MG53Protects Kidney From Severe Burn Injury In Mouse Model

Internal organs are participants and sustainers of all kinds of life activities. Manyfactors, such as acute ischemia, anoxia and inflammatory factors, could induce multi-tissuedamage in some internal organs after severe burn injury. Tissue damage in some internalorgans has been proved to be responsible for disease aggravation, complicationdevelopment and mortality augmentation. Better prevention and timely rehabilitation andreconstruction for those important internal organs are critical for improving survival andreducing mortality. After the serious scalding, the ischemic injury occurs in the organs andits repair process is not drawing public attention due to the macroscopic invisibility, widerange, multiple involved organs, complex/concealed pathogenesis and ineffectiverepair-promoting measures1. In the past, various measures were always taken targeting at acertain stage of pathogenesis or to alleviate the injury degree, but couldn’t directly act onthe repairing of cells, which couldn’t contribute to the initiative repairing of organs.Therefore, how to accelerate and strengthen the initiative repairing of injured organs havebecome the key to successfully rescue the serious scald patients, to prevent/treat themultiple organ dysfunction syndromes (MODS) and multiple system organ failure (MSOF)at later stage, and also key to improve the rate of successful rescue. It is an importantresearch topic in this field, and is of great theoretic/clinical significance.MG53, a muscle-specific TRIM family protein, is an essential component of the cellmembrane repair machinery. Ma et al reported that rhMG53could be a therapeutic agent forthe treatment of duchenne muscular dystrophy, and potentially other human diseases wheremembrane injuries contribute to the pathogenesis of the disorder. rhMG53proteins canidentify external signals at membrane disruptions and increase membrane resealing incultured muscle and non-muscle cells when applied to the extracellular solution. Animalstudies showed that application of rhMG53through multiple routes (intramuscular,intravenous, or subcutaneous) could improve the membrane repair capacity of skeletalmyocytes, as well as ameliorate muscular dystrophy2. Therefore, it is reasonable to propose that exogenous rhMG53may somehow help thedamaged cell be recovery via repairing the injuried cell membrane in burn model and thusprobably decrease the mortality. Here we will report the possible roles of rhMG53inprevention of internal organ tissue injury and of high mortality in mouse severe burntmodel.Materials and methods:Male BAL b/c mice, weighing between19g and21g, were induced30%of TBSA andthree degrees injury as histologically confirmed.16serious scald mice were randomlydivided into Control Group (bovine serum albumin, BSA) and Treatment Group (MG53),8mice for each group. In the Treatment Group, rhMG53was injected at3mg/kg twice via tailvein at0.5h and6.5h after the scalding2; and in the Control Group, the same dose of BSA asabove was administered at same above dose. The record was made once every6h during48h after the scalding. At48h after the scalding, the mice were sacrificed and the samples,such as the heart, liver, spleen, lung, kidney, stomach, small intestine, colon, skin, muscleand brain, were harvested. All the tissue sections were colored by hematoxylin-eosin (HE),and observed under the microscope. To measure the pathological score,20visual fields ofeach section were randomly selected under the microscope, and score was recorded throughthe semi-quantitative pathological assessment method (Erdogan et al) according to thenecrotic degree of renal tubule. Immunohistochemical staining was performed to observethe KIM-1expression in both control and MG-53treated groups for evaluation of kidneyinjury.Immunohistochemical staining was performed to observe the location of exogenousrhMG53protein injected via tail vein in both group. Severe burn tissues and normalsamples were harvested and PTRF expression in different groups was tested byimmunohistochemistry.Result:1. The change after severe burn injury in mouse modelThe death rate within48h after the scalding was25%and37.5%in the MG53-treatedGroup and BSA-treated Group respectively. The death of the MG53-treated Group after the scalding of48h was lower than that of BSA-treated.After the HE staining, the lesion was not apparently different in the tissues of mouseheart, liver, spleen, lung, stomach, small intestine, colon, skin, muscle and brain betweenMG53-treated Group and BSA-treated Group. In the MG53-treated Group, the epithelialcells of proximal and distal convoluted renal tubules were significantly improved in thecloudy swelling and degeneration, the same did the inflammatory cells of renalmesenchymes in the infiltration, but the renal glomerulus did not significantly change.48hafter the scalding, the semi-quantitative pathological score (Erdogan et al) in theMG53-treated Group was significantly lower than the renal tubule lesion score in theBSA-treated Group (P<0.0001).According to the KIM-1immunohistochemical results, numerous KIM-1+cells werefound in the renal in both groups, but the average optical density score in the MG53-treatedGroup was significantly lower than the BSA-treated Group (P<0.0001).2. The location of exogenous rhMG53in internal organ tissues and the differenceof PTRF expression before and after burnImmunohistochemical staining of MG53in mouse indicate that, numerous endogenousMG53+cells were found in the cardiac/skeletal muscles in both groups; and exogenousrhMG53was mainly distributed in some epithelial cells of renal tubule and someendothelial cells of pulmonary vessels in the MG53-treated Group, but were not found inBSA-treated Group; Also exogenous rhMG53was detected in the vessel wall of smallpulmonary veins in the MG53-treated Group; there were no positive cells in other organs inboth group.According to the PTRF immunohistochemical results, numerous PTRF+cells werefound in the renal in both groups, and there was no distinct difference of the average opticaldensity score in both group(P=0.890). Also, light poor plus cells were found in skin andsmall intestine of severe burn mouse.Conclusion:Animal experiments indicate that after the injection into tail vein, the exogenousrhMG53could selectively arrive at the high-expressed site of PTRF of kidney. Theexogenous rhMG53protein injected via tail vein can reduce the mortality and apparently alleviate histological alteration of renal after the serious mouse scalding. Our data indicatethat the exogenous rhMG53protein protects the kidney through the involvement of localPTRF after severe burn injury.