The derivation of the first human embryonic stem cell (hESC) lines in 1998 by Thomson and colleagues (1) was a seminal moment in stem cell biology. By definition, hESC are capable of growing indefinitely in culture as well as being able to differentiate into cells representative of all three embryonic germ layers -- ectoderm, mesoderm and endoderm (1, 2). Because of these properties, the derivation of hESC marked the beginning of a new area of research not only for basic biology but also for regenerative medicine and drug discovery. It is widely accepted that hESC are a promising source of a variety of cell types for future cell based therapies. To be able to use these cells for regenerative medicine, we must have a much deeper understanding of the basic biology of hESC, so that we can develop efficient means of differentiating them into clinically useful cell types (3). The main goals that remain include: (i) derivation and differentiation of hESC under good manufacturing practice (GMP) conditions; (ii) understanding the mechanisms by which cell fate is determined, which might better facilitate directed differentiation; (iii) large-scale culture of hESC and their differentiated progeny; (iv) selection and expansion of pure populations of desired cell types; (v) analysis of efficacy and safety in various animal models of disease; and (vi) overcoming immunological tolerance of allogenic cells. If these obstacles can be surmounted then the possible benefits to human health will be great indeed (4).
1. Thomson, J.A., Itskovitz-Eldor, J., Shapiro, S.S., Waknitz, M.A., Swiergiel, J.J, Marshall, V.S., et al. Embryonic stem cell lines derived from human blastocysts. Science 282, 1145-1147 (1998).
2. Stojkovic, M., Lako, M., Stojkovic, P., Stewart, R., Przyborski, S., Armstrong, L., et al. Derivation of human embryonic stem cells from Day 8 blastocysts recovered after three-steps in vitro culture. STEM CELLS 22, 790-797 (2004).
3. Cooke, M., Stojkovic, M., Przyborski, S. Growth of teratomas derived from human pluripotent stem cells is influenced by the anatomical location of the graft site. Stem Cells and Development 2, 254-259 (2006).
4. Cervera, R.P., Stojkovic, M. Human embryonic stem cell derivation and nuclear transfer: Impact on regenerative therapeutics and drug discovery. Clinical Pharmacology & Therapeutics (in press).