Early Changes in Structural and Stress-Like Genes after Radiation to the Submental Muscles

Abstract

INTRODUCTION: Radiation treatments for head and neck cancer can lead to early alterations in swallowing kinematics that ultimately develop into dysphagia and require modifications in oral intake. The submental muscles (ie mylohyoid) are located inferior to the mandible and are crucial for swallowing function. Expression of collagen and heat shock proteins can be altered following muscle injury, which can impair muscle fiber regeneration leading to conditions of muscle atrophy or fibrosis. The aim of this study was to evaluate collagen and heat shock protein (HSP) 72 (HSPA1A/B) expression in a rat model of radiation-induced dysphagia. HSP72 is known to increase in response to stress and is needed to mediate muscle repair after injury. METHODS: We hypothesized that the submental muscles treated with 48 Gy of fractionated radiation would have increased expression of HSPA1A, HSPA1B, COL1, COL3, and COL4 genes at 2 and 4 weeks post treatment. Relative gene expression was measured using RT-PCR. RESULTS: The results showed that there was a sequential increase in expression of HSPA1A, HSPA1B, COL1, and COL3 at both the 2-week and 4-week post irradiation points. There was a greater increase in expression in COL4 at the 2-week compared to the 4-week post irradiation point. The highest change in gene expression was observed with HSPA1A and COL3. CONCLUSION: Results support the idea that irradiation treatment provokes early gene changes that may contribute to modifying the muscle structure and promoting dysphagia which can lead to decreased quality of life for head and neck cancer patients.