Effects of continuous administration of soft diet masticatory muscles: a histological and immunohistochemical study in mice

• Grant number: 19/06714-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2019
• End date: October 31, 2020
• Field of knowledge: Health Sciences - Dentistry - Oral and Maxillofacial Surgery
• Principal Investigator: Andre Luis Shinohara
• Grantee: Klaryssa Akemi de Araujo Kitamoto
• Host Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil

Abstract

The introduction of a liquid and/or soft diet is mandatory during the recovering period after orthognathic surgery, because of the mechanical restriction of mouth opening and the period of tissue healing. In this context, animal studies have demonstrated that continuous feeding with soft diets may lead to atrophy of masticatory muscles. However, investigation about muscle atrophy and connective tissue surrounding these muscles are poorly explored. Thus, the present study aims to evaluate muscle atrophy and changes on connective tissue surrounding masticatory muscles (masseter and digastric) in mice submitted to continuous administration of soft diet. For this purpose, sixty C57Bl/6 male mice, 6 months old, will be distributed into 2 groups: Control group (CG) - treated with hard diet (conventional food); and Experimental group (EG), treated with soft diet (conventional food diluted in 2:5 of distilled water). All groups will be divided into 3 experimental time points (7, 14 and 30 days) of treatment, being 10 animals for each group and experimental time point. Animals will be weighed once a week until the end of experimental time points. After euthanasia, right and left masseter and digastric muscles will be collected and immediately weighed to obtain the mass density. Characterization on muscle fibers and connective tissue will be done by means different qualitative and quantitative histological analysis. For muscle fibers, histological slides will be stained with H&E and transversal section area will be quantified. Atrophy will be also characterized by means immunohistochemical analysis for MuRF-1 (Muscle Ring Finger-1), which is known as an atrophy marker. For connective tissue, morphological and quantitative analysis will be done by means histological analyses: picrosirius red for collagen fibers, Masson trichrome for all components and Weigert - van Gieson for elastic fibers. Quantitative data will be submitted to statistical analysis following the normality distribution. Finally, it is expected that the body of this work could improve the understanding mechanisms involving masticatory apparatus atrophy in clinical situations.