Human embryonic stem cells (hES cells) and human induced pluripotent stem cells (hiPS cells) are defined as human pluripotent stem cells [1,2]. They have two unique properties: unlimited selfrenewal and pluripotency, which made them attractive for human early development research, disease modeling, drug screening and cell replacement [1-4].

The most important potential of hES and hiPS cells is they could be used clinically to develop replacement cells for transplantation medicine for diseases caused by loss of cell or cell function [5-8]. One recent promising progress is the transplantation of RPE cells in human patients [9,10]. The first use of hES cell-derived RPE cells in human patients was described by Schwartz group, in one patient with Stargardt’s macular dystrophy and another with dry AMD. Initial results show no significant improvement in visual function as loss of photoreceptor cells is at an advanced stage, but do suggest a good safety profile [9,10]. A number of clinical trials investigating the safety of ESC-RPE are now underway or planned. The study of transplantation of hiPS-derived RPE sheet in human with exudative age-related macular degeneration is underway in Japan. The first patient receiving transplantation was in September 2014. This is the first human clinical trial to use iPS-derived cells. The outcomes of this trial are anxiously awaited.

These promising applications of hES cells and hiPS cells have opened exciting avenues for regenerative medicine, disease modelling and drug screening. To harshness these potentials, we need to further understand the fundamental mechanisms of hES/hiPS cells self-renewal, pluripotency, disease mechanism and clinical trial in order to manipulate the process and improve the quality, efficiency, accuracy and consistency of generating target cells.

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