Research Of Building Animal Models Of Keloid By Using The Method Of The Tissue Engineering

Research Object and Signification:Cicatrization is one of necessary results to the reparation of thewound. But excessary reparation may lead to pathologic scar and bring the damage of figuration and vary degree function obstruction. Pathologic scar is a skin fibrosisis disease and it has the character of excessary aggradation of collagen. Hypertrophic scar and keloid is the pathologic scar which is often seen in clinic especially for the second. In clinic keloid grow excessively and overrun original wound to violate near tissue like crab foot. It is difficult to degenerate all the time and easy to recrudesce after operation. The therapy against them is a difficult problem worrying us. For lack of good animal models, the research for hypertrophic scar and keloid go ahead slowly. In 1985, Shetlar succeeded in transplanting of human keloid into athymic mice. After that, Estrem make some deeper research. He cut the keloid tissue to 1um slice and at the same time cultivate its fibroblast to do subcutaneous transplantation into athymic mice with them separately. After 2 month there was not marked significance compared with theoriginal keloid tissue in general appearance or microscope configuration. This results not only approved Shetlar's conclusion but also showed the fibroblast of keloids also has the capacity of producing abundant collagen abnormally. And it provides a good theoretics supportting for establishing the animal model of hypertrophic scar and keloid. In 1989,Kischer added the volume of hypertrophic scar and keloid to 5mm X 5mm X 8mm and remove epidermis and do subcutaneous transplantation into athymic mice for 246 day's continuing observation. In 1991,Hayward and Polo had the big rats without thymus carrier and transplant the keloid to the valove with blood vessel pedicel to make a kind of animal model of keloid and made time of 12 months' observation. These models have some progress. However, these model have hereinafter limitation:①The transplanted tissue is the formed HS and K and can not reflect the developing process from wound's reparation to pathologic cicatrisation and it is unfit for the research of pathologic scar's mechanism and precaution.② The transplanted HS and K is divorced from their original environment and the results may has some windage.③ The material is limited and can not do man-made control to get a satisfied comparation of the model.④ HS and K do not grow or grow a fat lot although keeping their histology character after transplantation and this appearance is different from in body's. And the reason may include the transplanted tissue excluded, the cell in athymic mice producing collagen enzyme to decompose the transplanted tissue, poor blood supply or FB losing collagen gene regulated factor's feedback mechanism.⑤The livability of tissue's dissociating transplantation is low and the chance of successis not satisfied. In order to get over these disadvantages, some scholar has been attemptting to make HS and K in some special animal itself. Someone had the report that scar just like K can come into being on horse in 1951.Morris did the whole floor skin wound deep inside cartilage in ventro-side of rabbit ear and did 288 day's continuing observation and found 11 of 16 wounds (69 percent) form hypertrophic scar which tower above skin. And from histology inspection they found in derma collagen fibril arrangement was turbulence and could find special collagen fibril node. They also found some supercilious inflammation in which blood vessel manifold. Morris consider this model could be used to do some research for the pathogenesis of HS and K as well as do some judgement for the curative effect of it. LI Hui-yuan did similar research from 1988 at home. Also,these kind of models exist some limitation:?there are fury argument about that whether the procreant scar is HS or K.(2)The degree of scar hyperplasia is far more than good as HS or K of human being and its sustaining time is shorter. ?These models is hard to be built successfully.With the development of tissue engineering, there are many reports about succeeding in building relevant tissue and apparatus from cell level. In 1984,the famous Chinese scholar named FEN Yuan-zhen brought forward the conception of tissue engineering for the first time. And then following it, Skalak and Fox in 1988,Nerem in 1991,Langer and Vacanti in 1993 put forward this conception. It is defined that tissue engineering is that using the principle and method of life sciences and engineering science, and in the basic of making right knowing about mammal's normal or pathologic relationship of organizingconfiguration and function, scientists do the research of life-form substitute to repair, mainten and promote the function and configuration after tissue or apparatus is hurt. It is a new subject. Following the development of cell-biology, molecule-biology and biomaterial, the research and applying of tissue's tissue engineering have been making good progress. Now The Tissue Engineering is coming into being. It not only improves the curing level and the sufferer's living quality but also reduce fee-for-service. It is now in process of forming high-new technique industry. It includes four points in the research of tissue engineering mostly: germ cell, scaffold, building apparatus and clinic using. The scaffold and germ cell is more important than the other two. For scaffold the research and using the polylactic acid (PLA), polyglycolic acid (PGA) and PLGA (the copolymers of polylactic acid (PLA) and polyglycolic acid (PGA)) is hot presently. Both PLA and PGA are belong to a-polyesters. Inside body PLA is degradated to lactic acid which is the metabolizing offspring of carbohybrate; PGA is degradated to glycolic acid which is easy to join the inner metabolize. The ester-bond in PLGA is easy to hydrolyze. And changing the proportion between PLA and PGA could control the degradated time of PLGA. It can be from several weeks to several years. These polymers belong to heat-modeled plastic and can be machined to all kinds of shape by modeling, extrusion or solvent-typecast. For the innocuity and good biocompatibility of its degradated offspring, PLA and PGA have consider using as suture, temporality scaffold and drug-control carrier by FDA. The aim of our research is to use the principle and method of tissue engineering to build the animal model of keloid and to explorethe feasibility to do clinic and lab research by this model. Method:Fibroblasts (FB) were isolated and cultured from keloids. After FB was transferred to generation six or eight we inoculate it to PLGA and then keep them in rotatory cell culture system ( RCCS)for 1 week prior to subcutaneous transplantation into 20 athymic mice.After4, 8,16,24 weeks, the specimens were cut out and examined histological. Results:All mice survived after surgery. The collagen pattern of all keloids were remained in every cases after 24 weeks. We can see there are lots of FB and its secreted collagen in specimens by light microscope. And we also can see there are FB in specimens by transmission electron microscope, and there are good many of rough endoplasmic reticulum (RER) in FB. These demonstrate the FB in specimens remains the capability of synthesizing and secreting collagen to approve its sustained cellular character. Conclusion:There is a good affinity between PLGA and FB. And the composition of PLGA and FB could form keloids in athymic mice. The model is worthy to do deeper research to find better animal model for the study of keloid.