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Piola M, Prandi F, Fiore GB, Agrifoglio M, Polvani G, Pesce M, Soncini M. Human Saphenous Vein Response to Trans-wall Oxygen Gradients in a Novel Ex Vivo Conditioning Platform. Ann Biomed Eng 2015; 44:1449-61. [PMID: 26319011 DOI: 10.1007/s10439-015-1434-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 08/18/2015] [Indexed: 11/30/2022]
Abstract
Autologous saphenous veins are commonly used for the coronary artery bypass grafting even if they are liable to progressive patency reduction, known as 'vein graft disease'. Although several cellular and molecular causes for vein graft disease have been identified using in vivo models, the metabolic cues induced by sudden interruption of vasa vasorum blood supply have remained unexplored. In the present manuscript, we describe the design of an ex vivo culture system allowing the generation of an oxygen gradient between the luminal and the adventitial sides of the vein. This system featured a separation between the inner and the outer vessel culture circuits, and integrated a purpose-developed de-oxygenator module enabling the trans-wall oxygen distribution (high oxygen level at luminal side and low oxygen level at the adventitial side) existing in arterialized veins. Compared with standard cultures the bypass-specific conditions determined a significant increase in the proliferation of cells around adventitial vasa vasorum and an elevation in the length density of small and large caliber vasa vasorum. These results suggest, for the first time, a cause-effect relationship between the vein adventitial hypoxia and a neo-vascularization process, a factor known to predispose the arterialized vein conduits to restenosis.
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Affiliation(s)
- Marco Piola
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133, Milan, Italy.
| | - Francesca Prandi
- Unità di Ingegneria Tissutale, Centro Cardiologico Monzino-IRCCS, Via Parea 4, 20138, Milan, Italy
| | - Gianfranco Beniamino Fiore
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133, Milan, Italy
| | - Marco Agrifoglio
- Dipartimento di Scienze Cliniche e di Comunità, Università di Milano, Via Parea 4, 20138, Milan, Italy
| | - Gianluca Polvani
- Dipartimento di Scienze Cliniche e di Comunità, Università di Milano, Via Parea 4, 20138, Milan, Italy
| | - Maurizio Pesce
- Unità di Ingegneria Tissutale, Centro Cardiologico Monzino-IRCCS, Via Parea 4, 20138, Milan, Italy
| | - Monica Soncini
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, P.zza Leonardo da Vinci 32, 20133, Milan, Italy
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The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins. Biomaterials 2014; 35:2588-99. [DOI: 10.1016/j.biomaterials.2013.12.041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/18/2013] [Indexed: 01/14/2023]
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Berard X, Déglise S, Alonso F, Saucy F, Meda P, Bordenave L, Corpataux JM, Haefliger JA. Role of hemodynamic forces in the ex vivo arterialization of human saphenous veins. J Vasc Surg 2013; 57:1371-82. [PMID: 23351647 DOI: 10.1016/j.jvs.2012.09.041] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/31/2012] [Accepted: 09/10/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Human saphenous vein grafts are one of the salvage bypass conduits when endovascular procedures are not feasible or fail. Understanding the remodeling process that venous grafts undergo during exposure to arterial conditions is crucial to improve their patency, which is often compromised by intimal hyperplasia. The precise role of hemodynamic forces such as shear stress and arterial pressure in this remodeling is not fully characterized. The aim of this study was to determine the involvement of arterial shear stress and pressure on vein wall remodeling and to unravel the underlying molecular mechanisms. METHODS An ex vivo vein support system was modified for chronic (up to 1 week), pulsatile perfusion of human saphenous veins under controlled conditions that permitted the separate control of arterial shear stress and different arterial pressure (7 mm Hg or 70 mm Hg). RESULTS Veins perfused for 7 days under high pressure (70 mm Hg) underwent significant development of a neointima compared with veins exposed to low pressure (7 mm Hg). These structural changes were associated with altered expression of several molecular markers. Exposure to an arterial shear stress under low pressure increased the expression of matrix metalloproteinase (MMP)-2 and MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 at the transcript, protein, and activity levels. This increase was enhanced by high pressure, which also increased TIMP-2 protein expression despite decreased levels of the cognate transcript. In contrast, the expression of plasminogen activator inhibitor-1 increased with shear stress but was not modified by pressure. Levels of the venous marker Eph-B4 were decreased under arterial shear stress, and levels of the arterial marker Ephrin-B2 were downregulated under high-pressure conditions. CONCLUSIONS This model is a valuable tool to identify the role of hemodynamic forces and to decipher the molecular mechanisms leading to failure of human saphenous vein grafts. Under ex vivo conditions, arterial perfusion is sufficient to activate the remodeling of human veins, a change that is associated with the loss of specific vein markers. Elevation of pressure generates intimal hyperplasia, even though veins do not acquire arterial markers. CLINICAL RELEVANCE The pathological remodeling of the venous wall, which leads to stenosis and ultimately graft failure, is the main limiting factor of human saphenous vein graft bypass. This remodeling is due to the hemodynamic adaptation of the vein to the arterial environment and cannot be prevented by conventional therapy. To develop a more targeted therapy, a better understanding of the molecular mechanisms involved in intimal hyperplasia is essential, which requires the development of ex vivo models of chronic perfusion of human veins.
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Affiliation(s)
- Xavier Berard
- Department of Vascular Surgery, Pellegrin Hospital, University of Bordeaux, Bordeaux, France
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Dummler S, Eichhorn S, Tesche C, Schreiber U, Voss B, Deutsch MA, Hauner H, Lahm H, Lange R, Krane M. Pulsatile ex vivo perfusion of human saphenous vein grafts under controlled pressure conditions increases MMP-2 expression. Biomed Eng Online 2011; 10:62. [PMID: 21777461 PMCID: PMC3148203 DOI: 10.1186/1475-925x-10-62] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 07/21/2011] [Indexed: 11/16/2022] Open
Abstract
Background The use of human saphenous vein grafts (HSVGs) as a bypass conduit is a standard procedure in the treatment of coronary artery disease while their early occlusion remains a major problem. Methods We have developed an ex vivo perfusion system, which uses standardized and strictly controlled hemodynamic parameters for the pulsatile and non-static perfusion of HSVGs to guarantee a reliable analysis of molecular parameters under different pressure conditions. Cell viability of HSVGs (n = 12) was determined by the metabolic conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) into a purple formazan dye. Results Under physiological flow rates (10 mmHg) HSVGs remained viable for two weeks. Their exposure to arterial conditions (100 mmHg) was possible for one week without important reduction in viability. Baseline expression of matrix metalloproteinase-2 (MMP-2) after venous perfusion (2.2 ± 0.5, n = 5) was strongly up-regulated after exposure to arterial conditions for three days (19.8 ± 4.3) or five days (23.9 ± 6.1, p < 0.05). Zymographic analyses confirmed this increase on the protein level. Our results suggest that expression and activity of MMP-2 are strongly increased after exposure of HSVGs to arterial hemodynamic conditions compared to physiological conditions. Conclusion Therefore, our system might be helpful to more precisely understand the molecular mechanisms leading to an early failure of HSVGs.
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Affiliation(s)
- Sara Dummler
- German Heart Center Munich at the Technische Universität München, Department of Cardiovascular Surgery, Lazarettstrasse 36, D-80636 Munich, Germany.
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El-Kurdi MS, Vipperman JS, Vorp DA. Design and Subspace System Identification of an Ex Vivo Vascular Perfusion System. J Biomech Eng 2009; 131:041012. [DOI: 10.1115/1.3072895] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Numerical algorithms for subspace system identification (N4SID) are a powerful tool for generating the state space (SS) representation of any system. The purpose of this work was to use N4SID to generate SS models of the flowrate and pressure generation within an ex vivo vascular perfusion system (EVPS). Accurate SS models were generated and converted to transfer functions (TFs) to be used for proportional integral and derivative (PID) controller design. By prescribing the pressure and flowrate inputs to the pumping components within the EVPS and measuring the resulting pressure and flowrate in the system,_four TFs were estimated;_two for a flowrate controller (HRP,f and HRPP,f) and two for a pressure controller (HRP,p and HRPP,p). In each controller,_one TF represents a roller pump (HRP,f and HRP,p),_and the other represents a roller pump and piston in series (HRPP,f and HRPP,p). Experiments to generate the four TFs were repeated five times (N=5) from which average TFs were calculated. The average model fits, computed as the percentage of the output variation (to_the_prescribed_inputs) reproduced by the model, were 94.93±1.05% for HRP,p, 81.29±0.20% for HRPP,p, 94.45±0.73% for HRP,f, and 77.12±0.36% for HRPP,f. The simulated step, impulse, and frequency responses indicate that the EVPS is a stable system and can respond to signals containing power of up to 70_Hz.
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Affiliation(s)
- Mohammed S. El-Kurdi
- Department of Surgery, Division of Vascular Surgery, University of Pittsburgh, Suite 200, Bridgeside Point, Pittsburgh, PA 15219; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219; McGowan Institute for Regenerative Medicine, University of Pittsburgh, 100 Technology Drive, Pittsburgh, PA 15219
| | - Jeffrey S. Vipperman
- Department of Mechanical Engineering and Material Science, and Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219
| | - David A. Vorp
- Department of Surgery, Division of Vascular Surgery, University of Pittsburgh, Suite 200, Bridgeside Point, Pittsburgh, PA 15219; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219; McGowan Institute for Regenerative Medicine, University of Pittsburgh, 100 Technology Drive, Pittsburgh, PA 15219
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Déglise S, Martin D, Probst H, Saucy F, Hayoz D, Waeber G, Nicod P, Ris HB, Corpataux JM, Haefliger JA. Increased connexin43 expression in human saphenous veins in culture is associated with intimal hyperplasia. J Vasc Surg 2005; 41:1043-52. [PMID: 15944608 DOI: 10.1016/j.jvs.2005.02.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVE Intimal hyperplasia is a vascular remodelling process that occurs after a vascular injury. The mechanisms involved in intimal hyperplasia are proliferation, dedifferentiation, and migration of medial smooth muscle cells towards the subintimal space. We postulated that gap junctions, which coordinate physiologic processes such as cell growth and differentiation, might participate in the development of intimal hyperplasia. Connexin43 (Cx43) expression levels may be altered in intimal hyperplasia, and we therefore evaluated the regulated expression of Cx43 in human saphenous veins in culture in the presence or not of fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity. METHODS Segments of harvested human saphenous veins, obtained at the time of bypass graft, were opened longitudinally with the luminal surface uppermost and maintained in culture for 14 days. Vein fragments were then processed for histologic examination, neointimal thickness measurements, immunocytochemistry, RNA, and proteins analysis. RESULTS Of the four connexins (Cx37, 40, 43, and 45), we focused on Cx43 and Cx40, which we found by real-time polymerase chain reaction to be expressed in the saphenous vein because they are the predominant connexins expressed by smooth muscle cells and endothelial cells. After 14 days of culture, histomorphometric analysis showed a significant increase in the intimal thickness as observed during the process of intimal hyperplasia. A time-course analysis revealed a progressive upregulation of Cx43 to reach a maximal increase of sixfold to eightfold at both transcript and protein levels after 14 days in culture. In contrast, the expression of Cx40, abundantly expressed in the endothelial cells, was not altered. Immunofluorescence showed a large increase in Cx43 within smooth muscle cell membranes of the media layer. The development of intimal hyperplasia in vitro was decreased in presence of fluvastatin and was associated with reduced Cx43 expression. CONCLUSIONS These data show that Cx43 is increased in vitro during the process of intimal hyperplasia and that fluvastatin could prevent this induction, supporting a critical role for Cx43-mediated gap-junctional communication in the human vein during the development of intimal hyperplasia. CLINICAL RELEVANCE Stenosis due to intimal hyperplasia is the most common cause of failure of venous bypass grafts. To better understand the development of intimal hyperplasia, we used an ex vivo organ culture model to study saphenous veins harvested from patients undergoing a lower limb bypass surgery. In this model, the morphologic and functional integrity of the vessel wall is maintained and significant intimal hyperplasia development occurs after 14 days in culture. We have postulated that gap junctions, which coordinate physiologic processes such as cell growth and differentiation, may participate in the development of intimal hyperplasia. Indeed, intimal hyperplasia consists of proliferation and migration of smooth muscle cells into the subendothelial space. Intercellular communication is responsible for the direct transfer of ions and small molecules from one cell to the other through gap-junction channels found at cell-cell appositions. No study to date has evaluated whether gap junctional communication is involved in the process of intimal hyperplasia in humans. This assertion was investigated by using the aforementioned organ culture model of intimal hyperplasia in human saphenous veins, and our data support a critical role for Cx43-mediated gap junctional communication in human vein during the development of intimal hyperplasia.
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Affiliation(s)
- Sébastien Déglise
- Department of Thoracic and Vascular Surgery, University Hospital, Lausanne, Switzerland
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Rey J, Probst H, Mazzolai L, Bosman FTB, Pusztaszeri M, Stergiopulos N, Ris HB, Hayoz D, Saucy F, Corpataux JM. Comparative assessment of intimal hyperplasia development after 14 days in two different experimental settings: tissue culture versus ex vivo continuous perfusion of human saphenous vein. J Surg Res 2004; 121:42-9. [PMID: 15313374 DOI: 10.1016/j.jss.2004.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Indexed: 11/23/2022]
Abstract
BACKGROUND Intimal hyperplasia (IH) is a vascular remodeling process which often leads to failure of arterial bypass or hemodialysis access. Experimental and clinical work have provided insight in IH development; however, further studies under precise controlled conditions are required to improve therapeutic strategies to inhibit IH development. Ex vivo perfusion of human vessel segments under standardized hemodynamic conditions may provide an adequate experimental approach for this purpose. Therefore, chronically perfused venous segments were studied and compared to traditional static culture procedures with regard to functional and histomorphologic characteristics as well as gene expression. MATERIALS AND METHODS Static vein culture allowing high tissue viability was performed as previously described. Ex vivo vein support system (EVVSS) was performed using a vein support system consisting of an incubator with a perfusion chamber and a pump. EVVSS allows vessel perfusion under continuous flow while maintaining controlled hemodynamic conditions. Each human saphenous vein was divided in two parts, one cultured in a Pyrex dish and the other part perfused in EVVSS for 14days. Testing of vasomotion, histomorphometry, expression of CD 31, Factor VIII, MIB 1, alpha-actin, and PAI-l were determined before and after 14days of either experimental conditions. RESULTS Human venous segments cultured under traditional or perfused conditions exhibited similar IH after 14 days as shown by histomorphometry. Smooth-muscle cell (SMC) was preserved after chronic perfusion. Although integrity of both endothelial and smooth-muscle cells appears to be maintained in both culture conditions as confirmed by CD31, factor VIII, and alpha-actin expression, a few smooth-muscle cells in the media stained positive for factor VIII. Cell-proliferation marker MIB-1 was also detected in the two settings and PAI-1 mRNA expression and activity increased significantly after 14 days of culture and perfusion. CONCLUSION This study demonstrates the feasibility to chronically perfuse human vessels under sterile conditions with preservation of cellular integrity and vascular contractility. To gain insights into the mechanisms leading to IH, it will now be possible to study vascular remodeling not only under static conditions but also in hemodynamic environment mimicking as closely as possible the flow conditions encountered in reconstructive vascular surgery.
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Affiliation(s)
- J Rey
- Division of Thoracic and Vascular Surgery, CHUV, Rue du Bugnon 46, 1011 Lausanne-CHUV, Switzerland
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