Mesenchymal stem cell – Wikipedia, the free encyclopedia

Mesenchymal stem cells, or MSCs, are multipotent stromal cells that can differentiate into a variety of cell types,[1] including: osteoblasts (bone cells),[2]chondrocytes (cartilage cells),[3] and adipocytes (fat cells). This phenomenon has been documented in specific cells and tissues in living animals and their counterparts growing in tissue culture.

While the terms Mesenchymal Stem Cell and Marrow Stromal Cell have been used interchangeably, neither term is sufficiently descriptive as discussed below:

The youngest, most primitive MSCs can be obtained from the umbilical cord tissue, namely Wharton's jelly and the umbilical cord blood. However the MSCs are found in much higher concentration in the Whartons jelly compared to the umbilical cord blood, which is a rich source of hematopoietic stem cells. The umbilical cord is easily obtained after the birth of the newborn, is normally thrown away and poses no risk for collection. The umbilical cord MSCs have more primitive properties than other adult MSCs obtained later in life, which might make them a useful source of MSCs for clinical applications.

An extremely rich source for mesenchymal stem cells is the developing tooth bud of the mandibular third molar. While considered multipotent, they may prove to be pluripotent. The stem cells eventually form enamel, dentin, blood vessels, dental pulp, nervous tissues, including a minimum of 29 different unique end organs. Because of extreme ease in collection at 810 years of age before calcification and minimal to no morbidity they will probably constitute a major source for personal banking, research and multiple therapies. These stem cells have been shown capable of producing hepatocytes. Additionally, amniotic fluid has been shown to be a very rich source of stem cells. As many as 1 in 100 cells collected from and genetic amniocentesis has been shown to be a pluripotent mesenchymal stem cell.[citation needed]

Adipose tissue is one of the richest sources of MSCs. When compared to bone marrow, there is more than 500 times more stem cells in 1 gram of fat when compared to 1 gram of aspirated bone marrow. Adipose stem cells are currently actively being researched in clinical trials for treatment in a variety of diseases.

The presence of MSCs in peripheral blood has been controversial. However, a few groups have successfully isolated MSCs from human peripheral blood and been able to expand them in culture.[7]

In 1924, Russian-born morphologist Alexander A. Maximow used extensive histological findings to identify a singular type of precursor cell within mesenchyme that develops into different types of blood cells.[8]

Scientists Ernest A. McCulloch and James E. Till first revealed the clonal nature of marrow cells in the 1960s.[9][10] An ex vivo assay for examining the clonogenic potential of multipotent marrow cells was later reported in the 1970s by Friedenstein and colleagues.[11][12] In this assay system, stromal cells were referred to as colony-forming unit-fibroblasts (CFU-f).

Subsequent experimentation revealed the plasticity of marrow cells and how their fate could be determined by environmental cues. Culturing marrow stromal cells in the presence of osteogenic stimuli such as ascorbic acid, inorganic phosphate, and dexamethasone could promote their differentiation into osteoblasts. In contrast, the addition of transforming growth factor-beta (TGF-b) could induce chondrogenic markers.[citation needed]

Mesenchymal stem cells are characterized morphologically by a small cell body with a few cell processes that are long and thin. The cell body contains a large, round nucleus with a prominent nucleolus, which is surrounded by finely dispersed chromatin particles, giving the nucleus a clear appearance. The remainder of the cell body contains a small amount of Golgi apparatus, rough endoplasmic reticulum, mitochondria, and polyribosomes. The cells, which are long and thin, are widely dispersed and the adjacent extracellular matrix is populated by a few reticular fibrils but is devoid of the other types of collagen fibrils.[13][14]

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Mesenchymal stem cell - Wikipedia, the free encyclopedia