Endothelial Progenitor Cell Adhesion Mediated by α4β1 and α5β1 Integrins is Critical to the Restoration of Lung Vascular Endothelial Barrier Function in a Model of Endotoxin‐induced Acute Lung Injury

Abstract

Here we tested the hypothesis that integrin‐mediated adhesion event is a critical requirement for the endothelial barrier protection induced by endothelial progenitor cells (EPCs). We used bone‐marrow (BM)‐derived mononuclear (MNCs) as a source for EPCs, and characterized for EPC marker expression including CD34, VE‐cadherin, Flk1, and integrins. To model Acute Lung Injury (ALI), the recipient mice were γ‐irradiated then challenged intraperitonially with bacterial endotoxin Lipopolysaccharide (LPS). Mice were administered with either control endothelial cells (ECs), EPCs, EPCs incubated with adhesion blocking anti‐integrin monoclonal antibodies, or EPCs transduced with specific shRNA integrin construct. The end points assessed were: (a) survival, (b) lung water content, (c) capillary filtration coefficient (Kfc), (d) H&E staining of lung sections, and (e) confocal image analysis of EPC retention. We found that treatment with EPCs afforded 50% survival (P<0.001) and restored lung fluid balance (Kfc, P<0.001) in α4 and α5 integrins‐dependent manner. Confocal image analyses showed increased retention of Red Fluorescent Protein (RFP)‐tagged EPCs until 8 weeks and overall improved lung morphology. Thus, the treatment with EPCs reduced the extent of LPS‐induced lung microvessel injury, restored lung fluid balance, and increased survival in α4β1 and α5β1 integrins dependent manner.