Established a comprehensive mice model of persistent genital arousal disorder and investigated the mechanism of VEGF-ERK signal pathing in vaginal microvascular injury
Authors: Yu Puguang , Li Guangyong , Chen Xiaojiang , Ren Shuai , Wang Qiangqiang , Su Yashan , Chen Keming , Feng Jiajin , Liu Hetao , Han Huaiqin , He Rui 
Published: July 2022

Abstract
Aim: (1) Simulating vaginal delivery and menopause to establish a mouse model of PGAD; (2) screen out a set of detection methods for quantifying and evaluating mouse sexual function; (3) further explore the relationship and possible mechanism of vaginal microvascular injury and PGAD.Methods: Animal study about established a PGAD mouse model with vaginal dilation and ovariectomized, and ligated vaginal microvascular to compared effects of blood flow on sexual behavior with sham. Animals: C57/B6J mice. Intervention: 8-week-old post-childbirth mice were vaginal dilation and ovariectomy and reared for 1 or 2 months. In addition, ligated microvascular around the vagina to build a vaginal ischemia model.Main Outcome Measures: Video cameras continuously recorded the mice's sexual behavior, vaginal temperature and lubricating were observed by thermometer and water absorption test paper, vagina surface tension was observed by multi-channel physiological recorder. Various stains were used to observe the vaginal morphology, blood vessels, nerves, muscles and fibers of vaginal tissue.Results: (1) Different modeling methods and time will cause atrophy in the vagina and uterus in different groups (F=169.4, p<0.01; F=114.3, p<0.01), among which VD2H has less effect, while OVX and VD4H have more. The influence of the two methods combination makes the atrophy more obvious. (2) Vaginal dilation had no significant effect on E2, T and DA (F=147.6, p>0.05), but the contents of these three hormones decreased after ovariectomy (F=480.9, p<0.01). (3) Except for VD2H, the acceptance of sexual response in other groups were decreased (F=58.4, p<0.01), the aggressive was increased (F=121.1, p<0.01), and the lordosis were also decreased (F=67.9, p<0.01). Besides, the vaginal lubrication and vaginal contractions were decreased (F=61.3, p<0.01), but the vaginal temperature did not change significantly in each group (F=38.4, p>0.05). (4) Different modeling methods caused different damage and atrophy in the vaginal tissue, which showed that the thickness of epithelial and muscle layer was reduced, the fibrosis was deepened, the content of muscle, nerve fibers and glycogen were reduced. The above phenomenon was most obvious in the OVX&VD4H group, and the VD2H group was the least. Compared with 1 month, the vaginal tissue had restored at 2 months in most groups. (5) Ovariectomy and vaginal dilation both decreased the number of vaginal microvascular (F=5.4, p<0.05), and the contents of VEGF and MMP-9 decreased (F=367.9, p<0.01; F=121.3, p<0.01), particularly, VD4H decreased more than VD2H (F=117.3, p<0.01), OVX&VD4H was more than OVX&VD2H (F=413.3, p<0.01), and in 2 months, their levels all increased to varying degrees. (6) Vaginal atrophy occurred after blood flow occlusion, manifested as uniform atrophy of the entire vaginal thickness and aggravated fibrosis. The weights of vagina and uterus were both lower than sham group (F=13.7, p<0.01; F= 12.1, p<0.01), the estrous cycle was disturbed, and these manifestations were more obvious in bilateral blood flow occlusion than unilateral occlusion. (7) The number of microvascular in the vaginal tissue were decreased after blood flow occlusion (F=16.4, p<0.01), and the contents of VEGF and MMP-9 also decreased (F=669.1, p<0.01; F=793.1, p<0.01), in which bilateral blockade was more obvious than unilateral blockade. After WB experiment, it was found that the contents of VEGF and ERK decreased after blood flow blockade, and the decrease in bilateral blockade group was more than that in unilateral blockade group.Conclusion: By simulating different modeling methods and time, we believe that a stable and novel PGAD mouse model can be established after ovariectomy combined with vaginal dilation for 2 hours (OVX&VD2H) and rearing for 1 month. In addition, through a large number of experiments, we screened that sexual behavior, vaginal lubricating, vagina surface tension can be used to detect sexual function in mice objectively and accurately, but vaginal temperature not suitable for the detection of mouse sexual function. Finally, we further verified that microvascular injury can significantly appeared in the model, and the VEGF-ERK signaling pathway is a possible mechanism involved in microvascular injury.