Z. N. Maan1, D. Duscher1, A. J. Whittam1, G. G. Walmsley1, R. C. Rennert3, M. Januszyk1, M. S. Hu1, L. H. Fischer1, I. N. Vial2, N. Ho1, S. Khong1, E. R. Zielins1, A. J. Whitmore1, M. T. Longaker1, G. C. Gurtner1 1Stanford University,Surgery,Palo Alto, CA, USA 2University Of Pittsburg,Plastic Surgery,Pittsburgh, PA, USA 3University Of California – San Diego,Neurosurgery,San Diego, CA, USA
Introduction: An impaired neovascular response underlies the significant cardiovascular and wound healing complications seen in elderly and diabetic patients. Stromal-derived factor-1 (SDF-1), a cytokine primarily known for inflammatory cell recruitment, is also thought to play a major role in trafficking progenitor cells to ischemic tissue. Recent studies have found that diabetics and the elderly are deficient in SDF-1, suggesting a possible mechanism for their impaired neovascularization and subsequent cardiovascular and wound complications. Utilizing newly developed murine models, we studied the effect of global (gKO) and endothelial cell-specific SDF-1 knockout (eKO) during neovascularization.
Methods: Humanized excisional wounds were created on the dorsum of gKO, eKO and wild type mice. An ischemic skin flap was created on the dorsum of eKO and WT mice. Wounds and flaps were photographed and assessed at regular intervals. Tissue was harvested for histology and qRT-PCR. The excisional wound model was repeated in eKO and WT mice parabiosed to GFP+ reporter mice and FACS and microfluidic single cell analysis was used to assess recruitment of circulating progenitor cells.
Results: The eKO and gKO groups demonstrated similarly impaired wound healing (*p=0.006). eKO wounds had reduced transcription, shown by qRT-PCR, and protein expression, on immunofluorescent staining, of SDF-1 (*p=0.002; *p=0.008), vascular endothelial growth factor (VEGF) (*p<0.05; *p<0.05) and fibroblast growth factor-2 (FGF-2) (*p<0.05; *p=0.006) with decreased vascular density (*p<0.05). eKO mice also had reduced ischemic flap survival (39% v 72%; *p=0.008) associated with decreased vascular density (*p=0.003). WT mice demonstrated increased recruitment of circulating progenitor cells (GFP+, Lin-) to wounds compared to eKO mice (*p<0.001). Single cell analysis identified a specific sub-population of progenitor cells absent in the wounds of eKO mice.
Conclusion: Endothelial cell SDF-1 (eSDF-1) plays a pivotal role in the vascular response, regulating the expression of cytokines responsible for neovascularization, recruiting a specific population of circulating progenitor cells and subsequently increasing vascular density in ischemic tissue.
