The Preliminary Study On The Tissue Engineering Urethra

Urethra defects, such as hypospadia or urethral stricture, are rather common in the urological clinic. Whenever there is such a case, reconstruction is usually performed with native, xenogenous tissue or synthetic materials. The use of native skin, bladder or small intestine may lead to numerous complications, such as fistula, stricture or urolithiasis. The xenografts usually encountered immunological rejection. Synthetic materials that have been tried previously in experimental and clinical settings include polyvinyl sponge, Teflon, gelatin sponge, collagen matrices, Vicry matrices, resin-sprayed paper and silicone. Such attempts have usually failed as a result of mechanical, structural, functional, or biocompatibility problems[1' 2]The study of tissue engineering has been mushrooming since Association of American National Science Foundation put forward the concept of tissue engineering in 1987. Soon, it has made great progress in the field of cartilage, bone and etc. And then, Atala and his colleagues suggested the principles of cell transplantation, materials science, and engineering in an attempt to develop a biologic substitute that would restore and maintain normal urologic function. Their strategies include harvesting and expanding patients' native cells; implanting cells on the biodegradable scaffold; transplanting the complex of cell-scaffold in the defect locus to complete reconstruction.Tissue engineering, applies the principles of biology and engineering to the development of functional substitutes for damaged tissue. This method is to lengthen the patient's life.In this study, we have applied the techniques of tissue engineering to constructing a novel urethra. We use the expanded urothelial cell in vitrodeveloped from New Zealand rabbits as the seeding cells. Then the seeding cells are implanted on the collagen membranes. After the cells adhere to the scaffold, the complexes can be transplanted in the subcutaneous of the athymic mice. The methods of morphological analysis and immunochemical analysis are used to determine the biologic character of urothelial cells and the degrading of the scaffold. These studies were to find how to apply the techniques of tissue engineering to build urethra, even to produce commercially materials. The conclusions are identified as follows:1. According to the reports of literatures, we have improved the method of cell dissociation and prescription of culture medium. In that way, we could get abundant cells with high purity and a steady passage of 7 to 9 generations.(1)Both the method of collagenase digestion combined scraping with blade to harvest urothelial cells, and the DMEM culture system added with several growth factors such as EGF are convenient and valid to get enough cells rapidly;(2)The EGF and bFGF stimulate the proliferation of urothelial cells in vitro obviously. And the optimal concentrations are 10ng/ml and 15u/ml.2. It is demonstrated that the nonpoisonous collagen membrane established by freeze-drying is a very good scaffolds for tissue engineering. It has many virtues, such as good compatibility with the urothelial cells, biodegradability, and ability to induce capillaries to grow in.3. The cells attached on and collected alone the collagen fibers, then the scaffold degraded gradually, and the capillaries grew after the complex of cells- scaffold transplanted subcutaneously in vivo. These demonstrated that the complex formed an analog of normal urethra, and it may use as a urethra substitute in the future.