Experimental Study Of Inhibition Of Hypertrophic Scar Formation By Botulinum Toxin Type A In Rabbit Ears

Objective Hypertrophic scar(HS)is a disappointing healing result of abnormal fibrosis resulting in fibroblast and extracellular matrix deposition during skin wound healing,and this pathological proliferation always has serious physical and psychological effects on patients.Botulinum toxin type A(BTXA),a neurotoxin,has been found to inhibit hypertrophic scar formation in recent years and has been widely used in the prevention and treatment of hypertrophic scars,but there is no clear consensus on its specific mechanism of action.Therefore,the aim of this study was to investigate the inhibitory effect of BTXA on the formation of hypertrophic scar in rabbit ears and the related mechanism by injecting different concentrations of BTXA into the acute trauma of rabbit ears at an early stage.Methods Eight healthy New Zealand long-eared rabbits,weighing 2.5-3.5 kg,were maintained in separate cages for 1 week,and four 1-cm diameter wounds were excised from the ventral surface of the rabbit’s ear to establish a rabbit ear hyperplastic scar model.The four wounds were divided into 0U/0.1ml,0.5U/0.1ml,1U/0.1ml,and2U/0.1ml groups in descending order.Samples were collected at 40 days postoperatively,and HE staining was performed to measure the hypertrophic index(HI)to assess the degree of scar proliferation in different groups,Masson staining and measurement of collagen volume fraction(CVF)were performed to assess collagen proliferation in different groups,and immunohistochemistry for Ki67,CD31 and transforming growth factor-beta 1(TGF-β1)was performed to assess the extent of the proliferation of fibroblasts,microvascular proliferation and TGF-β1 expression.Results At the end point of the experiment,all rabbits healed well,and no infection or death cases occurred.HE staining showed that HI decreased significantly with increasing BTXA concentration,and the differences between the groups were statistically significant by post hoc multiple comparisons(p<0.05).The quantitative and qualitative results of Masson staining showed that BTXA inhibited collagen proliferation and improved collagen alignment in the scar,and this inhibition was concentration-dependent,and the differences between groups were statistically significant(p<0.05).By immunohistochemical results,CD31 and TGF-β1 expression levels were found to decrease gradually with increasing treatment concentrations,indicating that BTXA inhibited angiogenesis and TGF-β1 expression in a concentration-dependent manner,and the differences between groups were statistically significant(p<0.05).In Addition to this,the results of Ki67 staining showed that the inhibitory effect of BTXA on fibroblast proliferation increased with the increase of BTXA concentration,but there was no statistically significant difference between the0.5U/0.1ml group and the 0U/0.1ml group(p>0.05).Conclusion Immediate postoperative injection of BTXA can concentration-dependently inhibit the formation of hypertrophic scar in rabbit ear by inhibiting fibroblast proliferation,collagen deposition,vascular proliferation and TGF-β1 expression.Therefore,BTXA had some value in the management of proliferative scar,which is worth further promotion and application.