Exogenous Indian hedgehog antagonist damages intervertebral discs homeostasis in adult mice

Intervertebral disc-intrinsic Hedgehog signaling maintains disc cell phenotypes and prevents disc degeneration through both cell autonomous and non-autonomous mechanisms

Intervertebral disc degeneration is closely related to abnormal phenotypic changes in disc cells. However, the mechanism by which disc cell phenotypes are maintained remains poorly understood. Here, Hedgehog-responsive cells were found to be specifically localized in the inner annulus fibrosus and cartilaginous endplate of postnatal discs, likely activated by Indian Hedgehog. Global inhibition of Hedgehog signaling using a pharmacological inhibitor or Agc1-CreERT2-mediated deletion of Smo in disc cells of juvenile mice led to spontaneous degenerative changes in annulus fibrosus and cartilaginous endplate accompanied by aberrant disc cell differentiation in adult mice. In contrast, Krt19-CreER-mediated deletion of Smo specifically in nucleus pulposus cells led to healthy discs and normal disc cell phenotypes. Similarly, age-related degeneration of nucleus pulposus was accelerated by genetic inactivation of Hedgehog signaling in all disc cells, but not in nucleus pulposus cells. Furthermore, inactivation of Gli2 in disc cells resulted in partial loss of the vertebral growth plate but otherwise healthy discs, whereas deletion of Gli3 in disc cells largely corrected disc defects caused by Smo ablation in mice. Taken together, our findings not only revealed for the first time a direct role of Hedgehog-Gli3 signaling in maintaining homeostasis and cell phenotypes of annuls fibrosus and cartilaginous endplate, but also identified disc-intrinsic Hedgehog signaling as a novel non-cell-autonomous mechanism to regulate nucleus pulposus cell phenotype and protect mice from age-dependent nucleus pulposus degeneration. Thus, targeting Hedgehog signaling may represent a potential therapeutic strategy for the prevention and treatment of intervertebral disc degeneration.

Small molecule inhibitors of osteoarthritis: Current development and future perspective

Osteoarthritis (OA) is one of the common degenerative joint diseases in clinic. It mainly damages articular cartilage, causing pain, swelling and stiffness around joints, and is the main cause of disability of the elderly. Due to the unclear pathogenesis of osteoarthritis and the poor self-healing ability of articular cartilage, the treatment options for this disease are limited. At present, NSAIDs, Glucocorticoid and Duloxetine are the most commonly used treatment choice for osteoarthritis. Although it is somewhat effective, the adverse reactions are frequent and serious. The development of safer and more effective anti-osteoarthritis drugs is essential and urgent. This review summarizes recent advances in the pharmacological treatment of OA, focusing on small molecule inhibitors targeting cartilage remodeling in osteoarthritis as well as the research idea of reducing adverse effects by optimizing the dosage form of traditional drugs for the treatment of osteoarthritis. It should provide a reference for exploration of new potential treatment options.