This study examined whether synovial regulatory T (Treg) cells are engaged early after joint injury in two mouse models — surgically induced destabilization of the medial meniscus (DMM) and non-invasive ACL rupture — and whether experimental Treg enrichment via IL-2/anti-IL-2 complexes or intraarticular AAV-mediated IL-2 delivery alters local inflammation and posttraumatic osteoarthritis (PTOA) pathology.
Synovial Treg cells rapidly accumulated after joint injury, adopting activation- and tissue-adaptation-associated phenotypes distinct from lymphoid Treg populations. IL-2-mediated Treg enrichment was associated with reduced synovitis, attenuated cartilage degeneration, and partial improvement in load-bearing gait parameters.
All experiments were conducted in mice; translation to human PTOA is uncertain. The study does not establish a direct causal mechanism linking Treg enrichment to cartilage protection. Optimal timing and delivery route for Treg-targeted therapy were not fully defined.
While not yet clinically actionable, these findings suggest that early immune modulation targeting synovial Treg cells after joint injury may be a future therapeutic strategy worth investigating in human PTOA. Clinicians should be aware that post-injury biological processes in the synovium — independent of biomechanical restoration — may drive PTOA progression.
