New strategies for anterior cruciate ligament partial rupture using bone marrow transplantation in rats.

The purpose of this study was to compare anterior cruciate ligament (ACL) regeneration between animal groups subjected to intra-articular injection of fresh whole bone marrow cells (BMCs), cultured mesenchymal stem cells (MSCs), or saline. Partially transected ACLs in Fischer 344/Nslc rats were prepared, followed by injection of BMCs, MSCs, or saline into the articular cavity at 1 week after transection. Donor cells expressing green fluorescent protein were detected in the recipient's transected ACLs at 4 weeks in the BMC and MSC groups, and their ACLs appeared almost normal histologically. Further, there were significantly more mature spindle cells in the BMC group than in the saline group at 4 weeks. Biomechanically, the tensile strength in the BMC group reached near normal levels at 4 weeks after injection. The levels of transforming growth factor-β1 in the ACL tissue and knee joint fluid in the BMC group were increased significantly compared with that of the saline group at 4 weeks as detected by immunohistochemical analysis. In conclusion, intra-articular bone marrow transplantation using fresh whole BMCs is an effective treatment for ACL partial rupture. This therapy is easy to apply in a clinical setting because no culture system is required for collecting MSCs.