Abstract: Objective To explore the effects of four different modeling method on endometrial receptivity, and establish a stable and effective experimental animal model of intrauterine adhesion ( IUA) with clinicopathological characteristics. Methods New Zealand white rabbits were randomly divided into 5 groups, according to different method of damage: chemical, infection, mechanical, thermal, and sham-operated ( control) groups. Rabbit bilateral uterine tissue was collected 4, 7, 14 and 28 d after treatment, and pathological changes were examined on both sides of the endometrium, using hematoxylin-eosin and Masson staining analysis. The thickness and number of endometrial glands and fibrosis area ratios were determined to evaluate the severity of adhesions. Pregnancy rates and the number of embryo implantations were used to examine reproductive function. Results Histopathological observations showed that both endometrial thickness and the number of glands decreased in the chemical-injured and heat-injured groups compared with the control group 7 and 14 d after treatment (P<0. 05), whereas the endometrial fibrosis area ratio was increased (P<0. 05). There were no significant differences between the mechanical damage and control groups. At 14 d after modeling, the pregnancy rate and number of uterine embryo implantations decreased in the chemical compared with the control group (P<0. 05), and the number of rabbit embryo implantations was significantly reduced (P<0. 001) in the heat- injured compared with control group. After 28 d of modeling, the chemical, infection and mechanical groups had basically recovered, but not the heat damage group. Conclusions In general, the histopathological changes observed in rabbit uteri after chemical injury modeling were more similar to the characteristics of moderate and severe IUA in humans, indicating this approach may be used as an effective model to investigate moderate and severe human IUA, and provide a basis for future in-depth study of the pathogenesis and treatment of IUA.

Abstract:Objective To compare Masson staining, van Gieson staining, and Sirius red staining for evaluation of an intrauterine adhesion (IUA) model in rats. Methods In total, 24 female adult Sprague-Dawley rats were selected and bilateral uteri exposed. To establish an IUA rat model, the left uterus was cut and the endometrium scraped using a scalpel. The right uterus was used as a control. Fourteen days after surgery, all uteri were collected for histological evaluation of IUA by hematoxylin and eosin (HE) staining, Masson staining, van Gieson staining, and Sirius red staining. Results HE staining showed that the endometrial epithelial layer of the uterus was absent, with a smaller number of endometrial glands than the control uterus ( P < 0.01). Collagen fibers were clearly visible using all special staining method . The fibrotic area rate of uteri by Masson staining (using toluidine blue) was higher than Masson staining (using light green), van Gieson staining, and Sirius red staining ( P < 0.01). Under polarized light, type I and type III collagen fibers were clearly distinguished by Sirius red staining, but not using Masson and van Gieson staining. Conclusions Sirius red staining is a superior method than Masson and van Gieson staining for evaluation of fibrosis in IUA and can also differentiate collagen fiber types.