Pluripotent adult stem cells

Adult stem cells are cells found in a number of differentiated tissues that can self-renew and differentiate (with certain limitations) to give rise to the specialized cell types of the tissue. Adult stem cells may also be able to give rise to specialized cell types of a completely different tissue, a phenomenon known as transdifferentiation or plasticity. However, the presence of pluripotent adult stem cells remains a subject of scientific debate. 

Rietze RL, Valcanis H, Brooker GF, Thomas T, Voss AK, et al. 2001. Purification ofa pluripotent neural stem cell from the adult mouse brain. Nature 412 736-739. 

In a general way, the question about the versatility of adult stem cells comes down to whether the library of genetic instructions is irreversibly changed as cells specialize, and whether some parts then become unusable. This is a fundamental question that scientists have been studying for many years, and the answers are not yet certain. It is also a practical question, since if stem cells from one or more adult tissue are pluripotent, then such cells might be taken from an individual and used to repair and replace any, or at least many, of his or her tissues that are not working correctly. 

Stem cells. Embryonic and adult stem cells are distinguished. Embryonic stem cells are taken from an early stage of the embryo, such as from blastocytes. They are undifferentiated and totipotent. Their potential to differentiate and to form different cell lines is unlimited. Adult stemcells are taken from the blood forming bone marrow, from epithelial cells from the skin and other sources. They are pluripotent. Both, embryonic totipotent and adult pluripotent stem cells can replace functionally differentiated cells and tissues in the body. Stem cells can divide. After division, they may form again a stem cell or proceed to a final, fully differentiated state. 

Stem cells normally are classified, based on their origin and differentiation capacity, as either embryonic or adult stem cells (1). Embryonic stem cells (ESCs) are derived from the inner cell mass of the blastocyst. ESCs can self-renew indefinitely and are pluripotent—(the ability to differentiate into all cell types in the embryo proper). Adult stem cells are undifferentiated (unspecialized) cells that are found in differentiated, or specialized, tissue. They have limited self-renewal capability and generally can only differentiate into the specialized cell types of the tissue in which they reside. These cells function as the reservoir for cell/tissue renewal during normal homeostasis or tissue regeneration. Sources of adult stem cells have been found in most tissues, including bone marrow, blood stream, cornea... 

Differentiation is the developmental process by which early pluripotent cells acquire the features of late-stage, mature cells such as neurons, hepatocytes, or heart muscle cells. Currently, few examples of devised, highly selective, and efficient conditions for stem cell differentiation into specific homogeneous cell types have been reported because of a lack of understanding of stem cell signaling at the molecular level. Small-molecule phenotypic screens provide another means to generate desired cell types in a controlled manner. Several small molecules have been identified by this method that modulate specific differentiation pathways of embryonic or adult stem cells. 

There are two general avenues for stem cell research pluripotent and multipotent stem cells. Pluripotent stem cells are obtained by two methods. One method is to harvest the clusters of cells from the blastocysts of human embryos. Another method is the isolation of pluripotent cells from fetuses in terminated pregnancies. Multipotent stem cells are derived from umbilical cords or adult stem cells. However, because of the specialization of these cells, their potential to develop into a myriad of different cells is limited. 

Another quantum leap for modern biotechnology was the first cloned mammal by Ian Willmut in 1996 (see his quote for Modern Biopharmaceuticals ) by means of somatic cell nuclear transfer (SCNT) -the sheep Dolly . Then, in 2004, the first human embryo was cloned by a team led by Woo Suk Hwang, who was able to obtain pluripotent embryonic stem cells by SCNT of reprogrammed human adult cells. The highly differentiated genetic pro-... 

Verfaillie, C. M. 2002. Adult stem cells assessing the case for pluripotency. Trends Cell Biol. 12 502-508. 

Stem cells, whether derived from embryos, fetuses, or adults, can be simply defined as progeny of cells that are capable of differentiating into different lineages [152], Embryonic stem cells (ESCs) are isolated from the inner cell mass of blastocysts and have the ability to be cultured and maintained in an undifferentiated and pluripotent state, and directed to differentiate into all specific cell types [153,154], A variety of adult stem cells (often referred as progenitor or multipotent cells), including bone marrow-derived mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), adipose-derived stem cells (ADSCs), and neutral stem cells (NSCs), have been found more committed but less pluripotent than ESCs. 

Megan J. Munsie, Anna E. Michalska, Carmel M. O Brien, Alan O. Trounson, Martin R Perta and Peter S. Mountford, Isolation of pluripotent embryonic stem cells from reprogrammed adult mouse somatic cell nuclei. Current Biology, 10 (2000), 989-992. 

There are two types of stem cells embryonic stem cells and adult stem cells. Human embryonic stem cells are thought to have much greater developmental potential than adult stem cells because they are pluripotent, which means they are able to develop into any type of cell. Adult stem cells are multipo-tent, meaning they can become cells corresponding to the type of tissue in which they reside. 

Pluripotency and plasticity are prominent properties of embryonic stem cells. Adult stem cells are thought to be restricted in their differentiation potential to the... 

Induced pluripotent stem cells are the adult cells that have been transformed into pluripotent stem cells through programming. Among adult stem cells, Mesenchymal stem cell is widely used as a multipotent source. Mesenchymal stem cell is derived from bone marrow stroma and can differentiate into a variety of cell types in vitro. Other sources of adult stem cells include the amniotic fluid and placental derived stem cells [29, 30]. 

Adult stem cells, also known as postnatal stem cells, have been isolated from other mesenchymal tissues, such as umbihcal cord blood (Mareschi et al., 2001), fat (Zuk et al., 2001), muscle (Collins et al., 2005), synovium (De Bari et al., 2001), and dental pulp (Gronthos et al., 2000, Miura et al., 2003). Although the cell characteristics of stem cells derived from different tissues are not identical, they all share the two basic properties of stem cells, self-renewal and pluripotency, like the BMSC populations. 

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