Effect of BCG vaccine on peritoneal endometriotic implants in a rat model of endometriosis

To investigate the effect of Bacillus Calmette-Guerin (BCG) vaccine on peritoneal implantation of endometrial tissue in rats. Forty sexually mature virgin Wistar albino rats weighing 190-200 g were randomly assigned (double blind) to two groups. The rats in the first group were vaccinated with 0.1 mL BCG and those in the second group were injected with 0.1 mL saline into the tail, intracutaneously. All the rats underwent median laparotomy after 4 weeks of vaccination or injection. The right uterine horn was excised, and the two samples of endometrial tissue dissected from myometrium were implanted on each side of peritoneum at the 2 cm lateral line of the median laparotomy incision. The implanted peritoneal segments were excised after 8 weeks of laparotomy. The tissue samples were accepted, histologically, as endometriosis when both glands and stroma of endometrial tissue were seen in sections. Thirty-six implants from the study group and 34 implants from the control group were obtained. Ten and 23 implants were accepted as endometriosis in the study and control group, respectively. The number of endometriotic foci were significantly lower in the study group than in the control group (P = 0.01). Stimulation of the cellular immune response with BCG vaccine could exert an inhibitory effect on ectopic endometriotic implants.