The Mechanism Study For The Treatment Of Thin Endometrium Through Mechanical Loading

BackgroundThin endometrium is a common gynecological disease in women,its incidence is increasing year by year.The infertility caused by thin endometrium seriously affects the reproductive health of women,which is a difficult problem in the field of reproductive medicine.Thin endometrium is characterized by high resistance of uterine artery blood flow,limited growth of glandular epithelium,low expression of VEGF and vascular dysplasia.It is necessary to find a new treatment method based on the pathology of thin endometrium.Our self-developed pulsed mechanical loading is a physical rehabilitation therapy that imitate human active physical exercise by mechanically stimulating synovial joints such as knee joints at a certain frequency.The preliminary work has shown that in the animal model of femoral head necrosis,mechanical loading can promote angiogenesis by up-regulating the expression of VEGF,while increasing blood perfusion to strengthen the vascular remodeling of femoral head.However,the effect of mechanical loading on the treatment of thin endometrium is unclear.ObjectivesIn order to further understand the therapeutic effect and mechanism of mechanical loading on thin endometrium,an ethanol-induced animal model of thin endometrium was used in this experiment.We investigated whether mechanical loading could repair the thin endometrium.Based on the observation of the therapeutic effect,we further explore whether the mechanism of mechanical loading therapy can play a vital role by regulating endoplasmic reticulum stress in uterine cells.MethodsIn this experiment,thirty female Sprague-Dawley rats with regular estrous cycles were randomly divided into three groups: sham operation control group(Control,n=10),thin endometrium model group(Model,n=10)and mechanical loading treatment group(Loading,n=10).The thin endometrium model was established by intrauterine injection of 95% ethanol in the estrus phase.The same amount of normal saline was injected into the uterine cavity in Control group.Loading group received knee loading on the second day after modeling.For knee loading,5 N loads were laterally applied to the knee at 15 Hz for 5 min/day for 3 estrous cycles.Hematoxylin-eosin(HE)staining was used to observe the histopathological changes of endometrium,and endometrial thickness,endometrial area and gland numbers were measured.The expressions of VEGF and Ki-67 in the endometrium were detected by immunohistochemistry.The cell proliferation and angiogenesis of endometrium were analyzed by the expression of Ki-67 and VEGF.Western blot was used to evaluate the expression of endoplasmic reticulum stress pathway related proteins such as p-eIF2 ?,ATF4,GPR78 and CHOP.Results 1.Histopathological changes of endometrium: the endometrium of Control group had complete structure,and the epithelial cells in the lumen and the glandular had normal morphology and tight arrangement.In addition,there was no edema in the stroma of the endometrium,and the glands and vessels were normal.Compared with Control group,the endometrium in Model group was significantly thinner,and exfoliated tissue fragments were seen in the uterine cavity.The number of epithelial cells in the lumen and the glandular epithelium was decreased,and their arrangement was uneven.Further,the stroma of the endometrium is obviously edema,and endometrial glands and blood vessels are reduced.After mechanical loading treatment,the thickness of endometrial layer in Loading group was significantly increased,and most of the endometrial intact structures were observed.The number of epithelial cells in the lumen and the glandular epithelium was increased,and their arrangement was very close.The endometrial interstitial edema was significantly improved,and the glands and blood vessels were significantly increased.The pathological changes were significantly improved in comparison with those in Model group.2.Measurement results of endometrial thickness,endometrial area and gland numbers: compared with Control group,endometrial thickness,endometrial area and gland numbers in Model group were significantly decreased(all P < 0.001).Compared with the Model group,endometrial thickness,endometrial area and gland numbers were significantly increased in Loading group(all P < 0.01).3.Expression of VEGF and Ki-67 in endometrium: VEGF was mainly expressed in the cytoplasm of epithelial cells and stromal cells,while Ki-67 was mainly expressed in the nucleus of glandular epithelial cells and stromal cells.Compared with Control group,the expression of VEGF and Ki-67 was significantly decreased in Model group(both P < 0.001).After mechanical loading treatment,the expression of VEGF and Ki-67 were significantly increased in Loading group compared with Model group(both P < 0.01).4.Expression of p-eIF2?,ATF4,GPR78 and CHOP in endometrium: compared with Control group,the expression of ER stress-linked proteins such as p-eIF2?,GRP78,ATF4 and CHOP was significantly increased in Model group(all P < 0.01).After mechanical loading treatment,the expression of p-eIF2?,GRP78,CHOP and ATF4 was significantly decreased in Loading group compared with Model group(P < 0.05,P < 0.05,P < 0.01 and P < 0.05,respectively).ConclusionsIn this study,animal model of thin endometrium was successfully established by intrauterine injection of 95% ethanol.The results showed that knee loading could promote endometrial regeneration,increase endometrial thickness,endometrial area and the number of glands.At the same time,knee loading can promote the cell proliferation and angiogenesis of endometrium.These effects with knee loading might be related to the inhibition of ER stress.The study provides a new idea for treatment of thin endometrium.