Mesenchymal Stem Cells (MSCs): Overview, Properties, Functions & Therapies

Mesenchymal Stem Cells
Human Mesenchymal Stem Cells under Microscope (Image Source: Flickr)

Mesenchymal Stem Cells: Stem cells are the basic building blocks of tissues and organs in the body. It is important to note that there is no single stem cell that gives rise to them but in fact a variety of them coming from different locations in the body and formed at different time periods.

One of the most common type of stem cells is the mesenchymal stem cells (aka MSCs). But what exactly is it? Let’s take a closer look.

How to pronounce Mesenchymal Stem Cells?

Mesenchymal Stem Cells Word Origin: Greek

What are Mesenchymal Stem Cells?

By definition, mesenchymal stem cells are multi-potent cells that are able to differentiate and mature into different types of cells. Mesenchymal cells are characterized[1] by having long and thin bodies and very prominent nucleus.

In terms of size, they are relatively smaller than fibrocytes and are quite difficult to observe in histological sections. And overall morphologically speaking, they appear to have no difference from fibroblasts.

Where are they found?

A group of mesenchymal stem cells is called a mesenchyme and together, they form the undifferentiated “filling” of the embryo. Mesenchymal stem cells (or tissue) have a wide distribution in the body[1].

  • Mesenchymal cells can be isolated from the bone marrow, umbilical cord, adipose tissues, and others.
  • During fetal development, the mesenchymal cells form the connective tissue in developing tissues and organs.
  • During adulthood, mesenchymal connective tissues are only located[1] in the dental pulp.

Properties of Mesenchymal Stem Cells

Like most stem cells, mesenchymal stem cells are capable of self-renewal and differentiation.

  • On one hand, self-renewal is the ability of cells to continuously divide while maintaining its undifferentiated state. By doing this, the stem cell pool can perpetuate throughout the organism’s life.
  • Mesenchymal cells are considered to be multi-potent. Meaning, under certain conditions, whether be it in vitro or in vivo, they are able to mature and differentiate into multiple specialized cells.

Functions of Mesenchymal Stem Cells

Despite its size, the mesenchymal stem cell play a lot of significant roles within an organism. The following are just some of them.

Functions of Mesenchymal Stem Cells
Functions of Mesenchymal Stem Cells (Image Source: frontiersin.org)

1. Suppression of immune cells activation

Aside from being the progenitor of most cells in the body, mesenchymal cells also control the activities of immune cells (i.e. T-lymphocytes, B-lymphocytes, macrophages, mast cells, and neutrophils) during an organ transplant. This is important because it prevents further inflammation and eventual rejection of the transplanted organ.

2. Increase the number of nerve cells

Strikingly, recent studies have revealed that mesenchymal stem cells can also differentiate into nerve cells. This process of differentiation usually happens as a result to a stress response or any related stimuli.

  • Neurons are one of the few cells that when damaged, can no longer regenerate. Hence, the idea of mesenchymal cells opens up the possibility to replace any damaged or lost nerve cells in the nervous system.

3. Reduction of Cell Death

While the process of apoptosis, or programmed cell death, is important for the regulation of some physiological process, too much of it can be damaging for the body. Hence, mesenchymal stem cells are present in order to maintain homeostasis and continually replace lost cells.

4. Secretion of neurotrophic and angiogenic factors

Mesenchymal stem cells secrete both neurotrophic and angiogenic factors which are responsible for stabilizing the extracellular matrix (ECM).

5. Increase synaptic connections

When transplanted into the brain, mesenchymal stem cells promote the reduction of free radical levels and enhance the synaptic connections of damaged neurons. In addition to that, they also increase the number of astrocytes (star-shaped cells associated with the formation of functional synapses). As a result, impulses (messages) are being passed on at a faster speed, hence, reactions are also immediate.

6. Increase the myelination of axons

Myelin sheath is the insulating layer that covers the axons of nerve cells. By further enhancing the myelination of axons, mesenchymal cells (similar with above) further increase the speed at which impulses are passed along.

7. Increase the number of blood vessels and astrocytes in the brain

According to a recent study published in the World Journal of Stem Cells[3], mesenchymal cells are also able to replace and repair any damaged blood vessel in the cerebrum part of the brain. Hence, mesenchymal cells are being viewed as potential therapeutic remedy for stroke patients.

The Mesengenic Process

Mesenchymal cells undergo mesengenic process in order to transform into different cell types such as osteocytes (bone cells), chondrocytes (cartilage cells), muscle cells, and others.

The Differentiation of Mesenchymal Stem Cells into different types of cells
The Differentiation of Mesenchymal Stem Cells into different types of cells (Image Source: frontiersin.org)

  • In this process (shown in the diagram above), the cells undergo proliferation and commitment events following the progression of their progeny into lineages that results to their differentiation.
  • It is important to note that the control of this process provides the principle for designing clinical methods and therapies for the manipulation of mesenchymal stem cells and tissues[2].

Clinical uses of Mesenchymal Cells

Present-day studies are now paving the way for the further applications of mesenchymal stem cells into numerous clinical measures and techniques. In addition to the natural functions of mesenchymal cells mentioned above, several commercialized products from these cells have already been approved.

  • Examples of such are the Caristem and Cupistem (from South Korea) for degenerative arthritis and anal fistula respectively, and the Prochymal (from New Zealand and Canada) for acute GyHD (graft-versus-host-disease).
  • But despite the aforementioned uses, the use of stem cells in general can be quite dangerous. Potential rejection of the introduced cells or the potential failure of the transplant may occur, leading to more serious problems.
  • Being capable of self-renewal and continuous cell division, stem cells are being feared for such characteristics as they may cause the development of cancers and tumors.

Despite their promising effect on overall organism health, the knowledge about mesenchymal stem cells is still incomplete. Hence, further research is still needed to ensure the safety of patients and improve quality control.

Cite this article as: "Mesenchymal Stem Cells (MSCs): Overview, Properties, Functions & Therapies," in Bio Explorer, December 31, 2016, https://www.bioexplorer.net/mesenchymal-stem-cells.html/.

References

  • [1] – Slomianka, Lutz. “Blue Histology – Connective Tissues.” Blue Histology – Connective Tissues. Accessed December 30, 2016. Link.
  • [2] – “The mesengenic process.” Clinics in plastic surgery. Accessed December 30, 2016. Link.
  • [3] – Valenti, Maria Teresa, Antonio Mori, Giovanni Malerba, and Luca Dalle Carbonare. “Mesenchymal stem cells: A new diagnostic tool?” World Journal of Stem Cells. 2015. Accessed December 30, 2016. Link.
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