inducing freezing injury to establish an orofacial muscle fibrosis mouse model

Etablering af en orofacial muskelfibrosemodel hos mus via en fryseskade

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.

Forfatter Spotlight: Udforskning af orofacial muskelregenerering – indsigt og innovationer

Fryseskade i musetyggemuskel for at etablere en orofacial muskelfibrosemodel

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.

Inducering af fryseskade for at etablere en orofacial muskelfibrose-musemodel

For at begynde skal du placere den bedøvede mus på operationsbordet. Brug en vatpind til at påføre hårfjerningspastaen på huden, der dækker tyggemusklen og tibialis forreste muskel. Efter at have ventet i et til to minutter, vask pastaen væk med en kirurgisk serviet.For at udsætte tyggemusklen skal du først palpere langs underkæbens nedre kant. Fem millimeter fra kanten skal du skære huden op langs linjen og forbinde den orale kommissur med tragus. For at udføre frysning skal du bruge forkølet pincet til at holde et stykke tøris.Placer tørisen langs tyggemusklernes lange akser direkte på overfladen af musklen og hold den i fem sekunder. Bekræft, at musklen fremstår stiv og bleg hvid umiddelbart efter fjernelse af tørisen, og vender derefter tilbage til sin normale farve og tekstur inden for 22 til 25 sekunder. Når musklen er kommet sig helt, skal du lukke hudsåret med mindst tre 7-0 suturer.For tibialis forreste muskel palperes langs læggen for at lokalisere den forreste kant af skinnebenet. To millimeter bagud til kanten, skær huden op, startende fra knæet og slutter ved anklen. For at udføre frysning skal du bruge forkølet pincet til at holde et stykke tøris.Placer tørisen langs de lange akser af tibialis forreste muskler direkte på overfladen, og hold den i fem sekunder. Bekræft, at musklen fremstår stiv og bleg hvid umiddelbart efter fjernelse af tørisen, og vender derefter tilbage til sin normale farve og tekstur inden for 22 til 25 sekunder. Efter at have sutureret hudsåret, placer musen på en varmeplade, der holdes ved cirka 38 grader Celsius.Overvåg kontinuerligt, indtil musen genvinder sin oprettelsesrefleks.

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 ...