[Observation on the effect of electroacupuncture on the regeneration of endometrium in rats with intrauterine adhesion].

Objective: To observe the effect of electroacupuncture (EA) on the degree of endometrial fibrosis and inflammatory response in the rat model of intrauterine adhesion (IUA), so as to explore the possible mechanism of EA underlying improving IUA and promoting endometrium regeneration.

Methods: Forty-five female SD rats were randomly divided into blank, model and EA groups, with 15 rats in each group. The IUA model was established by mechanical scratching combined with lipopolysaccharide infection. EA was applied to bilateral "Zigong" (EX-CA1) and "Sanyinjiao" (SP6), with acupuncture applied to "Guanyuan" (CV4) for rats in the EA group, started from the 2nd day after modeling, 15 minutes every time, once a day for 2 consecutive estrous cycles. Samples from 5 rats in each group were collected during estrus period. Changes of endometrial histopathology and number of glands were observed after HE staining. The area of endometrial fibrosis was observed and calculated after Masson staining. The positive expressions of collagen type I (Col-I) and transforming growth factor β1 (TGF-β1) proteins in endometrial tissue were detected by immunohistochemistry method. The protein expression of integrin αγβ3 in uterine tissue was detected by Western blot. The contents of interleukin (IL)-1β and tumor necrosis factor α (TNF-α) in uterine tissue were detected by ELISA. Samples from remaining 10 rats in each group were collected on the 8th day of gestation for calculation of the embryo implantation numbers of the rats.

Results: HE staining showed complete uterine tissue structure of the rats in the blank group during estrus period, with clear endometrial layer, unobstructed and regular uterine cavity, and dense glands. Destroyed endometrial layer, narrowed and adhered uterine cavity, and sparse glands of the rats were seen in the model group, which was relatively milder in the EA group. Following modeling, the number of endometrial glands, the protein expression of Integrin αγβ3, the number of implanted uterine embryos on the injured side of the model group were significantly decreased (<0.01), while the area of endometrial fibrosis, the positive expressions of Col-I and TGF-β1 proteins, and the contents of IL-1β and TNF-α in the uterine tissue were significantly increased (<0.01) in comparison with those in the blank group. After intervention, the number of endometrial glands, the protein expression of Integrin αγβ3, the number of implanted uterine embryos on the injured side of the EA group were significantly increased (<0.01，<0.05), while the area of endometrial fibrosis, the positive expressions of Col-I and TGF-β1 proteins, and the contents of IL-1β and TNF-α in the uterine tissue were significantly decreased (<0.01,<0.05) compared with the model group.

Conclusion: EA can enhance endometrial receptivity, and promote endometrial regeneration, be conducive to embryo implantation in IUA model rats, which may be related to its effect in alleviating endometrial fibrosis and reducing inflammatory response.