Tendon Organoids Enable Functional Tendon Rejuvenation Through ALKBH5-Dependent RNA Demethylation.

Adult tendon injuries pose a major clinical challenge due to limited self-repair capacity, resulting in suboptimal regeneration. Although tendon stem/progenitor cells (TSPCs) are pivotal for tendon engineering, achieving microstructure and functional regeneration remains challenging. Organoids boost tissue regeneration post-transplantation in multiple organs. however, tendon-specific organoids with stable phenotype and regenerative capacity are still lacking. Since fetal tendons possess strong regenerative capabilities, the construction of fetal-like tendon organoids is crucial for promoting tendon regeneration. In this study, we generated fetal-like tendon organoids (FT organoids) from adult TSPCs using a serum-free 3D culture system that recapitulated the in vivo microenvironment. These organoids exhibited robust phenotypic restoration and enhanced tenogenic potential, with a gene expression profile resembling fetal tendon development. Notably, transplantation experiments demonstrated functional regeneration of organized tendon collagen matrices in vivo. Furthermore, the mRNA demethylase ALKBH5 plays a critical role in activating key regulatory networks for tendon regeneration via the TGF-β signaling pathway. These findings provided compelling evidence that FT organoids represent a promising strategy for tendon collagen microstructure regeneration and highlights their promising clinical translation potential.