Efficacy of bone marrow mononuclear cells to promote bone regeneration compared with isolated CD34+ cells from the same volume of aspirate.

Autologous bone marrow mononuclear cell (BMMNC) transplantation is currently an emerging clinical treatment in the orthopedic as well as cardiovascular fields. It is believed that the therapeutic effect of the BMMNCs is due to neovascularization enhanced by the CD34(+) cells contained therein, which include endothelial progenitor cells. However, isolation of the CD34(+) cell fraction for clinical application has many disadvantages such as cost and invasiveness related to cell mobilization with cytokine. To investigate whether a purification step is in fact necessary for bone regeneration, we separated BMMNCs, CD34(+), and CD34(-) cells from the same initial volume of rabbit bone marrow aspirates. We then transplanted them back into a femoral bone defect of the same rabbit together with atelocollagen gel and basic fibroblast growth factor (bFGF) and evaluated neovascularization and bone regeneration up to 8 weeks after transplantation. The greatest potential for neovascularization and bone regeneration medicated by cells from the same volume of bone marrow aspirate was found in the BMMNC group. Although purified CD34(+) cells might be an ideal cell source, BMMNCs could be a practical and feasible cell source for bone regeneration in present clinical settings with limited cost, availability of materials, and technical issues for transplantation.