Mesenchymal stem cells enhance recovery and repair following ventilator-induced lung injury in the rat

Background Bone-marrow derived mesenchymal stem cells (MSCs) reduce the severity of evolving acute lung injury (ALI), but their ability to repair the injured lung is not clear. A study was undertaken to determine the potential for MSCs to enhance repair after ventilator-induced lung injury (VILI) and elucidate the mechanisms underlying these effects. Methods Anaesthetised rats underwent injurious ventilation which produced severe ALI. Following recovery, they were given an intravenous injection of MSCs (2x10(6) cells) or vehicle immediately and a second dose 24 h later. The extent of recovery following VILI was assessed after 48 h. Subsequent experiments examined the potential for non-stem cells and for the MSC secretome to enhance VILI repair. The contribution of specific MSC-secreted mediators was then examined in a wound healing model. Results MSC therapy enhanced repair following VILI. MSCs enhanced restoration of systemic oxygenation and lung compliance, reduced total lung water, decreased lung inflammation and histological lung injury and restored lung structure. They attenuated alveolar tumour necrosis factor a concentrations while increasing concentrations of interleukin 10. These effects were not seen with non-stem cells (ie, rat fibroblasts). MSC-secreted products also enhanced lung repair and attenuated the inflammatory response following VILI. The beneficial effect of the MSC secretome on repair of pulmonary epithelial wounds was attenuated by prior depletion of keratinocyte growth factor. Conclusion MSC therapy enhances lung repair following VILI via a paracrine mechanism that may be keratinocyte growth factor-dependent.