Human Mesenchymal Stem Cells (HMSC)

Mesenchymal stem cells (MSCs) are stromal cells characterized by their self-renewal and remarkable ability to differentiate into various cell types. This makes them a valuable tool in regenerative medicine, drug testing, and disease research. They are usually obtained from diverse tissues like umbilical cord, bone marrow, and adipose tissue. However, new sources such as menstrual blood and endometrium have also been found. These sources are favored for their accessibility and potential clinical applications [1].

This article will shed light on mesenchymal stem cell's general characteristics, types, and potential applications in research. Mainly, it will discuss:

1. General attributes of mesenchymal stem cells
2. Mesenchymal stem cells culturing information
3. Different types of mesenchymal stem cells and their salient features
4. Research applications of mesenchymal stem cells

1. General attributes of mesenchymal stem cells

This section will discuss the general properties of mesenchymal stem cells, which include:

Multipotency
MSCs are multipotent stem cells. They have the ability to differentiate into multiple cell types, making them a valuable research tool for regenerative medicine.
Self-renewal
Like other stem cells, mesenchymal stem cells have self-renewing ability, thus maintaining a stable source of stem cells for an extended period.
Immunomodulatory potential
MSCs exert an immunomodulatory effect and thus are used in treating different autoimmune diseases.
Immunogenicity
Generally, MSCs possess low levels of immunogenicity, reducing the risk of immune rejection in transplantation. However, it may vary from type to type.
Availability and accessibility
MSCs can be isolated from various tissues, including bone marrow, adipose tissue, and umbilical cord tissue, making them easily available for research and therapeutic applications.

2. Mesenchymal stem cells culturing information

To effectively manage and handle mesenchymal stem cell cultures, it is imperative to have a comprehensive understanding of the following MSCs cell culturing information. This knowledge will not ease your job but accelerate the advancement of your research pursuits.

Key Points for Culturing Mesenchymal Stem Cells

Doubling Time:	The population doubling time varies among different types of MSCs. It may range from 15.8 to 41. 9 hours [2].
Adherent or in Suspension:	Mesenchymal stem cells are adherent.
Seeding density:	The cell seeding density recommended for MSCs is kept between 1 to 3 x 10⁴ cells/cm². For seeding, cells are rinsed with 1 x PBS (phosphate buffer saline) and incubated with accutase (passaging solution) for approximately 10 minutes at an ambient temperature. After cell detachment, media is added, and cells are centrifuged. Afterwards, the cell pellet is carefully resuspended, and cells are dispensed into a new culture flask containing fresh culture medium.
Growth Medium:	Alpha MEM medium containing 0.1 ng/ml bFGF (Basic fibroblast growth factor), 2.0 mM stable Glutamine, Ribonucleosides, Deoxyribonucleosides, 1.0 mM Sodium pyruvate, and 2.2 g/L NaHCO3 is used for culturing mesenchymal stem cells. Media should be replaced every 2 to 3 days.
Growth Conditions:	Mesenchymal stem cell cultures are kept in a humidified incubator at 37ºC temperature and 5% CO2.
Storage:	Mesenchymal stem cells can be stored in the vapour phase of liquid nitrogen or at below -150 °C for the longer term.
Freezing Process and Medium:	CM-1 or CM-ACF freezing media are used to store mesenchymal stem cells. A slow freezing process is generally adapted, allowing only a 1°C decrease in temperature per minute. This protects the cell's viability.
Thawing Process:	Frozen MSCs are slightly immersed in a water bath pre-set at 37 °C for approximately 60 seconds. Afterwards, fresh culture media is added, cells are resuspended and centrifuged. This step removes freezing media components from cells. The obtained cell pellet is then added to the growth medium, and cells are dispensed into new flasks for culturing.
Biosafety Level:	Biosafety one laboratory is required to handle and maintain mesenchymal stem cell cultures.

3. Different types of mesenchymal stem cells and their salient features

There are many source-based types of mesenchymal stem cells. Three main MSC types are discussed in this section of the article.

3.1 Adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (AD-MSCs) are a type of mesenchymal stem cell extracted from adipose or fat tissue.
They are abundantly present in adipose tissue, and the extraction procedure is relatively easy through a minimally invasive procedure called liposuction.
They are less likely to cause an immune response upon allogeneic transplantation.
These cells exhibit robust adipogenic potential, meaning have a high differentiating tendency into adipocytes (fat cells) compared to other mesenchymal stem cell types.

Human mesenchymal adipose tissue cells (HMSC.AD) at 10x magnification in MSC-2 cell culture medium, and adipogenic differentiation medium stained with Oil-Red-O, highlighting triglycerides as an adipocyte marker.

3.2 Bone marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are harvested from the bone marrow, typically taken from the hip and thigh bone. These non-hematopoietic cells were discovered in 1970 by A.J. Friedenstein.
The extraction procedure for BM-MSCs is painful and more invasive, for instance, bone marrow aspiration.
Bone marrow mesenchymal stem cell transplantation requires close matching with the recipient to reduce the risk of immune rejection.
BM-MSCs possess osteogenic potential. They have a stronger inclination toward differentiating into osteocytes, the bone cells.

At 40x magnification, cells undergoing osteogenic differentiation with Alizarin-Red-S staining to visualize calcium deposits, and at the same magnification, cells undergoing adipogenic differentiation stained with Oil-Red-O.

3.3 Umbilical cord-derived mesenchymal stem cells

Umbilical cord-derived stem cells (UC-MSCs) are obtained from the umbilical cord tissue.
The umbilical cord tissue is readily accessible for stem cell extraction after childbirth.
Like BM-MSCs, umbilical cord stem cells also require recipient-donor HLA matching for transplantation to avoid any immune response.
They exhibit a higher tendency for neural differentiation and, thus, are valuable research tools for neurological research.

4. Research applications of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are widely employed in biomedical research owing to their significant therapeutic potential. A few promising applications of different MSC types are mentioned in this section.

Regenerative medicine research: Mesenchymal stem cells are multipotent cells; they have the potential to differentiate into various cell types such as cartilage, bone, muscle, and fat cells. Therefore, they are administered as regenerative medicine for repairing and substituting injured or damaged tissues. The regenerative applications of MSCs are primarily observed in skin, bone, and musculoskeletal injuries. For instance, a study conducted by Helena Debiazi Zomer and coworkers in 2020 found that mesenchymal stem cells derived from adipose tissues (AD-MSCs) are able to accelerate skin wound healing in mouse models. They stimulate angiogenesis and extracellular matrix remodelling to promote a better-quality scar resembling normal healthy skin than the control group [3]. Research has also observed the bone defect repair properties of umbilical cord-derived mesenchymal stem cells. They exert repairing effects by promoting angiogenesis, osteoclastogenesis, and mobilization of host MSCs or differentiating into osteoblast-like cells [4].
Immune system diseases/disorders: Mesenchymal stem cells exert immunomodulatory effects. They tend to regulate immune responses and reduce inflammation. Therefore, they are employed to treat autoimmune diseases, i.e., rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, etc. For a study explored the immunomodulatory effect of bone marrow-derived mesenchymal stem cells on peripheral blood T cells extracted from rheumatoid arthritis patients. BM-MSC cells exert an inhibitory effect on T cells and suppress cytokines involved in rheumatoid arthritis physiopathology [5].
Neurological and Cardiovascular Research: MSCs hold significant potential for neurological and cardiovascular research applications. They are used to treat several neurodegenerative disorders, including Parkinson's and Alzheimer's disease. Moreover, they are employed in cardiovascular disease treatment as they repair damaged or injured heart tissues after cardiac events. Besides, MSCs also promote angiogenesis and thus are valuable in cardiovascular research. Such a study explored the therapeutic potential of adipose and bone marrow-derived mesenchymal stem cells in an acute myocardial infarction (MI) model. The study found that both sources are equally beneficial in regenerating cardiac tissues and reducing fibrosis [6]. Interestingly, research conducted in 2022 found that human umbilical cord-derived mesenchymal stem cells (UC-MSCs) exert neuroprotective effects in Parkinson's disease mouse models via regulating intestinal microorganisms. The mouse model displayed improved locomotor function after UC-MSCs intranasal transplantation [7].

References

Ding, D.C., W.C. Shyu, and S.Z. Lin, Mesenchymal stem cells. Cell Transplant, 2011. 20(1): p. 5-14.
Zhan, X.-S., et al., A comparative study of biological characteristics and transcriptome profiles of mesenchymal stem cells from different canine tissues. International journal of molecular sciences, 2019. 20(6): p. 1485.
Zomer, H.D., et al., Mesenchymal stromal cells from dermal and adipose tissues induce macrophage polarization to a pro-repair phenotype and improve skin wound healing. Cytotherapy, 2020. 22(5): p. 247-260.
Kosinski, M., et al., Bone defect repair using a bone substitute supported by mesenchymal stem cells derived from the umbilical cord. Stem Cells International, 2020. 2020.
Pedrosa, M., et al., Immunomodulatory effect of human bone marrow‐derived mesenchymal stromal/stem cells on peripheral blood T cells from rheumatoid arthritis patients. Journal of tissue engineering and regenerative medicine, 2020. 14(1): p. 16-28.
Omar, A.M., et al., Comparative Study of the Therapeutic Potential of Mesenchymal Stem Cells Derived from Adipose Tissue and Bone Marrow on Acute Myocardial Infarction Model. Oman Med J, 2019. 34(6): p. 534-543.
Sun, Z., et al., Human umbilical cord mesenchymal stem cells improve locomotor function in Parkinson's disease mouse model through regulating intestinal microorganisms. Frontiers in Cell and Developmental Biology, 2022. 9: p. 808905.