Differential promotion of angiogenesis by distinct bone marrow cell subpopulations

Abstract

Abstract Introduction: Bone marrow mononuclear cells (BMMC) have the capacity to differentiate into endothelial cells and promote neovascularization in hindlimb ischemia. However, the specific bone marrow cell population that promotes revascularization is unknown. Therefore, we determined the ability of unfractionated BMMC, CD34+ and CD34− from bone marrow to promote angiogenesis in an in-vivo murine model. Methods: BMMC were obtained from total bone marrow harvested from C57Bl/6 mice. CD34+ and CD34− subpopulations were isolated using magnetic bead separation. 1cc Matrigel was admixed with either unfractionated BMMC or CD34+ or CD34− cells was injected subcutaneously. Matrigel +/− VEGF (500ng/cc) was injected as positive and negative controls. Matrigel implants were harvested 14 days later and were analyzed by immunohistochemistry with determination of CD31+ and smooth-muscle actin (SMA) positive areas by morphometry. Results: No angiogenesis was observed in plain Matrigel. All implants seeded with bone-marrow-derived cells promoted neovessel formation in a dose-dependent manner. Unfractionated BMMC promoted formation of neovessels containing both CD31+ and SMA + cells. CD31+ area was greatest in implants seeded with CD34+ cells. In contrast, SMA+ area was greatest in implants containing CD34− cells, which promoted development of larger SMA-containing vessels. Conclusions: BMMC are capable of promoting angiogenesis in an in-vivo Matrigel model in a dose-dependent manner. CD34+ bone marrow cells are most capable of promoting endothelial development. In contrast, the CD34− subpopulation promotes development of larger arteries containing vascular SMA. These results have important implications for the development of cell-based therapies for limb ischemia.