Untiring steps toward the maturation of human stem cellengineered heart tissue

Although the generation of a human heart in vitro would be an attempt somewhat beyond human wisdom, many researchers are tackling the subject with enthusiasm, taking advantage of technological progresses in stem cell biology and bioengineering in recent decades. The discovery of human induced pluripotent stem cells (hiPSCs) (1) was a paradigm shift on this research field which opened the door to employ abundant human heart cells (cardiomyocytes, vascular cells and so on) as a source of autologous or allogeneic engineered human heart constructs, which have never been possible with stem cell populations reported so far. Novel protocols to efficiently induce heart cells from hiPSCs (2-4), and bioengineered methods to reconstruct the 3-dimensional (3-D) heart based on porous biomaterials (5-11), decellularized heart (12) or scaffold-free approaches such as cell sheet technologies (3,13-15) are under investigation.