Abstract
Background
Exosomes are small extracellular vesicles with potential roles in modulating the hair growth cycle and are an emerging therapy for patients with alopecia. In recent years, researchers have made significant progress in deciphering the network of cellular interactions and signaling pathways mediated by the transfer of exosomes. This has opened the door to a wide range of potential therapeutic applications with an increasing focus on its application in precision medicine.
Aim
To evaluate current published evidence, both preclinical and clinical, on the use of exosomes for hair restoration.
Methods
In January 2023, a systematic search was conducted using PubMed, Embase, and the Cochrane Library. Records were identified, screened, and assessed for eligibility as per the PRISMA guideline.
Results
We identified 16 studies (15 preclinical and 1 clinical) showing varying degrees of efficacy using exosomes derived from sources including adipose-derived stem cells (ADSCs) and dermal papilla cells (DPCs). Applications of exosomes isolated from ADSCs (ADSC-Exo) and DPCs have shown early promising results in preclinical studies corroborated by results obtained from different model systems. Topical ADSC-Exo has been tried successfully in 39 androgenetic alopecia patients demonstrating significant increases in hair density and thickness. No significant adverse reactions associated with exosome treatment have been reported thus far.
Conclusions
Although current clinical evidence supporting the use of exosome treatment is limited, there is a growing body of evidence suggesting its therapeutic potential. Further studies are warranted to define its mechanism of action, optimize its delivery and efficacy, and to address important safety concerns.
1. INTRODUCTION
Hair loss attributed to non-scarring alopecia, such as androgenetic alopecia (AGA) or alopecia areata (AA), represents a significant source of disease and psychological burden to patients of all ages. There is a need for new and innovative therapies that offer sustained hair regrowth over extended durations with minimal side effects.
Previous studies have shown the potential efficacy of stem cell therapies derived from the adipose tissue in inducing significant hair growth in AGA and AA patients; similar results were also observed using extract of secreted proteins containing exosome and other extracellular vesicles (EVs).
Exosomes are small (30–150 nm) cargo-delivering EVs that mediate intercellular communications. They are characterized by a phospholipid bilayer with specific surface markers and cargos that affect cell signaling and gene expression (e.g., cytokines, growth factors and regulatory microRNAs [miRNAs]). Although its exact mechanism of action is unclear; it is suspected that exosomes, through modulations of paracrine signaling, can mediate the crosstalk between epithelial cells and mesenchymal cells during the hair growth cycle.
For example, exosomes derived from dermal papilla cells (DPCs; DPC-Exos) were shown to upregulate the Wnt/β-catenin pathway in outer root sheath cells (ORSCs), resulting in the telogen-to-anagen transition in mice.
The present review covers the current landscape of exosome treatment in hair restoration, with a focus on preclinical, clinical, and safety data reported thus far in the literature. Issues concerning the safety of exosome treatment, as well as future directions, are discussed.
2. MATERIALS AND METHODS
An electronic search was conducted in January 2023 using PubMed, Embase (Ovid), and the Cochrane Library, without date or language restrictions. We aimed to investigate published evidence pertaining to the use of exosomes for hair growth. Items identified using the following search/MeSH terms were combined: “exosome,” “alopecia,” “hair follicle,” “dermal papilla cell,” “root sheath,” and “Wnt pathway.” Reference sections of relevant review articles were screened for additional records. Deduplication and screening of identified records were performed using Rayyan (https://www.rayyan.ai/). Studies were excluded if a mixture of EVs was used, and if the observed effects could not be attributed to the exosome fraction. This review was designed in concordance with the PRISMA guideline.
3. RESULTS AND DISCUSSION
Following the initial identification of 255 search results, 16 articles were eligible for data extraction. Of the 15 preclinical studies, information on source, content and target of exosomes, as well as any observed genotypic and/or phenotypic effects are summarized in Table 1. Results from 1 clinical study of 39 patients are summarized in Table 2. No randomized or controlled trials were found.
3.1 Preclinical Evidence
Favorable effects have been observed using exosomes derived from a variety of cell types, including adipose-derived stem cells (ADSCs), which increase hair growth and dermis thickness in vivo, potentially through paracrine regulation of DPCs.
Similar functions were observed for DPC-Exos, including induction of human hair follicle growth and acceleration of the telogen-to-anagen transition in mice, potentially through upregulation of fibroblast growth factor and β-catenin pathways.
DPCs may function as a paracrine regulator of hair follicle stem cells (HFSCs) and ORSCs. Interestingly, exosomes from ORSCs exhibited reciprocal effects on DPCs.
Other sources include myeloid-derived suppressor cells and amniotic fluid stem cells. Platelet-derived exosomes (PRP or platelet lysate) showed limited efficacy in some studies. Delivery systems such as microneedle patches may improve efficacy.
miRNAs within exosomes play a key role in regulating hair growth. Some miRNAs promote hair growth (e.g., miR-181a-5p, miR-218-5p), while others inhibit it (e.g., miR-22-5p).
3.2 Clinical Evidence
Exosomes are not currently approved by the U.S. FDA for hair disorders. A case series of 39 AGA patients treated with ADSC-derived exosomes showed improvements in hair density and thickness after 12 weeks of topical treatment using microneedle rollers.
However, randomized controlled trials are lacking. Another case series using EV mixtures showed partial hair growth in 64.5% of patients, but effects could not be attributed specifically to exosomes.
3.3 Safety
Limited safety data exist. No serious adverse reactions were reported in AGA patients treated with topical ADSC-derived exosomes. Mild side effects such as injection site reactions, erythema, edema, dryness, and mild hyperpigmentation were observed in some studies.
Subcutaneous MSC-derived biologics containing EVs also showed no major adverse effects.
Preclinical studies indicate that exosomes may localize in organs such as liver, kidneys, brain, and lungs without major toxicity, although immunological changes (e.g., elevated immunoglobulins and CD8+ T cells) were observed.
Long-term risks such as tumorigenesis and metastasis remain unclear.
3.4 Regulatory Concerns
The U.S. FDA has issued alerts against exosome products. Exosomes are regulated as drugs and biologics, but no approved marketed exosome therapies exist.
Challenges include:
- Lack of standardization in isolation and characterization
- Heterogeneity of exosome populations
- Limited detection methods for functional components (e.g., miRNAs)
- Manufacturing and contamination risks (e.g., Mycoplasma)
Good Manufacturing Practice (GMP) compliance is essential.
3.5 Future Directions
Future improvements may include:
- Optimizing formulation, dosing, and delivery
- Use of topical formulations to improve compliance
- Combination therapies (e.g., minoxidil, PRP, stem cells)
- Advanced delivery systems such as microneedles and ultrasound
- Enhancing exosome production (e.g., phototherapy, plant extracts, engineered vesicles)
- Exploring alternative sources (e.g., bovine colostrum, plant-derived vesicles)
Microneedle patches and nanovesicle technologies show promise in improving delivery and efficacy.
Conclusion
Exosome-based therapies show promising potential for hair restoration, supported by preclinical and limited clinical evidence. However, significant challenges remain in terms of safety, standardization, regulatory approval, and large-scale clinical validation. Further research and clinical trials are required to establish their role in routine treatment of alopecia.
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