Regulation of Human Pluripotent Stem Cell-Derived Hepatic Cell Phenotype by Three-Dimensional Hydrogel Models

Decellularized liver scaffolds for constructing drug-metabolically functional ex vivo human liver models

The creation of ex vivo human liver models has long been a critical objective in academic, clinical, and pharmaceutical research, particularly for drug development, where accurate evaluation of hepatic metabolic dynamics is crucial. We have developed a bioengineered, perfused, organ-level human liver model that accurately replicates key liver functions, including metabolic activities, and protein synthesis, thus addressing some of the limitations associated with traditional liver monolayers, organoids, and matrix-embedded liver cells. Our approach utilizes liver-specific biomatrix scaffolds, prepared using an innovative protocol and fortified with matrix components that facilitate cellular interactions. These scaffolds, when seeded with human fetal liver cells or co-seeded with liver parenchymal and endothelial cell lines, enable the formation of three-dimensional (3D) human livers with enhanced cellular organization. The "recellularized tissue-engineered livers" (RCLs) have undergone various analyses, demonstrating the capability for establishing liver microenvironments ex vivo. Within 7-14 days, the RCLs exhibit evidence of liver differentiation and metabolic capabilities, underscoring the potential for use in drug metabolism and toxicity studies. Although our study represents a significant step forward, we acknowledge the need for direct comparisons with existing models and further research to fully elucidate the spectrum of regenerative responses. The high drug-metabolizing enzyme activity of RCLs, as demonstrated in our study, provides a promising avenue for investigating drug-induced liver injury mechanisms, contributing to a more detailed understanding of early drug discovery processes.

Advances in drug-induced liver injury research: in vitro models, mechanisms, omics and gene modulation techniques

Drug-induced liver injury (DILI) refers to drug-mediated damage to the structure and function of the liver, ranging from mild elevation of liver enzymes to severe hepatic insufficiency, and in some cases, progressing to liver failure. The mechanisms and clinical symptoms of DILI are diverse due to the varying combination of drugs, making clinical treatment and prevention complex. DILI has significant public health implications and is the primary reason for post-marketing drug withdrawals. The search for reliable preclinical models and validated biomarkers to predict and investigate DILI can contribute to a more comprehensive understanding of adverse effects and drug safety. In this review, we examine the progress of research on DILI, enumerate in vitro models with potential benefits, and highlight cellular molecular perturbations that may serve as biomarkers. Additionally, we discuss omics approaches frequently used to gather comprehensive datasets on molecular events in response to drug exposure. Finally, three commonly used gene modulation techniques are described, highlighting their application in identifying causal relationships in DILI. Altogether, this review provides a thorough overview of ongoing work and approaches in the field of DILI.

Bioinks for bioprinting using plant-derived biomaterials

Three-dimensional (3D) bioprinting has revolutionized tissue engineering by enabling the fabrication of complex and functional human tissues and organs. An essential component of successful 3D bioprinting is the selection of an appropriate bioink capable of supporting cell proliferation and viability. Plant-derived biomaterials, because of their abundance, biocompatibility, and tunable properties, hold promise as bioink sources, thus offering advantages over animal-derived biomaterials, which carry immunogenic concerns. This comprehensive review explores and analyzes the potential of plant-derived biomaterials as bioinks for 3D bioprinting of human tissues. Modification and optimization of these materials to enhance printability and biological functionality are discussed. Furthermore, cancer research and drug testing applications of the use of plant-based biomaterials in bioprinting various human tissues such as bone, cartilage, skin, and vascular tissues are described. Challenges and limitations, including mechanical integrity, cell viability, resolution, and regulatory concerns, along with potential strategies to overcome them, are discussed. Additionally, this review provides insights into the potential use of plant-based decellularized ECM (dECM) as bioinks, future prospects, and emerging trends in the use of plant-derived biomaterials for 3D bioprinting applications. The potential of plant-derived biomaterials as bioinks for 3D bioprinting of human tissues is highlighted herein. However, further research is necessary to optimize their processing, standardize their properties, and evaluate their long-termin vivoperformance. Continued advancements in plant-derived biomaterials have the potential to revolutionize tissue engineering and facilitate the development of functional and regenerative therapies for diverse clinical applications.

Animal-derived products in science and current alternatives

More than fifty years after the 3Rs definition and despite the continuous implementation of regulatory measures, animals continue to be widely used in basic research. Their use comprises not only in vivo experiments with animal models, but also the production of a variety of supplements and products of animal origin for cell and tissue culture, cell-based assays, and therapeutics. The animal-derived products most used in basic research are fetal bovine serum (FBS), extracellular matrix proteins such as Matrigel™, and antibodies. However, their production raises several ethical issues regarding animal welfare. Additionally, their biological origin is associated with a high risk of contamination, resulting, frequently, in poor scientific data for clinical translation. These issues support the search for new animal-free products able to replace FBS, Matrigel™, and antibodies in basic research. In addition, in silico methodologies play an important role in the reduction of animal use in research by refining the data previously to in vitro and in vivo experiments. In this review, we depicted the current available animal-free alternatives in in vitro research.

Comparison of two supporting matrices for patient-derived cancer cells in 3D drug sensitivity and resistance testing assay (3D-DSRT)

Central to the success of functional precision medicine of solid tumors is to perform drug testing of patient-derived cancer cells (PDCs) in tumor-mimicking ex vivo conditions. While high throughput (HT) drug screening methods have been well-established for cells cultured in two-dimensional (2D) format, this approach may have limited value in predicting clinical responses. Here, we describe the results of the optimization of drug sensitivity and resistance testing (DSRT) in three-dimensional (3D) growth supporting matrices in a HT mode (3D-DSRT) using the hepatocyte cell line (HepG2) as an example. Supporting matrices included widely used animal-derived Matrigel and cellulose-based hydrogel, GrowDex, which has earlier been shown to support 3D growth of cell lines and stem cells. Further, the sensitivity of ovarian cancer PDCs, from two patients included in the functional precision medicine study, was tested for 52 drugs in 5 different concentrations using 3D-DSRT. Shortly, in the optimized protocol, the PDCs are embedded with matrices and seeded to 384-well plates to allow the formation of the spheroids prior to the addition of drugs in nanoliter volumes with acoustic dispenser. The sensitivity of spheroids to drug treatments is measured with cell viability readout (here, 72 h after addition of drugs). The quality control and data analysis are performed with openly available Breeze software. We show the usability of both matrices in established 3D-DSRT, and report 2D vs 3D growth condition dependent differences in sensitivities of ovarian cancer PDCs to MEK-inhibitors and cytotoxic drugs. This study provides a proof-of-concept for robust and fast screening of drug sensitivities of PDCs in 3D-DSRT, which is important not only for drug discovery but also for personalized ex vivo drug testing in functional precision medicine studies. These findings suggest that comparing results of 2D- and 3D-DSRT is essential for understanding drug mechanisms and for selecting the most effective treatment for the patient.

Patient-Derived Multiple Myeloma 3D Models for Personalized Medicine-Are We There Yet?

Despite the wide variety of existing therapies, multiple myeloma (MM) remains a disease with dismal prognosis. Choosing the right treatment for each patient remains one of the major challenges. A new approach being explored is the use of ex vivo models for personalized medicine. Two-dimensional culture or animal models often fail to predict clinical outcomes. Three-dimensional ex vivo models using patients' bone marrow (BM) cells may better reproduce the complexity and heterogeneity of the BM microenvironment. Here, we review the strengths and limitations of currently existing patient-derived ex vivo three-dimensional MM models. We analyze their biochemical and biophysical properties, molecular and cellular characteristics, as well as their potential for drug testing and identification of disease biomarkers. Furthermore, we discuss the remaining challenges and give some insight on how to achieve a more biomimetic and accurate MM BM model. Overall, there is still a need for standardized culture methods and refined readout techniques. Including both myeloma and other cells of the BM microenvironment in a simple and reproducible three-dimensional scaffold is the key to faithfully mapping and examining the relationship between these players in MM. This will allow a patient-personalized profile, providing a powerful tool for clinical and research applications.

A quick pipeline for the isolation of 3D cell culture-derived extracellular vesicles

Recent advances in cell biology research regarding extracellular vesicles have highlighted an increasing demand to obtain 3D cell culture-derived EVs, because they are considered to more accurately represent EVs obtained in vivo. However, there is still a grave need for efficient and tunable methodologies to isolate EVs from 3D cell cultures. Using nanofibrillar cellulose (NFC) scaffold as a 3D cell culture matrix, we developed a pipeline of two different approaches for EV isolation from cancer spheroids. A batch method was created for delivering high EV yield at the end of the culture period, and a harvesting method was created to enable time-dependent collection of EVs to combine EV profiling with spheroid development. Both these methods were easy to set up, quick to perform, and they provided a high EV yield. When compared to scaffold-free 3D spheroid cultures on ultra-low affinity plates, the NFC method resulted in similar EV production/cell, but the NFC method was scalable and easier to perform resulting in high EV yields. In summary, we introduce here an NFC-based, innovative pipeline for acquiring EVs from 3D cancer spheroids, which can be tailored to support the needs of variable EV research objectives.

Induction and Maturation of Hepatocyte-Like Cells In Vitro: Focus on Technological Advances and Challenges

Limited by the poor proliferation and restricted sources of adult hepatocytes, there is an urgent need to find substitutes for proliferation and cultivation of mature hepatocytes in vitro for use in disease treatment, drug approval, and toxicity testing. Hepatocyte-like cells (HLCs), which originate from undifferentiated stem cells or modified adult cells, are considered good candidates because of their advantages in terms of cell source and in vitro expansion ability. However, the majority of induced HLCs are in an immature state, and their degree of differentiation is heterogeneous, diminishing their usability in basic research and limiting their clinical application. Therefore, various methods have been developed to promote the maturation of HLCs, including chemical approaches, alteration of cell culture systems, and genetic manipulation, to meet the needs of in vivo transplantation and in vitro model establishment. This review proposes different cell types for the induction of HLCs, and provide a comprehensive overview of various techniques to promote the generation and maturation of HLCs in vitro.

Recent Advances in Three-Dimensional Stem Cell Culture Systems and Applications

Cell culture is one of the most core and fundamental techniques employed in the fields of biology and medicine. At present, although the two-dimensional cell culture method is commonly used in vitro, it is quite different from the cell growth microenvironment in vivo. In recent years, the limitations of two-dimensional culture and the advantages of three-dimensional culture have increasingly attracted more and more attentions. Compared to two-dimensional culture, three-dimensional culture system is better to realistically simulate the local microenvironment of cells, promote the exchange of information among cells and the extracellular matrix (ECM), and retain the original biological characteristics of stem cells. In this review, we first present three-dimensional cell culture methods from two aspects: a scaffold-free culture system and a scaffold-based culture system. The culture method and cell characterizations will be summarized. Then the application of three-dimensional cell culture system is further explored, such as in the fields of drug screening, organoids and assembloids. Finally, the directions for future research of three-dimensional cell culture are stated briefly.

3D culture of functional human iPSC-derived hepatocytes using a core-shell microfiber

Human iPSC-derived hepatocytes hold great promise as a cell source for cell therapy and drug screening. However, the culture method for highly-quantified hepatocytes has not yet been established. Herein, we have developed an encapsulation and 3D cultivation method for iPSC-hepatocytes in core-shell hydrogel microfibers (a.k.a. cell fiber). In the fiber-shaped 3D microenvironment consisting of abundant extracellular matrix (ECM), the iPSC-hepatocytes exhibited many hepatic characteristics, including the albumin secretion, and the expression of the hepatic marker genes (ALB, HNF4α, ASGPR1, CYP2C19, and CYP3A4). Furthermore, we found that the fibers were mechanically stable and can be applicable to hepatocyte transplantation. Three days after transplantation of the microfibers into the abdominal cavity of immunodeficient mice, human albumin was detected in the peripheral blood of the transplanted mice. These results indicate that the iPSC-hepatocyte fibers are promising either as in vitro models for drug screening or as implantation grafts to treat liver failure.

Current progress in hepatic tissue regeneration by tissue engineering

Liver, as a vital organ, is responsible for a wide range of biological functions to maintain homeostasis and any type of damages to hepatic tissue contributes to disease progression and death. Viral infection, trauma, carcinoma, alcohol misuse and inborn errors of metabolism are common causes of liver diseases are a severe known reason for leading to end-stage liver disease or liver failure. In either way, liver transplantation is the only treatment option which is, however, hampered by the increasing scarcity of organ donor. Over the past years, considerable efforts have been directed toward liver regeneration aiming at developing new approaches and methodologies to enhance the transplantation process. These approaches include producing decellularized scaffolds from the liver organ, 3D bio-printing system, and nano-based 3D scaffolds to simulate the native liver microenvironment. The application of small molecules and micro-RNAs and genetic manipulation in favor of hepatic differentiation of distinct stem cells could also be exploited. All of these strategies will help to facilitate the application of stem cells in human medicine. This article reviews the most recent strategies to generate a high amount of mature hepatocyte-like cells and updates current knowledge on liver regenerative medicine.

iPSC-Derived Hepatocytes as a Platform for Disease Modeling and Drug Discovery

The liver is one of the largest organs in the body and is responsible for a diverse repertoire of metabolic processes. Such processes include the secretion of serum proteins, carbohydrate and lipid metabolism, bile acid and urea synthesis, detoxification of drugs and metabolic waste products, and vitamin and carbohydrate storage. Currently, liver disease is one of the most prevalent causes of mortality in the USA with congenital liver defects contributing to a significant proportion of these deaths. Historically the study of liver disease has been hampered by a shortage of organ donors, the subsequent scarcity of healthy tissue, and the failure of animal models to fully recapitulate human liver function. In vitro culture of hepatocytes has also proven difficult because primary hepatocytes rapidly de-differentiate in culture. Recent advances in stem cell technology have facilitated the generation of induced pluripotent stem cells (iPSCs) from various somatic cell types from patients. Such cells can be differentiated to a liver cell fate, essentially providing a limitless supply of cells with hepatocyte characteristics that can mimic the pathophysiology of liver disease. Furthermore, development of the CRISPR-Cas9 system, as well as advancement of miniaturized differentiation platforms has facilitated the development of high throughput models for the investigation of hepatocyte differentiation and drug discovery. In this review, we will explore the latest advances in iPSC-based disease modeling and drug screening platforms and examine how this technology is being used to identify new pharmacological interventions, and to advance our understanding of liver development and mechanisms of disease. We will cover how iPSC technology is being used to develop predictive models for rare diseases and how information gained from large in vitro screening experiments can be used to directly inform clinical investigation.

Differentiation of the human liver progenitor cell line (HepaRG) on a microfluidic-based biochip

HepaRG is a bipotent stem cell line that can be differentiated towards hepatocyte-like and biliary-like cells. The entire cultivation process requires 1 month and relies on the addition of 2% dimethyl sulfoxide (DMSO) to the culture. Our motivation in this research is to differentiate HepaRG cells (progenitor cells and undifferentiated cells) towards hepatocyte-like cells by minimizing the cultivation time and without using DMSO treatment by instead using a microfluidic device combined with the following strategies: (a) comparison of extracellular matrices (matrigel and collagen I), (b) types of flow (one or both sides), and (c) effects of DMSO. Our results demonstrate that matrigel promotes the differentiation of progenitor cells towards hepatocytes and biliary-like cells. Moreover, the frequent formation of HepaRG cell clusters was observed by a supply of both sides of flow, and the cell viability and liver specific functions were influenced by DMSO. Finally, differentiated HepaRG progenitor cells cultured in a microfluidic device for 14 days without DMSO treatment yielded 70% of hepatocyte-like cells with a highly polarized organization that reacted to stimulation with IL-6 to produce C-reactive protein (CRP). This culture model has high potential for investigating cell differentiation and liver pathophysiology research.

Impact of Three-Dimentional Culture Systems on Hepatic Differentiation of Puripotent Stem Cells and Beyond

Generation of functional hepatocytes from human pluripotent stem cells (hPSCs) is a vital tool to produce large amounts of human hepatocytes, which hold a great promise for biomedical and regenerative medicine applications. Despite a tremendous progress in developing the differentiation protocols recapitulating the developmental signalling and stages, these resulting hepatocytes from hPSCs yet achieve maturation and functionality comparable to those primary hepatocytes. The absence of 3D milieu in the culture and differentiation of these hepatocytes may account for this, at least partly, thus developing an optimal 3D culture could be a step forward to achieve this aim. Hence, review focuses on current development of 3D culture systems for hepatic differentiation and maturation and the future perspectives of its application.

Fabrication of agarose concave petridish for 3D-culture microarray method for spheroids formation of hepatic cells

Liver is one of the most important organ in the body. But there are many limitations about liver transplantation for liver failure. It is quite important to develop the xenogeneic biological liver for providing an alternation to transplantation or liver regeneration. In this paper, we proposed a method to construct a novel kind of agarose 3D-culture concave microwell array for spheroids formation of hepatic cells. Using the 3D printing method, the microwell array was fabricated with an overall size of 6.4 mm × 6.4 mm, containing 121 microwells with 400 μm width/400 μm thickness. By exploiting the Polydimethylsiloxane (PDMS) membranes as a bridge, we finally fabricated the agarose one. We co-cultured three types of liver cells with bionics design in the microwell arrays. Using the methods described above, the resulting co-formed hepatocyte spheroids maintained the high viability and stable liver-specific functions. This engineered agarose concave microwell array could be a potentially useful tool for forming the elements for biological liver support. After developing the complete system, we also would consider to scale up the application of this system. It will be not only applied to the therapy of human organ damage, but also to the development of disease models and drug screening models.

Decellularized human liver extracellular matrix (hDLM)-mediated hepatic differentiation of human induced pluripotent stem cells (hIPSCs)

Liver tissue engineering has emerged as a promising approach in organ transplantation but has been hampered by the lack of a reliable and readily available cell source. Human induced pluripotent stem cells hiPSCs have been highlighted as a desirable source, due to their differentiation potential, ability to self-renew, and the possibility of making patient-specific cells. We developed a decellularization protocol that efficiently removes cellular material while retaining extracellular matrix components. Subsequently, hiPSCs were differentiated on decellularized human liver extracellular matrix (hDLM) scaffolds using an established hepatic differentiation protocol. We demonstrate that using hDLM leads to upregulation markers of hepatic functions when compared with standard differentiation conditions. In addition, expression of a number of hepatic transcription and nuclear factors were found to be within levels comparable with those of primary human adult hepatocytes. Analysis of progression of differentiation on hDLM demonstrated that hepatic developmental marker expression was consistent with hepatic development. The hDLM-derived cells exhibited key hepatic characteristics that were comparable with those observed in primary neonatal human hepatocytes. We investigated the optimal timing of the introduction of hDLM into the differentiation protocol and found that the best results are obtained when cells are plated on hDLM since the earliest stages and accompanied by a progressive loss of sensitivity to substrate composition at later stages. The significance of this work is that it allows for the development of differentiation protocols that take into account signals from extracellular matrix, closely recapitulating of the in vivo micro-environment and resulting in cells that are phenotypically closer to mature hepatocytes.