An Experimental Study of Tissue Reaction to Hyaluronic Acid (Restylane) and Polymethylmethacrylate (Metacrill) in the MouseRosa, Simone C. MD, MSc*; Macedo, Jefferson L. S. MD, MSc, PhD*; Magalhães, Albino V. MD, PhD†American Journal of Dermatopathology: October 2012 - Volume 34 - Issue 7 - p 716–722 doi: 10.1097/DAD.0b013e3182485c21 Original Study Abstract Author Information Abstract: The aging skin is a challenge for medical science. Plastic surgeons and dermatologists are called every day to solve problems like filling wrinkles or folds. The material used must be biocompatible because abnormal reactions may cause catastrophic results. This study analyzes the biological behavior of polymethylmethacrylate (Metacrill) and hyaluronic acid (Restylane), using a histopathologic study in mice. A prospective study was performed using 40 mice for each substance: polymethylmethacrylate or hyaluronic acid was injected into the right ear, the left ear been used as a control. Histopathologic analyses of the right ear, liver, and kidney were performed at intervals during the study and revealed the development of a granulomatous reaction with fibrosis and absorption of spheres and signs of liver and kidney sistematization for polymethylmethacrylate. A discrete cellular reaction, with less formation of fibrosis, and no giant cells were seen in the mice injected with hyaluronic acid. *Department of pathology, Brazilian Society of Plastic Surgery, Brasilia †University of Brasilia, Brasilia, Brazil. The authors declare no conflict of interest. Reprints: Simone C. Rosa, MD, MSc, SQS 213 Bloco H ap. 104 Asa Sul Brasília, DF, Brazil, CEP 70292-080 (e-mail: firstname.lastname@example.org). © 2012 Lippincott Williams & Wilkins, Inc.