RECOMBINANT HUMAN COLLAGEN & CTGF FOR TISSUE ENGINEERING

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The combination of a growth factor capable of effecting the regeneration of a tissue with a matrix suitable to act as a scaffold for that tissue is a central tenet in tissue engineering. We propose to test this hypothesis by developing prototype tissue engineering biomaterials for in vivo and in vitro proof of concept studies. Connective tissue growth factor (CTGF), a key fibrogenic growth factor, acts downstream of TGF- beta to promote mesenchymal cell proliferation and to stimulate extracellular matrix deposition. Our recent data suggest a role in development and differentiation of cartilage, skin and bone. Uses of CTGF in tissue engineering applications are unexplored. Strength, persistence and biocompatibility are unique and inherent properties of collagens that make these proteins well suited as scaffolds for these studies. Although animal-derived collagens are available and most frequently used as biomaterials, there are increasing concerns about their purity, safety and immunogenicity. Of the 20 known collagens, only type 1 collagen has been evaluated as a biomaterial, again because it is the only collagen economically extracted from tissue. Until recently, recombinant expression of human collagens has been difficult due to the significant post translational modifications needed for function. Our success with collagen expression technology now provides a means to generate and explore uses of the rarer, tissue-specific human collagens such as types II (predominant in cartilage) and III (prominent in vessels). To evaluate recombinant human collagens and CTGF as components of tissue engineering therapeutics we specifically will: 1) produce recombinant human collagen types I, II, and III in a cost effective, commercially viable yeast expression system. This will involve expression, purification, formulation and characterization; 2) evaluate biocompatibility of the recombinant human collagens compared to tissue- derived materials; 3) investigate in vitro how matching mesenchymal cell type and collagen matrix affects cell attachment, differentiation, migration, proliferation and survival and also determine the effects of including CTGF in these scaffolds; and, 4) evaluate these CTGF augmented scaffolds in tissue engineering applications using in vivo models of tissue repair and regeneration that focus on cartilage, bone and skin. The momentum of our ongoing programs and commitments in related areas will leverage additional support to expedite the development of these novel therapeutic prototypes that are capable of addressing significant medical needs. In addition, further avenues for research and development, based on novel combinations of cytokines and engineered and/or tissue-specific collagens, will have been identified.