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Background: Mesenchymal stem cells (MSCs) transplantation therapy is considered an alternative therapy to prevent posttraumatic osteoarthritis (PTOA). However, consensus as to the sufficient number of MSCs for the prevention of PTOA is lacking. The purpose of this study was to determine the sufficient number of MSCs to achieve PTOA prevention and the reduction in pain after anterior cruciate ligament transection (ACLT).Methods: Eight-week-old male Wistar rats were used. ACLT was conducted in the knee joint as a PTOA model. According to the species-specific knee joint volume, 104 MSCs in rats are equivalent to 3 × 107 MSCs in humans, which was clinically prepared. MSCs (104, 105, or 106 cells) or phosphate-buffered saline were injected into the knee joint at 1, 2, and 3 weeks after ACLT. Histological examinations were performed at 12 weeks after ACLT. The weight-bearing distribution improvement ratio was calculated as an assessment of pain until 12 weeks after ACLT.Results: Histological evaluations showed that all the MSCs groups except for 104 MSCs group in femur were significantly improved compared to the control group at 12 weeks after ACLT. The weight-bearing distribution in the 104 and 105 MSCs groups at 12 weeks after ACLT and in the 106 MSCs group at 6, 8, 10, and 12 weeks after ACLT were significantly higher than those of the control group.Conclusion: A clinically feasible number of MSCs was found to reduce the articular cartilage degeneration and to decrease pain in the PTOA model. Increasing numbers of the cells further protected the articular cartilage against degeneration. [ABSTRACT FROM AUTHOR]

Background: The treatment of meniscus injuries combined with anterior cruciate ligament (ACL) reconstruction would be important to improve outcomes after ACL reconstruction. However, the effects of treatment methods for meniscus after ACL reconstruction have not been thoroughly investigated. The objective of this study was to investigate the effects of treatment methods for meniscus on clinical and radiological outcomes at 2 years after ACL reconstruction.Methods: Three-hundred and eighteen patients with primary ACL reconstruction using autologous hamstring tendon registered in our multicenter study database and who were followed up for 2 years were included. They were then divided into 3 groups, the no meniscal lesion/untreated group (n = 149), the meniscal repair group (n = 139), and the meniscal resection group (n = 30). Patient-based subjective evaluations (Lysholm score, Knee injury and Osteoarthritis Outcome score and International Knee Documentation Committee subjective score), objective evaluations (Lachman test, pivot shift test and KT measurement), and radiological measurements (medial and lateral joint space width) were compared among the 3 groups preoperatively and at 2 years follow-up.Results: All subjective scores and objective evaluations significantly improved in all groups without significant differences among the groups postoperatively. Regarding radiological findings, the medial joint space width significantly decreased only in the resection group during the 2-year period, and the medial joint space width in the resection group was significantly smaller than that of the other groups at the 2-year follow-up. Moreover, the medial joint space width significantly decreased during the 2-year period when MM was resected.Conclusions: In radiological findings, medial meniscus resection decreased medial joint space width two years after ACL reconstruction. On the other hand, treatment methods for meniscus neither significantly affected subjective nor objective findings until the 2-year follow-up.Level Of Evidence: Ⅱ, Cohort study. [ABSTRACT FROM AUTHOR]