Reviewed Evidence
Reviewed Study 1: Exosomes Derived From Bone Marrow Mesenchymal Stromal Cells Promote Remyelination and Reduce Neuroinflammation in the Demyelinating Central Nervous System Authors: Zhang J, Buller BA, Zhang ZG, et al. Publication & Date: Experimental Neurology. 2022;347:113895. DOI / Link: https://doi.org/10.1016/j.expneurol.2021.113895 | PubMed
Reviewed Study 2: Intranasal Delivery of Mesenchymal Stem Cell-Derived Exosomes Ameliorates Experimental Autoimmune Encephalomyelitis Authors: Wu J, Li A, Shi Y, et al. Publication & Date: International Immunopharmacology. 2025;146:113853. DOI / Link: https://doi.org/10.1016/j.intimp.2024.113853 | PubMed
Reviewed Study 3: Exosomes Derived From Mesenchymal Stem Cells Repair a Parkinson’s Disease Model by Inducing Autophagy Authors: Chen HX, Liang FC, Gu P, et al. Publication & Date: Cell Death & Disease. 2020;11(4):288. DOI / Link: https://doi.org/10.1038/s41419-020-2473-5 | PubMed
Reviewed Study 4: Extracellular Vesicles From Adipose Mesenchymal Stem Cells Target Inflamed Lymph Nodes in Experimental Autoimmune Encephalomyelitis Authors: Turano E, Scambi I, Bonafede R, et al. Publication & Date: Cytotherapy. 2024;26(3):276-285. DOI / Link: https://doi.org/10.1016/j.jcyt.2023.12.007 | PubMed
Supporting Publications
Supporting Publication 1: Transport of Extracellular Vesicles Across the Blood-Brain Barrier: Brain Pharmacokinetics and Effects of Inflammation Authors: Banks WA, Sharma P, Bullock KM, Hansen KM, Ludwig N, Whiteside TL Publication & Date: International Journal of Molecular Sciences. 2020;21(12):4407. DOI / Link: https://doi.org/10.3390/ijms21124407 | PubMed
Supporting Publication 2: Intranasal Administration of Extracellular Vesicles Derived From Adipose Mesenchymal Stem Cells Has Therapeutic Effect in Experimental Autoimmune Encephalomyelitis Authors: Rossi B, Virla F, Angelini G, et al. Publication & Date: Cells. 2025;14(15):1172. DOI / Link: https://doi.org/10.3390/cells14151172 | PubMed
Scientific Review By: Michael Healey, M.Ed., C.A.S.
Executive Summary & Key Takeaways
- Primary Objective: Evaluate how mesenchymal stem cell paracrine signaling may influence neuroinflammation in Parkinson’s disease and multiple sclerosis research models, particularly through exosomes and effects on the blood-brain barrier.
- Evidence Reviewed: Six preclinical studies were reviewed, including experimental models of MS-like demyelination, Parkinson’s disease, and studies tracking how extracellular vesicles move through the body and whether they reach the brain and spinal cord.
- Key Finding: MSC-derived extracellular vesicles reduced inflammatory signaling, supported myelin repair and nerve-cell survival, and influenced blood-brain barrier function in experimental models. Some studies also reported CNS localization after intravenous delivery. However, the strength of that evidence varies substantially by labeling and detection method, route, inflammatory state, timing, and vesicle product used.
- Safety and Tolerability: The studies primarily evaluated mechanisms and experimental efficacy and did not establish human safety, tolerability, or long-term risks.
Study Overview & Clinical Objectives
For patients researching mesenchymal stem cell paracrine signaling, this independent review examines whether MSC-derived secretome products can cross or influence the blood-brain barrier (BBB) and, if they do, how they may affect neuroinflammation.
The MSC secretome includes soluble proteins, neurotrophic factors, cytokines, and extracellular vesicles. Of these, exosomes and other extracellular vesicles have the strongest experimental evidence for reaching or influencing central nervous system tissue.
Five of the six studies evaluated MSC-derived exosomes or extracellular vesicles using different cell sources, disease models, and delivery routes. Zhang used exosomes from rhesus monkey bone marrow MSCs, Chen used human umbilical cord MSC exosomes, Turano and Rossi studied adipose MSC-derived EVs, and Wu used bone marrow MSC-derived exosomes. Banks separately evaluated blood-to-brain transport of 10 non-MSC exosome populations and provided supporting evidence that extracellular vesicles may cross the BBB under normal and inflammatory conditions.
Because source, dose, route, tracking method, disease model, and timing differed substantially, the findings cannot establish one common BBB-transport mechanism. Bias-control procedures also differed across studies. Chen used random assignment, blinded data collection and analysis, and an a priori power calculation, while comparable procedures were not consistently described across the full evidence set.
Biological Mechanism & Science
The proposed neuroinflammation mechanisms of mesenchymal stem cells are increasingly understood as paracrine rather than replacement effects. MSCs release soluble mediators and extracellular vesicles that may transport proteins, lipids, and regulatory RNA to immune, vascular, and neural cells.
Banks and colleagues provide important background on extracellular-vesicle transport. Ten exosome populations entered the brain from the bloodstream, but some crossed at rates more than 10 times higher than others. Exposure to lipopolysaccharide, or LPS, increased uptake of six populations and decreased uptake of one. These changes remained after correction for BBB leakage with co-injected radiolabeled albumin, indicating that LPS altered transport independently of simply disrupting the barrier. None of the vesicles were MSC-derived, so direct extrapolation to MSC exosomes remains uncertain.
Zhang studied rhesus monkey MSC exosomes in experimental autoimmune encephalomyelitis (EAE), an MS-like disease model, and in a cuprizone demyelination model. In the EAE model, exosomes or PBS were given intravenously twice weekly for four weeks beginning on day 10 after immunization. The authors reported that MSC exosomes crossed the BBB and were internalized by CNS parenchymal cells as early as four hours after IV administration. The detection method for this localization finding is not specified, which limits direct comparison with studies using explicitly described tracking methods. Treatment also shifted microglia toward an M2-relative-to-M1 phenotype, altered related inflammatory cytokine signaling, inhibited TLR2/IRAK1/NF-κB signaling, and promoted oligodendrocyte development and remyelination.
In the separate cuprizone demyelination model, exosomes were given intravenously once weekly for two weeks beginning when the cuprizone diet was withdrawn. This part of the study provided additional evidence on remyelination rather than the same BBB-transport experiment used in EAE.
Wu evaluated intranasal bone marrow MSC exosomes in EAE mice. Treatment improved tight-junction integrity in the brain and spinal cord and reduced molecules involved in inflammatory-cell adhesion. The study showed increases in ZO-1, occludin, and claudin-5 and reductions in ICAM1 and VCAM1 in bEnd3 brain endothelial cells. Notably, treatment did not alter T-cell differentiation in the spleen, arguing against a purely systemic T-cell mechanism.
Key Findings & Neurological Outcomes
Zhang provides evidence for systemic MSC-EV delivery, reduced neuroinflammation, and remyelination. Its BBB-crossing finding came specifically from the EAE model, where inflammatory disease may already have altered barrier function.
Chen provides another finding suggesting that intravenously administered exosomes can reach the central nervous system. In a 6-OHDA rat model of Parkinson’s disease, human umbilical cord MSC exosomes were given through the tail vein every three days for eight weeks. In a separate localization experiment with three animals per group, fluorescently labeled exosomes were detected in the substantia nigra 24 hours after IV administration. However, the fluorescent dye used in the study, PKH67, can sometimes produce a signal even when intact extracellular vesicles are not present, and the study did not include a free-dye control. The finding therefore supports possible CNS entry but is less conclusive than methods that directly track the vesicles themselves. Treatment was also associated with less dopaminergic neuron loss and apoptosis, higher striatal dopamine levels, improved rotational behavior, and activation of autophagy-related pathways. The 6-OHDA model reproduces dopaminergic injury but does not capture the full progressive biology of human Parkinson’s disease.
Turano provides an important counterpoint using a more specific iron-labeling and ultrastructural approach. Researchers administered a single intravenous dose of USPIO-labeled adipose MSC-derived EVs at EAE onset. The dose contained 40 µg of EV protein, corresponding to approximately 6.07 × 10⁸ particles. At 48 hours, Prussian Blue histology in four EAE mice treated with USPIO-EVs identified labeled vesicles in lymph nodes but not in the lungs or spinal cord. No EV signal was detected in lymph nodes of healthy mice, supporting inflammation-dependent localization. Spleen assessment was limited by naturally high iron content.
A separate transmission electron microscopy analysis of lymph nodes and spinal cord from two EAE mice and two healthy mice independently supported lymph-node localization and the lack of spinal-cord detection. In another experiment using human adipose MSC-EVs rather than the iron-labeled vesicles, flow cytometry identified EV uptake by immune cells in inflamed lymph nodes. The clearest increase occurred in macrophages, while uptake was also observed in dendritic cells and CD4+ T cells.
Taken together, Zhang, Chen, and Turano illustrate why biodistribution findings cannot be interpreted solely as positive versus negative. Chen used PKH67 fluorescence, which carries known labeling limitations. Turano used iron labeling, Prussian Blue histology, and TEM with a separate USPIO control. The studies also differed in disease model, exposure time, and dosing schedule, preventing a direct one-to-one comparison.
Rossi used intranasal adipose MSC-EVs in EAE. Therapeutic protocols used 5 µg per administration, either three doses every four days or 10 consecutive doses beginning at disease onset. A separate USPIO-EV localization experiment showed signals in inflamed brain regions after intranasal delivery, while no specific signal was observed in healthy mice. Because this route can exploit direct nose-to-brain pathways, the findings support inflammation-directed CNS localization rather than conventional blood-to-brain BBB transit.
Clinical Data Summary
| Study Metric | Study Specification |
|---|---|
| Study Type | Six independent preclinical studies; no human MSC-secretome clinical trial |
| Disease Models | EAE and cuprizone demyelination; 6-OHDA Parkinson’s model; experimental BBB transport |
| MSC/EV Sources | Rhesus monkey bone marrow, human umbilical cord, adipose, and bone marrow MSC-derived products; Banks evaluated non-MSC exosome populations |
| Reported Sample Details | Chen: n=12 per treatment group; separate BBB-localization experiment n=3 per group; Turano histology: n=4 EAE/USPIO-EV and n=3 healthy, with the USPIO-alone control-arm n not reported consistently across sections; Turano TEM: n=2 EAE and n=2 healthy; Rossi: 20 mice per condition in the principal therapeutic experiment; Zhang sample size not listed |
| Representative EV Dose | Chen: 200 µg EV protein; Turano: 40 µg EV protein, approximately 6.07 × 10⁸ particles; Rossi: 5 µg per therapeutic intranasal administration; Zhang and Wu: dose not listed |
| Dosing Schedule | Zhang: IV twice weekly for 4 weeks in EAE and weekly for 2 weeks after cuprizone withdrawal; Chen: IV every 3 days for 8 weeks; Turano: single IV administration at EAE onset with biodistribution assessed at 48 hours; Rossi: 3 intranasal doses every 4 days or 10 consecutive doses; Wu: schedule not listed |
| Characterization/Tracking | Zhang: early CNS localization reported, detection method not specified; Chen: PKH67 fluorescence; Turano: USPIO labeling, Prussian Blue histology, and TEM; Rossi: USPIO/MRI localization; Banks: radiolabeled transport studies |
| Endpoint Timing | Zhang reported CNS entry as early as 4 hours; Chen localization at 24 hours; Rossi localization MRI at 3 hours; Turano biodistribution at 48 hours |
| Evidence Summary | Biological activity is supported, but direct CNS trafficking varies by model, route, product, inflammatory state, dosing strategy, and detection method |
Stemedix Clinical Context
From a clinical perspective, the evidence supports continued investigation of mesenchymal stem cell paracrine signaling, not treatment certainty.
The direct answer to “Do MSC secretomes cross the blood-brain barrier, and how?” is that some MSC-derived exosomes and extracellular vesicles have reached or influenced CNS tissue in experimental models, but this has not occurred consistently across studies. Their ability to reach the brain appears to depend on the vesicle product, inflammatory state, delivery route, dose, timing, and detection method. The studies reviewed here do not establish one common transport mechanism.
Once they reach or influence the CNS, preclinical models suggest MSC-derived vesicles may reduce neuroinflammation by altering microglial activity, inflammatory signaling, BBB regulation, remyelination, autophagy, and neuronal survival. These mechanisms have not yet been established through human clinical trials.
Research into MSC-derived trophic factors in neurodegenerative disease also identifies factors such as BDNF and NGF as biologically relevant components of MSC signaling. The reviewed evidence does not demonstrate that these free factors, or the secretome as a whole, independently cross an intact human BBB at therapeutically meaningful concentrations.
Evidence for systemic EV entry into the CNS remains mixed and depends heavily on how localization was measured. Zhang reported CNS entry in inflamed EAE after repeated IV treatment, although the detection method for that localization finding is not specified. Chen also reported substantia nigra localization after IV administration, but that finding relied on PKH67 fluorescence in three animals per group at a single 24-hour timepoint without a reported free-dye control.
Turano used a more specific tracking method, labeling the vesicles with iron particles that could be detected by tissue staining and electron microscopy. After a single IV dose at the start of EAE, labeled vesicles were found in the lymph nodes of four treated mice but not in the lungs or spinal cord 48 hours later. A separate electron microscopy analysis in two treated EAE mice and two healthy controls also found no labeled vesicles in the spinal cord. No lymph-node signal was seen in healthy mice, suggesting that inflammation may affect where the vesicles travel. The authors also noted that IV delivery may limit how many vesicles leave the bloodstream and reach the central nervous system, and suggested intranasal delivery as a possible alternative.
Intranasal studies by Wu and Rossi examine how a different route may facilitate CNS access without conventional blood-to-brain transport. Overall, these findings establish plausible experimental mechanisms, not proven improvements in relapse control, disability, motor function, or disease progression in people with MS or Parkinson’s disease.
Frequently Asked Questions
How do MSC secretomes reduce neuroinflammation according to clinical trials?
The studies reviewed here are primarily preclinical rather than human clinical trials. In experimental models, MSC-derived exosomes and extracellular vesicles reduced neuroinflammatory signaling through mechanisms including changes in microglial activity, NF-κB-related signaling, blood-brain barrier function, remyelination, and neuronal-survival pathways. Human clinical trials are still needed to determine whether these mechanisms translate into meaningful neurological benefits in patients.
Do MSC secretomes cross the blood-brain barrier, and how?
Some MSC-derived exosomes and extracellular vesicles have reached or influenced CNS tissue in experimental models, but this has not occurred consistently across studies. Their ability to reach the brain appears to depend on the vesicle product, inflammation, delivery route, dose, timing, and detection method. The evidence does not show that the entire MSC secretome uniformly crosses the BBB.
What are the main mesenchymal stem cell mechanisms involved in neuroinflammation?
Preclinical studies suggest MSC-derived signals may influence neuroinflammation through extracellular-vesicle signaling, microglial polarization, inflammatory pathways including TNF-alpha-related signaling, BBB function, oligodendrocyte activity, remyelination, and neuronal-survival mechanisms.
What role do MSC-derived trophic factors play in neurodegenerative disease?
Neurotrophic factors such as BDNF and NGF may contribute to neuronal survival and repair signaling. The reviewed studies do not establish that these free factors independently cross an intact human BBB at therapeutic concentrations after systemic MSC administration.
Are there Parkinson’s clinical trials on stem cell immunomodulation?
The Parkinson’s evidence reviewed here is preclinical and does not establish stem cell immunomodulation in human clinical trials. Chen and colleagues evaluated MSC-derived exosomes in a 6-OHDA rat model and reported neuroprotective and autophagy-related findings, along with possible CNS localization after intravenous administration. The study did not directly evaluate cytokine, microglial, or T-cell immunomodulatory endpoints. No human trial of MSC immunomodulation in Parkinson’s disease is evaluated in this review.
Do MSC exosomes need to cross the BBB to reduce neuroinflammation?
Not necessarily. Turano’s lymph-node findings support the possibility of peripheral immune effects, while Wu found improvement in EAE without changes in splenic T-cell differentiation. Other studies support direct CNS localization, suggesting that central and peripheral mechanisms may differ by product and route.
Regulatory Disclaimer
Stemedix provides this review for educational and informational purposes only and represents an academic commentary on published literature. The featured studies evaluate experimental procedures and primarily preclinical models. Regenerative cell therapies and extracellular vesicle therapies discussed are non-FDA-approved treatments unless explicitly stated otherwise. Consult a board-certified physician before making medical decisions.
References
1. Zhang J, Buller BA, Zhang ZG, et al. Exosomes derived from bone marrow mesenchymal stromal cells promote remyelination and reduce neuroinflammation in the demyelinating central nervous system. Exp Neurol. 2022;347:113895. doi:10.1016/j.expneurol.2021.113895. https://pubmed.ncbi.nlm.nih.gov/34653510/ 2. Wu J, Li A, Shi Y, et al. Intranasal delivery of mesenchymal stem cell-derived exosomes ameliorates experimental autoimmune encephalomyelitis. Int Immunopharmacol. 2025;146:113853. doi:10.1016/j.intimp.2024.113853. https://pubmed.ncbi.nlm.nih.gov/39700966/ 3. Chen HX, Liang FC, Gu P, et al. Exosomes derived from mesenchymal stem cells repair a Parkinson’s disease model by inducing autophagy. Cell Death Dis. 2020;11(4):288. doi:10.1038/s41419-020-2473-5. https://pubmed.ncbi.nlm.nih.gov/32341347/ 4. Turano E, Scambi I, Bonafede R, et al. Extracellular vesicles from adipose mesenchymal stem cells target inflamed lymph nodes in experimental autoimmune encephalomyelitis. Cytotherapy. 2024;26(3):276-285. doi:10.1016/j.jcyt.2023.12.007. https://pubmed.ncbi.nlm.nih.gov/38231166/ 5. Banks WA, Sharma P, Bullock KM, Hansen KM, Ludwig N, Whiteside TL. Transport of extracellular vesicles across the blood-brain barrier: Brain pharmacokinetics and effects of inflammation. Int J Mol Sci. 2020;21(12):4407. doi:10.3390/ijms21124407. https://pubmed.ncbi.nlm.nih.gov/32575812/ 6. Rossi B, Virla F, Angelini G, et al. Intranasal administration of extracellular vesicles derived from adipose mesenchymal stem cells has therapeutic effect in experimental autoimmune encephalomyelitis. Cells. 2025;14(15):1172. doi:10.3390/cells14151172. https://pubmed.ncbi.nlm.nih.gov/40801605/
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