A Study About The Biomechanical Properties Of PDO-SIS Patch And Its Ability To Repair Abdominal Wall Defect In Rats

Objective :This study aims to synthesize a hybrid patch,which not only has high bioactivity of extracellular matrix materials,but also has high mechanical properties of artificial materials,and can be gradually degraded in vivo.Extracellular matrix materials have been widely used in clinic because of their high biocompatibility and bioactivity,for example: Cook company Surgisis biological patch has been widely used in clinical,and there is no significant difference in hernia recurrence rate compared with artificial patch,and the postoperative complications are less.Porcine small intestinal submucosa(P-SIS)was used as the experimental material for this study.However,it is not possible to maintain the mechanical properties of the extracellular matrix materials,we chose PDO elastic fiber as the artificial material for the synthesis of hybrid patch.PDO elastic fibers are often used in joint surgery because of their superior mechanical properties and shape memory function,the relevant research shows that PDO material in vivo hydrolysis degraded gradually,rid the body through metabolism.In the initial period of time,PDO elastic fibers can maintain strong mechanical properties,and then gradually reduced.The two kinds of materials have certain similarity,which provide biological activity and mechanical properties,they can be used as raw material for the synthesis of hybrid patch.This experiment is divided into two parts: in vitro and in vivo.1.In vitro.The essential information of P-SIS materials will be detected first.Then the lyophilized P-SIS materials were used to construct 8SIS mash by vacuum lamination technique.PDO elastic fiber and lyophilized P-SIS materials were used to construct the hybrid PDO-SIS patch by weaving and vacuum lamination technique.The mechanical properties of the two types of mash were measured.2.In vivo.To investigate whether there are differences between PDO-SIS hybrid mash and 8SIS mash in the repair of SD rat abdominal wall partial defects.The host response to the two kinds of patch will be studied in deeply.Method:1.P-SIS preparation and tested:(1)The fat?blood vessels?muscle and mucosa in the jejunum were scraped away by hand.(2)In accordance with the Abraham method,the cells in P-SIS tissue were removed by deionized water?gradient alcohol?isopropanol?chloroform and so on,and freeze dried.(3)The residual cell ?the content of fat and endotoxin?the cytotoxicity and the quantity of growth factor were respectively detected.2.Constructing mash:(1)8SIS patch: the lyophilized P-SIS was trimmed,then spliced into 8 layers by hydration,using the vacuum lamination technique made those P-SIS tight binding.(2)PDO-SIS mash: the lyophilized P-SIS was trimmed,the P-SIS and PDO elastic fiber intersect knitting,then spliced by hydration,using the vacuum lamination technique made those P-SIS tight binding.(3)The mash of tensile force and bending length will be respectively tested by the instrument.3.Repairing rat abdominal wall partial defects:(1)Creating an abdominal wall partial defect model in SD rat by surgical.(2)According to autogenous contrast,the defects of both sides of rectus abdominis muscle were repaired with 8SIS patch and PDO-SIS patch respectively.(3)To observe the postoperative general condition of animal,including the incidence of seroma,infection rate and mortality rate.(4)The harvested specimen were respectively stained with immunohistochemistry?(CD68,CD206,CCR7,CD31)?Masson and HE,and analyzed the inflammation?tissue structure?vascularization and the constituent ratio of macrophages.(5)To observe the general situation of regenerative tissue,including the tissue thickness and shrinkage.Research results:(1)The prepared P-SIS tissue had no residual cells,lower fat and endotoxin content,no cytotoxicity,and moderate growth factors,can promoted cell proliferation in vitro.(2)The PDO-SIS patch was successfully constructed by the cross-knitting method.The hybrid mash was compact and the mechanical properties were significantly higher than the 8SIS patch.After hydration,the PDO-SIS patch can still maintain a good bending length,it is more flexible and convenient to use.(3)In vivo repair experiments,different degrees of seroma could be observed in the repair area within 1 weeks after the operation,but none of the two patches induced acute immune rejection or cytotoxic reaction.The chronic inflammatory reaction was observed in HE staining,and the inflammation decreased gradually with the prolongation of time,and there was no significant difference between the two groups.Mononuclear macrophages appeared in the repair area from the beginning.with the degradation of P-SIS,the number of macrophages was gradually decreased.At eighth weeks after operation,a few scattered macrophages were seen in the sections.Two different subtypes of differentiated macrophages(M1 and M2)showed a dynamic change in the body.At 2 weeks after surgery,the ratio of M1 to M2 was close to 1:1,type M2 macrophages occupied the majority.With the prolongation of repaired time,the number of M2 type macrophages was more than M1.In the later period of repair,the structure and organization collage can be observed in the Masson staining.The regenerated tissue was transparent,but the thickness was lower than that of normal abdominal wall tissue.Vascular endothelial cells and vascular structures were observed in the two groups,and the vascular structure of PDO-SIS group was more than the 8SIS group.Research conclusion:(1)The P-SIS material prepared by this experiment can promote cell proliferation in vitro,and has high biological activity.In this study,we successfully constructed a hybrid PDO-SIS patch,this mash of the structure is relatively tight,not loose after hydration.The tensile strength and bending length of the hybrid patch were significantly better than that of the 8SIS patch.The hybrid patch was more flexible.The PDO material can make up for some deficiencies in the mechanical properties of the biological patch.(2)In vivo,both mash can promote tissue reconstruction.The PDO elastic fiber in the patch did not induce acute immune rejection,and did not change the type of immune response in the repair area,still dominated by M2 type macrophages.The degradation of PDO can accelerate the deposition of collagen and promote the regeneration of blood vessels.(3)Both mash can promote tissue reconstruction,however,the regeneration of tissue is mainly collagen,no muscle tissue regeneration,no innervation,lack of contraction,unable to achieve functional repair,tissue repair materials need to be further improved.Innovation point:In this experiment,through the combination of biological materials and synthetic materials,create a new hybrid patch,the method and technology for the first time to explore at home and abroad(with proof search),which provides a new way for the research on a new type of hernia repair materials.