Tissue Engineering for Ligament and Tendon Repair – TELiTeR

1-Scientific background and objectives Ligaments and tendons play a crucial role in joint movement and stability. Some of them have bad or no healing capacity (e.g. the anterior cruciate ligament). Four options have been utilized for the repair or replacement of damaged ligaments or tendons : autograft, allograft, xenograft, and synthetic prostheses. Despite of certain satisfactory results, the use of human grafts has big problems such as donor site morbidity, permanent immunosuppressive treatment, lack of donors, etc. Xenografts and artificial prostheses are rarely used in clinic, even though the treatment of non-degradable prostheses by biopolymers could be a new trend of research. Today tissue engineering is emerging as a new technique. Based on biological and physical manipulations on cells, it aims at the regeneration and reconstruction of tissues or organs. By using autologous cells and biodegradable materials, it would allow to overcome the limitations of human grafts mentioned above. The objective of this project is to construct biotissues having realistic dimensions and acceptable biological and mechanical properties for the repair or replacement of damaged ligaments or tendons. Preliminary works have been carried out in our groups in Nancy since 2002 with financial supports of the French National Center for Scientific Research (CNRS, ATIP/SPI) and the Lorraine Region (Emerging theme), France. Given the multi-disciplinary nature of this project, four groups of public research institutions in Nancy specialized in biomechanics and mechanical engineering (LEMTA UMR 7563), polymer science (LCPM UMR 7568), biochemical engineering (LSGC UPR 6811), and biology-surgery (Surgery School of the Faculty of Medicine of Nancy), respectively, will participate to the present project. 2-Description of the project, methodology The principle of tissue engineering seems simple: living cells are seeded onto a biodegradable template (scaffold). The cells proliferate, differentiate, secret their own extra cellular matrices, and finally form a neo-tissue while the scaffold degrades. In this project we will methodologically focus on the following points: Cell source The multi-potent bone marrow mesenchymal stem cell (bMSC) has a great potential to be used as a cell source in tissue engineering. Thus we will study the proliferation and differentiation of bMSCs in comparison with ligament fibroblasts combined with biodegradable materials. Biochemical culture conditions Cell proliferation and differentiation depend largely on the presence of biochemical regulatory factors, in particular growth factors. We will identify the growth factors necessary for ligaments and tendons construction. Scaffold A scaffold provides a structural and logistic template for cell adhesion and tissue development. It must be made of biocompatible and biodegradable materials, have a 3D structure with high porosity, and possess adequate mechanical properties. Bioreactor Recent studies show that mechanical loadings have important influence on cell activities and tissue development. Thus the control of mechanical conditions in a bioreactor during tissue construction is a key point of this project. The influence of the physico-chemical parameters (pH, pO2, temperature) will be studied during kinetic studies with cells in flow chamber, and these parameters will be controlled by coupling a perfused medium tank to the bioreactor. Quality control Aiming at functional tissue engineering, we plan to determine experimentally the properties of healthy and constructed tissues and scaffolds. Also, theoretical and numerical modeling (soft tissue and composite mechanics) will be performed. Animal model From cell harvest and tissue construction in this project, animals models (rabbit and rat) will enable us to approach as close as possible the physiological and surgical reality and to valid our methodology. 3-Expected results for tissue engineering of ligament and tendon: · Optimize the conditions for bMSC proliferation and differentiation for in vitro biotissue construction · Synthesize an elastic biocompatible and biodegradable polymer · Propose an adequate scaffold · Construct an advanced bioreactor · Obtain experimentally a biotissue · Prepare the conditions for in vivo implantation of the constructed biotissue In addition, the publication of our results in high-level scientific journals is naturally expected and patents will be applied eventually.