Insulin-induced endothelial cell proliferation and viability in stretched murine skin and cell culture [electronic resource] /

by Shrader, Carl D.

We developed a novel in vivo model utilizing acute stretch to investigate endothelial cell (EC) proliferation as a marker of vascular growth in healing SKH1 mouse skin. We also used human umbilical vein endothelial cells (HUVECs) as an in vitro model system to validate postulated tissue insulin-mediated signal transduction pathway(s) using paradigms that would prove lethal in the animal model. Dorsal distally based flaps of skin were stretched for 3 min using linear (skin hook) plus hemispherical load cycling (inflated subcutaneous silicone catheter). Unstretched, wounded skin along the back and sternum served as postoperative controls. Laser Doppler flowmetry demonstrated a three-fold increase in flap perfusion at postoperative day 7. A stretch-induced six-fold increase in EC mitogenesis accompanied enhancements in blood flow and extracorporal wound healing over the sternum. Western blots revealed upregulation / activation of insulin and mitogenic signaling intermediates in stretched skin. Activated insulin and insulin growth factor receptors (pIR/pIGFR), protein kinase B (Akt, pAkt), vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (flk-1) were among the identified stretch-responsive intermediates. These results indicated the benefits of acute stretch are mediated through enhanced vascularity as evidenced by EC mitogenesis and up-regulation / activation of insulin and key angiogenic effectors in dorsal distally based skin flaps. iii