Study Of New Hydrogels Therapy On Promoting Skin Wound Reepithelialization Of Deep ?° Burns In Rats

Objective:To investigate the effect of topical application of new hydrogels on deep second degree scald wound healing and its possible mechanism of re-epithelialization.Methods:A total of 80 SD rats were randomly divided into 4 groups:normal control group?n=20?,model group?untreated after deep II degree burn in rat skin,n=20?,comfeel hydrogel group?topical application of comfeel hydrogel after deep II degree burn in rat skin,n=20?,new hydrogel group?local application of new hydrogel after deep II degree burn in rat skin,n=20?,and medication?including topical application of comfeel hydrogel and new hydrogel?was used one time per day till the day before drawing tissues.After treatment,the changes of wounds were observed daily,and the wound healing rate of each group was observed every 3 days and the full healing time was recorded.The wounds were also cut off on the 3rd,7th,14th and 21st days after the treatment for histological grading of HE staining and wound healing;integrin?1 and keratin 14?K14?expression analyzed by immunohistochemical staining to ESCs;PCNA was also analyzed by immunohistochemistry to observe the proliferation of cells;Masson staining were performed to study the collagen fibers expression;fluorescence quantitative PCR?qPCR?was used to detect the mRNA expression of KGF,IL-1,IL-6,IL-10,TGF-?,EGF,VEGF,HIF-1?,integrin?3 and integrin?1 in wound tissues.Results:After the scald model was established,the scalded skin became pale,slightly swollen and the skin elasticity decreased.Four hours later,the wound showed a little flaky blood stasis,swelling and wound moist.After 2 days,the wound became red,blood stasis,wound wet,swollen,no effusion and suppuration;the wound was reddish brown after 3 days.The wounds in the each group hardened after knot and at the edge of wounds there existed red circles.Part of the new epithelium was visible around the wound after scab,of which the middle covered with granulation tissue,and a small amount of yellowish exudates.On the21st day,the model group did not achieve complete re-epithelialization.There was a small amount of granulation tissue growth in the center of the wound without exudation.The new hydrogel group and the comfeel hydrogel group basically re-epithelized on the 21st day.The time of complete scab removal of the new hydrogel group was faster than that of the comfeel hydrogel group and model group?P<0.05?.As time went on,the wound healing rate of each group increased.Especially,the wound healing rates of the new hydrogel group and comfeel hydrogel group at each time point were higher than those in the model group?P<0.05?,while there was no significant difference in wound healing rate between the new hydrogel group and comfeel hydrogel group at each time point?P>0.05?.HE staining showed that the pathological scores of skin wound repairing in the new hydrogel group on the 7th,14th and21st day were higher than that of in the model group?P<0.05?.Specifically,the pathological score of new hydrogel group on the 21st day was higher than that of the comfeel hydrogel group?P<0.05?.Masson staining showed that the deposition of collagen fibers in each group gradually increased in the whole wound healing process.On the 3rd day after scalding,the amount of collagen in the model group was sparse,whereas the collagen fibers in the new hydrogel group and the comfeel hydrogel group were coarse and arranged disorderly.On the7th day after scalding,the amount of collagen fibers in the new hydrogel group and the comfeel hydrogel group were more than those in the model group?P<0.05?.On the 14th day after scalding,the collagen fibers in the model group were coarse and arranged disorderly.However,the collagen fibers in the new hydrogel group and the comfeel hydrogel group tended to be neater than the model group?P<0.05?.On the 21st day,the collagen fibers of the model group were coarse and arranged disorderly;the collagen fibers of the new hydrogel group and the comfeel hydrogel group were arranged neatly,and the collagen fibers of the new hydrogel group were more than that of the comfeel hydrogel group and the model group?P<0.05?,more close to that of the normal group.Immunohistochemistry revealed that the expression of integrin?1,K14 and PCNA positive cells in each group increased gradually and peaked on the 14th day.The integrin?1,?P<0.05?.On the 21st day,the expression of integrin?1 and the positive rate of PCNA of the new hydrogel decreased which were lower than that of the model group?P<0.05?.The qPCR results suggested the mRNA expression of IL-1,IL-6 and IL-10 in the new hydrogel group and the comfeel hydrogel group were lower than those in the untreated group on the 14^th day;the expression of VEGF and EGF mRNA were higher on the 3^rd day;the mRNA expression of TGF-?,HIF-1?showed a tendency of increasing first and decreasing then;integrin?1 mRNA expression increased significantly,which was highest;integrin?3 mRNA expression was higher on day 3^rd and21th respectively?P<0.05?.Conclusion:The new hydrogels and comfeel hydrogel can shorten the wound healing time and improve the healing quality mainly by promoting the wound epithelization,but the full healing time of deep second-degree scald wounds treated by the new hydrogel are earlier and the effect on sweat glands and other skin appendages repair is superior to that by the comfeel hydrogel.The role of new hydrogels in promoting the re-epithelization of burn wounds is related to promoting the migration and proliferation of ESCs by providing low oxygen and humid environment,promoting the deposition of collagen,reducing the inflammatory response of wounds,increasing the expression of EGF,VEGF,TGF-?,HIF-1?,Integrin?3,and meanwhile increasing the release of Integrin?1 and other mechanisms.