**5. Conclusions**

PRP represents a relatively new therapeutic approach widely used in different areas of dermatology and plastic surgery [19,21,22], although its underlying mechanisms of action are not completely understood. The present meta-analysis proves the valuable role of PRP therapy in AGA for patients of both sexes, but also points to the need for personalized therapeutic indications and approaches. Although the total number of PRP treatments and the amount of PRP injected per treatment do not appear to influence the outcome, an increased frequency of application (number of treatments per month) results in larger increases in hair density. Other important factors are the age of patients and implicitly duration since alopecia onset. For best results it is advisable to apply a complex combined therapy protocol as early as possible.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/jpm12030342/s1, Table S1: Inclusion and exclusion criteria for the clinical trials included in the meta-analysis, Table S2: Methods of PRP preparation, injection and of patient monitoring for the clinical trials included in the meta-analysis, Table S3: Influence of sex composition of study groups on hair density (initial and after PRP treatment).

**Author Contributions:** All authors have equally contributed to this paper. Conceptualization, S.R.G., A.A. and M.T.; methodology, S.R.G., A.A. and C.M.; validation, C.I.M., M.I.M., C.C. and M.N.; formal analysis, A.A., M.T. and C.M.; investigation, A.A., C.I.M. and M.I.M.; resources, C.M.; data curation, C.C. and C.M.; writing—original draft preparation, A.A. and M.T.; writing—review and editing, M.T., C.I.M., M.I.M., C.C. and M.N.; visualization, S.R.G., C.M. and C.C.; supervision, S.R.G., M.N. and M.T.; project administration, S.R.G. and M.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** The article processing charges are funded by Carol Davila University of Medicine and Pharmacy within the project Publish not perish.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Abbreviations**

