Post injury changes in the properties of mesenchymal stem cells derived from human anterior cruciate ligaments

Purpose The anterior cruciate ligament (ACL) rarely heals spontaneously after rupture. Mesenchymal stem cells (MSCs) contribute to healing in various tissues, therefore, they may also have a key role in healing after ACL rupture. The purpose of this study was to investigate the properties of MSCs in ruptured ACLs. Methods Human ACL samples were harvested from patients undergoing primary ACL reconstruction, and samples were classified by the number of days post rupture (phase I <21 days; phase II 21–56 days; phase III 57–139 days phase IV ≥140 days). We evaluated the characteristics of MSCs, such as colony-forming capacity, differentiation potential and cell-surface markers. Results There was a tendency for high colony-forming capacity during phases I and II, which tended to decrease in phase III. Chondrogenic, adipogenic and osteogenic differentiation potential was maintained until phase II but decreased in phase III. Most surface-epitope expression was consistent from phase I to III: positive for CD44, CD73, CD90 and CD105; negative for CD11b, CD19, CD34, CD45 and human leukocyte antigen-D-related (HLA-DR). The presence of these surface markers proved the existence of MSCs in ruptured ACL tissue. Conclusions Our results suggest that colony-forming and differentiation potential decrease over time. It is important to consider changes in properties of MSCs and use ACL tissue in the acute phase of rupture when biological manipulation is required.