What cell therapy actually is, and is not.

The phrase "stem cell" covers at least five different kinds of cells with wildly different abilities, risk profiles, and regulatory treatment. When a clinic says "stem cell therapy" without specifying which cell, in what preparation, from what source, they are either being sloppy or deliberately opaque. Most of what is actually offered in the regenerative-medicine clinics you've heard of is not, strictly, a stem-cell therapy at all.

The two most common preparations in legitimate clinics today are mesenchymal stromal cells (MSCs) and the extracellular vesicles they secrete (often called exosomes). MSCs are adult cells, sourced most often from umbilical-cord tissue donated after a healthy birth, or from the patient's own adipose or bone marrow. They are emphatically not embryonic stem cells, which are a different category with a different legal and ethical history and are not used in any COFEPRIS- or FDA-authorized clinical program for the indications discussed on this site.

MSCs do not, for the most part, become new tissue. They do not turn into cartilage the way you'd grow a new fingernail. Their role is closer to that of a dispatch center: they sense damaged tissue, park nearby, and secrete a complicated soup of signals that instruct the body's existing repair machinery to do its job better. This is called paracrine signaling, and it is the mechanism most of the evidence actually supports.

The honest limit: we do not, in 2026, fully understand the dose-response curve, the optimal route of administration for every indication, or why some patients respond dramatically and others not at all. Anyone who tells you otherwise is selling.

The useful mental model is not "new cells build new tissue." It is "your existing cells get a memo." MSCs and exosomes carry a payload of cytokines, growth factors, and small RNAs that do three things well: they dampen chronic inflammation, they recruit local progenitor cells to repair sites, and they modulate the behavior of the immune system.

This is why the same preparation can plausibly help a knee joint, a post-viral inflammatory state, and a neurological condition with an autoimmune component, it is not treating the indication directly. It is shifting a biochemical environment. It is also why the therapy is systemic on an IV route and local on an injected route, and why we argue with clinics that administer both the same way regardless of target.

The time course matters. MSCs themselves clear from circulation within roughly fourteen days. The downstream effects, the quieter inflammation, the improved biomarker trajectory, the symptom relief, commonly persist three to six months in patients who respond. Maintenance infusions every three to six months (two to four per year) are how we hold that state for chronic conditions.

The honest limit: paracrine signaling is real and measurable, but "signal" is not "cure." For degenerative processes with tissue already lost, late-stage osteoarthritis with bone-on-bone contact, neurological disease with significant neuronal death, the signal cannot rebuild what's gone. It can, in many cases, slow the curve.

Not all cell-therapy claims are equal. It is useful, if uncomfortable, to separate them into three buckets.

Strong evidence. Intra-articular MSC injections for symptomatic knee osteoarthritis show consistent pain and function improvement in multiple randomized trials and meta-analyses. IV MSCs for steroid-refractory graft-versus-host disease and certain acute inflammatory conditions (including severe COVID-19 ARDS) have regulatory approvals in several jurisdictions. Hematopoietic stem-cell transplants, a different and older branch of the field, have been standard care for certain blood cancers for four decades.

Mixed evidence. IV MSCs for autoimmune and inflammatory conditions (Crohn's, multiple sclerosis, certain cardiomyopathies) show promise in phase-II trials but inconsistent results at larger scale. The biology is plausible; the protocols are not yet standardized. Many patients improve; we cannot yet predict reliably which ones.

Speculative. "Anti-aging" longevity claims, IV cell therapy for late-stage neurodegenerative disease (advanced Alzheimer's, advanced Parkinson's), most cosmetic applications, and cell therapy for conditions with no inflammatory or regenerative component. The biology is often not even plausible for some of these.

The honest limit: a clinic that offers the same protocol for chronic pain, autism, autoimmune disease, and aging is not practicing medicine. They are pattern-matching on hope. Our candidacy list is narrow on purpose.

Every month we decline patients for whom the therapy cannot help. It is the least enjoyable part of the job and the most important one. A short, non-exhaustive list of what cell therapy, as it exists in 2026, cannot do:

It cannot rebuild what's gone. Late-stage osteoarthritis with bone-on-bone contact needs a joint replacement. Stage 4 cartilage defects are a surgical problem. Cells do not regrow a meniscus that was removed ten years ago.

It cannot reverse neurodegeneration. We do not, despite what some clinics advertise, treat advanced Alzheimer's, advanced Parkinson's, or ALS. For earlier-stage disease with documented inflammatory contribution there is sometimes a narrow case; for most patients with these diagnoses, there is not. We say no more than we say yes.

It cannot cure autoimmune disease. It can, in some patients, meaningfully quiet it. That is a different claim and we hold to it.

It cannot make you live longer. No published evidence supports that claim. Longevity branding is marketing, not medicine, and we keep those words off our joint and neuro programs for that reason.

It cannot replace a proper diagnosis. If you've been told you need a surgical workup, get the workup. If you haven't had imaging, get imaging. If the clinic you're considering doesn't ask for these things, that is the red flag.