Joint degeneration affects millions worldwide, but most treatments only address symptoms rather than the underlying cellular mechanisms driving cartilage destruction. The synovium—the tissue lining joints—becomes hyperactive in osteoarthritis, producing inflammatory compounds that accelerate joint breakdown. Targeting these synovial cells could offer a pathway to slow disease progression rather than merely managing pain.
Melatonin demonstrates potent anti-proliferative effects on fibroblast-like synoviocytes, the key cells responsible for synovial thickening and inflammation. The hormone arrests cell cycle progression by suppressing cyclin D1 and cyclin E1 expression while promoting programmed cell death through Bax upregulation and Bcl-2 downregulation. Additionally, melatonin impairs cellular migration by reducing vimentin expression, potentially limiting the spread of pathological synovial tissue. In rabbit models, melatonin treatment preserved cartilage integrity and reduced subchondral bone changes characteristic of osteoarthritis progression.
This research represents a significant advance in understanding melatonin's joint-protective mechanisms beyond its established role in sleep regulation. While previous studies demonstrated melatonin's cartilage-preserving effects, this work reveals its direct action on synovial hyperplasia—a critical but often overlooked component of osteoarthritis pathology. The dual targeting of both inflammation and cellular proliferation positions melatonin as potentially superior to conventional anti-inflammatory approaches that address only one aspect of joint degeneration. However, the study's reliance on animal models and isolated cell cultures limits immediate clinical translation. The optimal dosing, timing, and delivery methods for human joint protection remain unclear, and long-term safety data for therapeutic melatonin use in joint disease is limited.