The Adaptability of Somatic Stem Cells: A Review.

Cell and tissue specific somatic stem cells develop as dynamic populations of precursor cells to discrete tissue and organ differentiation during embryonic and fetal stages and their potential evolves with development. Some of their progeny are sequestered into separate cell niches of tissues as adult somatic stem cells at various times during organ development and differentiation These are diverse cell populations of stem and progenitor cells that respond to homeostatic needs for cell and tissue maintenance and the cycling of differentiated cells for physiological/ endocrinological changes. Nominally, multipotent stem cells in one or more niches follow specific lineages of differentiation that can be followed by diverse markers of differentiation.

The urodele limb regeneration blastema: the cell potential.

The developmental potential of the limb regeneration blastema, a mass of mesenchymal cells of mixed origins, was once considered as being pluripotent, capable of forming all cell types. Now evidence asserts that the blastema is a heterogeneous mixture of progenitor cells derived from tissues of the amputation site, with limited developmental potential, plus various stem cells with multipotent abilities. Many specialized cells, bone, cartilage, muscle, and Schwann cells, at the injury site undergo dedifferentiation to a progenitor state and maintain their cell lineage as they redifferentiate in the regenerate.

New paths to pluripotent stem cells.

Stem cells obtained from early mammalian embryos and the subsequent establishment of self replicating embryonic stem cell lines (ES) provided a legacy resource of pluripotent cells capable of differentiating into specific cell lineages of the adult organism. Still the most versatile source of pluripotent cells, their application to potential human therapeutic use has been encumbered by various technical and ethical objections. New sources of embryonic pluripotent stem cells have been sought, the isolation of ES cell lines from a single blastomere that avoids destruction of the human embryo, the use of arrested embryos no longer capable of completing development or using post-implantation embryos as stem cell providers.

Embryos, clones, and stem cells: a scientific primer.

This article is intended to give the nonspecialist an insight into the nuances of "clones", cloning, and stem cells. It distinguishes embryonic and adult stem cells, their normal function in the organism, their origin, and how they are recovered to produce stem cell lines in culture. As background, the fundamental processes of embryo development are reviewed and defined, since the manipulation of stem cell lines into desired specialized cells employs many of the same events.