Preservation strategies for decellularized pericardial scaffolds for off-the-shelf availability

Reconstruction of the human nipple-areolar complex: a tissue engineering approach

Introduction: Nipple-areolar complex (NAC) reconstruction after breast cancer surgery is challenging and does not always provide optimal long-term esthetic results. Therefore, generating a NAC using tissue engineering techniques, such as a decellularization-recellularization process, is an alternative option to recreate a specific 3D NAC morphological unit, which is then covered with an in vitro regenerated epidermis and, thereafter, skin-grafted on the reconstructed breast. Materials and methods: Human NACs were harvested from cadaveric donors and decellularized using sequential detergent baths. Cellular clearance and extracellular matrix (ECM) preservation were analyzed by histology, as well as by DNA, ECM proteins, growth factors, and residual sodium dodecyl sulfate (SDS) quantification. In vivo biocompatibility was evaluated 30 days after the subcutaneous implantation of native and decellularized human NACs in rats. In vitro scaffold cytocompatibility was assessed by static seeding of human fibroblasts on their hypodermal side for 7 days, while human keratinocytes were seeded on the scaffold epidermal side for 10 days by using the reconstructed human epidermis (RHE) technique to investigate the regeneration of a new epidermis. Results: The decellularized NAC showed a preserved 3D morphology and appeared white. After decellularization, a DNA reduction of 98.3% and the absence of nuclear and HLA staining in histological sections confirmed complete cellular clearance. The ECM architecture and main ECM proteins were preserved, associated with the detection and decrease in growth factors, while a very low amount of residual SDS was detected after decellularization. The decellularized scaffolds were in vivo biocompatible, fully revascularized, and did not induce the production of rat anti-human antibodies after 30 days of subcutaneous implantation. Scaffold in vitro cytocompatibility was confirmed by the increasing proliferation of seeded human fibroblasts during 7 days of culture, associated with a high number of living cells and a similar viability compared to the control cells after 7 days of static culture. Moreover, the RHE technique allowed us to recreate a keratinized pluristratified epithelium after 10 days of culture. Conclusion: Tissue engineering allowed us to create an acellular and biocompatible NAC with a preserved morphology, microarchitecture, and matrix proteins while maintaining their cell growth potential and ability to regenerate the skin epidermis. Thus, tissue engineering could provide a novel alternative to personalized and natural NAC reconstruction.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Comparison of Bovine- and Porcine-Derived Decellularized Biomaterials: Promising Platforms for Tissue Engineering Applications

Animal-derived xenogeneic biomaterials utilized in different surgeries are promising for various applications in tissue engineering. However, tissue decellularization is necessary to attain a bioactive extracellular matrix (ECM) that can be safely transplanted. The main objective of the present study is to assess the structural integrity, biocompatibility, and potential use of various acellular biomaterials for tissue engineering applications. Hence, a bovine pericardium (BP), porcine pericardium (PP), and porcine tunica vaginalis (PTV) were decellularized using a Trypsin, Triton X (TX), and sodium dodecyl sulfate (SDS) (Trypsin + TX + SDS) protocol. The results reveal effective elimination of the cellular antigens with preservation of the ECM integrity confirmed via staining and electron microscopy. The elasticity of the decellularized PP (DPP) was markedly (p < 0.0001) increased. The tensile strength of DBP, and DPP was not affected after decellularization. All decellularized tissues were biocompatible with persistent growth of the adipose stem cells over 30 days. The staining confirmed cell adherence either to the peripheries of the materials or within their matrices. Moreover, the in vivo investigation confirmed the biocompatibility and degradability of the decellularized scaffolds. Conclusively, Trypsin + TX + SDS is a successful new protocol for tissue decellularization. Moreover, decellularized pericardia and tunica vaginalis are promising scaffolds for the engineering of different tissues with higher potential for the use of DPP in cardiovascular applications and DBP and DPTV in the reconstruction of higher-stress-bearing abdominal walls.

Influence of Storage Conditions on Decellularized Porcine Conjunctiva

Porcine decellularized conjunctiva (PDC) represents a promising alternative source for conjunctival reconstruction. Methods of its re-epithelialization in vitro with primary human conjunctival epithelial cells (HCEC) have already been established. However, a long-term storage method is required for a simplified clinical use of PDC. This study investigates the influence of several storage variants on PDC. PDC were stored in (1) phosphate-buffered saline solution (PBS) at 4 °C, (2) in glycerol-containing epithelial cell medium (EM/gly) at −80 °C and (3) in dimethyl sulfoxide-containing epithelial cell medium (EM/DMSO) at −196 °C in liquid nitrogen for two and six months, respectively. Fresh PDC served as control. Histological structure, biomechanical parameters, the content of collagen and elastin and the potential of re-epithelialization with primary HCEC under cultivation for 14 days were compared (n = 4–10). In all groups, PDC showed a well-preserved extracellular matrix without structural disruptions and with comparable fiber density (p ≥ 0.74). Collagen and elastin content were not significantly different between the groups (p ≥ 0.18; p ≥ 0.13, respectively). With the exception of the significantly reduced tensile strength of PDC after storage at −196 °C in EM/DMSO for six months (0.46 ± 0.21 MPa, p = 0.02), no differences were seen regarding the elastic modulus, tensile strength and extensibility compared to control (0.87 ± 0.25 MPa; p ≥ 0.06). The mean values of the epithelialized PDC surface ranged from 51.9 ± 8.8% (−196 °C) to 78.3 ± 4.4% (−80 °C) and did not differ significantly (p ≥ 0.35). In conclusion, all examined storage methods were suitable for storing PDC for at least six months. All PDC were able to re-epithelialize, which rules out cytotoxic influences of the storage conditions and suggests preserved biocompatibility for in vivo application.

In vitro evaluation of crosslinked bovine pericardium as potential scaffold for the oral cavity

BACKGROUND

Bovine pericardium (BP) is a scaffold widely used in soft tissues regeneration; however, its calcification in contact with glutaraldehyde, represent an opportunity for its application in hard tissues, such as bone in the oral cavity.

OBJECTIVE

To develop and to characterize decellularized and glutaraldehyde-crosslinked bovine pericardium (GC-BP) as a potential scaffold for guided bone regeneration GBR.

METHODS

BP samples from healthy animals of the bovine zebu breed were decellularized and crosslinked by digestion with detergents and glutaraldehyde respectively. The resulting cell-free scaffold was physical, chemical, mechanical, and biologically characterized thought hematoxylin and eosin staining, DNA quantification, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), uniaxial tensile test, cell viability and live and dead assay in cultures of dental pulp stem cells (DPSCs).

RESULTS

The decellularization and crosslinking of BP appeared to induce conformational changes of the CLG molecules, which led to lower mechanical properties at the GC-BP scaffold, at the same time that promoted cell adhesion and viability of DPSCs.

CONCLUSION

This study suggests that the decellularized and GC-BP is a scaffold with the potential to be used promoting DPSCs recruitment, which has a great impact on the dental area.

Decellularized rat submandibular gland as an alternative scaffold for dental pulp regeneration

Introduction: Decellularized extracellular matrix has been recognized as an optimal scaffold for dental pulp regeneration. However, the limited amount of native dental pulp tissue restricts its clinical applications. The submandibular gland shares some basic extracellular matrix components and characteristics with dental pulp. However, whether decellularized submandibular gland extracellular matrix (DSMG) can be used as an alternative scaffold for dental pulp regenerative medicine is unclear. Methods: Thus, we successfully decellularized the whole rat submandibular gland and human dental pulp, and then conducted in vitro and in vivo studies to compare the properties of these two scaffolds for dental pulp regeneration. Results: Our results showed that extracellular matrix of the submandibular gland had great similarities in structure and composition with that of dental pulp. Furthermore, it was confirmed that the DSMG could support adhesion and proliferation of dental pulp stem cells in vitro. In vivo findings revealed that implanted cell-seeded DSMG formed a vascularized dental pulp-like tissue and expressed markers involved in dentinogenesis and angiogenesis. Discussion: In summary, we introduced a novel accessible biological scaffold and validated its effectiveness as an extracellular matrix-based tissue engineering scaffold for dental pulp regenerative therapy.

Decellularized Extracellular Matrix Scaffolds for Cardiovascular Tissue Engineering: Current Techniques and Challenges

Cardiovascular diseases are the leading cause of global mortality. Over the past two decades, researchers have tried to provide novel solutions for end-stage heart failure to address cardiac transplantation hurdles such as donor organ shortage, chronic rejection, and life-long immunosuppression. Cardiac decellularized extracellular matrix (dECM) has been widely explored as a promising approach in tissue-regenerative medicine because of its remarkable similarity to the original tissue. Optimized decellularization protocols combining physical, chemical, and enzymatic agents have been developed to obtain the perfect balance between cell removal, ECM composition, and function maintenance. However, proper assessment of decellularized tissue composition is still needed before clinical translation. Recellularizing the acellular scaffold with organ-specific cells and evaluating the extent of cardiomyocyte repopulation is also challenging. This review aims to discuss the existing literature on decellularized cardiac scaffolds, especially on the advantages and methods of preparation, pointing out areas for improvement. Finally, an overview of the state of research regarding the application of cardiac dECM and future challenges in bioengineering a human heart suitable for transplantation is provided.

A New Detergent for the Effective Decellularization of Bovine and Porcine Pericardia

Human and animal pericardia are among the most widely exploited materials suitable to repair damaged tissues in the cardiovascular surgery context. Autologous, xenogeneic (chemically treated) and homologous pericardia are largely utilized, but they do exhibit some crucial drawbacks. Any tissue treated with glutaraldehyde is known to be prone to calcification in vivo, lacks regeneration potential, has limited durability, and can result in cytotoxicity. Moreover, autologous tissues have limited availability. Decellularized biological tissues represent a promising alternative: decellularization removes cellular and nuclear components from native tissues and makes them suitable for repopulation by autologous cells upon implantation into the body. The present work aims to assess the effects of a new detergent, i.e., Tergitol, for decellularizing bovine and porcine pericardia. The decellularization procedure successfully removed cells, while preserving the histoarchitecture of the extracellular matrix. No cytotoxic effect was observed. Therefore, decellularized pericardia showed potential to be used as scaffold for cardiovascular tissue regeneration.

Biomaterials for Regenerative Medicine in Italy: Brief State of the Art of the Principal Research Centers

Regenerative medicine is the branch of medicine that effectively uses stem cell therapy and tissue engineering strategies to guide the healing or replacement of damaged tissues or organs. A crucial element is undoubtedly the biomaterial that guides biological events to restore tissue continuity. The polymers, natural or synthetic, find wide application thanks to their great adaptability. In fact, they can be used as principal components, coatings or vehicles to functionalize several biomaterials. There are many leading centers for the research and development of biomaterials in Italy. The aim of this review is to provide an overview of the current state of the art on polymer research for regenerative medicine purposes. The last five years of scientific production of the main Italian research centers has been screened to analyze the current advancement in tissue engineering in order to highlight inputs for the development of novel biomaterials and strategies.

A Roadmap to Cardiac Tissue-Engineered Construct Preservation: Insights from Cells, Tissues, and Organs

Worldwide, over 26 million patients suffer from heart failure (HF). One strategy aspiring to prevent or even to reverse HF is based on the transplantation of cardiac tissue-engineered (cTE) constructs. These patient-specific constructs aim to closely resemble the native myocardium and, upon implantation on the diseased tissue, support and restore cardiac function, thereby preventing the development of HF. However, cTE constructs off-the-shelf availability in the clinical arena critically depends on the development of efficient preservation methodologies. Short- and long-term preservation of cTE constructs would enable transportation and direct availability. Herein, currently available methods, from normothermic- to hypothermic- to cryopreservation, for the preservation of cardiomyocytes, whole-heart, and regenerative materials are reviewed. A theoretical foundation and recommendations for future research on developing cTE construct specific preservation methods are provided. Current research suggests that vitrification can be a promising procedure to ensure long-term cryopreservation of cTE constructs, despite the need of high doses of cytotoxic cryoprotective agents. Instead, short-term cTE construct preservation can be achieved at normothermic or hypothermic temperatures by administration of protective additives. With further tuning of these promising methods, it is anticipated that cTE construct therapy can be brought one step closer to the patient.

Fourier transform infrared spectroscopy coupled with machine learning classification for identification of oxidative damage in freeze-dried heart valves

Freeze-drying can be used to ensure off-the-shelf availability of decellularized heart valves for cardiovascular surgery. In this study, decellularized porcine aortic heart valves were analyzed by nitroblue tetrazolium (NBT) staining and Fourier transform infrared spectroscopy (FTIR) to identify oxidative damage during freeze-drying and subsequent storage as well as after treatment with H₂O₂ and FeCl₃. NBT staining revealed that sucrose at a concentration of at least 40% (w/v) is needed to prevent oxidative damage during freeze-drying. Dried specimens that were stored at 4 °C depict little to no oxidative damage during storage for up to 2 months. FTIR analysis shows that fresh control, freeze-dried and stored heart valve specimens cannot be distinguished from one another, whereas H₂O₂- and FeCl₃-treated samples could be distinguished in some tissue section. A feed forward artificial neural network model could accurately classify H₂O₂ and FeCl₃ treated samples. However, fresh control, freeze-dried and stored samples could not be distinguished from one another, which implies that these groups are very similar in terms of their biomolecular fingerprints. Taken together, we conclude that sucrose can minimize oxidative damage caused by freeze-drying, and that subsequent dried storage has little effects on the overall biochemical composition of heart valve scaffolds.

Covalent functionalization of decellularized tissues accelerates endothelialization

In the field of tissue regeneration, the lack of a stable endothelial lining may affect the hemocompatibility of both synthetic and biological replacements. These drawbacks might be prevented by specific biomaterial functionalization to induce selective endothelial cell (EC) adhesion. Decellularized bovine pericardia and porcine aortas were selectively functionalized with a REDV tetrapeptide at 10⁻⁵ M and 10⁻⁶ M working concentrations. The scaffold-bound peptide was quantified and REDV potential EC adhesion enhancement was evaluated in vitro by static seeding of human umbilical vein ECs. The viable cells and MTS production were statistically higher in functionalized tissues than in control. Scaffold histoarchitecture, geometrical features, and mechanical properties were unaffected by peptide anchoring. The selective immobilization of REDV was effective in accelerating ECs adhesion while promoting proliferation in functionalized decellularized tissues intended for blood-contacting applications.

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Covalent functionalization of the decellularized tissues with REDV peptide accelerates endothelialization.

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New covalent grafting method not inducing collagen cross-linking.

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Measurements through two photon miscroscopy allow the quantification of biological matrix bound peptide.

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The decellularized tissues can be changed by chemical procedures to promote specific cellular behaviour with ECM preservation.

Spectroscopic assessment of oxidative damage in biomolecules and tissues

Oxidative damage is one of the main causes of cryopreservation injury compromising the use of cryopreserved biospecimens. The aim of this study was to evaluate the use of Fourier transform infrared spectroscopy (FTIR) as a non-invasive method to assess changes in biomolecular composition and structure, associated with oxidative stress in isolated biomolecules, acellular heart valve tissues, and ovarian cortex tissues. FTIR spectra of these specimens subjected to various treatments (H₂O₂- and Fenton-treatment or elevated temperatures) were vector normalized and selected spectral regions were analyzed by principal component analysis (PCA). Control and damaged biomolecules can easily be separated using PCA score plots. Acellular heart valve tissues that were subjected to different levels of oxidative damage formed separate cluster in PCA score plots. In hydrated ovarian tissue, large variation of the principal components was observed. Drying the ovarian tissues samples resulted in improved cluster separation of treatment groups. However, early signs of oxidative damage under mild stress conditions could not be detected by PCA of FTIR spectra. For the ovarian tissue samples, the standardly used nitro blue tetrazolium chloride (NBT) assay was used to monitor the amount of formazan production, reflecting reactive oxygen species (ROS) production at various temperatures. At 37 °C, formazan staining rapidly increased during the first 30 min, and then slowly reached a saturation level, but also at lower temperatures (i.e. 4 °C) formazan production was observed. In summary, we conclude that ATR-FTIR combined with PCA can be used to study oxidative damage in biomolecules as well as in tissues. In tissues, however, sample heterogeneity makes it difficult to detect early signs of oxidative damage.

Bioengineered percutaneous heart valves for transcatheter aortic valve replacement: a comparative evaluation of decellularised bovine and porcine pericardia

Glutaraldehyde-treated, surgical bioprosthetic heart valves undergo structural degeneration within 10-15 years of implantation. Analogous preliminary results were disclosed for percutaneous heart valves (PHVs) realized with similarly-treated tissues. To improve long-term performance, decellularised scaffolds can be proposed as alternative fabricating biomaterials. The aim of this study was to evaluate whether bovine and porcine decellularised pericardia could be utilised to manufacture bioengineered percutaneous heart valves (bioPHVs) with adequate hydrodynamic performance and leaflet resistance to crimping damage. BioPHVs were fabricated by mounting acellular pericardia onto commercial stents. Independently from the pericardial species used for valve fabrication, bioPHVs satisfied the minimum hydrodynamic performance criteria set by ISO 5840-3 standards and were able to withstand a large spectrum of cardiac output conditions, also during extreme backpressure, without severe regurgitation, especially in the case of the porcine group. No macroscopic or microscopic leaflet damage was detected following bioPHV crimping. Bovine and porcine decellularized pericardia are both suitable alternatives to glutaraldehyde-treated tissues. Between the two types of pericardial species tested, the porcine tissue scaffold might be preferable to fabricate advanced PHV replacements for long-term performance. CONDENSED ABSTRACT: Current percutaneous heart valve replacements are formulated with glutaraldehyde-treated animal tissues, prone to structural degeneration. In order to improve long-term performance, bovine and porcine decellularised pericardia were utilised to manufacture bioengineered replacements, which demonstrated adequate hydrodynamic behaviour and resistance to crimping without leaflet architectural alteration.

Large three-dimensional cell constructs for tissue engineering

Much research has been conducted on fabricating biomimetic biomaterials in vitro. Tissue engineering approaches are often conducted by combining cells, scaffolds, and growth factors. However, the degradation rate of scaffolds is difficult to control and the degradation byproducts occasionally limit tissue regeneration. To overcome these issues, we have developed a novel system using a thermo-responsive hydrogel that forms scaffold-free, three-dimensional (3D) cell constructs with arbitrary size and morphology. 3D cell constructs prepared using bone marrow-derived stromal stem cells (BMSCs) exhibited self-organizing ability and formed bone-like tissue with endochondral ossification. Endothelial cells were then introduced into the BMSC construct and a vessel-like structure was formed within the constructs. Additionally, the bone formation ability was promoted by endothelial cells and cell constructs could be freeze-dried to improve their clinical application. A pre-treatment with specific protein protectant allowed for the fabrication of novel bone substitutes composed only of cells. This 3D cell construct technology using thermo-responsive hydrogels was then applied to other cell species. Cell constructs composed of dental pulp stem cells were fabricated, and the resulting construct regenerated pulp-like tissue within a human pulpless tooth. In this review, we demonstrate the approaches for the in vitro fabrication of bone and dental pulp-like tissue using thermo-responsive hydrogels and their potential applications.

Principles Underlying Cryopreservation and Freeze-Drying of Cells and Tissues

Cryopreservation and freeze-drying can be used to preserve cells or tissues for prolonged periods. Vitrification, or ice-free cryopreservation, is an alternative to cryopreservation that enables cooling cells to cryogenic temperatures in the absence of ice. The processing pathways involved in (ice-free) cryopreservation and freeze-drying of cells and tissues, however, can be very damaging. In this chapter, we describe the principles underlying preservation of cells for which freezing and drying are normally lethal processes as well as for cells that are able to survive in a reversible state of suspended animation. Freezing results in solution effects injury and/or intracellular ice formation, whereas drying results in removal of (non-freezable) water normally bound to biomolecules, which is generally more damaging. Cryopreservation and freeze-drying require different types of protective agents. Different mechanistic modes of action of cryoprotective and lyoprotective agents are described including minimizing ice formation, preferential exclusion, water replacement, and vitrification. Furthermore, it is discussed how protective agents can be introduced into cells avoiding damage due to too large cell volume excursions, and how knowledge of cell-specific membrane permeability properties in various temperature regimes can be used to rationally design (ice-free) cryopreservation and freeze-drying protocols.

Long-term preservation effects on biological properties of acellular placental sponge patches

Decellularization, preservation protocol and storage time influence the biomechanical and biological properties of allografts and xenografts. Here, we examined the consequences of storage time on the antibacterial, angiogenic and biocompatibility properties of the decellularized placental sponge (DPS) in vitro and in vivo. The DPS samples were preserved for one, three and six months at -20 °C. The decellularized scaffolds showed uniform morphology with interconnected pores compared with not decellularized sponges. Storage time did not interfere with collagen and vascular endothelial growth factor contents, and cytobiocompatibility for Hu02 fibroblast cells. Chorioallantoic membrane assay and subcutaneous implantation indicated a decreased new vessel formation and neovascularization in six months DPS sample compared with other experimental groups. The number of CD4⁺ and CD68⁺ cells infiltrated into the six months DPS on the implanted site showed a significant increase compared with one and three months sponges. The antibacterial activities and angiogenic properties of the DPS decreased over storage time. Three months preservation at -20 °C is suggested as the optimal storage period to retain its antibacterial activity and high stimulation of new vessel formation. This storage protocol could be considered for preservation of similar decellularized placenta-derived products with the aim of retaining their biological properties.

RegenHeart: A Time-Effective, Low-Concentration, Detergent-Based Method Aiming for Conservative Decellularization of the Whole Heart Organ

Heart failure is the worst outcome of all cardiovascular diseases and still represents nowadays the leading cause of mortality with no effective clinical treatments, apart from organ transplantation with allogeneic or artificial substitutes. Although applied as the gold standard, allogeneic heart transplantation cannot be considered a permanent clinical answer because of several drawbacks, as the side effects of administered immunosuppressive therapies. For the increasing number of heart failure patients, a biological cardiac substitute based on a decellularized organ and autologous cells might be the lifelong, biocompatible solution free from the need for immunosuppression regimen. A novel decellularization method is here proposed and tested on rat hearts in order to reduce the concentration and incubation time with cytotoxic detergents needed to render acellular these organs. By protease inhibition, antioxidation, and excitation–contraction uncoupling in simultaneous perfusion/submersion modality, a strongly limited exposure to detergents was sufficient to generate very well-preserved acellular hearts with unaltered extracellular matrix macro- and microarchitecture, as well as bioactivity.

Bovine Decellularized Amniotic Membrane: Extracellular Matrix as Scaffold for Mammalian Skin

Decellularized membranes (DM) were obtained from bovine amniotic membranes (BAM) using four different decellularization protocols, based on physical, chemical, and mechanical treatment. The new material was used as a biological scaffold for in vitro skin cell culture. The DM were characterized using hematoxylin-eosin assay, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR-ATR), and differential scanning calorimetry (DSC). The in vitro cytotoxicity of DM was evaluated using MTT. The efficacy of decellularization process was assessed through DNA quantification and electrophoresis. All the used protocols showed a high effectiveness in terms of elimination of native cells, confirmed by DNA extraction and quantification, electrophoresis, and SEM, although protocol IV removes the cellular contents and preserve the native extracellular matrix (ECM) architecture which it can be considered as the most effective in terms of decellularization. FTIR-ATR and DSC on the other hand, revealed the effects of decellularization on the biochemical composition of the matrices. There was no cytotoxicity and the biological matrices obtained were a source of collagen for recellularization. The matrices of protocols I, II, and III were degraded at day 21 of cell culture, forming a gel. The biocompatibility in vitro was demonstrated; hence these matrices may be deemed as potential scaffold for epithelial tissue regeneration.

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.

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.