHH was identified as a downstream target of recombination signal binding protein for immunoglobulin kappa J region (RBPJ), a transcription factor of NOTCH1 signaling. Meanwhile, MT stimulated the expression of RUNX2 through activating the SHH signaling whose downstream transcription factor glioma-associated oncogene 1 (GLI1) directly controlled the transcription of RUNX2 through binding to its promoter region. Moreover, repression of GLI1 counteracted the proliferative effect of MT on antler chondrocytes and attenuated the advancement of MT on chondrocyte differentiation, while supplementation of recombinant RUNX2 protein recued above effects. Collectively, MT induced the proliferation and differentiation of antler chondrocytes via RUNX2 dependent on the interaction between NOTCH1 and SHH signaling pathways.

High-precision bioactive scaffold with dECM and extracellular vesicles targeting 4E-BP inhibition for cartilage injury repair

The restoration of cartilage injuries remains a formidable challenge in orthopedics, chiefly attributed to the absence of vascularization and innervation in cartilage. Decellularized extracellular matrix (dECM) derived from cartilage, following antigenic removal through decellularization processes, has exhibited remarkable biocompatibility and bioactivity, rendering it a viable candidate for cartilage repair. Additionally, extracellular vesicles (EVs) generated from cartilage have demonstrated a synergistic effect when combined with dECM, potentially mitigating the inhibitory impact on protein synthesis by phosphorylating 4ebp, thereby promoting the synthesis of cartilage-related proteins such as collagen. In pursuit of this objective, we have innovated a novel bioink and repair scaffold characterized by exceptional biocompatibility, bioactivity, and biodegradability, establishing a tissue-specific microenvironment conducive to chondrogenesis. Within rat osteochondral defects, the biologically active scaffold successfully prompted the formation of transparent cartilage, featuring adequate mechanical strength, favorable elasticity, and dECM deposition indicative of cartilage. In summary, this study has effectively engineered a hydrogel bioink tailored for cartilage repair and devised a bioactive cartilage repair scaffold proficient in instigating cell differentiation and fostering cartilage repair.

Melatonin is a potential novel analgesic agent for osteoarthritis: Evidence from cohort studies in humans and preclinical research in rats

Melatonin exhibits potential for pain relief and long-term safety profile. We examined the analgesic effects of oral melatonin on osteoarthritis (OA) and investigated the underlying mechanism. Using data from a UK primary care database, we conducted a cohort study in individuals with OA to compare the number of oral analgesic prescriptions and the risk of knee/hip replacement between melatonin initiators and hypnotic benzodiazepines (i.e., active comparator) initiators using quantile regression models and Cox-proportional hazard models, respectively. To elucidate causation, we examined the effects of melatonin on pain behaviors and explored several metabolites that may serve as potential regulatory agents of melatonin in the monoiodoacetate rat model of OA. Using data from another community-based cohort study, that is, the Xiangya OA Study, we verified the association between the key serum metabolite and incident symptomatic knee OA. Compared with the hypnotic benzodiazepines cohort (n = 8135), the melatonin cohort (n = 813) had significantly fewer subsequent prescriptions of oral analgesics (50th percentile: 5 vs. 7, 75th percentile: 19 vs. 29, and 99th percentile: 140 vs. 162) and experienced a lower risk of knee/hip replacement (hazard ratio = 0.47, 95% Cl: 0.30-0.73) during the follow-up period. In rats, oral melatonin alleviated pain behaviors and increased serum levels of glycine. There was an inverse association between baseline serum glycine levels and the risk of incident symptomatic knee OA in humans (n = 760). In conclusion, our findings indicate that oral melatonin shows significant potential to be a novel treatment for OA pain. The potential role of glycine in its analgesic mechanism warrants further investigation.

Targeting an inflammation-amplifying cell population can attenuate osteoarthritis-associated pain

BACKGROUND

Understanding of pain in osteoarthritis, its genesis, and perception is still in its early stages. Identification of precise ligand-receptor pairs that transduce pain and the cells and tissues in which they reside will elucidate new therapeutic approaches for pain management. Our recent studies had identified an inflammation-amplifying (Inf-A) cell population that is expanded in human OA cartilage and is distinctive in the expression of both IL1R1 and TNF-R2 receptors and active Jnk signaling cascade.

METHODS

In this study, we have tested the function of the cartilage-resident IL1R1+TNF-R2+ Inf-A cells in OA. We have identified that the IL1R1+TNF-R2+ Inf-A cells expand in aged mice as well as after anterior cruciate ligament tear upon tibia loading and OA initiation in mice. We targeted and modulated the Jnk signaling cascade in InfA through competitive inhibition of Jnk signaling in mice and human OA explants and tested the effects on joint structure and gait in mice.

RESULTS

Modulation of Jnk signaling led to attenuation of inflammatory cytokines CCL2 and CCL7 without showing any structural improvements in the joint architecture. Interestingly, Jnk inhibition and lowered CCL2 and 7 are sufficient to significantly improve the gait parameters in treated PTOA mice demonstrating reduced OA-associated pain. Consistent with the mice data, treatment with JNK inhibitor did not improve human OA cartilage explants.

CONCLUSION

These studies demonstrate that Inf-A, an articular-cartilage resident cell population, contributes to pain in OA via secretion of CCL2 and 7 and can be targeted via inhibition of Jnk signaling.