Significance of expression of programmed cell death 5 in ovarian endometriosis

Objective To investigate the expression of programmed cell death 5 (PDCD5) in ovarian endometriosis and the effect of PDCD5 on the biological behavior of ectopic endometrial stromal cells. Methods Immunohistochemistry and RT-qPCR were used to detect the expression of PDCD5 protein and mRNA, respectively, in normal endometrium, ectopic endometrium, and eutopic endometrium. Ectopic endometrial stromal cells were isolated and cultured, and then PDCD5 was knocked down by RNA interference. The proliferation and apoptosis of ectopic endometrial stromal cells treated with leuprorelin of different concentrations were detected by CCK-8 assay and TUNEL assay, respectively. The difference in the expression rate of PDCD5 protein in the ectopic, eutopic, and normal endometrium was compared by the χ2 test. Pairwise comparisons of the relative expression of PDCD5 mRNA in ectopic, eutopic, and normal endometrium, the number of viable cells between the PDCD5 knockdown group and control group, cell proliferation inhibition rate and apoptosis rate in cells treated with different concentrations of leprorelin, and cell proliferation inhibition rate and apoptosis rate in ectopic, eutopic, and normal endometrium were performed by t-tests. Results The positive rates of PDCD5 protein in ectopic endometrium, eutopic endometrium, and normal endometrium were 30%, 29%, and 75%, respectively. The expression of PDCD5 protein in ectopic endopmetrium and eutopic endometrium was both significantly lower than that in normal endometrium (P=0.004 and 0.007, respectively). There was no significant difference in the expression of PDCD5 protein between ectopic endometrium and eutopic endometrium (P=0.928). The relative expression of PDCD5 mRNA in ectopic endometrium, eutopic endometrium, and normal endometrium was 0.24±0.02, 0.27±0.03, and 1.00±0.04, respectively. The expression of PDCD5 mRNA in ectopic endometrium and eutopic endometrium was both significantly lower than that in normal endometrium (t=-32.098, P<0.001; t=-28.659, P<0.001). There was no significant difference in the expression of PDCD5 mRNA between eutopic endometrium and ectopic endometrium (t=-1.617, P=0.181). The trend of mRNA expression is consistent with that of protein expression. Knockdown of PDCD5 had no significant effect on the morphology and proliferation of ectopic endometrial stromal cells in vitro. CCK-8 assay showed that with the increase of leuprorelin concentration, the proliferation inhibition rate of cells in the PDCD5 knock-down group and control group increased gradually, and at the same concentration of leuprorelin, the cell proliferation inhibition rate was significantly lower in the PDCD5 knockdown group than in the control group (P<0.05). TUNEL assay showed that the apoptosis rate of cells treated with leuprorelin at 0.1 μg/ml was significantly in the PDCD5 knockdown group (0.06±0.01) than in the control group (0.13±0.02) (t=-5.972, P<0.001). Conclusion PDCD5 knockdown can reduce the sensitivity of ectopic endometrial stromal cells to leuprorelin, resulting in decreased apoptosis and increased cell proliferation. The down-regulation of PDCD5 expression in ovarian endometriosis may promote the occurrence and development of endometriosis. Key words: Endometriosis; Programmed cell death 5; Immunohistochemistry; Leuprorelin; Stromal cells