Abstract 5635: Estradiol Promotes Neural Stem Cell-based Peripheral Nerve Repair by Enhancing Angiogenesis
Background: Neural stem cells (NSCs) have been shown to have the potential to differentiate into endothelial cells (ECs) as well as neuronal cells (NCs). Estradiol (E2) is known to exhibit pro-angiogenic effects on ischemic tissue via EC activation. Based on these prior findings, we hypothesized that E2 could promote the therapeutic potential of NSC xplant for nerve repair via NSC differentiation into ECs and neovascularization.
Methods and Results: NSCs were isolated from the brains of newborn mice. After unilateral sciatic nerve crush injury, mice were randomly assigned to one of 4 groups: E2 (100 μg administered locally in biodegradable gel), Control (C) (vehicle/gel), NSC (105 cells), and combined E2/NSCs. The E2/NSC group exhibited the greatest nerve functional recovery in motor nerve conduction velocity (C: 33.15±5.23, NSC: 46.97±2.62, E2: 45.32±4.75, E2/NSC: 56.02±6.26 m/s), voltage amplitude (C: 2.7±1.48, NSC: 4.42±0.28, E2: 3.23±1.00, E2/NSC: 6.86±1.48 mV) and exercise tolerance (C: 376.8±68.0; NSC: 437.6±124.9; E2: 428.6±118.2; E2/NSC: maximum duration, 600 sec, same as noninjured) and also showed significantly greater intraneural vascularity and blood perfusion (Laser Doppler) (C: 3.23±1.38, NSC: 10.08±1.15, E2: 14.57±3.31, E2/NSC: 28.14±7.03 flux) compared to the other groups (P<0.05). Fluorescent immunohistology analyses showed that when E2 and DiI-labeled NSCs were locally transplanted in injured nerves, double-positive cells (DiI and EC marker CD31) were more frequently observed (E2/NSC: 6.33±1.53, NSC: 1.33±0.57/nerve, p<0.01), suggesting that E2 promoted NSC differentiation into ECs. The effect of E2 on NSC differentiation into the EC-lineage was further investigated in CD31-negative cells selected by FACS; 5.69% of initially CD31-negative NSCs expressed CD31 when cultured with E2 (10−8 M) for 10 days, and blockade of the E2 receptor with ICI blocked CD31 expression (0%) in E2-treated NSCs.
Conclusions: The combination of E2 and NSC transplantation cooperatively improved the functional recovery of injured peripheral nerves, at least in part, by E2 associated NSC differentiation into ECs. These findings provide a novel mechanistic insight not only in NSC biology but also regarding the biological effect of endogenous E2.