Effect Of Sacubitril/Valsartan On Blood Pressure And Vaginal Fibrosis In Female Spontaneously Hypertensive Rats

Objective: Hypertension is an important risk factor for cardiovascular diseases and cerebrovascular diseases.Hypertension causes the damage of heart,brain,kidney and peripheral blood vessels,which are considered as hypertension mediated organ damage(HMOD).Our previous study has shown that hypertension results in the main organ damage,including female sexual dysfunction(FSD).Elevating blood pressure can result in the vaginal and clitoral dysfunction,then,it will cause genital fibrosis.Therefore,the lower reproductive tract can be regarded as one of the HMOD in female patients with hypertension.The main components of SAC/VAL are neprilysin inhibitors and angiotensin receptor blockers.Neprilysin inhibitors can reduce the degradation of natriuretic peptide.Besides,valsartan has the effects of anti-proliferation and anti-fibrosis.Therefore,we hypothesized that SAC/VAL improved the vagina fibrosis of spontaneous hypertensive rats(SHRs).To study the effect of SAC/VAL on vaginal fibrosis,we evaluated sexual cycle and vaginal fibrosis in female SHRs.Methods: Twelve-week age female SHRs were randomly divided into SHR group(n = 10),SHR+VAL group(n = 10)and SHR+SAC/VAL group(n = 10).Wistar-Kyoto(WKY)group(n = 10)was considered as control group.The rats in SHR group and WKY group were given intragastric administration of autoclaved water.The systolic blood pressure(SBP)and diastolic blood pressure(DBP)were measured by tail-cuff method before treatments.After four-week-treatment,the following experiments were carried out:(1)blood pressure measurement: SBP and DBP were assessed;(2)vaginal smear papanicolaou staining: estrus cycle was detected by rats.(3)according to the results of vaginal smears,the morphology of vaginal epithelium was observed by hematoxylin-eosin(H&E),the area of vaginal f was measured by Masson staining.The protein expression of collagen-Ⅰ andcollagen-Ⅲ in vaginal tissue were detected by Western blotting.The measurement data were expressed as mean ± standard deviation((?) ± SD).The data obtained from the experiment was processed by Graph Pad Prism 8 Software.One-way analysis of variance was used for comparison between multiple groups.P < 0.05 was considered significant.Results:(1)Blood pressure: Compared to SHR,SBP [(119.18 ± 5.84)vs(145.78± 16.4)mmHg,(P < 0.05)] and DBP [(88.54 ± 8.2)vs(110.23 ± 14.89)mmHg,P <0.01] in the SHR+SAC/VAL group were significantly lower than those in the SHR group.Compared to the SHR+VAL group,SBP [(122.74 ± 13.03)vs(119.18 ±5.84)mmHg,(P > 0.05)] and DBP [(100.72 ± 8.99)vs(88.54 ±8.26)mmHg] in SHR+SAC/VAL group,there was no significant difference between two treatment groups.(2)Vaginal smears: the results of vaginal smears showed that compared to the SHR group,the SHR+SAC/VAL and SHR+VAL groups significantly prolonged the periods of estrus and proestrus,which suggested the improvement of sexual cycle.The SHR + SAC/VAL group has longer the periods of estrus and metestrus than the SHR + VAL group,and the improvement of sexual cycle was obvious.(3)H&E staining of vaginal tissue: the thickness of vaginal epithelium in WKY group was order,and there was no morphological change and few collagen fiber deposition.The thickness of vaginal epithelium was significantly decreased in the SHR group.The morphology was disordered,and much collagen fibers were deposited in the SHR group.The thickness of vaginal epithelium in the SHR+VAL group was thinner than that in the WKY group,which was better than that in the SHR group.The morphology was slightly disordered in the SHR+VAL group,with a small amount of collagen fibers were deposited.The thickness of vaginal epithelium in the SHR+SAC/VAL group was improved obviously,and a very small amount of collagen fibers were deposited,arranged neatly and regularly in morphology.(4)Masson staining: the WKY group had very little blue staining substance,which indicated that there was almost no proliferation of collagen fibers,while the large blue staining area in SHR group showed that there were a large number of collagen fibers in disordered and irregular arrangement,and the vaginal collagen volume fraction measured was significantly higher than that in WKY group(P < 0.05).The area of collagen fibers and the volume ratio of vaginal collagen in SHR+VAL group and SHR+SAC/VAL group were significantly lower than those in SHR group,and the difference was statistically significant.The improvement in SHR+SAC/VAL group was more obvious than that in SHR+VAL group,and the degree of fibrosis was the slightest.(5)Westernblot results: compared with Wistar rats,the relative expression of collagen-Ⅰ andcollagen-Ⅲ in vaginal tissue of SHR group was significantly increased,Col-Ⅰ[(2.04±0.12)vs(0.77±0.07),(P < 0.01)],Col-Ⅲ [(1.72±0.04)vs(0.39±0.10),(P< 0.01).Compared with SHR group,the expression of Col-Ⅰ and Col-Ⅲ in vaginal tissue of SHR+SAC/VAL group and SHR+VAL group was significantly lower,and which was lower in SHR+ SAC/VAL group than in SHR+VAL group(P < 0.05).Conclusion: SAC/VAL reduces blood pressure in female SHRs;SAC/VAL reduces the protein expression of Col-Ⅰ and Col-Ⅲ in SHR vagina,and it decreases collagen fiber production as well,thus inhibiting vaginal tissue fibrosis,and improving their estrus cycle and improving sexual function in female SHRs.