[Effects of freeze-drying bovine pericardium using a combination of polyethylene glycol and trehalose].

The freeze-drying is a technology that preserves biological samples in a dry state, which is beneficial for storage, transportation, and cost saving. In this study, the bovine pericardium was treated with a freeze-drying protectant composed of polyethylene glycol (PEG) and trehalose (Tre), and then freeze-dried. The results demonstrated that the mechanical properties of the pericardium treated with PEG + 10% w/v Tre were superior to those of the pericardium fixed with glutaraldehyde (GA). The wet state water content of the rehydrated pericardium, determined using the Karl Fischer method, was (74.81 ± 1.44)%, which was comparable to that of the GA-fixed pericardium. The dry state water content was significantly reduced to (8.64 ± 1.52)%, indicating effective dehydration during the freeze-drying process. Differential scanning calorimetry (DSC) testing revealed that the thermal shrinkage temperature of the pericardium was (84.96 ± 0.49) ℃, higher than that of the GA-fixed pericardium (83.14 ± 0.11) ℃, indicating greater thermal stability. Fourier transform infrared spectroscopy (FTIR) results showed no damage to the protein structure during freeze-drying. Hematoxylin and eosin (HE) staining demonstrated that the freeze-drying process reduced pore formation, prevented ice crystal growth, and resulted in a tighter arrangement of tissue fibers. The frozen-dried bovine pericardium was subjected to tests for cell viability and hemolysis rate. The results revealed a cell proliferation rate of (77.87 ± 0.49)%, corresponding to a toxicity grade of 1. Additionally, the hemolysis rate was (0.17 ± 0.02)%, which is below the standard of 5%. These findings indicated that the frozen-dried bovine pericardium exhibited satisfactory performance in terms of cytotoxicity and hemolysis, thus meeting the relevant standards. In summary, the performance of the bovine pericardium treated with PEG + 10% w/v Tre and subjected to freeze-drying could meet the required standards.

A universal strategy for the construction of polymer brush hybrid non-glutaraldehyde heart valves with robust anti-biological contamination performance and improved endothelialization potential.

With the intensification of the aging population and the development of transcatheter heart valve replacement technology (THVR), clinical demand for bioprosthetic valves is increasing rapidly. However, commercial bioprosthetic heart valves (BHVs), mainly manufactured from glutaraldehyde cross-linked porcine or bovine pericardium, generally undergo degeneration within 10-15 years due to calcification, thrombosis and poor biocompatibility, which are closely related to glutaraldehyde cross-linking. In addition, endocarditis caused by post-implantation bacterial infection also accelerates the failure of BHVs. Herein, a functional cross-linking agent bromo bicyclic-oxazolidine (OX-Br) has been designed and synthesized to crosslink BHVs and construct a bio-functionalization scaffold for subsequent in-situ atom transfer radical polymerization (ATRP). The porcine pericardium cross-linked by OX-Br (OX-PP) exhibits better biocompatibility and anti-calcification property than the glutaraldehyde-treated porcine pericardium (Glut-PP) as well as comparable physical and structural stability to Glut-PP. Furthermore, the resistance to biological contamination especially bacterial infection of OX-PP along with anti-thrombus and endothelialization need to be enhanced to reduce the risk of implantation failure due to infection. Therefore, amphiphilic polymer brush is grafted to OX-PP through in-situ ATRP polymerization to prepare polymer brush hybrid BHV material SA@OX-PP. SA@OX-PP has been demonstrated to significantly resist biological contamination including plasma proteins, bacteria, platelets, thrombus and calcium, and facilitate the proliferation of endothelial cells, resulting in reduced risk of thrombosis, calcification and endocarditis. Altogether, the proposed crosslinking and functionalization strategy synergistically achieves the improvement of stability, endothelialization potential, anti-calcification and anti-biofouling performances for BHVs, which would resist the degeneration and prolong the lifespan of BHVs. The facile and practical strategy has great potential for clinical application in fabricating functional polymer hybrid BHVs or other tissue-based cardiac biomaterials. STATEMENT OF SIGNIFICANCE: Bioprosthetic heart valves (BHVs) are widely used in valve replacements for severe heart valve disease, and clinical demand is increasing year over year. Unfortunately, the commercial BHVs, mainly cross-linked by glutaraldehyde, can serve for only 10-15 years because of calcification, thrombus, biological contamination, and difficulties in endothelialization. Many studies have been conducted to explore non-glutaraldehyde crosslinkers, but few can meet high requirements in all aspects. A new crosslinker, OX-Br, has been developed for BHVs. It can not only crosslink BHVs but also serve as a reactive site for in-situ ATRP polymerization and construct a bio-functionalization platform for subsequent modification. The proposed crosslinking and functionalization strategy synergistically achieves the high requirements for stability, biocompability, endothelialization, anti-calcification, and anti-biofouling propeties of BHVs.

Anisotropic Mechanical Response of Bovine Pericardium Membrane Through Bulge Test and In-Situ Confocal-Laser Scanning.

In this work, we present a new experimental setup for the assessment of the anisotropic properties of Bovine Pericardium (BP) membranes. The chemically fixed BP samples have been subjected to a bulge test with in situ confocal laser scanning at increasing applied pressure. The high resolution topography provided by the confocal laser scanning has allowed to obtain a quantitative measure of the bulge displacement; after polynomial fitting, principal curvatures have been obtained and a degree of anisotropy (DA) has been defined as the normalized difference between the maximum and minimum principal curvatures. The experiments performed on the BP membranes have allowed us to obtain pressure-displacement data which clearly exhibit distinct principal curvatures indicating an anisotropic response. A comparison with curvatures data obtained on isotropic Nitrile Buthadiene Rubber (NBR) samples has confirmed the effectiveness of the experimental setup for this specific purpose. Numerical simulations of the bulge tests have been performed with the purpose of identifying a range of constitutive parameters which well describes the obtained range of DA on the BP membranes. The DA values have been partially validated with biaxial tests available in literature and with suitably performed uni-axial tensile tests.

Dual-crosslinked bioprosthetic heart valves prepared by glutaraldehyde crosslinked pericardium and poly-2-hydroxyethyl methacrylate exhibited improved antithrombogenicity and anticalcification properties.

Bioprosthetic heart valves (BHVs) have been widely used due to the revolutionary transcatheter aortic valve replacement (TAVR) techniques but suffer from a limited lifespan. Previous modification methods of BHVs mainly rely on glutaraldehyde precrosslinking and subsequent modification. In this study, we have engineered a Poly-2-Hydroxyethyl methacrylate (pHEMA) coated BHV based on co-crosslinking and co-polymerization strategies. Our BHV overcomes previous limitations of glutaraldehyde prefixation by introducing free molecules before crosslinking to achieve the crosslinking and allyl moiety immobilization simultaneously. Decellularized porcine pericardium and 2-Amino-4-pentenoic acid (APA) are firstly co-crosslinked by glutaraldehyde to obtain alkenylated porcine pericardium (APA-PP), then APA-PP is copolymerized with hydrophilic monomer 2-Hydroxyethyl methacrylate (HEMA) to prepare pHEMA grafted porcine pericardium (HEMA-PP). Compared with traditional glutaraldehyde crosslinked pericardium (GA), HEMA-PP exhibits decreased cytotoxicity and significantly increased endothelialial cells proliferation (7-folds higher than GA after 3-day incubation). In vitro and ex vivo hemocompatibility studies demonstrate the superiority of HEMA-PP in anti-thrombogenicity, where the platelet adhesion decreased by levels of approximately 89% compared to GA. Moreover, HEMA-PP maintains structurally stable with a low level of calcification in the subcutaneous model. The hydrodynamic performance and durability are proven to meet the requirements of ISO 5840-3. Altogether, HEMA-PP may have the potential for future clinical application. STATEMENT OF SIGNIFICANCE: Currently, bioprosthetic heart valves (BHVs) have drawbacks including cytotoxicity, calcification and thrombosis, which would accelerate structural valvular degeneration and limit the service life of BHVs. We developed a new modification strategy that could simultaneously improve the biocompatibility, anti-calcification and anti-thrombotic properties of BHVs. Moreover, the appropriate durability and hydrodynamic property demonstrated the potential of our strategy for clinical application. This work will potentially prolong the service life of BHVs and provide new insight for the modification of BHVs.

Minimising chemical crosslinking for stabilising collagen in acellular bovine pericardium: Mechanistic insights via structural characterisations.

Chemically crosslinked acellular bovine pericardium (ABP) has been widely used in clinical practice as bioprostheses. To ensure its consistency and durability, crosslinkers are used in excess, with stability guided by indicators including the hydrothermal denaturation temperature, the enzymatic resistance and the degree of crosslinking. Yet, understanding of the intermolecular structure in collagen fibrils which imparts the intrinsic stability of the ABPs is lacking, and the discrepancies in the stability criteria in varied conditions are poorly explained. In this study, synchrotron small-angle X-ray scattering (SAXS) in combination with thermal and colorimetric methods are employed to investigate the changes in the structure and the stability of ABPs during crosslinking using glutaraldehyde (GA) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) at different concentrations. Based on the findings, a mechanism is proposed to explicate the crosslinking effects on collagen structure and the relationship between the structure and each stability indicator. At low crosslinker concentrations, the telopeptidyl-helical linkages are preferred, which cause rearrangements in the intermolecular structure of collagen, and efficiently contribute to its stabilities. Excess crosslinking is revealed by a revert trend in structural changes and the plateauing of the stabilities, assigning to the helical-helical linkages and monovalent bindings. The former would improve thermal stability but not collagenase resistance, whereas the latter have negligible effects. Overall, this study provides a mechanistic understanding of the chemical crosslinking of ABPs, which will contribute to the future development of more efficient and economically viable strategies to produce bioprostheses. STATEMENT OF SIGNIFICANCE: Chemical crosslinking imparts suitable properties to acellular bovine pericardium (ABP) for clinical applications, yet the understanding is lacking on the structure-stability relationship especially under different crosslinking conditions. Structural evidence in this study differentiates the binding sites during crosslinking in collagen fibrils at different crosslinker concentrations, highlighting the excess usage in the conventional crosslinking treatments. The mechanism based on the structure of collagen also successfully explains the dissimilarity in hydrothermal and enzymatic stabilities with varied crosslinking conditions. Future researches focusing on developing biomaterials via chemical crosslinking of ABPs would benefit from this study, for its contribution to the better understanding of the relationship of collagen structure and functions.

Higher epicardial fat in older adults living with HIV with viral suppression and relationship with liver steatosis, coronary calcium and cardiometabolic risks.

OBJECTIVES: HIV infection is associated with ectopic fat deposition, which leads to chronic inflammation and cardiometabolic dysregulation. We assessed the epicardial adipose tissue (EAT) volume and its associated factors among people with HIV (PWH). DESIGN: A cross-sectional study. METHODS: We conducted a cross-sectional study among PWH aged at least 50 years and age-matched and sex-matched HIV-negative older individuals in Bangkok, Thailand. Participants underwent a noncontrast, cardiac computed tomography (CT) scan to assess coronary artery calcium (CAC) score and EAT between March 2016 and June 2017. Multivariate linear regression analyses were used to investigate HIV-related factors, cardiac and metabolic markers associated with EAT volume. RESULTS: Median age was 55 years [interquartile range (IQR) 52-60] and 63% were men. Median duration of antiretroviral therapy (ART) was 16 years with 97% had HIV-1 RNA less than 50 copies/ml and median CD4 + cell count of 617 cells/µl. Median EAT volume was significantly higher in PWH [99 (IQR 75-122) cm 3 ] than HIV-negative individuals [93 (IQR 69-117) cm 3 ], P  = 0.022. In adjusted model, factors associated with EAT volume included male sex ( P  = 0.045), older age ( P  < 0.001), abnormal waist circumference ( P  < 0.001) and HOMA-IR ( P  = 0.01). In addition, higher CAC score was independently associated with EAT volume. Higher mean EAT volume was seen in PWH with severe liver steatosis than those without steatosis ( P  = 0.018). In adjusted PWH-only model, duration of HIV was significantly associated with higher EAT volume ( P  = 0.028). CONCLUSION: In an aging cohort, PWH had higher EAT volume than HIV-negative controls. EAT was also independently associated with central fat accumulation, insulin resistance, liver steatosis and CAC score.

Glycidyl methacrylate-crosslinked fish swim bladder as a novel cardiovascular biomaterial with improved antithrombotic and anticalcification properties.

At present, commercial artificial biological valves are mostly prepared by crosslinking bovine or porcine pericardia with glutaraldehyde. Swim bladder has similar components and lower immunogenicity compared to bovine or porcine pericardium. In this study, we used a glycidyl methacrylate (GMA)-based radical polymerization method to crosslink decellularized swim bladders. Amino and carboxyl groups in the swim bladder were reacted with epoxy groups on GMA to introduce carbon-carbon double bonds to the swim bladder. The results showed that the platelet adhesion of GMA-crosslinked swim bladders (GMA-SBs) decreased by 35%, as compared to that of glutaraldehyde-crosslinked swim bladders (GLUT-SBs). Moreover, the superior anticoagulant property was further verified by the ex vivo arteriovenous shunt assay. Meanwhile, the subcutaneous implantation in rats showed that GMA-SBs were able to effectively inhibit the calcification compared with GLUT-SBs. In conclusion, GMA-SBs showed improved antithrombotic and anticalcification properties compared to GLUT-SBs.

Double-Network Hydrogel Armored Decellularized Porcine Pericardium as Durable Bioprosthetic Heart Valves.

Heart valves have extraordinary fatigue resistance which beat ≈3 billion times in a lifetime. Bioprosthetic heart valves (BHVs) made from fixed heteroplasm that are incrementally used in heart valve replacement fail to sustain the expected durability due to thrombosis, poor endothelialization, inflammation, calcification, and especially mechanical damage induced biocompatibility change. No effective strategy has been reported to conserve the biological properties of BHV after long-term fatigue test. Here, a double-network tough hydrogel is introduced, which interpenetrate and anchor into the matrix of decellularized porcine pericardium (dCell-PP) to form robust and stable conformal coatings and reduce immunogenicity. The ionic crosslinked hyaluronic acid (HA) network mimics the glycocalyx on endothelium which improves antithrombosis and accelerates endothelialization; the chemical crosslinked hydrophilic polyacrylamide (PAAm) network further enhances antifouling properties and strengthens the shielding hydrogels and their interaction with dCell-PP. In vitro and rabbit ex vivo shunt assay demonstrate great hemocompatibility of polyacrylamide/HA hydrogel hybrid PP (P/H-PP). Cell experiments and rat subcutaneous implantation confirm satisfactory endothelialization, biocompatibility, and anticalcification properties. For hydrodynamic experiment, P/H-PP gains full mark at different flow conditions and sustains excellent biomechanical and biological properties after 200 000 000 cycles. P/H double-network hydrogel armoring dCell-PP is a promising progress to extend BHV durability for clinical implantation therapy.

Preliminary hemocompatibility assessment of an innovative material for blood contacting surfaces.

Over the years, several devices have been created (and the development of many others is currently in progress) to be in permanent contact with blood: mechanical circulatory supports represent an example thereof. The hemocompatibility of these devices largely depends on the chemical composition of blood-contacting components. In the present work, an innovative material (hybrid membrane) is proposed to fabricate the inner surfaces of a pulsatile ventricular chamber: it has been obtained by coupling a synthetic polymer (e.g., commercial polycarbonate urethane) with decellularized porcine pericardium. The hemocompatibility of the innovative material has been preliminarily assessed by measuring its capacity to promote thrombin generation and induce platelet activation. Our results demonstrated the blood compatibility of the proposed hybrid membrane.

Feasibility study of oxidized hyaluronic acid cross-linking acellular bovine pericardium with potential application for abdominal wall repair.

Bovine pericardium(BP)is one of the biological membranes with extensive application in tissue engineering. To fully investigate the potential clinical applications of this natural biological material, a suitable cross-linking reagent is hopefully adopted for modification. Glutaraldehyde (GA) is a clinically most common synthetic cross-linking reagent. In the study, oxidized hyaluronic acid (AHA) was developed to substitute GA to fix acellular bovine pericardium (ABP) for lower cytotoxicity, aiming to evaluate the feasibility of AHA as a cross-linking reagent and develop AHA-fixed ABP as a biological patch for abdominal wall repair. The AHA with the feeding ratio (1.8:1.0) has an appropriate molecular weight and oxidation degree, almost no cytotoxicity and good cross-linking effect. The critical cross-linking characteristics and cytocompatibility of AHA-fixed ABP were also investigated. The results demonstrated that 2.0% AHA-fixed ABP had the most suitable mechanical properties, thermal stability, resistance to enzymatic degradation and hydrophilicity. Moreover, 2.0% AHA-fixed samples exhibited an excellent cytocompatibility with human peritoneal mesothelial cells (HPMC) and low antigenicity. It also showed a prominent anti-calcification ability required for abdominal wall repair. Our data provided experimental basis for future research on AHA as a new cross-linking reagent and AHA-fixed ABP for abdominal wall repair.

A bioprosthetic heart valve cross-linked by a non-glutaraldehyde reagent with improved biocompatibility, endothelialization, anti-coagulation and anti-calcification properties.

Valvular heart disease is an important disease that endangers human health and heart valve replacement has become one of the main treatments for patients with severe valvular heart disease. However, the traditional surgical valve replacement (SVR) suffers several drawbacks such as high risk, great trauma and long recovery time, and more than 30% of patients are intolerant to SVR, especially elderly patients. In recent years, with the development of minimally invasive technology, transcatheter heart valve replacement (THVR) as a method of implantation without thoracotomy has become an optimal treatment for severe valvular heart disease due to its advantages of minimal trauma, low risk and fast recovery. Meanwhile, the usage of bioprosthetic heart valves (BHVs) has been enlarged greatly with the rapid development of THVR and the aging population. Most BHVs in clinics are crosslinked by glutaraldehyde (Glut), which shows great mechanical properties and chemical stability. However, some problems such as poor biocompatibility, calcification, coagulation and endothelialization difficulty also need to be solved urgently for Glut-treated BHVs. In this work, a non-Glut treated BHV from 7a-ethyltetrahydro-oxazolo[3,4-c]oxazole (OX-Et) crosslinked porcine pericardium (PP) has been developed. Compared with glutaraldehyde-crosslinked porcine pericardium (Glut-PP), good physical and chemical properties similar to Glut-PP are shown for OX-Et treated porcine pericardium (OX-Et-PP). It is noteworthy that better biocompatibility, endothelialization performance, and anti-coagulant effect as well as the improved anti-calcification property can also be observed for OX-Et-PP in the in vitro and in vivo study, potentially making OX-Et-PP a good candidate in the application of BHVs.

A combination of hydrogen bonding and chemical covalent crosslinking to fabricate a novel swim-bladder-derived dry heart valve material yields advantageous mechanical and biological properties.

The current biological valve products used in transcatheter aortic valve replacement (TAVR) are mainly made of glutaraldehyde (GLUT)-crosslinked porcine and bovine pericardia, which need to be transported and stored in GLUT solution. This leads to prolonged preparation time and the presence of GLUT residue. Therefore, there has been interest in developing TAVR valves using a pre-crimped valve (also known as a dry valve). Herein, a natural, inexpensive, and widely available swim bladder was selected as the source of a biological valve functioning as a dry valve and was obtained via acellular processes and crosslinking fixation. With the help of multiple hydrogen bonds between polyphenols (represented by procyanidin and curcumin) and tissue, as well as the chemical crosslinking of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) with tissue, we found that this novel combined crosslinking method was able to successfully crosslink with an acellular swim bladder. The stabilities, mechanical properties, resistance to pre-folding/pre-compressing, flattening capability in water, hemocompatibility, cytocompatibility, and anti-calcification capability were systematically measured via a series of experiments. We demonstrated that this dry valve resulting from a combination of EDC/polyphenols exhibited superior properties compared with those of a control pericardial-based valve.

Pericardial Mitochondrial DNA Levels Are Associated With Atrial Fibrillation After Cardiac Surgery.

BACKGROUND: Postoperative atrial fibrillation (POAF) is the most common complication after cardiac surgery, and is associated with increased morbidity and mortality. Inflammation has been implicated as an etiology of POAF. Mitochondrial DNA (mtDNA) has been shown to initiate inflammation. This study analyzed inflammatory mechanisms of POAF by evaluating mtDNA, neutrophils, and cytokines/chemokines in the pericardial fluid and blood after cardiac surgery. METHODS: Blood and pericardial fluid from patients who underwent coronary artery bypass or heart valve surgery, or both, were collected intraoperatively and at 4, 12, 24, and 48 hours postoperatively. Real-time polymerase chain reaction was used to quantify mtDNA in the pericardial fluid and blood. A Luminex (Luminex Corp, Austin, TX) assay was used to study cytokine and chemokine levels. Flow cytometry was used to analyze neutrophil infiltration and activation in the pericardial fluid. RESULTS: Samples from 100 patients were available for analysis. Postoperatively, mtDNA and multiple cytokine levels were higher in the pericardial fluid versus blood. Patients who had POAF had significantly higher levels of mtDNA in the pericardial fluid compared with patients who did not (P < .001, area under the curve 0.74). There was no difference in the mtDNA concentration in the blood between the POAF group and non-POAF group (P = .897). Neutrophil concentration increased in the pericardial fluid over time from a baseline of 0.8% to 56% at 48 hours (P < .01). CONCLUSIONS: The pericardial space has a high concentration of inflammatory mediators postoperatively. Mitochondrial DNA in the pericardial fluid was strongly associated with the development of POAF. This finding provides insight into a possible mechanism of inflammation that may contribute to POAF, and may offer novel therapeutic targets.

Evaluating the effects of vacuum on the microstructure and biocompatibility of bovine decellularized pericardium.

The aim of this study was evaluating the effects of vacuum on microstructure and biocompatibility of bovine decellularized pericardium. So the bovine pericardia were decellularized and then the vacuum was applied for two periods of time; 90 and 180 min. DNA, glucose amino glycan, collagen and elastin content assay, scanning electron microscopy (SEM) examination, hematoxylin and eosin (H&E) and Masson's trichrome stainings performed to evaluate microstructure of tissues. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, subcutaneous implantation, and tensile test were used to assay biocompatibility and mechanical properties of decellularized tissues. The results showed that applying vacuum reduced residual DNA significantly. Vacuum after 180 min reduced more residual DNA. There were no significant differences in the content of glucose amino glycan (GAG), collagen, and elastin between the vacuumed and control groups. SEM examination was revealed that vacuum for 180 min increased pore size and porosity more than 90 min and control groups. H&E and Masson's trichrome stainings revealed extracellular matrix preservation after decellularization in all groups. Cell viability was increased in vacuumed samples significantly after 72 h in vaccumed samples. H&E staining and tensile test after implantation of tissues were showed less inflammation in the vacuum applied tissues and increased durability. The vacuum increased DNA removal, pore size, porosity, and biocompatibility in vitro and in vivo and durability of bovine decellularized pericardium in vivo. Considering the important role of time, more studies should be performed to optimize time, intensity, and method of application of vacuum in decellularization of different tissues as well as bovine pericardium.

FLIm and Raman Spectroscopy for Investigating Biochemical Changes of Bovine Pericardium upon Genipin Cross-Linking.

Biomaterials used in tissue engineering and regenerative medicine applications benefit from longitudinal monitoring in a non-destructive manner. Label-free imaging based on fluorescence lifetime imaging (FLIm) and Raman spectroscopy were used to monitor the degree of genipin (GE) cross-linking of antigen-removed bovine pericardium (ARBP) at three incubation time points (0.5, 1.0, and 2.5 h). Fluorescence lifetime decreased and the emission spectrum redshifted compared to that of uncross-linked ARBP. The Raman signature of GE-ARBP was resonance-enhanced due to the GE cross-linker that generated new Raman bands at 1165, 1326, 1350, 1380, 1402, 1470, 1506, 1535, 1574, 1630, 1728, and 1741 cm-1. These were validated through density functional theory calculations as cross-linker-specific bands. A multivariate multiple regression model was developed to enhance the biochemical specificity of FLIm parameters fluorescence intensity ratio (R2 = 0.92) and lifetime (R2 = 0.94)) with Raman spectral results. FLIm and Raman spectroscopy detected biochemical changes occurring in the collagenous tissue during the cross-linking process that were characterized by the formation of a blue pigment which affected the tissue fluorescence and scattering properties. In conclusion, FLIm parameters and Raman spectroscopy were used to monitor the degree of cross-linking non-destructively.

Collagen membranes of dermal and pericardial origin-In vivo evolvement of vascularization over time.

Aim of the study was to compare the evolvement of vascularization over time of collagen membranes (CMs) of dermal and pericardial origin in an in vivo animal study. Twenty-eight mice underwent implantation of three commercially available CM derived from porcine dermis (homogenous structure: CM1 (Control 1) and bilayer structure: CM2 [Control 2]), from porcine pericardium (CM3; Test 1) as well as CM3 sprayed with silica-enhanced nanostructured hydroxyapatite (CM4, Test 2). After 3, 6, 9, and 12 days, intravital fluorescence microscopy was conducted for determination of capillary diameter, density, flow, and length. At Day 12, samples were examined immunohistologically for expression of fibroblast growth factor receptor 4 (FGFR4), CD11b, CD68, αSMA, and CD34. In all CM, intravital fluorescence microscopy over time showed increasing values for all parameters with the highest levels in CM4 and the lowest values in CM1. Significant lower amounts of FGFR4, CD11b, and CD68 were detected in CM4 when compared to CM2 (p < .05). In contrast to CM3, lower values of αSMA and higher numbers of CD34 positive-marked vessels were observed in CM4 (p < .05). In conclusion, dermal bilayer as well as pericardial CM seem to have a higher vascularization rate than dermal homogenous CM. Additional coating of pericardial CM with a silica-enhanced hydroxyapatite increases the speed of vascularization as well as biological remodeling processes.

Pre-mounted dry TAVI valve with improved endothelialization potential using REDV-loaded PEGMA hydrogel hybrid pericardium.

The pre-mounted dry transcatheter aortic valve implantation (TAVI) valve is a new technology in the development of biological heart valves. Dry valves do not need to be placed in special preservation solution and can be opened and used immediately, meeting the needs of clinical emergency valve implantation. However, current biological valves obtained by simple air drying cannot be unfolded quickly. In addition, the crimping process leads to structural damage to the valve fiber microstructure, reducing the service life of biological valves. Furthermore, current biological valves still have problems such as calcification, endothelialization difficulty, and immune rejection. In this study, a poly(ethylene glycol)methacrylate (PEGMA) hydrogel hybrid pericardium loaded with REDV was developed. The PEGMA monomer solution can penetrate the space of the pericardium. REDV was loaded into the PEGMA hydrogel, which was hybridized with pericardium via in situ polymerization. The results showed improved unfolding properties, less mechanical damage after crimping, and improved endothelialization potential of the biological valve. Thus, REDV-loaded PEGMA hydrogel hybrid pericardium is a promising approach for obtaining pre-mounted dry TAVI valves with enhanced endothelialization properties.

A Comprehensive Comparison of Bovine and Porcine Decellularized Pericardia: New Insights for Surgical Applications.

Xenogeneic pericardium-based substitutes are employed for several surgical indications after chemical shielding, limiting their biocompatibility and therapeutic durability. Adverse responses to these replacements might be prevented by tissue decellularization, ideally removing cells and preserving the original extracellular matrix (ECM). The aim of this study was to compare the mostly applied pericardia in clinics, i.e. bovine and porcine tissues, after their decellularization, and obtain new insights for their possible surgical use. Bovine and porcine pericardia were submitted to TRICOL decellularization, based on osmotic shock, detergents and nuclease treatment. TRICOL procedure resulted in being effective in cell removal and preservation of ECM architecture of both species' scaffolds. Collagen and elastin were retained but glycosaminoglycans were reduced, significantly for bovine scaffolds. Tissue hydration was varied by decellularization, with a rise for bovine pericardia and a decrease for porcine ones. TRICOL significantly increased porcine pericardial thickness, while a non-significant reduction was observed for the bovine counterpart. The protein secondary structure and thermal denaturation profile of both species' scaffolds were unaltered. Both pericardial tissues showed augmented biomechanical compliance after decellularization. The ECM bioactivity of bovine and porcine pericardia was unaffected by decellularization, sustaining viability and proliferation of human mesenchymal stem cells and endothelial cells. In conclusion, decellularized bovine and porcine pericardia demonstrate possessing the characteristics that are suitable for the creation of novel scaffolds for reconstruction or replacement: differences in water content, thickness and glycosaminoglycans might influence some of their biomechanical properties and, hence, their indication for surgical use.

Comparison of tensile properties of xenopericardium from three animal species and finite element analysis for bioprosthetic heart valve tissue.

Bioprosthetic heart valves still have poor long-term durability due to calcification and mechanical failure. The function and performance of bioprostheses is known to depend on the collagen architecture and mechanical behavior of the target tissue. So it is necessary to select an appropriate tissue for such prostheses. In this study, porcine, equine, and bovine pericardia were compared histologically and mechanically. The specimens were analyzed under light microscopy. The planar biaxial tests were performed on the tissue samples by applying synchronic loads along the axial (fiber direction) and perpendicular directions. The measured biaxial data were then fitted into both the modified Mooney-Rivlin model and the anisotropic four parameter Fung-type model. The modified Mooney-Rivlin model was applied to the modeling of the bovine, equine, and porcine pericardia using finite element analysis. The equine pericardium illustrated a wavy collagen bundle architecture similar to bovine pericardium, whereas the collagen bundles in the porcine pericardium were thinner and structured. Wavy pericardia may be preferable candidates for transcutaneous aortic valves because they are less likely to be delaminated during crimping. Based on the biaxial tensile test, the specimens indicated some degree of anisotropy; the anisotropy rates of the equine specimens were almost identical, and higher than the other two specimens. In general, porcine pericardium appeared stiffer, based on the greater strain energy magnitude and the average slope of the stress-stretch curves. Moreover, it was less distensible (due to lower areal strain) than the other two pericardial tissues. Furthermore, the porcine model induced localized high stress regions during the systolic and diastolic phases of the cardiac cycle. However, increased mechanical stress on the bioprosthetic leaflets may cause tissue degeneration and reduce the long-term durability of the valve. Based on our observations, the pericardial specimens behaved as anisotropic and nonlinear tissues-well-characterized by both the modified Mooney-Rivlin and the Fung-type models. The results indicate that, compared to bovine pericardium, equine tissue is mechanically and histologically more appropriate for manufacturing heart valve prostheses. The results of this study can be used in the design and manufacture of bioprosthetic heart valves.

Swim Bladder as a Novel Biomaterial for Cardiovascular Materials with Anti-Calcification Properties.

Calcification is a major cause of cardiovascular materials failure and deterioration, which leads to the restriction of their wide application. To develop new materials with anti-calcification capability is an urgent clinical requirement. Herein, a natural material derived from swim bladders as one promising candidate is introduced, which is prepared by decellularization and glutaraldehyde (GA) crosslinking. Data show that the swim bladder is mainly composed of collagen I, glycosaminoglycan (GAG), and elastin, especially rich in elastin, in accordance with higher elastic modulus in comparison to bovine pericardium. Moreover, the calcification of this material is proved dramatically lower than that of bovine pericardium by in vitro calcification assessments and in vivo assay using a rat subcutaneous implantation model. Meanwhile, good cytocompatibility, hemocompatibility, and enzymatic stability are demonstrated by in vitro assays. Further, a small diameter vascular graft using this material is successfully developed by rolling method and in situ implantation assay using a rat abdominal artery replacement model shows great performances in the aspect of higher patency and lower calcification. Taken together, these superior properties of swim bladder-derived material in anti-calcification, proper mechanical strength and stability, and excellent hemocompatibility and cytocompatibility endow it a great candidate as cardiovascular biomaterials.