Construction and evaluation of intrauterine adhesion model in rats by different methods of mechanical injury.

PURPOSE: The study aimed to establish a stable and effective animal model for the experimental study of intrauterine adhesion (IUA) by evaluating various mechanical injury methods. METHODS: A total of 140 female rats were divided into four groups according to the extent and area of endometrial injury: group A (excision area: 2.0 × 0.5 cm2), group B (excision area: 2.0 × 0.25 cm2), group C (endometrial curettage) and group D (sham operation). On the 3rd, 7th, 15th and 30th day after the operation, the tissue samples of each group were collected, and the uterine cavity stenosis and histological changes were recorded by HE and Masson staining. Immunohistochemistry of CD31 was applied to visualize microvessel density (MVD). The pregnancy rate and the number of gestational sacs were used to evaluate the reproductive outcome. RESULTS: The results showed that endometrium injured by small-area endometrial excision or simple curettage could be repaired. The ratio of fibrosis in groups A and B was higher than that in groups C and group D 30 days after modeling (P < 0.001). The number of endometrial glands and MVD in group A was significantly lower than those in groups B, C and D (P < 0.05). The pregnancy rate in group A was 20%, which was lower than that in groups B (33.3%), C (89%) and D (100%) (P < 0.05). CONCLUSION: Full-thickness endometrial excision has a high rate of success in constructing stable and effective IUA models in rats.

Smad signaling coincides with epithelial-mesenchymal transition in a rat model of intrauterine adhesion.

PURPOSE: Intrauterine adhesion (IUA) is a fibrotic disease mainly caused by tissue injury, yet the mechanism is poorly understood. The aim of this study was to investigate the roles of TGF-ß1/BMP7/Smad signaling coincident with epithelial-mesenchymal transition (EMT) in IUA. METHODS: Twenty-four female SD rats were divided into IUA and sham groups. For each animal, a mechanical injury or sham operation was performed on the left uterus (IUA-L, Sham-L), and the right uterus (IUA-R, Sham-R) was used as the control. Animals were sacrificed in batches on days 7 and 28. The endometrial morphology, number of endometrial glands, microvascular density (MVD), area of endometrial fibrosis and immunohistochemistry (IHC) analysis of biomarkers of EMT, as well as levels of TGF-ß1, phosphorylated Smad3 (pSmad3), BMP7, phosphorylated Smad1/5 (pSmad1/5) and estrogen receptor (ER) were evaluated. Besides, the correlation between these IHC markers was also analyzed. RT-PCR and western blot were used to test relevant genes. RESULTS: Compared with other groups, the IUA-L group showed a significant decrease in the number of glands and MVD. And it also showed a significant increase in the stromal fibrosis rate and a-SMA level. Moreover, in the IUA-L group, TGF-ß1 and pSmad3 levels were consistently high, and levels of BMP7, pSmad1/5 and ER were low. EMT markers E-cadherin was decreased, while N-cadherin was increased. Sham and control groups showed no significant difference in these markers. In addition, E-cadherin with a-SMA, fibrosis rate with BMP7, TGF-ß1 with pSmad3 and BMP7 with pSmad1/5 showed correlation in IUA-L group, which had statistical significance. The mRNA expression of TGF-ß1, a-SMA and ccn2 in 7 d IUA-L was higher than 7 d IUA-R while BMP7 was lower, which had significant difference. The protein expression of BMP7 in 7 d IUA-L was lower than 7 d IUA-R, which had significant difference. CONCLUSIONS: These results suggest a potential role of Smad signaling together with EMT in endometrial fibrosis development.