Histomorphometric Changes of the Masseter Muscle of Rats After a Single Injection of Botulinum Toxin Type A

Author(s)

Ramos, Douglas Massoni ; de Brito Silva, Raira ; Canales, Giancarlo de la Torre ; Resende, Luciana ; Esquisatto, Marcelo Augusto Marretto ; Moreira, Nadia Cristina Favaro ; Ernberg, Malin ; Rizzatti-Barbosa, Celia Marisa

• Document type: Journal article
• Source: AESTHETIC PLASTIC SURGERY; v. N/A, p. 8-pg., 2023-08-24.

Abstract

Background It has been reported that botulinum toxin type A (BoNT-A) produces structural changes in masticatory muscles. However, not all histomorphometric parameters affected by BoNT-A parameters have been assessed. This study investigated the histomorphometric changes in the masseter muscle of rats after a single injection of BoNT-A.Methods Forty-four adult animals were randomly divided into control group (n = 22) and BoNT-A group (n = 22). Controls received a single dose of 0.14 mL/kg of saline in masseter muscles, and the BoNT-A group received a 7 U/Kg of BoNT-A. The groups received the same volume of injected substances. Animals were sacrificed on 7th (n = 5), 14th (n = 5), 21st (n = 5), 28th (n = 4) and 90th (n = 3) days post-treatment. Histological masseter tissue slides were obtained from hematoxylin-eosin treatment and analyzed in optical microscopy regarding muscle cross-sectional area, amount of connective tissue and quantity and diameter of myocytes. For statistical analysis, generalized linear models were used to compare the data (ANOVA). In all test, the significance level of 5% was set.Results BoNT-A values of cross-sectional area of the masseter muscle were significantly lower than controls (p < 0.01) throughout the study. Regarding myocytes quantity, BoNT-A subgroups presented higher values than controls (p < 0.0001) since the 14th day until the end of the study; however, the diameter of myocytes was smaller in all BoNT-A subgroups (p < 0.0001) in all assessment points. The amount of connective tissue was higher in BoNT-A subgroups (p < 0.0001) throughout the study.Conclusion A single injection of BoNT-A altered the structure of masseter muscle of rats, regarding its histomorphometric parameters. (AU)

• FAPESP's process: 17/21674-0 - Comparison of the effectiveness of botulinum toxin type A in patients with refractory chronic orofacial pain according to different somatosensory profiles
• Grantee: Giancarlo de La Torre Canales
• Support Opportunities: Scholarships in Brazil - Post-Doctoral