For example, haematopoietic stem cells can be manipulated in vitro to generate dendritic cells, the most potent antigen presenting cells.ĭendritic cells have a pivotal role in the elicitation and regulation of antigen specific, major histocompatibility complex-restricted T cell responses and are thought to be the only antigen presenting cells able to prime naive T cells. 13 The cytokine milieu and extracellular matrix interaction provides the “road map” for maturation and differentiation of stem cells, 14 which should be instrumental for their in vitro manipulation before therapeutic use. 12 This extracellular matrix has an important role in the facilitation of cell-to-cell interaction, in addition to a more complex role in the binding and presentation of cytokines to the haematopoietic progenitor cells. The bone marrow is a mesenchyme derived tissue consisting of a complex haematopoietic cellular component supported by a microenvironment composed of stromal cells embedded in a complex extracellular matrix. 9 Since umbilical cord blood stem cells can be expanded in vitro or frozen for storage in cell banks 10 they have been used in clinical trials for both autologous and allogeneic haematopoietic stem cell transplantation. In recipients with severe T cell immunodeficiency disorders, fast engraftment is required together with a low risk of graft versus host disease and a low viral transmission rate. 8 Umbilical cord blood stem cells have been used progressively in paediatric patients, from both related and unrelated HLA-matched donors. The use of peripheral blood stem cells in both autologous and allogeneic transplantation has become routine as they can be collected on an outpatient basis and also promote a consistent acceleration in haematopoietic reconstitution after engraftment. 4 Haematopoietic stem cells can be obtained from bone marrow, peripheral blood, 5 umbilical cord blood, 6 and fetal liver. They are known to restore multilineage, long term haematopoietic cell differentiation, and maturation in lethally cytoablated hosts. The best way to define haematopoietic stem cells is from their functional biology. 3 However, pluripotent stem cells constitute only a small fraction of the whole CD34+ population, which is by itself rather heterogeneous regarding phenotype and function. 2 Human haematopoietic progenitor cells, like stromal cell precursors in bone marrow, express the CD34 antigen, a transmembrane cell surface glycoprotein identified by the My10 monoclonal antibody. Haematopoietic stem cells are a somatic cell population with highly specific homing properties and are capable of self renewal and differentiation into multiple cell lineages. In this overview, we briefly discuss the current research and the clinical status of treatments based on haematopoietic and tissue stem cells.Īpplications of cultured haematopoietic stem cells
However, the ability of tissue stem cells to integrate into the tissue cytoarchitecture under the control of the host microenvironment and developmental cues, makes them ideal for cell replacement therapy. This is due to the difficulty of reproducing the necessary and precise three dimensional arrangements and tight cell-cell and cell-extracellular matrix interactions that exist in solid organs. Research into solid tissue stem cells has not made the same progress as that on haematopoietic stem cells. Although early research has focused on haematopoietic stem cells, stem cells have also been recognised in other sites. 1 Stem cells survive well and show stable division in culture, making them ideal targets for in vitro manipulation.
Stem cells are defined as totipotent progenitor cells capable of self renewal and multilineage differentiation.
Stem cell technology is a rapidly developing field that combines the efforts of cell biologists, geneticists, and clinicians and offers hope of effective treatment for a variety of malignant and non-malignant diseases.
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