Experimental Study Of VAC Reducing Necrosis Of Zone Of Stasis In Burns

Background: Thermal energy causes an immediate, irreversible injury at the burnsite. However, the uninjured area surroudding the burn site become progressively necrosis.The progressive nerosis in burn wound increased the area and depth of the wound, andincreased the morbidity and mortality. It has become one of the unsolved problems in burntreatment. VAC (Vacuum-assisted closure) therapy can produced a pressure lower than theatmosphere at the burn site to promote the recovery of the tissue wound, and the effect ofthe treatment has been admitted. Overseas studies have proved that the VAC therapy canreverse the burn zone of stasis, reducing the area and depth of the burn, but lacking of thestudy of the mechanisms.In the process of the progressive necrosis, the vascularendothelial cell is the main target cell of damage and also the effect cell of the pathologyprogress. The effective protection of the vascular endothelial cell and to avoid the damageis the critical point to reverse zone of stasis. Autophagy is a kind of cellular mechanism tomaintain a stable internal environment by digesting itself, damaged proteins and theorganelles of aging. So, the effect of autophagy in the burn zone of stasis has became animportant part of studies. This topic intends to observe the function and autophagychanges of the vascular endothelial cells in the zone of stasis to explore the mechanism of VAC reversing the progressive necrosis and to provide a theoretical basis for the clinicaltreatment. This experiment included the following four parts:1． The comb brass burn model was built in ratsThe interspace tissue between the comb teeth burned areas taken as the zone of stasis.The experimental animals were randomly devided into VAC Group and control Group.The samples taken from the interspace was stained by HE to measure the necrotic area anddepth. Results shown that the necrotic area and depth in VAC group6hours post burn wassignificantly less than that in control group.2． Detection of NO and ET-1We have separately detected the NO and ET-1levels with nitrate reductase assay andElisa to calculate the ET-1/NO ratio in zone of stasis and observe the effects of VAC onthe functions of vascular endothelial cells. Results showed that the NO levels in VACgroup were significantly higher than that in control group. It reached peak at12hours postburn and still than normal in72hours. In the control group, it reached peak in6hours andbecame lesser than normal in72hours. As contrast to control group, the ET-1levels inzone of stasis in VAC group significantly increased and reached peak in24hours, butdeclined below the normal in48hours. In control group the ET-1levels reached peak in6hours and lesser than the normal in12hours, besides, the ET-1/NO ratio was sustainedhigher, even in72hours later.3． Detection of TM and TM mRNAThe TM and TM mRNA expressions on the endothelial cell of the interspace tissuewere separately detected by immunohistochemistry staining and real-time PCR to analysisthe impact of VAC on the functions of endothelial cells anti-coagulontion andanti-inflammation. Results showed that TM expression quantity in vascular endothelialcell in zone of stasis was positive in VAC group at each time point post burn. In controlgroup turned negative in24hours post burn. In both groups the TM mRNA expressionshowed a downward trend at each time point, but the expresion in VAC group was higherthan that in control group. 4． The expression of LC3and Beclin-1Their expressions were observed by immunohistochemistry staining in order tocompare the differences between the two groups and analysis the impact of VAC on thecell autophagy in zone of stasis. Results showed that the expression of LC3and Beclin-1in zone of stasis in VAC group was lower than that in control group after6h-24h, but washigher than that in control group in48and72hours. The semi-quantitative analysisshwoed that the differences in6hours post burn and subsequent time were stastisticallysignificant.