Perforated Bioinert Chamber: Anovel Model For In Vivo Tissue Engineering And The Research Of Its Application And Microenvironment

The outcome of conventional tissue engineering products for clinical application isunsatisfactory, which would be more promising if the products could be formed in animmunocompetent host. But most researchers use immunodeficient animals such as nudemice as animal models in the in vivo regeneration process of tissue engineering to avoidan inflammatory reaction. In fact, nude mice have become a standard model widelyapplied in tissue engineering, whereas it cannot completely replace the immunocompetentanimal model. Most importantly, regenerated tissue in nude mice is hard to re-apply to therestoration of host tissue defects because of the vascular invasion and admixture of thenude mice cells with seeded cells. Therefore, how to achieve the in vivo regenerationprocess in a place that mimics the subcutaneous environment of nude mice inimmunocompetent animals as transition is the key point. Since the inflammatory reactionsin immunocompetent animals could lead to damage or deformity of the regenerated tissue,which might obstruct the reconstruction, and even the autologous cell source encounteredthe same problem, besides the host vascular invasion and interference would impair thequality of regenerated tissue, so a closed environment that can isolate the implanted cell population from the invasion of host cells and vasculature might be the solution to theproblem. Meanwhile, this environment could not be completely isolated otherwise theimplanted cell in it could not survival either. Ideally this closed setting should provide astable environment which can achieve transmission of body fluid and nutrition and isolatethe host cell in growth and vascular invasion at the same time.In view of the above situation，we designed hollow perforated chamber with siliconeas a novel in vivo tissue engineering model which can be used in both nude mice andimmunocompetent animals. In this study, we would like to examine the ability of thisnovel silicon perforated chamber to support the survival and growth of diversiformimplanted cells and investigate the microenvironment in the chamber. The siliconperforated chambers of different samples were subcutaneously implanted on the backs ofrabbits or rats to measure the exudates volume and collect the exudates for further study.The outcomes showed that this silicon perforated chamber did not cause foreign bodyreaction after implanted, and the exudates volume generated and increased steadily in thismodel. The cell culture tests showed the rabbit chondrocytes, rat mesenchymal stem cellsand human fibroblasts could not only survive but grow well in the condition of exudates,and this had been confirmed by our following assay. The exudates components (TP, ALB,GLU, K+, Na+, Cl-,VEGF, bFGF, TGF-β, IGF-1and PDGF-BB)we tested maintained at astable level and contained enough nutrients and growth factors to keep cell survival anddifferentiation.Tissue engineered cartilage is one of the most promising tissue engineering productsthat could achieve clinical application in future. In order to verify the availability of ourtissue engineering chamber, we constructed tissue engineering cartilage using thisperforated bioinert chamber in our study. We isolated rabbit ear chondrocytes as seed cellsand then we seeded the chondrocytes in PLGA and Matrigel. After4weeks of culture invitro, we found good compatibility of both the seeded cells and the scaffolds. Cell-scaffold complexes were then implanted in the tissue engineering chamber and cultured invivo for another12weeks, and the specimens were collected after then. By generalobservation and histopathology analysis we found that both of the two scaffolds couldform cartilage tissue engineering products with the organizational structure; however, theMatrigel group constructed soft products which could not be used for further study. Tissueengineered cartilage in the PLGAgroup could maintained a good biomechanical indicators, which has more potential clinical value.The results indicate this new setting could not only provide a stable environment thatcan achieve transmission of body fluid, but also isolate the host cell in growth andvascular invasion at the same time. Moreover, the abundance nutrients and growth factorsin the chamber make its application full of great potential in the field of tissue engineering.Using this tissue engineering chamber we have successfully constructed atissue-engineered cartilage with good biological indicators and its availability had beenverified. Our study laid the foundation for the future use of this model in tissueengineering and cell transplantation research.