Mesenchymal Stem Cells (MSC): The Science Behind Regenerative Therapy

What are mesenchymal stem cells?

Mesenchymal stem cells (MSCs), more formally mesenchymal stromal cells, are multipotent adult progenitor cells originally identified in bone marrow by Alexander Friedenstein in the 1970s. They are not embryonic — they exist in adult tissues throughout the body and are responsible for the routine maintenance and repair of connective tissue, bone, cartilage, tendon, and fat. They are also one of the most studied cellular populations in the history of regenerative medicine, with thousands of registered clinical trials evaluating their use in orthopedic, autoimmune, cardiovascular, and degenerative conditions.

Unlike hematopoietic stem cells (which produce blood lineages), MSCs sit in the stromal compartment of tissues and exert their effects largely by signaling, not by replacement. They are plastic-adherent in culture, can be expanded into clinically relevant numbers under controlled laboratory conditions, and can be cryopreserved for later use. This combination — accessibility, expandability, and a documented safety profile — is why they have become the most clinically translated stem cell type in the world.

Importantly, MSCs are not a single cell type with a single behavior. Cells derived from umbilical cord tissue behave differently from cells derived from bone marrow or fat. Donor age matters, passage number matters, processing matters. A clinic that talks about "stem cells" without specifying which population and from which source is glossing over the variable that most influences clinical effect — and that distinction is exactly what this page is about.

How MSCs work — signaling, not differentiation

The most common misconception about stem cell therapy is the idea that MSCs travel to damaged tissue and "become" the cells that were lost. This is mostly not what happens. The current scientific consensus, supported by more than two decades of mechanistic research, is that MSCs work primarily through paracrine signaling — they secrete factors that change the behavior of the cells already present in the tissue.

• Paracrine secretome. MSCs release a continuous mixture of growth factors (VEGF, HGF, IGF-1, TGF-β), cytokines, and chemokines that recruit local progenitor cells, dampen chronic inflammation, and stimulate angiogenesis. This "secretome" is the active pharmacology of MSC therapy and is now an area of research in its own right.
• Exosomes and extracellular vesicles. A meaningful share of the MSC paracrine effect is delivered through extracellular vesicles — small membrane-bound packages of microRNA, lipids, and proteins. Exosome-based therapeutics are an active research arm precisely because they isolate the signaling without the cells.
• Immunomodulation. MSCs interact with both arms of the immune system: they shift macrophages toward a pro-resolution M2 phenotype, suppress over-activated T cells, and induce regulatory T cells. This is the core mechanism behind their use in autoimmune and inflammatory conditions, and the reason allogeneic protocols are clinically feasible.
• Limited direct differentiation. MSCs can differentiate into bone, cartilage, and fat lineages in vitro, but the in-vivo evidence that infused MSCs engraft and become new tissue at scale is weak. Marketing language that frames therapy as "replacing damaged cells" is not consistent with the current published literature. The honest framing is signaling and immunomodulation.

The practical implication is that MSC therapy works best when the underlying tissue still has repair capacity — when there is a biology to nudge. It is most useful as a modulator of an active disease process, not as a substitute for tissue that no longer exists.

Sources we use: where the cells come from

Three sources dominate clinical practice today. Each has trade-offs in cell yield, donor age, immune profile, and processing burden. The right source for a given patient is a medical decision driven by indication, age, and the goals of the protocol.

MSC sources at a glance

Regeneris uses Wharton's jelly UC-MSCs from a COFEPRIS-registered laboratory chain for most allogeneic protocols, and autologous BM-MSC or AD-MSC when the indication and patient profile justify it. The choice is never arbitrary.

ISCT minimum criteria for MSC identification

Because "stem cell" is a loose term used by everyone from researchers to wellness marketers, the International Society for Cell & Gene Therapy (ISCT) published in 2006 a three-part minimum definition for what counts as a mesenchymal stromal cell. A reputable laboratory characterizes every batch against these criteria.

1. Plastic-adherent under standard culture conditions. MSCs must attach to tissue culture plastic when maintained in standard culture conditions. This is the operational starting point for isolation and expansion.
2. Surface marker expression. Positive for CD73, CD90, and CD105 (≥95% of the population). Negative for CD45, CD34, CD14 or CD11b, CD79α or CD19, and HLA-DR (≤2%). Verified by flow cytometry on each release lot.
3. Trilineage differentiation in vitro. Cells must be able to differentiate into osteoblasts (bone), adipocytes (fat), and chondroblasts (cartilage) under appropriate induction conditions. Documented during the laboratory's potency assays.

A clinic that cannot tell you whether its cells meet the ISCT criteria — and on what assays — is asking you to take their word. Ask for the Certificate of Analysis (CoA) for the lot that would be used in your protocol.

Conditions MSCs are being studied for

MSC therapy is investigational for most indications. The published evidence is strongest for some, emerging for others, and preliminary for many more. We list below the indication classes we routinely evaluate, with the honest caveat that mechanism is more established than efficacy in many cases.

• Knee and joint osteoarthritis. Strongest peer-reviewed evidence base. Randomized trials report meaningful symptomatic and functional improvement, often lasting 12–24 months. Frequently combined with PRP or hyaluronic acid. See our knee osteoarthritis program.
• Lumbar and cervical spine pain. Used as an adjunct to interventional pain medicine in disc-related and facet pain after conservative therapy plateaus. Indication is patient-specific and imaging-driven.
• Autoimmune conditions. Lupus, rheumatoid arthritis, Hashimoto's thyroiditis, multiple sclerosis — evaluated jointly with the patient's specialist. MSC immunomodulation rationale is mechanistically clear; clinical evidence is heterogeneous and case selection matters.
• Sports and overuse injury. Tendinopathy, partial tears, and post-surgical recovery in athletes and active adults. Often combined with PRP and structured rehabilitation.
• Long COVID and chronic post-viral inflammation. Emerging research area. Mechanism (immunomodulation, dampened chronic inflammation) maps to the proposed pathophysiology; clinical data is early.
• Hair restoration and dermatology. MSC-conditioned media and exosomes for androgenetic alopecia and skin rejuvenation — typically as adjuncts to PRP and topical therapy.

If your condition is not on this list, that does not mean MSCs are not relevant — it means we evaluate case by case and prefer to be honest about what the literature supports.

Safety profile

Across more than two decades of clinical research, MSCs have demonstrated one of the cleanest safety profiles in the cellular therapy field. Meta-analyses of allogeneic MSC trials have not identified an increased risk of tumor formation, acute infusion reactions are uncommon and typically self-limited, and rejection — the immune-mediated destruction that defines transplantation medicine — has not been a clinically significant problem for properly sourced allogeneic cells.

The reason for the low immunogenicity is biological. MSCs express low levels of HLA class I, essentially no HLA class II, and a set of immunomodulatory factors that actively dampen the recipient immune response. This is not a marketing claim; it is the consensus position across the published literature and the basis for the entire allogeneic MSC industry. The clinical consequence is that off-the-shelf Wharton's jelly UC-MSCs can be administered without HLA matching in screened patients.

That said, safety is conditional on sourcing and process. The risks that do exist — infectious disease transmission from an inadequately screened donor, bacterial contamination from a non-sterile process, batch variability from poor quality control — are entirely supply-chain risks. They are filtered out by donor screening, by laboratory accreditation, and by Certificate-of-Analysis review per lot. A regulated supply chain is what makes the safety profile of the published trials transferable to a clinical patient.

Quality control at Regeneris

Every batch of cells used at Regeneris goes through a documented release process before it is approved for clinical use. We treat this paperwork as part of the protocol, not as a back-office detail.

• Flow cytometry characterization. ISCT-aligned panel — CD73+, CD90+, CD105+ (positive markers ≥95%) and CD45−, CD34−, CD14−, CD19−, HLA-DR− (negative markers ≤2%). Run on every release lot.
• Viability assay. Trypan blue or 7-AAD viability assessment. Lots are released only if viability meets the laboratory's pre-set threshold for the cell type and passage in question.
• Sterility and endotoxin testing. USP <71> or equivalent sterility test plus limulus amebocyte lysate (LAL) endotoxin assay. No lot is released with a positive sterility result or an endotoxin value above the pharmacopeial limit.
• Mycoplasma screening. PCR-based mycoplasma testing on the master and working cell banks, in line with regulatory expectations for cellular therapeutics.
• Identity and passage tracking. Each lot is traceable to the donor and the passage number. Cells used clinically are kept at low passage to preserve potency.
• Certificate of Analysis (CoA) per dose. Every dose administered is accompanied by a Certificate of Analysis summarizing the above. Patients can request a copy for their records.

Frequently asked questions

Mesenchymal stem cell therapy is investigational for many indications. Evidence varies by condition. Individual results vary, and individualized medical evaluation is required before any protocol is recommended. This page is for educational purposes and does not constitute medical advice.