Mesenchymal stem cell
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Mesenchymal stem cells or MSCs are multipotent stem cells that can differentiate into a variety of cell types. Cell types that MSCs have been shown to differentiate into in vitro or in vivo include osteoblasts, chondrocytes, myocytes, adipocytes, neuronal cells, and, as described lately, into beta-pancreatic islets cells.
Mesenchymal stem cells have been classically obtained from the bone marrow, and MSC can sometimes refer to marrow stromal cells. While the terms mesenchymal stem cell and stromal cell have been used interchangably, they are increasingly recognised as separate entities as:
(1) MSCs can encompass multipotent cells derived from other non-marrow tissues, such as adult muscle side-population cells or the Wharton's jelly present in the umbilical cord.
(2) Stromal cells are a highly heterogenous cell population consisting of multiple cell types with different potentials for proliferation and differentiation. In contrast, MSCs represent a more heterogenous sub-population of mononuclear progenitor cells possessing stem cell features and specific cell surface markers.
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[edit] Historical background
The presence of clonogenic multipotent cells in the bone marrow was reported in the 1970s (Friedenstein et al.) These stromal cells were reported as colony-forming unit-fibroblasts (CFU-F).
In the presence of osteogenic stimuli such as ascorbic acid, inorganic phosphate and dexamethasone were found to promote the differentiation of stromal cells into osteoblasts. In contrast, the addition of transforming growth factor-beta (TGF-b) induced chondrogenic differentiation.
[edit] Modern culturing of MSCs
The majority of modern culture techniques still take a CFU-F approach, where raw unpurified bone marrow or ficoll-purified bone marrow monocytes are plated directly into cell culture plates or flasks. The "MSCs" are adherent to tissue culture plastic with 24-48 hours. However, recent publications have idenfied non-adherent MSC populations that are not obtained using these culture methods.
Other flow cytometry based methods allow the sorting of bone marrow cells for specific surface markers, such as STRO-1. Flow-purified MSCs are generally more homogenous, possess more of the features of stem cells, have higher rates of adherence, and higher rates of proliferation.
[edit] Features of MSCs
MSCs have a large capacity for self-renewal while maintaining their multipotence. However, the capacity of cells to proliferate and differentiate are known to decrease with the age of the donor, as well as the time in culture.
[edit] See also
[edit] References
Friedenstein AJ, Gorskaja JF, Kulagina NN. Fibroblast precursors in normal and irradiated mouse hematopoietic organs. Exp Hematol. 1976 Sep;4(5):267-74.
