Bioengineering Approaches for the Advanced Organoid Research

Progress of organoid platform in cardiovascular research

Cardiovascular disease is a significant cause of death in humans. Various models are necessary for the study of cardiovascular diseases, but once cellular and animal models have some defects, such as insufficient fidelity. As a new technology, organoid has certain advantages and has been used in many applications in the study of cardiovascular diseases. This article aims to summarize the application of organoid platforms in cardiovascular diseases, including organoid construction schemes, modeling, and application of cardiovascular organoids. Advances in cardiovascular organoid research have provided many models for different cardiovascular diseases in a variety of areas, including myocardium, blood vessels, and valves. Physiological and pathological models of different diseases, drug research models, and methods for evaluating and promoting the maturation of different kinds of organ tissues are provided for various cardiovascular diseases, including cardiomyopathy, myocardial infarction, and atherosclerosis. This article provides a comprehensive overview of the latest research progress in cardiovascular organ tissues, including construction protocols for cardiovascular organoid tissues and their evaluation system, different types of disease models, and applications of cardiovascular organoid models in various studies. The problems and possible solutions in organoid development are summarized.

Senescence-targeted MicroRNA/Organoid composite hydrogel repair cartilage defect and prevention joint degeneration via improved chondrocyte homeostasis

Introduction

Cartilage defect (CD) is a common complication in osteoarthritis (OA). Impairment of chondrogenesis and cellular senescence are considered as hallmarks of OA development and caused failure of cartilage repair in most clinical CD cases. Exploring markers for cellular senescence in CD patients might provide new perspectives for osteoarthritic CD patients. In the present study, we aim to explore senescent markers in CD patients with OA to fabricate a senescence-targeted SMSC organoid hydrogel for cartilage repair.

Methods

Clinical cartilage samples from cartilage defect patients were collected. Immunofluorescence staining of senescent markers and SA-β-Gal staining were used to detect the senescence state of SMSCs and chondrocytes in cartilage defect and OA patients. MicroRNA expression profiles of SMSC organoids and H2O2-treated SMSC organoids were analyzed and compared with high-throughput microRNA sequencing. Fluorescent in situ hybridization of miRNA were used to determine the expression level of miR-24 in SMSC organoids and cartilage samples. Interaction between miR-24 and its downstream target was analyzed via qRT-PCR, immunofluorescence and luciferase assay. Senescence-targeted miR-24 μS/SMSC organoid hydrogel (MSOH) was constructed for cartilage repair. Anti-senescence properties and chondrogenesis were determined in vitro for MSOH. Rats were used to evaluate the cartilage repair capacity of the MSOH hydrogel in vivo.

Results

In this study, we found Osteoarthritic cartilage defect patients demonstrated upregulated cellular senescence in joint cartilage. MicroRNA sequencing demonstrated senescence marker miR-24 was negatively associated with cartilage impairment and cellular senescence in osteoarthritic CD patients. Moreover, miR-24 mimics alleviates cellular senescence to promote chondrogenesis by targeting downstream TAOK1. Also, miR-24 downregulated TAOK1 expression and promoted chondrogenesis in SMSC organoids. Senescence-targeted miR-24 μS/SMSC organoid hydrogel (MSOH) was constructed and demonstrated superior chondrogenesis in vitro. Animal experiments demonstrated that MSOH hydrogel showed better cartilage repairing effects and better maintained joint function at 24 weeks with low intra-articular inflammatory response after transplantation in rat joint. Single-cell RNA-seq of generated cartilage indicated that implanted MSOH could affect chondrocyte homeostatic state and alter the chondrocyte cluster frequency by regulating cellular glycolysis and OXPHOS, impacting cell cycle and ferroptosis to alleviate cellular senescence and prevent joint degeneration.

Conclusion

Osteoarthritic cartilage defect patients demonstrated upregulated cellular senescence in joint cartilage. Senescence marker miR-24 was negatively associated with cartilage impairment in osteoarthritic CD patients. miR-24 attenuates chondrocytes senescence and promotes chondrogenesis in SMSC organoids through targeting TAOK1. Senescence-targeted miR-24 microsphere/SMSC organoid composite hydrogel could successfully repair cartilage defect in osteoarthritic microenvironment via enhanced miR-24/TAOK1 signaling pathway, suggesting MSOH might be a novel therapy for cartilage repair in osteoarthritic CD patients.

Bioengineered Silk Protein-Based 3D In Vitro Models for Tissue Engineering and Drug Development: From Silk Matrix Properties to Biomedical Applications

3D in vitro model has emerged as a valuable tool for studying tissue development, drug screening, and disease modeling. 3D systems can accurately replicate tissue microstructures and physiological features, mirroring the in vivo microenvironment departing from conventional 2D cell cultures. Various 3D in vitro models utilizing biomacromolecules like collagen and synthetic polymers have been developed to meet diverse research needs and address the complex challenges of contemporary research. Silk proteins, bearing structural and functional similarities to collagen, have been increasingly employed to construct advanced 3D in vitro systems, surpassing the limitations of 2D cultures. This review examines silk proteins' composition, structure, properties, and functions, elucidating their role in 3D in vitro models. Furthermore, recent advances in biomedical applications involving silk-based organoid models are discussed. In particular, the unique physiological attributes of silk matrix constituents in in vitro tissue constructs are highlighted, providing a meticulous evaluation of their importance. Additionally, it outlines the current research hurdles and complexities while contemplating future avenues, thereby paving the way for developing complex and biomimetic silk protein-based microtissues.

Recent Advances of Engineered Cell Membrane-Based Nanotherapeutics to Combat Inflammatory Diseases

An immune reaction known as inflammation serves as a shield from external danger signals, but an overactive immune system may additionally lead to tissue damage and even a variety of inflammatory disorders. By inheriting biological functionalities and serving as both a therapeutic medication and a drug carrier, cell membrane-based nanotherapeutics offer the potential to treat inflammatory disorders. To further strengthen the anti-inflammatory benefits of natural cell membranes, researchers alter and optimize the membranes using engineering methods. This review focuses on engineered cell membrane-based nanotherapeutics (ECMNs) and their application in treating inflammation-related diseases. Specifically, this article discusses the methods of engineering cell membranes for inflammatory diseases and examines the progress of ECMNs in inflammation-targeted therapy, inflammation-neutralizing therapy, and inflammation-immunomodulatory therapy. Additionally, the article looks into the perspectives and challenges of ECMNs in inflammatory treatment and offers suggestions as well as guidance to encourage further investigations and implementations in this area.

Gelatin methacryloyl microneedle loaded with 3D-MSC-Exosomes for the protection of ischemia-reperfusion

Exosomes (Exo) generated from mesenchymal stem cells (MSCs) have great therapeutic potential in ischemia-reperfusion treatment. For best therapeutic effect, high quality Exo product and effective delivery system are indispensable. In this study, we developed a new strategy for ischemia-reperfusion recovery by combining MSCs 3D (3D-MSC) culturing technology to generate Exo (3D-MSC-Exo) and microneedle for topical delivery. Firstly, primary MSCs from neonatal mice were isolated and 3D cultured with gelatin methacryloyl (GelMA) hydrogel to prepare 3D-MSC-Exo. The 3D-MSC showed better viability and 3D-MSC-Exo exhibited more effective effects of reducing neuroinflammation, inhibiting glial scarring, and promoting angiogenesis. Subsequently, the biocompatible GelMA was used to construct microneedles for 3D-Exo delivery (GelMA-MN@3D-Exo). The results demonstrated GelMA microneedles had excellent 3D-Exo loading capacity and enabled continuous 3D-Exo release to maintain effective therapeutic concentrations. Furthermore, the rat middle cerebral artery occlusion (MCAO) model was established to evaluate the therapeutic effect of GelMA-MN@3D-Exo in ischemia-reperfusion in vivo. Animal experiments showed that the GelMA-MN@3D-Exo system could effectively reduce the local neuroinflammatory reaction, promote angiogenesis and minimize glial scar proliferation in ischemia-reperfusion. The underlying reasons for the stronger neuroprotective effect of 3D-Exo was further studied using mass spectrometry and transcriptome assays, verifying their effects on immune regulation and cell proliferation. Taken together, our findings demonstrated that GelMA-MN@3D-Exo microneedle can effectively attenuate ischemia-reperfusion cell damage in the MCAO model, which provides a promising therapeutic strategy for ischemia-reperfusion recovery.

The application of organoids in colorectal diseases

Intestinal organoids are a three-dimensional cell culture model derived from colon or pluripotent stem cells. Intestinal organoids constructed in vitro strongly mimic the colon epithelium in cell composition, tissue architecture, and specific functions, replicating the colon epithelium in an in vitro culture environment. As an emerging biomedical technology, organoid technology has unique advantages over traditional two-dimensional culture in preserving parental gene expression and mutation, cell function, and biological characteristics. It has shown great potential in the research and treatment of colorectal diseases. Organoid technology has been widely applied in research on colorectal topics, including intestinal tumors, inflammatory bowel disease, infectious diarrhea, and intestinal injury regeneration. This review focuses on the application of organoid technology in colorectal diseases, including the basic principles and preparation methods of organoids, and explores the pathogenesis of and personalized treatment plans for various colorectal diseases to provide a valuable reference for organoid technology development and application.

Osteochondral organoids: current advances, applications, and upcoming challenges

In the realm of studying joint-related diseases, there is a continuous quest for more accurate and representative models. Recently, regenerative medicine and tissue engineering have seen a growing interest in utilizing organoids as powerful tools for studying complex biological systems in vitro. Organoids, three-dimensional structures replicating the architecture and function of organs, provide a unique platform for investigating disease mechanisms, drug responses, and tissue regeneration. The surge in organoid research is fueled by the need for physiologically relevant models to bridge the gap between traditional cell cultures and in vivo studies. Osteochondral organoids have emerged as a promising avenue in this pursuit, offering a better platform to mimic the intricate biological interactions within bone and cartilage. This review explores the significance of osteochondral organoids and the need for their development in advancing our understanding and treatment of bone and cartilage-related diseases. It summarizes osteochondral organoids' insights and research progress, focusing on their composition, materials, cell sources, and cultivation methods, as well as the concept of organoids on chips and application scenarios. Additionally, we address the limitations and challenges these organoids face, emphasizing the necessity for further research to overcome these obstacles and facilitate orthopedic regeneration.

FAM19A5 in vascular aging and osteoporosis: Mechanisms and the "calcification paradox"

Aging induces a progressive decline in the vasculature's structure and function. Vascular aging is a determinant factor for vascular ailments in the elderly. FAM19A5, a recently identified adipokine, has demonstrated involvement in multiple vascular aging-related pathologies, including atherosclerosis, cardio-cerebral vascular diseases and cognitive deficits. This review summarizes the current understanding of FAM19A5' role and explores its putative regulatory mechanisms in various aging-related disorders, including cardiovascular diseases (CVDs), metabolic diseases, neurodegenerative diseases and malignancies. Importantly, we provide novel insights into the underlying therapeutic value of FAM19A5 in osteoporosis. Finally, we outline future perspectives on the diagnostic and therapeutic potential of FAM19A5 in vascular aging-related diseases.

Organoid bioinks: construction and application

Organoids have emerged as crucial platforms in tissue engineering and regenerative medicine but confront challenges in faithfully mimicking native tissue structures and functions. Bioprinting technologies offer a significant advancement, especially when combined with organoid bioinks-engineered formulations designed to encapsulate both the architectural and functional elements of specific tissues. This review provides a rigorous, focused examination of the evolution and impact of organoid bioprinting. It emphasizes the role of organoid bioinks that integrate key cellular components and microenvironmental cues to more accurately replicate native tissue complexity. Furthermore, this review anticipates a transformative landscape invigorated by the integration of artificial intelligence with bioprinting techniques. Such fusion promises to refine organoid bioink formulations and optimize bioprinting parameters, thus catalyzing unprecedented advancements in regenerative medicine. In summary, this review accentuates the pivotal role and transformative potential of organoid bioinks and bioprinting in advancing regenerative therapies, deepening our understanding of organ development, and clarifying disease mechanisms.

Decellularized Brain Extracellular Matrix Hydrogel Aids the Formation of Human Spinal-Cord Organoids Recapitulating the Complex Three-Dimensional Organization

The intricate electrophysiological functions and anatomical structures of spinal cord tissue render the establishment of in vitro models for spinal cord-related diseases highly challenging. Currently, both in vivo and in vitro models for spinal cord-related diseases are still underdeveloped, complicating the exploration and development of effective therapeutic drugs or strategies. Organoids cultured from human induced pluripotent stem cells (hiPSCs) hold promise as suitable in vitro models for spinal cord-related diseases. However, the cultivation of spinal cord organoids predominantly relies on Matrigel, a matrix derived from murine sarcoma tissue. Tissue-specific extracellular matrices are key drivers of complex organ development, thus underscoring the urgent need to research safer and more physiologically relevant organoid culture materials. Herein, we have prepared a rat decellularized brain extracellular matrix hydrogel (DBECMH), which supports the formation of hiPSC-derived spinal cord organoids. Compared with Matrigel, organoids cultured in DBECMH exhibited higher expression levels of markers from multiple compartments of the natural spinal cord, facilitating the development and maturation of spinal cord organoid tissues. Our study suggests that DBECMH holds potential to replace Matrigel as the standard culture medium for human spinal cord organoids, thereby advancing the development of spinal cord organoid culture protocols and their application in in vitro modeling of spinal cord-related diseases.

Human Placenta Decellularized Extracellular Matrix Hydrogel Promotes the Generation of Human Spinal Cord Organoids with Dorsoventral Organization from Human Induced Pluripotent Stem Cells

Spinal cord organoids are of significant value in the research of spinal cord-related diseases by simulating disease states, thereby facilitating the development of novel therapies. However, the complexity of spinal cord structure and physiological functions, along with the lack of human-derived inducing components, presents challenges in the in vitro construction of human spinal cord organoids. Here, we introduce a novel human decellularized placenta-derived extracellular matrix hydrogel (DPECMH) and, combined with a new induction protocol, successfully construct human spinal cord organoids. The human placenta-sourced decellularized extracellular matrix (dECM), verified through hematoxylin and eosin staining, DNA quantification, and immunofluorescence staining, retained essential ECM components such as elastin, fibronectin, type I collagen, laminin, and so forth. The temperature-sensitive hydrogel made from human placenta dECM demonstrated good biocompatibility and promoted the differentiation of human induced pluripotent stem cell (hiPSCs)-derived spinal cord organoids into neurons. It displayed enhanced expression of laminar markers in comparison to Matrigel and showed higher expression of laminar markers compared to Matrigel, accelerating the maturation process of spinal cord organoids and demonstrating its potential as an organoid culture substrate. DPECMH has the potential to replace Matrigel as the standard additive for human spinal cord organoids, thus advancing the development of spinal cord organoid culture protocols and their application in the in vitro modeling of spinal cord-related diseases.

Application of organoid technology in the human health risk assessment of microplastics: A review of progresses and challenges

Microplastic (MP) pollution has become a global environmental issue, and increasing concern has been raised about its impact on human health. Current studies on the toxic effects and mechanisms of MPs have mostly been conducted in animal models or in vitro cell cultures, which have limitations regarding inter-species differences or stimulation of cellular functions. Organoid technology derived from human pluripotent or adult stem cells has broader prospects for predicting the potential health risks of MPs to humans. Herein, we reviewed the current application advancements and opportunities for different organoids, including brain, retinal, intestinal, liver, and lung organoids, to assess the human health risks of MPs. Organoid techniques accurately simulate the complex processes of MPs and reflect phenotypes related to diseases caused by MPs such as liver fibrosis, neurodegeneration, impaired intestinal barrier and cardiac hypertrophy. Future perspectives were also proposed for technological innovation in human risk assessment of MPs using organoids, including extending the lifespan of organoids to assess the chronic toxicity of MPs, and reconstructing multi-organ interactions to explore their potential in studying the microbiome-gut-brainaxis effect of MPs.

Construction of dental pulp decellularized matrix by cyclic lavation combined with mechanical stirring and its proteomic analysis

The decellularized matrix has a great potential for tissue remodeling and regeneration; however, decellularization could induce host immune rejection due to incomplete cell removal or detergent residues, thereby posing significant challenges for its clinical application. Therefore, the selection of an appropriate detergent concentration, further optimization of tissue decellularization technique, increased of biosafety in decellularized tissues, and reduction of tissue damage during the decellularization procedures are pivotal issues that need to be investigated. In this study, we tested several conditions and determined that 0.1% Sodium dodecyl sulfate and three decellularization cycles were the optimal conditions for decellularization of pulp tissue. Decellularization efficiency was calculated and the preparation protocol for dental pulp decellularization matrix (DPDM) was further optimized. To characterize the optimized DPDM, the microstructure, odontogenesis-related protein and fiber content were evaluated. Our results showed that the properties of optimized DPDM were superior to those of the non-optimized matrix. We also performed the 4D-Label-free quantitative proteomic analysis of DPDM and demonstrated the preservation of proteins from the natural pulp. This study provides a optimized protocol for the potential application of DPDM in pulp regeneration.

The chicken chorioallantoic membrane assay revisited - A face-lifted approach for new perspectives in placenta research

The study of very early human placentation is largely limited due to ethical restrictions on the use of embryonic tissue and the fact that the placental anatomy of common laboratory animal models varies considerably from that of humans. In recent years several promising models, including trophoblast stem cell-derived organoids, have been developed that have also proven useful for the study of important trophoblast differentiation processes. However, the consideration of maternal blood flow in trophoblast invasion models currently appears to be limited to animal models. An almost forgotten model to study the invasive behavior of trophoblasts is to culture them in vitro on the chicken chorioallantoic membrane (CAM), showing an extraembryonic vascular network in its mesenchymal stroma that is continuously perfused by the chicken embryonic blood circulation. Here, we present an extension of the previously described ex ovo CAM assay and describe the use of cavity-bearing trophoblast spheroids obtained from the first trimester cell line ACH-3P. We demonstrate how spheroids penetrated the CAM and that erosion of CAM vessels by trophoblasts led to filling of the spheroid cavities with chicken blood, mimicking initial steps of intervillous space blood perfusion. Moreover, we prove that this model is useful for state-of-the-art techniques including immunofluorescence and in situ padlock probe hybridization, making it a versatile tool to study aspects of trophoblast invasion in presence of blood flow.

Advancing Organoid Engineering for Tissue Regeneration and Biofunctional Reconstruction

Tissue damage and functional abnormalities in organs have become a considerable clinical challenge. Organoids are often applied as disease models and in drug discovery and screening. Indeed, several studies have shown that organoids are an important strategy for achieving tissue repair and biofunction reconstruction. In contrast to established stem cell therapies, organoids have high clinical relevance. However, conventional approaches have limited the application of organoids in clinical regenerative medicine. Engineered organoids might have the capacity to overcome these challenges. Bioengineering-a multidisciplinary field that applies engineering principles to biomedicine-has bridged the gap between engineering and medicine to promote human health. More specifically, bioengineering principles have been applied to organoids to accelerate their clinical translation. In this review, beginning with the basic concepts of organoids, we describe strategies for cultivating engineered organoids and discuss the multiple engineering modes to create conditions for breakthroughs in organoid research. Subsequently, studies on the application of engineered organoids in biofunction reconstruction and tissue repair are presented. Finally, we highlight the limitations and challenges hindering the utilization of engineered organoids in clinical applications. Future research will focus on cultivating engineered organoids using advanced bioengineering tools for personalized tissue repair and biofunction reconstruction.

Traditional and emerging strategies using hepatocytes for pancreatic regenerative medicine

Although pancreas and islet cell transplantation are the only ways to prevent the late complications of insulin-dependent diabetes, a shortage of donors is a major obstacle to tissue and organ transplantation. Stem cell therapy is an effective treatment for diabetes and other pancreatic-related diseases, which can be achieved by inducing their differentiation into insulin-secreting cells. The liver is considered an ideal source of pancreatic cells due to its similar developmental origin and strong regenerative ability as the pancreas. This article reviews the traditional and emerging strategies using hepatocytes for pancreatic regenerative medicine and evaluates their advantages and challenges. Gene reprogramming and chemical reprogramming technologies are traditional strategies with potential to improve the efficiency and specificity of cell reprogramming and promote the transformation of hepatocytes into islet cells. At the same time, organoid technology, as an emerging strategy, has received extensive attention. Biomaterials provide a three-dimensional culture microenvironment for cells, which helps improve cell survival and differentiation efficiency. In addition, clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing technology has brought new opportunities and challenges to the development of organoid technology.

Hybrid Endometrial-Derived Hydrogels: Human Organoid Culture Models and In Vivo Perspectives

The endometrium plays a vital role in fertility, providing a receptive environment for embryo implantation and development. Understanding the endometrial physiology is essential for developing new strategies to improve reproductive healthcare. Human endometrial organoids (hEOs) are emerging as powerful models for translational research and personalized medicine. However, most hEOs are cultured in a 3D microenvironment that significantly differs from the human endometrium, limiting their applicability in bioengineering. This study presents a hybrid endometrial-derived hydrogel that combines the rigidity of PuraMatrix (PM) with the natural scaffold components and interactions of a porcine decellularized endometrial extracellular matrix (EndoECM) hydrogel. This hydrogel provides outstanding support for hEO culture, enhances hEO differentiation efficiency due to its biochemical similarity with the native tissue, exhibits superior in vivo stability, and demonstrates xenogeneic biocompatibility in mice over a 2-week period. Taken together, these attributes position this hybrid endometrial-derived hydrogel as a promising biomaterial for regenerative treatments in reproductive medicine.

Transplantation of beige adipose organoids fabricated using adipose acellular matrix hydrogel improves metabolic dysfunction in high-fat diet-induced obesity and type 2 diabetes mice

Transplantation of brown adipose tissue (BAT) is a promising approach for treating obesity and metabolic disorders. However, obtaining sufficient amounts of functional BAT or brown adipocytes for transplantation remains a major challenge. In this study, we developed a hydrogel that combining adipose acellular matrix (AAM) and GelMA and HAMA that can be adjusted for stiffness by modulating the duration of light-crosslinking. We used human white adipose tissue-derived microvascular fragments to create beige adipose organoids (BAO) that were encapsulated in either a soft or stiff AAM hydrogel. We found that BAOs cultivated in AAM hydrogels with high stiffness demonstrated increased metabolic activity and upregulation of thermogenesis-related genes. When transplanted into obese and type 2 diabetes mice, the HFD + BAO group showed sustained improvements in metabolic rate, resulting in significant weight loss and decreased blood glucose levels. Furthermore, the mice showed a marked reduction in nonalcoholic liver steatosis, indicating improved liver function. In contrast, transplantation of 2D-cultured beige adipocytes failed to produce these beneficial effects. Our findings demonstrate the feasibility of fabricating beige adipose organoids in vitro and administering them by injection, which may represent a promising therapeutic approach for obesity and diabetes.

Nascent matrix deposition supports alveolar organoid formation from aggregates in synthetic hydrogels

Human induced pluripotent stem cell (iPSC) derived alveolar organoids have emerged as a system to model the alveolar epithelium in homeostasis and disease. However, alveolar organoids are typically grown in Matrigel, a mouse-sarcoma derived basement membrane matrix that offers poor control over matrix properties, prompting the development of synthetic hydrogels as a Matrigel alternative. Here, we develop a two-step culture method that involves pre-aggregation of organoids in hydrogel-based microwells followed by embedding in a synthetic hydrogel that supports alveolar organoid growth, while also offering considerable control over organoid and hydrogel properties. We find that the aggregated organoids secrete their own nascent extracellular matrix (ECM) both in the microwells and upon embedding in the synthetic hydrogels. Thus, the synthetic gels described here allow us to de-couple exogenous and nascent ECM in order to interrogate the role of ECM in organoid formation.

A Hierarchical Mechanotransduction System: From Macro to Micro

Mechanotransduction is a strictly regulated process whereby mechanical stimuli, including mechanical forces and properties, are sensed and translated into biochemical signals. Increasing data demonstrate that mechanotransduction is crucial for regulating macroscopic and microscopic dynamics and functionalities. However, the actions and mechanisms of mechanotransduction across multiple hierarchies, from molecules, subcellular structures, cells, tissues/organs, to the whole-body level, have not been yet comprehensively documented. Herein, the biological roles and operational mechanisms of mechanotransduction from macro to micro are revisited, with a focus on the orchestrations across diverse hierarchies. The implications, applications, and challenges of mechanotransduction in human diseases are also summarized and discussed. Together, this knowledge from a hierarchical perspective has the potential to refresh insights into mechanotransduction regulation and disease pathogenesis and therapy, and ultimately revolutionize the prevention, diagnosis, and treatment of human diseases.

Bibliometric and visualized analysis of hydrogels in organoids research

Over the past decades, there has been ongoing effort to develop complex biomimetic tissue engineering strategies for in vitro cultivation and maintenance of organoids. The defined hydrogels can create organoid models for various organs by changing their properties and various active molecules. An increasing number of researches has been done on the application of hydrogels in organoids, and a large number of articles have been published on the topic. Although there have been existing reviews describing the application of hydrogels in the field of organoids, there is still a lack of comprehensive studies summarizing and analyzing the overall research trends in this field. The citation can be used as an indicator of the scientific influence of an article in its field. This study aims to evaluate the application of hydrogels in organoids through bibliometric analysis, and to predict the hotspots and developing trends in this field.

Induction of lung progenitor cell-like organoids by porcine pluripotent stem cells

Organoids are in vitro 3D models that are generated using stem cells to study organ development and regeneration. Despite the extensive research on lung organoids, there is limited information on pig lung cell generation or development. Here, we identified five epithelial cell types along with their characteristic markers using scRNA-seq. Additionally, we found that NKX2.1 and FOXA2 acted as the crucial core transcription factors in porcine lung development. The presence of SOX9/SOX2 double-positive cells was identified as a key marker for lung progenitor cells. The Monocle algorithm was used to create a pseudo-temporal differentiation trajectory of epithelial cells, leading to the identification of signaling pathways related to porcine lung development. Moreover, we established the differentiation method from porcine pluripotent stem cells (pPSCs) to SOX17+ FOXA2+ definitive endoderm (DE) and NKX2.1+ FOXA2+ CDX2- anterior foregut endoderm (AFE). The AFE is further differentiated into lung organoids while closely monitoring the differentiation process. We showed that NKX2.1 overexpression facilitated the induction of lung organoids and supported subsequent lung differentiation and maturation. This model offers valuable insights into studying the interaction patterns between cells and the signaling pathways during the development of the porcine lung.

Patient-derived organoids in human cancer: a platform for fundamental research and precision medicine

Cancer is associated with a high degree of heterogeneity, encompassing both inter- and intra-tumor heterogeneity, along with considerable variability in clinical response to common treatments across patients. Conventional models for tumor research, such as in vitro cell cultures and in vivo animal models, demonstrate significant limitations that fall short of satisfying the research requisites. Patient-derived tumor organoids, which recapitulate the structures, specific functions, molecular characteristics, genomics alterations and expression profiles of primary tumors. They have been efficaciously implemented in illness portrayal, mechanism exploration, high-throughput drug screening and assessment, discovery of innovative therapeutic targets and potential compounds, and customized treatment regimen for cancer patients. In contrast to conventional models, tumor organoids offer an intuitive, dependable, and efficient in vitro research model by conserving the phenotypic, genetic diversity, and mutational attributes of the originating tumor. Nevertheless, the organoid technology also confronts the bottlenecks and challenges, such as how to comprehensively reflect intra-tumor heterogeneity, tumor microenvironment, tumor angiogenesis, reduce research costs, and establish standardized construction processes while retaining reliability. This review extensively examines the use of tumor organoid techniques in fundamental research and precision medicine. It emphasizes the importance of patient-derived tumor organoid biobanks for drug development, screening, safety evaluation, and personalized medicine. Additionally, it evaluates the application of organoid technology as an experimental tumor model to better understand the molecular mechanisms of tumor. The intent of this review is to explicate the significance of tumor organoids in cancer research and to present new avenues for the future of tumor research.

Cryopreservation of organoids: Strategies, innovation, and future prospects

Organoid technology has demonstrated unique advantages in multidisciplinary fields such as disease research, tumor drug sensitivity, clinical immunity, drug toxicology, and regenerative medicine. It will become the most promising research tool in translational research. However, the long preparation time of organoids and the lack of high-quality cryopreservation methods limit the further application of organoids. Although the high-quality cryopreservation of small-volume biological samples such as cells and embryos has been successfully achieved, the existing cryopreservation methods for organoids still face many bottlenecks. In recent years, with the development of materials science, cryobiology, and interdisciplinary research, many new materials and methods have been applied to cryopreservation. Several new cryopreservation methods have emerged, such as cryoprotectants (CPAs) of natural origin, ice-controlled biomaterials, and rapid rewarming methods. The introduction of these technologies has expanded the research scope of cryopreservation of organoids, provided new approaches and methods for cryopreservation of organoids, and is expected to break through the current technical bottleneck of cryopreservation of organoids. This paper reviews the progress of cryopreservation of organoids in recent years from three aspects: damage factors of cryopreservation of organoids, new protective agents and loading methods, and new technologies of cryopreservation and rewarming.

Small Joint Organoids 3D Bioprinting: Construction Strategy and Application

Osteoarthritis (OA) is a chronic disease that causes pain and disability in adults, affecting ≈300 million people worldwide. It is caused by damage to cartilage, including cellular inflammation and destruction of the extracellular matrix (ECM), leading to limited self-repairing ability due to the lack of blood vessels and nerves in the cartilage tissue. Organoid technology has emerged as a promising approach for cartilage repair, but constructing joint organoids with their complex structures and special mechanisms is still challenging. To overcome these boundaries, 3D bioprinting technology allows for the precise design of physiologically relevant joint organoids, including shape, structure, mechanical properties, cellular arrangement, and biological cues to mimic natural joint tissue. In this review, the authors will introduce the biological structure of joint tissues, summarize key procedures in 3D bioprinting for cartilage repair, and propose strategies for constructing joint organoids using 3D bioprinting. The authors also discuss the challenges of using joint organoids' approaches and perspectives on their future applications, opening opportunities to model joint tissues and response to joint disease treatment.

Engineering Heterogeneous Tumor Models for Biomedical Applications

Tumor tissue engineering holds great promise for replicating the physiological and behavioral characteristics of tumors in vitro. Advances in this field have led to new opportunities for studying the tumor microenvironment and exploring potential anti-cancer therapeutics. However, the main obstacle to the widespread adoption of tumor models is the poor understanding and insufficient reconstruction of tumor heterogeneity. In this review, the current progress of engineering heterogeneous tumor models is discussed. First, the major components of tumor heterogeneity are summarized, which encompasses various signaling pathways, cell proliferations, and spatial configurations. Then, contemporary approaches are elucidated in tumor engineering that are guided by fundamental principles of tumor biology, and the potential of a bottom-up approach in tumor engineering is highlighted. Additionally, the characterization approaches and biomedical applications of tumor models are discussed, emphasizing the significant role of engineered tumor models in scientific research and clinical trials. Lastly, the challenges of heterogeneous tumor models in promoting oncology research and tumor therapy are described and key directions for future research are provided.

Engineering Biomimetic Microenvironment for Organoid

Organoid is an emerging frontier technology in the field of life science, in which pluripotent stem cells or tissue-derived differentiated/progenitor cells form 3D structures according to their multi-directional differentiation potential and self-assembly ability. Nowadays, although various types of organoids are widely investigated, their construction is still complicated in operation, uncertain in yield, and poor in reproducibility for the structure and function of native organs. Constructing a biomimetic microenvironment for stem cell proliferation and differentiation in vitro is recognized as a key to driving this field. This review reviews the recent development of engineered biomimetic microenvironments for organoids. First, the composition of the matrix for organoid culture is summarized. Then, strategies for engineering the microenvironment from biophysical, biochemical, and cellular perspectives are discussed in detail. Subsequently, the newly developed monitoring technologies are also reviewed. Finally, a brief conclusion and outlook are presented for the inspiration of future research.

Biomimetic cell culture for cell adhesive propagation for tissue engineering strategies

Biomimetic cell culture, which involves creating a biomimetic microenvironment for cells in vitro by engineering approaches, has aroused increasing interest given that it maintains the normal cellular phenotype, genotype and functions displayed in vivo. Therefore, it can provide a more precise platform for disease modelling, drug development and regenerative medicine than the conventional plate cell culture. In this review, initially, we discuss the principle of biomimetic cell culture in terms of the spatial microenvironment, chemical microenvironment, and physical microenvironment. Then, the main strategies of biomimetic cell culture and their state-of-the-art progress are summarized. To create a biomimetic microenvironment for cells, a variety of strategies has been developed, ranging from conventional scaffold strategies, such as macroscopic scaffolds, microcarriers, and microgels, to emerging scaffold-free strategies, such as spheroids, organoids, and assembloids, to simulate the native cellular microenvironment. Recently, 3D bioprinting and microfluidic chip technology have been applied as integrative platforms to obtain more complex biomimetic structures. Finally, the challenges in this area are discussed and future directions are discussed to shed some light on the community.

Factors Influencing Microbiota in Modulating Vaccine Immune Response: A Long Way to Go

Vaccine immunogenicity still represents an unmet need in specific populations, such as people from developing countries and "edge populations". Both intrinsic and extrinsic factors, such as the environment, age, and dietary habits, influence cellular and humoral immune responses. The human microbiota represents a potential key to understanding how these factors impact the immune response to vaccination, with its modulation being a potential step to address vaccine immunogenicity. The aim of this narrative review is to explore the intricate interactions between the microbiota and the immune system in response to vaccines, highlighting the state of the art in gut microbiota modulation as a novel therapeutic approach to enhancing vaccine immunogenicity and laying the foundation for future, more solid data for its translation to the clinical practice.

Vascular organoids: unveiling advantages, applications, challenges, and disease modelling strategies

Understanding mechanisms and manifestations of cardiovascular risk factors, including diabetes, on vascular cells such as endothelial cells, pericytes, and vascular smooth muscle cells, remains elusive partly due to the lack of appropriate disease models. Therefore, here we explore different aspects for the development of advanced 3D in vitro disease models that recapitulate human blood vessel complications using patient-derived induced pluripotent stem cells, which retain the epigenetic, transcriptomic, and metabolic memory of their patient-of-origin. In this review, we highlight the superiority of 3D blood vessel organoids over conventional 2D cell culture systems for vascular research. We outline the key benefits of vascular organoids in both health and disease contexts and discuss the current challenges associated with organoid technology, providing potential solutions. Furthermore, we discuss the diverse applications of vascular organoids and emphasize the importance of incorporating all relevant cellular components in a 3D model to accurately recapitulate vascular pathophysiology. As a specific example, we present a comprehensive overview of diabetic vasculopathy, demonstrating how the interplay of different vascular cell types is critical for the successful modelling of complex disease processes in vitro. Finally, we propose a strategy for creating an organ-specific diabetic vasculopathy model, serving as a valuable template for modelling other types of vascular complications in cardiovascular diseases by incorporating disease-specific stressors and organotypic modifications.

Recent advances in defined hydrogels in organoid research

Organoids are in vitro model systems that mimic the complexity of organs with multicellular structures and functions, which provide great potential for biomedical and tissue engineering. However, their current formation heavily relies on using complex animal-derived extracellular matrices (ECM), such as Matrigel. These matrices are often poorly defined in chemical components and exhibit limited tunability and reproducibility. Recently, the biochemical and biophysical properties of defined hydrogels can be precisely tuned, offering broader opportunities to support the development and maturation of organoids. In this review, the fundamental properties of ECM in vivo and critical strategies to design matrices for organoid culture are summarized. Two typically defined hydrogels derived from natural and synthetic polymers for their applicability to improve organoids formation are presented. The representative applications of incorporating organoids into defined hydrogels are highlighted. Finally, some challenges and future perspectives are also discussed in developing defined hydrogels and advanced technologies toward supporting organoid research.

A microwell platform for high-throughput longitudinal phenotyping and selective retrieval of organoids

Organoids are powerful experimental models for studying the ontogeny and progression of various diseases including cancer. Organoids are conventionally cultured in bulk using an extracellular matrix mimic. However, bulk-cultured organoids physically overlap, making it impossible to track the growth of individual organoids over time in high throughput. Moreover, local spatial variations in bulk matrix properties make it difficult to assess whether observed phenotypic heterogeneity between organoids results from intrinsic cell differences or differences in the microenvironment. Here, we developed a microwell-based method that enables high-throughput quantification of image-based parameters for organoids grown from single cells, which can further be retrieved from their microwells for molecular profiling. Coupled with a deep learning image-processing pipeline, we characterized phenotypic traits including growth rates, cellular movement, and apical-basal polarity in two CRISPR-engineered human gastric organoid models, identifying genomic changes associated with increased growth rate and changes in accessibility and expression correlated with apical-basal polarity. A record of this paper's transparent peer review process is included in the supplemental information.

Induction of Metabolic Reprogramming in Kidney by Singlet Diradical Nanoparticles

Polycyclic aromatic compounds with an open-shell singlet diradical ground state, namely singlet diradicals, have recently gained attention in the fields of organic electronics, photovoltaics, and spintronics owing to their unique electronic structures and properties. Notably, singlet diradicals exhibit tunable redox amphoterism, which makes them excellent redox-active materials for biomedical applications. However, the safety and therapeutic efficacy of singlet diradicals in biological systems have not yet been explored. Herein, the study presents a newly designed singlet diradical nanomaterial, diphenyl-substituted biolympicenylidene (BO-Ph), exhibiting low cytotoxicity in vitro, non-significant acute nephrotoxicity in vivo, and the ability to induce metabolic reprogramming in kidney organoids. Integrated transcriptome and metabolome analyses reveal that the metabolism of BO-Ph stimulates glutathione (GSH) synthesis and fatty acid degradation, increases the levels of intermediates in the tricarboxylic acid (TCA) and carnitine cycles, and eventually boosts oxidative phosphorylation (OXPHOS) under redox homeostasis. Benefits of BO-Ph-induce metabolic reprogramming in kidney organoids include enhancing cellular antioxidant capacity and promoting mitochondrial function. The results of this study can facilitate the application of singlet diradical materials in the treatment of clinical conditions induced by mitochondrial abnormalities in kidney.

Advances in Microgravity Directed Tissue Engineering

Tissue engineering aims to generate functional biological substitutes to repair, sustain, improve, or replace tissue function affected by disease. With the rapid development of space science, the application of simulated microgravity has become an active topic in the field of tissue engineering. There is a growing body of evidence demonstrating that microgravity offers excellent advantages for tissue engineering by modulating cellular morphology, metabolism, secretion, proliferation, and stem cell differentiation. To date, there have been many achievements in constructing bioartificial spheroids, organoids, or tissue analogs with or without scaffolds in vitro under simulated microgravity conditions. Herein, the current status, recent advances, challenges, and prospects of microgravity related to tissue engineering are reviewed. Current simulated-microgravity devices and cutting-edge advances of microgravity for biomaterials-dependent or biomaterials-independent tissue engineering to offer a reference for guiding further exploration of simulated microgravity strategies to produce engineered tissues are summarized and discussed.

Three-Dimensional Cell Cultures: The Bridge between In Vitro and In Vivo Models

Although historically, the traditional bidimensional in vitro cell system has been widely used in research, providing much fundamental information regarding cellular functions and signaling pathways as well as nuclear activities, the simplicity of this system does not fully reflect the heterogeneity and complexity of the in vivo systems. From this arises the need to use animals for experimental research and in vivo testing. Nevertheless, animal use in experimentation presents various aspects of complexity, such as ethical issues, which led Russell and Burch in 1959 to formulate the 3R (Replacement, Reduction, and Refinement) principle, underlying the urgent need to introduce non-animal-based methods in research. Considering this, three-dimensional (3D) models emerged in the scientific community as a bridge between in vitro and in vivo models, allowing for the achievement of cell differentiation and complexity while avoiding the use of animals in experimental research. The purpose of this review is to provide a general overview of the most common methods to establish 3D cell culture and to discuss their promising applications. Three-dimensional cell cultures have been employed as models to study both organ physiology and diseases; moreover, they represent a valuable tool for studying many aspects of cancer. Finally, the possibility of using 3D models for drug screening and regenerative medicine paves the way for the development of new therapeutic opportunities for many diseases.

Graphene Hybrid Inner Ear Organoid with Enhanced Maturity

Inner ear organoids (IEOs) are 3D structures grown in vitro, which can mimic the complex cellular structure and function of the inner ear. IEOs are potential solutions to problems related to inner ear development, disease modeling, and drug delivery. However, current approaches in generating IEOs using chemical factors have a few limitations, resulting in unpredictable outcomes. In this study, we propose the use of nanomaterial-based approaches, specifically by using graphene oxide (GO). GO's unique properties promote cell-extracellular matrix interactions and cell-cell gap junctions, thereby enhancing hair cell formation, which is an essential part of IEO development. We also investigated the potential applications for drug testing. Our findings suggest that GO is a promising candidate for enhancing the functionality of IEOs and advancing our understanding of the problems underlying inner ear development. The use of nanomaterial-based approaches may provide a more reliable and effective method for building better IEOs in the future.

Three-dimensional-cultured MSC-derived exosome with hydrogel for cerebral ischemia repair

Microglia-mediated neuroinflammatory response, one of the most essential pathological processes of cerebral ischemia-reperfusion (I/R) injury, is acknowledged as the main factors leading to poor prognosis of cerebral ischemia. Exosome derived from mesenchymal stem cell (MSC-Exo) exhibits neuroprotective functions by reducing cerebral ischemia-induced neuroinflammatory response and promoting angiogenesis. However, MSC-Exo has disadvantages such as insufficient targeting capability and low production, which limits their clinical applications. Here, we fabricated gelatin methacryloyl (GelMA) hydrogel for three-dimensional (3D) culture of MSCs. It is indicated that 3D environment could simulate the biological niches of MSCs, thereby significantly increasing the cell stemness of MSCs and improving the yield of MSCs-derived exosomes (3D-Exo). In this study, we utilized the modified Longa method to induce middle cerebral artery occlusion (MCAO) model. Additionally, in vitro and in vivo studies were conducted to interrogate the mechanism of the stronger neuroprotective effect of 3D-Exo. Furthermore, the administration of 3D-Exo in MCAO model could promote neovascularization in infarct region and result in a significant suppression of inflammatory response. This study proposed an exosome-based targeting delivery system for cerebral ischemia and provided a promising strategy for efficient and large-scale production of MSC-Exo.

Progress of research on tumor organoids: A bibliometric analysis of relevant publications from 2011 to 2021

Background

Research on tumor organoids has developed rapidly over the past 20 years, but a systematic analysis of current research trends is lacking. Researchers in the field need relevant references and knowledge of current research hot spots. Bibliometric analysis and visualization is a systematic method of acquiring an in-depth understanding of the status of research on tumor organoids.

Methods

CiteSpace, VOSviewer and the Bibliometric Online Analysis Platform from the Web of Science Core Collection were used to analyze and predict publishing trends and research hot spots worldwide in the field of tumor organoids.

Results

A total of 3,666 publications on tumor organoids were retrieved, and 2,939 eligible articles were included in the final analysis. The number of publications has grown significantly, with the United States of America as the leading country for research on tumor organoids. Among journals, Cancers published the largest number of articles. Harvard Medical School published the highest number of articles among all institutions. The Chinese Academy of Sciences was ranked highest among all contributing institutions on the importance of their publications. A trend in multi-disciplinary collaboration was observed in studies on tumor organoids. Keywords indicated that the current research largely concentrated on optimizing the construction of organoid models to use for medication development and screening in the clinical setting, and to provide patients with individualized treatment for gastric cancer and colorectal cancer, which are newly emerging research hotspots. Gastric and colorectal cancers were the top two tumors that have received increasing attention and have become the focal points of recent studies.

Conclusion

This study analyzed 2,939 publications covering the topic of tumor organoids. Although optimizing the construction of organoid models has always been a hot topic in this field, the application of tumor organoids to the development of medications and screenings will foster individualized treatment for patients, which is another emerging hot spot in this field of research.

Bioengineering Liver Organoids for Diseases Modelling and Transplantation

Organoids as three-dimension (3D) cellular organizations partially mimic the physiological functions and micro-architecture of native tissues and organs, holding great potential for clinical applications. Advances in the identification of essential factors including physical cues and biochemical signals for controlling organoid development have contributed to the success of growing liver organoids from liver tissue and stem/progenitor cells. However, to recapitulate the physiological properties and the architecture of a native liver, one has to generate liver organoids that contain all the major liver cell types in correct proportions and relative 3D locations as found in a native liver. Recent advances in stem-cell-, biomaterial- and engineering-based approaches have been incorporated into conventional organoid culture methods to facilitate the development of a more sophisticated liver organoid culture resembling a near to native mini-liver in a dish. However, a comprehensive review on the recent advancement in the bioengineering liver organoid is still lacking. Here, we review the current liver organoid systems, focusing on the construction of the liver organoid system with various cell sources, the roles of growth factors for engineering liver organoids, as well as the recent advances in the bioengineering liver organoid disease models and their biomedical applications.

Organoids

Organoids have attracted increasing attention because they are simple tissue-engineered cell-based in vitro models that recapitulate many aspects of the complex structure and function of the corresponding in vivo tissue. They can be dissected and interrogated for fundamental mechanistic studies on development, regeneration, and repair in human tissues. Organoids can also be used in diagnostics, disease modeling, drug discovery, and personalized medicine. Organoids are derived from either pluripotent or tissue-resident stem (embryonic or adult) or progenitor or differentiated cells from healthy or diseased tissues, such as tumors. To date, numerous organoid engineering strategies that support organoid culture and growth, proliferation, differentiation and maturation have been reported. This Primer serves to highlight the rationale underlying the selection and development of these materials and methods to control the cellular/tissue niche; and therefore, structure and function of the engineered organoid. We also discuss key considerations for generating robust organoids, such as those related to cell isolation and seeding, matrix and soluble factor selection, physical cues and integration. The general standards for data quality, reproducibility and deposition within the organoid community is also outlined. Lastly, we conclude by elaborating on the limitations of organoids in different applications, and key priorities in organoid engineering for the coming years.

Macrophage autophagy in macrophage polarization, chronic inflammation and organ fibrosis

As the essential regulators of organ fibrosis, macrophages undergo marked phenotypic and functional changes after organ injury. These changes in macrophage phenotype and function can result in maladaptive repair, causing chronic inflammation and the development of pathological fibrosis. Autophagy, a highly conserved lysosomal degradation pathway, is one of the major players to maintain the homeostasis of macrophages through clearing protein aggregates, damaged organelles, and invading pathogens. Emerging evidence has shown that macrophage autophagy plays an essential role in macrophage polarization, chronic inflammation, and organ fibrosis. Because of the high heterogeneity of macrophages in different organs, different macrophage types may play different roles in organ fibrosis. Here, we review the current understanding of the function of macrophage autophagy in macrophage polarization, chronic inflammation, and organ fibrosis in different organs, highlight the potential role of macrophage autophagy in the treatment of fibrosis. Finally, the important unresolved issues in this field are briefly discussed. A better understanding of the mechanisms that macrophage autophagy in macrophage polarization, chronic inflammation, and organ fibrosis may contribute to developing novel therapies for chronic inflammatory diseases and organ fibrosis.

High-Content Screening and Analysis of Stem Cell-Derived Neural Interfaces Using a Combinatorial Nanotechnology and Machine Learning Approach

A systematic investigation of stem cell-derived neural interfaces can facilitate the discovery of the molecular mechanisms behind cell behavior in neurological disorders and accelerate the development of stem cell-based therapies. Nevertheless, high-throughput investigation of the cell-type-specific biophysical cues associated with stem cell-derived neural interfaces continues to be a significant obstacle to overcome. To this end, we developed a combinatorial nanoarray-based method for high-throughput investigation of neural interface micro-/nanostructures (physical cues comprising geometrical, topographical, and mechanical aspects) and the effects of these complex physical cues on stem cell fate decisions. Furthermore, by applying a machine learning (ML)-based analytical approach to a large number of stem cell-derived neural interfaces, we comprehensively mapped stem cell adhesion, differentiation, and proliferation, which allowed for the cell-type-specific design of biomaterials for neural interfacing, including both adult and human-induced pluripotent stem cells (hiPSCs) with varying genetic backgrounds. In short, we successfully demonstrated how an innovative combinatorial nanoarray and ML-based platform technology can aid with the rational design of stem cell-derived neural interfaces, potentially facilitating precision, and personalized tissue engineering applications.

Lung Cancer Organoids: The Rough Path to Personalized Medicine

Simple Summary

Lung cancer is very difficult to cure, especially when it has spread to other parts of the body. One of the main reasons that delay the identification of effective therapies is the complexity of lung cancer cells, which can be very different among individual patients. Organoids are small aggregates of tumor cells that are generated from lung tumors and used in cancer research laboratories to study the features of tumor cells. Organoids have unique properties, as they reproduce many characteristics of the tumor derived from each specific patient. Due to their capacity to reproduce individual tumor features in the laboratory setting, organoids are an excellent system to study lung cancer and to identify functional therapies. This review summarizes the challenges encountered by researchers in the field of lung cancer organoids and describes how the advances in organoid technology may allow the future development of individualized therapies for lung cancer patients.

Abstract

Lung cancer is the leading cause of cancer death worldwide. Despite significant advances in research and therapy, a dismal 5-year survival rate of only 10–20% urges the development of reliable preclinical models and effective therapeutic tools. Lung cancer is characterized by a high degree of heterogeneity in its histology, a genomic landscape, and response to therapies that has been traditionally difficult to reproduce in preclinical models. However, the advent of three-dimensional culture technologies has opened new perspectives to recapitulate in vitro individualized tumor features and to anticipate treatment efficacy. The generation of lung cancer organoids (LCOs) has encountered greater challenges as compared to organoids derived from other tumors. In the last two years, many efforts have been dedicated to optimizing LCO-based platforms, resulting in improved rates of LCO production, purity, culture timing, and long-term expansion. However, due to the complexity of lung cancer, further advances are required in order to meet clinical needs. Here, we discuss the evolution of LCO technology and the use of LCOs in basic and translational lung cancer research. Although the field of LCOs is still in its infancy, its prospective development will likely lead to new strategies for drug testing and biomarker identification, thus allowing a more personalized therapeutic approach for lung cancer patients.

Advances of Engineered Hydrogel Organoids within the Stem Cell Field: A Systematic Review

Organoids are novel in vitro cell culture models that enable stem cells (including pluripotent stem cells and adult stem cells) to grow and undergo self-organization within a three-dimensional microenvironment during the process of differentiation into target tissues. Such miniature structures not only recapitulate the histological and genetic characteristics of organs in vivo, but also form tissues with the capacity for self-renewal and further differentiation. Recent advances in biomaterial technology, particularly hydrogels, have provided opportunities to improve organoid cultures; by closely integrating the mechanical and chemical properties of the extracellular matrix microenvironment, with novel synthetic materials and stem cell biology. This systematic review critically examines recent advances in various strategies and techniques utilized for stem-cell-derived organoid culture, with particular emphasis on the application potential of hydrogel technology in organoid culture. We hope this will give a better understanding of organoid cultures for modelling diseases and tissue engineering applications.

Bioelectric Potential in Next-Generation Organoids: Electrical Stimulation to Enhance 3D Structures of the Central Nervous System

Pluripotent stem cell-derived organoid models of the central nervous system represent one of the most exciting areas in in vitro tissue engineering. Classically, organoids of the brain, retina and spinal cord have been generated via recapitulation of in vivo developmental cues, including biochemical and biomechanical. However, a lesser studied cue, bioelectricity, has been shown to regulate central nervous system development and function. In particular, electrical stimulation of neural cells has generated some important phenotypes relating to development and differentiation. Emerging techniques in bioengineering and biomaterials utilise electrical stimulation using conductive polymers. However, state-of-the-art pluripotent stem cell technology has not yet merged with this exciting area of bioelectricity. Here, we discuss recent findings in the field of bioelectricity relating to the central nervous system, possible mechanisms, and how electrical stimulation may be utilised as a novel technique to engineer “next-generation” organoids.

Engineering mammalian living materials towards clinically relevant therapeutics

Engineered living materials represent a new generation of human-made biotherapeutics that are highly attractive for a myriad of medical applications. In essence, such cell-rich platforms provide encodable bioactivities with extended lifetimes and environmental multi-adaptability currently unattainable in conventional biomaterial platforms. Emerging cell bioengineering tools are herein discussed from the perspective of materializing living cells as cooperative building blocks that drive the assembly of multiscale living materials. Owing to their living character, pristine cellular units can also be imparted with additional therapeutically-relevant biofunctionalities. On this focus, the most recent advances on the engineering of mammalian living materials and their biomedical applications are herein outlined, alongside with a critical perspective on major roadblocks hindering their realistic clinical translation. All in all, transposing the concept of leveraging living materials as autologous tissue-building entities and/or self-regulated biotherapeutics opens new realms for improving precision and personalized medicine strategies in the foreseeable future.