Microtechnology-based methods for organoid models

Emerging biotechnologies for engineering liver organoids

The engineering construction of the liver has attracted enormous attention. Organoids, as emerging miniature three-dimensional cultivation units, hold significant potential in the biomimetic simulation of liver structure and function. Despite notable successes, organoids still face limitations such as high variability and low maturity. To overcome these challenges, engineering strategies have been established to maintain organoid stability and enhance their efficacy, laying the groundwork for the development of advanced liver organoids. The present review comprehensively summarizes the construction of engineered liver organoids and their prospective applications in biomedicine. Initially, we briefly present the latest research progress on matrix materials that maintain the three-dimensional morphology of organoids. Next, we discuss the manipulative role of engineering technologies in organoid assembly. Additionally, we outline the impact of gene-level regulation on organoid growth and development. Further, we introduce the applications of liver organoids in disease modeling, drug screening and regenerative medicine. Lastly, we overview the current obstacles and forward-looking perspectives on the future of engineered liver organoids. We anticipate that ongoing innovations in engineered liver organoids will lead to significant advancements in medical applications.

Neurochemical and Morphological Comparisons of Motor Nerve Organoids and Spinal-Cord Explants

Organoids are multicellular structures formed in vitro from populations of individual cells allowing modeling of structural and functional aspects of organs and tissues in normal and diseased states. They offer unique opportunities to model and treat disease. Using a mouse embryonic stem cell line, we have cultured organoids that express markers of spinal cord motor neurons as well as motor neurons found within the peripheral nervous system. The morphology and select neurotransmitter content of the organoids and spinal cord explants were compared at different developmental time points. We found indications of maturation in the organoids over time, mirrored by similar trends in the spinal cord explants. Although the organoids contained the same neurotransmitters as the spinal cord explants, the developmental changes of these neurotransmitter levels were less marked in organoids. Given these differences, further work is required to optimize organoid growth conditions to better reproduce in vivo models when using organoids to study development.

Dynamic Diselenide Hydrogels for Controlled Tumor Organoid Culture and Dendritic Cell Vaccination

Dynamic hydrogels are emerging as advanced materials for engineering tissue-like environments that mimic cellular microenvironments. We introduce a diselenide-cross-linked hydrogel system with light-responsive properties, designed for precise control of tumor organoid growth and light-initiated radical inactivation, particularly for dendritic cell (DC) vaccines. Diselenide exchange enables stress relaxation and hydrogel remodeling, while recombination and quenching of seleno radicals (Se•) reduce cross-linking density, leading to controlled degradation. We demonstrate a 2D to 3D growth strategy, where tumor cells inoculate on the hydrogel surface, expand, and gradually form spherical organoids within the 3D hydrogel. These tumor organoids show significantly higher drug resistance compared to 2D-cultured cells. High-density light irradiation enhances diselenide exchange, inducing hydrogel degradation, tumor cell death, and release of functional antigens. This system serves as a dynamic platform for tumor organoid culture and antigen release, offering significantly advanced approaches for in vitro tumor modeling and immunological research. Our findings position diselenide-cross-linked hydrogels as versatile materials for precision cellular engineering, with broad applications in cancer research and beyond.

Standardization and optimization of the hiPSC-based PluriLum assay for detection of embryonic and developmental toxicants

New approach methodologies (NAMs) for predicting embryotoxicity and developmental toxicity are urgently needed for generating human relevant data, while reducing turnover time and costs, and alleviating ethical concerns related to the use of animal models. We have previously developed the PluriLum assay, a NKX2.5-reporter gene 3D model using human-induced pluripotent stem cells (hiPSCs) that are genetically modified to enable the assessment of adverse effects of chemicals on the early-stage embryo. Aiming at improving the predictive value of the PluriLum assay for future screening purposes, we sought to introduce standardization steps to the protocol, improving the overall robustness of the PluriLum assay, as well as a shortening of the assay protocol. First, we showed that the initial size of embryoid bodies (EBs) is crucial for a proper differentiation into cardiomyocytes and overall reproducibility of the assay. When the starting diameter of the EBs exceeds 500 µm, robust differentiation can be anticipated. In terms of reproducibility, exposure to the fungicide epoxiconazole at smaller initial diameters resulted in a larger variation of the derived data, compared to more reliable concentration-response curves obtained using spheroids with larger initial diameters. We further investigated the ideal length of the differentiation protocol, resulting in a shortening of the PluriLum assay by 24 h to 7 days. Following exposure to the teratogens all-trans and 13-cis retinoic acid, both cardiomyocyte contraction and measurement of NKX2.5-derived luminescence were recorded with a similar or increased sensitivity after 6 days of differentiation when compared to the original 7 days. Finally, we have introduced an efficient step for enzymatic dissociation of the EBs at assay termination. This allows for an even splitting of the individual EBs and testing of additional endpoints other than the NKX2.5-luciferase reporter, which was demonstrated in this work by the simultaneous assessment of ATP levels. In conclusion, we have introduced standardizations and streamlined the PluriLum assay protocol to improve its suitability as a NAM for screening of a large number of chemicals for developmental toxicity testing.

Integration of secreted signaling molecule sensing on cell monitoring platforms: a critical review

Monitoring cell secretion in complex microenvironments is crucial for understanding cellular behavior and advancing physiological and pathological research. While traditional cell culture methods, including organoids and spheroids, provide valuable models, real-time monitoring of cell secretion of signaling molecules remains challenging. Integrating advanced monitoring technologies into these systems often disrupts the delicate balance of the microenvironment, making it difficult to achieve sensitivity and specificity. This review explored recent strategies for integrating the monitoring of cell secretion of signaling molecules, crucial for understanding and replicating cell microenvironments, within cell culture platforms, addressing challenges such as non-adherent cell models and the focus on single-cell methodologies. We highlight advancements in biosensors, microfluidics, and three-dimensional culture methods, and discuss their potential to enhance real-time, multiplexed cell monitoring. By examining the advantages, limitations, and future prospects of these technologies, we aim to contribute to the development of integrated systems that facilitate comprehensive cell monitoring, ultimately advancing biological research and pharmaceutical development.

Potential Use of Organoids in Regenerative Medicine

BACKGROUND

In vitro cell culture is crucial for studying human diseases and development. Compared to traditional monolayer cultures, 3D culturing with organoids offers significant advantages by more accurately replicating natural tissues' structural and functional features. This advancement enhances disease modeling, drug testing, and regenerative medicine applications. Organoids, derived from stem cells, mimic tissue physiology in a more relevant manner. Despite their promise, the clinical use of regenerative medicine currently needs to be improved by reproducibility, scalability, and maturation issues.

METHODS

This article overviews recent organoid research, focusing on their types, sources, 3D culturing methods, and applications in regenerative medicine. A literature review of "organoid" and "regenerative medicine" in PubMed/MEDLINE highlighted relevant studies published over the past decade, emphasizing human-sourced organoids and their regenerative benefits, as well as the availability of free full-text articles. The review uses descriptive data, including tables and text, to illustrate the challenges and potential of organoids in regenerative medicine.

RESULTS

The transition from 2D to 3D models, particularly organoids, has significantly advanced in vitro research. This review covers a decade of progress in various organoid types-such as liver, cholangiocyte, intestinal, pancreatic, cardiac, brain, thymus, and mammary organoids-and their 3D culture methods and applications. It addresses critical issues of maturity, scalability, and reproducibility and underscores the need for standardization and improved production techniques to facilitate broader clinical applications in regenerative medicine.

CONCLUSIONS

Successful therapy requires increased scalability and standardization. Organoids have enormous potential in biological research, notwithstanding obstacles.

Advancing cancer research through organoid technology

The complexity of tumors and the challenges associated with treatment often stem from the limitations of existing models in accurately replicating authentic tumors. Recently, organoid technology has emerged as an innovative platform for tumor research. This bioengineering approach enables researchers to simulate, in vitro, the interactions between tumors and their microenvironment, thereby enhancing the intricate interplay between tumor cells and their surroundings. Organoids also integrate multidimensional data, providing a novel paradigm for understanding tumor development and progression while facilitating precision therapy. Furthermore, advancements in imaging and genetic editing techniques have significantly augmented the potential of organoids in tumor research. This review explores the application of organoid technology for more precise tumor simulations and its specific contributions to cancer research advancements. Additionally, we discuss the challenges and evolving trends in developing comprehensive tumor models utilizing organoid technology.

Advances and Challenges of Bioassembly Strategies in Neurovascular In Vitro Modeling: An Overview of Current Technologies with a Focus on Three-Dimensional Bioprinting

Bioassembly encompasses various techniques such as bioprinting, microfluidics, organoids, and self-assembly, enabling advances in tissue engineering and regenerative medicine. Advancements in bioassembly technologies have enabled the precise arrangement and integration of various cell types to more closely mimic the complexity functionality of the neurovascular unit (NVU) and that of other biodiverse multicellular tissue structures. In this context, bioprinting offers the ability to deposit cells in a spatially controlled manner, facilitating the construction of interconnected networks. Scaffold-based assembly strategies provide structural support and guidance cues for cell growth, enabling the formation of complex bio-constructs. Self-assembly approaches utilize the inherent properties of cells to drive the spontaneous organization and interaction of neuronal and vascular components. However, recreating the intricate microarchitecture and functional characteristics of a tissue/organ poses additional challenges. Advancements in bioassembly techniques and materials hold great promise for addressing these challenges. The further refinement of bioprinting technologies, such as improved resolution and the incorporation of multiple cell types, can enhance the accuracy and complexity of the biological constructs; however, developing bioinks that support the growth of cells, viability, and functionality while maintaining compatibility with the bioassembly process remains an unmet need in the field, and further advancements in the design of bioactive and biodegradable scaffolds will aid in controlling cell adhesion, differentiation, and vascularization within the engineered tissue. Additionally, integrating advanced imaging and analytical techniques can provide real-time monitoring and characterization of bioassembly, aiding in quality control and optimization. While challenges remain, ongoing research and technological advancements propel the field forward, paving the way for transformative developments in neurovascular research and tissue engineering. This work provides an overview of the advancements, challenges, and future perspectives in bioassembly for fabricating neurovascular constructs with an add-on focus on bioprinting technologies.

Microdissection tools to generate organoids for modeling the tumor immune microenvironment

Patient-derived tumor organoids have emerged as promising models for predicting personalized drug responses in cancer therapy, but they typically lack immune components. Preserving the in vivo association between tumor cells and endogenous immune cells is critical for accurate testing of cancer immunotherapies. Mechanical dissection of tumor specimens into tumor fragments, as opposed to enzymatic digestion into single cells, is essential for maintaining these native tumor-immune cell spatial relationships. However, conventional mechanical dissection relying on manual mincing is time-consuming and irreproducible. This study describes two microdissection devices, the µDicer and µGrater, to facilitate the generation of intact tumor fragments from mouse B16 melanoma, a common model of human melanoma. The µDicer- and µGrater-cut tumor fragments were used to generate air‒liquid interface (ALI) organoids that copreserve tumor cells with infiltrating immune subsets without artificial reconstitution. The µDicer, consisting of a hexagonal array of silicon microblades, was employed to investigate the effect of organoid size. The viability of ALI organoid immune cells appeared insensitive to organoid sizes exceeding ~400 µm but diminished in organoids ~200 µm in size. The µGrater, consisting of an array of submillimeter holes in stainless steel, was employed to accelerate dissection. For the samples studied, the µGrater was 4.5 times faster than manual mincing. Compared with those generated by manual mincing, ALI organoids generated by the µGrater demonstrated similar viability, immune cell composition, and responses to anti-PD-1 immunotherapy. With further optimization, the µGrater holds potential for integration into clinical workflows to support the advancement of personalized cancer immunotherapy.

Three-dimensional cell culture: Future scope in cancer vaccine development

Three-dimensional (3D) cell culture techniques, which are superior to 2D methods in viability and functionality, are being used to develop innovative cancer vaccines. Tumor spheroids, which are structurally and functionally similar to actual tumors, can be developed using 3D cell culture. These spheroid vaccines have shown superior antitumor immune responses to 2D cell-based vaccines. Dendritic cell vaccines can also be produced more efficiently using 3D cell culture. Personalized cancer vaccines are being developed using 3D cell culture, providing substantial benefits over 2D methods. The more natural conditions of 3D cell culture might promote the expression of tumor antigens not expressed in 2D culture, potentially allowing for more targeted vaccines by co-culturing tumor cells with other cell types. Advanced cancer vaccines using 3D cell cultures are expected soon.

Emerging Landscape of In Vitro Models for Assessing Rheumatoid Arthritis Management

Rheumatoid arthritis (RA) is a complex condition that is influenced by various causes, including immunological, genetic, and environmental factors. Several studies using animal models have documented immune system dysfunction and described the clinical characteristics of the disease. These studies have provided valuable insights into the pathogenesis of inflammatory arthritis and the identification of new targets for treatment. Nevertheless, none of these animal models successfully replicated all the characteristics of RA. Additionally, numerous experimental medications, which were developed based on our enhanced comprehension of the immune system's function in RA, have shown potential in animal research but ultimately proved ineffective during different stages of clinical trials. There have been several novel therapy alternatives, which do not achieve a consistently outstanding therapeutic outcome in all patients. This underscores the importance of employing the progress in in vitro models, particularly 3D models like tissue explants, and diverse multicomponent approaches such as coculture strategies, synovial membrane, articular cartilage, and subchondral bone models that accurately replicate the structural characteristics of RA pathophysiology. These methods are crucial for the advancement of potential therapeutic strategies. This review discusses the latest advancements in in vitro models and their potential to greatly impact research on managing RA.

Low-Cost Robotic Manipulation of Live Microtissues for Cancer Drug Testing

The scarcity of human biopsies available for drug testing is a paramount challenge for developing new therapeutics, disease models, and personalized treatments. Microtechnologies that combine the microscale manipulation of tissues and fluids offer the exciting possibility of miniaturizing both disease models and drug testing workflows on scarce human biopsies. Unfortunately, these technologies presently require microfluidic devices or robotic dispensers that are not widely accessible. We have rapidly-prototyped an inexpensive platform based on an off-the-shelf robot that can microfluidically manipulate live microtissues into/out of culture plates without using complicated accessories such as microscopes or pneumatic controllers. The robot integrates complex functions with a simple, cost-effective and compact construction, allowing placement inside a tissue culture hood for sterile workflows. We demonstrated a proof-of-concept cancer drug evaluation workflow of potential clinical utility using patient tumor biopsies with multiple drugs on 384-well plates. Our user-friendly, low-cost platform promises to make drug testing of microtissues broadly accessible to pharmaceutical, clinical, and biological laboratories.

Teaser

A low-cost robot for handling microtissues and catalyzing their use in cancer drug evaluation and personalized oncology.

In vitro modelling of intramuscular injection site events

INTRODUCTION

Intramuscular (IM) injections deliver a plethora of drugs. The majority of IM-related literature details dissolution and/or pharmacokinetic (PK) studies, using methods with limited assessments of post-injection events that can impact drug fate, and absorption parameters. Food and Drug Association guidelines no longer require preclinical in vivo modeling in the U.S.A. Preclinical animal models fail to correlate with clinical outcomes, highlighting the need to study, and understand, IM drug fate in vitro using bespoke models emulating human IM sites. Post-IM injection events, i.e. underlying processes that influence PK outcomes, remain unacknowledged, complicating the application of in vitro methods in preclinical drug development. Understanding such events could guide approaches to predict and modulate IM drug fate in humans.

AREAS COVERED

This article reviews challenges in biorelevant IM site modeling (i.e. modeling drug fate outcomes), the value of technologies available for developing IM injectables, methods for studying drug fate, and technologies for training in performing IM administrations. PubMed, Web-of-Science, and Lens databases provided papers published between 2014 and 2024.

EXPERT OPINION

IM drug research is expanding what injectable therapeutics can achieve. However, post-injection events that influence PK outcomes remain poorly understood. Until addressed, advances in IM drug development will not realize their full potential.

Microinstrumentation for Brain Organoids

Brain organoids are three-dimensional aggregates of self-organized differentiated stem cells that mimic the structure and function of human brain regions. Organoids bridge the gaps between conventional drug screening models such as planar mammalian cell culture, animal studies, and clinical trials. They can revolutionize the fields of developmental biology, neuroscience, toxicology, and computer engineering. Conventional microinstrumentation for conventional cellular engineering, such as planar microfluidic chips; microelectrode arrays (MEAs); and optical, magnetic, and acoustic techniques, has limitations when applied to three-dimensional (3D) organoids, primarily due to their limits with inherently two-dimensional geometry and interfacing. Hence, there is an urgent need to develop new instrumentation compatible with live cell culture techniques and with scalable 3D formats relevant to organoids. This review discusses conventional planar approaches and emerging 3D microinstrumentation necessary for advanced organoid-machine interfaces. Specifically, this article surveys recently developed microinstrumentation, including 3D printed and curved microfluidics, 3D and fast-scan optical techniques, buckling and self-folding MEAs, 3D interfaces for electrochemical measurements, and 3D spatially controllable magnetic and acoustic technologies relevant to two-way information transfer with brain organoids. This article highlights key challenges that must be addressed for robust organoid culture and reliable 3D spatiotemporal information transfer.

3D Cell Culture Method in Channel-Free Water-in-Oil Droplets

A new channel-free water-in-oil (WO) droplet 3D cell culture method is proposed to address the challenges while maintaining the advantages of the conventional 3D cell culture methods. The proposed WO method can fundamentally solve the constraint of spheroids size, a common challenge in conventional 3D culture, by using droplet size controllability. The 3D cell culture performance of the WO method is verified by comparing it with the conventional 3D cell culture methods. A systematic investigation of the culture conditions of the WO method confirms the working range of cell concentration and droplet size, as well as the scalability of spheroid size. Adjusting droplet size and cell concentration enables rapid spheroid formation with large and high cell concentration droplets or fast spheroid growth with small and low cell concentration droplets, providing control over the spheroid size and growth rate according to the purpose. Furthermore, long-term culture is demonstrated for 1 month with the proposed method, showing the largest spheroid culture and demonstrating the possibility that this method can be used not only for spheroid formation but also for organoid studies. Finally, if a WO-based automated 3D cell culture system is developed, it will be a useful tool for organoid research.

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.

Uniform sized cancer spheroids production using hydrogel-based droplet microfluidics: a review

Three-dimensional (3D) cell culture models have been extensively utilized in various mechanistic studies as well as for drug development studies as superior in vitro platforms than conventional two-dimensional (2D) cell culture models. This is especially the case in cancer biology, where 3D cancer models, such as spheroids or organoids, have been utilized extensively to understand the mechanisms of cancer development. Recently, many sophisticated 3D models such as organ-on-a-chip models are emerging as advanced in vitro models that can more accurately mimic the in vivo tissue functions. Despite such advancements, spheroids are still considered as a powerful 3D cancer model due to the relatively simple structure and compatibility with existing laboratory instruments, and also can provide orders of magnitude higher throughput than complex in vitro models, an extremely important aspects for drug development. However, creating well-defined spheroids remain challenging, both in terms of throughputs in generation as well as reproducibility in size and shape that can make it challenging for drug testing applications. In the past decades, droplet microfluidics utilizing hydrogels have been highlighted due to their potentials. Importantly, core-shell structured gel droplets can avoid spheroid-to-spheroid adhesion that can cause large variations in assays while also enabling long-term cultivation of spheroids with higher uniformity by protecting the core organoid area from external environment while the outer porous gel layer still allows nutrient exchange. Hence, core-shell gel droplet-based spheroid formation can improve the predictivity and reproducibility of drug screening assays. This review paper will focus on droplet microfluidics-based technologies for cancer spheroid production using various gel materials and structures. In addition, we will discuss emerging technologies that have the potential to advance the production of spheroids, prospects of such technologies, and remaining challenges.

Drug testing of monodisperse arrays of live microdissected tumors using a valved multiwell microfluidic platform

Cancer drug testing in animals is an extremely poor predictor of the drug's safety and efficacy observed in humans. Hence there is a pressing need for functional testing platforms that better predict traditional and immunotherapy responses in human, live tumor tissue or tissue constructs, and at the same time are compatible with the use of mouse tumor tissue to facilitate building more accurate disease models. Since many cancer drug actions rely on mechanisms that depend on the tumor microenvironment (TME), such platforms should also retain as much of the native TME as possible. Additionally, platforms based on miniaturization technologies are desirable to reduce animal use and sensitivity to human tissue scarcity. Present high-throughput testing platforms that have some of these features, e.g. based on patient-derived tumor organoids, require a growth step that alters the TME. On the other hand, microdissected tumors (μDTs) or "spheroids" that retain an intact TME have shown promising responses to immunomodulators acting on native immune cells. However, difficult tissue handling after microdissection has reduced the throughput of drug testing on μDTs, thereby constraining the inherent advantages of producing numerous TME-preserving units of tissue for drug testing. Here we demonstrate a microfluidic 96-well platform designed for drug treatment of hundreds of similarly-sized, cuboidal μDTs ("cuboids") produced from a single tumor sample. The platform organizes a monodisperse array of four cuboids per well in 384 hydrodynamic traps. The microfluidic device, entirely fabricated in thermoplastics, features 96 microvalves that fluidically isolate each well after the cuboid loading step for straightforward multi-drug testing. Since our platform makes the most of scarce tumor tissue, it can potentially be applied to human biopsies that preserve the human TME while minimizing animal testing.

Reproducible generation of human liver organoids (HLOs) on a pillar plate platform via microarray 3D bioprinting

Human liver organoids (HLOs) hold significant potential for recapitulating the architecture and function of liver tissues in vivo. However, conventional culture methods of HLOs, forming Matrigel domes in 6-/24-well plates, have technical limitations such as high cost and low throughput in organoid-based assays for predictive assessment of compounds in clinical and pharmacological lab settings. To address these issues, we have developed a unique microarray 3D bioprinting protocol of progenitor cells in biomimetic hydrogels on a pillar plate with sidewalls and slits, coupled with a clear bottom, 384-deep well plate for scale-up production of HLOs. Microarray 3D bioprinting, a droplet-based printing technology, was used to generate a large number of small organoids on the pillar plate for predictive hepatotoxicity assays. Foregut cells, differentiated from human iPSCs, were mixed with Matrigel and then printed on the pillar plate rapidly and uniformly, resulting in coefficient of variation (CV) values in the range of 15-18%, without any detrimental effect on cell viability. Despite utilizing 10-50-fold smaller cell culture volume compared to their counterparts in Matrigel domes in 6-/24-well plates, HLOs differentiated on the pillar plate exhibited similar morphology and superior function, potentially due to rapid diffusion of nutrients and oxygen at the small scale. Day 25 HLOs were robust and functional on the pillar plate in terms of their viability, albumin secretion, CYP3A4 activity, and drug toxicity testing, all with low CV values. From three independent trials of in situ assessment, the IC50 values calculated for sorafenib and tamoxifen were 6.2 ± 1.6 μM and 25.4 ± 8.3 μM, respectively. Therefore, our unique 3D bioprinting and miniature organoid culture on the pillar plate could be used for scale-up, reproducible generation of HLOs with minimal manual intervention for high-throughput assessment of compound hepatotoxicity.

Self-Assembly of Tooth Root Organoid from Postnatal Human Dental Stem Cells

Challenges remain in simultaneously regenerating the multiple diverse tissues of the tooth root in a spatially organized manner. Previously, our research group has established that scaffold-free tissue engineering approaches enable dental pulp stem/progenitor cells (DPSCs) and periodontal ligament (PDL) stem/progenitor cells (PDLSCs) to self-assemble into dentin-pulp and PDL-cementum organoids, respectively. In this study, we leveraged the innate self-organizing capacity of DPSCs and PDLSCs to now engineer organoids that resemble the full tooth root. Scaffold-free engineered tissues were generated using a heterogeneous mixture of human DPSCs and PDLSCs. Within 2 days of construct formation, PDLSCs and DPSCs became spatially restricted to the periphery and center of the constructs, respectively, emulating their anatomical positions in the tooth root. Histological and microcomputed tomography analyses showed that organoids exhibited a striated mineral pattern with a central unmineralized core, surrounded by a mineralized tissue structure, enclosed within a second peripheral unmineralized tissue, similar to the natural tooth root. Interestingly, DPSCs gave rise to the central unmineralized tissue and the inner portion of the mineralized tissue, and PDLSCs generated the outer portion of the mineralized tissue and the peripheral soft tissue. Quantitative image analysis of immunofluorescent staining revealed increased dentin sialophosphoprotein expression in the region of mineralized tissue associated with DPSCs and increased cementum protein-1 expression in the portion formed by PDLSCs, demonstrating that tooth root organoids comprise two biochemically distinct mineralized tissues characteristic of dentin-like and cementum-like structures, respectively. In addition, PDL-associated protein-1 expression was localized to the peripheral soft tissue, suggesting the formation of a rudimentary PDL-like structure. This study demonstrates that DPSCs and PDLSCs have an inherent ability to orchestrate the formation of a full tooth root-like structure. These organoids present a biomimetic model system to study cellular dynamics driving dental tissue repair or could be utilized therapeutically as biological dental implants.

Effect of estradiol after bacterial infection on the Wnt/β-catenin pathway in bovine endometrium epithelial cells and organoids

Endometritis is a disease caused by a postpartum bacterial infection with a poor prognosis that primarily affects dairy cows. Three-dimensional organoids have been used as a model for endometritis, because they exhibit a structure comparable to that of the endometrium, demonstrating both expansibility and hormone responsiveness. These characteristics render them an ideal platform for in vitro investigations of endometrial diseases. Estradiol (E2) is an endogenous steroid hormone with demonstrated anti-inflammatory properties, and the objective of this study was to determine the mechanism by which E2 modulates the inflammatory response and the Wnt signal transduction pathway in bovine endometrial epithelial cells and organoids following E. coli infection. We present the techniques for isolating and culturing primary bovine endometrial epithelial cells (BEECs), and producing endometrial organoids. For the experiments, the endometrial epithelial cells and organoids were infected with E. coli for 1 h, followed by incubation with E2 for 12 h. The mRNA and protein expressions of the inflammation-related genes, IL-1β, IL-6, TLR4, and NF-κB, as well as the Wnt pathway-related genes, Wnt4, β-catenin, c-Myc, and CyclinD1, were assessed using real-time quantitative-PCR and western blotting, respectively. The CCK8 viable cell counting assay was utilized to determine the optimal concentration of the Wnt inhibitor, IWR-1. The mRNA and protein expression of Wnt pathway-related genes was assessed following IWR-1 treatment, while the expression levels of proliferation-associated genes (Ki67, PCNA) and barrier repair genes (occludin, claudin, and Zo-1) in BEECs and organoids were evaluated after E2 treatment. The results of this study show that mRNA expression of the inflammatory genes, IL-1β, TLR4, and NF-κB (P < 0.05) decreased in BEECs following E2 treatment compared to the E. coli group. The protein expression of the IL-1β, IL-6, TLR4 and NF-κB genes was also inhibited (P < 0.05). Similar results were observed in tests on the organoids. Our findings demonstrate that E2 significantly upregulates the expression of Wnt-related genes, including β-catenin and c-Myc, while concurrently downregulating the expression of GSK3β (P < 0.05). Next, we treated E. coli-infected BEECs and organoids with the Wnt inhibitor, IWR-1. Compared with E. coli and E. coli + E2, the expression of mRNA and protein from Wnt 4, β-catenin, and CyclinD1 in E. coli + E2 and E. coli + IWR-1 was down-regulated (P < 0.05). The expression of the proliferation genes, Ki67, PCNA, and the tight junction genes, occludin, claudin1, and Zo-1, in organoids was significantly higher than that in BEECs (P < 0.05). In summary, we found strong potential for E2 mitigation of the E. coli-induced inflammatory response in BEECs and organoids, through activation of the Wnt pathway. In addition, the proliferation and repair capacity of organoids was much higher than that of BEECs.

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.

Strategies for Constructing Tissue-Engineered Fat for Soft Tissue Regeneration

BACKGROUND

Repairing soft tissue defects caused by inflammation, tumors, and trauma remains a major challenge for surgeons. Adipose tissue engineering (ATE) provides a promising way to solve this problem.

METHODS

This review summarizes the current ATE strategies for soft tissue reconstruction, and introduces potential construction methods for ATE.

RESULTS

Scaffold-based and scaffold-free strategies are the two main approaches in ATE. Although several of these methods have been effective clinically, both scaffold-based and scaffold-free strategies have limitations. The third strategy is a synergistic tissue engineering strategy and combines the advantages of scaffold-based and scaffold-free strategies.

CONCLUSION

Personalized construction, stable survival of reconstructed tissues and functional recovery of organs are future goals of building tissue-engineered fat for ATE.

Acoustofluidic Actuation of Living Cells

Acoutofluidics is an increasingly developing and maturing technical discipline. With the advantages of being label-free, non-contact, bio-friendly, high-resolution, and remote-controllable, it is very suitable for the operation of living cells. After decades of fundamental laboratory research, its technical principles have become increasingly clear, and its manufacturing technology has gradually become popularized. Presently, various imaginative applications continue to emerge and are constantly being improved. Here, we introduce the development of acoustofluidic actuation technology from the perspective of related manipulation applications on living cells. Among them, we focus on the main development directions such as acoustofluidic sorting, acoustofluidic tissue engineering, acoustofluidic microscopy, and acoustofluidic biophysical therapy. This review aims to provide a concise summary of the current state of research and bridge past developments with future directions, offering researchers a comprehensive overview and sparking innovation in the field.

Promising preclinical models for lung cancer research-lung cancer organoids: a narrative review

Background and Objective

Traditional cell line models are the commonly used preclinical models for lung cancer research. However, cell lines cannot recapitulate the complex tumor heterogeneity and cannot mimic the microenvironment of human cancer. Recently, 3D multicellular in vitro self-assembled models called "organoids" have been developed at a fast pace in the field of research, which can mimic the actual primary tumor. At present, several studies have reported on protocols of lung cancer organoids (LCOs) generation, and using LCOs can provide novel insight into the basic and translational research of lung cancer. However, the establishment of the LCO models remains challenging due to the complexity of lung cancer and the immaturity of organoid technology, so it is necessary to understand the influences of different methodologies on LCO generation and review the applications and limitations of LCO models.

Methods

In this review, we searched the literature in the recent ten years in the field of LCOs.

Key Content and Findings

We summarized the methodology, the problems, and the solutions in the LCOs generation, its application and limitations, as well as proposing future challenges and perspectives.

Conclusions

Currently, LCOs are successfully generated via exploring the methodology by the researchers. Though there are still challenges in clinical application, LCOs are applied in some cancer studies including investigation of anti-cancer treatment response in vitro, modeling tumor immune microenvironment, and construction of organ chips, which are forging a promising path towards precision medicine.

Optimization of hair follicle spheroids for hair-on-a-chip

Currently, most models for hair follicle research have the limitation of not replicating some key features of the hair follicle microenvironment. To complement this, we transfected various factors for hair growth into dermal papilla cells (DPCs) by electroporation and cultured the spheroids with keratinocytes (KCs). We optimized the cell number and culture period for applying spheroids to hair-on-a-chip. Furthermore, we investigated the expression of hair growth factors in spheroids depending on the presence or absence of human umbilical vein endothelial cells (HUVECs) and transfection. In spheroids in which DPCs, KCs, and HUVECs were co-cultured for 21 days, the expression of lymphoid enhancer factor 1 (LEF1), T-cell factor 1 (TCF1), and keratin 25 (K25) in the center of the spheroid, the expression of keratin 17 (K17) on the outer surface of the spheroid, and the shape of hair extending outward from the spheroid surface were observed. From these results, it is expected that a hair-on-a-chip experiment in which short-term cultured TKH spheroids are injected into the dermis and co-cultured with KC will enable the production of full-thickness skin equivalents containing hair in vitro without transplantation into animals.

Sophocarpine alleviates intestinal fibrosis via inhibition of inflammation and fibroblast into myofibroblast transition by targeting the Sirt1/p65 signaling axis

In this study, we used alkaloids from Sophora flavescens to inhibit the SASP, leading to fibroblast-into-myofibroblast transition (FMT) to maintain intestinal mucosal homeostasis in vitro and in vivo. We used western blotting (WB) and immunofluorescence staining (IF) to assess whether five kinds of alkaloids inhibit the major inflammatory pathways and chose the most effective compound (sophocarpine; SPC) to ameliorate colorectal inflammation in a dextran sulfate sodium (DSS)-induced UC mouse model. IF, Immunohistochemistry staining (IHC), WB, disease activity index (DAI), and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the mechanism of action of this compound. Next, we detected the pharmacological activity of SPC on the senescence-associated secretory phenotypes (SASP) and FMT in interleukin 6 (IL-6)-induced senescence-like fibroblasts and discussed the mucosal protection ability of SPC on a fibroblast-epithelium/organoid coculture system and organ-on-chip system. Taken together, our results provide evidence that SPC alleviates the inflammatory response, improves intestinal fibrosis and maintains intestinal mucosal homeostasis in vivo. Meanwhile, SPC was able to prevent IL-6-induced SASP and FMT in fibroblasts, maintain the expression of TJ proteins, and inhibit inflammation and genomic stability of colonic mucosal epithelial cells by activating SIRT1 in vitro. In conclusion, SPC treatment attenuates intestinal fibrosis by regulating SIRT1/NF-κB p65 signaling, and it might be a promising therapeutic agent for inflammatory bowel disease.

Reproducible generation of human liver organoids (HLOs) on a pillar plate platform via microarray 3D bioprinting

Human liver organoids (HLOs) hold significant potential for recapitulating the architecture and function of liver tissues in vivo. However, conventional culture methods of HLOs, forming Matrigel domes in 6-/24-well plates, have technical limitations such as high cost and low throughput in organoid-based assays for predictive assessment of compounds in clinical and pharmacological lab settings. To address these issues, we have developed a unique microarray 3D bioprinting protocol of progenitor cells in biomimetic hydrogels on a pillar plate with sidewalls and slits, coupled with a clear bottom, 384-deep well plate for scale-up production of HLOs. Microarray 3D bioprinting, a droplet-based printing technology, was used to generate a large number of small organoids on the pillar plate for predictive hepatotoxicity assays. Foregut cells, differentiated from human iPSCs, were mixed with Matrigel and then printed on the pillar plate rapidly and uniformly, resulting in coefficient of variation (CV) values in the range of 15 - 18%, without any detrimental effect on cell viability. Despite utilizing 10 - 50-fold smaller cell culture volume compared to their counterparts in Matrigel domes in 6-/24-well plates, HLOs differentiated on the pillar plate exhibited similar morphology and superior function, potentially due to rapid diffusion of nutrients and oxygen at the small scale. Day 25 HLOs were robust and functional on the pillar plate in terms of their viability, albumin secretion, CYP3A4 activity, and drug toxicity testing, all with low CV values. From three independent trials of in situ assessment, the IC50 values calculated for sorafenib and tamoxifen were 6.2 ± 1.6 μM and 25.4 ± 8.3 μM, respectively. Therefore, our unique 3D bioprinting and miniature organoid culture on the pillar plate could be used for scale-up, reproducible generation of HLOs with minimal manual intervention for high-throughput assessment of compound hepatotoxicity.

Artificial tumor matrices and bioengineered tools for tumoroid generation

The tumor microenvironment (TME) is critical for tumor growth and metastasis. The TME contains cancer-associated cells, tumor matrix, and tumor secretory factors. The fabrication of artificial tumors, so-called tumoroids, is of great significance for the understanding of tumorigenesis and clinical cancer therapy. The assembly of multiple tumor cells and matrix components through interdisciplinary techniques is necessary for the preparation of various tumoroids. This article discusses current methods for constructing tumoroids (tumor tissue slices and tumor cell co-culture) for pre-clinical use. This article focuses on the artificial matrix materials (natural and synthetic materials) and biofabrication techniques (cell assembly, bioengineered tools, bioprinting, and microfluidic devices) used in tumoroids. This article also points out the shortcomings of current tumoroids and potential solutions. This article aims to promotes the next-generation tumoroids and the potential of them in basic research and clinical application.

Organoid intelligence: Integration of organoid technology and artificial intelligence in the new era of in vitro models

Organoid Intelligence ushers in a new era by seamlessly integrating cutting-edge organoid technology with the power of artificial intelligence. Organoids, three-dimensional miniature organ-like structures cultivated from stem cells, offer an unparalleled opportunity to simulate complex human organ systems in vitro. Through the convergence of organoid technology and AI, researchers gain the means to accelerate discoveries and insights across various disciplines. Artificial intelligence algorithms enable the comprehensive analysis of intricate organoid behaviors, intricate cellular interactions, and dynamic responses to stimuli. This synergy empowers the development of predictive models, precise disease simulations, and personalized medicine approaches, revolutionizing our understanding of human development, disease mechanisms, and therapeutic interventions. Organoid Intelligence holds the promise of reshaping how we perceive in vitro modeling, propelling us toward a future where these advanced systems play a pivotal role in biomedical research and drug development.

Spheroids formation in large drops suspended in superhydrophobic paper cones

The utilization of 3D cell culture for spheroid formation holds significant implications in cancer research, contributing to a fundamental understanding of the disease and aiding drug development. Conventional methods such as the hanging drop technique and other alternatives encounter limitations due to smaller drop volumes, leading to nutrient starvation and restricted culture duration. In this study, we present a straightforward approach to creating superhydrophobic paper cones capable of accommodating large volumes of culture media drops. These paper cones have sterility, autoclavability, and bacterial repellent properties. Leveraging these attributes, we successfully generate large spheroids of ovarian cancer cells and, as a proof of concept, conduct drug screening to assess the impact of carboplatin. Thus, our method enables the preparation of flexible superhydrophobic surfaces for laboratory applications in an expeditious manner, exemplified here through spheroid formation and drug screening demonstrations.

Principles of Hanging Drop Method (Spheroid Formation) in Cell Culture

A type of three-dimensional (3D) cell culture models which is simple and easy is hanging drop method. The hanging drop method emerges as a pivotal technique with diverse applications in cancer research and cell biology. This method facilitates the formation of multicellular spheroids, providing a unique environment for studying cell behavior dynamics. The hanging drop method's theoretical underpinning relies on gravity-enforced self-assembly, allowing for cost-effective, reproducible 3D cell cultures with controlled spheroid sizes. The advantages of this approach include its efficiency in producing cellular heterogeneity, particularly in non-adherent 3D cultures, and its ability to create hypoxic spheroids, making it a suitable model for studying cancer. Moreover, the hanging drop method has proven valuable in investigating various aspects such as tissue structure, signaling pathways, immune activation of cancer cells, and notably, cell proliferation. Researchers have utilized the hanging drop method to explore the dynamics of cell proliferation, studying the effects of mesenchymal stem cells (MSC) secretome on cancer cells. The method's application involves co-culturing different cell lines, assessing spheroid formations, and quantifying their sizes over time. These studies have unveiled intricate cell behavior dynamics, demonstrating how the MSC secretome influences cancer cell growth and viability within a three-dimensional co-culture paradigm.

Progress in developing microphysiological systems for biological product assessment

Microphysiological systems (MPS), also known as miniaturized physiological environments, have been engineered to create and study functional tissue units capable of replicating organ-level responses in specific contexts. The MPS has the potential to provide insights about the safety, characterization, and effectiveness of medical products that are different and complementary to insights gained from traditional testing systems, which can help facilitate the transition of potential medical products from preclinical phases to clinical trials, and eventually to market. While many MPS are versatile and can be used in various applications, most of the current applications have primarily focused on drug discovery and testing. Yet, there is a limited amount of research available that demonstrates the use of MPS in assessing biological products such as cellular and gene therapies. This review paper aims to address this gap by discussing recent technical advancements in MPS and their potential for assessing biological products. We further discuss the challenges and considerations involved in successful translation of MPS into mainstream product testing.

Opto-fluidically multiplexed assembly and micro-robotics

Techniques for high-definition micromanipulations, such as optical tweezers, hold substantial interest across a wide range of disciplines. However, their applicability remains constrained by material properties and laser exposure. And while microfluidic manipulations have been suggested as an alternative, their inherent capabilities are limited and further hindered by practical challenges of implementation and control. Here we show that the iterative application of laser-induced, localized flow fields can be used for the relative positioning of multiple micro-particles, irrespectively of their material properties. Compared to the standing theoretical proposal, our method keeps particles mobile, and we show that their precision manipulation is non-linearly accelerated via the multiplexing of temperature stimuli below the heat diffusion limit. The resulting flow fields are topologically rich and mathematically predictable. They represent unprecedented microfluidic control capabilities that are illustrated by the actuation of humanoid micro-robots with up to 30 degrees of freedom, whose motions are sufficiently well-defined to reliably communicate personal characteristics such as gender, happiness and nervousness. Our results constitute high-definition micro-fluidic manipulations with transformative potential for assembly, micro-manufacturing, the life sciences, robotics and opto-hydraulically actuated micro-factories.

Brain organoids: A revolutionary tool for modeling neurological disorders and development of therapeutics

Brain organoids are self-organized, three-dimensional (3D) aggregates derived from pluripotent stem cells that have cell types and cellular architectures resembling those of the developing human brain. The current understanding of human brain developmental processes and neurological disorders has advanced significantly with the introduction of this in vitro model. Brain organoids serve as a translational link between two-dimensional (2D) cultures and in vivo models which imitate the neural tube formation at the early and late stages and the differentiation of neuroepithelium with whole-brain regionalization. In addition, the generation of region-specific brain organoids made it possible to investigate the pathogenic and etiological aspects of acquired and inherited brain disease along with drug discovery and drug toxicity testing. In this review article, we first summarize an overview of the existing methods and platforms used for generating brain organoids and their limitations and then discuss the recent advancement in brain organoid technology. In addition, we discuss how brain organoids have been used to model aspects of neurodevelopmental and neurodegenerative diseases, including autism spectrum disorder (ASD), Rett syndrome, Zika virus-related microcephaly, Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD).

Insights on Three Dimensional Organoid Studies for Stem Cell Therapy in Regenerative Medicine

Regenerative medicine has developed as a promising discipline that utilizes stem cells to address limitations in traditional therapies, using innovative techniques to restore and repair damaged organs and tissues. One such technique is the generation of three-dimensional (3D) organoids in stem cell therapy. Organoids are 3D constructs that resemble specific organs' structural and functional characteristics and are generated from stem cells or tissue-specific progenitor cells. The use of 3D organoids is advantageous in comparison to traditional two-dimensional (2D) cell culture by bridging the gap between in vivo and in vitro research. This review aims to provide an overview of the advancements made towards regenerative medicine using stem cells to generate organoids, explore the techniques used in generating 3D organoids and their applications and finally elucidate the challenges and future directions in regenerative medicine using 3D organoids.

Bovine adipose tissue-derived mesenchymal stem cells self-assemble with testicular cells and integrates and modifies the structure of a testicular organoids

Mesenchymal stem cells (MSC) display self-renewal and mesodermal differentiation potentials. These characteristics make them potentially useful for in vitro derivation of gametes, which may constitute experimental therapies for human and animal reproduction. Organoids provide a spatial support and may simulate a cellular niche for in vitro studies. In this study, we aimed at evaluating the potential integration of fetal bovine MSCs derived from adipose tissue (AT-MSCs) in testicular organoids (TOs), their spatial distribution with testicular cells during TO formation and their potential for germ cell differentiation. TOs were developed using Leydig, Sertoli, and peritubular myoid cells that were previously isolated from bovine testes (n = 6). Thereafter, TOs were characterized using immunofluorescence and Q-PCR to detect testicular cell-specific markers. AT-MSCs were labeled with PKH26 and then cultured with testicular cells at a concentration of 1 × 106 cells per well in Ultra Low Attachment U-shape bottom (ULA) plates. TOs formed by testicular cells and AT-MSCs (TOs + AT-MSCs) maintained a rounded structure throughout the 28-day culture period and did not show significant differences in their diameters. Conversely, control TOs exhibited a compact structure until day 7 of culture, while on day 28 they displayed cellular extensions around their structure. Control TOs had greater (P < 0.05) diameters compared to TOs + AT-MSCs. AT-MSCs induced an increase in proportion of Leydig and peritubular myoid cells in TOs + AT-MSCs; however, did not induce changes in the overall gene expression of testicular cell-specific markers. STAR immunolabelling detected Leydig cells that migrated from the central area to the periphery and formed brunches in control TOs. However, in TOs + AT-MSCs, Leydig cells formed a compact peripheral layer. Sertoli cells immunodetected using WT1 marker were observed within the central area forming clusters of cells in TOs + AT-MSCs. The expression of COL1A associated to peritubular myoids cells was restricted to the central region in TOs + AT-MSCs. Thus, during a 28-day culture period, fetal bovine AT-MSCs integrated and modified the structure of the TOs, by restricting formation of branches, limiting the overall increase in diameters and increasing the proportions of Leydig and peritubular myoid cells. AT-MSCs also induced a reorganization of testicular cells, changing their distribution and particularly the location of Leydig cells.

The evolution of in vitro models of lung fibrosis: promising prospects for drug discovery

Lung fibrosis is a complex process, with unknown underlying mechanisms, involving various triggers, diseases and stimuli. Different cell types (epithelial cells, endothelial cells, fibroblasts and macrophages) interact dynamically through multiple signalling pathways, including biochemical/molecular and mechanical signals, such as stiffness, affecting cell function and differentiation. Idiopathic pulmonary fibrosis (IPF) is the most common fibrosing interstitial lung disease (fILD), characterised by a notably high mortality. Unfortunately, effective treatments for advanced fILD, and especially IPF and non-IPF progressive fibrosing phenotype ILD, are still lacking. The development of pharmacological therapies faces challenges due to limited knowledge of fibrosis pathogenesis and the absence of pre-clinical models accurately representing the complex features of the disease. To address these challenges, new model systems have been developed to enhance the translatability of preclinical drug testing and bridge the gap to human clinical trials. The use of two- and three-dimensional in vitro cultures derived from healthy or diseased individuals allows for a better understanding of the underlying mechanisms responsible for lung fibrosis. Additionally, microfluidics systems, which replicate the respiratory system's physiology ex vivo, offer promising opportunities for the development of effective therapies, especially for IPF.

Recreating Human Skin In Vitro: Should the Microbiota Be Taken into Account?

Skin plays crucial roles in the human body: besides protecting the organism from external threats, it acts as a thermal regulator, is responsible for the sense of touch, hosts microbial communities (the skin microbiota) involved in preventing the invasion of foreign pathogens, contains immunocompetent cells that maintain a healthy immunogenic/tolerogenic balance, and is a suitable route for drug administration. In the skin, four defense levels can be identified: besides the physical, chemical, and immune barriers that are inherent to the tissue, the skin microbiota (i.e., the numerous microorganisms living on the skin surface) provides an additional barrier. Studying the skin barrier function or the effects of drugs or cosmetic agents on human skin is a difficult task since snapshot evidence can only be obtained using bioptic samples where dynamic processes cannot properly be followed. To overcome these limitations, many different in vitro models of human skin have been developed that are characterized by diverse levels of complexity in terms of chemical, structural, and cellular composition. The aim of this review is to summarize and discuss the advantages and disadvantages of the different human skin models so far available and to underline how the insertion of a proper microbiota would positively impact an in vitro human skin model in an attempt to better mimic conditions in vivo.

Uniform cerebral organoid culture on a pillar plate by simple and reproducible spheroid transfer from an ultralow attachment well plate

Human induced pluripotent stem cell (iPSC)-derived brain organoids have potential to recapitulate the earliest stages of brain development, serving as an effectivein vitromodel for studying both normal brain development and disorders. However, current brain organoid culture methods face several challenges, including low throughput, high variability in organoid generation, and time-consuming, multiple transfer and encapsulation of cells in hydrogels throughout the culture. These limitations hinder the widespread application of brain organoids including high-throughput assessment of compounds in clinical and industrial lab settings. In this study, we demonstrate a straightforward approach of generating multiple cerebral organoids from iPSCs on a pillar plate platform, eliminating the need for labor-intensive, multiple transfer and encapsulation steps to ensure the reproducible generation of cerebral organoids. We formed embryoid bodies in an ultra-low attachment 384-well plate and subsequently transferred them to the pillar plate containing Matrigel, using a straightforward sandwiching and inverting method. Each pillar on the pillar plate contains a single spheroid, and the success rate of spheroid transfer was in a range of 95%-100%. Using this approach, we robustly generated cerebral organoids on the pillar plate and demonstrated an intra-batch coefficient of variation below 9%-19% based on ATP-based cell viability and compound treatment. Notably, our spheroid transfer method in combination with the pillar plate allows miniaturized culture of cerebral organoids, alleviates the issue of organoid variability, and has potential to significantly enhance assay throughput by allowingin situorganoid assessment as compared to conventional organoid culture in 6-/24-well plates, petri dishes, and spinner flasks.

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.

Application of Platelet-Rich Plasma as a Stem Cell Treatment - an Attempt to Clarify a Common Public Misconception

In recent years, there has been a significant increase in the practice of regenerative medicine by health practitioners and direct-to-consumer businesses globally. Among different tools of regenerative medicine, platelet-rich plasma (PRP) and stem cell-based therapies have received considerable attention. The use of PRP, in particular, has gained popularity due to its easy access, simple processing techniques, and regenerative potential. However, it is important to address a common misconception amongst the general public equating to PRP and stem cells due to the demonstrated efficacy of PRP in treating musculoskeletal and dermatological disorders. Notably, PRP promotes regeneration by providing growth factors or other paracrine factors only. Therefore, it cannot replenish or replace the lost cells in conditions where a large number of cells are required to regenerate tissues and/or organs. In such cases, cellbased therapies are the preferred option. Additionally, other tools of regenerative medicine, such as bioprinting, organoids, and mechanobiology also rely on stem cells for their success. Hence, healthcare and commercial entities offering direct-to-customer regenerative therapies should not mislead the public by claiming that the application of PRP is a stem cell-based therapy. Furthermore, it is important for regulatory bodies to strictly monitor these profit-driven entities to prevent them from providing unregulated regenerative treatments and services that claim a broad variety of benefits with little proof of efficacy, safety concerns, and obscure scientific justification.

Next-Generation Preclinical Functional Testing Models in Cancer Precision Medicine: CTC-Derived Organoids

Basic and clinical cancer research requires tumor models that consistently recapitulate the characteristics of prima tumors. As ex vivo 3D cultures of patient tumor cells, patient-derived tumor organoids possess the biological properties of primary tumors and are therefore excellent preclinical models for cancer research. Patient-derived organoids can be established using primary tumor tissues, peripheral blood, pleural fluid, ascites, and other samples containing tumor cells. Circulating tumor cells acquired by non-invasive sampling feature dynamic circulation and high heterogeneity. Circulating tumor cell-derived organoids are prospective tools for the dynamic monitoring of tumor mutation evolution profiles because they reflect the heterogeneity of the original tumors to a certain extent. This review discusses the advantages and applications of patient-derived organoids. Meanwhile, this work highlights the biological functions of circulating tumor cells, the latest advancement in research of circulating tumor cell-derived organoids, and potential application and challenges of this technology.

Stretchable Sponge-Based Electrochemical Biosensor for Real-Time Sensing of Cells in Three-Dimensional Culture

For the study of cell biology, real-time information on cell physiological processes will be more accurate and closer to the in vivo condition in a three-dimensional (3D) culture system. Although most reported 3D cell culture scaffolds can better mimic the in vivo dynamic microenvironment, the real-time analysis technique is deficient or lacking. Herein, a stretchable and conductive 3D scaffold is developed to construct an electrochemical biosensor for real-time monitoring of cell release in 3D culture under stimulation of drug stimulant and mechanical force. In our design, the polyurethane sponge (PU) dipped with conductive carbon ink (CC/PU) was used as a conductive scaffold, and gold nanoparticles (nano-Au) were electrodeposited on the CC/PU (nano-Au CC/PU) to improve the electrochemical sensing performance. The prepared nano-Au CC/PU scaffold exhibits a good electrocatalytic ability to H2O2 with a linear range from 20 nM to 43 μM. Due to the great biocompatibility, HeLa cells can be cultured directly on the nano-Au CC/PU and the in situ and real-time tracking of H2O2 secretion from cells was achieved. The results demonstrate that both the drug stimulant and mechanical force can rapidly activate the release of reactive oxygen species. This study indicates that the stretchable 3D sensing scaffold has good potential for cell biology research in an in vivo-like microenvironment and can be extensively used in the fields of tissue engineering, drug screening, and pathological 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.

Mass production of lumenogenic human embryoid bodies and functional cardiospheres using in-air-generated microcapsules

Organoids are engineered 3D miniature tissues that are defined by their organ-like structures, which drive a fundamental understanding of human development. However, current organoid generation methods are associated with low production throughputs and poor control over size and function including due to organoid merging, which limits their clinical and industrial translation. Here, we present a microfluidic platform for the mass production of lumenogenic embryoid bodies and functional cardiospheres. Specifically, we apply triple-jet in-air microfluidics for the ultra-high-throughput generation of hollow, thin-shelled, hydrogel microcapsules that can act as spheroid-forming bioreactors in a cytocompatible, oil-free, surfactant-free, and size-controlled manner. Uniquely, we show that microcapsules generated by in-air microfluidics provide a lumenogenic microenvironment with near 100% efficient cavitation of spheroids. We demonstrate that upon chemical stimulation, human pluripotent stem cell-derived spheroids undergo cardiomyogenic differentiation, effectively resulting in the mass production of homogeneous and functional cardiospheres that are responsive to external electrical stimulation. These findings drive clinical and industrial adaption of stem cell technology in tissue engineering and drug testing.

Uniform cerebral organoid culture on a pillar plate by simple and reproducible spheroid transfer from an ultralow attachment well plate

Human induced pluripotent stem cell (iPSCs)-derived brain organoids have potential to recapitulate the earliest stages of brain development, serving as an effective in vitro model for studying both normal brain development and disorders. However, current brain organoid culture methods face several challenges, including low throughput, high variability in organoid generation, and time-consuming, multiple transfer and encapsulation of cells in hydrogels throughout the culture. These limitations hinder the widespread application of brain organoids including high-throughput assessment of compounds in clinical and industrial lab settings. In this study, we demonstrate a straightforward approach of generating multiple cerebral organoids from iPSCs on a pillar plate platform, eliminating the need for labor-intensive, multiple transfer and encapsulation steps to ensure the reproducible generation of cerebral organoids. We formed embryoid bodies (EBs) in an ultra-low attachment (ULA) 384-well plate and subsequently transferred them to the pillar plate containing Matrigel, using a straightforward sandwiching and inverting method. Each pillar on the pillar plate contains a single spheroid, and the success rate of spheroid transfer was in a range of 95 - 100%. By differentiating the EBs on the pillar plate, we achieved robust generation of cerebral organoids with a coefficient of variation (CV) below 19%. Notably, our spheroid transfer method in combination with the pillar plate allows miniaturized culture of cerebral organoids, alleviates the issue of organoid variability, and has potential to significantly enhance assay throughput by allowing in situ organoid assessment as compared to conventional organoid culture in 6-/24-well plates, petri dishes, and spinner flasks.

Theoretical Neurobiology of Consciousness Applied to Human Cerebral Organoids

Organoids and specifically human cerebral organoids (HCOs) are one of the most relevant novelties in the field of biomedical research. Grown either from embryonic or induced pluripotent stem cells, HCOs can be used as in vitro three-dimensional models, mimicking the developmental process and organization of the developing human brain. Based on that, and despite their current limitations, it cannot be assumed that they will never at any stage of development manifest some rudimentary form of consciousness. In the absence of behavioral indicators of consciousness, the theoretical neurobiology of consciousness being applied to unresponsive brain-injured patients can be considered with respect to HCOs. In clinical neurology, it is difficult to discern a capacity for consciousness in unresponsive brain-injured patients who provide no behavioral indicators of consciousness. In such scenarios, a validated neurobiological theory of consciousness, which tells us what the neural mechanisms of consciousness are, could be used to identify a capacity for consciousness. Like the unresponsive patients that provide a diagnostic difficulty for neurologists, HCOs provide no behavioral indicators of consciousness. Therefore, this article discusses how three prominent neurobiological theories of consciousness apply to human cerebral organoids. From the perspective of the Temporal Circuit Hypothesis, the Global Neuronal Workspace Theory, and the Integrated Information Theory, we discuss what neuronal structures and functions might indicate that cerebral organoids have a neurobiological capacity to be conscious.

Cancer Models on Chip: Paving the Way to Large-Scale Trial Applications

Cancer kills millions of individuals every year all over the world (Global Cancer Observatory). The physiological and biomechanical processes underlying the tumor are still poorly understood, hindering researchers from creating new, effective therapies. Inconsistent results of preclinical research, in vivo testing, and clinical trials decrease drug approval rates. 3D tumor-on-a-chip (ToC) models integrate biomaterials, tissue engineering, fabrication of microarchitectures, and sensory and actuation systems in a single device, enabling reliable studies in fundamental oncology and pharmacology. This review includes a critical discussion about their ability to reproduce the tumor microenvironment (TME), the advantages and drawbacks of existing tumor models and architectures, major components and fabrication techniques. The focus is on current materials and micro/nanofabrication techniques used to manufacture reliable and reproducible microfluidic ToC models for large-scale trial applications.

Highly reproducible and cost-effective one-pot organoid differentiation using a novel platform based on PF-127 triggered spheroid assembly

Organoid technology offers sophisticatedin vitrohuman models for basic research and drug development. However, low batch-to-batch reproducibility and high cost due to laborious procedures and materials prevent organoid culture standardization for automation and high-throughput applications. Here, using a novel platform based on the findings that Pluronic F-127 (PF-127) could trigger highly uniform spheroid assembly through a mechanism different from plate coating, we develop a one-pot organoid differentiation strategy. Using our strategy, we successfully generate cortical, nephron, hepatic, and lung organoids with improved reproducibility compared to previous methods while reducing the original costs by 80%-95%. In addition, we adapt our platform to microfluidic chips allowing automated culture. We showcase that our platform can be applied to tissue-specific screening, such as drug toxicity and transfection reagents testing. Finally, we generateNEAT1knockout tissue-specific organoids and showNEAT1modulates multiple signaling pathways fine-tuning the differentiation of nephron and hepatic organoids and suppresses immune responses in cortical organoids. In summary, our strategy provides a powerful platform for advancing organoid research and studying human development and diseases.