Background: Decreased susceptibility of endometrial tissue to apoptosis may contribute to the pathogenesis of endometriosis. We investigate the role of survivin in the pathophysiology of endometriosis through the ability of ectopic and eutopic endometrial stromal cells (ESCs) to resist apoptosis.

Methods: Ectopic ESCs were obtained from ovarian chocolate cysts in patients undergoing laparoscopic surgery (n = 22). Eutopic ESCs were isolated from endometrial tissue of cyclic premenopausal women undergoing hysterectomy for fibroids (n = 22). Purified stromal cells were studied in vitro. The number of surviving cells and activation of caspases were assessed by WST-8 assay and immunoblotting. Expression of inhibitor of apoptosis proteins (IAP) family members: cIAP1 (birc2), cIAP2 (birc3), XIAP (birc4), survivin (birc5) were examined using cDNA array and real-time RT-PCR. Effects of gene silencing by small inhibitor RNAs (siRNA) were examined by WST-8-assay, Annexin-V staining and immunoblotting.

Results: After staurosporine (SS) treatment, 55% of eutopic ESCs survived versus 70% of ectopic ESCs. Procaspase-3 or -7 was more intensely activated by SS treatment in eutopic than in ectopic ESCs (P < 0.01). mRNAs for IAP-family genes, such as cIAP-1, XIAP and survivin, were highly expressed in ectopic ESCs before SS treatment. The fold induction of survivin expression after SS treatment was higher in ectopic than eutopic ESCs (2.8 +/- 0.27 versus 0.69 +/- 0.07, respectively). Survivin gene silencing in SS-treated ectopic ESCs led to an increase of apoptotic cells (P < 0.05, versus control siRNA).

Conclusions: We demonstrated that survivin plays a critical role in susceptibility of ESCs to apoptosis. Our results indicate that a survivin inhibitor may be effective as a novel treatment for endometriosis.