Dynamic cell fate plasticity and tissue reintegration drive functional adult synovial joint regeneration after complete resection

Adult mammalian synovial joints have limited regenerative capacity, where injuries heal with mechanically inferior fibrotic tissues. Here we developed a unilateral whole-joint resection model in adult zebrafish to advance our understanding of how to stimulate regrowth of native synovial joint tissues. Using a combination of microCT, histological, live imaging, and single-cell RNA sequencing (scRNAseq) approaches after complete removal of all joint tissues, we find de novo regeneration of articular cartilage, ligament, and synovium into a functional joint. Clonal lineage tracing and scRNAseq implicate a multipotent, neural crest-derived population in the adult skeleton as a cell source for these regenerating tissues. Together, our findings reveal latent molecular and cellular programs within the adult skeleton that are deployed to regenerate a complex joint with lubricated articular cartilage. Joint injury and disease are leading causes of disability, with mammalian joints exhibiting poor regenerative capacity. Here the authors showed that after loss of a whole joint, adult zebrafish regenerate de novo articular cartilage, ligament, and synovium into a complex joint organ.