Electrospun microfiber meshes have been shown to support the proliferation and differentiation of many types of stem cells, but the phenotypic fate of c-kit(+) human cardiac stem cells (hCSCs) have not been explored. To this end, we utilized thin (similar to 5 mu m) elastomeric meshes consisting of aligned 1.7 mu m diameter poly (ester-urethane urea) microfibers as substrates to examine their effect on hCSC viability, morphology, proliferation, and differentiation relative to cells cultured on tissue culture polystyrene (TCPS). The results showed that cells on microfiber meshes displayed an elongated morphology aligned in the direction of fiber orientation, lower proliferation rates, but increased expressions of genes and proteins majorly associated with cardiomyocyte phenotype. The early (NK2 homeobox 5, Nkx2.5) and late (cardiac troponin I, cTnI) cardiomyocyte genes were significantly increased on meshes (Nkx=2.5 56.2 +/- 13.0, cTn/=2.9 +/- 0.56,) over TCPS (Nkx2.5 = 4.2 +/- 0.9, cTnl=1.6 +/- 0.5, n=9, p < 0.05 for both groups) after differentiation. In contrast, expressions of smooth muscle markers, Gata6 and myosin heavy chain (SMMHC), were decreased on meshes. Immunocytochemical analysis with cardiac antibody exhibited the similar pattern of above cardiac differentiation. We conclude that aligned microfiber meshes are suitable for guiding cardiac differentiation of hCSCs and may. facilitate stem cell-based therapies for treatment of cardiac diseases. (C) 2016 Elsevier Inc. All rights reserved.