The Impact Of Local Endometrial Injury On Embryo Implantation And Its Mechanism In Mouse

In2003, Barash et al. firstly reported that endometrial biopsies taken at days8,12,21and26, respectively, before IVF treatment cycle can improve the rates of implantation,clinical pregnancies and live births. Such similar results were confirmed by other clinicalreports. However, due to the limitation of human endometrial biopsies, the underlyingmechanism of local endometrial injury remains uncertain. In this study, we established amouse model of endometrial local injury, and further investigated the mechanism withregard to its improvement of embryo implantation and clinical pregnancy.We speculated that the mechanism of local endometrial injury on enhancing the ratesof embryo implantation and clinical pregnancy was related to improve uterine receptivitythrough provoking cytokines to secret and local morphology to change. Normalpregnancies need the support of the endometrial glands. Pinopode is regarded as theimportant morphological marker of uterine receptivity. LIF and OSM belong to IL-6family. LIF was regarded as the key factor for embryo implantation, for it specificallyexpressed in the duration of implantation window. The biological function of OSM issimilar to LIF. Besides, it owns unique characteristics in angiogenesis and wound healing.In the present study, by using the established mouse model of local endometrial injury, themechanism of local injury to the endometrium was investigated in view of morphological changes (e.g. endometrial glands and pinopodes) and local cytokine production (e.g. LIFand OSM).Part Ⅰ Establishment of a mouse model for local endometrial injuryObjectives: The purpose of this study was to establish a mouse model for local endometrialinjury that could provide a experimental model for further research.Methods: Female Kunming mice were randomly allocated to four groups. The normalcontrol group (Group I) was composed of untreated mice, which were naturally matedduring their estrus phases. The surgical control group (Group II) was just dealed withopening the abdominal. Unilateral-injury procedure in one horn was performed and anotherhorn was remained normal to serve as control (Group III). Bilateral-injury procedure in twohorns was performed (Group IV). Estrus was identifed by daily vaginal smear. The localinjury on the endometrium was done by the following procedurs: opening the miceabdominal and exposing the uterus after being anesthetized, using a blunt syringe tocurettage endometrium at three site of the uterus. They were mated on the night when thenext estrus coming. If vaginal plug was observed on the next day morning, it was regardedas the first day of pregnancy. All pregnant mice were sacrifced at noon on the8th day ofpregnancy. Finally, the uterus was checked, and the number of implantation blastocyst oneach side of uterine and the total number of embryos were calculated.Results: The number of implantation blastocyst on the right side of uterus in Group IIIwas significantly higher than that in Group II,(7.50±1.83vs.5.54±1.05, respectively, P<0.05). The number of implantation blastocyst on each side of the uterus and the totalnumber in Group IV were significantly higher than Group II (7.38±1.81vs.5.62±1.98,7.69±2.69vs.5.54±1.05,15.08±2.43vs.11.15±2.19, respectively)(P <0.05).Conclusion: Local endometrial injury can improve the number of implantation blastocystin mouse. And the established mouse model for local endometrial injury can be used for thefollowing mechanism study. Objectives: To evaluated the impact of local injury on the endometrium at the duration ofof uterine receptivity in mouse with regard to the morphology.Methods: The endometrial species were taken at the4thday of pregnancy in mouse. Byusing hematoxylin-eosin (HE) staining method, the changes of the endometrial glands wereobserved among the three groups. Using scanning electron microscopy (SEM), the changesof pinopode ultrastructure were identified.Results: The HE staining results showed that in the normal controls (Group I), the luminalepithelium was well organized and full of glands. And the interstitial tissues were scarce. Inoperative controls (Group II), the thickness of endometrium became thin. The glands andthe gland secretion were less. The areas of the interstitial tissues were increased. In thebilateral-injury group (Group IV), the thickness of the endometrium increased obviously.And the luminal epithelium was well organized. The glands were well-developed. Theareas of the interstitial tissues were decreased. The SEM results showed that in Group I, thepinopodes were uniformly distributed, and a few microvilli were present on the pinopodes.In Group II, the number of the pinopodes reduced obviously. In Group IV, the pinopodeswere abundant and well-developed. Compared to the normal controls, the microvilli wereless.Conclusion: Compared with the Group I and Group II, the endometrial thickness increased,and the glands and pinopodes were more aboundant in Group IV. Moreover, the pinopodeswere well-developed. These findings indicated that local endometrial injury improved theuterine receptivity at the duration of implantation window by inducing the hyperplasic ofendometrial glands and the development of the pinopodes. This might be one of the reasonwhy the local endometrial injury enhanced the embryo implantation. Objectives: To evaluate the impact of local injury on endometrial receptivity with regard tolocal cytokine production of LIF and OSM.Methods: The endometrial species were taken at the4thday of pregnancy in mouse. Usingquantitative reverse transcript polymerase chain reaction (qRT-PCR) and western blotmethods, the levels of LIF and OSM mRNA and protein expression were detected.Results: Compared with Group II, the levels of both LIF and OSM mRNA expression weresignificantly increased in Group IV (P <0.05). LIF and OSM protein can be detected inall groups. Compared with Group I, the level of LIF protein expression in Group IV wereincreased (P <0.01). However, that of LIF protein expression in Group II was significantlydecreased (P <0.05). The levels of OSM protein expression in Group IV were also morethan those in Group II (P <0.05).Conclusion: The levels of both LIF and OSM mRNA and protein expression wereobviously increased in Group IV when compared with the Group II. The observationsindicate that local endometrial injury stimulates the compensative production of LIF andOSM, which can improve the endometrial receptivity. This might be the another reasonwhy the local endometrial injury enhanced the embryo implantation.