As the unique cell type in articular cartilage, chondrocyte senescence is a crucial cellular event contributing to osteoarthritis development. Here we show that clathrin-mediated endocytosis and activation of Notch signaling promotes chondrocyte senescence and osteoarthritis development, which is negatively regulated by myosin light chain 3. Myosin light chain 3 (MYL3) protein levels decline sharply in senescent chondrocytes of cartilages from model mice and osteoarthritis (OA) patients. Conditional deletion of Myl3 in chondrocytes significantly promoted, whereas intra-articular injection of adeno-associated virus overexpressing MYL3 delayed, OA progression in male mice. MYL3 deficiency led to enhanced clathrin-mediated endocytosis by promoting the interaction between myosin VI and clathrin, further inducing the internalization of Notch and resulting in activation of Notch signaling in chondrocytes. Pharmacologic blockade of clathrin-mediated endocytosis-Notch signaling prevented MYL3 loss-induced chondrocyte senescence and alleviated OA progression in male mice. Our results establish a previously unknown mechanism essential for cellular senescence and provide a potential therapeutic direction for OA.

Osteoarthritis (OA) is the most common form of arthritic disease, and phenotypic modification of chondrocytes is an important mechanism that contributes to the loss of cartilage homeostasis. This study identified that Fascin actin-bundling protein 1 (FSCN1) plays a pivotal role in regulating chondrocytes phenotype and maintaining cartilage homeostasis. Proteome-wide screening revealed markedly upregulated FSCN1 protein expression in human OA cartilage. FSCN1 accumulation was confirmed in the superficial layer of OA cartilage from humans and mice, primarily in dedifferentiated-like chondrocytes, associated with enhanced actin stress fiber formation and upregulated type I and III collagens. FSCN1-inducible knockout mice exhibited delayed cartilage degeneration following experimental OA surgery. Mechanistically, FSCN1 promoted actin polymerization and disrupted the inhibition of Decorin on TGF-β1, leading to excessive TGF-β1 production and ALK1/Smad1/5 signaling activation, thus, accelerated chondrocyte dedifferentiation. Intra-articular injection of FSCN1-overexpressing adeno-associated virus exacerbated OA progression in mice, which was mitigated by an ALK1 inhibitor. Moreover, FSCN1 inhibitor NP-G2-044 effectively reduced extracellular matrix degradation in OA mice, cultured human OA chondrocytes, and cartilage explants by suppressing ALK1/Smad1/5 signaling. These findings suggest that targeting FSCN1 represents a promising therapeutic approach for OA.

Regenerative medicine is a discipline that studies how to use biological and engineering principles and operation methods to repair and regenerate damaged tissues and organs. Until now, regenerative medicine has focused mainly on the in-depth study of the pathological mechanism of diseases, the further development and application of new drugs, and tissue engineering technology strategies. The emergence of aptamers has supplemented the development methods and types of new drugs and enriched the application elements of tissue engineering technology, injecting new vitality into regenerative medicine. The role and application status of aptamers screened in recent years in various tissue regeneration and repair are reviewed, and the prospects and challenges of aptamer technology are discussed, providing a basis for the design and application of aptamers in long-term transformation.