Oxygen gradients correlate with cell density and cell viability in engineered cardiac tissue

• Published in: Biotechnology and bioengineering 2006-02, Vol.93 (2), p.332-343
• Main Authors: Radisic, Milica, Malda, Jos, Epping, Eric, Geng, Wenliang, Langer, Robert, Vunjak-Novakovic, Gordana
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biomarkers - analysis; Biotechnology; cardiac tissue engineering; cardiomyocytes; Cell Count; Cell Survival; Cells; diffusion; Fundamental and applied biological sciences. Psychology; Health. Pharmaceutical industry; Heart; Industrial applications and implications. Economical aspects; Miscellaneous; Myocytes, Cardiac - chemistry; Myocytes, Cardiac - metabolism; Oxygen; Oxygen - analysis; Oxygen - metabolism; Oxygen Consumption; oxygen profile; Rats; Rats, Sprague-Dawley; Skin & tissue grafts; Tissue Engineering; viability
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.20722

For clinical utility, cardiac grafts should be thick and compact, and contain physiologic density of metabolically active, differentiated cells. This involves the need to control the levels of nutrients, and most critically oxygen, throughout the construct volume. Most culture systems involve diffusional transport within the constructs, a situation associated with gradients of oxygen concentration, cell density, cell viability, and function. The goal of our study was to measure diffusional gradients of oxygen in statically cultured cardiac constructs, and to correlate oxygen gradients to the spatial distributions of cell number and cell viability. Using microelectrodes, we measured oxygen distribution in a disc‐shaped constructs (3.6 mm diameter, 1.8 mm thickness) based on neonatal rat cardiomyocytes cultured on collagen scaffolds for 16 days in static dishes. To rationalize experimental data, a mathematical model of oxygen distribution was derived as a function of cell density, viability, and spatial position within the construct. Oxygen concentration and cell viability decreased linearly and the live cell density decreased exponentially with the distance from the construct surface. Physiological density of live cells was present only within the first 128 µm of the construct thickness. Medium flow significantly increased oxygen concentration within the construct, correlating with the improved tissue properties observed for constructs cultured in convectively mixed bioreactors. © 2005 Wiley Periodicals, Inc.