Establishment of an animal model of intrauterine adhesions

Objective To establish a stable animal model for the study of pathological regeneration of intrauterine adhesions （IUAs）. Methods Thirty female SD rats were randomly divided into the experimental （n=15） and control groups （n=15）. In the experimental group, a self-made 2-mm diameter curette was utilized to create mild and severe mechanical injury to the left and right endometrium of estrous rats and then divided into the mild and severe mechanical injury groups, respectively. In the control group, the rats were not treated with endometrial injury after open surgery, which were used as sham surgery controls. At 0 h, 24 h, 72 h, 5 d, and 7 d after surgery, bilateral uteruses were removed from 3 rats in each group and prepared for quick frozen sections for MHCⅡ and BrdU immunohistochemical staining. The endometrial glands of different rats were observed at postoperative 7 d, and the inflammatory reaction of endometrial tissues and the changes of endometrial tissue proliferation and repair were also observed in rats with different degrees of mechanical injury at different time points after surgery. Results In the mild mechanical injury group, a small amount of red-stained BrdU-containing cells and blue-stained MHCⅡ cells were seen at 7 d after surgery, and the endometrium was basically repaired, while mild inflammatory reaction occurred. In the severe mechanical injury group, no endometrial glands or very few glands were detected, no obvious red-stained BrdU-containing cells were seen, a small quantity of blue-stained MHCⅡ cells, mild inflammatory reaction, endometrial fibrosis, local lumen closure and adhesion were observed at postoperative 7 d. Compared with the control group, the number of endometrial glands in the rat uterine cavity was decreased along with the increase in the degree of mechanical endometrial injury at 7 d after surgery, and the difference was statistically significant （P < 0.001）. Conclusions The rat model of IUAs can be successfully established by incision and suture of endometrial mechanical injury method. After mild mechanical injury, the endometrium of rats can regenerate and achieve basic repair. Nevertheless, the endometrial tissues cannot achieve basic repair after severe mechanical injury. In addition, tissue fibrosis occurs, leading to IUAs.