Increased Vascularization and Heterogeneity of Vascular Structures Occurring in Polyglycolide Matrices Containing Aortic Endothelial Cells Implanted in the Rat

The development of sufficient vascularization to maintain adequate perfusion is a primary consideration in the engineering of large tissue constructs. This research investigated the ability of aortic endothelial cells to affect the organization of vascular structures within a matrix both in vitro and in vivo . Highly porous matrices of poly(glycolic) acid (PGA) (50 mg/cc) 10 × 10 × 3 mm meshes were implanted subcutaneously (two per rat) in inbred rats, with and without syngeneic cells. Test groups (n = 8/group) were: PGA; PGA with aortic endothelial cells; PGA with aortic smooth muscle cells; PGA with skeletal muscle cells. Matrices were evaluated histologically from two rats per week at weeks 1,2,3, and 4. Scanning electron microscopy was done on matrices prior to implantation. Matrices without cells demonstrated typical ingrowth of host fibroblasts, capillaries, and macrophages/giant cells. Matrices containing skeletal muscle or aortic smooth muscle cells showed similar vascularization to matrices without cells. The implanted muscle cells demonstrated cellular growth with little organization. Matrices containing aortic endothelial cells demonstrated organized and unorganized endothelial cells within the matrix, increased numbers of capillaries, increased numbers of lymphatic-like structures, and numerous heterogeneous and unusual vascular structures which were positive for factor VIII localization including: 1) large parallel arrays of capillaries, 2) large thin sinusoidal vascular structures, and 3) layered complex vascular structures.