Research progress of stem cell-derived exosomes in injury repair

After organ and tissue injury,the proliferation and differentiation of stem cells themselves play only a small role in the repair of injury,and their repair role is mainly played through the paracrine function of stem cells.Exosomes are nano-scale vesicles that are secreted into the extracellular space in an exocytic manner,and its own function will be regulated after the target cells absorb the exosomes.Stem cell-derived exosomes communicate between cells by transmitting proteins,lipids and micro-RNAs(miRNAs).The targeting and biological properties of stem cell-derived exosomes are determined by the level of miRNAs that they carry.After the exosomes reach the target cells and undergo fusion,the gene expression of the target cells is changed by degradation and expression.In addition,the RNA and protein of stem cell-derived exosomes can also limit the development of injury through cell homing.This article will review the mechanism of stem cell-derived exosomes in wound healing,joint injury,fracture healing and cardiac injury.

Study on the mechanism of microporous sheep ADM combined with hUCMSC in promoting wound healing

Objective:To explore the therapeutic mechanism of microporous sheep acellular dermal matrix(ADM)combined with human umbilical cord mesenchymal stem cell(hUCMSC)to promote the healing of full-thickness skin defect.Methods:hUCMSC was co-cultured on microporous sheep ADM to form composite biological dressings.Seventy-two nude mice were selected to make full-thickness skin injury models and randomly divided into 3 groups(hUCMSC+microporous sheep ADM group,sheep ADM group and iodophor gauze group),with 24 mice in each group.The wound healing rate of each group was detected at 14 d,21 d and 28 d after operation,qRT-PCR technique was used to detect the expression of Bax and Bcl-2 in the wound tissues,and the immunohistochemical staining technique was used to detect the expression of Collagen I and vascular endothelial growth factor(VEGF).Data were analyzed with one-way ANOVA and t test.Results:At 14 d after operation,the wound healing rate of the hUCMSC+microporous sheep ADM group was(65.34±14.72)%,which was significantly higher than that of the iodophor gauze group[(37.54±10.21)%],and higher than that of the sheep ADM group[(49.08±11.16)%],the differences were statistically significant(t=19.52,14.72;p<.05).With the gradual healing of the wound,at 28 d after operation,the wound healing rate of the hUCMSC+microporous sheep ADM group was(98.63±15.41)%,which was significantly higher than that of the iodophor gauze group[(81.74±16.27)%],and higher than that of the sheep ADM group[(63.47±14.80)%],the differences were statistically significant(t=-16.42,20.35;p<.05).The expression of Bax in the wound tissues of the hUCMSC+microporous sheep ADM group was significantly reduced,especially at 21 d after operation,the expression level was 0.25±0.06,which was significantly lower than the iodophor gauze group(0.53±0.16)and the sheep ADM group(0.41±0.12),the differences were statistically significant(t=3.52,-2.83;p<.05).The expression of Bcl-2 in the wound tissues of the hUCMSC+microporous sheep ADM group was significantly higher than those of the other two groups,especially at 21 d after operation,the expression level was 0.63±0.19,which was significantly higher than the iodophor gauze group(0.34±0.09)and the sheep ADM group(0.46±0.13),the differences were statistically significant(t=5.31,-6.07;p<.05).Immunohistochemical detection showed that the expression of Collagen I and VEGF in the hUCMSC+microporous sheep ADM group was slightly more than that of the sheep ADM group and the iodophor gauze group,but the effect was not remarkable.Conclusions:hUCMSC+microporous sheep ADM composite dressing can promote the healing of the full-thickness skin injury and reduce the production of apoptotic cells by carrying hUCMSC.

Experimental study on the protective effect of ulinastatin on lung tissue in rats with severe scalded

Objective:To explore the potential protective effects of ulinastatin on ventilation-induced lung injuries of severe burned rats.Methods:Ninety Wistar rats were randomly divided into three experimental groups:the control group(n=30),the ventilation group(n=30)and the ventilation-ulinastatin group(n=30).After establishing the severe burn model,the rats of latter two groups were mechanically ventilated for 1 hour with or without the pre-treatment of ulinastatin.After severe scald,the protective effect of ulinastatin on lung injury caused by mechanical ventilation was estimated through the observation of the tissues samples,and evaluation of the pathological changes of lung tissue by HE staining,ultrastructure change by electron microscopy,lung coefficient,and the expression levels of lung tissue cytokines TNF-α,IFN-γ,IL-2 by immunohistochemical staining.Results:Edema in lung tissues of the control group and the ventilation group was obvious,the hemorrhagic focus could be seen,and the cut surface was observed to be scattered and swelling;Edema in lung tissues of the ventilation-ulinastatin group was mild.HE staining revealed that the pathological changes of the ventilation-ulinastatin group were milder than the ventilation group.Under the electron microscope,the lung tissue organelles of the control group and the ventilation group were seriously damaged;the corresponding changes in the ventilation-ulinastatin group were lighter.The lung coefficient of the ventilation-ulinastatin group was significantly lower than that in the ventilation group.The immunohistochemical results showed that the intensity of TNF-α,IL-2 and IFN-γin lung tissue of the ventilation-ulinastatin group was significantly lower than that in the ventilation group.Conclusions:Ulinastatin has protective effects on lung injury caused by mechanical ventilation in severe scalded rats,whose mechanism may be related to the capacity of ulinastatin to reduce the expression of cytokines including TNF-α,IL-2 and IFN-γ.