Pharmaceutical applications of embryonic stem cells.

Embryonic stem cells (ESCs) will become a source of all adult differentiated cells once reliable protocols for directed differentiation have been established. This resource will revolutionise laboratory cell biology and will provide much improved cell culture models for discovery and development of drugs, and fundamental studies of the genetic basis of disease. These are early days, and there are few examples of practical outcomes in the pharmaceutical world, though in recent years some drug-like molecules, which direct differentiation, have been discovered. At this stage the focus is on understanding the signalling systems and transcription factors that drive differentiation, on characterisation and isolation of precursor cells, and on establishing methods to improve the homogeneity of differentiated cells derived from ESCs. There is particular interest in establishing methods for deriving fully differentiated human cells from human ESCs (HESCs), but there are challenges to be met before HESC technology can be taken up in a widespread manner. Protocols for expansion of HESC cultures are labour-intensive at present. There is an urgent need for discovery of factors that will allow serum-free (and feeder cell-free) expansion of HESCs, and which can be applied to the majority of HESC lines. Our expectation is that adequate protocols will emerge in the coming years opening the way for development of many cell culture tools in the pharmaceutical industry. Here we review the current status and future prospects for this exciting field and encourage pharmaceutical scientists to play a role in directing its development.