Heart remodeling is associated with the loss of cardiomyocytes and increase of fibrous tissue owing to abnormal mechanical load in a number of heart disease conditions. In present study, a well-described in vitro sust...Heart remodeling is associated with the loss of cardiomyocytes and increase of fibrous tissue owing to abnormal mechanical load in a number of heart disease conditions. In present study, a well-described in vitro sustained stretch model was employed to study mechanical stretch-induced responses in both neonatal cardiomyocytes and cardiac fibroblasts. Cardiomyocytes, but not cardiac fibroblasts, underwent mitochondria-dependent apoptosis as evidenced by cytochrome c (cyto c) and Smac/DIABLO release from mitochondria into cytosol accompanied by mitochondrial membrane potential (△ψ_m) reduction, indicative of mitochondrial permeability transition pore (PTP) opening. Cyclosporin A, an inhibitor of PTP, inhibited stretch-induced cyto c release, △ψ_m reduction and apoptosis, suggesting an important role of mitochondrial PTP in stretch-induced apoptosis. The stretch also resulted in increased expression of the pro-apoptotic Bcl-2 family proteins, including Bax and Bad, in cardiomyocytes, but not in fibroblasts. Bax was accumulated in mitochondria following stretch. Cell permeable Bid-BH3 peptide could induce and facilitate stretch-induced apoptosis and △ψ_m reduction in cardiomyocytes. These results suggest that Bcl-2 family proteins play an important role in coupling stretch signaling to mitochondrial death machinery, probably by targeting to PTP. Interestingly, the levels of p53 were increased at 12 h after stretch although we observed that Bax upregulation and apoptosis occurred as early as 1 h. Adenovirus delivered dominant negative p53 blocked Bax upregulation in cardiomyocytes but showed partial effect on preventing stretch-induced apoptosis, suggesting that p53 was only partially involved in mediating stretch-induced apoptosis. Furthermore, we showed that p21 was upregulated and cyclin B1 was downregulated only in cardiac fibroblasts, which may be associated with G_2/M accumulation in response to mechanical stretch.展开更多
The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaf...The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaffolds for the cardiac tissue engineering, either in a form of thin membranes or electrospun fiber mats. The results show that cardiac cells of various origins can be successfully grown on PHB substrates, in the both forms： membrane and nanofiber matrix. Functioning of obtained tissue patches was tested by visual observation of contractions and with the aid of optical mapping, i.e., registration of excitation waves with fluorescent markers. The latter one allowed ensuring the fact that cultured cells represented electrophysiological syncytium, and the PHB scaffold showed its full compatibility with the excitability of cardiac cells.展开更多
The T-tubule (TT) system forms the structural basis for excitation-contraction coupling in heart and muscle cells. The morphogenesis of the TT system is a key step in the maturation of heart cells because it does not ...The T-tubule (TT) system forms the structural basis for excitation-contraction coupling in heart and muscle cells. The morphogenesis of the TT system is a key step in the maturation of heart cells because it does not exist in neonatal cardiomyocytes. In the present study, we quantified the morphological changes in TTs during heart cell maturation and investigated the role of junctophilin-2 (JP2), a protein known to anchor the sarcoplasmic reticulum (SR) to TT, in changes to TT morphological parameters. Analysis of confocal images showed that the transverse elements of TTs increased, while longitudinal elements decreased during the maturation of TTs. Fourier transform analysis showed that the power of ~2 m spatial components increased with cardiomyocytes maturation. These changes were preceded by increased expression of JP2, and were reversed by JP2 knockdown. These findings indicate that JP2 is required for the morphogenesis of TTs during heart development.展开更多
Although microRNAs （miRNAs） have been intensively studied in cardiac fibrosis, their roles in drug-mediated anti-fibrotic therapy are still unknown. Previously, Pioglitazone attenuated cardiac fibrosis and increased...Although microRNAs （miRNAs） have been intensively studied in cardiac fibrosis, their roles in drug-mediated anti-fibrotic therapy are still unknown. Previously, Pioglitazone attenuated cardiac fibrosis and increased miR-711 experimentally. We aimed to explore the role and mechanism of miR-711 in pioglitazone-treated myocardial infarction in rats. Our results showed that pioglitazone significantly reduced collagen-I levels and increased miR-711 expression in myocardial infarction heart. Pioglitazone increased the expression of miR-711 in cardiac fibroblasts, and overexpression of miR-711 suppressed collagen-I levels in angiotensin II （Ang II）-treated or untreated cells. Transfection with antagomir-711 correspondingly abolished the pioglitazone-induced reduction in collagen-I levels. Bioinformatics analysis identified SP1, which directly promotes collagen-I synthesis, as the putative target of miR-711. This was confirmed by luciferase assay and western blot analysis. Additionally, increased SP1 expression was attenuated by pioglitazone in myocardial infarction heart. Furthermore, transfection of antago- mir-711 attenuated pioglitazone-reduced SP1 expression in cardiac fibroblasts with or without Ang II stimulation. We conclude that pioglitazone up-regulated miR-711 to reduce collagen-I levels in rats with myocardial infarction. The miR-711-SPl-collagen-I pathway may be involved in the anti-fibrotic effects of pioglitazone. Our findings may provide new strategies for miRNA-based anti-fibrotic drug research.展开更多
基金supported by Research Grants(No.30170467)Outstanding Young Scientist Award from National Natural Sciences Foundation of China(QC)+2 种基金the“Major National Basic Research Program(973 Program,No.G2000056904)”(LYC)the KIKP Projects in Chinese Academy of Sciences(QC)the Ph.D.Programs Foundation from the Ministry of Education of China(LYC).
文摘Heart remodeling is associated with the loss of cardiomyocytes and increase of fibrous tissue owing to abnormal mechanical load in a number of heart disease conditions. In present study, a well-described in vitro sustained stretch model was employed to study mechanical stretch-induced responses in both neonatal cardiomyocytes and cardiac fibroblasts. Cardiomyocytes, but not cardiac fibroblasts, underwent mitochondria-dependent apoptosis as evidenced by cytochrome c (cyto c) and Smac/DIABLO release from mitochondria into cytosol accompanied by mitochondrial membrane potential (△ψ_m) reduction, indicative of mitochondrial permeability transition pore (PTP) opening. Cyclosporin A, an inhibitor of PTP, inhibited stretch-induced cyto c release, △ψ_m reduction and apoptosis, suggesting an important role of mitochondrial PTP in stretch-induced apoptosis. The stretch also resulted in increased expression of the pro-apoptotic Bcl-2 family proteins, including Bax and Bad, in cardiomyocytes, but not in fibroblasts. Bax was accumulated in mitochondria following stretch. Cell permeable Bid-BH3 peptide could induce and facilitate stretch-induced apoptosis and △ψ_m reduction in cardiomyocytes. These results suggest that Bcl-2 family proteins play an important role in coupling stretch signaling to mitochondrial death machinery, probably by targeting to PTP. Interestingly, the levels of p53 were increased at 12 h after stretch although we observed that Bax upregulation and apoptosis occurred as early as 1 h. Adenovirus delivered dominant negative p53 blocked Bax upregulation in cardiomyocytes but showed partial effect on preventing stretch-induced apoptosis, suggesting that p53 was only partially involved in mediating stretch-induced apoptosis. Furthermore, we showed that p21 was upregulated and cyclin B1 was downregulated only in cardiac fibroblasts, which may be associated with G_2/M accumulation in response to mechanical stretch.
文摘The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaffolds for the cardiac tissue engineering, either in a form of thin membranes or electrospun fiber mats. The results show that cardiac cells of various origins can be successfully grown on PHB substrates, in the both forms： membrane and nanofiber matrix. Functioning of obtained tissue patches was tested by visual observation of contractions and with the aid of optical mapping, i.e., registration of excitation waves with fluorescent markers. The latter one allowed ensuring the fact that cultured cells represented electrophysiological syncytium, and the PHB scaffold showed its full compatibility with the excitability of cardiac cells.
基金supported by the National Basic Research Program of China (2011CB809101)the National Natural Science Foundation of China (30730013)
文摘The T-tubule (TT) system forms the structural basis for excitation-contraction coupling in heart and muscle cells. The morphogenesis of the TT system is a key step in the maturation of heart cells because it does not exist in neonatal cardiomyocytes. In the present study, we quantified the morphological changes in TTs during heart cell maturation and investigated the role of junctophilin-2 (JP2), a protein known to anchor the sarcoplasmic reticulum (SR) to TT, in changes to TT morphological parameters. Analysis of confocal images showed that the transverse elements of TTs increased, while longitudinal elements decreased during the maturation of TTs. Fourier transform analysis showed that the power of ~2 m spatial components increased with cardiomyocytes maturation. These changes were preceded by increased expression of JP2, and were reversed by JP2 knockdown. These findings indicate that JP2 is required for the morphogenesis of TTs during heart development.
基金supported by the National Natural Science Foundation of China (81100164,31271212,81070196,81030001)the Research Fund for the Doctoral Program of Higher Education (20100001110101,20110001120015)the Program for New Century Excellent Talents in University,the Beijing Talents Foundation
文摘Although microRNAs （miRNAs） have been intensively studied in cardiac fibrosis, their roles in drug-mediated anti-fibrotic therapy are still unknown. Previously, Pioglitazone attenuated cardiac fibrosis and increased miR-711 experimentally. We aimed to explore the role and mechanism of miR-711 in pioglitazone-treated myocardial infarction in rats. Our results showed that pioglitazone significantly reduced collagen-I levels and increased miR-711 expression in myocardial infarction heart. Pioglitazone increased the expression of miR-711 in cardiac fibroblasts, and overexpression of miR-711 suppressed collagen-I levels in angiotensin II （Ang II）-treated or untreated cells. Transfection with antagomir-711 correspondingly abolished the pioglitazone-induced reduction in collagen-I levels. Bioinformatics analysis identified SP1, which directly promotes collagen-I synthesis, as the putative target of miR-711. This was confirmed by luciferase assay and western blot analysis. Additionally, increased SP1 expression was attenuated by pioglitazone in myocardial infarction heart. Furthermore, transfection of antago- mir-711 attenuated pioglitazone-reduced SP1 expression in cardiac fibroblasts with or without Ang II stimulation. We conclude that pioglitazone up-regulated miR-711 to reduce collagen-I levels in rats with myocardial infarction. The miR-711-SPl-collagen-I pathway may be involved in the anti-fibrotic effects of pioglitazone. Our findings may provide new strategies for miRNA-based anti-fibrotic drug research.
