The PIEZO1/miR-155-5p/GDF6/SMAD2/3 signaling axis is involved in inducing the occurrence and progression of osteoarthritis under excessive mechanical stress.

OBJECTIVE: To elucidate the molecular mechanism of overloading-induced osteoarthritis (OA) and to find a novel therapeutic target. METHODS: We utilized human cartilage specimens, mouse chondrocytes, a destabilization of the medial meniscus (DMM) mouse model, and a mouse hindlimb weight-bearing model to validate the role of overloading on chondrocyte senescence and OA development. Then, we observed the effect of PIEZO1-miR-155-5p-GDF6-SMAD2/3 signaling axis on the preservation of joint metabolic homeostasis under overloading in vivo, in vitro and ex vivo by qPCR, Western blot, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, immunofluorescence, SA-ß-gal staining, CCK8 assay, et al. Finally, we verified the therapeutic effects of intra-articular injection of miR-155-5p inhibitor or recombinant GDF6 on the murine overloading-induced OA models. RESULTS: Chondrocytes sensesed the mechanical overloading through PIEZO1 and up-regulated miR-155-5p expression. MiR-155-5p mimics could copy the effects of overloading-induced chondrocyte senescence and OA. Additionally, miR-155-5p could suppress the mRNA expression of Gdf6-Smad2/3 in various tissues within the joint. Overloading could disrupt joint metabolic homeostasis by downregulating the expression of anabolism indicators and upregulating the expression of catabolism indicators in the chondrocytes and synoviocytes, while miR-155-5p inhibition or GDF6 supplementation could exert an antagonistic effect by preserving the joint homeostasis. Finally, in the in vivo overloading models, intra-articular injection of miR-155-5p inhibitor or recombinant GDF6 could significantly mitigate the severity of impending OA and lessened the progression of existing OA. CONCLUSION: GDF6 overexpression or miR-155-5p inhibition could attenuate overloading-induced chondrocyte senescence and OA through the PIEZO1-miR-155-5p-GDF6-SMAD2/3 signaling pathway. Our study provides a new therapeutic target for the treatment of overloading-induced OA.

Growth differentiation factor-6 attenuates inflammatory and pain-related factors and degenerated disc-induced pain behaviors in rat model.

Previous studies have indicated that growth differentiation factor 6 (GDF6) is a potential candidate for intervertebral disc (IVD) degeneration (IDD) treatment. Here, we investigated the effect of GDF6 on IDD by examining changes in disc structure and the expression of inflammatory and pain-related factors. A rat posterior disc puncture model of single segments and three consecutive segments was constructed, and GDF6 or phosphate-buffered solution was administered via intradiscal injection 1 or 2 weeks after surgery. Magnetic resonance imaging showed a clear degeneration signal in the punctured disc, which was inhibited by GDF6. Histological staining revealed that GDF6 did not significantly improve the structure of IVDs in rats 8 weeks after puncture surgery, but it had an inhibitory effect on expression of the tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-1ß in the IVD. Furthermore, GDF6 was found to protect the morphology and structure of the IVD 32 weeks after surgery. Mechanical and thermal hyperalgesia tests suggested that GDF6 injection can significantly improve mechanical and thermal-stimulated pain behavior in rats and inhibit the expression of inflammatory factors TNF-α and IL-1ß and the pain factor calcitonin gene-related peptide in the dorsal root ganglion. A rat protein array test indicated that GDF6 could reduce the expression of cytokines IL-6, intercellular cell adhesion molecule-1, matrix metalloproteinase-13, IL-1ß, and TNF-α and increase the expression of tissue inhibitor of metalloproteinases 1, Transforming growth factor-beta 2, IL-10, and resistin in a TNF-α-induced IDD cell model. Thus, our study demonstrates that GDF6 can improve the structure of the IVD, inhibit the expression of inflammatory and pain-related factors, and improve pain behavior in rats. Clinical Significance: To establish further preclinical research and clinical trials, comprehensive data are needed to validate the regenerative properties of GDF6. Ideally, a regenerative agent should also be able to relieve discogenic pain, achieving the best clinical outcomes.

Treatment with rhBMP12 or rhBMP13 increase the rate and the quality of rat Achilles tendon repair.

Tendon injuries that result in partial or complete tears often come from chronic, repetitive use, or from sudden trauma. In some cases, torn tendons can be repaired, but such repairs often fail to completely restore tendon function. We used global gene expression profiling and histological examination to study tendon repair to elucidate key molecular processes that regulate the rate and quality of tissue restoration. Using a rat Achilles tendon transection model, tissue was collected at 3, 7, 10, and 15 days postinjury. The pattern of gene expression in the repairing tissue paralleled the healing phases of inflammation, matrix formation, and matrix reorganization. Newly formed repaired tissue is characterized by cells expressing many genes associated with tendon formation, thereby potentially distinguishing this repair tissue from other types of repair or scar tissue. Addition of recombinant human bone morphogenic protein (rhBMP)12 or rhBMP13, also known as growth and differentiation factors (GDFs) 6 and 7, 1 day after injury yielded increases in tissue volume, rate of cellular infiltration, and in changes in levels of key mRNAs involved in tendon repair. Altogether, our results indicate that rhBMP12 or rhBMP13 enhance the rate of tendon repair. A better understanding of the key molecular regulators of tendon repair could lead to the development of new therapies for tendon injuries and the identification of diagnostic markers that indicate the status of tendon repair after injury.

BMP13 prevents the effects of annular injury in an ovine model.

Chronic back pain is a global health problem affecting millions of people worldwide and carries significant economic and social morbidities. Intervertebral disc damage and degeneration is a major cause of back pain, characterised by histological and biochemical changes that have been well documented in animal models. Recently there has been intense interest in early intervention in disc degeneration using growth factors or stem cell transplantation, to replenish the diseased tissues. Bone Morphogenetic Proteins (BMPs) have been approved for clinical use in augmenting spinal fusions, and may represent candidate molecules for intervertebral disc regeneration. BMP13 has an important role in embryonic development and recent genetic evidence shows a role in the development of the human spine. This study explores the effect of BMP13 on a damaged intervertebral disc in an ovine model of discal degeneration. We found that, when injected at the time of injury, BMP13 reversed or arrested histological changes that occurred in the control discs such as loss of extracellular matrix proteins. In addition, BMP13 injected discs retained greater hydration after 4 months, and possessed more cells in the NP. Taken together, BMP13 may be a potent clinical therapeutic agent when used early in the degeneration cascade to promote healthy disc tissue.