Inosculation and perfusion of pre-vascularized tissue patches containing aligned human microvessels after myocardial infarction

Abstract

A major goal of tissue engineering is the creation of pre-vascularized tissues that have a high density of organized microvessels that can be rapidly perfused following implantation. This is especially critical for highly metabolic tissues like myocardium, where a thick myocardial engineered tissue would require rapid perfusion within the first several days to survive transplantation. In the present work, tissue patches containing human microvessels that were either randomly oriented or aligned were placed acutely on rat hearts post-infarction and for each case it was determined whether rapid inosculation could occur and perfusion of the patch could be maintained for 6 days in an infarct environment. Patches containing self-assembled microvessels were formed by co-entrapment of human blood outgrowth endothelial cells and human pericytes in fibrin gel. Cell-induced gel contraction was mechanically-constrained resulting in samples with high densities of microvessels that were either randomly oriented (with 420±140 lumens/mm2) or uniaxially aligned (with 940±240 lumens/mm2) at the time of implantation. These patches were sutured onto the epicardial surface of the hearts of athymic rats following permanent ligation of the left anterior descending artery. In both aligned and randomly oriented microvessel patches, inosculation occurred and perfusion of the transplanted human microvessels was maintained, proving the in vivo vascularization potential of these engineered tissues. No difference was found in the number of human microvessels that were perfused in the randomly oriented (111±75 perfused lumens/mm2) and aligned (173±97 perfused lumens/mm2) patches. Our results demonstrate that tissue patches containing a high density of either aligned or randomly oriented human pre-formed microvessels achieve rapid perfusion in the myocardial infarct environment - a necessary first-step toward the creation of a thick, perfusable heart patch.

Enhanced Directional Migration of Cancer Stem Cells in 3D Aligned Collagen Matrices

“…To generate aligned 3D collagen matrices, we adapted a protocol previously used for tissue-engineering aligned microvessels in fibrin gels (29,30,37). We modified this methodology employed by Tranquillo and coworkers (29,30,37) to account for the differences in mechanical and gelling properties between fibrin and collagen matrices as well as to meet our specific objective of generating acellular, aligned collagen matrices (see Materials and Methods for details).…”

“…We modified this methodology employed by Tranquillo and coworkers (29,30,37) to account for the differences in mechanical and gelling properties between fibrin and collagen matrices as well as to meet our specific objective of generating acellular, aligned collagen matrices (see Materials and Methods for details). In an attempt to mimic the microenvironment of the breast tumor stroma, a primary carcinoma-associated fibroblast line obtained from an autochthonous murine mammary tumor (mFb) was used as the matrix reorganizing agent.…”

“…Aligned collagen matrices were engineered by constrained cellular compaction, using a method adapted from a recently reported technique to align microvessels in fibrin gels (29,30). First, 2.5 Â 1.0 cm rectangular regions were etched on six-well plates by partial melting of the polystyrene using the end of a heated spatula, and 1.0 Â 0.5 cm autoclaved porous polyethylene spacers (Interstate Specialty Products) were glued to the far ends of the region using vacuum grease (Dow Corning).…”

A Net Mold-Based Method of Biomaterial-Free Three-Dimensional Cardiac Tissue Creation

“…28 Riemenschneider et al demonstrated that tissue patches containing a high density of either aligned or randomly oriented, human preformed microvessels resulted in more rapid perfusion when utilized in a myocardial infarct model. 29 In our net mold system, use of the mold cavity removes the need to utilize biomaterials for tissue fusion, allowing perfusion of nutrients and oxygen to deeper portions of the tissue during formation and preventing the formation of a necrotic core. Both the TUNEL staining we performed and quantification of CD31-positive cells support the concept of early vascularization in the net mold patch allowing for improved viability despite creation of a thicker tissue.…”

Bioprinting for vascular and vascularized tissue biofabrication

“…Angiogenesis promoting strategies have focused on either in-growth of newly formed capillaries inside implanted constructs from the host or to achieve a rapid blood supply within engineered constructs by stimulating inosculation with the help of pre-vascularized constructs [29,43]. After implantation, the pre-vascularized channels within the constructs develop interconnections with neighboring tissue vessel network to get perfused rapidly.…”