[Reparative osteogenesis after transplantation of bone marrow multipotent stromal cells cultivated at various oxygen...

Comparative histological and morphometric methods were used to study the bone callus (BC) in rats 14 and 30 days after the experimental fibula fracture. Animals were infused with cell preparations of multipotent bone marrow stromal cells--BMSC (also known as multipotent mesenchymal stromal cells) in the site of injury immediately after the fracture. BMSC were cultivated in vitro under normoxic (20% O2) and hypoxic (5% O2) conditions. 14 days after the fracture, in rats that received no BMSC (control group) and in animals injected with BMSC, newly formed BC contained fibrous tissue, cartilage and reticulofibrous bone tissue (RFBT). The portion of BC, occupied by RFBT was significantly greater in rats that received BMSC grown at 5% O2, than in the other experimental groups. Thickening index of BC at day 14 was 1.3 and 1.4 times higher in animals treated with BMSC grown at 5% and 20% O2 (p < 0.05) than in rats that received no BMSC. At day 30, BC was histologically more mature in rats that received BMSC infusion than in the control group, while the restoration of the initial bone thickness was also more effective in these animals. Thus, the results of this study demonstrated that the infusion of allogeneic BMSC, expanded in vitro at different oxygen concentrations, into the site of fracture improved osteocartilaginous fragment and BC formation and bone size restoration in rats with fibula fracture.