Apoptosis and Differential Expression of Apoptosis-Related Proteins in Endometriotic Glandular and Stromal Cells

Objective Apoptosis is an important regulator of eutopic endometrial function. Endometriosis, the growth of endometrial tissue outside the uterus, could result from increased cellular proliferation or decreased apoptosis in response to appropriate stimuli. The objective of this study was to evaluate the rate of apoptosis and the expression of apoptosis-related Bcl-2 and Box proteins in endometriotic tissues within the glandular and stromal compartments, according to the phase of the menstrual cycle and the stage of disease. Methods Ovarian endometriosis samples were evaluated in 75 women who had surgery at a university hospital. Apoptotic cells were detected with the use of the dUTP nick-end labeling (TUNEL) assay. Bcl-2 and Bax expression were assessed by immunohistochemical techniques. Results The percentage of apoptotic cells was significantly higher in endometriotic stromal cells (73.3%) compared with glandular cells (48%; P = .002). In contrast, the expression of the apoptosis-related proteins Bcl-2 and Bax was significantly lower in the endometriotic stroma (17.3% for both) than in the glandular epithelium (38.6% and 41.3%, respectively; P < .004). No significant menstrual cycle phase-dependent changes or endometriosis stage-related changes were observed in TUNEL, Bcl-2, or Bax positivity within ovarian endometriotic tissues. Conclusion Apoptosis occurs in ovarian endometriotic lesions at significantly higher levels in the stroma than the glandular epithelium. However, Bcl-2 and Bax proteins are distributed preferentially in glandular epithelial cells. The apoptotic rate as well as Bcl-2 and Bax expression in ovarian endometriotic cells were not affected by the stage of endometriosis or the phase of the menstrual cycle.