Platelet-rich plasma may represent the best-supported regenerative adjunctive therapy for hair transplantation, whereas exosome-based therapies and other emerging approaches remain investigational because of limited and heterogeneous clinical evidence. The review concluded that standardized protocols and transplantation-specific outcome measures are needed to improve the quality and clinical applicability of future evidence.
Researchers conducted a structured narrative review of English-language studies identified through PubMed/MEDLINE, Scopus, and Google Scholar from database inception through February 2025. Eligible publications included randomized controlled trials, prospective and retrospective clinical studies, systematic reviews, meta-analyses, and translational preclinical studies evaluating regenerative therapies for hair loss or hair transplantation. The review assessed outcomes including hair density, hair shaft diameter, graft survival, hair yield, wound healing, time to visible regrowth, shock loss, and patient-reported satisfaction and quality of life. Because of substantial heterogeneity in study design, interventions, and outcome reporting, the researchers synthesized the evidence narratively rather than performing a meta-analysis.
Among the therapies reviewed, platelet-rich plasma (PRP) had the most mature evidence base. Randomized trials in patients with androgenetic alopecia reported increases in hair density of approximately 10 to 30 hairs/cm² compared with baseline or control groups, and many studies also demonstrated improvements in hair shaft diameter and patient-reported outcomes. However, evidence specific to hair transplantation remained limited, with inconsistent reporting of transplantation-specific endpoints such as graft survival, hair yield, regrowth time, and long-term durability.
The review found that PRP has been incorporated into multiple stages of hair transplantation, including graft preservation, recipient-site preparation, intraoperative infiltration, and postoperative scalp injections. Some prospective and randomized studies reported improvements in early postoperative healing and hair density, but variations in platelet concentration, leukocyte content, activation methods, treatment timing, and outcome assessment limited comparisons across studies and precluded standardized conclusions.
Evidence supporting exosome-based therapies was considerably less developed. Preclinical studies suggested that extracellular vesicles derived from mesenchymal stem or stromal cells may promote dermal papilla cell proliferation, angiogenesis, and signaling pathways involved in hair follicle regeneration. However, the researchers found that clinical evidence was limited to small, heterogeneous studies with substantial variability in product characterization, dosing, delivery methods, and outcome reporting. The review identified no robust randomized trials evaluating exosome therapies as adjuncts to hair transplantation.
The review also evaluated other emerging regenerative approaches, including low-level laser therapy, microneedling-assisted application, photoactivated PRP, and combination treatment protocols. Low-level laser therapy demonstrated moderate evidence in patients with androgenetic alopecia, whereas transplantation-specific data remained limited. Microneedling showed benefit when combined with topical therapies in androgenetic alopecia but lacked standardized protocols in hair transplantation. Evidence supporting photoactivated PRP and combination regenerative approaches was limited, early, and inconsistent.
The researchers emphasized that future studies should prioritize standardized treatment protocols, transplantation-specific outcome measures, objective assessments using trichoscopy and standardized photography, validated patient-reported outcomes, and longer follow-up. They also highlighted pragmatic study designs, including split-scalp and stepped-wedge approaches, as potential strategies for generating more reproducible clinical evidence.
The review was limited by its narrative design, potential selection bias, and the heterogeneity of the included literature. The researchers noted that formal systematic review methods were not fully implemented and that variability in treatment protocols and outcome reporting precluded quantitative evidence synthesis.
Overall, the review suggests that PRP may currently have the strongest evidence among regenerative adjuncts used in hair transplantation, although the researchers cautioned that higher-quality, transplantation-specific studies are needed before emerging therapies can be more broadly incorporated into clinical practice.
“A continued emphasis on protocol standardization and rigorous scientific evaluation will determine which approaches ultimately achieve lasting clinical significance in hair transplantation,” wrote lead study author Abdulaziz Balwi, of Elit Hair GmbH, Berlin, Germany, and colleague.
Disclosures: The authors reported no funding. Balwi serves as president of ElitHair Group, and Koldas works for Elit Klinik Medical Center. The authors also reported using generative artificial intelligence during manuscript preparation.
Source: Frontiers in Medicine
