Rodent Model of Masseter Volumetric Muscle Loss for Studying Bioengineering Materials

Our research is focused on skeletal muscle regeneration in the face and the body. We aim to understand what limits regeneration in mammals, including humans, using various experimental approaches. In this project, we are focused on volumetric muscle loss and approaches to understand it mechanistically and develop therapeutic approaches.

Creating reliable experimental models for volumetric muscle loss is difficult, especially for smaller muscles. The models need to be reproducible and relevant to the biological condition in order to test limitations of regeneration and therapeutic approaches. And without good in vivo models, it's not possible to understand this injury.

This model helps researchers understand muscle response, treatment effects, and regeneration after craniofacial injuries. This is significant because treatments have not changed in decades, and understanding the injury response can lead to future therapeutics. Craniofacial skeletal muscle differs from extremity muscle in gene expression and fiber composition.

VML injuries affect them differently, and our model aims to investigate their regenerative capacity and develop new tissue engineering approaches. To begin, position the rodent on its left side with its nose fitted into an anesthetic nose cone for right facial exposure. Apply ophthalmic ointment to the rodent's eyes.

Use depilatory cream to remove fur from the operative site. Then disinfect the operative site using both ethanol and Betadine scrub, repeating several times. After creating a longitudinal incision, elevate the skin flap to visualize the right masseter and the buccal and mandibular branches of the facial nerve.

Using blunt separation, clear the skin from the underlying fascia. Hold the skin edges with surgical clamps for optimal visualization of the underlying muscle. Use blunt separation to expand the space between the fascia and the masseter, preserving the integrity of the remaining fascia.

Next, make a transverse incision in the fascia over the anterior portion of the masseter. Then employ a sterilized disposable punch biopsy to create a circular injury in the muscle, using the fascial incision as a window to the superficial masseter. Use surgical scissors to excise the tissue injury created by the biopsy punch.

After that, add the biomaterial to the circular masseter injury. Once the agent is suitably in place, using a 5-0 monofilament suture, suture the muscle investing fascial window to prevent agent migration. Close the skin using a simple, interrupted, or running subcuticular technique, employing a 5-0 monofilament suture.

Apply skin glue over the sutures to prevent postoperative incision dehiscence. Then place the rats in a recovery cage with an external heating source. Dilute the antibiotic, trimethoprim-sulfamethoxazole, in drinking water.

Add it to the rodent's drinking water for seven days postoperatively.