Noninvasive Detection For Myocardial Fibrosis And Drugs Intervention Research In SHRs

OBJECTIVETo evaluate the value of quantitative acoustic densitometry(AD) technique and Serological indicators in myocardial fibrosis diagnosis and to explore the effects of benazepril and valsartan on myocardial fibrosis.METHODSSixty ten-week-old male spontaneously hypertensive rats(SHRs) were randomly equally assigned to control group(SHRc group),benazepril group(SHRb group),valsartan group(SHRv group) and combination group(SHRb+v group),which were subjected to an intragastic administration for ten weeks.Fifteen male age-matched Wistar-Kyoto(WKY) rats served as the control group.The integrated backscatter(IBS) and cyclic variation of integrated backscatter (CVIB) were assessed with the AD technique.The cardiac collagen volume fraction(CVF) and perivascular circumferential area(PVCA) were determined by Masson staining.The serum concentrations of procollagen typeⅠcarboxy-terminal propeptide(PⅠCP),procollagen typeⅢamino-terminal propeptide(PⅢNP),matrix metalloproteinase-2(MMP-2),matrix metalloproteinase-9(MMP-9) and tissue inhibitom of metalloproteinase-1(TIMP-1) were obtained by radioimmunoassay or by enzyme-linked immunosorbent assays(ELISA).Myocardial hyproline concentration(HC) were measured by a spectrophotometric method.Also,body weight(BW),systolic blood pressure(SBP),left ventricular mass(LVM) and left ventricular mass index(LVMI) were observed.Correlation analysis among the above indexes was analyzed.RESULTS1) BW,SBP,LVM,LVMI and HC:The mean body weight of SHRb group was slightly lower than other groups,but the differences had no statistically significant(P＞0.05).Compared with WKY group,levels of SBP,LVM,LVMI and HC were all significantly increased in SHRc group(P＜0.01),and the indexes were substantially ameliorate in three treated SHR groups(P＜0.01).The combination group showed a more pronounced amelioration in LVMI and HC than the other two monotherapy groups(P＜0.05,P＜0.01),however,this difference was not be found between the monotherapy groups(P＞0.05).There had no significant difference in SBP among three treated SHR groups(P＞0.05).2) Myocardial Acoustic Densitometry:Compared with WKY group,the normalized values of integrated backscatter(IB%) at interventricular septum and left ventricular posterior wall were all significantly increased in SHRc group(P＜0.01),while CVIB was significantly decreased(P＜0.01),and the indexes were substantially ameliorate in three treated SHR groups(P＜0.05,P＜0.01).The combination group showed a most pronounced amelioration both in IB%and CVIB.3) Muscular tissues structure and collagen disposition:Myocardial fibers arranged regularly and tightly in WKY.A amall quantity collagen deposited arouding the arterioles,but it seltom extended to matrix.The collagen fibers were distributed randomly or seeming long trabs.Compared with WKY group,cardiocytes swelled and fibers arranged disorderly and loosely in SHRc.Collagen significantly increased and cross-linked seeming graticule arrouding the arterioles and in matrix.These abnormities were substantially ameliorate in three treated SHR groups,and the combination group showed a more pronounced amelioration than the other two monotherapy groups.4) CVF and PVCA:Compared with WKY group,levels of CVF and PVCA were both significantly increased in SHRc group(P＜0.01),and they were substantially ameliorate in three treated SHR groups(P＜0.01).The combination group showed a more pronounced effect than the other two monotherapy groups(P＜0.01),however, this difference was not be found between the monotherapy groups(P＞0.05).5) The serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1: Compared with WKY group,the serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1 were all significantly increased in SHRc group(P＜0.01).Except for TIMP-1,the levels of indexes were substantially decreased in three treated SHR groups(P＜0.01),and the combination group showed a more pronounced effect than the other two monotherapy groups(P＜0.05,P＜0.01),however,this difference was not be found between the monotherapy groups(P＞0.05).There had no significant difference in the concentration of TIMP-1 among three treated SHR groups(P＞0.05).6) The relationship between myocardial ultrasonic backscatter parameters and CVF or PVCA:IB%at interventricular septum and left ventricular posterior wall were positively related to CVF(r=0.731,0.756,P＜0.01)and PVCA(r=0.776,0.788, P＜0.01) in SHR groups,while both CVIBs were inversely related to CVF(r=-0.642,-0.716,P＜0.01)and PVCA(r=-0.720,-0.755,P＜0.01).The correlations above were not observed in WKY group(P＞0.05).7) The relationship between serum indexes and CVF or PVCA:The serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1 were positively related to CVF(r=0.866,0.867,0.859,0.893,0.662,P＜0.01)and PVCA(r=0.761,0.789,0.799,0.855,0.658,P＜0.01).8) The relationship between serum indexes and myocardial ultrasonic backscatter parameters:IB%at interventricular septum and left ventricular posterior wall were positively related to PⅠCP(r=0.576,0.602,P＜0.01),PⅢNP(r=0.425,0.455,P＜0.01, P＜0.01),MMP-2(r=0.470,0.483,P＜0.01),MMP-9(r=0.554,0.566,P＜0.01)in SHR groups,while both CVIBs were inversely related to PⅠCP(r=-0.591,-0.631, P＜0.01),PⅢNP(r=-0.505,-0.533,P＜0.01),MMP-2(r=-0.549,-0.553,P＜0.01),MMP-9(r=-0.645,-0.640,P＜0.01).The serum concentration of TIMP-1 was positively related to IB%at interventricular septum and left ventricular posterior wall(r=0.509,0.526,P＜0.01),but it had no relation to both CVIBs(P＞0.05).The correlations above were not observed in WKY group(P＞0.05).CONCLUSION 1) Normal myocardial ultrasonic backscatter parameters are not dependented to collagen contents.But while hypertensive myocardial fibrosis exist,ultrasonic backscatter parameters are closely correlated with the alteration of myocardial collagen contents.2) The serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1 are closely correlated with the alteration of myocardial collagen contents.3) While hypertensive myocardial fibrosis exist,myocardial ultrasonic backscatter parameters are closely correlated with the serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1.4) Quantitative myocardial acoustic densitometry is a reliable technique for detecting myocardial fibrosis and evaluating its severity.5) The serum concentrations of PⅠCP,PⅢNP,MMP-2,MMP-9 and TIMP-1 are useful indexes for detecting myocardial fibrosis and evaluating its severity.6) Benazepril and valsartan decrease the blood pressure and can reverse an early myocardial fibrosis in SHRs.Half-value dose of benazepril in combination with valsartan is more effective in ameliorating myocardial fibrosis than either one alone.