Objective: We used an animal irradiation model to investigate and define the molecular mechanisms affecting SGs following IR, focusing on saliva proteome and global transcription profile of submandibular salivary gland (SSG) tissue.
Methods: Saliva was measured following pilocarpine stimulation and rat SSG tissue was obtained before and 4, 8, and 12 weeks after 15-Gy IR to head and neck. Saliva was subjected to proteomic analysis and tissue mRNA expression was determined by microarray followed by real-time PCR validation and confocal microscopy.
Results: Saliva secretion was gradually reduced to 50% of its initial level 12 weeks post-IR. Interestingly, proteomic analysis revealed proteins with reduced expression originating from SSGs and proteins with increased expression derived from the serum, both indicating salivary tissue damage. Microarray analysis revealed significant alteration in 95 genes, including cell-cycle arrest genes, SG functional genes and a DNA repair gene. Confocal immunofluorescence of α-amylase and c-Kit showed an increase and decrease, respectively, in protein expression, as seen in real-time PCR.
Conclusions: This data indicates that IR damages the SSG cells' ability to produce and secrete saliva and proteins, and maintain the physiological barrier between serum and saliva. The damage does not heal due to cell-cycle arrest, which prevents tissue regeneration. Taken together, our results reveal a new insight into IR pathobiology.