Influence of Botulinum Toxin Type A on Apoptosis of Hypertrophic Scar Tissue in Mice and its Therapeutic Effect

Abstract

Background: Hypertrophic scar (HS) is a disorder characterized by hyperplasia of fibrous tissue during the process of wound healing. During this process, patients suffer from pain, itching and ulceration. There is currently no effective method to inhibit the formation of HS. It is reported that botulinum toxin A (BTX-A) can prevent the excessive proliferation of fibroblasts by regulating apoptosis. The aim of this study was to investigate the therapeutic effects of BTX-A on HS tissue in mice. Methods: An animal model of HS was established and treated with low (1 U/kg), medium (2 U/kg) and high (4 U/kg) doses of BTX-A, respectively. The effects of different doses of BTX-A on the HS tissue and collagen fibers of mice were detected by hematoxylin-eosin (HE) and masson staining. The effects of different doses of BTX-A on the expression of proteins related to the mitogen-activated protein kinase (MAPK) pathway as well as alpha-smooth muscle actin (α-SMA) and Collagen-I were detected by western blot (WB). The effects of different doses of BTX-A on apoptosis were detected by TdT-mediated dUTP nick end labeling (TUNEL). Results: There was no visible bulge at the site of the incision. The wound was healed after 2 weeks, and there was no significant scarring in the control group. In the model group, the HS tissue showed an obvious bulge with significant congestion and was hard in texture. After 2 weeks, the degree of bulge was reduced, and was slightly softer in texture, but still had a certain degree of congestion, as well as significant scarring, altered arrangement of tissue and abnormal accumulation of collagen fibers. As the dose of BTX-A increased, there was a significant reduction in congestion. The scar was softer in texture, the thickness was markedly thinner, the number and density of collagen fibers were reduced and the arrangement of tissue and accumulation of collagen fibers were improved. Compared with the control group, the expression of extracellular signal-regulated kinase (ERK)1/2, p-ERK1, Jun N-terminal kinase (JNK), p-JNK, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), Cleaved-caspase 3, α-SMA and Collagen-I was increased in the model group (p < 0.05). With the increased dose of BTX-A, the expressions of p-ERK1, Bcl-2, α-SMA and Collagen-I were reduced and p-JNK, Bax and Cleaved-caspase 3 were increased (p < 0.05). Conclusion: BTX-A inhibited the formation of HS in mice by inhibiting the activation of the JNK/ERK pathway, promoting the level of apoptosis in HS tissue, reducing the formation of myofibroblasts and deposition of collagen, down-regulating the expression of α-SMA and Collagen-I as well as improving the disordered arrangement of collagen fibers.