Effect of radiation on cytokines, MMP-1 and type I collagen mRNA expressions in human gingival fibroblasts.

e16034 Background: Oral mucositis is an acute injury to the mucosal lining of the head and neck region associated with radiation therapy (RT). In this study, we aimed to elucidate the effects of radiation on the proliferation of gingival fibroblasts and proinflammatory cytokines and matrix metalloproteinase-1 (MMP-1), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and type I collagen (COL I) mRNA expressions of gingival fibroblasts. Methods: Gingival fibroblasts were isolated from human gingival connective tissue of systemically healthy individuals. These cells were treated with radiation dosages as follows; control group (untreated), 0.5 Gry, 1 Gry, 2 Gry, 4 Gry, 6 Gry, and 8 Gry. RT was applied in the form of a single dose which was applied with linac 6 MV photon beams. Cell proliferation was determined by counting cells at 24 and 48 hrs. Total RNA was isolated at 24 hours after radiation. Expression of interleukin (IL)-1 beta, IL-6, IL-8 and MMP-1, TIMP-1 transcripts in HGFs was determined by quantitative PCR (QPCR) analysis. Morphology of gingival fibroblasts was evaluated using inverted microscope after different dosages of radiation. For proliferation experiments and gene expressions, the statistical analysis used was one-way analysis of variance (ANOVA) and Turkey HSD multiple comparison tests. Results: Radiation decreased cell proliferation (p<0.05) compared to the control group. Expression of IL1beta, IL-6 and IL-8 was stimulated at higher dosage (8 Gry) of radiation (p<0.001) (figure 1). In parallel, MMP-1, and TIMP-1 mRNA expressions were elevated in response to highest dosage of radiation (p<0.001) (figure 2). Radiation suppressed COL I mRNA expression in response to all dosages at 24 hrs (p<0.001). Conclusions: These findings demonstrated that radiation even in a single dose regulates behavior of gingival fibroblasts. Radiation-induced inflammatory characteristics of gingival fibroblasts could potentially lead to a disruption of oral mucosa. Results of this study clarify the possible mechanisms of radiation induced oral mucositis in radiation treated cancer patients.