Rat multicellular 3D liver microtissues to explore TGF-β1 induced effects

Liver-on-chips for drug discovery and development

Recent FDA modernization act 2.0 has led to increasing industrial R&D investment in advanced in vitro 3D models such as organoids, spheroids, organ-on-chips, 3D bioprinting, and in silico approaches. Liver-related advanced in vitro models remain the prime area of interest, as liver plays a central role in drug clearance of compounds. Growing evidence indicates the importance of recapitulating the overall liver microenvironment to enhance hepatocyte maturity and culture longevity using liver-on-chips (LoC) in vitro. Hence, pharmaceutical industries have started exploring LoC assays in the two of the most challenging areas: accurate in vitro-in vivo extrapolation (IVIVE) of hepatic drug clearance and drug-induced liver injury. We examine the joint efforts of commercial chip manufacturers and pharmaceutical companies to present an up-to-date overview of the adoption of LoC technology in the drug discovery. Further, several roadblocks are identified to the rapid adoption of LoC assays in the current drug development framework. Finally, we discuss some of the underexplored application areas of LoC models, where conventional 2D hepatic models are deemed unsuitable. These include clearance prediction of metabolically stable compounds, immune-mediated drug-induced liver injury (DILI) predictions, bioavailability prediction with gut-liver systems, hepatic clearance prediction of drugs given during pregnancy, and dose adjustment studies in disease conditions. We conclude the review by discussing the importance of PBPK modeling with LoC, digital twins, and AI/ML integration with LoC.

Biological and mechanical influence of three-dimensional microenvironment formed in microwell on multicellular spheroids composed of heterogeneous hair follicle stem cells

Hair loss caused by malfunction of the hair follicle stem cells (HFSCs) and physical damage to the skin is difficult to recover from naturally. To overcome these obstacles to hair follicle (HF) regeneration, it is essential to understand the three-dimensional (3D) microenvironment and interactions of various cells within the HFs. Therefore, 3D cell culture technology has been used in HF regeneration research; specifically, multicellular spheroids have been generally adapted to mimic the 3D volumetric structure of the HF. In this study, we culture HF-derived cells, which are mainly composed of HFSCs, in the form of 3D spheroids using a microwell array and discuss the effects of the 3D cellular environment on HF morphogenesis by expression measurements of Sonic hedgehog signaling and stem cell markers in the HF spheroids. Additionally, the influences of microwell depth on HF spheroid formation and biological conditions were investigated. The biomolecular diffusion and convective flow in the microwell were predicted using computational fluid dynamics, which allows analysis of the physical stimulations occurring on the spheroid at the micro-scale. Although a simple experimental method using the microwell array was adopted in this study, the results provide fundamental insights into the physiological phenomena of HFs in the 3D microenvironment, and the numerical analysis is expected to shed light on the investigation of the geometric parameters of the microwell system.

Three-Dimensional Cell Co-Culture Liver Models and Their Applications in Pharmaceutical Research

As the primary site for the biotransformation of drugs, the liver is the most focused on organ type in pharmaceutical research. However, despite being widely used in pharmaceutical research, animal models have inherent species differences, while two-dimensional (2D) liver cell monocultures or co-cultures and three-dimensional (3D) liver cell monoculture in vitro liver models do not sufficiently represent the complexity of the human liver’s structure and function, making the evaluation results from these tools less reliable. Therefore, there is a pressing need to develop more representative in vitro liver models for pharmaceutical research. Fortunately, an exciting new development in recent years has been the emergence of 3D liver cell co-culture models. These models hold great promise as in vitro pharmaceutical research tools, because they can reproduce liver structure and function more practically. This review begins by explaining the structure and main cell composition of the liver, before introducing the potential advantages of 3D cell co-culture liver models for pharmaceutical research. We also discuss the main sources of hepatocytes and the 3D cell co-culture methods used in constructing these models. In addition, we explore the applications of 3D cell co-culture liver models with different functional states and suggest prospects for their further development.

3D culture of HepaRG cells in GelMa and its application to bioprinting of a multicellular hepatic model

Bioprinting is an emergent technology that has already demonstrated the capacity to create complex and/or vascularized multicellular structures with defined and organized architectures, in a reproducible and high throughput way. Here, we present the implementation of a complex liver model by the development of a three-dimensional extrusion bioprinting process, including parameters for matrix polymerization of methacrylated gelatin, using two hepatic cell lines, Huh7 and HepaRG. The printed structures exhibited long-term viability (28 days), proliferative ability, a relevant hepatocyte phenotype and functions equivalent to or better than those of their 2D counterparts using standard DMSO treatment. This work served as a basis for the bioprinting of complex multicellular models associating the hepatic parenchymal cells, HepaRG, with stellate cells (LX-2) and endothelial cells (HUVECs), able of colonizing the surface of the structure and thus recreating a pseudo endothelial barrier. When bioprinted in 3D monocultures, LX-2 expression was modulated by TGFβ-1 toward the induction of myofibroblastic genes such as ACTA2 and COL1A1. In 3D multicellular bioprinted structures comprising HepaRG, LX-2 and endothelial cells, we evidenced fibrillar collagen deposition, which is never observed in monocultures of either HepaRG or LX-2 alone. These observations indicate that a precise control of cellular communication is required to recapitulate key steps of fibrogenesis. Bioprinted 3D co-cultures therefore open up new perspectives in studying the molecular and cellular basis of fibrosis development and provide better access to potential inducers and inhibitors of collagen expression and deposition.

A review of manufacturing capabilities of cell spheroid generation technologies and future development

Spheroid culture provides cells with a three-dimensional environment that can better mimic physiological conditions compared to monolayer culture. Technologies involved in the generation of cell spheroids are continuously being innovated to produce spheroids with enhanced properties. In this paper, we review the manufacturing capabilities of current cell spheroid generation technologies. We propose that spheroid generation technologies should enable tight and robust process controls to produce spheroids of consistent and repeatable quality. Future technology development for the generation of cell spheroids should look into improvement in process control, standardization, scalability and monitoring, in addition to advanced methods of spheroid transfer and characterization.

Regulation of peroxisome proliferator-activated receptor-gamma activity affects the hepatic stellate cell activation and the progression of NASH via TGF-β1/Smad signaling pathway

Development of liver fibrosis is associated with activation of quiescent hepatic stellate cells (HSCs) into myofibroblasts (activated HSCs), which produce excessive extracellular matrix. Peroxisome proliferator-activated receptor-gamma (PPAR-γ) exerts protective effects on hepatic inflammation and fibrosis. The current study was to explore the function of PPAR-γ on HSC activation and progression of nonalcoholic steatohepatitis (NASH). Our study found that HSCs were gradually activated during the progression of methionine-choline-deficient (MCD) diet-induced NASH, accompanied by decreased PPAR-γ expression and activated TGF-β1/Smad signaling pathway in the liver. PPAR-γ agonist was found to inhibit primary HSCs and NIH/3T3 fibroblast activation and reverted their phenotypical morphology induced by TGF-β1 in vitro. In addition to this, PPAR-γ agonist decreased expression of TGF-β1 and phosphorylation of Smad2/3 while increased expression of Smad7. In vivo, rosiglitazone, a PPAR-γ agonist, inhibited HSC activation and alleviated liver fibrosis and inflammation similarly via inhibiting the activation of TGF-β1/Smad signaling pathway. In parallel, rosiglitazone alleviated hepatic lipid accumulation and peroxidation, beneficial to reverse of NASH. From these findings, it can be concluded that the gradual activation of HSCs is crucial to the progression of NASH and modulating PPAR-γ expression can affect HSC activation via TGF-β1/Smad signaling pathway and thereby influence hepatic fibrogenesis.

Exosomal miR-223 derived from natural killer cells inhibits hepatic stellate cell activation by suppressing autophagy

Background

Activation of hepatic stellate cells (HSCs) is a prominent driver of liver fibrosis. We previously demonstrated that exosomes derived from natural killer (NK) cells (NK-Exo) attenuated TGF-β1-induced HSC activation. Herein, this study was designed to investigate the mechanism underlying the action of NK-Exo.

Methods

NK-Exo was isolated from NK-92MI cells and then administered into TGF-β1-treated LX-2 (human HSC line) cells. MiR-223 expression in NK-Exo was downregulated by transfecting NK-92MI cells with miR-223 inhibitor followed by exosome isolation. The HSC activation was evaluated by determining cell proliferation using CCK-8 assay and measuring the protein levels of α-SMA and CoL1A1 using western blot in LX-2 cells. The expression of miR-223 was detected by qRT-PCR. The interaction between miR-223 and ATG7 was analyzed by a dual-luciferase activity assay. The autophagy was evaluated by measuring the autophagy-related proteins using western blot.

Results

miR-223 was highly expressed in NK-Exo and inhibition of miR-223 expression in NK-Exo abrogated the inhibitory effect of NK-Exo on TGF-β-induced HSC activation. ATG7 was confirmed as a direct target of miR-223. Furthermore, treatment with the autophagy activator rapamycin and ATG7 overexpression in LX-2 cells abolished the HSC activation-suppressive effect of NK-Exo.

Conclusion

NK-Exo attenuated TGF-β-induced HSC activation by transferring miR-223 that inhibited autophagy via targeting ATG7.

Exosomes derived from natural killer cells inhibit hepatic stellate cell activation and liver fibrosis

Activation of hepatic stellate cells (HSCs) is a prominent driver of liver fibrosis. This study was designed to investigate the effect of exosomes derived from natural killer (NK) cells on HSC activation and liver fibrosis. The exosomes were isolated from NK-92MI cells (NK-Exo) and identified by transmission electron microscopy, nanoparticle tracking analysis, and western blot. Then NK-Exo was administered into TGF-β1-treated LX-2 cells (human HSC line) and mice with CCl₄-induced liver fibrosis. LX-2 cell proliferation was determined by CCK-8 assay. The levels of α-SMA and CoL1A1 were measured by qRT-PCR and western blot to evaluate HSC activation. Serum levels of AST and ALT were measured. Hematoxylin-eosin, Masson staining, and Sirius Red staining were performed to assess the pathological changes and collagen deposition. Cell supernatant derived from NK-92MI cells inhibited TGF-β1-induced HSC proliferation and activation in LX-2 cells, and this effect was counteracted by the exosome inhibitor GW4869. Further assays confirmed that NK-Exo treatment significantly inhibited TGF-β1-induced HSC proliferation and activation. Moreover, NK-Exo administration alleviated CCl₄-induced liver fibrosis in mice. NK-Exo inhibited TGF-β1-induced HSC activation and CCl₄-induced liver fibrosis.