The Expermental Study Of Reparring Abdominal Wall Defects In Rats By Using New Biodegradable Materials

Due to the trauma, abdominal-wall tumors or population aging etc, the incidence rate of abdominal-wall defect and lateral ventral syndrome are all gradually increased. The application of tension free repair in some operations, i.e, on bdominal-wall defect and lateral ventral syndrome, are accepted gradually and even have become the standard operations in some countries. The patch was used in all kinds of abdominal-wall defect and lateral ventral syndrome including inguinal hernia, lateral ventral syndrome, incisional hernia. Whereas the contraindication is only restrict at children and those whose operating field are infected. The consumption of the patch is up to 1,000,000 each year in all over the world. Currently, most commonly used patch in reparing abdominal-wall defect and lateral ventral syndrome are polypropylene, polyester, expande polytetraflouroethylene (ePTFE), etc. and they are all non-absorbing material.The application of Polypropylene patch are quite extensive due to their characteristics of stabilization, firm, inertia and fine texture, but the products is so different in their shape, size, density and aperture with relative company. The disadvantage of the Polypropylene patch are as metioned below:crude surfaces; potential adhesions with organs in peritoneal cavity; causing Intestinal fistula by erosing intestinal canal; the formation of skin sinus tract after infection or cicatrix contracture and patch twist. Polyester, which is Dacron, is the secondary biggist consumption patch, only rank after Polypropylene. Polyester patch has the feature of hydrophilicity so that the tissue cicatrix contracture is much lighter than that of heavy weight Polypropylene patch.Whereas it's disadvantage is poor histocompatibility, so the patch must be taken out as long as infection occurs. There are some kinds of expande polytetraflouroethylene are considered as safe due to their moderate adhesions cases,there are seldom the intestinal fistula after being treated with ePTFE. Unfortunately, ePTFE is belongs to the micropore materials which leads to such a situation that seroma might occurs as the pore space is too small to allow fibroblasts, macrophages to crawl in, which must be infected by bacteria. Thus, the patch must be moved finally. Biomaterial patch is novel product in recent study, there are kinds of Biomaterial patch including or non-human source be invented after risking so much infections and operation failures. Whereas, those material is restricted in clinical therapy because of lacking the supporting testimony. The repairing materials metioned above are all imported from overseas so that can not be accepted by patient even our doctors. Therefore, it is extremely important to develop a new, domestic, inexpensive, ideal therapeutic effect, degradable material to deal with abdominal-wall defect and lateral ventral syndrome.Polypropylene carbonate (PPC), also called poly (propylene carbonate), is a polyalkylene carbonate plastic material, a copolymer of carbon dioxide and propylene oxide, which is a biodegradable plastic. Its nontoxic, no pollution, and good transparence, biocompatibility and plasticity are suitable for being a new type of biomaterial. But its low glass transition temperature, thermostability and hardness make it difficult for PPC to be biomaterial alone. Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate, a polymer belonging to the polyesters class, which is produced by micro-organisms. It is non toxic, biodegradable, biocompatible so is suitable for medical applications. But its brittleness and bad thermostability make it can't be used in medical applications. Neither PPC nor PHB alon can be used as biomaterial for abdominal-wall defect and lateral ventral syndrome.In our research, we have developped a series of new biodegradable polymers, porous modified-polypropylene carbonate (PM-PPC), by admixing PPC and PHB at different ratio and salting out to make it multiaperture. PM-PPC combine the good qualities of PPC and PHB, maked it more suitable for medical application. The admixture of PPC and PHB at the ratio of 90:10 can be used as biomaterial for abdominal-wall defect and lateral ventral syndrome. In this research, we have investigated the physico-mechanical function, degradation ability and biological availability of abdominal-wall defect repair of PM-PPC, abstract as follow:Part I:Research on physical function of PM-PPC and PP. PP is the initial repairing material of abdominal wall used in clinic application. It was developed by Johnson & Johnson Company in 1981 and put on the market afterwards. Now it is accepted by the clinic doctors and patients and widely used in the therapy of clinic abdominal wall injury. What we developed here is the new modified degradable biomaterial PM-PPC. It's a mixed porous material which PHB is 90:10. In this part of the study, PM-PPC and PC were compared on weight, fiber weight, pore size, bending strength, tearing of traction force, maximum traction force, pressure resistance and extension capability under 16N/m2. We demonstrated that there is no significant difference between PM-PPC and PP on these properties. PM-PPC is suitable for the restoration of abdominal wall injury.PartⅡ:The study of compatibility of fibroblast with porous modified-polypropylene carbonate (PM-PPC). The fibroblast is important for abdominal wall repair and rebuilding. In this study, we isolate and culture the primary Wistar peritoneum fibroblast by tissue culture and identify the cells by immunofluorescence, electron microscopy and vimentin blot. The identified fibroblast as the seed cells, is inoculated into culture plates in 3.5×105 cell concentration and cultured. The material can directly contact with cells, we observe the growth capacity of fibroblasts regularly. On the different time points, we observed the compatibility of materials with fibroblast in vitro by cell counting and scanning electron microscope method of surface materials. The results show that the fibroblast can adhesion, elongation and proliferation on the surface of PM-PPC. PM-PPC have good compatibility with fibroblast which can be repair materials for abdominal wall defection.PartⅢ:The study of compatibility of porous modified-polypropylene carbonate (PM-PPC) with rats'abdominal wall tissue. We dissociated the preperitoneal space by surgical method, then put the PM-PPC patch and PP patch into the preperitoneal space and closed the abdomen. We observed the fiber production and arrangement, cells number and distribution by HE staining. the expression of tumor growth factor-β(TGF-β) antibody and fiber growth factor (FGF) by immunohistochemistry and the function of fibroblast by electron microscope techniques in 1,3,5,7 and 14 days after surgery. The results show that 3 to 5 days after surgery is the peak expression period of TGF-β. The expression of PM-PPC group and PP group is significantly higher than control, which show PM-PPC can stimulate the overexpression of TGF-βduring the abdominal wall repair, but which have no significant difference with PP group.3 to 5 days after surgery is the peak expression period of FGF. The control group is significant lower than PM-PPC group and PP group, which show PM-PPC can stimulate the overexpression of FGF during the abdominal wall repair, but which have no significant difference with PP group.The partⅣ:study on the restoration of abdominal wall injury with PM-PPC. Abdominal wall injury animal model was established by surgical resection of rectus abdominis anterior sheath, rectus abdominis. Then, PM-PPC and PP were implanted into the injury position, respectively. Histology and ultrasonography examination were employed to evaluate the restoration process of abdominal wall injury at the week 2,4,8,12 after surgery. At week 12, PM-PPC and PP group exhibited good restoration effect without occurrence of abdominal wall hernia. However, abdominal wall hernia formed in the control group without implanted material at week 12. Rose Bengal-polarized light technique was utilized to detect the collagenⅠ,Ⅲexpression in rectus sheath. PM-PPC and PP could improve the expression of collagenⅠand increase the ratio of collagenⅠandⅢ, which could further enhance the abdominal wall strength and reduce the occurrence of abdominal wall hernia.