H & E staining of histological sections formed by the implantation of Lentiviral-BMP2 transduced USCs/β-TCP and USCs/β-TCP into the hind limb of athymic mice for six weeks. (a) The USCs/β-TCP induced no bone formation, whereas the Lentiviral-BMP2 transduced USCs/β-TCP resulted in bone formation in the outer surface and inner pore of the implants (b). Scale bar = 50 μm. TCP: β-TCP; FB: fibroblast tissue; NB: new bone; CA: cartilage tissue. B-TCP, β-tricalcium phosphate; BMP2, bone morphogenic proteins 2; USCs, urine-derived stem cells.