inducing freezing injury to establish an orofacial muscle fibrosis mouse model

Etablissement d’un modèle de fibrose musculaire orofaciale chez la souris via une lésion par congélation

Orofacial muscles are critical in daily physiological activities such as mastication, speech, respiration, and facial expression1. In congenital orofacial deformities, however, these muscles exhibit atrophic and fibrotic alterations, leading to impaired body health and social cognition2. Facial reconstructive surgery remains the first-line treatment, but up to 30-70% of postoperative patients still suffer from muscle loss and muscle dysfunction3,4 The failure of orofacial muscle regeneration has been attributed to intrinsic factors, which cannot be corrected by surgery alone. 
The emergence of orofacial muscles is an evolutionary novelty, accompanying the complex vertebrate head and chambered heart5,6. Unlike their somite-derived limb counterparts, orofacial muscles originate from the branchial arch7. These phylogenetic and ontogenetical characters may predispose them to distinct regenerative behaviors8. It has been reported that the masseter (MAS) muscle developed severe fibrosis at the time when the tibialis anterior (TA) muscle fully regenerated after exposure to the same extent of injury1,9. However, the underlying mechanism of regeneration remains poorly understood. 
In this study, a freezing injury model of the mice masseter muscle was established to facilitate the investigation into orofacial muscle regeneration. We chose 14 days after injury as the time point for assessing fibrosis phenotype as it was the earliest time point where discernible divergence was detectable between two muscles. Complete regeneration of the MAS after injury requires at least 40 weeks1. Consistently, this study revealed a remarkable deposition of collagen following freezing injury of MAS compared to the regular regeneration of the TA at 14 days post injury. With the help of this model, further mechanistic studies of muscle atrophy and fibrosis can be carried out, which will in turn help the development of potential therapeutic avenues to promote orofacial muscle regeneration after surgery.

Pleins feux sur l’auteur : Explorer la régénération des muscles orofaciaux – Perspectives et innovations

Lésion par congélation dans le muscle masséter de souris pour établir un modèle de fibrose musculaire orofaciale

Current skeletal muscle regeneration studies merely focus on the limb and the trunk muscle, leaving the characteristics and mechanism of orofacial muscle regeneration largely unexplored. The scope of this research is to create and easier and reliable mouse model to facilitate further investigation into muscle regeneration in the orofacial area. Recent developments review that orofacial muscles constitute a unique subset of skeletal muscle with a distinct evolutionary trajectory and developmental origin.They also exhibit different regeneration performances compared with their limb counterparts. A deeper investigation into the orofacial muscle regeneration is warranted to figure out the mechanism underlying these marked differences. The study present a rapid and reproducible method to study orofacial muscle regeneration.The half-freezing injury process took 20 minutes, and the harvest process took only 10 minutes for each mouse, and the mice can tolerate the injury well without any impairment of locomotion. Since our model allows for subsequent comparison between the fibrotic masseter muscle and the fully regenerated tibialis anterior muscle from the aspects of morphology, histology, and molecular regulation, it serves us a power for two for us to delve deeper into the underlying mechanism. Our future research will focus on the causal effects among the alterations of the resident muscle stem cells and multiple niche cells, and correspondingly developed interventions to the process of orofacial muscle fibrosis.

induire une lésion de congélation pour établir un modèle murin de fibrose musculaire orofaciale

Pour commencer, placez la souris anesthésiée sur la table d’opération. À l’aide d’un coton-tige, appliquez la pâte dépilatoire sur la peau, en recouvrant le muscle masséter et le muscle tibial antérieur. Après avoir attendu une à deux minutes, lavez la pâte avec une lingette chirurgicale.Pour exposer le muscle masséter, palpez d’abord le long du bord inférieur de la mandibule. À cinq millimètres du bord, ouvrez la peau le long de la ligne, reliant la commissure buccale au tragus. Pour effectuer la congélation, utilisez une pince pré-refroidie pour tenir un morceau de glace sèche.Placez la glace carbonique le long des axes longs des muscles masséters directement sur la surface du muscle et maintenez la position pendant cinq secondes. Confirmez que le muscle apparaît raide et blanc pâle immédiatement après avoir retiré la glace sèche, puis reprend sa couleur et sa texture normales dans les 22 à 25 secondes. Une fois que le muscle s’est complètement rétabli, fermez la plaie cutanée avec au moins trois sutures 7-0.Pour le muscle tibial antérieur, palper le long du mollet pour localiser le bord antérieur de l’os du tibia. Deux millimètres en arrière du bord, ouvrez la peau, en commençant par le genou et en terminant par la cheville. Pour effectuer la congélation, utilisez une pince pré-refroidie pour tenir un morceau de glace sèche.Placez la glace sèche le long des axes longs des muscles tibiaux antérieurs directement sur la surface et maintenez la position pendant cinq secondes. Confirmez que le muscle apparaît raide et blanc pâle immédiatement après avoir retiré la glace sèche, puis reprend sa couleur et sa texture normales dans les 22 à 25 secondes. Après avoir suturé la plaie cutanée, placez la souris sur une plaque chauffante maintenue à environ 38 degrés Celsius.Surveillez en continu jusqu’à ce que la souris retrouve son réflexe de redressement.

inducing-freezing-injury-to-establish-an-orofacial-muscle-fibrosis

Research

JoVE Journal

Biology

Inducing Freezing Injury to Establish an Orofacial Muscle Fibrosis Mouse Model

Freezing Injury in Mouse Masseter Muscle to Establish an Orofacial Muscle Fibrosis Model

Orofacial muscle constitutes a subset of skeletal muscle tissue, with a distinct evolutionary trajectory and development origin. Unlike the somite-derived ...