[Effect of letrozole on endometrosis and apoptosis of ectopic endometrial cells in rats].

OBJECTIVE

To investigate the therapeutic mechanism of letrozole, the third-generation aromatase inhibitor, on endometriotic lesions in a rat model and its effect on the apoptosis of ectopic endometrial cells.

METHODS

Endometriosis was induced by autotransplanting pieces of uterus onto the peritoneum in rats. The rats with successful ectopic implants were divided into 2 groups: A letrozole group (n=15) and a control group (n=15). The volume, appearance, and histopathology of ectopic implant were determined before and after the treatment. Expression of P450arom, COX-2, bcl-2, and bax in the ectopic implant was detected by immunohistochemistry and RT-PCR in the 2 groups.

RESULTS

The volume of ectopic implant in the letrozole group was significantly reduced compared with the control group (P<0.05). The protein and mRNA levels of P450arom and COX-2 in the ectopic implant were significantly decreased in the letrozole group compared with the control group (P<0.05). There was a positive correlation between the expression of P450arom and the expression of COX-2 (r=0.943, P<0.001; r=0.913, P<0.001). The protein and mRNA expression of bcl-2 was significantly decreased (P<0.05), and the bax protein and mRNA expression was significantly increased (P<0.05) in the ectopic implant with an increased bax/bcl-2 ratio in the letrozole group compared with the control group (P<0.05).

CONCLUSION

Letrozole can obviously reduce the size of ectopic implant through decreasing P450arom and COX-2 expression, suppressing the secretion of estrogen, inhibiting the proliferation, and inducing the apoptosis of ectopic implants.