Maintenance of human hepatocyte function in vitro by liver-derived extracellular matrix gels

3D bioprinting technology innovation in female reproductive system

Several diseases affect the female reproductive system, and both disease factors and treatments impact its integrity and function. Consequently, understanding the mechanisms of disease occurrence and exploring treatment methods are key research focuses in obstetrics and gynecology. However, constructing accurate disease models requires a microenvironment closely resembling the human body, and current animal models and 2D in vitro cell models fall short in this regard. Thus, innovative in vitro female reproductive system models are urgently needed. Additionally, female reproductive system diseases often cause tissue loss, yet effective tissue repair and regeneration have long been a bottleneck in the medical field. 3D bioprinting offers a solution by enabling the construction of implants with tissue repair and regeneration capabilities, promoting cell adhesion, extension, and proliferation. This helps maintain the long-term efficacy of bioactive implants and achieves both structural and functional repair of the reproductive system. By combining live cells with biomaterials, 3D bioprinting can create in vitro 3D biomimetic cellular models, facilitating in-depth studies of cell-cell and cell-extracellular microenvironment interactions, which enhances our understanding of reproductive system diseases and supports disease-specific drug screening. This article reviews 3D bioprinting methods and materials applicable to the female reproductive system, discussing their advantages and limitations to aid in selecting optimal 3D bioprinting strategies. We also summarize and critically evaluate recent advancements in 3D bioprinting applications for tissue regeneration and in vitro disease models and address the prospects and challenges for translating 3D bioprinting technology into clinical applications within the female reproductive system.

Effects of decellularization on glycosaminoglycans and collagen macromolecules in bovine bone extracellular matrix

Bovine bones were decellularized to obtain extracellular matrices with potential use for Tissue Bioengineering. The objective of the present study was to develop a decellularization protocol for bovine trabecular bone while maintaining the integrity of the extracellular matrix (ECM). The protocol proved to be effective in significantly reducing the Amount of genetic material and cellular content, and it was considered innovative, being filed as a patent. The scaffold obtained showed a reduction in the content of glycosaminoglycans (GAGs) and collagen. Even with the loss of these ECM components, the material obtained can be considered an alternative for use in Tissue Engineering and Regenerative Medicine.

Evaluating the synergistic use of advanced liver models and AI for the prediction of drug-induced liver injury

INTRODUCTION

Drug-induced liver injury (DILI) is a leading cause of acute liver failure. Hepatotoxicity typically occurs only in a subset of individuals after prolonged exposure and constitutes a major risk factor for the termination of drug development projects.

AREAS COVERED

We provide an overview of available human liver models for DILI research and discuss how they have been used to aid in early risk assessments and to mitigate the risk of project closures due to DILI in clinical stages. We summarize the different data that can be provided by such models and illustrate how these diverse data types can be interfaced with machine learning strategies to improve predictions of liver safety liabilities.

EXPERT OPINION

Advanced human liver models closely mimic human liver phenotypes and functions for many weeks, allowing for the recapitulation of hepatotoxicity events in vitro. Integration of the biochemical, histological, and toxicogenomic output data from these models with physicochemical compound properties using different machine learning architectures holds promise to enhance preclinical DILI predictions. However, to realize this aim, it is important to benchmark the available liver models on test sets of DILI positive and negative compounds and to carefully annotate and share the resulting data.

Application of Additive Manufacturing in Assisted Reproductive Techniques: What Is the Evidence? A Clinical and Technical Systematic Review of the Literature

Background and Objectives: This article investigates the transformative impact of 3D and bio 3D printing technologies in assisted reproductive technology (ART), offering a comprehensive review of their applications in improving reproductive outcomes. Materials and Methods: Following PRISMA guidelines, we conducted a thorough literature search focusing on the intersection of ART and additive manufacturing, resulting in the inclusion of 48 research papers. Results: The study highlights bio 3D printing's potential in revolutionizing female infertility treatments, especially in follicle complex culture and ovary printing. We explore the use of decellularized extracellular matrix (dECM) as bioink, demonstrating its efficacy in replicating the ovarian microenvironment for in vitro maturation of primordial oocytes. Furthermore, advancements in endometrial cavity interventions are discussed, including the application of sustained-release systems for growth factors and stem cell integration for endometrial regeneration, showing promise in addressing conditions like Asherman's syndrome and thin endometrium. We also examine the role of conventional 3D printing in reproductive medicine, including its use in educational simulators, personalized IVF instruments, and microfluidic platforms, enhancing training and precision in reproductive procedures. Conclusions: Our review underscores both 3D printing technologies' contribution to the dynamic landscape of reproductive medicine. They offer innovative solutions for individualized patient care, augmenting success rates in fertility treatments. This research not only presents current achievements but also anticipates future advancements in these domains, promising to expand the horizons for individuals and families seeking assistance in their reproductive journeys.

Advances in xenogeneic donor decellularized organs: A review on studies with sheep and porcine-derived heart valves

Heart valve replacement surgeries are performed on patients suffering from abnormal heart valve function. In these operations, the problematic tissue is replaced with mechanical valves or with bioprosthetics that are being developed. The thrombotic effect of mechanical valves, reflecting the need for lifelong use of anticoagulation drugs, and the short-lived nature of biological valves make these two types of valves problematic. In addition, they cannot adapt to the somatic growth of young patients. Although decellularized scaffolds have shown some promise, a successful translation has so far evaded. Although decellularized porcine xenografts have been extensively studied in the literature, they have several disadvantages, such as a propensity for calcification in the implant model, a risk of porcine endogenous retrovirus (PERV) infection, and a high xenoantigen density. As seen in clinical data, it is clear that there are biocompatibility problems in almost all studies. However, since decellularized sheep heart valves have not been tried in the clinic, a large data pool could not be established. This review compares and contrasts decellularized porcine and sheep xenografts for heart valve tissue engineering. It reveals that decellularized sheep heart valves can be an alternative to pigs in terms of biocompatibility. In addition, it highlights the potential advantages of bioinks derived from the decellularized extracellular matrix in 3D bioprinting technology, emphasizing that they can be a new alternative for the application. We also outline the future prospects of using sheep xenografts for heart valve tissue engineering.

An Ultrathin Coating of Microcapsules Enhances the Function of Encapsulated Hepatocyte Spheroids

Maintaining the differentiated phenotype and function of primary hepatocytes in vitro and in vivo represents a distinct challenge. Our paper describes microcapsules comprised of a bioactive polymer and overcoated with an ultrathin film as a means of maintaining the function of entrapped hepatocytes for at least two weeks. We previously demonstrated that heparin (Hep)-based microcapsules improved the function of entrapped primary hepatocytes by capturing and releasing cell-secreted inductive signals, including hepatocyte growth factor (HGF). Further enhancement of hepatic function could be gained by loading exogenous HGF into microcapsules. In this study, we demonstrate that an ultrathin coating of tannic acid (TA) further enhances endogenous HGF signaling for entrapped hepatocytes and increases by 2-fold the rate of uptake of exogenous HGF by Hep microcapsules. Hepatocytes in overcoated microcapsules exhibited better function and hepatic gene expression than in capsules without a TA coating. Our study showcases the potential application of ultrathin coatings to modulate the bioactivity of microcapsules and may enable the use of encapsulated hepatocytes for modeling drug toxicity or treating liver diseases.

Which detergent is most suitable for the generation of an acellular pancreas bioscaffold?

Pancreatic bioengineering is a potential therapeutic alternative for type 1 diabetes (T1D) in which the pancreas is decellularized, generating an acellular extracellular matrix (ECM) scaffold, which may be reconstituted by recellularization with several cell types to generate a bioartificial pancreas. No consensus for an ideal pancreatic decellularization protocol exists. Therefore, we aimed to determine the best-suited detergent by comparing sodium dodecyl sulfate (SDS), sodium deoxycholate (SDC), and Triton X-100 at different concentrations. Murine (n=12) and human pancreatic tissue from adult brain-dead donors (n=06) was harvested in accordance with Institutional Ethical Committee of the University of São Paulo Medical School (CEP-FMUSP) and decellularized under different detergent conditions. DNA content, histological analysis, and transmission and scanning electron microscopy were assessed. The most adequate condition for pancreatic decellularization was found to be 4% SDC, displaying: a) effective cell removal; b) maintenance of extracellular matrix architecture; c) proteoglycans, glycosaminoglycans (GAGs), and collagen fibers preservation. This protocol was extrapolated and successfully applied to human pancreas decellularization. The acellular ECM scaffold generated was recelullarized using human pancreatic islets primary clusters. 3D clusters were generated using 0.5×104 cells and then placed on top of acellular pancreatic slices (25 and 50 μm thickness). These clusters tended to connect to the acellular matrix, with visible cells located in the periphery of the clusters interacting with the ECM network of the bioscaffold slices and continued to produce insulin. This study provided evidence on how to improve and accelerate the pancreas decellularization process, while maintaining its architecture and extracellular structure, aiming at pancreatic bioengineering.

The Prospect of Hepatic Decellularized Extracellular Matrix as a Bioink for Liver 3D Bioprinting

The incidence of liver diseases is high worldwide. Many factors can cause liver fibrosis, which in turn can lead to liver cirrhosis and even liver cancer. Due to the shortage of donor organs, immunosuppression, and other factors, only a few patients are able to undergo liver transplantation. Therefore, how to construct a bioartificial liver that can be transplanted has become a global research hotspot. With the rapid development of three-dimensional (3D) bioprinting in the field of tissue engineering and regenerative medicine, researchers have tried to use various 3D bioprinting technologies to construct bioartificial livers in vitro. In terms of the choice of bioinks, liver decellularized extracellular matrix (dECM) has many advantages over other materials for cell-laden hydrogel in 3D bioprinting. This review mainly summarizes the acquisition of liver dECM and its application in liver 3D bioprinting as a bioink with respect to availability, printability, and biocompatibility in many aspects and puts forward the current challenges and prospects.

Paintable Decellularized-ECM Hydrogel for Preventing Cardiac Tissue Damage

The tissue-specific heart decellularized extracellular matrix (hdECM) demonstrates a variety of therapeutic advantages, including fibrosis reduction and angiogenesis. Consequently, recent research for myocardial infarction (MI) therapy has utilized hdECM with various delivery techniques, such as injection or patch implantation. In this study, a novel approach for hdECM delivery using a wet adhesive paintable hydrogel is proposed. The hdECM-containing paintable hydrogel (pdHA_t) is simply applied, with no theoretical limit to the size or shape, making it highly beneficial for scale-up. Additionally, pdHA_t exhibits robust adhesion to the epicardium, with a minimal swelling ratio and sufficient adhesion strength for MI treatment when applied to the rat MI model. Moreover, the adhesiveness of pdHA_t can be easily washed off to prevent undesired adhesion with nearby organs, such as the rib cages and lungs, which can result in stenosis. During the 28 days of in vivo analysis, the pdHA_t not only facilitates functional regeneration by reducing ventricular wall thinning but also promotes neo-vascularization in the MI region. In conclusion, the pdHA_t presents a promising strategy for MI treatment and cardiac tissue regeneration, offering the potential for improved patient outcomes and enhanced cardiac function post-MI.

Bioprinting of Perfusable, Biocompatible Vessel-like Channels with dECM-Based Bioinks and Living Cells

There is a growing interest in the production of bioinks that on the one hand, are biocompatible and, on the other hand, have mechanical properties that allow for the production of stable constructs that can survive for a long time after transplantation. While the selection of the right material is crucial for bioprinting, there is another equally important issue that is currently being extensively researched-the incorporation of the vascular system into the fabricated scaffolds. Therefore, in the following manuscript, we present the results of research on bioink with unique physico-chemical and biological properties. In this article, two methods of seeding cells were tested using bioink B and seeding after bioprinting the whole model. After 2, 5, 8, or 24 h of incubation, the flow medium was used in the tested systems. At the end of the experimental trial, for each time variant, the canals were stored in formaldehyde, and immunohistochemical staining was performed to examine the presence of cells on the canal walls and roof. Cells adhered to both ways of fiber arrangement; however, a parallel bioprint with the 5 h incubation and the intermediate plating of cells resulted in better adhesion efficiency. For this test variant, the percentage of cells that adhered was at least 20% higher than in the other analyzed variants. In addition, it was for this variant that the lowest percentage of viable cells was found that were washed out of the tested model. Importantly, hematoxylin and eosin staining showed that after 8 days of culture, the cells were evenly distributed throughout the canal roof. Our study clearly shows that neovascularization-promoting cells effectively adhere to ECM-based pancreatic bioink. Summarizing the presented results, it was demonstrated that the proposed bioink compositions can be used for bioprinting bionic organs with a vascular system formed by endothelial cells and fibroblasts.

Decellularization and Their Significance for Tissue Regeneration in the Era of 3D Bioprinting

Three-dimensional bioprinting is an emerging technology that has high potential application in tissue engineering and regenerative medicine. Increasing advancement and improvement in the decellularization process have led to an increase in the demand for using a decellularized extracellular matrix (dECM) to fabricate tissue engineered products. Decellularization is the process of retaining the extracellular matrix (ECM) while the cellular components are completely removed to harvest the ECM for the regeneration of various tissues and across different sources. Post decellularization of tissues and organs, they act as natural biomaterials to provide the biochemical and structural support to establish cell communication. Selection of an effective method for decellularization is crucial, and various factors like tissue density, geometric organization, and ECM composition affect the regenerative potential which has an impact on the end product. The dECM is a versatile material which is added as an important ingredient to formulate the bioink component for constructing tissue and organs for various significant studies. Bioink consisting of dECM from various sources is used to generate tissue-specific bioink that is unique and to mimic different biometric microenvironments. At present, there are many different techniques applied for decellularization, and the process is not standardized and regulated due to broad application. This review aims to provide an overview of different decellularization procedures, and we also emphasize the different dECM-derived bioinks present in the current global market and the major clinical outcomes. We have also highlighted an overview of benefits and limitations of different decellularization methods and various characteristic validations of decellularization and dECM-derived bioinks.

Enhancement of lacrimal gland cell function by decellularized lacrimal gland derived hydrogel

Sustainable treatment of aqueous deficient dry eye (ADDE) represents an unmet medical need and therefore requires new curative and regenerative approaches based on appropriatein vitromodels. Tissue specific hydrogels retain the individual biochemical composition of the extracellular matrix and thus promote the inherent cell´s physiological function. Hence, we created a decellularized lacrimal gland (LG) hydrogel (dLG-HG) meeting the requirements for a bioink as the basis of a LG model with potential forin vitroADDE studies. Varying hydrolysis durations were compared to obtain dLG-HG with best possible physical and ultrastructural properties while preserving the original biochemical composition. A particular focus was placed on dLG-HG´s impact on viability and functionality of LG associated cell types with relevance for a futurein vitromodel in comparison to the unspecific single component hydrogel collagen type-I (Col) and the common cell culture substrate Matrigel. Proliferation of LG epithelial cells (EpC), LG mesenchymal stem cells, and endothelial cells cultured on dLG-HG was enhanced compared to culture on Matrigel. Most importantly with respect to a functionalin vitromodel, the secretion capacity of EpC cultured on dLG-HG was higher than that of EpC cultured on Col or Matrigel. In addition to these promising cell related properties, a rapid matrix metalloproteinase-dependent biodegradation was observed, which on the one hand suggests a lively cell-matrix interaction, but on the other hand limits the cultivation period. Concluding, dLG-HG possesses decisive properties for the tissue engineering of a LGin vitromodel such as cytocompatibility and promotion of secretion, making it superior to unspecific cell culture substrates. However, deceleration of biodegradation should be addressed in future experiments.

Three Dimensional Bioprinting for Hepatic Tissue Engineering: From In Vitro Models to Clinical Applications

Fabrication of functional organs is the holy grail of tissue engineering and the possibilities of repairing a partial or complete liver to treat chronic liver disorders are discussed in this review. Liver is the largest gland in the human body and plays a responsible role in majority of metabolic function and processes. Chronic liver disease is one of the leading causes of death globally and the current treatment strategy of organ transplantation holds its own demerits. Hence there is a need to develop an in vitro liver model that mimics the native microenvironment. The developed model should be a reliable to understand the pathogenesis, screen drugs and assist to repair and replace the damaged liver. The three-dimensional bioprinting is a promising technology that recreates in vivo alike in vitro model for transplantation, which is the goal of tissue engineers. The technology has great potential due to its precise control and its ability to homogeneously distribute cells on all layers in a complex structure. This review gives an overview of liver tissue engineering with a special focus on 3D bioprinting and bioinks for liver disease modelling and drug screening.

Decellularized Liver Nanofibers Enhance and Stabilize the Long-Term Functions of Primary Human Hepatocytes In Vitro

Owing to significant differences across species in liver functions, in vitro human liver models are used for screening the metabolism and toxicity of compounds, modeling diseases, and cell-based therapies. However, the extracellular matrix (ECM) scaffold used for such models often does not mimic either the complex composition or the nanofibrous topography of native liver ECM. Thus, here novel methods are developed to electrospin decellularized porcine liver ECM (PLECM) and collagen I into nano- and microfibers (≈200-1000 nm) without synthetic polymer blends. Primary human hepatocytes (PHHs) on nanofibers in monoculture or in coculture with nonparenchymal cells (3T3-J2 embryonic fibroblasts or primary human liver endothelial cells) display higher albumin secretion, urea synthesis, and cytochrome-P450 1A2, 2A6, 2C9, and 3A4 enzyme activities than on conventionally adsorbed ECM controls. PHH functions are highest on the collagen/PLECM blended nanofibers (up to 34-fold higher CYP3A4 activity relative to adsorbed ECM) for nearly 7 weeks in the presence of the fibroblasts. In conclusion, it is shown for the first time that ECM composition and topography synergize to enhance and stabilize PHH functions for several weeks in vitro. The nanofiber platform can prove useful for the above applications and to elucidate cell-ECM interactions in the human liver.

Extracellular matrix cues regulate the differentiation of pluripotent stem cell-derived endothelial cells

The generation of endothelial cells (ECs) from human pluripotent stem cells (PSCs) has been a promising approach for treating cardiovascular diseases for several years. Human PSCs, particularly induced pluripotent stem cells (iPSCs), are an attractive source of ECs for cell therapy. Although there is a diversity of methods for endothelial cell differentiation using biochemical factors, such as small molecules and cytokines, the efficiency of EC production varies depending on the type and dose of biochemical factors. Moreover, the protocols in which most EC differentiation studies have been performed were in very unphysiological conditions that do not reflect the microenvironment of native tissue. The microenvironment surrounding stem cells exerts variable biochemical and biomechanical stimuli that can affect stem cell differentiation and behavior. The stiffness and components of the extracellular microenvironment are critical inducers of stem cell behavior and fate specification by sensing the extracellular matrix (ECM) cues, adjusting the cytoskeleton tension, and delivering external signals to the nucleus. Differentiation of stem cells into ECs using a cocktail of biochemical factors has been performed for decades. However, the effects of mechanical stimuli on endothelial cell differentiation remain poorly understood. This review provides an overview of the methods used to differentiate ECs from stem cells by chemical and mechanical stimuli. We also propose the possibility of a novel EC differentiation strategy using a synthetic and natural extracellular matrix.

Development potential of extracellular matrix hydrogels as hemostatic materials

The entry of subcutaneous extracellular matrix proteins into the circulation is a key step in hemostasis initiation after vascular injury. However, in cases of severe trauma, extracellular matrix proteins are unable to cover the wound, making it difficult to effectively initiate hemostasis and resulting in a series of bleeding events. Acellular-treated extracellular matrix (ECM) hydrogels are widely used in regenerative medicine and can effectively promote tissue repair due to their high mimic nature and excellent biocompatibility. ECM hydrogels contain high concentrations of extracellular matrix proteins, including collagen, fibronectin, and laminin, which can simulate subcutaneous extracellular matrix components and participate in the hemostatic process. Therefore, it has unique advantages as a hemostatic material. This paper first reviewed the preparation, composition and structure of extracellular hydrogels, as well as their mechanical properties and safety, and then analyzed the hemostatic mechanism of the hydrogels to provide a reference for the application and research, and development of ECM hydrogels in the field of hemostasis.

3D bioprinting of tissue constructs employing dual crosslinking of decellularized extracellular matrix hydrogel

Bioprinted tissues are currently being utilized for drug and cosmetic screening mostly, but the long-term goal is to achieve human scale functional tissues and organs for transplantation. Hence, recapitulating the multiscale architecture, 3D structures, and complexity of native tissues is the key to produce bioengineered tissues/organs. Decellularized extracellular matrix (dECM)-based biomaterials are widely being used as bioinks for 3D bioprinting for tissue engineering applications. Their potential to provide excellent biocompatibility for the cells drove researchers to use them extensively. However, the decellularization process involves many detergents and enzymes which may contribute to their loss of mechanical properties. Moreover, thermal gelation of dECM-based hydrogels is typically slow which affects the shape fidelity, printability, and physical properties while printing complex structures with 3D printing. But, thermally gelled dECM hydrogels provide excellent cell viability and functionality. To overcome this, a novel dual crosslinking of unmodified dECM has been proposed in this study to render shape fidelity and enhance cell viability and functionality. The dECM-based bioink can be initially polymerized superficially on exposure to light to achieve immediate stability and can attain further stability upon thermal gelation. This dual crosslinking mechanism can maintain the microenvironment of the structure, hence allowing the printing of stable flexible structures. Optimized concentrations of novel photo crosslinkers have been determined and printing of a few complex-shaped anatomical structures has been demonstrated. This approach of fabricating complex scaffolds employing dual crosslinking can be used for the bioprinting of different complex tissue structures with tissue-specific dECM based bioinks.

Monitoring Cultured Rat Hepatocytes Using RNA-Seq In Vitro

Compared to other techniques, RNA sequencing (RNA-Seq) has the advantage of having details of the expression abundance of all transcripts in a single run. In this study, we used RNA-Seq to monitor the maturity and dynamic characteristics of in vitro hepatocyte cultures. Hepatocytes, including mature hepatocytes and small hepatocytes, were analyzed in vitro using RNA-Seq and quantitative polymerase chain reaction (qPCR). The results demonstrated that the gene expression profiles measured by RNA-Seq showed a similar trend to the expression profiles measured by qPCR, and can be used to infer the success of in vitro hepatocyte cultures. The results of the differential analysis, which compared mature hepatocytes against small hepatocytes, revealed 836 downregulated and 137 upregulated genes. In addition, the success of the hepatocyte cultures could be explained by the gene list screened from the adopted gene enrichment test. In summary, we demonstrated that RNA-Seq could become an effective method for monitoring the whole transcriptome of hepatocyte cultures and provide a more comprehensive list of factors related to the differentiation of small hepatocytes into mature hepatocytes. This monitoring system not only shows high potential in medical applications but may also be a novel method for the clinical diagnosis of liver-related diseases.

Decellularized ECM hydrogels: prior use considerations, applications, and opportunities in tissue engineering and biofabrication

Tissue development, wound healing, pathogenesis, regeneration, and homeostasis rely upon coordinated and dynamic spatial and temporal remodeling of extracellular matrix (ECM) molecules. ECM reorganization and normal physiological tissue function, require the establishment and maintenance of biological, chemical, and mechanical feedback mechanisms directed by cell-matrix interactions. To replicate the physical and biological environment provided by the ECM in vivo, methods have been developed to decellularize and solubilize tissues which yield organ and tissue-specific bioactive hydrogels. While these biomaterials retain several important traits of the native ECM, the decellularizing process, and subsequent sterilization, and solubilization result in fragmented, cleaved, or partially denatured macromolecules. The final product has decreased viscosity, moduli, and yield strength, when compared to the source tissue, limiting the compatibility of isolated decellularized ECM (dECM) hydrogels with fabrication methods such as extrusion bioprinting. This review describes the physical and bioactive characteristics of dECM hydrogels and their role as biomaterials for biofabrication. In this work, critical variables when selecting the appropriate tissue source and extraction methods are identified. Common manual and automated fabrication techniques compatible with dECM hydrogels are described and compared. Fabrication and post-manufacturing challenges presented by the dECM hydrogels decreased mechanical and structural stability are discussed as well as circumvention strategies. We further highlight and provide examples of the use of dECM hydrogels in tissue engineering and their role in fabricating complex in vitro 3D microenvironments.

Advances in Recellularization of Decellularized Liver Grafts with Different Liver (Stem) Cells: Towards Clinical Applications

Liver transplantation is currently the only curative therapy for patients with acute or chronic liver failure. However, a dramatic gap between the number of available liver grafts and the number of patients on the transplantation waiting list emphasizes the need for valid liver substitutes. Whole-organ engineering is an emerging field of tissue engineering and regenerative medicine. It aims to generate transplantable and functional organs to support patients on transplantation waiting lists until a graft becomes available. It comprises two base technologies developed in the last decade; (1) organ decellularization to generate a three-dimensional (3D) extracellular matrix scaffold of an organ, and (2) scaffold recellularization to repopulate both the parenchymal and vascular compartments of a decellularized organ. In this review article, recent advancements in both technologies, in relation to liver whole-organ engineering, are presented. We address the potential sources of hepatocytes and non-parenchymal liver cells for repopulation studies, and the role of stem-cell-derived liver progeny is discussed. In addition, different cell seeding strategies, possible graft modifications, and methods used to evaluate the functionality of recellularized liver grafts are outlined. Based on the knowledge gathered from recent transplantation studies, future directions are summarized.

Recent Developments in 3D Bio-Printing and Its Biomedical Applications

The fast-developing field of 3D bio-printing has been extensively used to improve the usability and performance of scaffolds filled with cells. Over the last few decades, a variety of tissues and organs including skin, blood vessels, and hearts, etc., have all been produced in large quantities via 3D bio-printing. These tissues and organs are not only able to serve as building blocks for the ultimate goal of repair and regeneration, but they can also be utilized as in vitro models for pharmacokinetics, drug screening, and other purposes. To further 3D-printing uses in tissue engineering, research on novel, suitable biomaterials with quick cross-linking capabilities is a prerequisite. A wider variety of acceptable 3D-printed materials are still needed, as well as better printing resolution (particularly at the nanoscale range), speed, and biomaterial compatibility. The aim of this study is to provide expertise in the most prevalent and new biomaterials used in 3D bio-printing as well as an introduction to the associated approaches that are frequently considered by researchers. Furthermore, an effort has been made to convey the most pertinent implementations of 3D bio-printing processes, such as tissue regeneration, etc., by providing the most significant research together with a comprehensive list of material selection guidelines, constraints, and future prospects.

Decellularized tympanic membrane scaffold with bone marrow mesenchymal stem cells for repairing tympanic membrane perforation

BACKGROUND

Tympanic membrane perforation (TMP) is a common disease in otology, and few acellular techniques have been reported for repairing this condition. Decellularized extracellular matrix (ECM) scaffolds have been used in organ reconstruction.

OBJECTIVE

This study on tissue engineering aimed to develop a tympanic membrane (TM) scaffold prepared using detergent immersion and bone marrow mesenchymal stem cells (BMSCs) as repair materials to reconstruct the TM.

RESULTS

General structure was observed that the decellularized TM scaffold with BMSCs retained the original intact anatomical ECM structure, with no cell residue, as observed using scanning electron microscopy (SEM), and exhibited low immunogenicity. Therefore, we seeded the decellularized TM scaffold with BMSCs for recellularization. Histology and eosin staining, SEM and immunofluorescence in vivo showed that the recellularized TM patch had a natural ultrastructure and was suitable for the migration and proliferation of BMSCs. The auditory brainstem response (ABR) evaluated after recellularized TM patch repair was slightly higher than that of the normal TM, but the difference was not significant.

CONCLUSION

The synthetic ECM scaffold provides temporary physical support for the three-dimensional growth of cells during the tissue developmental stage. The scaffold stimulates cells to secrete their own ECM required for tissue regeneration. The recellularized TM patch shows potential as a natural, ultrastructure biological material for TM reconstruction.

Construction of antibacterial nano-silver embedded bioactive hydrogel to repair infectious skin defects

Background

Hydrogels loaded with antimicrobial agents have been widely used for treating infected wound defects. However, hydrogels derived from a porcine dermal extracellular matrix (PADM), containing silver nanoparticles (AgNPs), have not yet been studied. Therefore, we investigated the therapeutic effect of an AgNP-impregnated PADM (AgNP–PADM) hydrogel on the treatment of infected wounds.

Methods

An AgNP–PADM hydrogel was synthesized by embedding AgNPs into a PADM hydrogel. We examined the porosity, moisture retention, degradation, antibacterial properties, cytotoxicity, antioxidant properties, and ability of the PADM and AgNP–PADM hydrogels to treat infected wounds in animals.

Results

The PADM and AgNP–PADM hydrogels were pH sensitive, which made them flow dynamically and solidify under acidic and neutral conditions, respectively. The hydrogels also exhibited porous network structures, satisfactory moisture retention, and slow degradation. Additionally, the AgNP–PADM hydrogel showed a slow and sustained release of AgNPs for at least 7 days without the particle size changing. Thus, the AgNPs exhibited adequate antibacterial ability, negligible toxicity, and antioxidant properties in vitro. Moreover, the AgNP–PADM hydrogel promoted angiogenesis and healed infected skin defects in vivo.

Conclusions

The AgNP–PADM hydrogel is a promising bioderived antibacterial material for clinical application to infected wound dressings.

Preparation and Use of Decellularized Extracellular Matrix for Tissue Engineering

The multidisciplinary fields of tissue engineering and regenerative medicine have the potential to revolutionize the practise of medicine through the abilities to repair, regenerate, or replace tissues and organs with functional engineered constructs. To this end, tissue engineering combines scaffolding materials with cells and biologically active molecules into constructs with the appropriate structures and properties for tissue/organ regeneration, where scaffolding materials and biomolecules are the keys to mimic the native extracellular matrix (ECM). For this, one emerging way is to decellularize the native ECM into the materials suitable for, directly or in combination with other materials, creating functional constructs. Over the past decade, decellularized ECM (or dECM) has greatly facilitated the advance of tissue engineering and regenerative medicine, while being challenged in many ways. This article reviews the recent development of dECM for tissue engineering and regenerative medicine, with a focus on the preparation of dECM along with its influence on cell culture, the modification of dECM for use as a scaffolding material, and the novel techniques and emerging trends in processing dECM into functional constructs. We highlight the success of dECM and constructs in the in vitro, in vivo, and clinical applications and further identify the key issues and challenges involved, along with a discussion of future research directions.

Current strategies with implementation of three-dimensional cell culture: the challenge of quantification

From growing cells in spheroids to arranging them on complex engineered scaffolds, three-dimensional cell culture protocols are rapidly expanding and diversifying. While these systems may often improve the physiological relevance of cell culture models, they come with technical challenges, as many of the analytical methods used to characterize traditional two-dimensional (2D) cells must be modified or replaced to be effective. Here we review the advantages and limitations of quantification methods based either on biochemical measurements or microscopy imaging. We focus on the most basic of parameters that one may want to measure, the number of cells. Precise determination of this number is essential for many analytical techniques where measured quantities are only meaningful when normalized to the number of cells (e.g. cytochrome p450 enzyme activity). Thus, accurate measurement of cell number is often a prerequisite to allowing comparisons across different conditions (culturing conditions or drug and treatment screening) or between cells in different spatial states. We note that this issue is often neglected in the literature with little or no information given regarding how normalization was performed, we highlight the pitfalls and complications of quantification and call for more accurate reporting to improve reproducibility.

Analysis of decellularized mouse liver fragment and its recellularization with human endometrial mesenchymal cells as a candidate for clinical usage

Decellularized tissue has been used as a natural extracellular matrix (ECM) or bioactive biomaterial for tissue engineering. The present study aims to compare and analyze different decellularization protocols for mouse liver fragments and cell seeding and attachment in the created scaffold using human endometrial mesenchymal cells (hEMCs).After collecting and dissecting the mouse liver into small fragments, they were decellularized by Triton X-100 and six concentrations of sodium dodecyl sulfate (SDS; 0.025, 0.05, 0.1, 0.25, 0.5, and 1%) at different exposure times. The morphology and DNA content of decellularized tissues were studied, and the group with better morphology and lower DNA content was selected for additional assessments. Masson's tri-chrome and periodic acid Schiff staining were performed to evaluate ECM materials. Raman confocal spectroscopy analysis was used to quantify the amount of collagen type I, III and IV, glycosaminoglycans and elastin. Scanning electron microscopy and MTT assay were applied to assess the ultrastructure and porosity and cytotoxicity of decellularized scaffolds, respectively. In the final step, hEMCs were seeded on the decellularized scaffold and cultured for one week, and finally the cell attachment and homing were studied morphologically.The treated group with 0.1% SDS for 24 h showed a well preserved ECM morphology similar to native control and showing the minimum level of DNA. Raman spectroscopy results demonstrated that the amount of collagen type I and IV was not significantly changed in this group compared to the control, but a significant reduction in collagen III and elastin protein levels was seen (P < 0.001). The micrographs showed a porous ECM in decellularized sample similar to the native control with the range of 2.25 µm to 7.86 µm. After cell seeding, the infiltration and migration of cells in different areas of the scaffold were seen. In conclusion, this combined protocol for mouse liver decellularization is effective and its recellularization with hEMCs could be suitable for clinical applications in the future.

3d oxidized alginate-porcine liver acellular collagen droplets for tumor microenvironment mimicking

The traditional 2d culture has been proved inferior to reproduce the subtle interaction between cell-to-cell and cell-to-extracellular matrix (ECM) in tumor microenvironment (TME) and collagen in ECM contributes to various malignancies of tumors. Hence, the 3d model contained with collagen may overcome the shortcomings of 2d culture. In this study, the in vitro TME mimicking matrix was prepared by coupling porcine liver-derived collagen (COL) and the dialdehyde group of partially oxidized alginate (OA), namely OA-COL, and the 3d OA-COL droplets were polymerized by divalent calcium ions. In the 3d OA-COL droplets, cancer cells displayed vigorous proliferation, and the cells grew in clusters and formed a unique spindle like clone. Quantitative analysis proved that various gene transcription and protein expression were up-regulated for the cells in the 3d OA-COL droplets, including F-actin reassembling, focal adhesion, pseudopodia formation, and the proteins involved in epithelial-to-mesenchymal transition (EMT). The 3d OA-COL droplets induced the cells with strengthened polarity, invasiveness, higher IC50, and manifested stronger tumorigenicity in vivo. The fabricated 3d OA-COL droplets reproduced a variety of TME parameters, constructed an in vitro model similar to the TME in vivo, and it may facilitate many investigations in cell biology and tumor biology.

Biocompatibility-on-a-chip: Characterization and evaluation of decellularized tendon extracellular matrix (tdECM) hydrogel for 3D stem cell culture in a microfluidic device

Researchers have always tried expensive in vitro tests to show the 3D usability of dECM. The use of tissue-specific hydrogels in a microfluidic device is rarely studied. In this study, we have used ECM obtained from goat digital flexor tendons by decellularization technique. The tdECM was characterized for its structural properties using Scanning Electron Microscopy (SEM). Collagen, dsDNA, GAGs, and protein contents were quantified using spectrophotometric assays. The cell viability and proliferation of human umbilical cord-derived mesenchymal stem cells (hUMSCs) encapsulated in the tdECM hydrogel inside the microfluidic device were checked using Calcein-AM/PI. The FTIR data showed prominent peaks of the amide group, indicating the presence of collagen. The SEM data showed intact fiber morphology after the decellularization process. There was a 95 % reduction in double-stranded DNA (dsDNA) content, proving the effectiveness of the decellularization technique. There was no significant difference in the collagen content of tdECM and the GAGs were also in the acceptable range compared to the native tissue. Over 90 % cell viability in hUMSCs was observed qualitatively and quantitatively in vitro and inside a microfluidic device. In conclusion, we characterized the tdECM hydrogel and demonstrated its compatibility with the microfluidic device.

Three-Dimensional (3D) Printing in Cancer Therapy and Diagnostics: Current Status and Future Perspectives

Three-dimensional (3D) printing is a technique where the products are printed layer-by-layer via a series of cross-sectional slices with the exact deposition of different cell types and biomaterials based on computer-aided design software. Three-dimensional printing can be divided into several approaches, such as extrusion-based printing, laser-induced forward transfer-based printing systems, and so on. Bio-ink is a crucial tool necessary for the fabrication of the 3D construct of living tissue in order to mimic the native tissue/cells using 3D printing technology. The formation of 3D software helps in the development of novel drug delivery systems with drug screening potential, as well as 3D constructs of tumor models. Additionally, several complex structures of inner tissues like stroma and channels of different sizes are printed through 3D printing techniques. Three-dimensional printing technology could also be used to develop therapy training simulators for educational purposes so that learners can practice complex surgical procedures. The fabrication of implantable medical devices using 3D printing technology with less risk of infections is receiving increased attention recently. A Cancer-on-a-chip is a microfluidic device that recreates tumor physiology and allows for a continuous supply of nutrients or therapeutic compounds. In this review, based on the recent literature, we have discussed various printing methods for 3D printing and types of bio-inks, and provided information on how 3D printing plays a crucial role in cancer management.

Decellularized Periosteum-Derived Hydrogels Promote the Proliferation, Migration and Osteogenic Differentiation of Human Umbilical Cord Mesenchymal Stem Cells

Human umbilical cord mesenchymal stem cells (hUCMSCs) are promising for bone tissue engineering, which have a non-invasive harvesting process, high cell yield, favorable proliferation capacity, and low immunogenicity. However, the osteogenic efficacy of hUCMSCs is relatively lower than that of bone marrow mesenchymal stem cells (BMSCs). Hydrogels from decellularized extracellular matrix (dECM) preserve the biological compositions and functions of natural ECM, which can provide tissue-specific cues to regulate phenotypic expression and cell fate. It is unknown, however, whether hydrogels from periosteum can serve as pro-osteogenic carriers of hUCMSCs. Herein, a decellularized periosteum-derived hydrogel (dPH) was fabricated to reveal the effects of periosteum-specific cues on the bioactivities of hUCMSCs. A widely used non-bone/periosteum-derived ECM hydrogel product, Matrigel, was used as the control group. After decellularization, the absence of nuclei in the histological analysis indicated a successful removal of cellular components, which was also confirmed by DNA content quantification. The storage modulus of dPH increased (from 164.49 ± 29.92 Pa to 855.20 ± 20.67 Pa) with increasing concentration (from 0.5% to 1%). With a highly porous, fibrous microstructure, dPH had a more hydrophilic surface than Matrigel, of which the water contact angle reduced 62.62 ± 0.04%. Furthermore, dPH prominently promoted the initial cellular spreading with a significantly higher cell surface area (1.47-fold), cell spreading length (1.45-fold) and proliferation (approximately 1.05–1.13-fold) of hUCMSCs than those of Matrigel. Additionally, dPH was conducive to cell migration, whereas no cells migrated to Matrigel in the Transwell model. Compared with those of the Matrigel group, the osteogenesis-related genes expression levels (runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OCN)) and mineralized matrix formation (9.74-fold) of the hUCMSCs significantly increased in the dPH group. Our study indicated that dPH could provide a pro-osteogenic microenvironment for hUCMSCs, thereby revealing a promising application potential to repair bone defects.

Transplantation of SDF-1α-loaded liver extracellular matrix repopulated with autologous cells attenuated liver fibrosis in a rat model

Cell-based therapy and tissue engineering are promising substitutes for liver transplantation to cure end-stage liver disorders. However, the limited sources for healthy and functional cells and poor engraftment rate are main challenges to the cell-based therapy approach. On the other hand, feasibility of production and size of bioengineered tissues are primary bottlenecks in tissue engineering. Here, we induce regeneration in a rat fibrotic liver model by transplanting a natural bioengineered scaffold with a native microenvironment repopulated with autologous stem/progenitor cells. In the main experimental group, a 1 mm³ stromal derived factor-1α (SDF-1α; S) loaded scaffold from decellularized liver extracellular matrix (LEM) was transplanted (Tx) into a fibrotic liver and the endogenous stem/progenitor cells were mobilized via granulocyte colony stimulating factor (G-CSF; G) therapy. Four weeks after transplantation, changes in liver fibrosis and necrosis, efficacy of cell engraftment and differentiation, vasculogenesis, and liver function recovery were assessed in this (LEM-TxSG) group and compared to the other groups. We found significant reduction in liver fibrosis stage in the LEM-TxSG, LEM-TxS and LEM-TxG groups compared to the control (fibrotic) group. Liver necrosis grade, and alanine transaminase (ALT) and aspartate transaminase (AST) levels dramatically reduced in all experimental groups compared to the control group. However, the number of engrafted cells into the transplanted scaffold and ratio of albumin (Alb) positive cells per total incorporated cells were considerably higher in the LEM-TxSG group compared to the LEM-Tx, LEM-TxS and LEM-TxG groups. Serum Alb levels increased in the LEM-Tx, LEM-TxS, and LEM-TxG groups, and was highest in the LEM-TxSG group, which was significantly more than the fibrotic group. Small vessel formation in the LEM-TxSG group was significantly higher than the LEM-Tx and LEM-TxS groups. Totally, these findings support application of the in vivo tissue engineering approach as a possible novel therapeutic strategy for liver fibrosis.

Injection laryngoplasty of human adipose-derived stem cell spheroids with hyaluronic acid-based hydrogel improves the morphological and functional characteristics of geriatric larynx

Aim

As the geriatric population increased, the need of treatment for laryngeal atrophy and dysfunction increased. This study was performed to evaluate the effects of injection of human adipose-derived stem cell (hASC) spheroid-loaded catechol-conjugated hyaluronic acid (HA-CA) hydrogel on therapeutic rejuvenation of the geriatric larynx.

Methods

Stem cell spheroids with hyaluronic acid-based hydrogel were injected into the laryngeal muscles of 18-month-old Sprague–Dawley rats. The effects of hASC spheroids were examined in the following four groups: SHAM, injected with PBS; GEL, injected with HA-CA hydrogel; MONO, injected with single hASCs in HA-CA hydrogel; and SP, injected with hASCs spheroids in HA-CA hydrogel. The rejuvenation efficacy in geriatric laryngeal muscle tissues at 12 weeks postinjection was evaluated and compared by histology, immunofluorescence staining, and functionality analysis.

Results

Total myofiber cross-sectional area and myofiber number/density, evaluated by detection of myosin heavy chain with antibodies against laminin and fast myosin heavy chain, were significantly higher in the SP group than in the other groups. The lamina propria of the larynx was evaluated by alcian blue staining, which showed that the HA was increased significantly in the SP group compared to the other groups. In functional analysis, the glottal gap area was significantly reduced in the SP group compared to the other groups. The phase difference in the vocal fold during vibration was also smaller in the SP group than in the other groups, but the difference did not reach statistical significance.

Conclusion

Injection of hASC spheroids with hyaluronic acid-based hydrogel improves the morphological and functional characteristics of geriatric larynx.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00261-x.

Review on Multicomponent Hydrogel Bioinks Based on Natural Biomaterials for Bioprinting 3D Liver Tissues

Three-dimensional (3D)-printed in vitro tissue models have been used in various biomedical fields owing to numerous advantages such as enhancements in cell response and functionality. In liver tissue engineering, several studies have been reported using 3D-printed liver tissue models with improved cellular responses and functions in drug screening, liver disease, and liver regenerative medicine. However, the application of conventional single-component bioinks for the printing of 3D in vitro liver constructs remains problematic because of the complex structural and physiological characteristics of the liver. The use of multicomponent bioinks has become an attractive strategy for bioprinting 3D functional in vitro liver tissue models because of the various advantages of multicomponent bioinks, such as improved mechanical properties of the printed tissue construct and cell functionality. Therefore, it is essential to review various 3D bioprinting techniques and multicomponent hydrogel bioinks proposed for liver tissue engineering to suggest future directions for liver tissue engineering. Accordingly, we herein review multicomponent bioinks for 3D-bioprinted liver tissues. We first describe the fabrication methods capable of printing multicomponent bioinks and introduce considerations for bioprinting. We subsequently categorize and evaluate the materials typically utilized for multicomponent bioinks based on their characteristics. In addition, we also review recent studies for the application of multicomponent bioinks to fabricate in vitro liver tissue models. Finally, we discuss the limitations of current studies and emphasize aspects that must be resolved to enhance the future applicability of such bioinks.

Influence of Liver Extracellular Matrix in Predicting Drug-Induced Liver Injury: An Alternate Paradigm

In vitro drug-induced liver injury (DILI) models are promising tools for drug development to predict adverse events during clinical usage. However, the currently available DILI models are not specific or not able to predict the injury accurately. This is believed to be mainly because of failure to conserve the hepatocyte phenotype, lack of longevity, and difficulty in maintaining the tissue-specific microenvironment. In this study, we have assessed the potential of decellularized liver extracellular matrix (DLM) in retaining the hepatic cellular phenotype and functionality in the presence of a tissue-specific microenvironment along with its role in influencing the effect of the drug on hepatic cells. We show that DLM helps maintain the phenotype of the hepatic cell line HepG2, a well-known cell line for secretion of human proteins that is easily available. Also, the DLM enhanced the expression of a metabolic marker carbamoyl phosphate synthetase I (CPS1), a regulator of urea cycle, and bile salt export pump (BSEP), a marker of hepatocyte polarity. We further validated the DLM for its influence on the sensitivity of cells toward different classes of drugs. Interestingly, the coculture model, in the presence of endothelial cells and stellate cells, exhibited a higher sensitivity for both acetaminophen and trovafloxacin, a toxic compound that does not show any toxicity on preclinical screening. Thus, our results demonstrate for the first time that a multicellular combination along with DLM can be a potential and reliable DILI model to screen multiple drugs.

Expanding the Repertoire of Electrospinning: New and Emerging Biopolymers, Techniques, and Applications

Electrospinning has emerged as a versatile and accessible technology for fabricating polymer fibers, particularly for biological applications. Natural polymers or biopolymers (including synthetically derivatized natural polymers) represent a promising alternative to synthetic polymers, as materials for electrospinning. Many biopolymers are obtained from abundant renewable sources, are biodegradable, and possess inherent biological functions. This review surveys recent literature reporting new fibers produced from emerging biopolymers, highlighting recent developments in the use of sulfated polymers (including carrageenans and glycosaminoglycans), tannin derivatives (condensed and hydrolyzed tannins, tannic acid), modified collagen, and extracellular matrix extracts. The proposed advantages of these biopolymer-based fibers, focusing on their biomedical applications, are also discussed to highlight the use of new and emerging biopolymers (or new modifications to well-established ones) to enhance or achieve new properties for electrospun fiber materials.

Organotypic and Microphysiological Human Tissue Models for Drug Discovery and Development-Current State-of-the-Art and Future Perspectives

The number of successful drug development projects has been stagnant for decades despite major breakthroughs in chemistry, molecular biology, and genetics. Unreliable target identification and poor translatability of preclinical models have been identified as major causes of failure. To improve predictions of clinical efficacy and safety, interest has shifted to three-dimensional culture methods in which human cells can retain many physiologically and functionally relevant phenotypes for extended periods of time. Here, we review the state of the art of available organotypic culture techniques and critically review emerging models of human tissues with key importance for pharmacokinetics, pharmacodynamics, and toxicity. In addition, developments in bioprinting and microfluidic multiorgan cultures to emulate systemic drug disposition are summarized. We close by highlighting important trends regarding the fabrication of organotypic culture platforms and the choice of platform material to limit drug absorption and polymer leaching while supporting the phenotypic maintenance of cultured cells and allowing for scalable device fabrication. We conclude that organotypic and microphysiological human tissue models constitute promising systems to promote drug discovery and development by facilitating drug target identification and improving the preclinical evaluation of drug toxicity and pharmacokinetics. There is, however, a critical need for further validation, benchmarking, and consolidation efforts ideally conducted in intersectoral multicenter settings to accelerate acceptance of these novel models as reliable tools for translational pharmacology and toxicology. SIGNIFICANCE STATEMENT: Organotypic and microphysiological culture of human cells has emerged as a promising tool for preclinical drug discovery and development that might be able to narrow the translation gap. This review discusses recent technological and methodological advancements and the use of these systems for hit discovery and the evaluation of toxicity, clearance, and absorption of lead compounds.

3D-printed dermis-specific extracellular matrix mitigates scar contraction via inducing early angiogenesis and macrophage M2 polarization

Scar contraction frequently happens in patients with deep burn injuries. Hitherto, porcine dermal extracellular matrix (dECM) has supplied microenvironments that assist in wound healing but fail to inhibit scar contraction. To overcome this drawback, we integrate dECM into three-dimensional (3D)-printed dermal analogues (PDA) to prevent scar contraction. We have developed thermally gelled, non-rheologically modified dECM powder (dECMp) inks and successfully transformed them into PDA that was endowed with a micron-scale spatial structure. The optimal crosslinked PDA exhibited desired structure, good mechanical properties as well as excellent biocompatibility. Moreover, in vivo experiments demonstrated that PDA could significantly reduced scar contraction and improved cosmetic upshots of split thickness skin grafts (STSG) than the commercially available dermal templates and STSG along. The PDA has also induced an early, intense neovascularization, and evoked a type-2-like immune response. PDA's superior beneficial effects may attribute to their desired porous structure, the well-balanced physicochemical properties, and the preserved dermis-specific ECM cues, which collectively modulated the expression of genes such as Wnt11, ATF3, and IL1β, and influenced the crucial endogenous signalling pathways. The findings of this study suggest that PDA is a clinical translatable material that possess high potential in reducing scar contraction.

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Current dermal analogues have supplied microenvironments that assist in wound healing but cannot inhibit scar contraction.

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dECMp ink was formulated and transformed into PDA endowed with a micron-scale designed spatial structure.

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The PDAs were neatly superior to split thickness skin grafts and commercial dermal templates in hindering scar contraction.

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The transcriptome data may reveal how at the molecular level the IS and skin wounds respond to biomaterial stimuli.

Formation of 3D tissues of primary hepatocytes using fibrillized collagen microparticles as intercellular binders

Numerous attempts have been made to organize isolated primary hepatocytes into functional three-dimensional (3D) constructs, but technologies to introduce extracellular matrix (ECM) components into such assemblies have not been fully developed. Here we report a new approach to forming hepatocyte-based 3D tissues using fibrillized collagen microparticles (F-CMPs) as intercellular binders. We created thick tissues with a thickness of ∼200 μm simply by mixing F-CMPs with isolated primary rat hepatocytes and culturing them in cell culture inserts. Owing to the incorporated F-CMPs, the circular morphology of the formed tissues was stabilized, which was strong enough to be manually manipulated and retrieved from the chamber of the insert. We confirmed that the F-CMPs dramatically improved the cell viability and hepatocyte-specific functions such as albumin production and urea synthesis in the formed tissues. The presented approach provides a versatile strategy for hepatocyte-based tissue engineering, and will have a significant impact on biomedical applications and pharmaceutical research.

Elucidating Extracellular Matrix and Stiffness Control of Primary Human Hepatocyte Phenotype Via Cell Microarrays

How the liver's extracellular matrix (ECM) protein composition and stiffness cooperatively regulate primary human hepatocyte (PHH) phenotype is unelucidated. Here, we utilize protein microarrays and high content imaging with single-cell resolution to assess PHH attachment/functions on 10 major liver ECM proteins in single and two-way combinations robotically spotted onto polyacrylamide gels of 1 kPa or 25 kPa stiffness. Albumin, cytochrome-P450 3A4 (CYP3A4), and hepatocyte nuclear factor alpha (HNF4α) positively correlate with each other and cell density on both stiffnesses. The 25 kPa stiffness supports higher average albumin and HNF4α expression after 14 days, while ECM protein composition significantly modulates PHH functions across both stiffnesses. Unlike previous rodent data, PHH functions are highest only when collagen-IV or fibronectin are mixed with specific proteins, whereas non-collagenous proteins without mixed collagens downregulate functions. Combination of collagen-IV and hyaluronic acid retains high CYP3A4 on 1 kPa, whereas collagens-IV and -V better retain HNF4α on 25 kPa over 14 days. Adapting ECM conditions to 96-well plates containing conjugated hydrogels reveals novel regulation of other functions (urea, CYP1A2/2A6/2C9) and drug-mediated CYP induction by the ECM protein composition/stiffness. This high-throughput pipeline can be adapted to elucidate ECM's role in liver diseases and facilitate optimization of engineered tissues.

Functional Recellularization of Acellular Rat Liver Scaffold by Induced Pluripotent Stem Cells: Molecular Evidence for Wnt/B-Catenin Upregulation

BACKGROUND

Liver transplantation remains the only viable therapy for liver failure but has a severely restricted utility. Here, we aimed to decellularize rat livers to form acellular 3D bio-scaffolds suitable for seeding with induced pluripotent cells (iPSCs) as a tool to investigate the role of Wnt/β-catenin signaling in liver development and generation.

METHODS

Dissected rat livers were randomly divided into three groups: I (control); II (decellularized scaffolds) and III (recellularized scaffolds). Liver decellularization was established via an adapted perfusion procedure and assessed through the measurement of extracellular matrix (ECM) proteins and DNA content. Liver recellularization was assessed through histological examination and measurement of transcript levels of Wnt/β-catenin pathway, hepatogenesis, liver-specific microRNAs and growth factors essential for liver development. Adult rat liver decellularization was confirmed by the maintenance of ECM proteins and persistence of growth factors essential for liver regeneration.

RESULTS

iPSCs seeded rat decellularized livers displayed upregulated transcript expression of Wnt/β-catenin pathway-related, growth factors, and liver specification genes. Further, recellularized livers displayed restored liver-specific functions including albumin secretion and urea synthesis.

CONCLUSION

This establishes proof-of-principle for the generation of three-dimensional liver organ scaffolds as grafts and functional re-establishment.

Characterization Methods of Acellularized Tissue and Organs

The extracellular matrix (ECM) of mammalian organs and tissues has been applied as a substitute scaffold to simplify the restoration and reconstruction of several tissues. Such scaffolds are prepared in various arrangements including sheets, powders, and hydrogels. One of the more applicable processes is using natural scaffolds, for this purpose discarded tissues or organs are naturally derived by processes that comprised decellularization of following tissues or organs. Protection of the complex structure and 3D (three dimensional) ultrastructure of the ECM is extremely necessary but it is predictable that all protocols of decellularization end in disruption of the architecture and potential loss of surface organization and configuration. Tissue decellularization with conservation of ECM bioactivity and integrity can be improved by providing well-designed protocols regarding the agents and decellularization techniques operated during processing. An overview of the characterization of decellularized scaffolds and the role of reagnets can validate the applied methods' efficacy.

Tissue Engineering in Skin Substitute

Thermal injuries may cause significant damage to large areas of the skin. Extensive and deep burn wounds require specialized therapy. The optimal method in the strategy of treating extensive, full thickness burns (III°) is the use of autologous split thickness skin grafts STSG (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalized patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017). The main limitation of that method is the inadequate amount of healthy, undamaged skin (donor sites), which could be harvested and used as a graft. Moreover, donor sites are an additional wounds that require analgesic therapy, leave scars during the healing process and they are highly susceptible to infection (1-6). It must be emphasized that in terms of the treatment of severe, deep and extensive burns, and there should be no doubt that the search for a biocompatible skin substitute that would be able to replace autologous STSG is an absolute priority. The above-mentioned necessitates the search for new treatment methods of severe burn wounds. Such methods could consider the preparation and application of bioengineered, natural skin substitutes. At present, as the clinical standard considered by the physicians may be use of available biological skin substitutes, e.g., human allogeneic skin, in vitro cultured skin cells, acellular dermal matrix ADM and revitalized ADMs, etc. (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalised patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017; Łabuś et al. FebJ Biomed Mater Res B Appl Biomater 106:726-733, 2018).

Integrated 3D Printing-Based Framework-A Strategy to Fabricate Tubular Structures with Mechanocompromised Hydrogels

Several hollow organs perform various crucial functions in the body and must be replaced, repaired, or augmented in many disease conditions. Fabrication of tissue analogues to these hollow organs is incredibly challenging. Still, recent advancements in biofabrication have allowed researchers to pursue the development of several hollow organs such as blood vessels, esophagus, trachea, urethra, and others. Materials like collagen, alginate, elastin, silk, fibrin, etc., have been predominantly used for organ development. However, the focus has been duly shifted toward decellularized extracellular matrix (dECM) to develop tissue-specific hydrogels because they provide relevant biochemical cues to promote cellular activity. Still, the dECM-based hydrogels are mechanically weak to fabricate self-supporting tubular structures. Here, an innovative approach using the stereolithography apparatus (SLA) 3D printed framework has been implemented to achieve a self-supporting tubular structure using caprine esophagus muscle dECM hydrogel. A significant improvement in the mechanical stability of the biofabricated tissue has been observed within 7 days of culture. Interestingly, the encapsulated L929 mouse fibroblasts transdifferentiated into myofibroblasts because of the cues provided by the muscle dECM. Overall, the potential of an SLA-based 3D printing strategy to fabricate frameworks, especially for fabricating tubular organs/tissues using mechanocompromised hydrogel, has been demonstrated here.

Photocrosslinkable liver extracellular matrix hydrogels for the generation of 3D liver microenvironment models

Liver extracellular matrix (ECM)-based hydrogels have gained considerable interest as biomimetic 3D cell culture environments to investigate the mechanisms of liver pathology, metabolism, and toxicity. The preparation of current liver ECM hydrogels, however, is based on time-consuming thermal gelation and limits the control of mechanical properties. In this study, we used detergent-based protocols to produce decellularized porcine liver ECM, which in turn were solubilized and functionalized with methacrylic anhydride to generate photocrosslinkable methacrylated liver ECM (LivMA) hydrogels. Firstly, we explored the efficacy of two protocols to decellularize porcine liver tissue using varying combinations of commonly used chemical agents such as Triton X-100, Sodium Dodecyl Sulphate (SDS) and Ammonium hydroxide. Then, we demonstrated successful formation of stable, reproducible LivMA hydrogels from both the protocols by photocrosslinking. The LivMA hydrogels obtained from the two decellularization protocols showed distinct mechanical properties. The compressive modulus of the hydrogels was directly dependent on the hydrogel concentration, thereby demonstrating the tuneability of mechanical properties of these hydrogels. Immortalized Human Hepatocytes cells were encapsulated in the LivMA hydrogels and cytocompatibility of the hydrogels was demonstrated after one week of culture. In summary, the LivMA hydrogel system provides a simple, photocrosslinkable platform, which can potentially be used to simulate healthy versus damaged liver for liver disease research, drug studies and cancer metastasis modelling.

Upgrading Hepatic Differentiation and Functions on 3D Printed Silk-Decellularized Liver Hybrid Scaffolds

We developed hybrid liver-specific three-dimensional (3D) printed scaffolds using a solubilized native decellularized liver (DCL) matrix and silk fibroin (SF) and investigated their ability to support functional cultures of hepatic cells. Rat livers were decellularized by perfusing detergents via the portal vein, solubilized using pepsin to form DCL, and characterized. SF blended with gelatin (8% w/v) was optimized with varying percentages of DCL to obtain silk gelatin-DCL bioink (SG-DCL). Different compositions of SG-DCL were studied by rheology for optimum versatility and print fidelity. 3D printed six-layered scaffolds were fabricated using a sophisticated direct-write 3D bioprinter. Huh7 cells were cultured on the 3D printed scaffolds for 3 weeks. 3D printed SG scaffolds without DCL along with 2D films (SG and SG-DCL) and 2D culture on tissue culture Petri dish control were used for comparative studies. The DCL matrix showed the absence of cells in histology and SEM. The combined SG-DCL ink at all of the studied DCL percentages (1-10%) revealed shear-thinning behavior in the printable range. The storage modulus value for the SG-DCL ink at all DCL percentages was higher than the loss modulus. In comparison to 2D controls, hepatic cells cultured on 3D SG-DCL revealed increased proliferation until 2 weeks and an upregulated expression of hepatocyte markers, including asialoglycoprotein receptor 1 (ASGR1). The Wnt pathway gene β-catenin was upregulated by more than 4-fold in 3D SG-DCL on day 3, while it showed a decline on day 7 as compared to 3D SG and also 2D controls. The expression of the epithelial cell adhesion molecule (EpCAM) was however lower in both 2D SG-DCL (2-fold) and 3D SG-DCL (2.5-fold) as compared to that in 2D controls. Immunofluorescence studies validated the protein expression of ASGR1 in 3D SG-DCL. Albumin (ALB) was not identified on SG scaffolds but prominently expressed in 3D SG-DCL constructs. In comparison to 2D SG, both ALB (1.8-fold) and urea (5-fold) were enhanced in cells cultured on 3D SG-DCL on day 7 of culture. Hence, the SG-DCL 3D printed scaffolds provide a conducive microenvironment for elevating differentiation and functions of hepatic cells possibly through an involvement of the Wnt/β-catenin signaling pathway.

Printing 3D vagina tissue analogues with vagina decellularized extracellular matrix bioink

A variety of factors can cause vaginal loss. The patients are suffering from great psychological and physical pain, and there is an urgent need for vagina reconstruction. 3D-bioprinting is expected to achieve vaginal morphological restoration and true functional reconstruction. The current study aimed to explore the biomimetic 3D vagina tissue printing with acellular vagina matrix (AVM) bioink. The AVM from pig was converted to bioink by 15% gelatin and 3% sodium alginate mixed with the AVM solution. Rheology, scanning electron microscopy and HE staining were performed to characterize the bioink's viscosity, morphologies and biocompatibility. After printing, the viability of bone marrow mesenchymal stem cells (BMSCs) in the printed 3D scaffolds in vitro was investigated by a live/dead assay kit. Then, subcutaneous transplantation in rats were divided randomly into 3D scaffold group and 3D scaffold encapsulating CM-Dil-labeled BMSCs group. The results of HE, immunohistochemistry and immunofluorescence staining revealed that 3D scaffold encapsulating BMSCs expressed significant effects on the vascularization and epithelization of the printed vagina tissue, and the BMSCs could acquire the phenotype of vaginal epithelial cells and endothelial-like cells. The work showed that the biomimetic 3D vagina tissue with AVM bioink encapsulating BMSCs is a promising approach for vagina reconstruction.

Osteogenesis of 3D-Printed PCL/TCP/bdECM Scaffold Using Adipose-Derived Stem Cells Aggregates; An Experimental Study in the Canine Mandible

Three-dimensional (3D) printing is perceived as an innovative tool for change in tissue engineering and regenerative medicine based on research outcomes on the development of artificial organs and tissues. With advances in such technology, research is underway into 3D-printed artificial scaffolds for tissue recovery and regeneration. In this study, we fabricated artificial scaffolds by coating bone demineralized and decellularized extracellular matrix (bdECM) onto existing 3D-printed polycaprolactone/tricalcium phosphate (PCL/TCP) to enhance osteoconductivity and osteoinductivity. After injecting adipose-derived stem cells (ADSCs) in an aggregate form found to be effective in previous studies, we examined the effects of the scaffold on ossification during mandibular reconstruction in beagle dogs. Ten beagles were divided into two groups: group A (PCL/TCP/bdECM + ADSC injection; n = 5) and group B (PCL/TCP/bdECM; n = 5). The results were analyzed four and eight weeks after intervention. Computed tomography (CT) findings showed that group A had more diffuse osteoblast tissue than group B. Evidence of infection or immune rejection was not detected following histological examination. Goldner trichrome (G/T) staining revealed rich ossification in scaffold pores. ColI, Osteocalcin, and Runx2 gene expressions were determined using real-time polymerase chain reaction. Group A showed greater expression of these genes. Through Western blotting, group A showed a greater expression of genes that encode ColI, Osteocalcin, and Runx2 proteins. In conclusion, intervention group A, in which the beagles received the additional ADSC injection together with the 3D-printed PCL/TCP coated with bdECM, showed improved mandibular ossification in and around the pores of the scaffold.

TMT-based quantitative proteome profiles reveal the memory function of a whole heart decellularized matrix for neural stem cell trans-differentiation into the cardiac lineage

Whole organ or tissue decellularized matrices are a promising scaffold for tissue engineering because they maintain the specific memory of the original organ or tissue. A whole organ or tissue decellularized matrix contains extracellular matrix (ECM) components, and exhibits ultrastructural and mechanical properties, which could significantly regulate the fate of stem cells. To better understand the memory function of whole organ decellularized matrices, we constructed a heart decellularized matrix and seeded cross-embryonic layer stem cells - neural stem cells (NSCs) to repopulate the matrix, engineering cardiac tissue, in which a large number of NSCs differentiated into the neural lineage, but besides that, NSCs showed an obvious tendency of trans-differentiating into cardiac lineage cells. The results demonstrated that the whole heart decellularized microenvironment possesses memory function. To reveal the underlying mechanism, TMT-based quantitative proteomics analysis was used to identify the differently expressed proteins in the whole heart decellularized matrix compared with a brain decellularized matrix. 937 of the proteins changed over 1.5 fold, with 573 of the proteins downregulated and 374 of the proteins upregulated, among which integrin ligands in the ECM serve as key signals in regulating NSC fate. The findings here provide a novel insight into the memory function of tissue-specific microenvironments and pave the way for the therapeutic application of personalized tissues.

Research progress in decellularized extracellular matrix-derived hydrogels

Decellularized extracellular matrix (dECM) is widely used in regenerative medicine as a scaffold material due to its unique biological activity and good biocompatibility. Hydrogel is a three-dimensional network structure polymer with high water content and high swelling that can simulate the water environment of human tissues, has good biocompatibility, and can exchange nutrients, oxygen, and waste with cells. At present, hydrogel is the ideal biological material for tissue engineering. In recent years, rapid development of the hydrogel theory and technology and progress in the use of dECM to form hydrogels have attracted considerable attention to dECM hydrogels as an innovative method for tissue engineering and regenerative medicine. This article introduces the classification of hydrogels, and focuses on the history and formation of dECM hydrogels, the source of dECM, the application of dECM hydrogels in tissue engineering and the commercial application of dECM materials.