Novel Strategies in Artificial Organ Development: What Is the Future of Medicine?

Artificial Cells and HepG2 Cells in 3D-Bioprinted Arrangements

Artificial cells are engineered units with cell-like functions for different purposes including acting as supportive elements for mammalian cells. Artificial cells with minimal liver-like function are made of alginate and equipped with metalloporphyrins that mimic the enzyme activity of a member of the cytochrome P450 family namely CYP1A2. The artificial cells are employed to enhance the dealkylation activity within 3D bioprinted structures composed of HepG2 cells and these artificial cells. This enhancement is monitored through the conversion of resorufin ethyl ether to resorufin. HepG2 cell aggregates are 3D bioprinted using an alginate/gelatin methacryloyl ink, resulting in the successful proliferation of the HepG2 cells. The composite ink made of an alginate/gelatin liquid phase with an increasing amount of artificial cells is characterized. The CYP1A2-like activity of artificial cells is preserved over at least 35 days, where 6 nM resorufin is produced in 8 h. Composite inks made of artificial cells and HepG2 cell aggregates in a liquid phase are used for 3D bioprinting. The HepG2 cells proliferate over 35 days, and the structure has boosted CYP1A2 activity. The integration of artificial cells and their living counterparts into larger 3D semi-synthetic tissues is a step towards exploring bottom-up synthetic biology in tissue engineering.

Characterization of a Chimeric Resilin-Elastin Structural Protein Dedicated to 3D Bioprinting as a Bioink Component

In this study we propose to use for bioprinting a bioink enriched with a recombinant RE15mR protein with a molecular weight of 26 kDa, containing functional sequences derived from resilin and elastin. The resulting protein also contains RGD sequences in its structure, as well as a metalloproteinase cleavage site, allowing positive interaction with the cells seeded on the construct and remodeling the structure of this protein in situ. The described protein is produced in a prokaryotic expression system using an E. coli bacterial strain and purified by a process using a unique combination of known methods not previously used for recombinant elastin-like proteins. The positive effect of RE15mR on the mechanical, physico-chemical, and biological properties of the print is shown in the attached results. The addition of RE15mR to the bioink resulted in improved mechanical and physicochemical properties and promoted the habitation of the prints by cells of the L-929 line.

Stem Cell-Based Strategies: The Future Direction of Bioartificial Liver Development

Acute liver failure (ALF) results from severe liver damage or end-stage liver disease. It is extremely fatal and causes serious health and economic burdens worldwide. Once ALF occurs, liver transplantation (LT) is the only definitive and recommended treatment; however, LT is limited by the scarcity of liver grafts. Consequently, the clinical use of bioartificial liver (BAL) has been proposed as a treatment strategy for ALF. Human primary hepatocytes are an ideal cell source for these methods. However, their high demand and superior viability prevent their widespread use. Hence, finding alternatives that meet the seed cell quality and quantity requirements is imperative. Stem cells with self-renewing, immunogenic, and differentiative capacities are potential cell sources. MSCs and its secretomes encompass a spectrum of beneficial properties, such as anti-inflammatory, immunomodulatory, anti-ROS (reactive oxygen species), anti-apoptotic, pro-metabolomic, anti-fibrogenesis, and pro-regenerative attributes. This review focused on the recent status and future directions of stem cell-based strategies in BAL for ALF. Additionally, we discussed the opportunities and challenges associated with promoting such strategies for clinical applications.

Effects of Addition of Lanthanum and Zinc Oxides on the Biological Properties of TiO2-SiO2-P2O5/CaO on Ion Exchange Resin for Bone Implantation

The spherical materials TiO2-SiO2-P2O5/CaO, TiO2-SiO2-P2O5/La2O3, and TiO2-SiO2-P2O5/ZnO deposited on the Tokem-250 cation exchanger have been synthesized with an alcoholic solution by the sol-gel method. The macroporous cation exchanger Tokem-250, which has high Ca2+, Zn2+, and La3+ ion selectivity, was used in the present study. This material has the ability to precipitate and mineralize calcium phosphates on its surface in biological media, since it has high porosity, a homogeneous structure with a uniform variation of elements, and the presence of active centers (Si4+, Ti4+) on the surface. The effect of lanthanum and zinc additives on biological properties has been studied. It was established that accumulation of Ca2+ and Mg2+ occurs faster on the surface of TiO2-SiO2-P2O5/ZnO in the SBF (simulated body fluid) model solution, showing higher reaction capacity. The amount of calcium and phosphorus ions on the surface of sample TiO2-SiO2-P2O5/La2O3 is greater due to the ability of lanthanum to coordinate a large number of ions (lanthanum coordination number is 10). The presence of zinc ions in the system causes the partial hemoglobin release from erythrocytes into the supernatant fluid. The samples with lanthanum ions reduce the amount of protein in plasma after incubation, which has a positive effect on the practical application.

A comprehensive overview of advanced dynamic in vitro intestinal and hepatic cell culture models

Orally administered drugs pass through the gastrointestinal tract before being absorbed in the small intestine and metabolised in the liver. To test the efficacy and toxicity of drugs, animal models are often employed; however, they are not suitable for investigating drug-tissue interactions and making reliable predictions, since the human organism differs drastically from animals in terms of absorption, distribution, metabolism and excretion of substances. Likewise, simple static in vitro cell culture systems currently used in preclinical drug screening often do not resemble the native characteristics of biological barriers. Dynamic models, on the other hand, provide in vivo-like cell phenotypes and functionalities that offer great potential for safety and efficacy prediction. Herein, current microfluidic in vitro intestinal and hepatic models are reviewed, namely single- and multi-tissue micro-bioreactors, which are associated with different methods of cell cultivation, i.e., scaffold-based versus scaffold-free.

Bioprinted 3D Bionic Scaffolds with Pancreatic Islets as a New Therapy for Type 1 Diabetes-Analysis of the Results of Preclinical Studies on a Mouse Model

Recently, tissue engineering, including 3D bioprinting of the pancreas, has acquired clinical significance and has become an outstanding potential method of customized treatment for type 1 diabetes mellitus. The study aimed to evaluate the function of 3D-bioprinted pancreatic petals with pancreatic islets in the murine model. A total of 60 NOD-SCID (Nonobese diabetic/severe combined immunodeficiency) mice were used in the study and divided into three groups: control group; IsletTx (porcine islets transplanted under the renal capsule); and 3D bioprint (3D-bioprinted pancreatic petals with islets transplanted under the skin, on dorsal muscles). Glucose, C-peptide concentrations, and histological analyses were performed. In the obtained results, significantly lower mean fasting glucose levels (mg/dL) were observed both in a 3D-bioprint group and in a group with islets transplanted under the renal capsule when compared with untreated animals. Differences were observed in all control points: 7th, 14th, and 28th days post-transplantation (129, 119, 118 vs. 140, 139, 140; p < 0.001). Glucose levels were lower on the 14th and 28th days in a group with bioprinted petals compared to the group with islets transplanted under the renal capsule. Immunohistochemical staining indicated the presence of secreted insulin-living pancreatic islets and neovascularization within 3D-bioprinted pancreatic petals after transplantation. In conclusion, bioprinted bionic petals significantly lowered plasma glucose concentration in studied model species.

An Overview on Image-Based and Scanner-Based 3D Modeling Technologies

Advances in the scientific fields of photogrammetry and computer vision have led to the development of automated multi-image methods that solve the problem of 3D reconstruction. Simultaneously, 3D scanners have become a common source of data acquisition for 3D modeling of real objects/scenes/human bodies. This article presents a comprehensive overview of different 3D modeling technologies that may be used to generate 3D reconstructions of outer or inner surfaces of different kinds of targets. In this context, it covers the topics of 3D modeling using images via different methods, it provides a detailed classification of 3D scanners by additionally presenting the basic operating principles of each type of scanner, and it discusses the problem of generating 3D models from scans. Finally, it outlines some applications of 3D modeling, beyond well-established topographic ones.

The rise of mechanical metamaterials: Auxetic constructs for skin wound healing

Auxetic materials are known for their unique ability to expand/contract in multiple directions when stretched/compressed. In other words, they exhibit a negative Poisson's ratio, which is usually positive for most of materials. This behavior appears in some biological tissues such as human skin, where it promotes wound healing by providing an enhanced mechanical support and facilitating cell migration. Skin tissue engineering has been a growing research topic in recent years, largely thanks to the rapid development of 3D printing techniques and technologies. The combination of computational studies with rapid manufacturing and tailored designs presents a huge potential for the future of personalized medicine. Overall, this review article provides a comprehensive overview of the current state of research on auxetic constructs for skin healing applications, highlighting the potential of auxetics as a promising treatment option for skin wounds. The article also identifies gaps in the current knowledge and suggests areas for future research. In particular, we discuss the designs, materials, manufacturing techniques, and also the computational and experimental studies on this topic.

Three-Dimensional (3D) Printing of Organs according to the Perspective of Islamic Law

The outburst of the fourth Industrial Revolution had a significant impact on many aspects of life. The discovery of new technologies in medicine has resulted in innovations: organ transplants. The introduction of three-dimensional (3D) organ printing technology promises improvements to the field. Organs such as the liver, kidneys, heart and others are printed to meet the needs of the actual organs. However, the production of prototype organs to replace the original organs is associated with the issue of changing the creation of Allah. Accordingly, this study will analyse the issue of changing the creation of God in three-dimensional (3D) organ printing technology according to the perspective of Islamic law. Several appropriate methodologies in Islamic law (usul fiqh) are used such as legal reasoning through maqasid shariah perspective and analogical reasoning. The result shows that three-dimensional (3D) organ printing technology falls under the permissible category of changing the creation of Allah because it can save human lives. The production of organs through 3D printing involving changes included in the category of necessity (daruri) and need (hajiy) is permissible, but the category of desirable (tahsini) requires further specifications.

Bioartificial livers: a review of their design and manufacture

Acute liver failure (ALF) is a rapidly progressive disease with high morbidity and mortality rates. Liver transplantation and artificial liver support systems, such as artificial livers (ALs) and bioartificial livers (BALs), are the two major therapies for ALF. Compared to ALs, BALs are composed of functional hepatocytes that provide essential liver functions, including detoxification, metabolite synthesis, and biotransformation. Furthermore, BALs can potentially provide effective support as a form of bridging therapy to liver transplantation or spontaneous recovery for patients with ALF. In this review, we systematically discussed the currently available state-of-the-art designs and manufacturing processes for BAL support systems. Specifically, we classified the cell sources and bioreactors that are applied in BALs, highlighted the advanced technologies of hepatocyte culturing and bioreactor fabrication, and discussed the current challenges and future trends in developing next generation BALs for large scale clinical applications.

3D-bioprinted cancer-on-a-chip: level-up organotypic in vitro models

Combinatorial conjugation of organ-on-a-chip platforms with additive manufacturing technologies is rapidly emerging as a disruptive approach for upgrading cancer-on-a-chip systems towards anatomic-sized dynamic in vitro models. This valuable technological synergy has potential for giving rise to truly physiomimetic 3D models that better emulate tumor microenvironment elements, bioarchitecture, and response to multidimensional flow dynamics. Herein, we showcase the most recent advances in bioengineering 3D-bioprinted cancer-on-a-chip platforms and provide a comprehensive discussion on design guidelines and possibilities for high-throughput analysis. Such hybrid platforms represent a new generation of highly sophisticated 3D tumor models with improved biomimicry and predictability of therapeutics performance.

Three-Dimensional Cell Cultures as a Research Platform in Lung Diseases and COVID-19

BACKGROUND

Chronic respiratory diseases (CRD) are a major public health problem worldwide. In the current epidemiological context, CRD have received much interest when considering their correlation with greater susceptibility to SARS-Cov-2 and severe disease (COVID-19). Increasingly more studies have investigated pathophysiological interactions between CRD and COVID-19.

AREA COVERED

Animal experimentation has decisively contributed to advancing our knowledge of CRD. Considering the increase in ethical restrictions in animal experimentation, researchers must focus on new experimental alternatives. Two-dimensional (2D) cell cultures have complemented animal models and significantly contributed to advancing research in the life sciences. However, 2D cell cultures have several limitations in studies of cellular interactions. Three-dimensional (3D) cell cultures represent a new and robust platform for studying complex biological processes and are a promising alternative in regenerative and translational medicine.

EXPERT OPINION

Three-dimensional cell cultures are obtained by combining several types of cells in integrated and self-organized systems in a 3D structure. These 3D cell culture systems represent an efficient methodological approach in studies of pathophysiology and lung therapy. More recently, complex 3D culture systems, such as lung-on-a-chip, seek to mimic the physiology of a lung in vivo through a microsystem that simulates alveolar-capillary interactions and exposure to air. The present review introduces and discusses 3D lung cultures as robust platforms for studies of the pathophysiology of CRD and COVID-19 and the mechanisms that underlie interactions between CRD and COVID-19.

3D Printing of Physical Organ Models: Recent Developments and Challenges

Physical organ models are the objects that replicate the patient-specific anatomy and have played important roles in modern medical diagnosis and disease treatment. 3D printing, as a powerful multi-function manufacturing technology, breaks the limitations of traditional methods and provides a great potential for manufacturing organ models. However, the clinical application of organ model is still in small scale, facing the challenges including high cost, poor mimicking performance and insufficient accuracy. In this review, the mainstream 3D printing technologies are introduced, and the existing manufacturing methods are divided into "directly printing" and "indirectly printing", with an emphasis on choosing suitable techniques and materials. This review also summarizes the ideas to address these challenges and focuses on three points: 1) what are the characteristics and requirements of organ models in different application scenarios, 2) how to choose the suitable 3D printing methods and materials according to different application categories, and 3) how to reduce the cost of organ models and make the process simple and convenient. Moreover, the state-of-the-art in organ models are summarized and the contribution of 3D printed organ models to various surgical procedures is highlighted. Finally, current limitations, evaluation criteria and future perspectives for this emerging area are discussed.

Stem Cells as a Source of Pancreatic Cells for Production of 3D Bioprinted Bionic Pancreas in the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is the third most common autoimmune disease which develops due to genetic and environmental risk factors. Often, intensive insulin therapy is insufficient, and patients require a pancreas or pancreatic islets transplant. However, both solutions are associated with many possible complications, including graft rejection. The best approach seems to be a donor-independent T1D treatment strategy based on human stem cells cultured in vitro and differentiated into insulin and glucagon-producing cells (β and α cells, respectively). Both types of cells can then be incorporated into the bio-ink used for 3D printing of the bionic pancreas, which can be transplanted into T1D patients to restore glucose homeostasis. The aim of this review is to summarize current knowledge about stem cells sources and their transformation into key pancreatic cells. Last, but not least, we comment on possible solutions of post-transplant immune response triggered stem cell-derived pancreatic cells and their potential control mechanisms.

Bionic Organs: Shear Forces Reduce Pancreatic Islet and Mammalian Cell Viability during the Process of 3D Bioprinting

Background: 3D bioprinting is the future of constructing functional organs. Creating a bioactive scaffold with pancreatic islets presents many challenges. The aim of this paper is to assess how the 3D bioprinting process affects islet viability. Methods: The BioX 3D printer (Cellink), 600 μm inner diameter nozzles, and 3% (w/v) alginate cell carrier solution were used with rat, porcine, and human pancreatic islets. Islets were divided into a control group (culture medium) and 6 experimental groups (each subjected to specific pressure between 15 and 100 kPa). FDA/PI staining was performed to assess the viability of islets. Analogous studies were carried out on α-cells, β-cells, fibroblasts, and endothelial cells. Results: Viability of human pancreatic islets was as follows: 92% for alginate-based control and 94%, 90%, 74%, 48%, 61%, and 59% for 15, 25, 30, 50, 75, and 100 kPa, respectively. Statistically significant differences were observed between control and 50, 75, and 100 kPa, respectively. Similar observations were made for porcine and rat islets. Conclusions: Optimal pressure during 3D bioprinting with pancreatic islets by the extrusion method should be lower than 30 kPa while using 3% (w/v) alginate as a carrier.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part II: Systems and Applications

In this second part of our systematic review on the research area of 3D cell culture in micro-bioreactors we give a detailed description of the published work with regard to the existing micro-bioreactor types and their applications, and highlight important results gathered with the respective systems. As an interesting detail, we found that micro-bioreactors have already been used in SARS-CoV research prior to the SARS-CoV2 pandemic. As our literature research revealed a variety of 3D cell culture configurations in the examined bioreactor systems, we defined in review part one “complexity levels” by means of the corresponding 3D cell culture techniques applied in the systems. The definition of the complexity is thereby based on the knowledge that the spatial distribution of cell-extracellular matrix interactions and the spatial distribution of homologous and heterologous cell–cell contacts play an important role in modulating cell functions. Because at least one of these parameters can be assigned to the 3D cell culture techniques discussed in the present review, we structured the studies according to the complexity levels applied in the MBR systems.