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Dittfeld C, Winkelkotte M, Scheer A, Voigt E, Schmieder F, Behrens S, Jannasch A, Matschke K, Sonntag F, Tugtekin SM. Challenges of aortic valve tissue culture - maintenance of viability and extracellular matrix in the pulsatile dynamic microphysiological system. J Biol Eng 2023; 17:60. [PMID: 37770970 PMCID: PMC10538250 DOI: 10.1186/s13036-023-00377-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 09/14/2023] [Indexed: 09/30/2023] Open
Abstract
BACKGROUND Calcific aortic valve disease (CAVD) causes an increasing health burden in the 21st century due to aging population. The complex pathophysiology remains to be understood to develop novel prevention and treatment strategies. Microphysiological systems (MPSs), also known as organ-on-chip or lab-on-a-chip systems, proved promising in bridging in vitro and in vivo approaches by applying integer AV tissue and modelling biomechanical microenvironment. This study introduces a novel MPS comprising different micropumps in conjunction with a tissue-incubation-chamber (TIC) for long-term porcine and human AV incubation (pAV, hAV). RESULTS Tissue cultures in two different MPS setups were compared and validated by a bimodal viability analysis and extracellular matrix transformation assessment. The MPS-TIC conjunction proved applicable for incubation periods of 14-26 days. An increased metabolic rate was detected for pulsatile dynamic MPS culture compared to static condition indicated by increased LDH intensity. ECM changes such as an increase of collagen fibre content in line with tissue contraction and mass reduction, also observed in early CAVD, were detected in MPS-TIC culture, as well as an increase of collagen fibre content. Glycosaminoglycans remained stable, no significant alterations of α-SMA or CD31 epitopes and no accumulation of calciumhydroxyapatite were observed after 14 days of incubation. CONCLUSIONS The presented ex vivo MPS allows long-term AV tissue incubation and will be adopted for future investigation of CAVD pathophysiology, also implementing human tissues. The bimodal viability assessment and ECM analyses approve reliability of ex vivo CAVD investigation and comparability of parallel tissue segments with different treatment strategies regarding the AV (patho)physiology.
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Affiliation(s)
- Claudia Dittfeld
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany.
| | - Maximilian Winkelkotte
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
| | - Anna Scheer
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
| | - Emmely Voigt
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
| | - Florian Schmieder
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - Stephan Behrens
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - Anett Jannasch
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
| | - Klaus Matschke
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
| | - Frank Sonntag
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - Sems-Malte Tugtekin
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Fetscherstr. 76, 01307, Dresden, Germany
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Bouhamida E, Morciano G, Pedriali G, Ramaccini D, Tremoli E, Giorgi C, Pinton P, Patergnani S. The Complex Relationship between Hypoxia Signaling, Mitochondrial Dysfunction and Inflammation in Calcific Aortic Valve Disease: Insights from the Molecular Mechanisms to Therapeutic Approaches. Int J Mol Sci 2023; 24:11105. [PMID: 37446282 DOI: 10.3390/ijms241311105] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/26/2023] [Accepted: 06/29/2023] [Indexed: 07/15/2023] Open
Abstract
Calcific aortic valve stenosis (CAVS) is among the most common causes of cardiovascular mortality in an aging population worldwide. The pathomechanisms of CAVS are such a complex and multifactorial process that researchers are still making progress to understand its physiopathology as well as the complex players involved in CAVS pathogenesis. Currently, there is no successful and effective treatment to prevent or slow down the disease. Surgical and transcatheter valve replacement represents the only option available for treating CAVS. Insufficient oxygen availability (hypoxia) has a critical role in the pathogenesis of almost all CVDs. This process is orchestrated by the hallmark transcription factor, hypoxia-inducible factor 1 alpha subunit (HIF-1α), which plays a pivotal role in regulating various target hypoxic genes and metabolic adaptations. Recent studies have shown a great deal of interest in understanding the contribution of HIF-1α in the pathogenesis of CAVS. However, it is deeply intertwined with other major contributors, including sustained inflammation and mitochondrial impairments, which are attributed primarily to CAVS. The present review aims to cover the latest understanding of the complex interplay effect of hypoxia signaling pathways, mitochondrial dysfunction, and inflammation in CAVS. We propose further hypotheses and interconnections on the complexity of these impacts in a perspective of better understanding the pathophysiology. These interplays will be examined considering recent studies that shall help us better dissect the molecular mechanism to enable the design and development of potential future therapeutic approaches that can prevent or slow down CAVS processes.
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Affiliation(s)
- Esmaa Bouhamida
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
| | - Giampaolo Morciano
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
| | - Gaia Pedriali
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
| | - Daniela Ramaccini
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
| | - Elena Tremoli
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
| | - Carlotta Giorgi
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
| | - Paolo Pinton
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
| | - Simone Patergnani
- Translational Research Center, Maria Cecilia Hospital GVM Care & Research, 48033 Cotignola, Italy
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
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3
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Salim MT, Villa-Roel N, Vogel B, Jo H, Yoganathan AP. HIF1A inhibitor PX-478 reduces pathological stretch-induced calcification and collagen turnover in aortic valve. Front Cardiovasc Med 2022; 9:1002067. [PMID: 36419483 PMCID: PMC9676244 DOI: 10.3389/fcvm.2022.1002067] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 10/20/2022] [Indexed: 09/19/2023] Open
Abstract
HIF1A is significantly upregulated in calcified human aortic valves (AVs). Furthermore, HIF1A inhibitor PX-478 was shown to inhibit AV calcification under static and disturbed flow conditions. Since elevated stretch is one of the major mechanical stimuli for AV calcification, we investigated the effect of PX-478 on AV calcification and collagen turnover under a pathophysiological cyclic stretch (15%) condition. Porcine aortic valve (PAV) leaflets were cyclically (1 Hz) stretched at 15% for 24 days in osteogenic medium with or without PX-478. In addition, PAV leaflets were cyclically stretched at a physiological (10%) and 15% for 3 days in regular medium to assess its effect of on HIF1A mRNA expression. It was found that 100 μM (high concentration) PX-478 could significantly inhibit PAV calcification under 15% stretch, whereas 50 μM (moderate concentration) PX-478 showed a modest inhibitory effect on PAV calcification. Nonetheless, 50 μM PX-478 significantly reduced PAV collagen turnover under 15% stretch. Surprisingly, it was observed that cyclic stretch (15% vs. 10%) did not have any significant effect on HIF1A mRNA expression in PAV leaflets. These results suggest that HIF1A inhibitor PX-478 may impart its anti-calcific and anti-matrix remodeling effect in a stretch-independent manner.
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Affiliation(s)
- Md Tausif Salim
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Nicolas Villa-Roel
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Booth Vogel
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, United States
| | - Hanjoong Jo
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Ajit P. Yoganathan
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
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Zeng Y, Zhao Y, Dai S, Liu Y, Zhang R, Yan H, Zhao M, Wang Y. Impact of lactate dehydrogenase on prognosis of patients undergoing cardiac surgery. BMC Cardiovasc Disord 2022; 22:404. [PMID: 36088306 PMCID: PMC9463775 DOI: 10.1186/s12872-022-02848-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 09/06/2022] [Indexed: 11/10/2022] Open
Abstract
Background Lactate dehydrogenase (LDH) has been reported in multiple heart diseases. Herein, we explored the prognostic effects of preoperative LDH on adverse outcomes in cardiac surgery patients. Methods Retrospective data analysis was conducted from two large medical databases: Medical Information Mart for Intensive Care (MIMIC) III and MIMIC IV databases. The primary outcome was in-hospital mortality, whereas the secondary outcomes were 1-year mortality, continuous renal replacement therapy, prolonged ventilation, and prolonged length of intensive care unit and hospital stay. Results Patients with a primary endpoint had significantly higher levels of LDH (p < 0.001). Multivariate regression analysis presented that elevated LDH was independently correlated with increased risk of primary and secondary endpoints (all p < 0.001). Subgroup analyses showed that high LDH was consistently associated with primary endpoint. Moreover, LDH exhibited the highest area under the curve (0.768) for the prediction of primary endpoint compared to the other indicators, including neutrophil–lymphocyte ratio (NLR), lymphocyte-monocyte ratio (LMR), platelet–lymphocyte ratio (PLR), lactate, and simplified acute physiology score (SAPS) II. The above results were further confirmed in the MIMIC IV dataset. Conclusions Elevated preoperative LDH may be a robust predictor of poor prognosis in cardiac surgery patients, and its predictive ability is superior to NLR, LMR, PLR, lactate, and SAPS II. Supplementary Information The online version contains supplementary material available at 10.1186/s12872-022-02848-7.
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Dittfeld C, Winkelkotte M, Behrens S, Schmieder F, Jannasch A, Matschke K, Sonntag F, Tugtekin SM. Establishment of a resazurin-based aortic valve tissue viability assay for dynamic culture in a microphysiological system. Clin Hemorheol Microcirc 2021; 79:167-178. [PMID: 34487029 DOI: 10.3233/ch-219112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND/AIM Tissue pathogenesis of aortic valve (AV) stenosis is research focus in cardiac surgery. Model limitations of conventional 2D culture of human or porcine valvular interstitial/endothelial cells (VIC/VECs) isolated from aortic valve tissues but also limited ability of (small) animal models to reflect human (patho)physiological situation in AV position raise the need to establish an in vitro setup using AV tissues. Resulting aim is to approximate (patho)physiological conditions in a dynamic pulsatile Microphysiological System (MPS) to culture human and porcine AV tissue with preservation of tissue viability but also defined ECM composition. MATERIALS/METHODS A tissue incubation chamber (TIC) was designed to implement human or porcine tissues (3×5 mm2) in a dynamic pulsatile culture in conventional cell culture ambience in a MPS. Cell viability assays based on lactate dehydrogenase (LDH)-release or resazurin-conversion were tested for applicability in the system and applied for a culture period of 14 days with interval evaluation of tissue viability on every other day. Resazurin-assay setup was compared in static vs. dynamic culture using varying substance saturation settings (50-300μM), incubation times and tissue masses and was consequently adapted. RESULTS Sterile dynamic culture of human and porcine AV tissue segments was established at a pulsatile flow rate range of 0.9-13.4μl/s. Implementation of tissues was realized by stitching the material in a thermoplastic polyurethane (TPU)-ring and insertion in the TIC-MPS-system. Culture volume of 2 ml caused LDH dilution not detectable in standard membrane integrity assay setup. Therefore, detection of resazurin-conversion of viable tissue was investigated. Optimal incubation time for viability conversion was determined at two hours at a saturated concentration of 300μM resazurin. Measurement in static conditions was shown to offer comparable results as dynamic condition but allowing optimal handling and TIC sterilization protocols for long term culture. Preliminary results revealed favourable porcine AV tissue viability over a 14 day period confirmed via resazurin-assay comparing statically cultured tissue counterparts. CONCLUSIONS Human and porcine AV tissue can be dynamically cultured in a TIC-MPS with monitoring of tissue viability using an adapted resazurin-assay setup. Preliminary results reveal advantageous viability of porcine AV tissues after dynamic TIC-MPS culture compared to static control.
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Affiliation(s)
- C Dittfeld
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden,Germany
| | - M Winkelkotte
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden,Germany
| | - S Behrens
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - F Schmieder
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - A Jannasch
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden,Germany
| | - K Matschke
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden,Germany
| | - F Sonntag
- Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany
| | - S M Tugtekin
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden,Germany
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Lerche CJ, Schwartz F, Theut M, Fosbøl EL, Iversen K, Bundgaard H, Høiby N, Moser C. Anti-biofilm Approach in Infective Endocarditis Exposes New Treatment Strategies for Improved Outcome. Front Cell Dev Biol 2021; 9:643335. [PMID: 34222225 PMCID: PMC8249808 DOI: 10.3389/fcell.2021.643335] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 05/04/2021] [Indexed: 12/13/2022] Open
Abstract
Infective endocarditis (IE) is a life-threatening infective disease with increasing incidence worldwide. From early on, in the antibiotic era, it was recognized that high-dose and long-term antibiotic therapy was correlated to improved outcome. In addition, for several of the common microbial IE etiologies, the use of combination antibiotic therapy further improves outcome. IE vegetations on affected heart valves from patients and experimental animal models resemble biofilm infections. Besides the recalcitrant nature of IE, the microorganisms often present in an aggregated form, and gradients of bacterial activity in the vegetations can be observed. Even after appropriate antibiotic therapy, such microbial formations can often be identified in surgically removed, infected heart valves. Therefore, persistent or recurrent cases of IE, after apparent initial infection control, can be related to biofilm formation in the heart valve vegetations. On this background, the present review will describe potentially novel non-antibiotic, antimicrobial approaches in IE, with special focus on anti-thrombotic strategies and hyperbaric oxygen therapy targeting the biofilm formation of the infected heart valves caused by Staphylococcus aureus. The format is translational from preclinical models to actual clinical treatment strategies.
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Affiliation(s)
- Christian Johann Lerche
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Franziska Schwartz
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Marie Theut
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Emil Loldrup Fosbøl
- Department of Cardiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Kasper Iversen
- Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, Herlev, Denmark.,Department of Emergency Medicine, Herlev and Gentofte Hospital, University of Copenhagen, Herlev, Denmark
| | - Henning Bundgaard
- Department of Cardiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Niels Høiby
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.,Costerton Biofilm Center, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Claus Moser
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
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Tandon I, Quinn KP, Balachandran K. Label-Free Multiphoton Microscopy for the Detection and Monitoring of Calcific Aortic Valve Disease. Front Cardiovasc Med 2021; 8:688513. [PMID: 34179147 PMCID: PMC8226007 DOI: 10.3389/fcvm.2021.688513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/17/2021] [Indexed: 12/12/2022] Open
Abstract
Calcific aortic valve disease (CAVD) is the most common valvular heart disease. CAVD results in a considerable socio-economic burden, especially considering the aging population in Europe and North America. The only treatment standard is surgical valve replacement as early diagnostic, mitigation, and drug strategies remain underdeveloped. Novel diagnostic techniques and biomarkers for early detection and monitoring of CAVD progression are thus a pressing need. Additionally, non-destructive tools are required for longitudinal in vitro and in vivo assessment of CAVD initiation and progression that can be translated into clinical practice in the future. Multiphoton microscopy (MPM) facilitates label-free and non-destructive imaging to obtain quantitative, optical biomarkers that have been shown to correlate with key events during CAVD progression. MPM can also be used to obtain spatiotemporal readouts of metabolic changes that occur in the cells. While cellular metabolism has been extensively explored for various cardiovascular disorders like atherosclerosis, hypertension, and heart failure, and has shown potential in elucidating key pathophysiological processes in heart valve diseases, it has yet to gain traction in the study of CAVD. Furthermore, MPM also provides structural, functional, and metabolic readouts that have the potential to correlate with key pathophysiological events in CAVD progression. This review outlines the applicability of MPM and its derived quantitative metrics for the detection and monitoring of early CAVD progression. The review will further focus on the MPM-detectable metabolic biomarkers that correlate with key biological events during valve pathogenesis and their potential role in assessing CAVD pathophysiology.
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Affiliation(s)
- Ishita Tandon
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR, United States
| | - Kyle P Quinn
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR, United States
| | - Kartik Balachandran
- Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR, United States
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8
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Katsi V, Magkas N, Antonopoulos A, Trantalis G, Toutouzas K, Tousoulis D. Aortic valve: anatomy and structure and the role of vasculature in the degenerative process. Acta Cardiol 2021; 76:335-348. [PMID: 32602774 DOI: 10.1080/00015385.2020.1746053] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Aortic valve stenosis is a degenerative disease affecting increasing number of individuals and characterised by thickening, calcification and fibrosis of the valve resulting in restricted valve motion. Degeneration of the aortic valve is no longer considered a passive deposition of calcium, but an active process that involves certain mechanisms, that is endothelial dysfunction, inflammation, increased oxidative stress, calcification, bone formation, lipid deposition, extracellular matrix (ECM) remodelling and neoangiogenesis. Accumulating evidence indicates an important role for neoangiogenesis (i.e. formation of new vessels) in the pathogenesis of aortic valve stenosis. The normal aortic valve is generally an avascular tissue supplied with oxygen and nutrients via diffusion from the circulating blood. In contrast, presence of intrinsic micro-vasculature has been demonstrated in stenotic and calcified valves. Importantly, presence and density of neovessels have been associated with inflammation, calcification and bone formation. It remains unclear whether neoangiogenesis is a compensatory mechanism aiming to counteract hypoxia and increased metabolic demands of the thickened tissue or represents an active contributor to disease progression. Data extracted mainly from animal studies are supportive of a direct detrimental effect of neoangiogenesis, however, robust evidence from human studies is lacking. Thus, there is inadequate knowledge to assess whether neoangiogenesis could serve as a future therapeutic target for a disease that no effective medical therapy exists. In this review, we present basic aspects of anatomy and structure of the normal and stenotic aortic valve and we focus on the role of valve vasculature in the natural course of valve calcification and stenosis.
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Affiliation(s)
- Vasiliki Katsi
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
| | - Nikolaos Magkas
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
| | - Alexios Antonopoulos
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
| | - Georgios Trantalis
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
| | - Konstantinos Toutouzas
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
| | - Dimitrios Tousoulis
- First Department of Cardiology, ‘Hippokration’ Hospital, Medical School, University of Athens, Athens, Greece
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9
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Niazy N, Barth M, Selig JI, Feichtner S, Shakiba B, Candan A, Albert A, Preuß K, Lichtenberg A, Akhyari P. Degeneration of Aortic Valves in a Bioreactor System with Pulsatile Flow. Biomedicines 2021; 9:biomedicines9050462. [PMID: 33922670 PMCID: PMC8145810 DOI: 10.3390/biomedicines9050462] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/18/2021] [Accepted: 04/21/2021] [Indexed: 02/07/2023] Open
Abstract
Calcific aortic valve disease is the most common valvular heart disease in industrialized countries. Pulsatile pressure, sheer and bending stress promote initiation and progression of aortic valve degeneration. The aim of this work is to establish an ex vivo model to study the therein involved processes. Ovine aortic roots bearing aortic valve leaflets were cultivated in an elaborated bioreactor system with pulsatile flow, physiological temperature, and controlled pressure and pH values. Standard and pro-degenerative treatment were studied regarding the impact on morphology, calcification, and gene expression. In particular, differentiation, matrix remodeling, and degeneration were also compared to a static cultivation model. Bioreactor cultivation led to shrinking and thickening of the valve leaflets compared to native leaflets while gross morphology and the presence of valvular interstitial cells were preserved. Degenerative conditions induced considerable leaflet calcification. In comparison to static cultivation, collagen gene expression was stable under bioreactor cultivation, whereas expression of hypoxia-related markers was increased. Osteopontin gene expression was differentially altered compared to protein expression, indicating an enhanced protein turnover. The present ex vivo model is an adequate and effective system to analyze aortic valve degeneration under controlled physiological conditions without the need of additional growth factors.
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Affiliation(s)
- Naima Niazy
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Mareike Barth
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Jessica I. Selig
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Sabine Feichtner
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Babak Shakiba
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Asya Candan
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
| | - Alexander Albert
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
- Department of Cardiovascular Surgery, Klinikum Dortmund gGmbH, Beurhausstraße 40, 44137 Dortmund, Germany
| | - Karlheinz Preuß
- Faculty of Biotechnology, Bioprocessing, Modulation and Simulation, University of Applied Sciences Mannheim, Paul-Wittsack-Straße 10, 68163 Mannheim, Germany;
| | - Artur Lichtenberg
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
- Correspondence:
| | - Payam Akhyari
- Department of Cardiac Surgery, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany; (N.N.); (M.B.); (J.I.S.); (S.F.); (B.S.); (A.C.); (A.A.); (P.A.)
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10
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Chester AH, Grande-Allen KJ. Which Biological Properties of Heart Valves Are Relevant to Tissue Engineering? Front Cardiovasc Med 2020; 7:63. [PMID: 32373630 PMCID: PMC7186395 DOI: 10.3389/fcvm.2020.00063] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 03/27/2020] [Indexed: 12/30/2022] Open
Abstract
Over the last 20 years, the designs of tissue engineered heart valves have evolved considerably. An initial focus on replicating the mechanical and structural features of semilunar valves has expanded to endeavors to mimic the biological behavior of heart valve cells as well. Studies on the biology of heart valves have shown that the function and durability of native valves is underpinned by complex interactions between the valve cells, the extracellular matrix, and the mechanical environment in which heart valves function. The ability of valve interstitial cells to synthesize extracellular matrix proteins and remodeling enzymes and the protective mediators released by endothelial cells are key factors in the homeostasis of valve function. The extracellular matrix provides the mechanical strength and flexibility required for the valve to function, as well as communicating with the cells that are bound within. There are a number of regulatory mechanisms that influence valve function, which include neuronal mechanisms and the tight regulation of growth and angiogenic factors. Together, studies into valve biology have provided a blueprint for what a tissue engineered valve would need to be capable of, in order to truly match the function of the native valve. This review addresses the biological functions of heart valve cells, in addition to the influence of the cells' environment on this behavior and examines how well these functions are addressed within the current strategies for tissue engineering heart valves in vitro, in vivo, and in situ.
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Affiliation(s)
- Adrian H Chester
- Heart Science Centre, The Magdi Yacoub Institute, Harefield, United Kingdom
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Zhu S, Qiu H, Bennett S, Kuek V, Rosen V, Xu H, Xu J. Chondromodulin-1 in health, osteoarthritis, cancer, and heart disease. Cell Mol Life Sci 2019; 76:4493-4502. [PMID: 31317206 PMCID: PMC6841647 DOI: 10.1007/s00018-019-03225-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 07/03/2019] [Accepted: 07/09/2019] [Indexed: 12/21/2022]
Abstract
The human chondromodulin-1 (Chm-1, Chm-I, CNMD, or Lect1) gene encodes a 334 amino acid type II transmembrane glycoprotein protein with characteristics of a furin cleavage site and a putative glycosylation site. Chm-1 is expressed most predominantly in healthy and developing avascular cartilage, and healthy cardiac valves. Chm-1 plays a vital role during endochondral ossification by the regulation of angiogenesis. The anti-angiogenic and chondrogenic properties of Chm-1 are attributed to its role in tissue development, homeostasis, repair and regeneration, and disease prevention. Chm-1 promotes chondrocyte differentiation, and is regulated by versatile transcription factors, such as Sox9, Sp3, YY1, p300, Pax1, and Nkx3.2. Decreased expression of Chm-1 is implicated in the onset and progression of osteoarthritis and infective endocarditis. Chm-1 appears to attenuate osteoarthritis progression by inhibiting catabolic activity, and to mediate anti-inflammatory effects. In this review, we present the molecular structure and expression profiling of Chm-1. In addition, we bring a summary to the potential role of Chm-1 in cartilage development and homeostasis, osteoarthritis onset and progression, and to the pathogenic role of Chm-1 in infective endocarditis and cancers. To date, knowledge of the Chm-1 receptor, cellular signalling, and the molecular mechanisms of Chm-1 is rudimentary. Advancing our understanding the role of Chm-1 and its mechanisms of action will pave the way for the development of Chm-1 as a therapeutic target for the treatment of diseases, such as osteoarthritis, infective endocarditis, and cancer, and for potential tissue regenerative bioengineering applications.
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Affiliation(s)
- Sipin Zhu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, China
- Molecular Laboratory and the Division of Regenerative Biology, School of Biomedical Sciences, M Block, QEII Medical Centre, The University of Western Australia (M504), 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Heng Qiu
- Molecular Laboratory and the Division of Regenerative Biology, School of Biomedical Sciences, M Block, QEII Medical Centre, The University of Western Australia (M504), 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Samuel Bennett
- Molecular Laboratory and the Division of Regenerative Biology, School of Biomedical Sciences, M Block, QEII Medical Centre, The University of Western Australia (M504), 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Vincent Kuek
- Molecular Laboratory and the Division of Regenerative Biology, School of Biomedical Sciences, M Block, QEII Medical Centre, The University of Western Australia (M504), 35 Stirling Hwy, Perth, WA, 6009, Australia
| | - Vicki Rosen
- Developmental Biology, Harvard School of Dental Medicine, Boston, MA, 02115, USA
| | - Huazi Xu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, China
| | - Jiake Xu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, China.
- Molecular Laboratory and the Division of Regenerative Biology, School of Biomedical Sciences, M Block, QEII Medical Centre, The University of Western Australia (M504), 35 Stirling Hwy, Perth, WA, 6009, Australia.
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Swaminathan G, Krishnamurthy VK, Sridhar S, Robson DC, Ning Y, Grande-Allen KJ. Hypoxia Stimulates Synthesis of Neutrophil Gelatinase-Associated Lipocalin in Aortic Valve Disease. Front Cardiovasc Med 2019; 6:156. [PMID: 31737648 PMCID: PMC6828964 DOI: 10.3389/fcvm.2019.00156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/14/2019] [Indexed: 12/15/2022] Open
Abstract
Objective: Aortic valve disease is commonly found in the elderly population. It is characterized by dysregulated extracellular matrix remodeling followed by extensive microcalcification of the aortic valve and activation of valve interstitial cells. The mechanism behind these events are largely unknown. Studies have reported expression of hypoxia inducible factor-1 alpha (HIF1α) in calcific nodules in aortic valve disease, therefore we investigated the effect of hypoxia on extracellular matrix remodeling in aged aortic valves. Approach and Results: Western blotting revealed elevated expression of HIF1α and the complex of matrix metalloprotease 9 (MMP9) and neutrophil gelatinase-associated lipocalin (NGAL) in aged porcine aortic valves cultured under hypoxic conditions. Consistently, immunofluorescence staining showed co-expression of MMP9 and NGAL in the fibrosa layer of these porcine hypoxic aortic valves. Gelatinase zymography demonstrated that the activity of MMP9-NGAL complex was significantly increased in aortic valves in 13% O2 compared to 20% O2. Importantly, the presence of ectopic elastic fibers in the fibrosa of hypoxic aortic valves, also detected in human diseased aortic valves, suggests altered elastin homeostasis due to hypoxia. Conclusion: This study demonstrates that hypoxia stimulates pathological extracellular matrix remodeling via expression of NGAL and MMP9 by valve interstitial cells.
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Maeda K, Ma X, Hanley FL, Riemer RK. Modeling Impaired Coaptation Effects on Mitral Leaflet Homeostasis Using a Flow-Culture Bioreactor. Ann Thorac Surg 2018; 107:512-518. [PMID: 30365966 DOI: 10.1016/j.athoracsur.2018.08.084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 08/02/2018] [Accepted: 08/31/2018] [Indexed: 10/28/2022]
Abstract
BACKGROUND Mitral valve (MV) regurgitation constitutes an increasing burden of adult and pediatric cardiac disease tending to worsen over time. Whether altered mechanical forces on leaflets cause valve disease is unknown. Here we show that MV leaflet coaptive strain disruption alters expression of genes critical to leaflet homeostasis. METHODS We used a flow-culture bioreactor of rat MVs with flow-induced cyclic coaptation (cycling valve group; n = 4) or in a sustained open state (open valve group; n = 4). After 3 days of culture, leaflet RNA expression was profiled. RESULTS More than 48 genes exhibited markedly changed expression when coaptive leaflet strain was disrupted for 3 days (change >fourfold; p < 0.05; cycling vs open valves). Genes exhibiting highly altered expression included Angpt2, Vegf, Cd74, RT1-Da (HLA-DRA), and Igfbp3. Pathway analysis indicated the most significant signaling pathways regulating the expression changes were Hif1α and Tnfα when MV closure was disrupted. CONCLUSIONS Disruption of normal MV coaptive strain markedly alters the expression of leaflet genes, demonstrating that cyclic strain is critically important to leaflet homeostasis. We demonstrate a pattern of MV gene expression changes in which hypoxia signaling is prominently increased in response to disrupted strain cycles. Coaptive strain regulation of MV leaflet homeostasis implicates altered strain as a mechanism potentially initiating valve disease. Early repair may prevent progression of disease driven by altered coaptation.
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Affiliation(s)
- Katsuhide Maeda
- Pediatric Cardiac Surgery Division, Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California
| | - Xiaoyuan Ma
- Pediatric Cardiac Surgery Division, Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California
| | - Frank L Hanley
- Pediatric Cardiac Surgery Division, Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California
| | - R Kirk Riemer
- Pediatric Cardiac Surgery Division, Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California.
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Amofa D, Hulin A, Nakada Y, Sadek HA, Yutzey KE. Hypoxia promotes primitive glycosaminoglycan-rich extracellular matrix composition in developing heart valves. Am J Physiol Heart Circ Physiol 2017; 313:H1143-H1154. [PMID: 28842437 PMCID: PMC5814654 DOI: 10.1152/ajpheart.00209.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 08/16/2017] [Accepted: 08/17/2017] [Indexed: 12/21/2022]
Abstract
During postnatal heart valve development, glycosaminoglycan (GAG)-rich valve primordia transform into stratified valve leaflets composed of GAGs, fibrillar collagen, and elastin layers accompanied by decreased cell proliferation as well as thinning and elongation. The neonatal period is characterized by the transition from a uterine environment to atmospheric O2, but the role of changing O2 levels in valve extracellular matrix (ECM) composition or morphogenesis is not well characterized. Here, we show that tissue hypoxia decreases in mouse aortic valves in the days after birth, concomitant with ECM remodeling and cell cycle arrest of valve interstitial cells. The effects of hypoxia on late embryonic valve ECM composition, Sox9 expression, and cell proliferation were examined in chicken embryo aortic valve organ cultures. Maintenance of late embryonic chicken aortic valve organ cultures in a hypoxic environment promotes GAG expression, Sox9 nuclear localization, and indicators of hyaluronan remodeling but does not affect fibrillar collagen content or cell proliferation. Chronic hypoxia also promotes GAG accumulation in murine adult heart valves in vivo. Together, these results support a role for hypoxia in maintaining a primitive GAG-rich matrix in developing heart valves before birth and also in the induction of hyaluronan remodeling in adults.NEW & NOTEWORTHY Tissue hypoxia decreases in mouse aortic valves after birth, and exposure to hypoxia promotes glycosaminoglycan accumulation in cultured chicken embryo valves and adult murine heart valves. Thus, hypoxia maintains a primitive extracellular matrix during heart valve development and promotes extracellular matrix remodeling in adult mice, as occurs in myxomatous disease.
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Affiliation(s)
- Dorothy Amofa
- Division of Molecular Cardiovascular Biology, Heart Institute, Cincinnati Children's Medical Center, Cincinnati Ohio; and
| | - Alexia Hulin
- Division of Molecular Cardiovascular Biology, Heart Institute, Cincinnati Children's Medical Center, Cincinnati Ohio; and
| | - Yuji Nakada
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Hesham A Sadek
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Katherine E Yutzey
- Division of Molecular Cardiovascular Biology, Heart Institute, Cincinnati Children's Medical Center, Cincinnati Ohio; and
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Krishnamurthy VK, Stout AJ, Sapp MC, Matuska B, Lauer ME, Grande-Allen KJ. Dysregulation of hyaluronan homeostasis during aortic valve disease. Matrix Biol 2017; 62:40-57. [PMID: 27856308 PMCID: PMC10615645 DOI: 10.1016/j.matbio.2016.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 11/05/2016] [Accepted: 11/08/2016] [Indexed: 01/03/2023]
Abstract
Aortic valve disease (AVD) is one of the leading causes of cardiovascular mortality. Abnormal expression of hyaluronan (HA) and its synthesizing/degrading enzymes have been observed during latent AVD however, the mechanism of impaired HA homeostasis prior to and after the onset of AVD remains unexplored. Transforming growth factor beta (TGFβ) pathway defects and biomechanical dysfunction are hallmarks of AVD, however their association with altered HA regulation is understudied. Expression of HA homeostatic markers was evaluated in diseased human aortic valves and TGFβ1-cultured porcine aortic valve tissues using histology, immunohistochemistry and Western blotting. Further, porcine valve interstitial cell cultures were stretched (using Flexcell) and simultaneously treated with exogenous TGFβ1±inhibitors for activated Smad2/3 (SB431542) and ERK1/2 (U0126) pathways, and differential HA regulation was assessed using qRT-PCR. Pathological heavy chain HA together with abnormal regional expression of the enzymes HAS2, HYAL1, KIAA1199, TSG6 and IαI was demonstrated in calcified valve tissues identifying the collapse of HA homeostatic machinery during human AVD. Heightened TSG6 activity likely preceded the end-stage of disease, with the existence of a transitional, pre-calcific phase characterized by HA dysregulation. TGFβ1 elicited a fibrotic remodeling response in porcine aortic valves similar to human disease pathology, with increased collagen and HYAL to HAS ratio, and site-specific abnormalities in the expression of CD44 and RHAMM receptors. Further in these porcine valves, expression of HAS2 and HYAL1 was found to be differentially regulated by the Smad2/3 and ERK1/2 pathways, and CD44 expression was highly responsive to biomechanical strain. Leveraging the regulatory pathways that control both HA maintenance in normal valves and early postnatal dysregulation of HA homeostasis during disease may identify new mechanistic insight into AVD pathogenesis.
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Affiliation(s)
| | - Andrew J Stout
- Department of Materials Science and Nanoengineering, Rice University, Houston, TX 77005, USA
| | - Matthew C Sapp
- Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Brittany Matuska
- Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Mark E Lauer
- Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA
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Salhiyyah K, Sarathchandra P, Latif N, Yacoub MH, Chester AH. Hypoxia-mediated regulation of the secretory properties of mitral valve interstitial cells. Am J Physiol Heart Circ Physiol 2017; 313:H14-H23. [PMID: 28314761 DOI: 10.1152/ajpheart.00720.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 03/14/2017] [Accepted: 03/14/2017] [Indexed: 11/22/2022]
Abstract
The sophisticated function of the mitral valve depends to a large extent on its extracellular matrix (ECM) and specific cellular components. These are tightly regulated by a repertoire of mechanical stimuli and biological pathways. One potentially important stimulus is hypoxia. The purpose of this investigation is to determine the effect of hypoxia on the regulation of mitral valve interstitial cells (MVICs) with respect to the synthesis and secretion of extracellular matrix proteins. Hypoxia resulted in reduced production of total collagen and sulfated glycosaminoglycans (sGAG) in cultured porcine MVICs. Increased gene expression of matrix metalloproteinases-1 and -9 and their tissue inhibitors 1 and 2 was also observed after incubation under hypoxic conditions for up to 24 h. Hypoxia had no effect on MVIC viability, morphology, or phenotype. MVICs expressed hypoxia-inducible factor (HIF)-1α under hypoxia. Stimulating HIF-1α chemically caused a reduction in the amount of sGAG produced, similar to the effect observed under hypoxia. Human rheumatic valves had greater expression of HIF-1α compared with normal or myxomatous degenerated valves. In conclusion, hypoxia affects the production of certain ECM proteins and expression of matrix remodeling enzymes by MVICs. The effects of hypoxia appear to correlate with the induction of HIF-1α. This study highlights a potential role of hypoxia and HIF-1α in regulating the mitral valve, which could be important in health and disease.NEW & NOTEWORTHY This study demonstrates that hypoxia regulates extracellular matrix secretion and the remodeling potential of heart valve interstitial cells. Expression of hypoxia-induced factor-1α plays a role in these effects. These data highlight the potential role of hypoxia as a physiological mediator of the complex function of heart valve cells.
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Affiliation(s)
- Kareem Salhiyyah
- National Heart & Lung Institute, Imperial College London, Heart Science Centre, Harefield, Middlesex, United Kingdom
| | - Padmini Sarathchandra
- National Heart & Lung Institute, Imperial College London, Heart Science Centre, Harefield, Middlesex, United Kingdom
| | - Najma Latif
- National Heart & Lung Institute, Imperial College London, Heart Science Centre, Harefield, Middlesex, United Kingdom
| | - Magdi H Yacoub
- National Heart & Lung Institute, Imperial College London, Heart Science Centre, Harefield, Middlesex, United Kingdom
| | - Adrian H Chester
- National Heart & Lung Institute, Imperial College London, Heart Science Centre, Harefield, Middlesex, United Kingdom
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