The transcriptome of embryonic stem cells
Embryonic stem cells (ESCs), derived from the blastocyst stage of early mammalian embryos, are distinguished by their ability to differentiate into any cell type and by their ability to propagate. It is these traits that makes them valuable in the scientific and medical fields. ESCs are also described as having a normal karyotype, maintaining high telomerase activity, and exhibiting remarkable long-term proliferative potential.
Embryonic stem cells of the inner cell mass are pluripotent, meaning they are able to differentiate to generate primitive ectoderm, which ultimately differentiates during gastrulation into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult human body. Pluripotency distinguishes embryonic stem cells from adult stem cells, which are multipotent and can only produce a limited number of cell types.
Under defined conditions, embryonic stem cells are capable of propagating indefinitely in an undifferentiated state. Conditions must either prevent the cells from clumping, or maintain an environment that supports an unspecialized state. While being able to remain undifferentiated, ESCs also have the capacity, when provided with the appropriate signals, to differentiate (presumably via the initial formation of precursor cells) into nearly all mature cell phenotypes.
Due to their plasticity and potentially unlimited capacity for self-renewal, embryonic stem cell therapies have been proposed for regenerative medicine and tissue replacement after injury or disease. Pluripotent stem cells have shown potential in treating a number of varying conditions, including but not limited to: spinal cord injuries, age related macular degeneration, diabetes, neurodegenerative disorders (such as Parkinson's disease), AIDS, etc. In addition to their potential in regenerative medicine, embryonic stem cells provide an alternative source of tissue/organs which serves as a possible solution to the donor shortage dilemma. Not only that, but tissue/organs derived from ESCs can be made immunocompatible with the recipient. Aside from these uses, embryonic stem cells can also serve as tools for the investigation of early human development, study of genetic disease and as in vitro systems for toxicology testing.