What Are Mesenchymal Stem Cells (MSCs)? Definition, Sources & Uses

Mesenchymal stem cells (MSCs) are adult stem cells found in bone marrow, fat, and umbilical cord tissue that can transform into bone, cartilage, muscle, or fat. MSCs support tissue repair by reducing inflammation and releasing proteins and exosomes that promote healing and control immune responses.

Mesenchymal Stem Cells in Simple Terms

So what makes MSCs special?

They’re multipotent stromal cells—meaning they can become multiple tissue types like bone, cartilage, fat, even muscle cells .

Found in places like bone marrow, fat tissue, dental pulp, synovium, and umbilical cord pulp, making them easier to collect than embryonic stem cells.

Where Do MSCs Come From?

Source

Abundance

How They’re Collected

Common Uses

Bone Marrow (BM‑MSCs)

Moderate

Needle aspiration

Arthritis, orthopedic injuries

Adipose Tissue (ASCs)

High

Liposuction

Joint injuries, soft tissue repair

Umbilical Cord (UC‑MSCs)

Moderate‑high

Wharton’s jelly extraction

Autoimmune, pediatric therapies

Other (dental pulp, placental)

Low

Tissue biopsy

Early research, niche applications

WHAT MATTERS: adipose-derived MSCs are plentiful and less invasive to get than bone marrow. Umbilical cord-derived MSCs are often younger, less immunogenic, and ideal for allogeneic (donor) therapy, though direct human trials comparing them to adult sources are still rare.

How Do MSCs Work?

Let’s break it down into three big roles:

1. Immunomodulation & Anti‑inflammation

MSCs help bring the immune system back to balance by suppressing overactive T cells, B cells, dendritic cells, and macrophages. This helps prevent autoimmune flare-ups and excessive inflammation.

2. Paracrine Signaling via Secretome

Most MSCs don’t stick around long after they’re injected. Instead, they secrete a cocktail of growth factors, cytokines, and exosomes (a.k.a the “secretome”) that jumpstart healing in nearby cells. This appears to be the primary way they work, not by physically turning into new tissue, but by telling other cells to do the job.

3. Tissue Regeneration & Homing

MSCs are naturally drawn to sites of injury or inflammation. Once there, they help support new tissue growth like cartilage, bone, or vascular structures. Unfortunately, survival rates are low – less than 5% stay long-term due to harsh environments or lack of integration.

MSCs in Modern Medicine

To give you a feel for how MSCs are used today, here’s where therapy is making waves:

Orthopedics & Cartilage Repair: Treating arthritis, joint damage, and bone injuries via injection into damaged areas.
Autoimmune Conditions: Offering promise for multiple sclerosis (a reduction in lesion formation and relapses in animal models and early human trials).
Heart & Liver Diseases: Injecting MSCs into cardiac tissue helps reduce scarring and improve function. Early studies in liver fibrosis show reduced inflammation and improved liver cell regeneration.
Wound & Tissue Healing: Chronic wounds, skin grafts, and burns have all seen benefits from localized MSC therapy and exosome-based treatments.

Clinical Trials & Research on MSCs

There’s been a surge of high-quality trials in the last few years. For example, MSCs are now being tested for long‑COVID and acute-on-chronic liver failure—with meta-analyses suggesting real benefits without serious safety concerns. In multiple sclerosis, recent work highlights MSCs’ neuroprotective and anti-inflammatory impact, while also examining key limitations like dosing and delivery methods.

A standout trial is ADMIRE‑CD, which led to approval for darvadstrocel—an adipose‑derived MSC product for treating perianal Crohn’s fistulas in adults. Though later withdrawn in the EU, it’s notable for the rigorous path it took.

Are MSCs Safe & Legal?

Safety Profile

Overall, intravenous and localized MSC treatments have shown a solid safety profile across many conditions. A recent meta-analysis on liver failure patients reported improved liver function and no increased incidence of serious adverse events. And broader reviews reaffirm that MSC infusions are well-tolerated.

Regulatory Landscape

A major milestone occurred on December 18, 2024, when the FDA approved Ryoncil (remestemcel‑L‑rknd), an allogeneic bone marrow–derived mesenchymal stromal cell (MSC) therapy, for steroid-refractory acute graft-versus-host disease (SR-aGVHD) in children aged 2 months and older.

This marked the first FDA-approved MSC therapy. Mesoblast has announced plans to seek expanded approval for adults and other indications, though these are still under development.

Globally, approximately 10 MSC therapies have received regulatory approval, mostly in Asia (notably South Korea and Japan), highlighting the rarity of such approvals.

In July 2025, Florida began permitting some unapproved MSC treatments for uses like pain, orthopedic, and wound care outside FDA pathways, raising oversight and safety concerns.

Organizations such as the ISCT continue to stress the need for rigorous standards governing the quality and attributes of MSC products.

MSCs vs Other Stem Cells

Here’s a quick side-by-side to help readers understand how MSCs stack up:

Comparison Area

Mesenchymal Stem Cells (MSCs)

Hematopoietic Stem Cells (HSCs)

iPSCs / Embryonic Cells (ESCs)

Source & Accessibility

Bone marrow, adipose, cord tissue

Bone marrow, peripheral blood

Reprogrammed adult cells or embryos

Differentiation

Multipotent (bone, cartilage, fat)

Only blood/immune cells

Pluripotent: any cell type

Immunogenicity

Low (esp. allogeneic UC‑MSCs)

Moderate (depends on donor/host match)

Higher risk of rejection or teratoma risk

Regulatory Status

One FDA-approved therapy (Ryoncil)

Established, many approvals

Strictly regulated, some early trials

Typical Uses

Inflammation, tissue repair

Transplants for blood cancers

Disease modeling, experimental therapy

The Future of MSCs

Here’s where things get exciting:

Exosome & Cell-Free Therapies are booming. MSC-derived exosomes may deliver healing signals without needing live cells.

Tissue Engineering & Scaffolds: New studies show MSCs growing on 3D‑printed scaffolds enhance cartilage and bone formation, think next-gen implants for joint repair.

Regulatory Momentum: With Ryoncil cleared, we may see broader FDA acceptance for indications like back pain, heart failure, and autoimmune disease, particularly with favorable policy shifts on federal oversight.

Final Thoughts

MSCs are now more than just a theoretical tool. They’re entering mainstream medicine, backed by solid safety data and real clinical approvals. That said, the landscape is still early stage: efficacy results are promising but inconsistent, and regulatory oversight varies widely from place to place.

As the field evolves, your guide should reflect real-world rigor: clinical evidence, manufacturing standards, and clear visitor guidance on safety and legitimacy. That way, readers can feel informed, not oversold about the evolving promise of MSC therapies.

What Are Mesenchymal Stem Cells (MSCs)?