Stem and progenitor cells in synovium

The synovium is a thin membrane that lines the cavity of synovial joints. It produces the synovial fluid for joint lubrication and cartilage nutrition. The adult synovium contains a heterogeneous population of mesenchymal stromal/stem cells (MSCs). A subset of MSCs in the joint that descends from the embryonic joint interzone naturally repairs articular cartilage defects in mice in vivo. MSCs in synovium are easy to access and attractive in regenerative cell-based therapy for cartilage repair and osteoarthritis via local delivery of exogenous MSCs or via pharmacological targeting of endogenous MSCs in the joint to trigger and enhance repair.