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Jin C, Zhao L, Wu Z, Li B, Liu R, He H, Wang L, Wang W. Comparison on the properties of bovine pericardium and porcine pericardium used as leaflet materials of transcatheter heart valve. Artif Organs 2021; 46:427-438. [PMID: 34545589 DOI: 10.1111/aor.14074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/06/2021] [Accepted: 09/13/2021] [Indexed: 12/12/2022]
Abstract
BACKGROUND In order to obtain the smaller delivery diameter, porcine pericardium had been used as a substitute material of bovine pericardium for the leaflet materials of transcatheter heart valve (THV). However, the differences between them had not been fully studied. Therefore, this study compared the microstructure, biochemical and mechanical properties of two materials and hydrodynamics of THV made by the two materials in detail. METHODS In this study, firstly, the microstructure of pericardium was analyzed by staining and scanning electron microscope; secondly, the biochemical properties of pericardium after different processes were compared by heat shrinkage temperature test, free amino and carboxyl concentration test, enzyme degradation test, subcutaneous implantation calcification analysis in rats; finally, the mechanical properties were evaluated by uniaxial tensile test before and after the pericardium being crimped, and then, the hydrodynamics of THV was studied according to the ISO5840 standard. RESULTS Compared with bovine pericardium, after the same process, porcine pericardium showed a looser and tinier fiber bundle, a similar free carboxyl concentration, a lower resistance to enzyme degradation, a significantly lower calcification, bearing capacity and damage after being crimped, a better hydrodynamic and adaption with lower cardiac output and deformation of implantation position. Meanwhile the dehydration process of pericardium almost had preserved all the biochemical advantages of two materials. CONCLUSION In this study, porcine and bovine pericardium showed some significant differences in biochemical, mechanical properties and hydrodynamics. According to the results, it was presumed that the thinner porcine pericardium might be more suitable for THV of right heart system. Meanwhile, more attention should be taken for the calcification of THV made by the bovine pericardium.
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Affiliation(s)
- Chang Jin
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
| | - Li Zhao
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
| | - Zebin Wu
- Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.,Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beihang University, Beijing, China
| | - Bin Li
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
| | - Ronghui Liu
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
| | - Hongping He
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
| | - Lizhen Wang
- Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.,Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beihang University, Beijing, China
| | - Weidong Wang
- Research Center for Biomedical Engineering, Medical Innovation & Research Division, Chinese PLA General Hospital, Beijing, China.,Key Laboratory of Biomedical Engineering and Translational Medicine, Ministry of Industry and Information Technology, Chinese PLA General Hospital, Beijing, China
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Xuan Y, Dvir D, Wang Z, Ye J, Guccione JM, Ge L, Tseng EE. Stent and leaflet stresses across generations of balloon-expandable transcatheter aortic valves. Interact Cardiovasc Thorac Surg 2020; 30:879-886. [PMID: 32248231 PMCID: PMC7248644 DOI: 10.1093/icvts/ivaa037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 01/10/2020] [Accepted: 02/04/2020] [Indexed: 12/23/2022] Open
Abstract
OBJECTIVES Transcatheter aortic valve replacement (TAVR) is established therapy for severe aortic stenosis patients with intermediate-, high- and prohibitive-risk for surgery. A significant challenge when expanding TAVR to low-risk and younger patients is the unknown long-term durability. High leaflet stresses have been associated with surgical bioprosthetic valve degeneration. In this study, we examined the impact of changes in valve design across 3 generations of same-sized TAVR devices on stent and leaflet stresses. METHODS The 26-mm Edwards SAPIEN, 23, 26 and 29 mm SAPIEN XT (XT) and 26 mm SAPIEN 3 (S3) (n = 1 each) underwent micro-computed tomography (micro-CT) scanning. Dynamic finite element computational simulations of 23-26 mm SAPIEN, 23-29 mm XT and 23-29 mm S3 were performed with physiological loading and micro-CT or scaled geometries. RESULTS Peak stresses were concentrated in the commissure area and along the bottom of the suture, representing areas most likely to develop structural valve degeneration across TAVR generations. Latest-generation S3 showed greatest 99th percentile principal stress on commissural leaflets for 26 and 29 mm, and increased stresses over XT for 23 mm. Percentage of higher stress areas within the leaflets steadily increased across generations, 3.8%, 3.9% and 5.7%, respectively, for 26 mm SAPIEN, XT and S3 with similar trend for 29-mm valves. CONCLUSIONS Using computational simulations based on high-fidelity modelling of balloon-expandable TAVRs, our study demonstrated that maximum stress areas existed in similar leaflet locations across SAPIEN generations, while the latest model S3 had the highest magnitude for both 26- and 29-mm valves. S3 also had the largest area of higher stresses than other generations, which would be prone to degeneration. Our study coupled with future long-term clinical outcomes >10 years will provide insight on biomechanics of TAVR degeneration.
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Affiliation(s)
- Yue Xuan
- Division of Cardiothoracic Surgery, University of California San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA
| | - Danny Dvir
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | - Zhongjie Wang
- Division of Cardiothoracic Surgery, University of California San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA
| | - Jian Ye
- Department of Surgery, St Paul’s Hospital, Vancouver, BC, Canada
| | - Julius M Guccione
- Division of Cardiothoracic Surgery, University of California San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA
| | - Liang Ge
- Division of Cardiothoracic Surgery, University of California San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA
| | - Elaine E Tseng
- Division of Cardiothoracic Surgery, University of California San Francisco and San Francisco VA Medical Center, San Francisco, CA, USA
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Xuan Y, Dvir D, Wang Z, Mizoguchi T, Ye J, Guccione JM, Ge L, Tseng EE. Stent and leaflet stresses in 26-mm, third-generation, balloon-expandable transcatheter aortic valve. J Thorac Cardiovasc Surg 2018; 157:528-536. [PMID: 30041923 DOI: 10.1016/j.jtcvs.2018.04.115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 04/12/2018] [Accepted: 04/23/2018] [Indexed: 10/14/2022]
Abstract
OBJECTIVES Transcatheter aortic valve replacement has proven successful in treating intermediate-risk, high-risk, and inoperable patients with severe aortic stenosis. Third-generation, balloon-expandable transcatheter aortic valves were developed with an outer sealing skirt to reduce paravalvular leakage. As transcatheter aortic valve replacement use expands, long-term durability questions remain. Valve design influences durability, where regions of increased leaflet stress are vulnerable to early degeneration. However, third-generation transcatheter aortic valve stresses are unknown. Our goals were to determine the stent and leaflet stresses of third-generation, balloon-expandable transcatheter aortic valves. METHODS The commercial 26-mm Edwards SAPIEN 3 valve (Edwards Lifesciences, Inc, Irvine, Calif) underwent high-resolution micro-computed tomography scanning to develop a precise 3-dimensional geometric mesh of the stent and valve. Leaflet material properties were obtained from surgical bioprostheses, and stent material properties were based on cobalt-chromium. Simulations of systemic pressure loading were performed, and stress was calculated using finite element analyses. RESULTS At diastole, maximum and minimum principal stresses on transcatheter aortic valve leaflets were 2.7 MPa and -0.47 MPa, respectively. Peak leaflet stresses were observed at upper leaflet commissures, at their connection to the stent. Maximum and minimum principal stresses for the stent were 38.2 MPa and -44.4 MPa, respectively, at 80 mm Hg and were located just below the commissural stent. CONCLUSIONS Stress analysis of the 26-mm SAPIEN 3 valve using exact geometry from high-resolution scans demonstrated that peak stresses for both transcatheter aortic valve stent and leaflets were present at commissural tips where leaflets were attached. These regions would be most likely to initiate degeneration. The Dacron skirt had minimal effect on stresses on leaflets and stent.
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Affiliation(s)
- Yue Xuan
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif
| | - Danny Dvir
- Division of Cardiology, University of Washington, Seattle, Wash
| | - Zhongjie Wang
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif
| | - Trek Mizoguchi
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif
| | - Jian Ye
- Division of Cardiovascular Surgery, St Paul's Hospital and Vancouver General Hospital, Vancouver, British Columbia, Canada
| | - Julius M Guccione
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif
| | - Liang Ge
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif
| | - Elaine E Tseng
- Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, Calif.
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Incidence, Timing, and Predictors of Valve Hemodynamic Deterioration After Transcatheter Aortic Valve Replacement: Multicenter Registry. J Am Coll Cardiol 2016; 67:644-655. [PMID: 26868689 DOI: 10.1016/j.jacc.2015.10.097] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 10/21/2015] [Indexed: 01/05/2023]
Abstract
BACKGROUND Scarce data exist on the incidence of and factors associated with valve hemodynamic deterioration (VHD) after transcatheter aortic valve replacement (TAVR). OBJECTIVES This study sought to determine the incidence, timing, and predictors of VHD in a large cohort of patients undergoing TAVR. METHODS This multicenter registry included 1,521 patients (48% male; 80 ± 7 years of age) who underwent TAVR. Mean echocardiographic follow-up was 20 ± 13 months (minimum: 6 months). Echocardiographic examinations were performed at discharge, at 6 to 12 months, and yearly thereafter. Annualized changes in mean gradient (mm Hg/year) were calculated by dividing the difference between the mean gradient at last follow-up and the gradient at discharge by the time between examinations. VHD was defined as a ≥10 mm Hg increase in transprosthetic mean gradient during follow-up compared with discharge assessment. RESULTS The overall mean annualized rate of transprosthetic gradient progression during follow-up was 0.30 ± 4.99 mm Hg/year. A total of 68 patients met criteria of VHD (incidence: 4.5% during follow-up). The absence of anticoagulation therapy at hospital discharge (p = 0.002), a valve-in-valve (TAVR in a surgical valve) procedure (p = 0.032), the use of a 23-mm valve (p = 0.016), and a greater body mass index (p = 0.001) were independent predictors of VHD. CONCLUSIONS There was a mild but significant increase in transvalvular gradients over time after TAVR. The lack of anticoagulation therapy, a valve-in-valve procedure, a greater body mass index, and the use of a 23-mm transcatheter valve were associated with higher rates of VHD post-TAVR. Further prospective studies are required to determine whether a specific antithrombotic therapy post-TAVR may reduce the risk of VHD.
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Simionescu DT, Chen J, Jaeggli M, Wang B, Liao J. Form Follows Function: Advances in Trilayered Structure Replication for Aortic Heart Valve Tissue Engineering. JOURNAL OF HEALTHCARE ENGINEERING 2012; 3:179-202. [PMID: 23355946 DOI: 10.1260/2040-2295.3.2.179] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Tissue engineering the aortic heart valve is a challenging endeavor because of the particular hemodynamic and biologic conditions present in the native aortic heart valve. The backbone of an ideal valve substitute should be a scaffold that is strong enough to withstand billions of repetitive bending, flexing and stretching cycles, while also being slowly degradable to allow for remodeling. In this review we highlight three overlooked aspects that might influence the long term durability of tissue engineered valves: replication of the native valve trilayered histoarchitecture, duplication of the three-dimensional shape of the valve and cell integration efforts focused on getting the right number and type of cells to the right place within the valve structure and driving them towards homeostatic maintenance of the valve matrix. We propose that the trilayered structure in the native aortic valve that includes a middle spongiosa layer cushioning the motions of the two external fibrous layers should be our template for creation of novel scaffolds with improved mechanical durability. Furthermore, since cells adapt to micro-loads within the valve structure, we believe that interstitial cell remodeling of the valvular matrix will depend on the accurate replication of the structures and loads, resulting in successful regeneration of the valve tissue and extended durability.
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Affiliation(s)
- Dan T Simionescu
- Biocompatibility and Tissue Regeneration Laboratory, Department of Bioengineering, Clemson University, Clemson, SC 29634
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Flameng W, Herregods MC, Vercalsteren M, Herijgers P, Bogaerts K, Meuris B. Prosthesis-Patient Mismatch Predicts Structural Valve Degeneration in Bioprosthetic Heart Valves. Circulation 2010; 121:2123-9. [DOI: 10.1161/circulationaha.109.901272] [Citation(s) in RCA: 183] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Willem Flameng
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
| | - Marie-Christine Herregods
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
| | - Monique Vercalsteren
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
| | - Paul Herijgers
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
| | - Kris Bogaerts
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
| | - Bart Meuris
- From the Divisions of Cardiac Surgery (W.F., B.M., M.V., P.H.) and Cardiology (M.H.), Department of Cardiovascular Diseases, Katholieke Universiteit Leuven, Leuven, Belgium; and Biostatistical Center, Universiteit Hasselt, Diepenbeek, Belgium (K.B.)
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Deiwick M, Glasmacher B, Baba HA, Roeder N, Reul H, von Bally G, Scheld HH. In vitro testing of bioprostheses: influence of mechanical stresses and lipids on calcification. Ann Thorac Surg 1998; 66:S206-11. [PMID: 9930449 DOI: 10.1016/s0003-4975(98)01125-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Structural valve deterioration of bioprostheses is mainly caused by the progressive development of calcification. Mechanical stresses or lipid deposits in porcine aortic leaflets have been proposed as major factors contributing to the calcification process. METHODS A new test protocol consisting of nondestructive holographic interferometry, which allows a quantitative deformation analysis of heart valves, and accelerated dynamic in vitro calcification was used. The rapid calcification fluid contained a final combined calcium and phosphorus concentration of 130 (mg/dL)2 in barbital buffer solution. The calcification of 32 bioprostheses donated by different manufacturers (SJM Bioimplant, Biocor standard, Biocor No-React, Carpentier-Edwards SAV, Bravo, pericardial prototype) was assessed after up to 25 x 10(6) cycles by microradiography and the areas of calcification were compared with the holographic interferograms. The distribution of lipid droplets of four porcine prostheses were visualized by Sudan III stain before the calcification process. RESULTS Most of the tested bioprostheses had areas presenting with stress concentrations, and the dynamic in vitro testing resulted in leaflet calcification corresponding to the holographic irregularities. A strong correlation between calcification and stress distribution or lipid accumulation was found (r = 0.72; r = 0.81, respectively). After 19 x 10(6) cycles, the Carpentier-Edwards SAV and the pericardial valves had significantly less calcification than other prostheses tested (p = 0.003), but the variation among individual prostheses from the same manufacturer was even more pronounced. CONCLUSIONS Mechanical stresses or lipid accumulation seems to play an important role in the calcification process of bioprostheses. Quality control of bioprosthetic valves using holographic interferometry has the potential to predict calcification before implantation.
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Affiliation(s)
- M Deiwick
- Department of Cardiothoracic Surgery, Gerhard-Domagk-Institute for Pathology, Westfälische Wilhelms-University, Münster, Germany.
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Bortolotti U, Milano A, Mazzaro E, Thiene G, Talenti E, Casarotto D. Hancock II porcine bioprosthesis: excellent durability at intermediate-term follow-up. J Am Coll Cardiol 1994; 24:676-82. [PMID: 8077538 DOI: 10.1016/0735-1097(94)90014-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVES This study aimed to assess the clinical performance and durability of a new generation of porcine valve, the Hancock II bioprosthesis, at intermediate-term follow-up. BACKGROUND Standard porcine bioprostheses undergo progressive structural deterioration, mainly due to cusp and commissural calcification, affecting durability and requiring reoperation. The Hancock II bioprosthesis, which is currently undergoing clinical investigation, is made from a porcine aortic valve treated with a calcium-retarding agent (sodium dodecyl sulfate [T6]), which should delay onset of calcification and increase durability. METHODS From May 1983 to December 1992, we used the Hancock II bioprothesis in aortic (59 patients), mitral (101 patients) and mitral-aortic (25 patients), valve replacement procedures. Postoperative follow-up ranged from 0.1 to 8.7 years (mean [+/- SD] 4.5 +/- 2.6 years) and was 100% complete. Freedom from major postoperative events was calculated at 7 years for patients with aortic valve replacement and at 8 years for those with mitral and mitral-aortic valve replacement. RESULTS The actuarial survival rate was 48 +/- 10%, 76 +/- 3% and 63 +/- 6%; freedom from valve-related mortality was 91 +/- 4%, 94 +/- 2% and 89 +/- 6%; freedom from thromboembolism was 80 +/- 11%, 90 +/- 2% and 79 +/- 7%; and freedom from reoperation was 100%, 97 +/- 1% and 89 +/- 6% after aortic, mitral and mitral-aortic valve replacement, respectively. No structural valve deterioration occurred. CONCLUSIONS At intermediate-term follow-up the Hancock II bioprosthesis showed excellent durability in all positions. However, the effectiveness of anticalcification treatment must be assessed with longer follow-up studies.
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Affiliation(s)
- U Bortolotti
- Department of Cardiovascular Surgery, University of Padova Medical School, Italy
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Levy RJ, Schoen FJ, Flowers WB, Staelin ST. Initiation of mineralization in bioprosthetic heart valves: studies of alkaline phosphatase activity and its inhibition by AlCl3 or FeCl3 preincubations. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1991; 25:905-35. [PMID: 1918108 DOI: 10.1002/jbm.820250802] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The principal cause of the clinical failure of bioprosthetic heart valves fabricated from glutaraldehyde-pretreated porcine aortic valves is calcification. Other prostheses composed of tissue-derived and polymeric biomaterials also are complicated by deposition of mineral. We have previously demonstrated that: (a) Failure due to calcification of clinical bioprosthetic valves can be simulated by either a large animal circulatory model or subdermal implants in rodents. (b) Calcification of bioprosthetic tissue has complex host, implant, and mechanical determinants. (c) The initial calcification event in the rat subdermal model is the mineral deposition in devitalized cells intrinsic to the bioprosthetic tissue within 48 to 72 h, followed later by collagen mineralization. (d) Initiation of bioprosthetic tissue mineralization, like that of physiological bone formation, has "matrix vesicles" as early nucleation sites. (e) Alkaline phosphatase (AP), an enzyme also associated with matrix vesicles involved in bone mineral nucleation, is present in both fresh and fixed bioprosthetic tissue at sites of initial mineralization. (f) Certain inhibitors of bioprosthetic tissue calcification (e.g., Al3+, Fe3+) are localized to the sites at which alkaline phosphatase is present. On the basis of these results, we hypothesize that alkaline phosphatase is a key element in the pathogenesis of mineralization of bioprosthetic tissue. In the present studies, we focused on the relationship of AP to early events in calcification, and the inhibition of both calcification and AP activity by FeCl3 and AlCl3 preincubations. Subdermal implants of glutaraldehyde pretreated bovine pericardium (GPBP) were done in 3-week-old rats. AP was characterized by enzymatic hydrolysis of paranitrophenyl phosphate (pnpp), and by histochemical studies. Calcification was evaluated chemically (by atomic adsorption spectroscopy) and morphologically (by light microscopy). The results of these studies are as follows: (a) Extractable AP activity is present in fresh but not glutaraldehyde-pretreated bovine pericardial tissue. However, histochemical studies reveal active AP within the intrinsic devitalized cells of GPBP, despite extended glutaraldehyde incubation. (b) Extrinsic AP is rapidly adsorbed following implantation, with peak activity at 72 h (424 +/- 67.2 nm pnpp/mg protein/min enzyme activity [units]), but markedly lesser amounts at 21 days (96.8 +/- 3.9 units). (c) Simultaneously to the AP activity maximum, bulk calcification is initiated, with GPBP calcium levels rising from 1.2 +/- 0.1 (unimplanted) to 2.4 +/- 0.2 micrograms/mg at 72 h, to 55.6 +/- 3.1 micrograms/mg at 21 days, despite a marked decline in AP activity at this later time.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R J Levy
- Department of Pediatrics, University of Michigan, Ann Arbor 48109
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