The generation and use of human embryonic stem cells

Ever since the first human embryonic stem cells (hES) were successfully derived and propagated in 1998 (1), an obvious topic of discussion has been the development of novel therapies based on stem cell technology for a number of diseases and conditions. Targets could include type 1 diabetes, Alzheimer’s disease, spinal cord injury, and Parkinson’s disease to name a few. hES cells can also be used for tissue engineering, to replace for example bone and cartilage, and for drug discovery. Exciting proof of principal experiments in animals demonstrate the clinical potential in this field. For example, in a rat model of Parkinson’s disease, dopamine neural grafts derived from mouse Es cells showed long-term survival, the production of dopamine and, importantly, persistent improvements in movement behaviour (2). The promises of these potential treatments is enormous. However, there are many hurdles to overcome before a therapy based on stem cells is a clinical reality. We outline (A) the variety of methods to derive hES cells including somatic cell nuclear transfer (SCNT) and describe the challenges and possible avenues of further use; (B) discuss the development of clinical grade hES cells and their use in the drug discovery process; and (C) alternative strategies to patient specific therapy including induced adult pluripotent stem cells (iPS cells).