inducing freezing injury to establish an orofacial muscle fibrosis mouse model

Establecimiento de un modelo de fibrosis muscular orofacial en ratones a través de una lesión por congelación

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.

Autor destacado: Explorando la regeneración del músculo orofacial - Perspectivas e innovaciones

Lesión por congelación en el músculo masetero de ratón para establecer un modelo de fibrosis muscular orofacial

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.

Inducción de una lesión por congelación para establecer un modelo de ratón de fibrosis muscular orofacial

Para comenzar, coloque el ratón anestesiado en la mesa quirúrgica. Con un bastoncillo de algodón, aplique la pasta depilatoria sobre la piel, cubriendo el músculo masetero y el músculo tibial anterior. Después de esperar uno o dos minutos, lave la pasta con una toallita quirúrgica.Para exponer el músculo masetero, primero palpa a lo largo del borde inferior de la mandíbula. A cinco milímetros del borde, corte la piel a lo largo de la línea, conectando la comisura oral con el trago. Para realizar la congelación, use pinzas preenfriadas para sostener un trozo de hielo seco.Coloque el hielo seco a lo largo de los ejes largos de los músculos maseteros directamente sobre la superficie del músculo y manténgalo durante cinco segundos. Confirme que el músculo se ve rígido y de color blanco pálido inmediatamente después de quitar el hielo seco, y luego vuelve a su color y textura normales dentro de 22 a 25 segundos. Después de que el músculo se recupere por completo, cierre la herida de la piel con al menos tres suturas 7-0.Para el músculo tibial anterior, palpa a lo largo de la pantorrilla para ubicar el borde anterior del hueso de la tibia. Dos milímetros después del borde, corta la piel, comenzando desde la rodilla y terminando en el tobillo. Para realizar la congelación, use pinzas preenfriadas para sostener un trozo de hielo seco.Coloque el hielo seco a lo largo de los ejes largos de los músculos tibiales anteriores directamente sobre la superficie y manténgalo durante cinco segundos. Confirme que el músculo se ve rígido y de color blanco pálido inmediatamente después de quitar el hielo seco, y luego vuelve a su color y textura normales dentro de 22 a 25 segundos. Después de suturar la herida en la piel, coloque el ratón en una placa calefactora mantenida a aproximadamente 38 grados centígrados.Monitorizar continuamente hasta que el ratón recupere su reflejo de enderezamiento.

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 ...