Engineering a microvascular capillary bed in a tissue-like collagen construct.

Previous studies have shown that plastic compression (PC) of collagen gels allows a rapid and controlled fabrication of matrix- and cell-rich constructs in vitro that closely mimic the structure and characteristics of tissues in vivo. Microvascular endothelial cells, the major cell type making up the blood vessels in the body, were added to the PC collagen to determine whether cells attach, survive, grow, and express endothelial cell characteristics when seeded alone or in coculture with other cells. Endothelial cells seeded on the PC collagen containing human foreskin fibroblasts (HFF) or human osteoblasts (HOS) formed vessel-like structures over 3 weeks in culture without the addition of exogenous growth factors in the medium. In contrast, on the PC scaffolds without HFF or HOS, human dermal microvascular endothelial cells (HDMEC) exhibited a typical cobblestone morphology for 21 days under the same conditions. We propose that the coculture of primary endothelial cells with PC collagen constructs, containing a stromal cell population, is a valuable technique for in vitro modeling of proangiogenic responses toward such biomimetic constructs in vivo. A major observation in the cocultures was the absence of gel contraction, even after 3 weeks of fibroblast culture. This collagen form could, for example, be of great value in tissue engineering of the skin, as contractures are both aesthetically and functionally disabling.