ABSTRACT:We compared the effect of syngeneic and allogeneic transplantation of synovial mesenchymal stem cells (MSCs) for meniscus regeneration in a rat model. Synovium was harvested from the knee joints of three strains of rats. The anterior half of the medial meniscus in both knees of F344 rats was removed and 5 million synovial MSCs derived from F344 (syngeneic transplantation), Lewis (minor mismatched transplantation), and ACI (major mismatched transplantation) were injected into the knee of the F344 rats. At 4 weeks, the area of the regenerated meniscus in the F344 group was significantly larger than that in the ACI group. Histological score was significantly better in the F344 and Lewis groups than in the ACI group at 8 weeks. DiI labeled cells could be observed in the knee joint in the F344 group, but were hardly detected in the ACI group at 1 week. The number of macrophages and CD8 T cells at synovium around the meniscus defect was significantly lower in the F344 group than in the ACI group at 1 week. Syngeneic and minor mismatched transplantation of synovial MSCs promoted meniscus regeneration better than major mismatched transplantation in a rat meniscectmized model. The meniscus is a fibrocartilage whose functions are to increase surface contact area, to absorb mechanical loads, and to improve stability across the knee joint. Meniscal injury is one of the most common injuries of the knee joint, primarily due to sports injuries or degenerative conditions. For injured menisci, efforts have been made to preserve the meniscus as much as possible to prevent degenerative arthritis. For meniscal defects after meniscectomy or meniscal degeneration, transplantations of meniscal grafts or artificial menisci have been attempted; however, the invasiveness, durability and safety of the transplant remain controversial.1 Therefore, a novel strategy for meniscus regeneration is required.Mesenchymal stem cells (MSCs), especially those derived from synovium, are an attractive cell source for meniscus regeneration, because synovial MSCs have remarkable proliferation 2 and chondrogenic potential.3-5 We previously reported that intraarticular injection of synovial MSCs promoted meniscal regeneration in a rat model. 6 It was a syngeneic transplantation model; therefore, possible immune reactions seem to be negligible.
MSCs have potent anti-inflammatory/immunosuppressive properties.7 This suggests that allogeneic MSCs can be used therapeutically with equal efficacy to autologous MSCs without triggering the donor specific immune responses. However, this is still controversial, and the opposite results were also reported. [8][9][10] In regard to synovial MSCs, the influence of allogeneic transplantation has not been investigated at all. In this study, we compared the effect of syngeneic and allogeneic transplantation of synovial MSCs for meniscus regeneration in a rat model. For allogeneic transplantations, major antigen mismatched and minor antigen mismatched MSCs were also prepared.
MATERIALS AND METHODS
AnimalsThis study w...