A Preliminary Study On The Apoptosis Of Cells In The Duct-ligated Rat Parotid Gland

ObjectiveTo investigate the expression of cell apoptosis-related gene in the parotid gland cells after ligation of duct in rats, elucidate the role of cell apoptosis-related gene on the atrophy of parotid gland and reveal the molecular mechanism of apoptosis in atrophic parotid acinar cells, ductal cells for providing gene therapy target spot for newly-developed gene in the treatment of parotid gland diseases.MethodsAtrophy of the right parotid gland was induced by ligating the stensen duct of rat.Histological changes of parotid glands were examined by HE staining during each step of glandular atrophy at time0(control)、1、3、5、7、14、21、30、60、90、120days after ligation;Acinar and ductal cells apoptosis were detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling (TUNEL).Protein expression of PDCD5、TMEM166and MAP1IC3were measured by Immunohistochemistry.ResultsAfter ligation of parotid gland duct, the morphological observation revealed that disorderly arrangement of acinar cells and dilatation of ducts on3days, disappearance of the majority of acinar cells and increased number of duct-like cells on5days, almost disappearance of acinar cells on21days,almost duct-like tissue on30days.Quantitative analysis of immunohistochemical staining results showed that PDCD5TMEM166protein uniformly distributed in normal parotid cytoplasm and expressed with a low level. The expression of PDCD5、TMEM166protein were significantly increased and peaked at3d and distribuded both in cytoplasm and nuclear. The average OD values of PDCD5、TMEM166in acinar cells were higher than those in duct cells at day1and3after duct ligation (P<0.05). The expression of MAP1IC3protein showed a low level condition in normal parotid cells, and significantly increased and peaked at1d and exhibited a uniform distribution in cytoplasm of parotid gland cells.TUNEL experiments showed that apoptotic cells were obviously upregulated at3d after duct ligation. The apoptosis index observed in acinar cells (21.750±0.119) was higher than that in duct cells (5.720±0.205). The difference between them was significantly in statistics. After3days, the apoptosis index progressively decreased. Further analysis indicated that there was a significantly positive correlation between increased PDCD5-TMEM166、 MAP1IC3levels and cell apoptosis induced by duct ligation.ConclusionAcinar cells and duct cells atrophy was attributed to cell apoptosis, which mainly occurred acinar cells, exhibiting a regular change.The expression of PDCD5、TMEM166、MAP1IC3is closely associated with the atrophy of the parotid gland after rat parotid duct ligation, indicating that PDCD5、TMEM166、 MAP1IC3might play an important role in apoptotic pathways after parotid duct ligation.