In Vivo Models for the Study of Hyaluronic Acid Fillers: A Review.

[BACKGROUND] Hyaluronic acid (HA) filler application is one of the most frequent minimally invasive aesthetic procedures used worldwide. Its properties and characterization, performance, effects in other tissues, and response to complication treatments have been studied in several animal models. This review aims to categorize animal models considering the advantages and disadvantages regarding the purpose of the study.

[METHODS] Literature research was made using MEDLINE via PubMed by two reviewers using keywords "hyaluronic acid" "filler" and "animal model". Full-text articles published in English and with an in vivo animal model were included for data extraction.

[RESULTS] The rat model was the most common animal used to evaluate properties or characteristics and degradation of HA fillers. Rabbits were preferred for evaluating HA embolism treatments; however, anatomical names of the arteries differ in some studies. Mice and rats used as vascular occlusion model are challenging due to the size of the vessels and viscosity of the filler.

[CONCLUSION] There is a wide variability of options of in vivo animal models to evaluate HA fillers. The animal characteristics, laboratory resources, and HA properties should be considered in accordance with the objective of the study, when choosing the ideal model.

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