Plants with Hair Growth Activity for Alopecia: A Scoping Review on Methodological Aspects

Alopecia is a common dermatological disorder of patchy hair loss with substantial patient burden. Phytotherapeutic compounds are increasingly used as a source of new therapeutic options. This review aimed to synthesize the evidence on plant species in hair growth and the methodological aspects of in vivo experimental models. The systematic scoping review was conducted following the PRISMA checklist, the Joanna Briggs Institute, and in accordance with Cochrane. A systematic search was carried out in the Pubmed, Scopus, Web of Science, and SciELO databases. In vivo experiments that evaluated hair growth activity using natural substances of plant origin were included. Data collection and analysis: a total of 1250 studies were identified, of which 175 were included for qualitative synthesis. Of these, 128 used mice, 37 rats, 10 rabbits, 1 guinea pig, and 1 sheep as animal models. The methodologies mapped were as follows: hair growth analysis, histological analysis, immunohistochemistry, gene expression analysis, Western blot, enzyme-linked immunosorbent assay, and biochemical analysis. Minoxidil and finasteride were the most commonly used positive controls. The studies evaluated plant species (166), algae (11), or isolated substances (31). Overall, 152 plant species and 37 isolated substances were identified. This is the first systematic scoping review on the methodological aspects of in vivo hair growth activity. We created a checklist to be completed by authors to allow data comparison and reproducibility, facilitate data interpretation by readers, and ensure better quality of evidence. This work may become a valuable tool for future research and contribute to significant advances in hair growth studies.