Wound healing of the ocular surface after surgery and burns

초록

Bone marrow derived stem cells are involved in the pathogenesis of ocular surface diseases such as pterygium and Mooren's ulcers. These cells may also participate in the repair process after surgical injuries or burns on the ocular surface. In an alkali-burned rabbit model, systemically-transplanted mesenchymal stem cells enhance epithelial healing of the injured cornea. In a clinical study, immunohistochemical staining with amniotic membrane applied to the surgical wound after a pterygium excision showed marked expression of endothelial progenitor and mesenchymal stem cells, which support the involvement of bone marrow-derived stem cells in wound healing of the ocular surface. Hypoxia caused by vascular disruption appears to govern stem cell recruitment and retention. In addition to hypoxia, endogenous growth factors, cytokines, and neurohormones are released to enhance the repair process following an injury, thus specifically mobilizing stem cells into the circulation. Among these factors, substance-P (SP), a neuropeptide involved in pain perception, may have a key role in the wound healing process. In a clinical study involving patients who had undergone surgery for pterygiums, we observed that systemic and tear SP levels increased after surgery, which is related to up-regulation of circulating CD34+ mononuclear cells. In an alkali-burned mouse model, SP showed injury-inducible kinetics in the peripheral blood. Likewise, intravenous injections of SP in uninjured mice and rats induced mobilization of CD29+ stromal-like cells with the capacity of multipotent differentiation, which were similar to stromal cells from bone marrow. Both SP injection and transfusion of autologous SP-mobilized CD29+ cells accelerated wound healing and epithelial engraftment in alkali-burned rabbits. An in vitro examination showed that SP stimulated transmigration and proliferation of human bone marrow stromal cells. These findings suggest that bone marrow-derived stem cells may participate in the repair process of the ocular surface, and SP acts as a messenger of injury and a mobilizer of these cells.©2011 Nova Science Publishers, Inc.