Abstract: Objective To investigate the effect of Xiaojie-An on ultrastructural changes of uterine flesh tumour cells
and reveal the possible mechanism for the treatment of uterine fibroids. Methods The rat model of hysteromyoma was
established by intramuscular injection of estradiol benzoate three times a week for five weeks. The model rats were randomly
divided into 5 groups according to their body weights including model group, Xiaojie-An groups (high, medium and low
doses), positive drug group and control group. After treatment for 4 weeks, the changes of uterine morphology, serum estrogen
and progesterone were observed, and the diameter of uterus above cervix, cervical transverse diameter of uterus from the root
of left angular uterus were measured. The ultrastructure changes of uterine cells were observed under electron microscope.
Results The uterine coefficient, ovarian coefficient, angular diameter and root diameter of angular fraction were all bigger
in the model group than those in the control group (P＜0.05). The uterine coefficient, horn diameter and root diameter were
all smaller in the positive drug group than those of Xiaojie-An groups (high, medium and low doses, P＜0.05). There were no
significant difference in above indexes between (high, medium and low dose Xiaojie-An groups. Results of transmission
electron microscopy showed that the treatment with Xiaojie-An could effectively improve the ultrastructural changes of
uterine fibroids and inhibit the abnormal proliferation of smooth muscle cells. Pathological examination showed that the
secretory changes in endometrium of the control group, with varying degrees of eosinophilic leukocyte infiltration in the
interstitium and no abnormalities in the muscular layer. In the model group, the endometrium showed secretory changes, the
smooth muscle layer of the uterus was thickened, the number of muscle cells increased, hypertrophy, irregular arrangement and small amount of neutrophils infiltration. High dose group and positive drug control group showed the better improvement.
Conclusion Xiaojie-An can reduce the volume of uterus, improve the ultrastructure of myoma cells, and then achieve the
therapeutic effect.

Key words: leiomyoma, uterine neoplasms, microscopy, electron, scanning transmission, gonadal steroid hormones,
Xiaojie-An