Engineering liver microtissues to study the fusion of HepG2 with mesenchymal stem cells and invasive potential of fused cells

Fusion of tumor cells and mesenchymal stem/stroma cells: a source of tumor heterogeneity, evolution and recurrence

The heterogeneity and evolution of tumors remain significant obstacles in cancer treatment, contributing to both therapy resistance and relapse. Mesenchymal stem/stromal cells (MSCs) are multipotent stromal cells within the tumor microenvironment that interact with tumor cells through various mechanisms, including cell fusion. While previous research has largely focused on the effects of MSC-tumor cell fusion on tumor proliferation, migration, and tumorigenicity, emerging evidence indicates that its role in tumor maintenance, evolution, and recurrence, particularly under stress conditions, may be even more pivotal. This review examines the connection between MSC-tumor cell fusion and several critical factors like tumor heterogeneity, cancer stem cells, and therapy resistance, highlighting the crucial role of cell fusion in tumor survival, evolution, and recurrence. Additionally, we explore potential therapeutic strategies aimed at targeting this process.

Hydrogel-Based Strategies for Liver Tissue Engineering

The liver's role in metabolism, detoxification, and immune regulation underscores the urgency of addressing liver diseases, which claim millions of lives annually. Due to donor shortages in liver transplantation, liver tissue engineering (LTE) offers a promising alternative. Hydrogels, with their biocompatibility and ability to mimic the liver's extracellular matrix (ECM), support cell survival and function in LTE. This review analyzes recent advances in hydrogel-based strategies for LTE, including decellularized liver tissue hydrogels, natural polymer-based hydrogels, and synthetic polymer-based hydrogels. These materials are ideal for in vitro cell culture and obtaining functional hepatocytes. Hydrogels' tunable properties facilitate creating artificial liver models, such as organoids, 3D bioprinting, and liver-on-a-chip technologies. These developments demonstrate hydrogels' versatility in advancing LTE's applications, including hepatotoxicity testing, liver tissue regeneration, and treating acute liver failure. This review highlights the transformative potential of hydrogels in LTE and their implications for future research and clinical practice.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Construction of in vitro liver-on-a-chip models and application progress

The liver is the largest internal organ of the human body. It has a complex structure and function and plays a vital role in drug metabolism. In recent decades, extensive research has aimed to develop in vitro models that can simulate liver function to demonstrate changes in the physiological and pathological environment of the liver. Animal models and in vitro cell models are common, but the data obtained from animal models lack relevance when applied to humans, while cell models have limited predictive ability for metabolism and toxicity in humans. Recent advancements in tissue engineering, biomaterials, chip technology, and 3D bioprinting have provided opportunities for further research in in vitro models. Among them, liver-on-a-Chip (LOC) technology has made significant achievements in reproducing the in vivo behavior, physiological microenvironment, and metabolism of cells and organs. In this review, we discuss the development of LOC and its research progress in liver diseases, hepatotoxicity tests, and drug screening, as well as chip combinations. First, we review the structure and the physiological function of the liver. Then, we introduce the LOC technology, including general concepts, preparation materials, and methods. Finally, we review the application of LOC in disease modeling, hepatotoxicity tests, drug screening, and chip combinations, as well as the future challenges and directions of LOC.

Engineering Highly Vascularized Bone Tissues by 3D Bioprinting of Granular Prevascularized Spheroids

The convergence of 3D bioprinting with powerful manufacturing capability and cellular self-organization that can reproduce intricate tissue microarchitecture and function is a promising direction toward building functional tissues and has yet to be demonstrated. Here, we develop a granular aggregate-prevascularized (GAP) bioink for engineering highly vascularized bone tissues by capitalizing on the condensate-mimicking, self-organization, and angiogenic properties of prevascularized mesenchymal spheroids. The GAP bioink utilizes prevascularized aggregates as building blocks, which are embedded densely in extracellular matrices conducive to spontaneous self-organization. We printed various complex structures with high cell density (∼1.5 × 108 cells/cm3), viability (∼80%), and shape fidelity using GAP bioink. After printing, the prevascularized mesenchymal spheroids developed an interconnected vascular network through angiogenic sprouting. We printed highly vascularized bone tissues using GAP bioink and found that prevascularized spheroids were more conducive to osteogenesis and angiogenesis. We envision that the design of the GAP bioink could be further integrated with human-induced pluripotent stem cell-derived organoids, which opens new avenues to create patient-specific vascularized tissues for therapeutic applications..

Deciphering the possible reciprocal loop between hepatic stellate cells and cancer cells in the tumor microenvironment of the liver

Activated hepatic stellate cells (HSCs)/myofibroblasts are the important sources of cancer-associated fibroblasts in the liver tumor microenvironment (TME). The crosstalk between activated HSCs and tumor cells mediates HCC progression, metastasis, tumor cell survival, angiogenesis and chemoresistance. In TME, HCC cells secrete various soluble factors responsible for the phenotypic activation of quiescent HSCs. Tumor cells use activated HSC-derived extracellular matrix (ECM) for migration and invasion. Further, in liver TME, activated HSCs and sinusoidal endothelial cells engage in a crosstalk that causes the secretion of angiogenesis and metastasis-related growth factors and cytokines. Activated HSCs and immune cells crosstalk to decrease immune surveillance in the liver TME by increasing the population of T regulatory cells and M2 macrophages or myeloid-derived suppressor cells. Thus, HSCs play a vital role in liver TME cell interactions. Therefore, a deep understanding of HSCs activation and their crosstalk with cancer and immune cells in TME may lead to the development of novel therapeutic strategies to target HCC.