Histomorphological evaluation of acellularized bovine pericardium in breast implant coverage.

Bovine pericardium (BP) has been used as a biomaterial for several decades in many medical applications particularly due to its mechanical properties and the high collagen content. In the acellular form it favors faster tissue repair, providing a three-dimensional support for cellular and vascular events observed during tissue repair and due, to a low elastin content, may favor its use as a breast implant cover, resulting in a low possibility of contracture of the biomaterial, preventing the appearance of irregularities during the reconstruction process. Thus, the aim of this study was to evaluate, histomorphologically, the behavior of acellularized bovine pericardium (ABP) as a mammary implant cover in rats. For this purpose, 16 animals were divided into two groups, with eight animals at each biological point: 7 and 15 days after surgery. Of the 16 animals, 32 specimens were obtained: 16 in the experimental group (EG) and 16 in the control group (CG). Throughout this study, none of the studied groups had postoperative complications. Results: The histomorphological results showed, in the two biological points, both in the EG and in the CG, chronic inflammatory infiltrate, leukocyte fibrin exudate, formation of granulation tissue and deposition of collagen fibers, more evident in the EG, regressive along the biological points. At 15 days, the implanted ABP showed initial biointegration with the fibrous capsule and surrounding tissues of the recipient bed. Conclusion: These results indicate that the due to the observed favorable tissue response ABP may be of potential use as a breast implant cover.

Comparison on the properties of bovine pericardium and porcine pericardium used as leaflet materials of transcatheter heart valve.

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.

Single-cell transcriptomics defines heterogeneity of epicardial cells and fibroblasts within the infarcted murine heart.

In the adult heart, the epicardium becomes activated after injury, contributing to cardiac healing by secretion of paracrine factors. Here, we analyzed by single-cell RNA sequencing combined with RNA in situ hybridization and lineage tracing of Wilms tumor protein 1-positive (WT1+) cells, the cellular composition, location, and hierarchy of epicardial stromal cells (EpiSC) in comparison to activated myocardial fibroblasts/stromal cells in infarcted mouse hearts. We identified 11 transcriptionally distinct EpiSC populations, which can be classified into three groups, each containing a cluster of proliferating cells. Two groups expressed cardiac specification markers and sarcomeric proteins suggestive of cardiomyogenic potential. Transcripts of hypoxia-inducible factor (HIF)-1α and HIF-responsive genes were enriched in EpiSC consistent with an epicardial hypoxic niche. Expression of paracrine factors was not limited to WT1+ cells but was a general feature of activated cardiac stromal cells. Our findings provide the cellular framework by which myocardial ischemia may trigger in EpiSC the formation of cardioprotective/regenerative responses.

Impact on Mechanical Properties of 10 versus 20 Minute Treatment of Human Pericardium with Glutaraldehyde in OZAKI Procedure.

PURPOSE: The aim of this study was to analyze the effects of 10-minute (standard term) versus 20-minute treatment with glutaraldehyde (GA) on mechanical stability and physical strength of human pericardium in the setting of the OZAKI procedure. METHODS: Leftover pericardium (6 patients) was bisected directly after the operation, and one-half was further fixed for 10 additional minutes. Uniaxial tensile tests were performed and ultimate tensile strength (UTS), ultimate tensile strain (uts), and collagen elastic modulus were evaluated. RESULTS: Both treatments resulted in similar values of uniaxial stretching-generated elongations at rupture (10 minutes 25 ± 7 % vs. 20 minutes: 22 ± 5 %; p = 0.05), UTS (5.16 ± 2 MPa vs. 6.54 ± 3 MPa; p = 0.59), and collagen fiber stiffness (elastic modulus: 31.80 ± 15.05 MPa vs. 37.35 ± 15.78 MPa; p = 0.25). CONCLUSION: Prolongation of the fixation time of autologous pericardium has no significant effect on its mechanical stability; thus, extending the intraoperative treatment cannot be recommended.

Cell Sheet Comprised of Mesenchymal Stromal Cells Overexpressing Stem Cell Factor Promotes Epicardium Activation and Heart Function Improvement in a Rat Model of Myocardium Infarction.

Cell therapy of the post-infarcted myocardium is still far from clinical use. Poor survival of transplanted cells, insufficient regeneration, and replacement of the damaged tissue limit the potential of currently available cell-based techniques. In this study, we generated a multilayered construct from adipose-derived mesenchymal stromal cells (MSCs) modified to secrete stem cell factor, SCF. In a rat model of myocardium infarction, we show that transplantation of SCF producing cell sheet induced activation of the epicardium and promoted the accumulation of c-kit positive cells in ischemic muscle. Morphometry showed the reduction of infarct size (16%) and a left ventricle expansion index (0.12) in the treatment group compared to controls (24-28%; 0.17-0.32). The ratio of viable myocardium was more than 1.5-fold higher, reaching 49% compared to the control (28%) or unmodified cell sheet group (30%). Finally, by day 30 after myocardium infarction, SCF-producing cell sheet transplantation increased left ventricle ejection fraction from 37% in the control sham-operated group to 53%. Our results suggest that, combining the genetic modification of MSCs and their assembly into a multilayered construct, we can provide prolonged pleiotropic effects to the damaged heart, induce endogenous regenerative processes, and improve cardiac function.

Cardiac motion non-influential in percutaneous computed tomography-guided biopsies of small (≤ 20 mm) lung nodules near pericardium.

PURPOSE: To assess the impact of cardiac motion during percutaneous computed tomography (CT)-guided core needle biopsy (PCT-CNB) of small lung lesions near pericardium, focusing on safety and diagnostic accuracy. MATERIALS AND METHODS: Seventy-eight PCT-CNBs were performed between March 2010 and June 2018 in 78 patients with small (≤ 20 mm) lung nodules, each within 10 mm of pericardium. Shifts in distance and length of interface separating lesions from pericardium were calculated and compared by cardiac chambers (left atrium, left ventricle, right atrium, or right ventricle). Risk factors for complications were subjected to univariate analysis, and diagnostic accuracy was assessed. RESULTS: The respective mean values were 0.8 ± 1.1 mm (range 0-5.1 mm) for shifts in distance and 1.5 ± 2.1 mm (range 0-10.8 mm) for length of interface. Neither parameter shifted significantly with respect to cardiac chambers (p > 0.05, both). Pneumothorax ensued in 28 patients (35.9%), and pulmonary hemorrhage occurred in 41 (52.6%). The overall sensitivity, specificity, and accuracy of PCT-CNB were 91.2%, 100%, and 93.2%, respectively. CONCLUSION: Our data indicate that cardiac motion has no impact on either the incidence of complications or the diagnostic accuracy of PCT-CNB in patients with small (≤ 20 mm) lung lesions near pericardium.

Fabrication of porous bovine pericardium scaffolds incorporated with bFGF for tissue engineering applications.

BACKGROUND: The design and fabrication of porous scaffolds are important issues for tissue engineering applications. In this study, we attempted to fabricate porous scaffolds using bovine pericardium (BP) and examined whether these scaffolds were beneficial for cell ingrowth and bioactive factors delivery. METHODS: A vacuum-freeze-thawing-Triton X-100 (VFTT) protocol was used to fabricate porous BP scaffolds. The porous and mechanical properties were assessed using histology, scanning electron microscopy, and mechanical assay. The fabricated scaffolds were seeded with mesenchymal stem cells (MSCs), and cell ingrowth was evaluated. Basic fibroblast growth factor (bFGF) was subsequently incorporated into the fabricated scaffolds. The bioactive factor delivery capacity was evaluated using loading and release studies. The bioactivity of released bFGF was assessed using a rat subcutaneous model. RESULTS: The BP scaffolds fabricated by the VFTT protocol displayed interconnected porous structures with porosity of 6.82 ± 1.36%.There were no significant differences in thickness, ultimate load, Young's modulus, and ultimate tensile strength between the fabricated porous BP scaffolds and native BPs (all P > .05). However, the water content of BPs was slightly reduced after VFTT treatment (P < .05). Cell ingrowth analysis showed that the seeded MSCs penetrated into the porous BP scaffolds with time of culture, while MSCs were limited to the surface layers of native BPs. Furthermore, bFGF was observed to be effectively loaded onto and released from the porous BP scaffolds. The released bFGF increased the phosphorylation levels of Akt, ERK 1/2, and MEK1/2, promoted host MSC recruitment, and inhibited myofibroblast differentiation in vivo. CONCLUSIONS: The porous BP scaffolds fabricated using a VFTT protocol were promising natural scaffolds for tissue engineering applications, since they had considerable mechanical properties as native BPs, supplied porous channels for cell ingrowth, and possessed bioactive factors delivery capability.

Coronary Revascularization During Heart Regeneration Is Regulated by Epicardial and Endocardial Cues and Forms a Scaffold for Cardiomyocyte Repopulation.

Defective coronary network function and insufficient blood supply are both cause and consequence of myocardial infarction. Efficient revascularization after infarction is essential to support tissue repair and function. Zebrafish hearts exhibit a remarkable ability to regenerate, and coronary revascularization initiates within hours of injury, but how this process is regulated remains unknown. Here, we show that revascularization requires a coordinated multi-tissue response culminating with the formation of a complex vascular network available as a scaffold for cardiomyocyte repopulation. During a process we term "coronary-endocardial anchoring," new coronaries respond by sprouting (1) superficially within the regenerating epicardium and (2) intra-ventricularly toward the activated endocardium. Mechanistically, superficial revascularization is guided by epicardial Cxcl12-Cxcr4 signaling and intra-ventricular sprouting by endocardial Vegfa signaling. Our findings indicate that the injury-activated epicardium and endocardium support cardiomyocyte replenishment initially through the guidance of coronary sprouting. Simulating this process in the injured mammalian heart should help its healing.

Bovine pericardium membrane as new tool for mesenchymal stem cells commitment.

Acellular matrices are widespread biomaterials used in surgical practice as tissue reinforcement and anatomical support to favor tissue regeneration. It is clear that a fundamental role in the regeneration of tissue is played by cell-material interaction. In this work, the interaction between a bovine pericardium membrane and human adult stem cells was investigated by microscopy analysis and gene expression analysis. Parallel cell cultures were prepared on the pericardium membrane or tissue culture plate. They were incubated in basal growth medium or in adipogenic differentiation medium to perform experiments on the seventh and the 14th day of culture. Results demonstrated that the membrane allows cell viability, adhesion, and proliferation of human stem cells. During adipogenic commitment on the membrane, the accumulation of cytoplasmatic lipid droplets and the expression of adipogenic gene PPARG, CEBPA, GLUT4, FABP4, and ADIPOQ were detected. Concurrently, a downregulation of mesenchymal stem cell gene CD29, CD90, and CD105 was detected. In basal medium, the adipogenic gene expression was upregulated, whereas the mesenchymal markers were indifferently expressed. These findings suggest that the bovine pericardium membrane is a biocompatible matrix and that their rough surface allows cell adhesion, spreading, and proliferation. The surface morphology activates mechanochemical signals that stimulate the adipogenic commitment of stem cells in basal medium and potentiate their commitment in adipogenic differentiation medium.

Assessment of cytocompatibility and mechanical properties of detergent-decellularized ovine pericardial tissue.

BACKGROUND: Autologous pericardium is widely used for the repair of different sized cardiovascular defects. However, its use is limited especially in redo cardiac surgery. We developed an engineered tissue based on decellularized pericardium reseeded with blood-derived endothelial cells. MATERIALS AND METHODS: Decellularization of ovine pericardium was performed using detergent treatment. Ovine outgrowth blood-derived and green fluorescent protein-labeled endothelial cells were used to reseed the decellularized ovine pericardium on the mesothelial side. The cell adhesion was assessed using fluorescent microscopy up to 15 days of in vitro cultivation. The mechanical properties of the pericardium were evaluated using suturability, burst pressure, and suture retention strength tests. RESULTS: After decellularization the pericardial sheets appeared cell-free and repopulation using ovine blood-derived endothelial cells was successful by forming a robust monolayer. Detergent treatment did not affect the extracellular matrix. The thickness of decellularized tissue was similar to native ovine pericardium (285.3 ± 28.2 µm, respective 276.9 ± 23.8 µm, p = 0.48). Decellularized patch showed similar suturability comparable to the native ovine pericardium. Resulted burst pressure was not significantly different (native/decellularized: 312.5 ± 13.6/304.2 ± 16, p = 0.35). The suture retention strength of native pericardium was 638.33 ± 90.2 gr and comparable to decellularized tissue (622.2 ± 89.9 gr, p = 0.76). No differences were observed concerning elongation of native and decellularized pericardium (8.33 ± 1.5 and 8.5 ± 0.84 mm, respectively; p = 0.82). CONCLUSION: Mesothelial surface of decellularized ovine pericardium is suitable for reseeding with ovine blood-derived endothelial cells. The mechanical properties of detergent-treated pericardium were comparable to native tissue.

Minor lipids profiling in subcutaneous and epicardial fat tissue using LC/MS with an optimized preanalytical phase.

Analysis of bioactive lipids in adipose tissue could lead to better understanding of the pathogenesis of obesity and its complications. However, current MS methods are limited by a high content of triacylglycerols (TAGs), which markedly surpasses the amount of other lipids and suppresses their ionization. The aim of our study was thus to optimize the preanalytical phase of lipid analysis in adipose tissue, focusing in particular on less-abundant lipids. Next, the optimized method was used to describe the differences between epicardial and subcutaneous adipose tissues obtained from patients undergoing cardiac surgery. Lipids were extracted using a modified Folch method with subsequent detachment of TAGs by thin layer chromatography (TLC). The extracts with/without TAGs were analyzed by tandem LC/MS. The repeatability of the presented method expressed by the median of the coefficients of variation was 12/5% for analysis with/without TAGs separation, respectively. The difference in the relative abundance of TAGs gained with/without TLC was, on average, 19% and did not reach significance (p value > 0.05) for any identified TAG. The novel preanalytical step allowed us to detect 37 lipids, which could not have been detected without TAG separation, because their signal to noise ratio is <5 in current methods of untargeted lipidomics. These lipids belong predominately to ceramides, glycerophosphatidylserines, glycerophosphatidylinsitols, sphingomyelins, glycerophosphatidylcholines, glycerophosphatidylethanolamines, diacylglycerols. The two adipose tissue depots differed mainly in the following lipid classes: glycerophosphatidylcholines, glycerophosphatidylinositols, glycerophosphatidylethanolamine, and sphingomyelins. Moreover, other major lipids showed distinctly different distributions between the two adipose tissues. Among these, the changes in TAGs were the most striking, which correspond to previously published data describing the differences between omental and subcutaneous adipose tissue. Implementation of the TLC step for the elimination of TAGs was crucial for enhancing the MS detection limit of minor lipids in adipose tissue. The differences between the overall lipid profiles of subcutaneous and epicardial tissue reflect their different functions arising from their location.

Pericardial application as a new route for implanting stem-cell cardiospheres to treat myocardial infarction.

KEY POINTS: Cardiospheres (CSps) are a promising new form of cardiac stem cells with advantage over other stem cells for myocardial regeneration, but direct implantation of CSps by conventional routes has been limited due to potential embolism. We have implanted CSps into the pericardial cavity and systematically demonstrated its efficacy regarding myocardial infarction. Stem cell potency and cell viability can be optimized in vitro prior to implantation by pre-conditioning CSps with pericardial fluid and hydrogel packing. Transplantation of optimized CSps into the pericardial cavity improved cardiac function and alleviated myocardial fibrosis, increased myocardial cell survival and promoted angiogenesis. Mechanistically, CSps are able to directly differentiate into cardiomyocytes in vivo and promote regeneration of myocardial cells and blood vessels through a paracrine effect with released growth factors as potential paracrine mediators. These findings establish a new strategy for therapeutic myocardial regeneration to treat myocardial infarction. ABSTRACT: Cardiospheres (CSps) are a new form of cardiac stem cells with an advantage over other stem cells for myocardial regeneration. However, direct implantation of CSps by conventional routes to treat myocardial infarction has been limited due to potential embolism. We have implanted CSps into the pericardial cavity and systematically assessed its efficacy on myocardial infarction. Preconditioning with pericardial fluid enhanced the activity of CSps and matrix hydrogel prolonged their viability. This shows that pretransplant optimization of stem cell potency and maintenance of cell viability can be achieved with CSps. Transplantation of optimized CSps into the pericardial cavity improved cardiac function and alleviated myocardial fibrosis in the non-infarcted area, and increased myocardial cell survival and promoted angiogenesis in the infarcted area. Mechanistically, CSps were able to directly differentiate into cardiomyocytes in vivo and promoted regeneration of myocardial cells and blood vessels in the infarcted area through a paracrine effect with released growth factors in pericardial cavity serving as possible paracrine mediators. This is the first demonstration of direct pericardial administration of pre-optimized CSps, and its effectiveness on myocardial infarction by functional and morphological outcomes with distinct mechanisms. These findings establish a new strategy for therapeutic myocardial regeneration to treat myocardial infarction.

Current status of intra-operative graft assessment: Should it be the standard of care for coronary artery bypass graft surgery?

The "Achilles heel" of coronary artery bypass graft (CABG) surgery is graft patency. While long-term patency is determined by the type of conduit and the progression of graft and native vessel disease, short-term patency is affected by intra-operative technical issues. Transit-time flow measurements and epicardial ultrasound have been shown to accurately assess intra-operative graft patency. This review will examine the evidence to support the premise that intra-operative graft assessment is essential in determining graft patency and should be the standard of care when performing CABG surgery.

A sterilization method for decellularized xenogeneic cardiovascular scaffolds.

Decellularized xenogeneic scaffolds have shown promise to be employed as compatible and functional cardiovascular biomaterials. However, one of the main barriers to their clinical exploitation is the lack of appropriate sterilization procedures. This study investigated the efficiency of a two-step sterilization method, antibiotics/antimycotic (AA) cocktail and peracetic acid (PAA), on porcine and bovine decellularized pericardium. In order to assess the efficiency of the method, a sterilization assessment protocol was specifically designed, comprising: i) controlled contamination with a known amount of bacteria; ii) sterility test; iii) identification of contaminants through MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization Time-of-Flight) mass spectrometry and iv) quantification by the Most Probable Number (MPN) method. This sterilization assessment protocol proved to be a successful tool to monitor and optimize the proposed sterilization method. The treatment with AA + PAA method provided sterile scaffolds while preserving the structural integrity and biocompatibility of the decellularized porcine and bovine tissues. However, surface properties and cellular adhesion resulted slightly impaired on porcine pericardium. This work developed a sterilization method suitable for decellularized pericardial scaffolds that could be adopted for in vivo tissue engineering. Together with the proposed sterilization assessment protocol, this decontamination method will foster the clinical translation of decellularized xenogeneic substitutes. STATEMENT OF SIGNIFICANCE: Clinical application of functional and compatible xenogeneic decellularized scaffolds has been delayed due to the lack of appropriate sterilization methodologies. In this study, it was investigated an effective sterilization method optimized for porcine and bovine decellularized pericardia, based on the use of antibiotics/antimycotics followed by peracetic acid treatment. This treatment effectively sterilizes both species scaffolds, proves to maintain tissue overall structure and components, preserves biocompatibility and biomechanical properties. Furthermore, it was also developed a sterilization assessment protocol used to monitor and validate the previous method, consisting in three main parts: i) controlled contamination; ii) sterility test, and iii) identification and quantification of contaminants. Both methodologies were optimized for the tissues in study but can be applied to other scaffolds and accelerate their clinical translation.

Traumatic leaflet injury: comparison of porcine leaflet self-expandable and bovine leaflet balloon-expandable prostheses.

OBJECTIVES: The main goal of this study was to compare the occurrence of post-deployment leaflet injury between prostheses made of porcine and bovine pericardium. METHODS: Two types of prostheses, self-expandable prostheses with porcine pericardial leaflet on one side and balloon-expandable prostheses with bovine pericardial leaflet on the other side, were used. In each group, crimped prostheses were compared with control non-crimped prostheses. Following a 15-min period of crimping, prostheses were deployed, and their leaflets were removed and subjected to analyses. The analyses included determination of global and local hydraulic conductance of the leaflets, leaflet plasma insudation and microscopic analysis. The results were expressed as percentage (standard error of the mean) or median (interquartile range). RESULTS: A significant increase in the global hydraulic conductance was only observed in the crimped balloon-expandable prostheses: 20.1 (15.5-41.2) ml/h/m2/mmHg vs 12.3 (9.0-15.6) ml/h/m2/mmHg (P = 0.021). Similarly, areas of marked staining (a marker of local hydraulic conductance) were only seen in the bovine pericardium balloon-expandable prostheses. The incidence of leaflet plasmatic insudation was increased in the crimped prostheses compared with the control prostheses. The microscopic study revealed a higher occurrence of traumatic lesions in the crimped prostheses in comparison with the control prostheses: 33.3 ± 21.1% vs 5.5 ± 5.5% (P = 0.039) and 44.4 ± 20.5% vs 5.5 ± 5.5% (P = 0.017) in the bovine and the porcine leaflets, respectively. CONCLUSIONS: Post-deployment leaflet injury occurred in both types of prostheses. However, alteration of the global and local hydraulic conductance was important in the bovine pericardium balloon-expandable prostheses.

The epicardium as a source of multipotent adult cardiac progenitor cells: Their origin, role and fate.

Since the regenerative capacity of the adult mammalian heart is limited, cardiac injury leads to the formation of scar tissue and thereby increases the risk of developing compensatory heart failure. Stem cell therapy is a promising therapeutic approach but is facing problems with engraftment and clinical feasibility. Targeting an endogenous stem cell population could circumvent these limitations. The epicardium, a membranous layer covering the outside of the myocardium, is an accessible cell population which plays a key role in the developing heart. Epicardial cells undergo epithelial to mesenchymal transition (EMT), thus providing epicardial derived cells (EPDCs) that migrate into the myocardium and cooperate in myocardial vascularisation and compaction. In the adult heart, injury activates the epicardium, and an embryonic-like response is observed which includes EMT and differentiation of the EPDCs into cardiac cell types. Furthermore, paracrine communication between the epicardium and myocardium improves the regenerative response. The significant role of the epicardium has been shown in both the developing and the regenerating heart. Interestingly, the epicardial contribution to cardiac repair can be improved in several ways. In this review, an overview of the epicardial origin and fate will be given and potential therapeutic approaches will be discussed.

Anatomy and Physiology of the Pericardium.

The pericardium consists of a visceral mesothelial monolayer (epicardium) that reflects over the great vessels and joins an outer, relatively inelastic fibrous parietal layer of organized collagen and elastin fibers, between which is a potential space that normally contains up to 50 mL of plasma filtrate. Although not essential for life, the pericardium serves important albeit subtle functions in the euvolemic healthy individual that become increasingly important in hypervolemic states and conditions in which the heart enlarges acutely. The pericardial functions can be divided into the mechanical, reflex, membranous, metabolic, ligamentous.

Histological and biomechanical characterization of decellularized porcine pericardium as a potential scaffold for tissue engineering applications.

BACKGROUND: Each year, more than 800,000 vascular and cardiac surgeries are performed therefore, there is a great need for suitable material for bioprosthetic operations. Porcine pericardium is a double-walled sac that covers the heart and can be used in vascular and cardiac thoracic surgery. OBJECTIVE: The aim of the present study was to evaluate the decellularization process and biomechanical properties in porcine pericardial tissue after the decellularization treatment. METHODS: A detergent based protocol was used for the decellularization of porcine pericardium. Histological analysis and contact cytotoxicity assay were performed. Additionally, biomechanical testing and in vivo biocompatibility by implantation into Wistar Rats were performed. RESULTS: The histological analysis showed the preservation of the extracellular matrix, without any observable cellular remnants. No toxic effects were noticed when contact cytotoxicity assay performed. The decellularized tissues, after implantation in Wistar Rats, remained for up to 12 weeks without being rejected. Finally, the biomechanical testing showed no significant differences between native and decellularized tissues. CONCLUSION: In this study, the decellularization of the porcine pericardium produced a non toxic scaffold, free of any cellular remnants, thus serving as an alternative material for tissue engineering applications including heart valve and vascular patch development.

Tension Creates an Endoreplication Wavefront that Leads Regeneration of Epicardial Tissue.

Mechanisms that control cell-cycle dynamics during tissue regeneration require elucidation. Here we find in zebrafish that regeneration of the epicardium, the mesothelial covering of the heart, is mediated by two phenotypically distinct epicardial cell subpopulations. These include a front of large, multinucleate leader cells, trailed by follower cells that divide to produce small, mononucleate daughters. By using live imaging of cell-cycle dynamics, we show that leader cells form by spatiotemporally regulated endoreplication, caused primarily by cytokinesis failure. Leader cells display greater velocities and mechanical tension within the epicardial tissue sheet, and experimentally induced tension anisotropy stimulates ectopic endoreplication. Unbalancing epicardial cell-cycle dynamics with chemical modulators indicated autonomous regenerative capacity in both leader and follower cells, with leaders displaying an enhanced capacity for surface coverage. Our findings provide evidence that mechanical tension can regulate cell-cycle dynamics in regenerating tissue, stratifying the source cell features to improve repair.

Packaging of implantable accelerometers to monitor epicardial and endocardial wall motion.

Acceleration signals, collected from the inner and the outer heart wall, offer a mean of assessing cardiac function during surgery. Accelerometric measurements can also provide detailed insights into myocardial motion during exploratory investigations. Two different implantable accelerometers to respectively record endocardial and epicardial vibrations, have been developed by packaging a commercially available capacitive transducer. The same coating materials have been deposited on the two devices to ensure biocompatibility of the implants: Parylene-C, medical epoxy and Polydimethylsiloxane (PDMS). The different position-specific requirements resulted in two very dissimilar sensor assemblies. The endocardial accelerometer, that measures accelerations from the inner surface of the heart during acute animal tests, is a 2 mm-radius hemisphere fixed on a polymethyl methacrylate (PMMA) rod to be inserted through the heart wall. The epicardial accelerometer, that monitors the motion of the outer surface of the heart, is a three-legged structure with a stretchable polytetrafluoroethylene (PTFE) reinforcement. This device can follow the continuous motion of the myocardium (the muscular tissue of the heart) during the cardiac cycle, without hindering its natural movement. Leakage currents lower than 1 µA have been measured during two weeks of continuous operation in saline. Both transducers have been used, during animal tests, to simultaneously record and compare acceleration signals from corresponding locations on the inner and the outer heart wall of a female sheep.