Hypertension Accelerates The Development And Progression And Its Potential Mechanisms Of Both Aging And Calcification In Aorta

Part One Hypertension accelerates the development and progression of vascular remodeling and aging as well as calcification in aorta.Objective To observe the dynamic changes of the aortic remodeling,aging,and calcification in both spontaneously hypertensive rats(SHR)and congenic wistar-kyoto normotensive rats(WKY)with aging and to prove that hypertension can accelerate vascular remodeling,aging and calcification in aorta.Methods Male SHRs were randomly divided into 4-week old group(4w),12-week old group(12w),24-week old group(24w),48-week old group(48w)and 72-week old group(72w).The male WKY rats with the same age severed as the control group(each group,n=10).The systolic blood pressure(SBP),the degree of aging in aorta(senescence associated ?-galactosidase staining),the morphology of aortic wall(HE staining,immunofluorescence staining and EVG staining),the calcium content of aortic wall(flame atomic absorption spectrophotometer method)and the degree of aortic calcification(von Kossa staining)were measured in both SHRs and WKY rats respectively.Results(1)Except the 4w group,SHRs have higher SBP than the age-matched WKY rats(p<0.01).(2)Few senescent cells were only observed in WKY rats at the age of 72 w.As compared with WKY rats,the senescent cells were observed in SHRs as early as 24 w and increased gradually with aging,obviously at age of 72 w.(3)The vascular smooth muscle cells(VSMCs)were the major cell type in the thickened media of the remodeling aorta which was caused by aging or hypertension.The morphological change of the aging-related vascular remodeling were observed in WKY rats at the age of 72 w,including the thickened media,the decreased contractile type VSMCs,the fracture tortuosity of the elastic fiber,and the relatively higher collagen content;however,the pathological changes in vascular remodeling were observed in SHR from the age of 24 w and aggravated with aging.The 72 w SHR group was the most obviously among all age groups.Compared with WKY rats,SHR showed a significant aggravation in vascular remodeling from 24 w to 72 w.(4)The calcium content of the aortic wall in WKY started to increase at the age of 72w(p<0.05),while the increase of the calcium content was brought forward to 48 w in SHR(p<0.05).The calcium content in SHR was already significantly higher than WKY at the age of 48w(p<0.05)and 72w(p<0.01).The von Kossa staining showed that the calcium deposition was distributed dispersedly along the membrane elastic fiber and was aggravated with the increase of age.The calcium deposition in WKY started to increase at the age of 72 w,while the significant increase of the calcium deposition was brought forward to 48 w in SHR.It aggravated obviously in SHR than WKY at the age of 48 w and 72 w.Conclusions(1)Aging-related vascular remodeling and hypertension-related vascular remodeling have common pathological changes to a certain extent.(2)Hypertension accelerates the pathogenesis progess of the vascular remodeling,aging and calcification in aorta.Part Two The dynamic changes of BMP2,MGP,Runx2,Osx and the phenotypic transformation of VSMCs in vascular calcification during aging.Objective In order to further clarify the potential mechanisms underlying the calcification of media in aging artery due to hypertension,the dynamic changes in the expression of bone morphogenetic protein 2(BMP2),matrix Gla protein(MGP),runt-related transcription factor 2(Runx2),osterix(Osx,a kind of transcription factor for bone formation),and the phenotypic transformation of VSMCs were studied during the aortic remodeling and calcification in both SHR and WKY.Methods The dynamic changes of BMP2,MGP,Runx2,Osx,?-smooth muscle actin(?-SMA),smooth muscle 22?(SM22?),alkaline phosphatase(ALP)and type I collagen were analyzed and compared by immunofluorescence staining,immunohistochemical staining,Real-time PCR and Western Blotting in all groups of SHR and WKY.Results(1)The expression of BMP2,Runx2 and Osx increased with aging,while the expression of MGP decreased with aging in both SHR and WKY rats.The trend of increase or decrease was more significant in SHR than in WKY.Both m RNA and protein expression of BMP2,MGP,Runx2 and Osx in WKY rats at the age of 72 w mostly showed a statistically significant change by comparing with early stages,while the statistically significant changes were found as early as 24 w and thus the comparison between SHR and WKY at the age of 48 w and 72 w was significant as well.(2)The expression of ?-SMA and SM22? decreased with age and the decrease was significant in WKY rats at the age of 72 w.In SHR,the decrease of ?-SMA and SM22? was brought forward to 48 w and 24 w respectively,and the decrease of ?-SMA at the age of 48 w and 72 w was more remarkable than in WKY rats.The expression of SM22? at the age of 24w-72 w was significantly lower in SHRs than in WKY.The expression of ALP and type I collagen increased with age.In WKY,the expression of ALP started to increase in WKY rats at the age of 72 w,and type I collagen increased at the 48 w and 72 w groups.While both the increase of ALP and type I collagen was brought forward to 24 w in SHR.The higher expression of ALP and type I collagen was observed in SHRs than WKY rats from 24w-72 w.Conclusions(1)This study shows that the imbalance of BMP2/MGP,the up-regulation of Runx2 and Osx,and the transformation of the contractile type VSMCs into the osteoblast-like cells,may be the important mechanisms underlying the occurrence and development of the vascular aging and calcification.(2)This study suggests that hypertension accelerates and aggravates the vascular aging and calcification through above processes.Part Three The dynamic changes of fibronectin(FN)and its receptor integrin ?5 in the development of aortic aging and calcification caused by hypertension.Objective By comparing the dynamic expression changes of FN,EDA-FN and integrin ?5 in the aging of SHR and WKY rats,we analyzed their roles in the development of aortic aging and calcification due to hypertension.Methods The immunohistochemical staining,Real-time PCR and Western Blotting were used to measure the dynamic changes for both the m RNA and protein expressions of ECM related proteins including FN,EDA-FN and integrin ?5 in different age groups of SHR and to compare with the corresponding age groups of WKYs.Results(1)FN and EDA-FN were expressed in the media of artery,with low level of both m RNA and protein expressions in WKY rats(no significant difference in the 4w-48 w groups).Only WKY rats at the age of 72 w had a significant increase in m RNA transcription and protein expression(p<0.01 or p<0.05).Compared with the corresponding age groups in WKY,SHR had much earlier and higher expression at both the m RNA and protein level of FN and EDA-FN(p<0.01 or p<0.05),with mostly starting at the age of 24 w.(2)The expression of integrin ?5 was mainly in the media and decreased with the aortic aging in both SHR and WKY,with more significant decrease in WKY.The significant decrease of integrin ?5 m RNA and protein expression started at the age of 48 w in both SHR and WKY.However,the m RNA and protein expression of integrin ?5 in SHR were significantly higher than the WKY rats at the age of 48w(p <0.05)and 72w(p<0.01).Conclusions This study shows that hypertension accelerates and aggravates the aortic aging and calcification probably by regulating FN,EDA-FN and integrin ?5.