Turning Stem Cells from Fat into Blood Vessels

Researchers at the University of Oklahoma (Norman, USA) first differentiated adipose-derived stem cells into smooth muscle cells (SMCs), and then seeded them onto a flat sheet of the human amniotic membrane--a very thin collagen membrane--used as a biological substrate to fabricate the small-diameter TEBVs. To develop a tubular construct similar to that of a muscular artery's tunica media layer, the cell-seeded sheet was wrapped around a 3-mm removable mandrel with six to seven revolutions. After a two-week static culture period, the fabricated TEBV was assessed for biochemical and mechanical properties.

The researchers examined and compared the contraction of the vessel in response to carbachol--a specific agonist for SMCs--to that of porcine coronary arteries; burst pressure and elastic modulus tests were also conducted. The researchers found that the thickness and architecture of the engineered vessel matched that of a porcine coronary artery in a histological analysis; it also performed better than the porcine vessel for elasticity in a tensile strength test. However, the burst pressure was too low, at about 150 mm Hg, while native tissue withstands 1,000 mm Hg. The problem, according to the researchers, appeared to be that the layers of the rolled-up vessel are not adhering well to one another.

The researchers found that the mechanical integrity of the construct could be further improved by exposure to appropriate physiological conditions in a perfusion bioreactor, and that adipose-derived endothelial cells also could be seeded into the lumen of the construct to prevent platelet adhesion. The study was presented at the American Heart Association Basic Cardiovascular Sciences 2012 scientific sessions, held during July 2012 in New Orleans (LA, USA).

“These liposuction-derived vessels, grown in a lab, could help solve major problems associated with grafting blood vessels from elsewhere in the body or from using artificial blood vessels that are not living tissue,” concluded lead author and study presenter Matthias Nollert, PhD, and colleagues of the school of chemical, biological, and materials engineering. “Our engineered blood vessels have good mechanical properties and we believe they will contract normally when exposed to hormones.”

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