A tissue graft construct for use in repairing diseased or damaged tissues isprovided. The tissue graft construct comprises a matrix composition selectedfrom the group consisting of urinary bladder submucosa and stomach submucosa,and extracts and hydrolysates thereof, added endothelial cells, and at leastone additional preselected, exogenous population of cells which enhanceinitiation of the formation vessel-like structures in the graft construct. Thepreselected population of cells can be a population of non-keratinized orkeratinized epithelial cells or a population of mesodermally-derived cellsselected from the group consisting of fibroblasts, smooth muscle cells,skeletal muscle cells, cardiac muscle cells, multi-potential progenitor cells,pericytes, osteogenic cells, and any other suitable cell type, preferablyselected based on the tissue to be repaired. Methods for enhancing thevascularization in vivo of these tissue graft constructs and for preparingthese graft constructs are also provided.