The Effectiveness And Preliminary Mechanism Of Locoregional Thymosin ?4 Gel Injection In The Prevention Of Esophageal Stenosis After Circumferential Endoscopic Submucosal Dissection

Endoscopic submucosal dissection(ESD)is developed on the basis of endoscopic mucosal resection(EMR),which is mainly used for treating benign tumors,early cancer and precancerous lesions of digestive tract.Compared with EMR,the main advantage of ESD is its effectiveness in resecting large-sized lesions in an en bloc fashion.ESD theoretically enables the resection of lesions regardless of their size,shape and severity of fibrosis.If the resection margins have residual cancer cells can be evaluated.Even the ulcerative lesions can also be removed.With the advancement of ESD technology,the larger esophageal lesions,even circumferential esophageal lesions can be completely removed by ESD.However,resection of a wide range of lesions also will be associated with a number of related complications,especially causes esophageal stenosis.We define a standard endoscopy(9.8mm in diameter)that is difficult to pass the esophagus as esophageal stenosis.Esophageal stenosis will cause dysphagia and reduce the quality of life.The possible mechanisms of esophageal stenosis post-ESD mainly include the following aspects: delayed healing of the mucosa,inflammation and fibrosis of a large number of extracellular matrix,and atrophy and destruction of muscularis propria.Currently the common therapies of post-esophageal ESD stricture in clinical are endoscopic balloon dilation and plastic coated stent implantation.However,repeated endoscopic diagnosis and treatment bring patients with the corresponding risks and troubles.Therefore,according to the mechanisms of esophageal stenosis,there are many kinds of prevention strategies,including systemic and local usage of corticosteroids,regenerative medicine approaches and topical anti-inflammatory and anti-fibrosis drugs.These methods acquired a certain effect,but due to safety or cost,are not suitable for wide clinical application.Thymosin beta 4(T?4)composed of 43 amino acids is a water soluble small molecule acidic peptide with highly-conserved chemical construction.T?4 has a variety of biological functions,including promoting angiogenesis,accelerating epithelial cell migration and regulating inflammation,fibrosis and inhibiting scar formation.A number of animal experiments and clinical trials revealed that it can promote the healing of skin,cornea and heart trauma.Therefore,we speculate that T?4 topically applied to the wound after esophageal ESD also can promote the migration of epithelial cells,inhibit inflammation and fibrosis of the wound,consequently promote wound healing and delay the process of esophageal stenosis.This study will evaluate the efficacy and safety of T?4 in the prevention of postoperative stenosis of esophageal circumferential ESD and explore the prevention mechanism preliminarily by animal experiments.This experiment is divided into two parts as follows.Part ?: the effectiveness study of Locoregional T?4 gel injection in the prevention of stricture after CESD of the esophagus.Objective: To evaluate the effect of locoregional T?4 gel injection on the duration of ulcer healing and the No.of required EBD in patients with CESD of esophagus.Methods: 8 pigs were anesthetized before CESD of esophagus.The prevention group of 4 pigs receive locoregional T?4 gel injection into the ulcer base and the junction of normal mucosal after CESD immediately and on day 3.Observe under endoscope on day 7 and then every 1 week.Performance EBD if the esophagus is developed stricture.Control group of the other 4 pigs apply EBD only with esophageal stenosis.The method of dilation of the groups is the same.Operate EBD until the ulcers are completely healed.Results: Both the prevention group and control group developed esophageal stenosis.Compared with the control group,the prevention group shortened the duration(15.25±3.5weeks vs.23.75±3.304 weeks,P=0.012)and reduced the No.of EBD(8.5±2.082 vs.17.25±2.754,P=0.002)required for resolving the stricture.In addition,the prevention group reduced the severity of stricture(P=0.046).There were no serious complications in the 2 groups.Conclusion: Locoregional T?4 gel injection relieves the process of stenosis developed after CESD in a porcine model,which provides a new strategy for preventing esophageal stricture post-CESD.Part ?: Preliminary study on the mechanism of locoregional T?4 gel injection in the prevention of esophageal stenosis after CESD.Objective: To further verify the efficacy of T?4 gel in the prevention of esophageal stricture post-CESD by histological assessment and inflammatory cytokines levels.Methods: 18 pigs were established esophageal CESD model.The prevention group(n=8)were injected T?4 gel into the ulcer base and the junction of normal mucosal after CESD immediately and on day 3.The control group(n=10)were only performed CESD.All animals underwent clinical and endoscopic observation.Euthanasia was performed at the end of the 14-day study period.Then take out the esophagus and perform histological analysis.Quantitate the expression of inflammatory cytokine levels in serum before CESD(day 0)and on day 7.Results: After 2 weeks,the mean esophageal diameter of the prevention group was significantly wider to that of the control group(3.13±1.126 vs.1.88±0.835,P =0.024).The mean thickness of the esophageal fibrosis was significantly thinner in the prevention group(1.16±0.27 mm vs.1.55±0.31 mm,P=0.018).The mean length of reepithelialization was significantly longer in the prevention group(3.77± 2.25 mm vs.1.59±1.45 mm,P=0.028).The quantitative measurements of serum inflammatory cytokines including IL-4,IL-6,IL-8,IL-12 p70,INF-? and TNF-? were significantly different in the two groups(P<0.001,P=0.001,P=0.03,P=0.014,P=0.019 and P=0.007,respectively).In addition,the reduction in IL-4,IL-12 p70 and TNF-? levels between days 0 and 7 were significantly greater in the prevention group(P<0.001,P=0.001,P=0.006,respectively).Conclusion: Locoregional T?4 gel injection after esophageal CESD reduces inflammation and fibrogenesis,and promotes the proliferation and migration of epithelial cells of wound,consequently relieves the process of esophageal stenosis.According to the above research results,the following conclusions can be drawn:Locoregional T?4 gel injection can alleviate process of the porcine esophageal stenosis post-CESD.It shortens the duration and reduces the No.of EBD required for resolving the stricture,reduces inflammation and fibrogenesis,and promotes the proliferation and migration of epithelial cells of wound.Our study provides a new strategy for the prevention of esophageal stricture post-CESD,and it also provides a new way for the clinical application of T?4 in the future.