An open access review of work on regenerative medicine based on embryonic stem cells: "The prospect of repairing or replacing damaged, dysfunctional or missing cells with new functional cells has shifted the therapeutic paradigm toward restoring tissue function in individuals affected with aging-associated diseases. The primary candidate for the development of these therapies is stem cells, particularly human embryonic stem cells (hESC), which have the capacity to self-renew indefinitely and differentiate into all tissue-specific cell types... In this review, we will describe the derivation, maintenance, and properties of pluripotent hESCs. We will also outline the methods used to induce the generation of specific cell types from hESCs, with primary focus on cell types that are applicable in understanding the pathology, as well as a potential source of cell-based therapies, in aging-associated diseases. ... As cell replacement therapies are envisioned and realized, their use in the treatment of aging-associated diseases becomes a compelling prospect. hESCs provide much promise as a potential tool in designing such therapies, as well as in drug discovery. It is clear that there are still major scientific challenges as well as ethical and legislative issues that must be addressed. However, it is encouraging to see that clinical trials involving the use of hESCs have begun, and that extensive efforts are underway to efficiently, successfully, and safely differentiate hESCs into specific cell types. These studies will pave the way toward leveraging the therapeutic benefit of hESCs for regenerative medicine, particularly in aging-associated diseases."