Effects of direct ATP delivery to ischemic skeletal muscle.

Skeletal muscle;Ischemia;Fusogenic lipid vesicles;Tissue preservation;Reperfusion

Federico V. Grossi, 1974-

University:University of Louisville

Department:Physiology and Biophysics

关键词: Skeletal muscle;    Ischemia;    Fusogenic lipid vesicles;    Tissue preservation;    Reperfusion;   

Others  :  https://ir.library.louisville.edu/cgi/viewcontent.cgi?article=1538&context=etd

美国|英语

来源: The Universite of Louisville's Institutional Repository

【 摘 要 】

The purpose of this dissertation was to demonstrate that a new method of direct intracellular energy delivery was effective in maintaining viability of in vitro Human Umbilical Vein Endothelial Cells (HUVECs) when exposed to chemical ischemia for prolonged periods of time and in preventing in vivo ischemia reperfusion injury in a composite tissue transplantation model. Ischemia and reperfusion injury is a well recognized phenomenon that occurs in situations like organ transplantation, shock, cardiac surgery, etc, where tissues are temporarily deprived of nutrients and oxygen for energy production. When exposed to short periods of ischemia, cells utilize their stored energy to survive. If ischemia is extended beyond certain limits, cellular energy stores become depleted leading to metabolic and structural changes. One of the effects of this lack of energy is the malfunctioning of the membrane adenosine triphosphate (ATP)-dependent ionic pumps which are ultimately responsible for maintaining cellular volume, intracellular pH and ionic homeostasis. Thus it is hypotesized that the negative effects of energy depletion on cellular homeostasis could be overcome by delivering energy directly into the cell. This method of direct energy delivery into cells is based on fusogenic lipid vesicles (FLVs) composed of lipids very similar to those that form the cellular membrane. These vesicles are very small and when put in contact with cell membranes, rapidly fuse to the cell membrane delivering their content into the cell interior. Making use of this phenomenon, the vesicles are loaded with ATP magnesium chloride (Mg-ATP) that is delivered directly into the cell, providing it with a readily usable form of energy. We hypothesized that, under chemical hypoxia, endothelial cell viability could be preserved and the Na + K +- ATPase pump activity could be maintained by delivering Mg-ATP directly into the cells. Further, we hypothesized that ischemia reperfusion injury due to tissue transplantation could be reduced by perfusing tissues ex vivo before reimplantation with a solution containing Mg-ATP-loaded FLVs. The first two hypotheses were tested in the following manner. First, we determined the optimal concentration of Mg-ATP that the FLVs needed to be loaded with to maintain the viability of HUVECs exposed to 4 hours of chemical hypoxia. Second, we tested if the Na + K + ATPase pump activity could be maintained by delivering Mg-ATP to HUVECs exposed to chemical hypoxia. The results of these experiments demonstrated that direct delivery of Mg-ATP using FLVs was effective in maintaining cell viability and