Outcomes of human umbilical cord blood-derived mesenchymal stem cells in enhancing tendon-graft healing in anterior cruciate ligament reconstruction: an exploratory study

BACKGROUND: The study investigated whether allogeneic human umbilical cord blood-derived MSCs (hUCB-MSCs) could be safely used without treatment-related adverse events, reducing tunnel enlargement, and improve clinical results in human anterior cruciate ligament (ACL) reconstruction. METHODS: Thirty patients were enrolled consecutively. They were divided into three groups by randomization. In the negative control group, ACL reconstruction surgery without additional treatment was performed. In the experimental group, a hUCB-MSC and hyaluronic acid mixture was applied to the tendon-bone interface of the femoral tunnels during ACL reconstruction surgery. In the positive control group, only hyaluronic acid was applied. Finally, 27 patients were analyzed after the exclusion of three patients. The incidence of treatment-related adverse events, clinical outcomes, including second-look arthroscopic findings, and the amount of tunnel enlargement, were evaluated. RESULTS: There were no treatment-related adverse events in the treatment groups. Tunnel enlargement in the experimental group (579.74 ± 389.85 mm(3)) was not significantly different from those in the negative (641.97 ± 455.84 mm(3)) and positive control (421.96 ± 274.83 mm(3)) groups (p = 0.6468). There were no significant differences between the groups in clinical outcomes such as KT-2000 measurement (p = 0.793), pivot shift test (p = 0.9245), International Knee Documentation Committee subjective score (p = 0.9195), Tegner activity level (p = 0.9927), and second-look arthroscopic findings (synovial coverage of the graft, p = 0.7984; condition of the graft, p = 0.8402). CONCLUSIONS: Allogeneic hUCB-MSCs were used safely for ACL reconstruction without treatment-related adverse event in a 2-year follow-up. However, our study did not suggest any evidence to show clinical advantage such as the prevention of tunnel enlargement postoperatively and a decrease in knee laxity or improvement of clinical outcomes. TRIAL REGISTRATION: CRIS, Registration Number: KCT0000917. Registered on 12 November 2013; https://cris.nih.go.kr/cris/index.jsp