Self-renewal

A combination of ozone oxidation with simultaneous exposure to ultraviolet light seems to produce a self-renewing chain reaction that can significantly reduce the dose of ozone needed to accomphsh oxidation. 

Lee RH, Hsu SC, Munoz J et al (2006) A subset of human rapidly self-renewing marrow stromal cells preferentially engraft in mice. Blood 107 2153-2161... 

Hematopoiesis is defined as the development and maturation of blood cells and their precursors. In utero, hematopoiesis may occur in the liver, spleen, and bone marrow. However, after birth, it occurs exclusively in the bone marrow. All blood cells are generated from a common hematopoietic precursor, or stem cell. These stem cells are self-renewing and pluripotent and thus are able to commit to any one of the different lines of maturation that give rise to platelet-producing megakaryocytes, lymphoid, erythroid, and myeloid cells. The myeloid cell line produces monocytes, basophils, neutrophils, and eosinophils, whereas the lymphoid stem cell differentiates to form circulating B and T lymphocytes. In contrast to the ordered development of normal cells, the development of leukemia seems to represent an arrest in differentiation at an early phase in the continuum of stem cell to mature cell.1... 

Knowledge gained from cell adhesion studies with SAMs has been used to develop culture substrates with the appropriate cell adhesion glycoproteins for different types of cells [7-10], Stem cells, capable of self-renewal and differentiation into multiple cell types, are found in embryonic and adult tissues. Pluripotent stem cells, like embryonic stem cells and induced pluripotent stem cells, have been developed in vitro. These cells are expected to provide cell sources for regenerative medicine. Various culture conditions have been developed to enable expansion of these cells without loss of their multi- and pluripotency and to induce differentiation into viable cells with specific functions. 

The details of haemopoiesis presented thus far prompt two very important questions (1) How is the correct balance between stem cell self-renewal and differentiation maintained (2) What forces exist that regulate the process of differentiation The answer to both questions, in particular the latter, is beginning to emerge in the form of a group of cytokines termed haemopoietic growth factors . This group includes ... 

The trial entailed retroviral-mediated ex vivo transduction of haematopoietic stem cells from 10 young SCID-X1 sufferers, with subsequent re-infusion of the treated cells. A marked and prolonged clinical response in which the condition was essentially reversed was observed in 9 out of the 10 patients. The prolonged response was likely due to the transduction of pluripotent progenitor cells with self-renewal capacity (Chapter 10). However, the two youngest patients (1 and 3 months old at the time of treatment) developed uncontrolled proliferation of mature T-lymphocytes 30 months and 34 months after gene therapy respectively. 

The therapeutic application of stem cells has long been a dream of medical sciences, but recent discoveries and technical advances have brought this dream somewhat closer to being a reality. Stem cells are usually defined as undifferentiated cells capable of self-renewal that can differentiate into more than one specialized cell type. 

Central nervous system stem cells maintain an undifferentiated state and the capacity to self-renew in response to epidermal growth factor and fibroblast growth factor 507 Cell lineage studies reveal close associations between distinct neural cell types 508... 

An important controversy remains about which factors, intrinsic or extrinsic, control the stem cell s decision to self-renew or develop into one of several committed progenitor cells. Two distinct models have been proposed to... 

Figure 2.1. Development of blood cells. The development of blood cells occurs in the bone marrow. All cells arise from the differentiation of pluripotent or multipotent stem cells, which have the capacity for self-renewal, or else can divide into more mature cells types. The morphological features of the mature blood cell types is shown.

It is believed that all blood cells arise from the division and differentiation of multipotent stem cells. These stem cells have considerable capacity for self-renewal by cell division but may also differentiate into progenitor cells of lymphocytic or myeloid lineages (see Fig. 2.1). Experiments with colony-... 

Figure 2.3. Maturation of bone marrow cells. Stem cells have the capacity for self-renewal, but also differentiate into more mature cell types. As the cells become more mature, their ability to proliferate declines and their number in the marrow increases.

Gerecht S, Burdick JA, Ferreira LS, Townsend SA, Langer R, Vunjak-Novakovic G (2007) Hyaluronic acid hydrogen for controlled self-renewal and differentiation of human embryonic stem cells. Proc Natl Acad Sci USA 104 11298-11303. 

Xi R, Xie T (2005) Stem cell self-renewal controlled by chromatin remodeUng factors. Science 310 1487-1489... 

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