Autologous Micrografts Containing Nanovesicles, Exosomes, and Follicle Stem Cells in Androgenetic Alopecia: In Vitro and In Vivo Analysis Through a Multicentric, Observational, Evaluator-Blinded Study

background: the use of micrografts (MCGs) containing human follicle mesenchymal stem cells (HF-MSCs) is a hair loss (HL) treatment that needs to be standardized as seems to have promising effects on hair regrowth (HR-G) also thanks to the presence of extracellular vesicles (EVs). objectives: the study aims to report both the in vivo results, obtained in patients affected by androgenic alopecia (AGA) treated using MCGs, and in vitro analysis characterizing the EVs. methods: a multicentric, retrospective, observational, evaluator-blinded study was conducted. eighty-three AGA patients were initially enrolled [52 suffering from male pattern hair loss (MPHL) at stages I–III vertex by the norwood–hamilton scale and 31 suffering from female PHL (FPHL) at stages I–II by the Ludwig scale]. sixty patients (20 females and 40 males) were treated and analyzed after exclusion and inclusion criteria assessment. the in vivo HR-G was evaluated through photography, physician’s, and patient’s global assessment scales, in addition to standardized photo-trichograms, during a follow-up for 1 year, while the in vitro analysis was performed through a quantitative, morphological, and dimensional characterization of the EVs population using transmission electron microscopy (TEM) and fluorescent microscopy. results: a hair density (HD) increase of 28 ± 4 hairs/cm2 at T4 after 12 months in the targeted area (TA) of FPHL, compared with the baseline, was observed using computerized trichograms with a statistically significant difference (SSD) in hair regrowth (HR-G) (p = 0.0429). regarding MPHL, an HD increase of 30 ± 5 hairs/cm2 at T4 after 12 months in the TA was observed with an SSD in HR-G (p = 0.0012). the presence of EVs and their interaction with the surrounding cellular population were demonstrated. conclusions: MCGs containing HF-MSCs and exosomes may fill in as a safe and viable alternative treatment against HL in mild and moderate degrees of AGA both in MPHL and in FPHL. level of evidence III: this journal requires that authors assign a level of evidence to each article. for a full description of these evidence-based medicine ratings, please refer to the table of contents or the online Instructions to authors www.springer.com/00266.