OBJECTIVETo investigate the role of mast cells in the pathogenesis of estrogen-mediated experimental endometriosis in rats.

METHODSEndometriosis model was established by transplanting autologous fragments of uterus to the inner surface of the abdominal wall in 24 un-pregnant female Sprague Dawley rats. The rats were divided randomly into three groups (n=8 in each group), and were injected with different doses of estrogen: high-dose group (200 μg·kg⁻¹·d⁻¹), low-dose group (100 μg·kg⁻¹·d⁻¹) and the control group (0 μg·kg⁻¹·d⁻¹). The ovaries were surgically removed in high-dose and low-dose groups. Four rats were sacrificed in each group at 2 and 4 weeks after surgery. Their serum estradiol levels, size of lesions, total number of mast cells and degranulations, serum TNF-α levels, expression of tryptase and NGF in tissues were analyzed and compared among groups.

RESULTSThe mean levels of serum estradiol 2 weeks and 4 weeks after model established and serum TNF-α at 4 weeks in estrogen-treated groups were significantly higher than those in control group (all P<0.05). The mean size of endometriotic lesions in the estrogen-treated groups was also significantly larger than that in the control group 2 weeks and 4 weeks after model established (all P<0.05). Meanwhile, both at week 2 and week 4, the mean ratio of degranulation/total number of mast cells by toluidine blue staining in low-dose estrogen group was significantly higher than that in the control group (P<0.05). The expression of NGF in high-dose estrogen group was significantly higher than that in the control group at week 4(P<0.05).

CONCLUSIONEstrogen can promote the growth of endometriotic lesions and may mediate the pathogenesis of endometriosis by activating mast cells, which may be associated with increasing TNF-α and NGF levels.