Investigation of Proliferation of Myoepithelial Cells in Irradiated Salivary Glands

Abstract

Title: Investigation of Proliferation of Myoepithelial Cells in Irradiated Salivary Glands. objectives: Investigate the Proliferative Activity of myoepithelial cells in irradiated rabbite salivary glands. Materials & Methods: Experimental Procedures: 16 rabbits were used ,eight rabbits were irradiated using doses of 10,20,30 and40 Gy, two rabbits for each dose, another 8 were irradiated using a dose of 40 Gy and were sacrificed after ( one, two weeks, one,4 months), major salivary glands were obtained and histologically prepared for investigation. Two rabbits were added as control group. Immunohistochemical Staining: The irradiated and control glands were examined immunohistochemically using immunohistochemical double staining Technique for PCNA and α-SMA . Quantification :The labeling indices of Actin and PCNA in myoepithelial cells were calculated, myoepithelial cells were randomly counted within eight fields at a magnification of 400 and the percentage of cycling (Actin ,PCNA-positive) cells was calculated. Statistical analysis of data was assessed using chi square test. Results: -compared with control glands there was increase in the expression of PCNA with increasing radiation dose(10→40Gy) in parotid gland, while in submandibular gland we found this increase in (40Gy) group(p=0.006) , the increase in the expression of PCNA was in parotid gland more than that in submandibular gland. Same was found in the follow-up groups (one, two week, one month, 4 months) in parotid and submandibular glands. the increase in the expression of PCNA was in (two week, one month) groups in parotid gland(35.1% , 39.4%)more than that in submandibular gland(21.5%,24.3%)(p=0.003,p=0.001), while in (4 months) group; submandibular gland(48.0%)was more than that in parotid gland(34.8%) (p=0.002). Conclusions: myoepithelial cells showed dose and follow-up period -related increase proliferative activity, this may give a new idea about the involvement of this cell in the radiogenic tissue damage and fibrosis of salivary glands after radiogenic damage.