Perivascular-Cell Derived Oct4 Is Essential For Angiogenesis Following Hindlimb Ischemia

Ischemic vascular diseases such as coronary, carotid, and peripheral artery disease (PAD) require vascular growth and remodeling in order to restore blood flow to ischemic tissue. Human therapeutic studies aimed at promoting neovascularization have been largely unsuccessful in part because these approaches have focused on stimulating endothelial cell (EC) growth without coordinate investment of smooth muscle cells and pericytes (SMC-P) needed for functional blood vessels that are stable and able to regulate perfusion. Thus, there is a critical need to identify mechanisms that mediate perivascular cell coverage during vascular network remodeling, a process that requires perivascular cell detachment, migration, and investment of endothelial tubes. Previous work from the Owens lab demonstrated that the stem cell pluripotency gene Oct4, previously thought to be permanently epigenetically silenced in all somatic cells, is reactivated in SMC within atherosclerotic lesions. SMC specific KO of Oct4 results in marked reductions in the number of SMC within lesions due to failure of cells to migrate out of the media. That is, Oct4 reactivation appears to be critical for SMC migration, at least in the context of atherosclerosis. Therefore, the present study tested the hypothesis that SMC-P reactivation of Oct4 is essential for neovascularization following hindlimb ischemia (HLI), a mouse model of PAD. To test this hypothesis, we used a unique mouse line enabling SMC-P specific tamoxifen-inducible lineage tracing (termed Myh11 eYFP), allowing their tracking following phenotypic switching and loss of identifying genes, combined with SMC-P specific knockout of Oct4. We subjected both Oct4WT and Oct4KO Myh11 eYFP mice to HLI and monitored perfusion recovery via Laser Doppler at days 0, 3, 7, 14, and 21 post-HLI. We found that SMC-P specific KO of Oct4 results in significantly impaired perfusion recovery at days 14 and 21 post-HLI. We harvested hindlimb muscle at day 21 post-HLI and observed that Oct4 KO mice have significantly impaired angiogenesis, but intact arteriogenesis, compared to WT controls. Future studies will investigate Oct4 downstream targets necessary for angiogenesis following HLI.