Interaction of sheep bone marrow stromal cells with biodegradable polyurethane bone substitutes

Summary: Autogenous cancellous bone graft is often used in clinical practice to promote bone healing in large, critical-size defects. Bone harvesting has numerous drawbacks which calls for new alternatives. Potentially, an alternative to bone grafting may be offered by a tissue engineering approach that utilizes a suitable scaffold seeded with osteogenic cells. In this study the interaction of sheep bone marrow stromal cells with biodegradable microporous polyurethane scaffolds designed as bone substitutes was investigated. The scaffolds were produced from the same polyurethane but had two different pore sizes in the ranges of 140–400 µm and 200–600 µm. The scaffolds were impregnated with platelet-rich plasma or fibrin to evaluate whether impregnation affects cell attachment, growth and proliferation. It has been found that scaffolds promote attachment, differentiation and proliferation of sheep bone marrow stromal cells. The cells adhered well to the scaffold's surface and infiltrated its porous structure. The DNA content and the mRNA expression increased with time of culture. Histological and immunohistochemical stainings showed that the cells were viable and differentiated into osteoblasts. There was an evident effect of the scaffolds' pore size on cell attachment and proliferation. Cell growth was more efficient in the scaffolds with smaller pore sizes than in the scaffolds with larger pores. Scaffolds with larger pores underwent calcification. No calcium was found in the scaffolds with smaller pore sizes. The pore size had no effect on cell morphology. The stromal cells differentiated into osteoblasts, which process was more pronounced in the scaffolds with larger pores. Impregnation of the scaffolds with fibrin or platelet-rich plasma facilitated cell growth and proliferation. This effect was more pronounced for scaffolds impregnated with platelet-rich plasma than for scaffolds impregnated with fibrin.