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Background

The Mesenchymal Stem / Progenitor Cell (MSC/MPC) System

 

 

The mesenchymal stem/progenitor cell system

 

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Mesenchymal stem/stromal cells are fibroblastoid-like, adherent cells that have the capability of differentiating into multiple cell types. The organization of the MSC system may be viewed as similar to that of the blood-forming system. However the MSC system is far less characterized. Although called stem cells, the MSCs are difficult to characterize into individual stem cell populations. In fact, it is unclear whether MSCs represent a stem cell population or whether they are a stromal cell population that can differentiate (see Dominici et al. Cytotherapy 2006, 8:315-317 and Prockop, Clin Pharamcol Therapeut, 2007, 82:241-243). Like lympho-hematopoietic stem cells, MSCs can be detected by cell surface expression markers such as CD90, CD105 and CD73. Mesenchymal stem/stromal cells are usually negative for CD34 and CD45. The ability of MSCs to differentiate into bone (osteoblasts), fat cells (adipocytes), cartilage (chondrocytes), muscle cells and even neural cells has been used in a number of tissue engineering, regenerative medicine and gene therapy applications both in humans and animals, e.g. horses. Mesenchymal stem/stromal cells can be obtained from numerous sources including bone marrow, umbilical cord blood, fat cells and many others. Mesenchymal stem/stromal cells have also been used to produce induced pluripotent stem cells (iPS cells).

Mesenchymal Stem/Stromal Cell Assays - CFU-F and MSCGlo™

Mesenchymal stem/stromal cells represent a proliferating cell population that exhibits a high potential for expansion. As MSCs differentiate, both proliferation ability or "quality" and proliferation potential or potency decrease to zero. When originally derived from a specific cell source from different donors, MSC can exhibit varying degrees of potency. However, the assay commonly used to detect MSC is subjective and cannot be standardized because the assay does not have any external standards or controls. As a result, it is difficult, if not impossible, to compare results over time. This assay is called the Colony-Forming Unit - Fibroblast or CFU-F assay. The assay is usually performed in 35mm or 60mm Petri dishes. The MSCs adhere to the growth surface and form colonies over time. Cell growth can be quite variable. As a result, 3 different cell concentrations are usually plated. It is therefore necessary to pick a cell concentration and an incubation time that allows a sufficient number of distinct and individual colonies to be counted so as to obtain statistical significance, without the culture plate being confluent with cells. This extremely inefficient, time-consuming and costly assay can now be replaced with MSCGlo™-96 Research.

 

Since the MSC is a proliferating population, it follows that MSCs should be detected with a proliferation assay. MSCGlo™ is a part of the HemoGenix® bioluminomics™ family of assays specifically designed to measure MSCs under different conditions. Fast to learn and easy to use, MSCGlo™-96 Research relies on the measurement of the cell's biochemical energy marker, ATP, to provide rapid, reliable and reproducible results. In a strategic partnership with Vitro Biopharma™, HemoGenix® now incorporates MSCGro™ media in all of its MSC assay kits and contract services for MSC. MSCGro™ media demonstrates superior growth and stability properties over virtually any other MSC media available. MSCGro™ Differentiation Media is also available for differentiating MSCs into chondrocytes, adipocytes and osteoblasts.

 

Starting with the original MSC source, the proliferation status and/or potential of:

  • Selected
  • Passaged, and 
  • Expanded

MSCs can be easily measured. Furthermore, MSCGlo™-96 Research has been designed to allow multiplexing, so that phenotypic analysis or gene expression analysis, for example, can be performed on the same sample being measured for proliferation parameters. Mesenchymal stem/stromal cells can either be grown directly in the 96-well plates provided for the assay or can be grown in other culture vessels. If the latter, MSCs can be assayed directly when removed for passaging, providing an almost instant indication of the proliferation status of the cells prior to further plating and expansion.

 

For clinical applications, HemoGenix® has designed two assays to measure human MSC "quality" and potency. MSCGlo™-96 HuQC and MSCGlo™-96 PQR/PRS are based on HALO®-96 SPC-QC and HALO®-96 PQR for human hematopoietic stem cell "quality" and potency for stem cell processing laboratories, respectively. They provide the assurance that the MSCs exhibit the "quality" and potency required prior to patient use. 

 

Mesenchymal stem/stromal cells and cells derived from MSC constitute the hematopoietic stroma or hematopoietic microenvironment, without which hematopoiesis would not occur. This stroma allows and supports the hematopoietic system by forming "niches" in which vital cell-to-cell interaction occurs. Drugs and other agents can damage the stroma thereby causing disregulation of the hematopoietic system. The differentiation of MSCs during tissue engineering and regenerative applications can also be severely affected by agents. It follows that knowledge of whether MSCs and their derived cells react to specific compounds is of special importance. HemoGenix® is the only company that provides specialized MSC toxicity assays for this purpose. Mesenchymal stem cell toxicity assays (MSCGlo™-Tox HT) are available in 96-well format as MSCGlo™-96 Tox and in 384-well plate format for high throughput screening as MSCGlo™-384 HT.