Effects Of Thymosin β4on Deep Partial Thickness Burn Wound Healing In Rats

Objectives：To detect the effects and preliminary mechanisms of topical thymosin β4on healing of deep partial-thickness burn wound in rats and to provide experimentalbasis for the application of thymosin β4treatment of burn wounds.Methods:PartⅠ Effects of different concentration of thymosinβ4on deep partial-thicknessburn wound healing in rats.128weighed240-260g Sprague Dawley (SD) rats were randomly divided into fourgroups: control group, low concentration group, medium concentration group andhigh concentration group with32in each group. All rats were anesthetized with10%chloral hydrate (400mg/kg) by intraperitoneal injection, followed by scalded with hotwater (91degrees for8seconds) on the back of rats to make a partial-thickness burnwound with3.0cm in diameter. The burn wounds of control group rats were treatedwith0.9%saline solution, those of low, medium and high concentration group weretreated with60,120and240mg/L thymosin β4respectively. Each rat was treated atthe0.1ml dose once a day. The sterile gauze bandage was used to tape securely. Thedressing on rats was changed very other day, and the burn wound area was measuredand healing rate was calculated on the7th,14th and21st day after burns. And ratsburn wound tissue blocks was cut for histological observation after they were stainedby HE. HydroxyProline in tissue was measured in different period by akalinehydroplysis. Immunohistochemical stained slip was taken to detect CD34expressionin blood vessel. SPSS18.0statistical package was adopted for completely randomizedanalysis, P＜0.05was considered statistically significant.Part Ⅱ Effects of thymosin β4on expression of VEGF and bFGF in deeppartial-thickness burn wound in rats.Another32SD rats were selected to create two deep partial-thickness burn wounds on each rat back at the same way. The right side wound was arranged as experimentalone, and the left side wound as control one by self contrast. A concentration of120mg/L thymosinβ4(the optimum concentration of thymosinβ4is120mg/Lwhich was verified on Part Ⅰ) was dropped on the experimental group wounds,while0.9%saline solution was dropped on the control group wounds. The woundswere glued tightly with sterile gauze bandage, followed with the treatment. The doseof thymosinβ4was0.1ml for each once a day. The dressing was changed every otherday at the same time for two groups. The wound healing rate was calculated at the7th,14th and21st day. Five rats was sacrificed on each time point, and the tissue ofwounds of two sides were taken for HE staining to observe of the morphologicalchanges. Immunohistolochemical staining was used to detect the basic fibroblastgrowth factor and vascular of endothelial growth factor expression. Their Integraloptical density was measured by Image Pro Plus system, and the wounds healing ratewas calculated according to measured data. Experimental data were analyzed withSPSS18.0. Paired T test was used to detect the difference between groups. P＜0.05was considered statistically significant.Results：PartⅠ Effects of different concentration of thymosin β4on deep partial-thicknessburn wounds healing in rats1.The wound healing rate：The wound healing rate of different concentration ofthymosinβ4groups were higher than control group, which was most obvious inmedium concentration group (120mg/L), the difference among groups wasstatistically significant.2.Wound healing time: Wound healing time of each thymosinβ4group was shorterthan the control group (24.79±1.23days), medium dose group (120mg/L) is themost obvious one among experimental groups with statistical significance.3. Histological observation of tissue: Capillaries, fibroblast and collagen fiber couldbe seen more in each thymosin β4group than in control group, and there were lessinflammatory cells in each thymosin β4group than in control group. The speed of thewounds epithelization of experimental groups were faster than the control group, medium concentration group (120mg/L) is the most obvious one among experimentalgroups with statistical significance.4.HydroxProline content detection: HYP content of experimental groups was higherthan control group on the7th,14th and21st day, there were statistically significantdifference between experimental group and the control group, especially betweenmedium concentration group and the control group on the7th,14th and21st day (P＜0.05).5.CD34positive blood vessel density：It increased in each group and reached to thepeak at the7th day after burn injury. There was statistically significant differencebetween medium concentration group and control group on the7th and14th day afterburns. It decreased on the21st day, and the difference between experimental groupand control group was not statistically significant.Part Ⅱ Effect of thymosin β4on expression of VEGF and bFGF in deeppartial-thickness burn wound in rats.1.Wound healing rate：The difference between thymosin β4group and control grouphad no statistical significance on the7th day after burn injury. Wound healing rate inthymosin β4group was higher than in control group on the14th and21st day afterburn injury, and the difference between the two groups was statistically significant.2.Wound healing time：Wound healing time of thymosin β4group were22.46±0.89days, while control group’s was24.54±1.10days, thymoinβ4group’s wereobviously shorter than of control group. The difference between two groups hadstatistically significance.3.Integral optical density value: The value of bFGF in experimental group was higherthan in control group on the7th and14th day after burn injury, and their paireddifference had statistical significance (P＜0.05). There was no statistical significanceof their paired difference on the3rd and21st day.4.Integral optical density values of VEGF：The values of both groups increased, andtheir paired difference was not statistically significant on the3rd day after burn injury.The experimental group continued to rise, and higher than that in control group (P＜0.05) with statistically significance on the7th and14th day after burn injury. The Integral optical density of experimental group declined on the21st day, the paireddifference of two group was not obvious.Conclusions: Thymosin β4significantly accelerate deep partial-thickness burn woundhealing, which could be related to increase expression of bFGF and VEGF, and to theeffects of cell apoptosis.