What Are Muse Cells? A Physician's Guide to Dezawa Muse Cell Therapy

The field of regenerative medicine has witnessed decades of investigation into how the body's own repair mechanisms might be harnessed to support tissue recovery. Among the cellular populations studied, muse cells—multilineage-differentiating stress-enduring cells—represent a distinct class first characterized by Professor Mari Dezawa and colleagues at Tohoku University. Unlike many stem cell types that require laboratory expansion or genetic manipulation, these cells circulate naturally in adult tissues and can be isolated from sources such as bone marrow and adipose tissue. Their defining feature is the expression of the SSEA-3 surface marker and an unusual resilience to stress conditions that would typically damage other cell populations.

This guide examines the published science underlying muse cell research, the mechanisms proposed to explain how intravenously delivered cells might navigate to damaged tissue, and the current state of clinical evidence in humans. Importantly, the majority of human data comes from small, early-stage trials conducted in Japan, and the therapy remains investigational worldwide. Regulatory frameworks vary by country, and in the United States the therapy is not FDA-approved. Patients considering any investigational cellular approach should understand both what the literature suggests and what it does not yet prove.

The Discovery and Isolation of Muse Cells

Kuroda, Dezawa, and colleagues first described muse cells in a 2010 publication in the Proceedings of the National Academy of Sciences. The research team was investigating pluripotent-like cell populations that could be found in adult human tissues without the need for induced reprogramming. They identified a rare subset of mesenchymal cells—comprising roughly one to three percent of cultured bone marrow stromal cells—that expressed the embryonic stem cell marker SSEA-3 and survived prolonged exposure to severe stress conditions. When isolated and cultured under appropriate conditions, these cells demonstrated an ability to differentiate into cell types from all three embryonic germ layers, a property typically associated with embryonic or induced pluripotent stem cells.

Wakao, Dezawa, and colleagues expanded on this characterization in a 2011 PNAS study, demonstrating that muse cells could be collected not only from bone marrow but also from adipose tissue, dermal fibroblasts, and even circulating peripheral blood. The isolation protocol relies on the SSEA-3 marker: cells are subjected to immunomagnetic sorting or flow cytometry to separate the SSEA-3-positive fraction from the larger population of SSEA-3-negative mesenchymal cells. The resulting population retains stress tolerance—cells survive serum deprivation, hypoxia, and other harsh conditions that eliminate most other cell types—and exhibits a gene expression profile distinct from conventional mesenchymal stem cells.

This isolation method does not require the weeks of laboratory expansion typical of mesenchymal stem cell therapies, nor does it involve genetic modification. The cells are collected, sorted, and can in principle be prepared for clinical use relatively quickly. However, the low frequency of muse cells in starting tissues means that obtaining sufficient numbers for therapy requires either large starting volumes or pooling from multiple donors. Published trials have used allogeneic (donor-derived) cells rather than autologous (patient-derived) preparations, in part to address this yield challenge.

How Muse Cells Differ from Mesenchymal Stem Cells

Mesenchymal stem cells, often referred to as MSCs, have been the subject of hundreds of clinical trials over the past two decades. These cells, typically harvested from bone marrow or adipose tissue, are characterized by their ability to differentiate into bone, cartilage, and fat, and they secrete a range of bioactive molecules that modulate inflammation and tissue repair. MSCs do not express SSEA-3 and are generally SSEA-3-negative in standard culture conditions. Most MSC therapies require substantial expansion in culture—growing cells over multiple passages to obtain the tens or hundreds of millions of cells needed for a therapeutic dose.

Muse cells, by contrast, are a rare SSEA-3-positive subset within the broader mesenchymal population. They exhibit pluripotent-like differentiation capacity, meaning they can in experimental settings give rise to ectodermal, mesodermal, and endodermal cell types, not just the mesodermal lineages typical of MSCs. This broader differentiation potential is one reason muse cells have attracted investigational interest, though it remains unclear how much of this laboratory-observed plasticity translates into functional tissue integration in living patients.

Another key distinction lies in homing behavior. While MSCs are known to migrate toward sites of inflammation when delivered systemically, the published literature on muse cells proposes a specific chemotactic signaling axis—discussed in the next section—that may direct intravenously infused cells to areas of tissue damage. Whether this difference confers a therapeutic advantage in humans remains an open question, as direct comparative trials between muse cells and MSCs have not been published. Both cell types remain investigational for the vast majority of clinical applications, and neither is FDA-approved for routine use outside of specific bone marrow transplantation contexts.

The S1P-S1PR2 Homing Mechanism

A central question in any systemically delivered cell therapy is whether and how the cells reach the target tissue. Intravenous infusion places cells into the bloodstream, where they must navigate the circulatory system, extravasate through blood vessel walls, and localize to sites where their regenerative potential might be beneficial. Yamada and colleagues addressed this question in a 2018 publication in Circulation Research, using an animal model to investigate the molecular signals that guide muse cells to damaged tissue.

The study demonstrated that injured tissue releases sphingosine-1-phosphate, a lipid signaling molecule abbreviated as S1P. Muse cells express the S1P receptor subtype 2, abbreviated S1PR2, on their surface. The researchers showed that this S1P-S1PR2 axis acts as a chemotactic gradient: muse cells migrate toward higher concentrations of S1P, which accumulate at sites of acute injury. When the researchers blocked S1PR2 signaling or used cells lacking the receptor, homing was substantially reduced. This mechanism differs from the more general inflammatory signals that attract MSCs and may explain why muse cells have been observed to accumulate in damaged tissues after intravenous delivery in preclinical models.

It is important to emphasize that this homing mechanism was characterized in animal studies, not in human patients. Translating findings from animal models to human physiology involves uncertainties about dose, timing, the severity and type of injury, and individual patient factors that affect how cells distribute in the body. The human trials discussed below did not include detailed imaging or biopsy studies that would confirm whether infused cells successfully reach and engraft in the intended tissues. The presence of a homing mechanism in laboratory models is promising but does not constitute proof that the same biology operates at a clinically meaningful scale in patients.

Published Clinical Evidence: What the Trials Show and Do Not Show

The most cited human data on muse cells come from trials conducted in Japan under the auspices of a cellular product designated CL2020. Noda and colleagues published results in 2020 from a first-in-human safety study involving a small number of patients. The trial was open-label, meaning both patients and investigators knew that active cells were being administered, and the primary objective was to assess whether intravenous infusion of allogeneic muse cells produced serious adverse events. The study reported that the therapy was well-tolerated over a short follow-up period, with no major safety signals. Efficacy was not the primary endpoint, and the small sample size and lack of a control group limit conclusions about whether the cells produced a measurable clinical benefit.

Niizuma and colleagues published a subsequent randomized, double-blind trial in 2023 in the journal Neurology. This study included a control arm and blinded assessment of outcomes. The trial enrolled patients and randomly assigned them to receive either muse cells or a placebo infusion. The primary endpoint showed a modest difference between groups, and the results were not uniformly positive across all measured outcomes. Secondary endpoints and subgroup analyses suggested potential signals of benefit in certain populations, but the authors acknowledged that larger, longer-duration trials would be necessary to determine whether the observed effects represent a reproducible and clinically significant improvement. Importantly, the results underscore a pattern common in early-stage regenerative medicine: initial enthusiasm often gives way to nuanced findings as study quality improves.

To place muse cell data in context, it is worth comparing the evidence base to that of mesenchymal stem cells. Hare and colleagues published a randomized trial in 2009 in the Journal of the American College of Cardiology that evaluated the safety of intravenous allogeneic MSCs. The study demonstrated that the cells could be administered without major adverse events, but efficacy signals were limited. Bartolucci and colleagues reported results from the RIMECARD trial in 2017 in Circulation Research, showing that umbilical-cord-derived MSCs appeared to produce a modest improvement in measured function, with the supported group showing an approximate seven-point mean improvement on a key metric. These MSC studies, like the muse cell trials, involved relatively small sample sizes and short follow-up periods, and the therapy remains investigational and not FDA-approved for the indications studied.

Across all these trials—whether muse cells or MSCs—several themes emerge. First, cellular therapies appear to be reasonably well-studied in carefully selected patient populations when administered by experienced research teams. Serious adverse events are uncommon, though risks such as infusion reactions, immunologic responses, and unintended cell migration cannot be entirely excluded. Second, efficacy signals tend to be modest, variable across individuals, and not always reproduced in larger or more rigorous studies. Third, the mechanisms by which any observed benefits occur remain incompletely understood. Cells may differentiate into functional tissue, secrete bioactive molecules that modulate the local environment, or trigger endogenous repair pathways. Distinguishing among these possibilities requires mechanistic studies that go beyond simply measuring clinical outcomes.

Limits, Unknowns, and the Current State of the Science

Despite the growing body of preclinical and early clinical data, muse cell therapy remains an investigational approach with numerous unanswered questions. The published human trials involve small numbers of patients, short follow-up periods, and limited diversity in terms of the types of conditions studied. Long-term outcomes—what happens to patients five or ten years after receiving cells—are largely unknown. Whether cells persist in the body, integrate into tissues, or are eventually cleared by the immune system has not been definitively established in humans.

Individual variability is another critical consideration. Not every patient in published trials responded in the same way, and factors such as age, baseline health status, the severity and type of tissue damage, concurrent medications, and genetic background may all influence how a person responds to cellular therapy. Predicting which patients are most likely to benefit remains a challenge. Some individuals in the published studies showed measurable changes on laboratory or imaging tests, while others did not, and the reasons for this heterogeneity are not fully understood.

The regulatory landscape adds further complexity. In the United States, cellular therapies that involve more than minimal manipulation or are used for purposes other than their normal physiological function are generally regulated as biological drugs and require FDA approval based on evidence of safety and efficacy from well-controlled trials. Muse cell therapy has not received FDA approval, and patients considering the approach should understand that they are participating in an investigational process. In Japan, regulatory pathways for regenerative medicine products differ, which is why the published trials have been conducted there. Access to investigational therapies in the US typically occurs through clinical trials, expanded access programs, or, in some cases, under regulatory frameworks that allow certain autologous cell therapies to be provided outside of formal trials, provided they meet specific criteria.

Cost and practical logistics also matter. Isolating, sorting, and preparing muse cells requires specialized laboratory facilities and trained personnel. The expense of these services is not covered by insurance in the United States for investigational therapies, and patients should be prepared for out-of-pocket costs that can be substantial. Additionally, because muse cells are rare in starting tissues, obtaining a therapeutic dose may require pooling from multiple donors or processing large volumes of tissue, which raises questions about supply chain, quality control, and donor screening.

Finally, it is essential to recognize that the published literature on muse cells is not uniformly positive. The Niizuma trial, for example, showed modest effects on the primary endpoint and variability across secondary measures. Other studies have reported no significant differences between muse cell-supported and control groups on certain outcomes. This pattern is typical of emerging therapies and underscores the importance of honest communication about what the science does and does not yet support. Overstating the evidence or implying certainty where none exists does a disservice to patients trying to make informed decisions.

Accessing Muse Cell Therapy in the United States

For patients in the United States interested in exploring muse cell therapy, understanding the available pathways is important. The therapy is investigational and not FDA-approved, meaning that access is generally limited to clinical trial participation, expanded access arrangements, or services provided by clinics that operate under regulatory frameworks permitting certain investigational uses. Historically, many patients seeking cellular therapies traveled overseas to countries with different regulatory structures, often incurring the risks and inconveniences associated with international medical travel, including limited follow-up care and difficulty verifying the quality and source of the cells being administered.

In recent years, a growing number of clinics in the United States have begun offering investigational cellular therapies under physician supervision. These programs vary in their structure, the types of cells used, and the regulatory basis under which they operate. Some clinics work with cellular products manufactured and licensed by companies that have obtained regulatory clearance in other jurisdictions, such as Japan, and import or prepare cells according to specific protocols. Others use autologous cells collected and processed from the patient's own tissues.

Dr. Charles Pereyra, MD, provides physician-led screening and evaluation for patients considering regenerative cellular therapies, including those involving muse cells. With clinic locations in Miami, New York, Los Angeles, Austin, and Atlanta, Dr. Pereyra's practice offers consultations to help patients understand whether they may be suitable candidates for investigational therapies, what the current evidence suggests, and what realistic expectations should guide their decision-making. Physician-supervised candidacy evaluation is an essential first step, as not every individual is an appropriate candidate, and contraindications or complicating medical conditions must be carefully assessed.

Accessing investigational cellular therapy in the United States eliminates the need for international travel and allows patients to receive care within the framework of the US medical system, with the continuity of follow-up and oversight that entails. However, it remains critical for patients to understand that investigational means exactly that: the therapy is not proven, results vary widely, and individual outcomes remain uncertain. The decision to proceed should be made in consultation with a knowledgeable physician who can review the published evidence, discuss risks and benefits, and help the patient weigh whether participation in an investigational program aligns with their goals and circumstances.

Are Muse Cells the Same as Stem Cells?

Muse cells are a specific type of stem cell, but they differ from many other stem cell populations. They are SSEA-3-positive, stress-tolerant, and exhibit pluripotent-like differentiation capacity, meaning they can in laboratory settings give rise to cell types from all three embryonic germ layers. Most other adult stem cells, such as mesenchymal stem cells, are more limited in their differentiation potential and do not express SSEA-3. While all muse cells are stem cells, not all stem cells are muse cells. The term "stem cell therapy" encompasses a wide range of cellular approaches, each with different characteristics, sources, and levels of supporting evidence.

How Long Do the Effects of Muse Cell Therapy Last?

The duration of any effects from muse cell therapy is not well-established. Published human trials have followed patients for weeks to months, not years, and long-term outcome data are limited. In animal models, some studies suggest that cells may persist and integrate into tissues for extended periods, while others indicate that cells are cleared relatively quickly. Individual responses vary, and factors such as the underlying condition, the patient's immune status, and the dose and preparation of cells all influence outcomes. No cellular therapy has certain or permanent outcomes, and patients should plan for the possibility of needing additional interventions over time.

Is Muse Cell Therapy FDA-Approved?

No. Muse cell therapy is not approved by the Food and Drug Administration for any indication in the United States. The therapy is investigational, and access typically occurs through clinical trials, expanded access programs, or clinics that provide investigational cellular therapies under physician supervision. Patients considering muse cell therapy should understand that they are participating in an investigational process and that the evidence base, while growing, remains early-stage. Regulatory approval would require larger, controlled trials demonstrating both safety and efficacy across diverse patient populations.

What Conditions Might Muse Cell Therapy Address?

Published preclinical and early clinical research has explored muse cells in a range of investigational contexts, including tissue damage, degenerative processes, and age-related changes. The majority of human data comes from small trials in Japan. Individual conditions and patient circumstances vary widely, and not every person is a suitable candidate. Physician-led screening by providers such as Dr. Charles Pereyra, MD, is essential to determine whether a patient's medical history, current health status, and goals align with participation in an investigational cellular therapy program. The published evidence does not support broad claims of efficacy, and outcomes remain uncertain and highly individual.

At Springs Rejuvenation, stem cell and exosome therapies are used together as part of a personalized regenerative protocol.