KIZILKAYAPHOTOS / ISTOCKPHOTO.COM
T.B. Kurth et al., “Functional mesenchymal stem cell niches in the adult knee joint synovium in vivo,” Arthritis and Rheumatism, DOI: 10.1002/art.30234. Free F1000 evaluation
Abnormal cell growth in joints is a hallmark of rheumatoid arthritis, but the origin of these cells was heretofore unknown. Cosimo De Bari of the University of Aberdeen has located adult stem cells in knee joints for the first time through a “meticulous analysis” of the injury and healing process, writes Rik Lories from the Katholieke Universiteit in Leuven, Belgium.
Stem cells cycle slowly until an injury triggers their rapid proliferation to help repair damage, a feature De Bari took advantage of to test for the presence of these cells. After first labeling murine cells that cycle slowly, the researchers injured the animals’ joints and injected the mice with a different marker that would only be incorporated into new, fast-growing cells. Cells containing both markers were suspected to be stem cells.
Using stains specific to different cell types, the researchers identified these double-marked cells as mesenchymal stem cells. However, De Bari found that they had distinct phenotypes based on location in the joint, and “we assume that these multiple populations may have specific functions,” he says.
The researchers tracked the stem cells as they differentiated into cartilage cells. The next step is to study these cells during injury repair and disease, with the hope of one day improving “the ability of the joint to maintain” or even rehabilitate itself, says De Bari, and of developing therapies for arthritis and other joint disorders.