LONDON, March 29 - The day may be coming when stem cells help arthritis patients repair their own joints. Cultured adult human periosteal stem cells demonstrate mesenchymal multipotency, suggesting that they may be used to repair tissue and joint damage associated with arthritis, researchers here reported. Upon enzymatic release and culture expansion, cells harvested from the periosteum can "give rise to cartilage and bone," wrote Cosimo De Bari, M.D., Ph.D. and colleagues at King's College London in the April issue of Arthritis & Rheumatism. Moreover, the cells differentiated into chondrocyte, osteoblast, adipocyte and myocyte lineages regardless of donor age. Although...