A Clear, Science-Based Explanation for Patients
The phrase ‘mesenchymal stem cell’ appears everywhere in regenerative medicine. It is used in clinic brochures, academic papers, news articles, and patient forums — but what does it actually mean? This article explains what mesenchymal stem cells are, what makes them biologically distinct, where they are found in the body, and why they have attracted such significant attention in medicine. No prior science background is required.
Start with the Basics: What Is a Stem Cell?
The human body contains approximately 37 trillion cells — and most of them have a fixed identity. Liver cells do liver work. Neurons transmit signals. Red blood cells carry oxygen. They are specialised, and they stay specialised.
Stem cells are different. They retain two defining abilities that most cells lose:
- Self-renewal:the ability to divide and produce copies of themselves over long periods
- Differentiation:the ability to develop into other, more specialised cell types
This combination makes stem cells a kind of biological reservoir — cells that can replenish and repair tissues over time. Different types of stem cells vary in how many different cell types they can become. The most potent (embryonic stem cells) can become virtually any cell in the body. Others are more restricted.
Where Do Mesenchymal Stem Cells Fit?
Mesenchymal stem cells (MSCs) are a type of adult stem cell — they exist throughout life, not just in embryonic development. They belong to a category called multipotent stem cells, meaning they can differentiate into several related cell types, but not all cell types.
Specifically, MSCs can differentiate into:
- Osteoblasts:bone-forming cells
- Chondrocytes:cartilage cells
- Adipocytes:fat cells
- Myocytes:muscle cells (in certain conditions)
- Stromal cells:connective tissue support cells
| Plain-language summary: MSCs are versatile repair and support cells that live in connective tissues throughout the body. They can become bone, cartilage, or fat — and they also help regulate inflammation and support surrounding tissue. |
The History: How Were MSCs Discovered?
Mesenchymal stem cells have a well-documented scientific history. The concept emerged from research in the 1960s and 70s, most notably through the work of Alexander Friedenstein, a Soviet biologist who showed that bone marrow contained a population of cells capable of forming bone and cartilage when transplanted. He called them colony-forming unit fibroblasts.
The term ‘mesenchymal stem cell’ was later popularised by Arnold Caplan, an American biologist, who in 1991 described their multi-lineage potential and proposed them as a therapeutic cell type. Caplan himself later reconsidered the terminology, suggesting ‘medicinal signalling cells’ as a more accurate description of what these cells actually do in vivo — reflecting the field’s growing understanding that their primary therapeutic value lies less in differentiation and more in their signalling functions.
Today, MSC research is one of the most active fields in cell therapy, with thousands of registered clinical trials globally.
Where Are MSCs Found in the Body?
MSCs are not unique to one tissue. They are found in many parts of the body, where they occupy what biologists call a niche — a localised microenvironment that supports their maintenance.
| Source | Notes |
| Bone marrow | The original and most studied source. Requires invasive aspiration from the hip or sternum. Yield decreases significantly with age. |
| Adipose tissue (fat) | Abundant source, accessible via liposuction procedures. Used in autologous (self-donor) approaches. |
| Umbilical cord (Wharton’s jelly) | Ethically obtained from donated birth tissue. High cell yield, high proliferative capacity, and lower immunogenicity than adult sources. Preferred for allogeneic (donor-to-patient) therapy. |
| Placenta | Rich source; research ongoing for therapeutic applications. |
| Dental pulp | Emerging source with interest in craniofacial applications. |
| Peripheral blood | Low concentration; typically mobilised with growth factors before collection. |
Why Are Umbilical Cord MSCs Considered Advantageous?
Among the various sources of MSCs, umbilical cord tissue — specifically the gelatinous Wharton’s jelly within the cord — has emerged as a particularly attractive source for clinical applications. Here is why:
Ethical and Practical Availability
Umbilical cords are routinely discarded after birth. Collecting them from consenting donors is non-invasive and presents no risk to mother or child. This is a significant advantage over bone marrow, which requires a painful and invasive harvesting procedure from living donors.
Superior Proliferative Capacity
UC-MSCs divide more rapidly and can be expanded to higher cell numbers than bone marrow-derived MSCs. This makes manufacturing at therapeutic scale more reliable and cost-effective.
Immunological Profile
A critically important property of UC-MSCs is their relatively low immunogenicity — they are less likely to be recognised and attacked by the recipient’s immune system than adult MSCs. This is due in part to their lower expression of MHC class II molecules (the surface proteins that immune cells use to distinguish self from non-self). This characteristic makes them suitable for allogeneic use: one donor’s cells can potentially be used in many recipients, enabling off-the-shelf treatment rather than personalised autologous cell therapy.
| In practical terms: UC-MSCs can be manufactured in advance, quality-tested, and stored — rather than requiring a fresh harvest from each individual patient before every treatment. |
Neonatal Vitality
Cells from birth tissue are biologically young. UC-MSCs have longer telomeres (the protective end-caps of chromosomes that shorten with age), higher mitochondrial activity, and a more vigorous growth profile than MSCs harvested from adult donors, who may have accumulated oxidative stress or senescent cells.
How Do MSCs Actually Work? The Paracrine Revolution
The early hypothesis about MSC therapy was that injected cells would migrate to damaged areas and physically replace lost tissue. This idea has been substantially revised by subsequent research.
In practice, most transplanted MSCs do not persist long-term in the recipient’s tissues. Many are cleared within days to weeks. Yet therapeutic effects can persist far longer. This apparent paradox is explained by what researchers now call the paracrine hypothesis: MSCs work primarily by releasing bioactive molecules — not by becoming new tissue.
The MSC Secretome
The collection of molecules secreted by MSCs is called the secretome. It includes:
- Growth factors:such as HGF (hepatocyte growth factor), VEGF (vascular endothelial growth factor), and IGF-1, which support cell survival and tissue repair
- Cytokines:signalling proteins that modulate immune cell behaviour, including IL-6, IL-10, and TGF-beta
- Extracellular vesicles:particularly exosomes — nano-sized membrane packets that carry proteins, lipids, and RNA to recipient cells, influencing their behaviour
- Immunosuppressive molecules:such as IDO (indoleamine 2,3-dioxygenase) and PGE2 (prostaglandin E2) that dampen excessive immune responses
| The exosome story: A growing body of research suggests that much of the therapeutic effect attributed to MSCs may actually be mediated by the exosomes they release. This has opened a parallel field of exosome therapy — using cell-derived vesicles without the cells themselves. The field is still early but scientifically significant. |
Context-Sensitivity: MSCs as Responsive Mediators
One of the most interesting properties of MSCs is that their behaviour is shaped by the local environment. In inflamed tissue, they produce more anti-inflammatory molecules. In areas of tissue damage, they upregulate trophic factors. This responsiveness — sometimes described as ‘sensing and responding’ — is part of why they have attracted interest across such a wide range of conditions. They are not a fixed pharmacological dose but a dynamic biological agent.
How Are MSCs Identified? The ISCT Criteria
Because MSCs from different tissues behave somewhat differently, and because the term ‘MSC’ has been applied loosely in the scientific literature, the International Society for Cell and Gene Therapy (ISCT) established minimum criteria for defining a cell population as mesenchymal stem cells. These include:
- Plastic adherence: MSCs must adhere to plastic culture surfaces under standard conditions.
- Surface marker profile: MSCs must express CD73, CD90, and CD105, and must not express CD45, CD34, CD14, CD11b, CD79a, CD19, or HLA-DR.
- Multipotency: MSCs must be able to differentiate into osteoblasts, adipocytes, and chondroblasts under defined in vitro conditions.
These criteria are the baseline. When evaluating any clinical programme, confirming that the cell product meets ISCT identity criteria is an important quality check.
MSCs vs. Other Stem Cell Types: A Quick Reference
| Cell Type | Potency | Source | Clinical Use |
| Embryonic (ESC) | Pluripotent (all cell types) | Embryo | Research; ethical restrictions limit clinical use |
| Induced pluripotent (iPSC) | Pluripotent | Adult cells reprogrammed | Research; manufacturing complexity limits clinical scale |
| Haematopoietic (HSC) | Multipotent (blood cells) | Bone marrow / blood | Bone marrow transplantation; approved clinical use |
| Mesenchymal (MSC) | Multipotent (connective tissues) | Bone marrow, cord, fat, others | Active clinical investigation; some approved indications |
Common Misconceptions About MSCs
- MSC therapy is the same as embryonic stem cell therapy
False. MSCs are adult stem cells — they do not come from embryos. Umbilical cord MSCs come from birth tissue that is donated with consent. The ethical concerns historically raised about embryonic stem cell research do not apply.
- MSCs will grow wherever they are injected and form new tissue
Largely false. Most transplanted MSCs are cleared relatively quickly. Their therapeutic effect is primarily mediated through paracrine signalling rather than direct tissue replacement. This is not a weakness — it is simply how they work.
- All MSC products are equivalent
False. MSCs from different tissue sources have different gene expression profiles, secretome compositions, and functional characteristics. Even within the same source tissue, manufacturing differences (passage number, culture conditions, cryopreservation method) significantly affect potency. Product standardisation is a major focus of ongoing regulatory science.
The Bottom Line
Mesenchymal stem cells are a biologically fascinating and therapeutically promising class of cells. They are not the magic cure-all that they are sometimes marketed as — but they are genuine biological agents with documented immunomodulatory and tissue-supportive properties, backed by decades of scientific investigation and an extensive body of clinical trial data.
Understanding what they are — and are not — is the foundation for evaluating any MSC-based therapy clearly. With that foundation in place, you are better positioned to ask the right questions and assess the credibility of any programme you are considering.
About EDNA Wellness
EDNA Wellness is a surgeon-led regenerative medicine center in Bangkok, specializing in orthopedic and neurological conditions using Umbilical Cord–Derived Mesenchymal Stem Cells (UC-MSCs).
All cases are reviewed by orthopedic surgeons and neurosurgeons, with a focus on clinical indication, patient safety, and realistic treatment expectations. Stem cell therapy is recommended selectively, and alternative treatments are considered when more appropriate.
For more information or to book a consultation:
LINE: @ednawellness
WhatsApp: +66 (0) 64 505 5599
www.ednawellness.com