The goal of this protocol is to establish an orofacial muscle fibrosis model. Comparison of the histology between mice masseter and tibialis anterior muscle after freezing injury confirmed masseter muscle fibrosis. This model will facilitate further investigation into the mechanism underlying orofacial muscle fibrosis.
Orofacial muscle constitutes a subset of skeletal muscle tissue, with a distinct evolutionary trajectory and development origin. Unlike the somite-derived limb muscles, the orofacial muscles originate from the branchial arches, with exclusive contributions from the cranial neural crest. A recent study has revealed that regeneration is also different in the orofacial muscle group. However, the underlying regulatory mechanism remains to be uncovered. Current skeletal muscle regeneration models mainly focus on the limb and trunk muscle. In this protocol, dry ice was used to induce freezing injury in the mouse masseter muscle and tibialis anterior muscle to create an orofacial muscle fibrosis model. The temporal dynamics of muscle satellite cells and fibro-adipogenic progenitors were different between the two muscles, leading to impaired myofiber regeneration and excessive extracellular matrix deposition. With the help of this model, a deeper investigation into muscle regeneration in the orofacial area could be carried out to develop therapeutic approaches for patients with orofacial diseases.
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.
There are a variety of injury models for studying skeletal muscle regeneration, including the use of physical, chemical, and surgical stimuli10,11,12,13,14,15,16. Cardiotoxin and barium chloride are the two most widely used chemicals to initiate muscle regeneration10<…
The authors have nothing to disclose.
This study was supported by grants from the Sichuan Provincial Health and Wellness Committee (Grant Number: 21PJ063) and the National Natural Science Foundation of China (Grant Number: 82001031).
1 mL syringe | Shifeng Medical Apparatus and Instrument (Chengdu, Sichuan, China) | 1-ml syringe | / |
Acetone | Chron Chemicals | Aceton | / |
Adhesion microscope slides | Citotest Scientific | 188105 | / |
Animal depilatory | Phygene Scientific | PH1877 | / |
BSA (bovine serum albumin) | Solarbio Life Sciences | A8010 | / |
DAPI | Solarbio Life Sciences | C0065 | / |
Donkey anti-goat Alexa Fluor 488 | Abcam | ab150129 | 1:200 |
donkey serum | Solarbio Life Sciences | SL050 | / |
Dry Ice | Sinrro Technology (Chengdu, Sichuan, China) | rice-shaped dry ice | / |
IFKine Red Donkey anti-rabbit | Abbkine Scientific Company | A24421 | 1:200 |
Insulation barrels (big) | Thermos | D600 | / |
Insulation barrels (small) | Polar Ware | 250B | / |
Isoflurane | RWD Life Technology Company (Shenzhen, Guangdong, China) | R510-22 | / |
Isopentane | MACKLIN | M813375 | / |
Laminin | Sigma-Aldrich | L9393 | 1:1000 |
Liquid nitrogen | Sinrro Technology (Chengdu, Sichuan, China) | / | / |
M.O.M kit | Vector Laboratories | BMK-2202 | |
Mice | Dashuo Biological Technology Company(Chengdu, Sichuan, China) | 5 weeks old | / |
mounting medium | Solarbio Life Sciences | S2100 | / |
Nertral balsam | Solarbio Life Sciences | G8590 | / |
Pax7 | Developmental Studies Hybridoma Bank | Pax7 | 1:5 |
Pdgfra | R&D systems | AF1062 | 1:40 |
Sirus Red Staining Kit | Solarbio Life Sciences | G1472 | / |
Surgical instruments (forceps, scissors, needle holder, scalpel, and suture) | Zhuoyue Medical Instrument (Suqian, Jiangsu, China) | / | / |
Tissue-tek OCT | Sakura | 4583 | / |
Triton | Shanghai Scigrace Biotech | ABIO-Biofroxx-0006A | / |
Zoletil | Virbac | Zoletil 50 | / |