Interactivity of biochemical and physical stimuli during epigenetic conditioning and cardiomyocytic differentiation of stem and progenitor cells derived from adult hearts.

Mixed populations of cardiosphere-derived stem and progenitor cells containing proliferative and cardiomyogenically committed cells were obtained from adult rat hearts. The cells were cultured in either static 2D monolayers or dynamic 3D scaffold systems with fluid flow. Cardiomyocyte lineage commitment in terms of GATA4 and Nkx2.5 expression was significantly enhanced in the dynamic 3D cultures compared with static 2D conditions. Treatment of the cells with 5-azacytidine (5-aza) produced different responses in the two culture systems, as activity of this chemical epigenetic conditioning agent depended on the cell attachment and hydrodynamic conditions provided during culture. Cell growth was unaffected by 5-aza in the static 2D cultures but was significantly reduced under dynamic 3D conditions relative to untreated controls. Myogenic differentiation measured as Mef2c expression was markedly upregulated by 5-aza in the dynamic 3D cultures but downregulated in the static 2D cultures. The ability of the physical environment to modulate the cellular cardiomyogenic response to 5-aza underscores the interactivity of biochemical and physical stimuli applied for cell differentiation. Accordingly, observations about the efficacy of 5-aza as a cardiomyocyte induction agent may not be applicable across different culture systems. Overall, use of dynamic 3D rather than static 2D culture was more beneficial for cardio-specific myogenesis than 5-aza treatment, which generated a more ambiguous differentiation response.