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Introducción y objetivos: Se ha estudiado la localización anatómica, las propiedades biomecánicas y el fenotipo molecular del colágeno miocárdico tisular en 40 pacientes con estenosis aórtica grave, fracción de eyección conservada y síntomas de insuficiencia cardiaca. Métodos: Se obtuvieron 2 biopsias transmurales de la pared libre del ventrículo izquierdo. La fracción del volumen de colágeno (FVC) se cuantificó mediante rojo picrosirio y la rigidez, mediante el módulo elástico de Young (YEM) evaluado con microscopia de fuerza atómica en regiones misiales y no misiales. Las FVC de tipos I y III se cuantificaron mediante microscopia confocal en áreas con determinación del YEM. Resultados: Comparados con sujetos de control, la FVC misial y no misial y el cociente FVC no misial:misial (p < 0,05) estaban incrementados en los pacientes. El cociente entre la velocidad pico de la onda E mitral y la velocidad E del anillo lateral mitral de los pacientes se correlacionaba con la FVC no misial (r = 0,330; p = 0,046) y con el cociente FVC no misial:misial (r = 0,419; p = 0,012). El cociente FVCI:FVCIII y el YEM aumentaban (p ≤ 0,001) en regiones no misiales respecto de las misiales, con correlación entre ellos (r = 0,895; p < 0,001). Conclusiones: En la estenosis aórtica grave con fracción de eyección conservada y síntomas de insuficiencia cardiaca, la disfunción diastólica se asocia con un depósito no misial de colágeno aumentado, predominantemente de tipo I y con mayor rigidez. Las características del colágeno tisular pueden contribuir a la disfunción diastólica en estos pacientes (AU)

Introduction and objectives: We investigated the anatomical localization, biomechanical properties, and molecular phenotype of myocardial collagen tissue in 40 patients with severe aortic stenosis with preserved ejection fraction and symptoms of heart failure. Methods: Two transmural biopsies were taken from the left ventricular free wall. Mysial and nonmysial regions of the collagen network were analyzed. Myocardial collagen volume fraction (CVF) was measured by picrosirius red staining. Young's elastic modulus (YEM) was measured by atomic force microscopy in decellularized slices to assess stiffness. Collagen types I and III were measured as CIVF and CIIIVF, respectively, by confocal microscopy in areas with YEM evaluation. Results: Compared with controls, patients exhibited increased mysial and nonmysial CVF and nonmysial:mysial CVF ratio (P < .05). In patients, nonmysial CVF (r = 0.330; P = .046) and the nonmysial:mysial CVF ratio (r = 0.419; P = .012) were directly correlated with the ratio of maximal early transmitral flow velocity in diastole to early mitral annulus velocity in diastole. Both the CIVF:CIIIVF ratio and YEM were increased (P ≤ .001) in nonmysial regions compared with mysial regions in patients, with a direct correlation (r = 0.895; P < .001) between them. Conclusions: These findings suggest that, in patients with severe aortic stenosis with preserved ejection fraction and symptoms of heart failure, diastolic dysfunction is associated with increased nonmysial deposition of collagen, predominantly type I, resulting in increased extracellular matrix stiffness. Therefore, the characteristics of collagen tissue may contribute to diastolic dysfunction in these patients (AU)

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INTRODUCTION AND OBJECTIVES: We investigated the anatomical localization, biomechanical properties, and molecular phenotype of myocardial collagen tissue in 40 patients with severe aortic stenosis with preserved ejection fraction and symptoms of heart failure. METHODS: Two transmural biopsies were taken from the left ventricular free wall. Mysial and nonmysial regions of the collagen network were analyzed. Myocardial collagen volume fraction (CVF) was measured by picrosirius red staining. Young's elastic modulus (YEM) was measured by atomic force microscopy in decellularized slices to assess stiffness. Collagen types I and III were measured as CIVF and CIIIVF, respectively, by confocal microscopy in areas with YEM evaluation. RESULTS: Compared with controls, patients exhibited increased mysial and nonmysial CVF and nonmysial:mysial CVF ratio (P < .05). In patients, nonmysial CVF (r = 0.330; P = .046) and the nonmysial:mysial CVF ratio (r = 0.419; P = .012) were directly correlated with the ratio of maximal early transmitral flow velocity in diastole to early mitral annulus velocity in diastole. Both the CIVF:CIIIVF ratio and YEM were increased (P ≤ .001) in nonmysial regions compared with mysial regions in patients, with a direct correlation (r = 0.895; P < .001) between them. CONCLUSIONS: These findings suggest that, in patients with severe aortic stenosis with preserved ejection fraction and symptoms of heart failure, diastolic dysfunction is associated with increased nonmysial deposition of collagen, predominantly type I, resulting in increased extracellular matrix stiffness. Therefore, the characteristics of collagen tissue may contribute to diastolic dysfunction in these patients.

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Phospholipase C-beta (PLCbeta) isozymes (PLCbeta(1) and PLCbeta(3)) have been extensively characterized in cardiac tissue, but no data are available for the PLCbeta(4) isozyme. In this study, PLCbeta((1-4)) isozymes mRNA relative expression was studied by real-time PCR (RT-PCR) in human, rat, and murine left ventricle and the presence of PLCbeta(4) isozyme at the protein level was confirmed by Western blotting in all species studied. Confocal microscopy experiments carried out in HL-1 cardiomyocytes revealed a sarcoplasmic subcellular distribution of PLCbeta(4). Although there were unexpected significant interspecies differences in the PLCbeta((1-4)) mRNA expression, PLCbeta(4) mRNA was the main transcript expressed in all left ventricles studied. Thus, whereas in human and rat left ventricles PLCbeta(4) > PLCbeta(3) > PLCbeta(2) > PLCbeta(1) mRNA pattern of expression was found, in murine left ventricle the pattern of expression was different, i.e., PLCbeta(4) > PLCbeta(1) > PLCbeta(3) > PLCbeta(2). However, results obtained in mouse HL-1 cardiomyocytes showed PLCbeta(3) approximately PLCbeta(4) > PLCbeta(1) > PLCbeta(2) pattern of mRNA expression indicating a probable cell type specific expression of the different PLCbeta isozymes in cardiomyocytes. Finally, RT-PCR experiments showed a trend, even though not significant (P = 0.067), to increase PLCbeta(4) mRNA levels in HL-1 cardiomyocytes after angiotensin II treatment. These results demonstrate the presence of PLCbeta(4) in the heart and in HL-1 cardiomyocytes showing a different species-dependent pattern of expression of the PLCbeta((1-4)) transcripts. We discuss the relevance of these findings in relation to the development of cardiac hypertrophy.

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