New engineering treatment of bovine pericardium confers outstanding resistance to calcification in mitral and pulmonary implantations in a juvenile sheep model

CardioCel® for repair of congenital heart defects: nationwide results of over 1000 implants

OBJECTIVES

To assess the mid-term performance of CardioCel for the repair of congenital heart defects.

METHODS

Data were retrospectively collected from databases and hospital records in 3 congenital cardiac surgery centres in Australia. Kaplan-Meier curves and log-rank tests were used to test for associations between patient age, gender, patch type and site of implantation. Multivariable Cox regression was used to test whether any specific implantation site was associated with reintervention risk, after adjusting for age group, gender and patch type.

RESULTS

A total of 1184 CardioCel patches were implanted in 752 patients under the age of 18 years. Median age at implant was 12 months [interquartile range (IQR) 3.6-84]. Median follow-up was 2.1 years (IQR 0.6-4.6). Probability of freedom from CardioCel-related reintervention was 93% [95% confidence interval (CI) 91-95] at 1 year, 91% (95% CI 88-93) at 3 years and 88% (95% CI 85-91) at 5 years, respectively. On multivariable regression analysis, aortic valve repair had a higher incidence of reintervention [hazard ratio (HR) = 7.15, P = 0.008] compared to other sites. The probability of reintervention was higher in neonates (HR = 6.71, P = 0.0007), especially when used for augmentation of the pulmonary arteries (HR = 14.38, P = 0.029), as compared to other age groups.

CONCLUSIONS

CardioCel can be used for the repair of a variety of congenital heart defects. In our study, in patients receiving a CardioCel implant, reinterventions were higher when CardioCel was used to augment the pulmonary arteries in neonates and for aortic valve repair as compared to other sites.

Functional regeneration at the blood-biomaterial interface

The use of cardiovascular implants is commonplace in clinical practice. However, reproducing the key bioactive and adaptive properties of native cardiovascular tissues with an artificial replacement is highly challenging. Exciting new treatment strategies are under development to regenerate (parts of) cardiovascular tissues directly in situ using immunomodulatory biomaterials. Direct exposure to the bloodstream and hemodynamic loads is a particular challenge, given the risk of thrombosis and adverse remodeling that it brings. However, the blood is also a source of (immune) cells and proteins that dominantly contribute to functional tissue regeneration. This review explores the potential of the blood as a source for the complete or partial in situ regeneration of cardiovascular tissues, with a particular focus on the endothelium, being the natural blood-tissue barrier. We pinpoint the current scientific challenges to enable rational engineering and testing of blood-contacting implants to leverage the regenerative potential of the blood.

Performance of CardioCel in Cardiac Surgery: A Systematic Review

A systematic review was performed for evaluation of the performance of CardioCel^® in cardiac surgery. The review included all studies published from January 2013 to December 2020. We conclude that CardioCel is a strong, flexible tissue substitute with good handling characteristics and a low incidence of thrombosis, aneurysm formation, infection, or structural degeneration. It can be used for a variety of intracardiac and extracardiac repairs of congenital heart defects in all age groups with good durability at mid-term follow-up. However, the use of CardioCel in certain positions requires caution. Information on the long-term performance of CardioCel is lacking.

What's New with TAVR? An Update on Device Technology

Over the last 20 years, transcatheter aortic valve replacement (TAVR) has revolutionized the management of aortic stenosis and has become the standard of care across the entire spectrum of surgical risk. Expansion of TAVR in treating younger, lower-risk patients with longer life expectancies, and treating earlier in the disease process, has seen a continuous evolution in device technology, with several next-generation transcatheter heart valves developed to minimize procedural complications and improve patient outcomes. This review provides an update on the latest advances in transcatheter delivery systems, devices, and leaflet technology.

Decellularized Bovine Pericardial Patch Loaded With Mesenchymal Stromal Cells Enhance the Mechanical Strength and Biological Healing of Large-to-Massive Rotator Cuff Tear in a Rat Model

PURPOSE

The purpose of this study was to determine whether the addition of decellularized bovine pericardial patch loaded with mesenchymal stromal cells enhanced bone-to-tendon healing and improved the biomechanical strength of large-to-massive rotator cuff tears in a small animal model.

METHODS

Adipose-derived mesenchymal stromal cells (MSCs) from rat inguinal fat were isolated, cultured, and loaded onto decellularized bovine pericardium patches. To simulate large-to-massive tears, rats were managed with free cage activity for 6 weeks after tear creation. A total of 18 rats were randomly allocated to repair-only (control), repair with pericardial patch augmentation (patch), or repair with MSC loaded pericardial patch augmentation (patch-MSC). Each group had 6 rats (one shoulder of each rat was used for histological evaluation and another for biomechanical evaluation). MSCs seeded on the pericardial patches were traced on four shoulders from 2 other rats at 4 weeks after surgery. Histological evaluation for bone-to-tendon healing and biomechanical testing was carried out at 8 weeks after repair.

RESULTS

MSCs tagged with a green fluorescent protein were observed in the repair site 4 weeks after the repair. One shoulder each in the control and patch groups showed complete discontinuity between the bone and tendon. One shoulder in the control group showed attenuation with only a tenuous connection. Fibrocartilage and tidemark formation at the bone-to-tendon interface (P = .002) and collagen fiber density (P = .040) and orientation (P = .003) were better in the patch-MSC group than in the control or patch group. Load-to-failure in the patch-MSC and patch groups was higher than that in the control group (P = .001 and .009, respectively).

CONCLUSION

Decellularized bovine pericardial patches loaded with adipose-derived and cultured mesenchymal stromal cells enhanced healing in terms of both histology and mechanical strength at 8 weeks following rotator cuff repair in a rat model.

CLINICAL RELEVANCE

Large-to-massive rotator tears need a strategy to prevent retear and enhance healing. The addition of decellularized bovine pericardial patch loaded with MSCs can enhance bone-to-tendon healing and improve biomechanical healing of large-to-massive rotator cuff tears following repair.

ECM roles and biomechanics in cardiac tissue decellularization

Natural biomaterials hold enormous potential for tissue regeneration. The rapid advance of several tissue-engineered biomaterials, such as natural and synthetic polymer-based scaffolds, has led to widespread application of these materials in the clinic and in research. However, biomaterials can have limited repair capacity; obstacles result from immunogenicity, difficulties in mimicking native microenvironments, and maintaining the mechanical and biochemical (i.e., biomechanical) properties of native organs/tissues. The emergence of decellularized extracellular matrix (ECM)-derived biomaterials provides an attractive solution to overcome these hurdles since decellularized ECM provides a nonimmune environment with native three-dimensional structures and bioactive components. More importantly, decellularized ECM can be generated from the tissue of interest, such as the heart, and keep its native macro- and microstructure and tissue-specific composition. These decellularized cardiac matrices/scaffolds can then be reseeded using cardiac cells, and the resulting recellularized construct is considered an ideal choice for regenerating functional organs/tissues. Nonetheless, the decellularization process must be optimized and depends on tissue type, age, and functional goal. Although most decellularization protocols significantly reduce immunogenicity and deliver a matrix that maintains the tissue macrostructure, suboptimal decellularization can change ECM composition and microstructure, which affects the biomechanical properties of the tissue and consequently changes cell-matrix interactions and organ function. Herein, we review methods of decellularization, with particular emphasis on cardiac tissue, and how they can affect the biomechanics of the tissue, which in turn determines success of reseeding and in vivo viability. Moreover, we review recent developments in decellularized ECM-derived cardiac biomaterials and discuss future perspectives.

Human-derived decellularized extracellular matrix scaffold incorporating autologous bone marrow stem cells from patients with congenital heart disease for cardiac tissue engineering

BACKGROUND

Stem cells are used as an alternative treatment option for patients with congenital heart disease (CHD) due to their regenerative potential, but they are subject to low retention rate in the injured myocardium. Also, the diseased microenvironment in the injured myocardium may not provide healthy cues for optimal stem cell function.

OBJECTIVE

In this study, we prepared a novel human-derived cardiac scaffold to improve the functional behaviors of stem cells.

METHODS

Decellularized extracellular matrix (ECM) scaffolds were fabricated by removing cells of human-derived cardiac appendage tissues. Then, bone marrow c-kit+ progenitor cells from patients with congenital heart disease were seeded on the cardiac ECM scaffolds. Cell adhesion, survival, proliferation and cardiac differentiation on human cardiac decellularized ECM scaffold were evaluated in vitro. Label-free mass spectrometry was applied to analyze cardiac ECM proteins regulating cell behaviors.

RESULTS

It was shown that cardiac ECM scaffolds promoted stem cell adhesion and proliferation. Importantly, bone marrow c-kit+ progenitor cells cultured on cardiac ECM scaffold for 14 days differentiated into cardiomyocyte-like cells without supplement with any inducible factors, as confirmed by the increased protein level of Gata4 and upregulated gene levels of Gata4, Nkx2.5, and cTnT. Proteomic analysis showed the proteins in cardiac ECM functioned in multiple biological activities, including regulation of cell proliferation, regulation of cell differentiation, and cardiovascular system development.

CONCLUSION

The human-derived cardiac scaffold constructed in this study may help repair the damaged myocardium and hold great potential for tissue engineering application in pediatric patients with CHD.

Reconstruction of the Aortic Arch in Neonates and Infants: The Importance of Patch Material

Objectives:

Restenosis after aortic arch reconstruction is a known complication in neonates and infants. Homograft is the most commonly used patch material for aortic arch reconstructions in our center. Since 2014, tissue-engineered bovine pericardium (CardioCel) has been used as an alternative. The aim of our study was to determine whether the choice of material affected the development of restenosis in these patients.

Methods:

Data of all neonates and infants who underwent aortic arch reconstruction with the use of any patch material between 2005 and 2016 were analyzed. Restenosis was defined by the need for reintervention, either percutaneous or surgical.

Results:

Forty-one patients underwent aortic arch repair. Excluding the 30-day mortality, 36 patients represented the study population. At primary repair, the aortic arch was reconstructed with homograft (n = 26) or CardioCel (n = 10). Restenosis was documented during the first year of life in 13 patients: Six (23%) patients in the homograft group and seven (70%) patients in the CardioCel group (P = .01). In the homograft group, the median time from operation to first intervention for restenosis was 22.0 (range: 14-32) weeks, as compared to 14.0 (range: 7-21) weeks in the CardioCel group (P = .04).

Conclusion:

We conclude that choice of patch material is likely to be an important determinant for the risk of restenosis needing reintervention following reconstruction of the aortic arch in neonates and infants.

Echocardiographic changes in patients with a cylinder mitral valve replacement: Preliminary analysis

AIMS

Cylinder mitral valve construct (cMVC) is new technique for replacing the mitral valve compared to more traditional mitral valve replacement (MVR) procedures. Goal of this study was to describe echocardiographic changes over time in patients undergoing a cMVC. Secondary goal was to compare echocardiographic changes in patients that underwent a cMVC to a group of patients that underwent a MVR.

METHODS

Retrospective analysis of patients undergoing a cMVC was performed. Demographics, discharge echocardiogram, and recent echocardiogram vales were evaluated. Age matched patients undergoing a MVR were assessed. Discharge and recent echocardiographic parameters were compared within the cMVC group. cMVC and MVR values were compared between groups.

RESULTS

Five cMVC patients were studied. Age at surgery for the cMVC was 4.3 ± 4.2 years (median 2.2, .8-10.3 years). Time interval from hospital discharge echocardiogram to the most recent echocardiogram was 1.2 ± .7 years (median 1.0, .6-2.0 years). Mean mitral valve gradient significantly increased over time (3.6 ± 3.0 mm Hg vs 7.6 ± 2.9 mm Hg). There were significant improvements in left ventricular diameters, systolic sphericity index, shortening fraction, and ejection fraction over time. There were no significant differences in demographics, discharge echocardiogram values, and follow up echocardiogram values between the cMVC and MVR groups.

CONCLUSION

In conclusion, echocardiographic indices of left ventricular function improved over time in patients undergoing cMVC. In addition, there were no significant differences between cMVC and MVR patients in echocardiographic values. Studies with a larger patient sample with longer follow up are needed to determine if cMVC continues to have comparable echocardiographic results to MVR.

Decellularized xenografts in regenerative medicine: From processing to clinical application

Decellularized xenografts are an inherent component of regenerative medicine. Their preserved structure, mechanical integrity and biofunctional composition have well established them in reparative medicine for a diverse range of clinical indications. Nonetheless, their performance is highly influenced by their source (ie species, age, tissue) and processing (ie decellularization, crosslinking, sterilization and preservation), which govern their final characteristics and determine their success or failure for a specific clinical target. In this review, we provide an overview of the different sources and processing methods used in decellularized xenografts fabrication and discuss their effect on the clinical performance of commercially available decellularized xenografts.

Decellularization and engineered crosslinking: a promising dual approach towards bioprosthetic heart valve longevity

OBJECTIVES

METHODS

Bovine and porcine pericardium were decellularized using the standard Triton X/sodium deoxycholate/DNAse/RNAse methodology and thereafter combined incrementally with components of a four-stage high-density dialdehyde-based fixation regimen. Mechanical properties prior to, and calcium levels following, subcutaneous implantation for 6 and 10 weeks in rats were assessed.

RESULTS

Enhanced four-stage crosslinking, independent of decellularization, or decellularization followed by any of the crosslinking regimens, achieved sustained, near-elimination of tissue calcification. Decellularization additionally resulted in significantly lower tissue stiffness and higher fatigue resistance in all groups compared to their non-decellularized counterparts.

CONCLUSIONS

The dual approach of combining decellularization with enhanced crosslinking chemistry in xenogeneic pericardial tissue offers much promise in extending bioprosthetic heart valve longevity.

Histological examination of explanted tissue-engineered bovine pericardium following heart valve repair

OBJECTIVES

Our goal was to present histopathological findings of human explants of a tissue-engineered bovine pericardium CardioCel (Admedus Regen Pty Ltd, Malaga, WA, Australia) used for heart valve repair in patients with congenital and acquired heart valve disease.

METHODS

Sixty patients underwent heart valve repair from May 2014 to November 2018 using CardioCel as a substitute for valve tissue. We identified 9 cases in which the CardioCel patch was explanted following valve repair and available for histomorphological analyses. CardioCel explants were evaluated histologically using haematoxylin and oeosin, Elastica van Gieson and immunohistochemical stains.

RESULTS

The indications for explantation were related to the CardioCel patch in 6 patients. Median time between the implantation and explantation was 242 (range 3-1247) days. We demonstrated a characteristic remodelling pattern with superficial coating of the tissue-engineered bovine pericardium by granulation tissue composed of histiocytes, few lymphocytes and fibrin. We had 2 cases with a multifocal nodular disruption, fragmentation and sclerosis of the decellularized collagen matrix with focal calcification after 795 and 1247 days in situ.

CONCLUSIONS

Our data suggest that the tissue-engineered CardioCel patch is initially tolerated in the valvular position in the majority of patients. However, we also experienced graft failures that showed degeneration with fragmentation of the collagen matrix and even 2 cases with focal calcification evident from the histopathological analysis. Further analyses of mid- and long-term performance are mandatory.

The Ozaki Procedure With CardioCel Patch for Children and Young Adults With Aortic Valve Disease: Preliminary Experience – a Word of Caution

Background:

The Ozaki procedure is a surgical technique for patients with significant aortic stenosis or regurgitation or both where valve repair cannot be performed. Individual cusps are cut from glutaraldehyde-treated autologous pericardium or bovine pericardium and implanted into the aortic valve position. Encouraging results have been reported within the adult population. There are limited published data on success of this procedure in younger patients.

Methods:

We present a series of five children and young adults who underwent the Ozaki procedure with neoaortic valve cusps made from CardioCel, a decellularized bovine pericardial patch treated with a monomeric glutaraldehyde.

Results:

There were no complications in the initial postoperative period and short inpatient stay. At a mean follow-up of 29.6 months (range: 22-36 months), 4 patients had no evidence of stenosis and 3 patients had trivial or no regurgitation from the neoaortic valve. Overall, two patients had complications related to the valve and underwent reintervention during the follow-up period with a Ross procedure. One of these patients who was not taking long-term anticoagulation experienced a transient ischemic attack.

Conclusions:

Our experience demonstrates that the Ozaki procedure with CardioCel in pediatric and young adult patients should be approached with caution. Further research with larger groups of pediatric patients, comparison of different graft materials, and longer follow-up is required to ascertain long-term success in children.

Decellularization as a method to reduce calcification in bovine pericardium bioprosthetic valves

OBJECTIVES

Decellularization is an alternative method for processing biological tissues with decreased antigenicity and resistance to calcification. The aim of this study was to characterize the properties of decellularized (dCell) bovine pericardium fixed with 0.1% glutaraldehyde (GA) and to evaluate outcomes of bioprosthetic valves constructed with this tissue when implanted in the mitral position of juvenile sheep.

METHODS

Bioprosthetic mitral valves were constructed with fresh bovine pericardium fixed in 0.5% GA (control group) or dCell bovine pericardium fixed in 0.1% GA (study group). Before implantation, samples were submitted to histological (haematoxylin-eosin, Movat and 4',6-diamidino-2-phenylindole), biochemical (residual deoxyribonucleic acid and α-gal epitopes) and biomechanical characterization. Valves were implanted (n = 8 in each group) as a mitral valve replacement for 180 days in sheep and explants were re-evaluated histologically and for calcification with radiological studies and calcium content determination.

RESULTS

Unimplanted dCell pericardia exhibited a well-preserved extracellular matrix with absence of cells, a 77% reduction in deoxyribonucleic acid levels and with no detectable α-gal epitopes. When compared to controls, they had lower ultimate tensile strength (7.3 ± 5.4 vs 10.2 ± 3.0 mPa, P = 0.04) and greater percentage elongation in the longitudinal direction (29 ± 6.5% vs 23.8 ± 5.1%, P = 0.02). After 180 days in mitral position, dCell valves showed pliable leaflets without macroscopic signs of calcification. Histologically, dCell leaflets had intact collagen fibres, better tissue remodelling and a significant 89% reduction in calcium content.

CONCLUSIONS

This study demonstrates that bioprosthetic valves constructed with dCell bovine pericardium fixed in low GA concentration were resistant to calcification and may thereby improve long-term durability of the tissue.

Acellular Extracellular Matrix Bioscaffolds for Cardiac Repair and Regeneration

Heart failure is a progressive deterioration of cardiac pump function over time and is often a manifestation of ischemic injury caused by myocardial infarction (MI). Post-MI, structural remodeling of the infarcted myocardium ensues. Dysregulation of extracellular matrix (ECM) homeostasis is a hallmark of structural cardiac remodeling and is largely driven by cardiac fibroblast activation. While initially adaptive, structural cardiac remodeling leads to irreversible heart failure due to the progressive loss of cardiac function. Loss of pump function is associated with myocardial fibrosis, wall thinning, and left ventricular (LV) dilatation. Surgical revascularization of the damaged myocardium via coronary artery bypass graft (CABG) surgery and/or percutaneous coronary intervention (PCI) can enhance myocardial perfusion and is beneficial. However, these interventions alone are unable to prevent progressive fibrotic remodeling and loss of heart function that leads to clinical end-stage heart failure. Acellular biologic ECM scaffolds can be surgically implanted onto injured myocardial regions during open-heart surgery as an adjunct therapy to surgical revascularization. This presents a novel therapeutic approach to alter maladaptive remodeling and promote functional recovery. Acellular ECM bioscaffolds have been shown to provide passive structural support to the damaged myocardium and also to act as a dynamic bioactive reservoir capable of promoting endogenous mechanisms of tissue repair, such as vasculogenesis. The composition and structure of xenogenic acellular ECM bioscaffolds are determined by the physiological requirements of the tissue from which they are derived. The capacity of different tissue-derived acellular bioscaffolds to attenuate cardiac remodeling and restore ECM homeostasis after injury may depend on such properties. Accordingly, the search and discovery of an optimal ECM bioscaffold for use in cardiac repair is warranted and may be facilitated by comparing bioscaffolds. This review will provide a summary of the acellular ECM bioscaffolds currently available for use in cardiac surgery with a focus on how they attenuate cardiac remodeling by providing the necessary environmental cues to promote endogenous mechanisms of tissue repair.

Comparison of physical and biological properties of CardioCel® with commonly used bioscaffolds

OBJECTIVES

Durability of bioscaffolds cross-linked with glutaraldehyde and used in cardiovascular surgery is limited by biomechanical instability, calcification and reduced biocompatibility. This study compares CardioCel®, a bovine pericardial scaffold engineered via the ADAPT® process to ensure optimized biostability and biocompatibility, with the commonly used bioscaffolds.

METHODS

Bovine pericardial scaffolds, cross-linked with 0.6% glutaraldehyde (XenoLogiX™, PeriGuard®), dye-mediated photo-oxidized (PhotoFix™) and a non-crosslinked porcine scaffold (CorMatrix®), were compared with CardioCel (decellularized, cross-linked with 0.05% monomeric glutaraldehyde, detoxified) by thermal stability and mechanical tests. Biocompatibility and calcification were assessed in a juvenile subcutaneous rat model at 6 and 12 weeks.

RESULTS

CardioCel displayed significantly higher (P < 0.01) cross-link stability (77.99 ± 0.64 °C) than CorMatrix (57.88 ± 0.22 °C) and PhotoFix (53.96 ± 0.41 °C). Tensile strength of CardioCel (8.31 ± 3.36 MPa) was comparable with XenoLogiX (11.00 ± 5.43 MPa, P = 0.734), PeriGuard (16.44 ± 6.69 MPa, P = 0.136), PhotoFix (7.10 ± 6.11, P = 0.399) and CorMatrix (9.75 ± 2.61, P = 0.204). XenoLogiX and PeriGuard recorded the highest Young's modulus (67.01 ± 30.36 vs 95.67 ± 45.91 MPa), while CardioCel (50.21 ± 19.92 MPa) was comparable with CorMatrix (36.78 ± 10.47 MPa, P = 0.204) and PhotoFix (33.50 ± 10.24, P = 0.399). CorMatrix displayed a significantly (P < 0.05) greater stiffness (4.74 ± 0.77 MPa) at 10% strain than PeriGuard (3.73 ± 1.79 MPa), PhotoFix (1.59 ± 0.40 MPa) and CardioCel (3.39 ± 0.83 MPa). Differences in extractable calcium did not reach significance; however, the inorganic phosphorus content of PhotoFix (21.3 ± 9.0 µg/mg) was higher than CardioCel (11.35 ± 0.76 µg/mg, P = 0.004) or PeriGuard (10.7 ± 2.18 µg/mg, P = 0.002) at 12 weeks. CardioCel underwent a typical mild host-graft response with fibroblast infiltration and remodelling. Foreign body reactions were visible in both XenoLogiX and PeriGuard, with isolated fibroblast infiltration. PhotoFix showed severe inflammation and 2 implants were completely degraded at 12 weeks.

CONCLUSIONS

CardioCel demonstrated optimized physical properties, minimal mineralization potential and superior biocompatibility. These results may benefit the long-term performance of this bioscaffold for cardiovascular surgery. The favourable characteristics of the comparator products were counterbalanced by less desirable features that may have negative implications on durability and performance when used in cardiovascular procedures.

Initial 2-year results of CardioCel® patch implantation in children

OBJECTIVES

We present the initial 2-year results of CardioCel® patch (Admedus Regen Pty Ltd, Perth, WA, Australia) implantation in paediatric patients with congenital heart diseases.

METHODS

This was a single-centre retrospective study with prospectively collected data of all patients aged 18 years and under operated for congenital heart disease. The patch was introduced in 2014, with clinical practice committee approval and a special consent in case of an Ozaki procedure. Standard follow-up was performed with systematic clinical exams and echocardiograms. In case of reoperation or graft failure, the patch was removed and sent for a histological examination.

RESULTS

Between March 2014 and April 2016, 101 patients had surgical repair using a CardioCel patch. The mean age was 22 (±36.3) months, and the mean weight was 9.7 (±10.3) kg. No infections and no intraoperative implantation difficulties were associated with the patch. The median follow-up period was 212 (range 4-726) days. The overall 30-day postoperative mortality was 3.8% (n = 4), none of which were related to graft failure. Five children were reoperated because of graft failure, 4 of whom had the patch implanted for aortic and were aged less than 10 days. The indications for patch implantation in the aortic position were aortopulmonary window, truncus arteriosus, coarctation and aortic arch hypoplasia repair. The median time between the first and the second operation for graft failure was 245 (range 5-480) days.

CONCLUSIONS

Our experience shows that the patch is well tolerated in the septal, valvar and pulmonary artery positions. However, we experienced graft failures in infants in the aortic position.

Aortic and mitral valve repair for anterior mitral leaflet perforation caused by severe aortic regurgitation

A 23-year-old man presented with acute onset of dyspnea on exert. Preoperative echocardiography showed a severe regurgitation of the bicuspid aortic valve (due to prolapse of the fused cusp) creating a jet directed through the defect in the anterior leaflet of the mitral valve. Both valves were repaired. Endocarditis was excluded with cultures and polymerase chain reaction (PCR). Postoperative course was uneventful.

Initial Experience and Early Results of Mitral Valve Repair With CardioCel Pericardial Patch

PURPOSE

The objective of this study was to assess the performance of a tissue engineering process-treated bovine pericardium patch (CardioCel, Admedus Regen Pty Ltd, Perth, Australia) in the setting of reconstructive mitral valve surgical procedures.

DESCRIPTION

Between March 2014 and April 2016, 30 patients (57.2 ± 14.3 years of age; 27% female) underwent mitral valve leaflet repair with a CardioCel patch.

EVALUATION

Perioperative mortality was 7% (2 patients, non-graft related). In the 28 remaining patients, predischarge echocardiography demonstrated good repaired valve function. At a mean follow-up of 1.7 ± 0.9 years, three additional deaths occurred (two resulting from infective endocarditis and one non-cardiac related). On follow-up echocardiography (follow-up time of 1.7 ± 0.8 years; available for 26 of 28 [93%] hospital survivors), recurrent regurgitation was seen in 2 patients (both with infective endocarditis), and 1 patient underwent reoperation (no infection at the level of patch repair was observed). In the remaining patients, the most recent echocardiogram demonstrated no regurgitation or mild regurgitation and stable gradients. The thickness and echodensity of the implanted patch on follow-up echocardiograms were comparable with postoperative echocardiograms.

CONCLUSIONS

Initial results with the CardioCel patch in mitral valve repair operations were satisfactory. The resistance to infection and late degeneration will need to be assessed in the future.

Infective Endocarditis Associated With Varicella Zoster Virus Following Aortic Valve Repair

We describe the management and clinical course of two children with congenital bicuspid aortic valve. Neo-tricuspidization was performed in one case using CardioCel leaflets and two cusps were formed from CardioCel and grafted alongside one native leaflet in the other. Both patients developed bacterial endocarditis associated with varicella zoster virus infection and required a second surgical procedure.

Reducing immunoreactivity of porcine bioprosthetic heart valves by genetically-deleting three major glycan antigens, GGTA1/β4GalNT2/CMAH

Bioprosthetic heart valves (BHVs) originating from pigs are extensively used for heart valve replacement in clinics. However, recipient immune responses associated with chronic calcification lead to structural valve deterioration (SVD) of BHVs. Two well-characterized epitopes on porcine BHVs have been implicated in SVD, including galactose-α1,3-galactose (αGal) and N-glycolylneuraminic acid (Neu5Gc) whose synthesis are catalyzed by α(1,3) galactosyltransferase (encoded by the GGTA1 gene) and CMP-Neu5Ac hydroxylase (encoded by the CMAH gene), respectively. It has been reported that BHV from αGal-knockout pigs are associated with a significantly reduced immune response by human serum. Moreover, valves from αGal/Neu5Gc-deficient pigs could further reduce human IgM/IgG binding when compared to BHV from αGal-knockout pigs. Recently, another swine xenoantigen, Sd(a), produced by β-1,4-N-acetyl-galactosaminyl transferase 2 (β4GalNT2), has been identified. To explore whether tissue from GGTA1, CMAH, and β4GalNT2 triple gene-knockout (TKO) pigs would further minimize human antibody binding to porcine pericardium, TKO pigs were successfully produced by CRISPR/Cas9 mediated gene targeting. Our results showed that the expression of αGal, Neu5G and Sd(a) on TKO pigs was negative, and that human IgG/IgM binding to pericardium was minimal. Moreover, the analysis of collagen composition and physical characteristics of porcine pericardium from the TKO pigs indicated that elimination of the three xenoantigens had no significant impact on the physical proprieties of porcine pericardium. Our results demonstrated that TKO pigs would be an ideal source of BHVs.

STATEMENT OF SIGNIFICANCE

Surgical heart valve replacement is an established lifesaving treatment for diseased heart valve. Bioprosthetic heart valves (BHVs) made from glutaraldehyde-fixed porcine or bovine tissues are widely used in clinics but exhibit age-dependent structural valve degeneration (SVD) which is associated with the immune response against BHVs. Three major xenoantigens present on commercial BHVs, Galactosea α1,3 galactose (αGal), N-glycolylneuraminic acid (Neu5Gc) and glycan products of β-1,4-N-acetyl-galactosaminyl transferase 2 (β4GalNT2) are eliminated through CRISPR/Cas9 mediated gene targeting in the present study. The genetically modified porcine pericardium showed reduced immunogenicity but comparable collagen composition and physical characteristics of the pericardium from wild-type pigs. Our data suggested that BHVs from TKO pigs is a promising alternative for currently available BHVs from wild-type pigs.

Patch materials for right ventricular outflow reconstruction: past, present, and future

In this review, we discuss various patch materials used for reconstruction of the right ventricular outflow tract. Their relative merits and demerits are discussed. Traditional patches and their results are detailed along with a brief description of newer developments in the field.

Calcification or Not. This Is the Question. A 1-Year Study of Bovine Pericardial Vascular Patches (CardioCel) in Minipigs

A main problem with bioprosthesis used for surgical correction of congenital cardiac malformation is its tendency to shrink and to calcify. Recently, a new material, that is, decellularized bovine pericardium (CardioCel), was introduced in clinics. It was proposed that this new patch material should not calcify and should be particularly suitable for the correction of vascular defects in inborn cardiac diseases. The aim of our chronic minipig study was to evaluate the performance of CardioCel patches implanted in aortic and pulmonary artery position, respectively. Ten minipigs aged 3 months were operated on. A CardioCel patch was implanted in the aorta ascendens and arteria pulmonalis, respectively. Seven minipigs completed the 12 months' follow-up. Angiography of both vessels, measurement of pressure gradients, and histologic evaluation of the implanted patches were carried out. Angiography of both great vessels revealed a good clinical outcome without stenosis. However, histologic examination of the patches showed calcification and neo-formation of hyaline cartilage in both vessel types. Staining of collagen and elastic fibers as well as α-smooth muscle actin demonstrated that the patches did not remodel into an anatomic vascular structure during the 1 year of implantation. In our chronic piglet model, CardioCel patches, when implanted in the ascending aorta and the pulmonary artery, led to calcification and neo-formation of hyaline cartilage in both vessel types 1 year after implantation. The present study indicates that the ideal patch biomaterial for repair of inborn cardiac diseases is still a goal not achieved yet.

Glutaraldehyde Treatment of Allografts and Aortic Outcomes Post-Norwood: Challenging Surgical Decision

BACKGROUND

Glutaraldehyde (GA) treatment of allografts used for arch reconstruction prevents the immunologic sensitization that occurs with untreated allografts, but its use may cause tissue changes that predispose to recurrent obstruction. The objective was to determine whether GA treatment of allografts used in Norwood procedures increases the risk of recurrent aortic obstruction.

METHODS

All infants who underwent a Norwood procedure between 2000 and 2015 were included. Cryopreserved pulmonary allografts were used for all arch reconstructions; starting in 2005 all were treated with GA before use. Complete follow-up was obtained, including survival, transplantation, and all repeat procedures. Competing risks analyses were used to assess for differences in aortic reintervention over time.

RESULTS

Two hundred six infants (132 male) were included. There were 60 deaths and 14 transplantations; 5-year transplantation-free survival was 71.9%. GA treatment of patches (n = 142, 68.9%) was not predictive of death (hazard ratio [HR] 1.38, 95% confidence interval [CI]: 0.61 to 3.08). Fifty-five patients had at least one aortic reintervention and 31 patients (15.0%) required surgical aortic reintervention. At 1-year, freedom from all aortic reintervention was similar between patients with and without treated patches, but freedom from surgical aortic reintervention was lower in the treated group (87.6% versus 95.3%, p = 0.0256). GA treatment was not associated with the combined end point of catheter-based or surgical reintervention but was associated with specific need for surgical reintervention (HR 4.05, 95% CI: 1.19 to 13.77).

CONCLUSIONS

GA treatment is associated with increased late surgical aortic reintervention. The advantages of decreased sensitization with GA treatment need to be balanced against the risk of aortic reobstruction.

Histologic Evaluation of Explanted Tissue-Engineered Bovine Pericardium (CardioCel)

CardioCel is a bovine pericardium that is subjected to a novel anticalcification tissue-engineering process. We present the histopathologic findings of human explants of CardioCel that were used in operations for congenital heart disease in children. Six explants were identified from 140 patients undergoing CardioCel implants from October 2012 to March 2015. CardioCel explants were evaluated histologically using hematoxylin and eosin, Masson trichrome, and immunohistochemical staining. A variable inflammatory response was seen in the surrounding native tissue, but not within the CardioCel graft in any of the explants. A neointimal layer of varying thickness developed on the visceral surface of 5 CardioCel explants with endothelialization of the longest duration explant. A granulation tissue layer developed on the parietal surface of the graft (consistently thicker than the neointima). Maintained collagen fiber architecture (laminated) and variable fibroblastic invasion (which increased with the age of the implant) were identified in all 6 cases. Scattered capillary vessels were noted in the majority of the explants with new collagen fibers in one, suggesting early remodeling. Calcium was seen in 1 explant at the interface of the graft and inflammatory response on its parietal surface. Evidence of graft remodeling was noted in the majority of the explants without inflammatory cells or calcification within the explanted graft material. A noticeable feature was the differential thickness of the host reaction to the parietal compared with the visceral surface of the graft. We will continue to evaluate CardioCel as a cardiovascular substitute for extracardiac and intracardiac reconstructions.

Application of the CardioCel bovine pericardial patch - a preliminary report

Introduction

Animal pericardial patches are widely used in adult and pediatric cardiac surgery. A search is ongoing for a new material with optimal surgical properties that will reduce intraoperative bleeding and the occurrence of restenosis, calcification, and pseudoaneurysms in long-term observation. One product of interest is the CardioCel bovine pericardial patch.

Aim

Evaluation of the short-term results of CardioCel bovine pericardial patch implantation during pediatric cardiac surgery.

Material and methods

The study included 8 patients who underwent surgical correction of congenital cardiac defects between January 2015 and February 2016. Pericardial patches were used to repair supravalvular aortic stenosis and reconstruct the aortic arch and pulmonary arteries. The age of the patients ranged from 10 days to 14 years.

Results

There were no hospital deaths. The new material exhibited satisfactory durability and elasticity during surgery, facilitating optimal adaptation of the patch to the patient's tissues. No significant bleeding was reported from the suture site. The median duration of follow-up was 58 days. During the follow-up, there were no symptoms of pseudoaneurysm formation, patch thickening, or calcification in the areas where the pericardial patches were implanted. No clinical or laboratory symptoms of infection were observed in locations where the new material was applied.

Conclusions

Satisfactory surgical properties of the patch were observed intraoperatively. Positive results using the new pericardial patch were obtained in short-term follow-up.

Physical equivalency of wild type and galactose α 1,3 galactose free porcine pericardium; a new source material for bioprosthetic heart valves

Humans make high levels of antibody to carbohydrates with terminal galactose α 1,3 galactose (Gal) modifications. This Gal antigen is widely expressed in other mammals and is present on an array of current animal derived biomedical devices including bioprosthetic heart valves. There is growing interest in using Gal-free animal tissues from Gal knockout pigs (GTKO) as these tissues would not be affected by anti-Gal antibody mediated injury. In this study we compare the composition and biophysical characteristics of glutaraldehyde fixed porcine pericardium from standard and GTKO pigs. We show that with the exception of the Gal antigen which is only present in standard pig tissue both GTKO and standard pig tissue have the same general morphology and collagen content. Moreover uniaxial stress testing and suture retention testing indicate the tissues are equivalent in tensile strength. These studies indicate that genetic disruption of the α-galactosyltransferase (GGTA-1) which blocks synthesis of the Gal antigen has no significant impact on the structural integrity of porcine pericardium and suggest that this tissue could be directly substituted for standard pig pericardium in biomedical devices such as bioprosthetic heart valves.

STATEMENT OF SIGNIFICANCE

Surgical heart valve replacement is a proven life saving therapy to treat heart valve dysfunction due to birth defects, infection and the effects of aging. Bioprosthetic heart valves (BHV) made from glutaraldehyde fixed animal tissues are an effective durable therapy in older patients (>60years) but exhibit age-dependent structural valve degeneration (SVD) in younger patients (<60years). SVD is principally caused by BHV calcification. Immune injury contributes to age-dependent SVD through the interaction of galactose α 1,3 galactose (Gal) a dominant xenogeneic antigen present on commercial BHVs and universally abundant human anti-Gal antibody. This study measures the tissue equivalency between standard pig pericardium and Gal-free pericardium from genetically modified pigs as a first step towards making Gal-free BHVs.

Noninferiority of Shanghai Cingular biotech's bovine pericardial valve preclinical study in juvenile ovine model

BACKGROUND

This study introduces a newly Chinese domestic-designed/manufactured bovine pericardial valve, the SCBC valve (Shanghai Cingular Biotech Corporation, Shanghai, China), and evaluates its hemodynamic performance and calcification potential compared with the Carpentier-Edwards (CE) Perimount(TM) valve (Edwards Lifesciences, Irvine, CA, USA) in juvenile sheep for preclinical study.

METHODS

Five SCBC valves in study group and three CE Perimount(TM) valves (6900P with TFX) in control group were implanted in the mitral position of juvenile sheep and followed up for five months. Transthoracic echocardiography (TTE) for hemodynamic measurement was performed ten days, three months and five months postoperatively. Valve calcification was assessed by X-ray after euthanasia. Other collected data included macroscopic examination, blood analysis, microorganism culture and histological assessment.

RESULTS

All sheep in two groups lived to sacrifice without evidence of valvular dysfunction. The SCBC valve had similar hemodynamic performance and susceptibility of calcification compared with the CE Perimount(TM) valve in juvenile ovine model. In all other parameters, the SCBC valve also exhibited no significant difference compared with the CE Perimount(TM) valve.

CONCLUSIONS

Our study demonstrated that the SCBC valve can exhibit similar mid-term satisfactory safety and efficacy compared with the CE Perimount(TM) valve in the mitral position of juvenile sheep model.

Current progress in tissue engineering of heart valves: multiscale problems, multiscale solutions

INTRODUCTION

Heart valve disease is an increasingly prevalent and clinically serious condition. There are no clinically effective biological diagnostics or treatment strategies. The only recourse available is replacement with a prosthetic valve, but the inability of these devices to grow or respond biologically to their environments necessitates multiple resizing surgeries and life-long coagulation treatment, especially in children. Tissue engineering has a unique opportunity to impact heart valve disease by providing a living valve conduit, capable of growth and biological integration.

AREAS COVERED

This review will cover current tissue engineering strategies in fabricating heart valves and their progress towards the clinic, including molded scaffolds using naturally derived or synthetic polymers, decellularization, electrospinning, 3D bioprinting, hybrid techniques, and in vivo engineering.

EXPERT OPINION

Whereas much progress has been made to create functional living heart valves, a clinically viable product is not yet realized. The next leap in engineered living heart valves will require a deeper understanding of how the natural multi-scale structural and biological heterogeneity of the tissue ensures its efficient function. Related, improved fabrication strategies must be developed that can replicate this de novo complexity, which is likely instructive for appropriate cell differentiation and remodeling whether seeded with autologous stem cells in vitro or endogenously recruited cells.