Direct transplantation of mesenchymal stem cells into the knee joints of Hartley strain guinea pigs with spontaneous osteoarthritis

Commercially available human MSCs were cultured, labeled with carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), suspended in either PBS or HA, and injected into the knee joints of 7-month-old animals. The control animals were injected with either PBS or HA alone. The animals were sacrificed at 1, 3, and 5 weeks post transplantation, the knee joints harvested, and fluorescent microscopic analysis was performed. Histological and immunohistochemical analysis were performed at 5 weeks post transplantation.At 5 weeks post transplantation, partial cartilage repair was noted in the HA-MSC group but not in the other groups. Examination of CFDA-SE-labeled cells demonstrated migration, differentiation, and proliferation of MSC in the HA-MSC group. There was strong immunostaining for type II collagen around both residual chondrocytes and transplanted MSCs in the OA cartilage.This scaffold-free and technically undemanding technique appears to result in the regeneration of articular cartilage in the spontaneous OA animal model. Although further examination of the long-term effects of transplantation is necessary, the findings suggest that intra-articular injection of HA-MSC mixture is potentially beneficial for OA.Osteoarthritis (OA) of the knee joint is characterized pathologically by degeneration of articular cartilage, sclerosis of the subchondral bone, and marginal osteophyte formation, and is characterized clinically by chronic devastating pain and disability in the elderly. OA is a major public health problem and its prevalence is expected to increase dramatically and rapidly over the next 20 years with an increasingly aged population [1]. Although tibial osteotomy and total knee arthroplasty have been pursued in a large number of patients to eliminate joint pain and improve joint function, the majority of patients with knee OA are managed conservatively with medication and/or physiotherapy. Development of less technically demanding but effective therapies for kne