Abstract
Proangiogenic cells (PACs) display surface markers and secrete angiogenic factors similar to those used by myelomonocytic cells, but, unlike myelomonocytic cells, PACs enhance neovascularization activity in experimental ischemic diseases. This study was performed to reveal the differential neovascularization activities of PACs compared with those of myelomonocytic cells. We cultured PACs and CD14(+)-derived macrophages (Macs) for 7 days. Most of the surface markers and cytokines in the two cell types were alike; the exceptions were KDR, β8 integrin, interleukin-8 and monocyte chemotactic protein-1. Unlike Macs, PACs significantly enhanced mesenchymal stem cell (MSC) transmigration. PACs and Macs increased neovascularization activity in an in vitro co-culture of human umbilical vein endothelial cells and MSCs and in an in vivo cotransplantation in Matrigel. However, the use of Macs resulted in inappropriately dilated and leaky vessels, whereas the use of PACs did not. We induced critical hindlimb ischemia in nude mice, and then transplanted PACs, Macs or vehicle into the mice. We obtained laser Doppler perfusion images weekly. At 2 weeks, mice treated with PACs showed significantly enhanced perfusion recovery in contrast to those treated with Macs. After day 7, when cells were depleted using a suicidal gene, viral thymidine kinase, to induce apoptosis of the cells in vivo by ganciclovir administration, we found that the improved perfusion was significantly abrogated in the PAC-treated group, whereas perfusion was not changed in the Mac-treated group. PACs caused an increase in healthy new vessels in in vitro and in vivo models of angiogenesis and enhanced long-term functional neovascularization activity in the hindlimb ischemia model, whereas Macs did not. Nevertheless, the angiogenic potential and long-term functional results for a specific cell type should be validated to confirm effectiveness and safety of the cell type for use in therapeutic angiogenesis procedures.