Transmembrane Stem Factor Nanodiscs Enhanced Revascularization in a Hind Limb Ischemia Model in Diabetic, Hyperlipidemic Rabbits

Abstract

Therapies to revascularize ischemic tissue have long been a goal for the treatment of vascular disease and other disorders. Therapies using stem cell factor (SCF), also known as a c-Kit ligand, had great promise for treating ischemia for myocardial infarct and stroke, however clinical development for SCF was stopped due to toxic side effects including mast cell activation in patients. We recently developed a novel therapy using a transmembrane form of SCF (tmSCF) delivered in lipid nanodiscs. In previous studies, we demonstrated tmSCF nanodiscs were able to induce revascularization of ischemia limbs in mice and did not activate mast cells. To advance this therapeutic towards clinical application, we tested this therapy in an advanced model of hindlimb ischemia in rabbits with hyperlipidemia and diabetes. This model has therapeutic resistance to angiogenic therapies and maintains long term deficits in recovery from ischemic injury. We treated rabbits with local treatment with tmSCF nanodiscs or control solution delivered locally from an alginate gel delivered into the ischemic limb of the rabbits. After eight weeks, we found significantly higher vascularity in the tmSCF nanodisc-treated group in comparison to alginate treated control as quantified through angiography. Histological analysis also showed a significantly higher number of small and large blood vessels in the ischemic muscles of the tmSCF nanodisc treated group. Importantly, we did not observe inflammation or mast cell activation in the rabbits. Overall, this study supports the therapeutic potential of tmSCF nanodiscs for treating peripheral ischemia.

Loss of c-Kit in Endothelial Cells Protects against Hindlimb Ischemia

“…The association between endothelial progenitor cell mobilization (EPCs—most of them c-Kit+/CD31+ cells derived from the bone marrow), limb ischemia and an improvement in perfusion and neovascularization has been well documented [ 36 , 37 ]. In addition, the delivery of transmembrane SCF in a rabbit hindlimb ischemia model showed an improvement in revascularization, as well as a greater number of vessels in the ischemic foot [ 38 ]; meanwhile, the loss of global c-Kit (using a c-Kit mutant mice), shown by our group and others, impairs limb perfusion, arteriogenesis, and limb function in the mouse model of hindlimb ischemia [ 21 , 36 ]. We believe that the discrepancy between a global mutation of c-Kit showing a negative effect in arteriogenesis and a specific EC c-Kit inactivation revealing a positive effect in arteriogenesis (both studies using the same model of limb ischemia) is related to the specificity of c-Kit inactivation in the endothelial cells in the present study.…”