Cardiac tissue engineering: Cell seeding, cultivation parameters, and tissue construct characterization

Cardiac tissue engineering has been motivated by the need to create functio nal tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs c an be cultivated using isolated cells, 3-dimensional scaffolds,and bioreact ors. In the present work, we examined the effects of (1) cell source (neona tal rat or embryonic chick), (2) initial cell seeding density, (3) cell see ding vessel, and (4) tissue culture vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed condition s with rat heart cells at a high initial density ((6-8) x 10(6) cells/polym er scaffold) maintained structural integrity and contained macroscopic cont ractile areas (approximately 20 mm(2)). Seeding in rotating vessels (lamina r flow) rather than mixed flasks (turbulent flow) resulted in 23% higher se eding efficiency and 20% less cell damage as assessed by medium lactate deh ydrogenase levels (p < 0.05). Advantages of culturing constructs under mixe d rather than static conditions included the maintenance of metabolic param eters in physiological ranges, 2-4 times higher construct cellularity (p le ss than or equal to 0.0001), more aerobic cell metabolism, and a more physi ological, elongated cell shape. Cultivations in rotating bioreactors, in wh ich flow patterns are laminar and dynamic, yielded constructs with a more a ctive, aerobic metabolism as compared to constructs cultured in mixed or st atic flasks. After 1-2 weeks of cultivation, tissue constructs expressed ca rdiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per u nit cell when compared to native cardiac tissue. (C) 1999 John Wiley & Sons , Inc.