Adjunctive regenerative therapies in hair transplantation: a comprehensive review of platelet-rich plasma, exosomes, and emerging methods

Background: Adjunctive regenerative therapies are increasingly used to improve outcomes in hair transplantation; however, evidence remains heterogeneously and variably reported. Objective: To provide a structured, evidence-based narrative review of platelet-rich plasma (PRP), extracellular vesicles/exosomes, and emerging adjunctive therapies in the context of hair transplantation. Methods: A structured literature search was conducted in PubMed/MEDLINE, Scopus, and Google Scholar databases from database inception to February 2025. English-language studies evaluating regenerative therapies in hair loss and hair transplantation were included. Study selection followed predefined inclusion and exclusion criteria, and evidence was synthesized narratively, with emphasis on study design, sample size, quantitative results, and methodological limitations. Results: have been reported in randomized trials, but evidence specific to transplantation is limited and heterogeneous. Exosome-based approaches show preclinical effects on dermal papillary cell proliferation and angiogenesis, but lack robust clinical validation and standardized characterization. Emerging adjuvant therapies, including low-level laser therapy, microneedling-assisted application, and photoactivated PRP, exhibit variable efficacy with limited transplantation-specific data. Conclusion: PRP represents the most evidence-supported adjuvant therapy in hair transplantation, while exosome-based and emerging regenerative approaches are under investigation. Standardization of protocols, quantitative outcome reporting, and transplantation-specific endpoints are necessary to improve clinical translation and quality of evidence.