Adult stem cells

Abstract

Development of a multicellular organism is accomplished through a series of events that are preprogrammed in the genome. These events encompass cellular proliferation, lineage commitment, lineage progression, lineage expression, cellular inhibition, and regulated apoptosis. The sequential progression of cells through these events results in the formation of the differentiated cells, tissues, and organs that constitute an individual. Although most cells progress through this sequence during development, a few cells leave the developmental continuum to become reserve precursor cells. The reserve precursor cells are involved in the continual maintenance and repair of the tissues and organs throughout the life span of the individual. Until recently it was generally assumed that the precursor cells in postnatal individuals were limited to lineage-committed progenitor cells specific for various tissues. However, studies by Young, his colleagues, and others have demonstrated the presence of two categories of precursor cells that reside within the organs and tissues of postnatal animals. These two categories of precursor cells are lineage-committed (multipotent, tripotent, bipotent, and unipotent) progenitor cells and lineage-uncommitted pluripotent (epiblastic-like, ectodermal, mesodermal, and endodermal) stem cells. These reserve precursor cells provide for the continual maintenance and repair of the organism after birth. Anat Rec Part A 276A: 75-102, 2004.

Derivation of male germ cells from bone marrow stem cells

“…Much of the excitement centers on embryonic stem cells (ES), but this approach remains controversial for ethical reasons; moreover, routine clinical application of this strategy is many years away. 17,18 By contrast, bone marrow (BM) stem (BMS) cells from adult BM are well characterized and have long been used therapeutically. 17 Accumulated evidence suggests that in addition to haematopoietic stem cells hematopoeitic stem cells, BM also harbors endothelial stem cells (ESC), mesenchymal stem cells (MSC), and multipotential adult progenitor cells.…”

Clonogenic analysis reveals reserve stem cells in postnatal mammals. II. Pluripotent epiblastic‐like stem cells

“…Telomerase activity was detected by polyacrylamide gel electrophoresis of cell lysates from a clone Scl-40␤ at 254 population doublings. Cells were thawed, plated, and expanded in medium containing PDGF-like (proliferative) and ADF-like (anti-differentiative/inhibitory) activities (Young, 2000(Young, , 2003. Cells were harvested and processed for telomerase activity as described (TRAPeze Assay, Intergen).…”

“…K: R-AFP, antibody to rat-specific AFP (Mujoo et al, 1983). L: YM-PS5088, antibody to insulin-secreting ␤-cells (Young, 2003;Young et al, 2003). M: OC4, antibody to liver progenitor cells, biliary epithelial cells, oval cells, and canalicular cells Walborg et al, 1985;Faris et al, 1991;Gordon et al, 2000).…”

The differentiation and transdifferentiation of epithelial cells in vitro – is it a new strategy in regenerative biomedicine?

“…That process involves a large range of cellular signals, growth and transcription factors as a group of uniform cells needs to progress to a number of different collections of more specialized cells, performing their respective function in the adult organism [5]. These pools of cells, so called progenitor cells, occupy specific niches across the body, functioning as a vessel for constant proliferation and differentiation associated with specificity of certain organs or organ systems [7]. They are usually associated with areas that need constant cell replacement, because of their function or location.…”

“…That allows them to function effectively without the need for the extraordinary amount of signaling needed to define a certain tissue from a pluripotent stem cell. There are multiple types of such cells, dependent on the niche in which they function, varying in the degree of their multipotency [7]. For example, unipotent myoblast satellite cells, function in repair and build-up of muscles [8], [9].…”