The Role Of Physiological Electric Filed In Diabetic Chronic Wounds

Chronic refractory wounds as one of the complication of diabetes pose an immense health and economic problem, affecting the quality of life of millions of patients globally. Recent research has found that the mechanism of chronic refractory wounds is complicated and no specific treatments for chronic refractory wounds. Electric stimulation is one of the advanced approaches in clinical treatment for chronic refractory wounds, but no standard guideline for this application has been established until now. The efficacy of the electric stimulation is unstable since the lack of understanding of the intrinsic electric field in the diabetic wounds. Aiming to promote the chronic refractory wound healing, the profile of electric signals at the diabetic wounds and its possibility of abnormal electric signals need be clarified. Endogenous electric fields involve in the embryonic development, tissue regeneration and wound healing process. The corneal epithelium actively generates and maintains antrans-epithelial potential (TEP) by the asymmetric distribution of ion channels and active directional pumping of ions between the stroma and tear side. Wounding collapses the local TEP resulting in significant electric potentials and currents between the wound and the surrounding intact epithelium, establishing the cathode at the wound. This electric current from intact tissue to wound center directs cell migration which plays a key role in the process of wound healing. Therefore, to investigate the role of physiological electric filed in diabetic wounds, this dissertation started with the measurement of normal cornea wound current, verified that the electric field could guide cell migration, and then investigated the potential mediated factors induced the chronic refractory wounds by in vitro and ex vivo models. The purpose of the dissertation is to expand further understanding the mechanism of the diabetic wound healing and to provide theoretical basis for the improvement electrical stimulation in the clinical application.To verify the significant role of the electric filed in the wound healing, at first we used vibrating probe to measure the normal cornea wound current and found that the electric current was immediately established and stabilized for several hours. And also with the application of this physiological electric field could direct the cell migration of single cells (human corneal epithelial cells) and also cell sheets (human embryonic stem cells) in an intensity-and time-dependent manner. Asymmetric biphase electric field could also play a role in directional cell migration in human neural stem cells. To some extent, these results provided basis for the proper application of electric stimulation.In the process of wound healing, it is necessary to sense and reponse to some chemical and physical signals which could guide the cell directional migration. On the basis of results of charpter one, electric fields could guide the cell migration, we supposed that the impaired wound healing might be related with the abnormal electric signals. Therefore, the second chapter basically studied electrical signals at the corneal wounds by three different types of diabetes mice and explored its mechanism of action. Vibrating probe was also used to record the corneal wound current in the STZ-induced, high fat diet induced and db/db diabetic mice. The results showed that diabetic corneas produced significantly weaker wound electric signals than the normal cornea. This was confirmed in three independent animal models of diabetes. Spatial measurements illustrated that diabetic cornea wound current at the wound edge but not wound center was significantly weaker than normal. Time-lapse measurements revealed that the electric currents at diabetic corneas lost the normal rising and plateau phases. The abnormal electric signals correlated significantly with impaired wound healing. Immunostaining suggested lower expression of chloride channel 2 and cystic fibrosis transmembrane regulator in diabetic corneal epithelium. Acute high glucose exposure significantly reduced electrotaxis of human corneal epithelial cells in vitro which might futher induce impaired wound healing.In summary, these data demonstrated the vital physiological significance of electric field for guiding the cell migration and found that weaker and unsteady wound electric signals and impaired electrotaxis may contribute to the impaired wound healing in diabetes. The findings of this dissertation put forward a novel direction to improve the clinical application of electrical stimulation in for the diabetic wounds and also provide a new insight into the understanding of the mechanism of impaired wound healing in diabetic patients.