Background: Transplantation of adipose-derived regenerative cells (ADRCs) enhances ischemia-induced angiogenesis, but the underlying mechanism remains unknown. Here, we compared the efficacy of ADRC transplantation with bone marrow mononuclear cell (BM-MNC) treatment using a hindlimb ischemia (HLI) rabbit model, and examined if the anti-inflammatory phenotypic polarization of macrophages regulates postnatal neovascularization.
Methods and Results: ADRCs and BM-MNCs were isolated from New Zealand White (NZW) rabbits and C57BL/6J mice. In the rabbit studies, ADRCs were incorporated into the existing vascular formation in vitro and in vivo. ADRC-conditioned media (CM) and BM-MNC-CM similarly enhanced the migratory ability and prevented apoptosis induction in human umbilical vein endothelial cells. Four weeks after treatment, NZW rabbits administered with either ADRCs or BM-MNCs revealed enhanced collateral vessel formation and functional blood flow recovery. In mice, lipopolysaccharide and/or hypoxic stress increased the level of prostaglandin E2 (PGE2), and led to the polarization of M2 macrophages in cultured ADRCs. Gene expressions of several angiogenic cytokines were amplified in macrophages cultured in ADRC-CM rather than BM-MNC-CM. The expression of interleukin (IL)-10 was increased in ischemic muscles of mice treated with ADRCs compared with those from BM-MNC- treated and control groups. The blockade of IL-10 using a neutralizing antibody attenuated ischemia-induced angiogenesis in vivo.
Conclusions: The therapeutic angiogenesis potential of ADRCs was comparable with those of BM-MNCs in healthy animals. Anti-inflammatory phenotypic polarization of macrophages plays an important role in the regenerative action of ADRCs through the PGE2-EP2/4 axis.