An organoid is a miniaturised and simplified version of an organ produced in vitro in three dimensions that mimics the key functional, structural, and biological complexity of that organ. [1] It is derived from one or a few cells from a tissue, embryonic stem cells, or induced pluripotent stem cells, which can self-organize in three-dimensional culture owing to their self-renewal and differentiation capacities. The technique for growing organoids has rapidly improved since the early 2010s, and The Scientist named it one of the biggest scientific advancements of 2013. [2] Scientists and engineers use organoids to study development and disease in the laboratory, for drug discovery and development in industry, [3] personalized diagnostics and medicine, gene and cell therapies, tissue engineering, and regenerative medicine.
Attempts to create organs in vitro started with one of the first dissociation-reaggregation experiments [4] where Henry Van Peters Wilson demonstrated that mechanically dissociated sponge cells can reaggregate and self-organize to generate a whole organism. [5] In the subsequent decades, multiple labs were able to generate different types of organs [4] in vitro through the dissociation and reaggregation of organ tissues obtained from amphibians [6] and embryonic chicks. [7] The formation of first tissue-like colonies in vitro was observed for the first time by co-culturing keratinocytes and 3T3 fibroblasts. [8] The phenomena of mechanically dissociated cells aggregating and reorganizing to reform the tissue they were obtained from subsequently led to the development of the differential adhesion hypothesis by Malcolm Steinberg. [4] With the advent of the field of stem cell biology, the potential of stem cells to form organs in vitro was realized early on with the observation that when stem cells form teratomas or embryoid bodies, the differentiated cells can organize into different structures resembling those found in multiple tissue types. [4] The advent of the field of organoids, started with a shift from culturing and differentiating stem cells in two dimensional (2D) media, to three dimensional (3D) media to allow for the development of the complex 3-dimensional structures of organs. [4] Utilization of 3D media culture media methods for the structural organization was made possible with the development of extracellular matrices (ECM). [9] In the late 1980s, Bissell and colleagues showed that a laminin rich gel can be used as a basement membrane for differentiation and morphogenesis in cell cultures of mammary epithelial cells. [10] [11] Since 1987, researchers have devised different methods for 3D culturing, and were able to utilize different types of stem cells to generate organoids resembling a multitude of organs. [4] In the 1990s, in addition to their role in physical support, the role of ECM components in gene expression by their interaction with integrin-based focal adhesion pathways was reported. [12] In 2006, Yaakov Nahmias and David Odde showed the self-assembly of vascular liver organoid maintained for over 50 days in vitro. [13] In 2008, Yoshiki Sasai and his team at RIKEN institute demonstrated that stem cells can be coaxed into balls of neural cells that self-organize into distinctive layers. [14] In 2009 the Laboratory of Hans Clevers at Hubrecht Institute and University Medical Center Utrecht, Netherlands, showed that single LGR5-expressing intestinal stem cells self-organize to crypt-villus structures in vitro without necessity of a mesenchymal niche, making them the first organoids. [15] In 2010, Mathieu Unbekandt & Jamie A. Davies demonstrated the production of renal organoids from murine fetus-derived renogenic stem cells. [16] In 2014, Qun Wang and co-workers engineered collagen-I and laminin based gels and synthetic foam biomaterials for the culture and delivery of intestinal organoids [17] and encapsulated DNA-functionalized gold nanoparticles into intestinal organoids to form an intestinal Trojan horse for drug delivery and gene therapy. [18] Subsequent reports showed significant physiological function of these organoids in vitro [19] and in vivo . [20] [21]
Other significant early advancements included in 2013, Madeline Lancaster at the Institute of Molecular Biotechnology of the Austrian Academy of Sciences established a protocol starting from pluripotent stem cells to generate cerebral organoids that mimic the developing human brain's cellular organization. [22] Meritxell Huch and Craig Dorrell at Hubrecht Institute and University Medical Center Utrecht demonstrated that single Lgr5+ cells from damaged mouse liver can be clonally expanded as liver organoids in Rspo1-based culture medium over several months. [23] In 2014, Artem Shkumatov et al. at the University of Illinois at Urbana-Champaign demonstrated that cardiovascular organoids can be formed from ES cells through modulation of the substrate stiffness, to which they adhere. Physiological stiffness promoted three-dimensionality of EBs and cardiomyogenic differentiation. [24]
Lancaster and Knoblich [4] define an organoid as a collection of organ-specific cell types that develops from stem cells or organ progenitors, self-organizes through cell sorting and spatially restricted lineage commitment in a manner similar to in vivo, and exhibits the following properties:
Organoid formation generally requires culturing the stem cells or progenitor cells in a 3D medium. [4] Stem cells have the ability to self-renew and differentiate into various cell subtypes, and they enable understanding the processes of development and disease progression. [25] Therefore organoids derived from stem cells enable studying biology and physiology at the organ level. [26] The 3D medium can be made using an extracellular matrix hydrogel such as Matrigel or Cultrex BME, which is a laminin-rich extracellular matrix that is secreted by the Engelbreth-Holm-Swarm tumor line. [27] Organoid bodies can then be made through embedding stem cells in the 3D medium. [4] When pluripotent stem cells are used for the creation of the organoid, the cells are usually, but not all the time, allowed to form embryoid bodies. [4] Those embryoid bodies are then pharmacologically treated with patterning factors to drive the formation of the desired organoid identity. [4] Organoids have also been created using adult stem cells extracted from the target organ, and cultured in 3D media. [28]
Biochemical cues have been incorporated in 3D organoid cultures and with exposure of morphogenes, morphogen inhibitors, or growth factors, organoid models can be developed using embryonic stem cells (ESCs) or adult stem cells (ASCs). Vascularization techniques can be utilized to embody microenvironments that are close to their counterparts, physiologically. Vasculature systems that can facilitate oxygen or nutrients to the inner mass of organoids can be achieved through microfluidic systems, vascular endothelial growth factor delivery systems, and endothelial cell-coated modules. [9] With patient-derived induced pluripotent stem cells (iPSCs) [29] and CRISPR/Cas-based genome editing [30] technologies, genome-edited or mutated pluripotent stem cells (PSCs) with altered signaling cues can be generated to control intrinsic cues within organoids.
A multitude of organ structures have been recapitulated using organoids. [4] This section aims to outline the state of the field as of now through providing an abridged list of the organoids that have been successfully created, along with a brief outline based on the most recent literature for each organoid, and examples of how it has been utilized in research.
A cerebral organoid describes artificially grown, in vitro , miniature organs resembling the brain. Cerebral organoids are created by culturing human pluripotent stem cells in a three-dimensional structure using rotational bioreactor and develop over the course of months. [22] The procedure has potential applications in the study of brain development, physiology and function. Cerebral organoids may experience "simple sensations" in response to external stimulation and neuroscientists are among those expressing concern that such organs could develop sentience. They propose that further evolution of the technique needs to be subject to a rigorous oversight procedure. [31] [32] [33] In 2023, researchers have built a hybrid biocomputer that combines laboratory-grown human brain organoids with conventional circuits, and can complete tasks such as voice recognition. [34] Cerebral Organoids are currently being used to research and develop Organoid Intelligence (OI) technologies. [35]
Gastrointestinal organoids refer to organoids that recapitulate structures of the gastrointestinal tract. The gastrointestinal tract arises from the endoderm, which during development forms a tube that can be divided in three distinct regions, which give rise to, along with other organs, the following sections of the gastrointestinal tract: [4]
Organoids have been created for the following structures of the gastrointestinal tract:
Intestinal organoids [15] have thus far been among the gut organoids generated directly from intestinal tissues or pluripotent stem cells. [4] One way human pluripotent stem cells can be driven to form intestinal organoids is through first the application of activin A to drive the cells into a mesoendodermal identity, followed by the pharmacological upregulation of Wnt3a and Fgf4 signaling pathways as they have been demonstrated to promote posterior gut fate. [4] Intestinal organoids have also been generated from intestinal stem cells, extracted from adult tissue and cultured in 3D media. [28] These adult stem cell-derived organoids are often referred to as enteroids or colonoids, depending on their segment of origin, and have been established from both the human and murine intestine. [15] [36] [37] Intestinal organoids consist of a single layer of polarized intestinal epithelial cells surrounding a central lumen. As such, recapitulate the crypt-villus structure of the intestine, by recapitulating its function, physiology and organization, and maintaining all the cell types found normally in the structure including intestinal stem cells. [4] Thus, intestinal organoids are a valuable model to study intestinal nutrient transport, [38] [39] drug absorption and delivery, [40] [41] nanomaterials and nanomedicine, [42] [43] incretin hormone secretion, [44] [45] and infection by various enteropathogens. [46] [47] For example, Qun Wang's team rationally designed artificial virus nanoparticles as oral drug delivery vehicles (ODDVs) with gut organoid-derived mucosal models [48] and demonstrated a new concept of using newly established colon organoids as tools for high-throughput drug screening, toxicity testing, and oral drug development. [49] Or recently, Sakib, S., and Zou, S. developed graphene oxide nanoparticles for delivering siRNA regulating expression of tumor necrosis factor-α, that aimed to treat intestinal organoids exhibiting an inflammatory phenotype. [50] Intestinal organoids also recapitulate the crypt-Villus structure to such a high degree of fidelity that they have been successfully transplanted to mouse intestines, and are hence highly regarded as a valuable model for research. [4] One of the fields of research that intestinal organoids have been utilized is that of stem cell niche. Intestinal organoids were used to study the nature of the intestinal stem cell niche, and research done with them demonstrated the positive role IL-22 has in maintaining in intestinal stem cells, [51] along with demonstrating the roles of other cell types like neurons and fibroblasts in maintenance of intestinal stem cells. [28] In the field of infection biology, different intestinal organoid-based model systems have been explored. On one hand, organoids can be infected in bulk by simply mixing them with the enteropathogen of interest. [52] However, to model infection via a more natural route starting from the intestinal lumen, microinjection of the pathogen is required. [53] [54] In addition, the polarity of intestinal organoids can be inverted, [55] and they can even be dissociated into single cells and cultured as 2D monolayers [56] [57] in order to make both the apical and basolateral sides of the epithelium more easily accessible. Intestinal organoids have also demonstrated therapeutic potential. [58]
In order to more accurately recapitulate the intestine in vivo, co-cultures of intestinal organoids and immune cells have been developed. [57] Furthermore, organ-on-a-chip models combine intestinal organoids with other cell types such as endothelial or immune cells as well as peristaltic flow. [59] [60]
Gastric organoids recapitulate at least partly the physiology of the stomach. Gastric organoids have been generated directly from pluripotent stem cells through the temporal manipulation of the FGF, WNT, BMP, retinoic acid and EGF signalling pathways in three-dimensional culture conditions. [61] Gastric organoids have also been generated using LGR5 expressing stomach adult stem cells. [62] Gastric organoids have been used as model for the study of cancer [63] [64] along with human disease [61] and development. [61] For example, one study [64] investigated the underlying genetic alterations behind a patient's metastatic tumor population, and identified that unlike the patient's primary tumor, the metastasis had both alleles of the TGFBR2 gene mutated. To further assess the role of TGFBR2 in the metastasis, the investigators created organoids where TGFBR2 expression is knocked down, through which they were able to demonstrate that reduced TGFBR2 activity leads to invasion and metastasis of cancerous tumors both in vitro and in vivo.
Lingual organoids are organoids that recapitulate, at least partly, aspects of the tongue physiology. Epithelial lingual organoids have been generated using BMI1 expressing epithelial stem cells in three-dimensional culture conditions through the manipulation of EGF, WNT, and TGF-β. [65] This organoid culture, however, lacks taste receptors, as these cells do not arise from Bmi1 expressing epithelial stem cells. [65] Lingual taste bud organoids containing taste cells, however, have been created using the LGR5+ or CD44+ stem/progenitor cells of circumvallate (CV) papilla tissue. [66] These taste bud organoids have been successfully created both directly from isolated Lgr5- or LGR6-expressing taste stem/progenitor cells. [67] and indirectly, through the isolation, digestion, and subsequent culturing of CV tissue containing Lgr5+ or CD44+ stem/progenitor cells. [66]
3D organoid models of brain cancer derived from either patient derived explants (PDX) or direct from cancer tissue is now easily achievable and affords high-throughput screening of these tumors against the current panel of approved drugs form around the world.
Self-assembled cell aggregates consisting of BMECs, astrocytes, and pericytes are emerging as a potential alternative to transwell and microfluidic models for certain applications. These organoides can generate many features of the BBB, such as the expression of tight junctions, molecular transporters, and drug efflux pumps, and can therefore be used to model drug transport across the BBB. Also, they can serve as a model for evaluating the interactions between the BBB and adjacent brain tissue and provide a platform for understanding the combined abilities of a new drug to overcome the BBB and its effect on brain tissue. In addition, such models are highly scalable and easier to manufacture and operate than microfluidic devices. However, they have limited ability to reconstruct the morphology and physiology of the BBB and are unable to simulate physiological flow and shear stress.
Organoids enable to study how cells interact together in an organ, their interaction with their environment, how diseases affect them and the effect of drugs. In vitro culture makes this system easy to manipulate and facilitates their monitoring. While organs are difficult to culture because their size limits the penetration of nutrients, the small size of organoids limits this problem. On the other hand, they do not exhibit all organ features and interactions with other organs are not recapitulated in vitro. While research on stem cells and regulation of stemness was the first field of application of intestinal organoids, [15] they are now also used to study e.g. uptake of nutrients, drug transport and secretion of incretin hormones. [102] This is of great relevance in the context of malabsorption diseases as well as metabolic diseases such as obesity, insulin resistance, and diabetes.
Organoids provide an opportunity to create cellular models of human disease, which can be studied in the laboratory to better understand the causes of disease and identify possible treatments. The power of organoids in this regard was first shown for a genetic form of microcephaly, where patient cells were used to make cerebral organoids, which were smaller and showed abnormalities in early generation of neurons. [22] In another example, the genome editing system called CRISPR was applied to human pluripotent stem cells to introduce targeted mutations in genes relevant to two different kidney diseases, polycystic kidney disease and focal segmental glomerulosclerosis. [83] These CRISPR-modified pluripotent stem cells were subsequently grown into human kidney organoids, which exhibited disease-specific phenotypes. Kidney organoids from stem cells with polycystic kidney disease mutations formed large, translucent cyst structures from kidney tubules. When cultured in the absence of adherent cues (in suspension), these cysts reached sizes of 1 cm in diameter over several months. [103] Kidney organoids with mutations in a gene linked to focal segmental glomerulosclerosis developed junctional defects between podocytes, the filtering cells affected in that disease. [104] Importantly, these disease phenotypes were absent in control organoids of identical genetic background, but lacking the CRISPR mutations. [83] [103] [104] Comparison of these organoid phenotypes to diseased tissues from mice and humans suggested similarities to defects in early development. [103] [104]
As first developed by Takahashi and Yamanaka in 2007, induced pluripotent stem cells (iPSC) can also be reprogrammed from patient skin fibroblasts. [105] These stem cells carry the exact genetic background of the patient including any genetic mutations which might contribute to the development of human disease. Differentiation of these cells into kidney organoids has been performed from patients with Lowe Syndrome due to ORCL1 mutations. [106] This report compared kidney organoids differentiated from patient iPSC to unrelated control iPSC and demonstrated an inability of patient kidney cells to mobilise transcription factor SIX2 from the golgi complex. [106] Because SIX2 is a well characterised marker of nephron progenitor cells in the cap mesenchyme, the authors concluded that renal disease frequently seen in Lowe Syndrome (global failure of proximal tubule reabsorption or renal Fanconi syndrome) could be related to alteration in nephron patterning arising from nephron progenitor cells lacking this important SIX2 gene expression. [106]
Other studies have used CRISPR gene editing to correct the patient's mutation in the patient iPSC cells to create an isogenic control, which can be performed simultaneously with iPSC reprogramming. [107] [108] [109] Comparison of a patient iPSC derived organoid against an isogenic control is the current gold standard in the field as it permits isolation of the mutation of interest as the only variable within the experimental model. [110] In one such report, kidney organoids derived from iPSC of a patient with Mainzer-Saldino Syndrome due to compound heterozygous mutations in IFT140 were compared to an isogenic control organoid in which an IFT140 variant giving rise to a non-viable mRNA transcript was corrected by CRISPR. [108] Patient kidney organoids demonstrated abnormal ciliary morphology consistent with existing animal models which was rescued to wild type morphology in the gene corrected organoids. [108] Comparative transcriptional profiling of epithelial cells purified from patient and control organoids highlighted pathways involved in cell polarity, cell-cell junctions and dynein motor assembly, some of which had been implicated for other genotypes within the phenotypic family of renal ciliopathies. [108] Another report utilising an isogenic control demonstrated abnormal nephrin localisation in the glomeruli of kidney organoids generated from a patient with congenital nephrotic syndrome. [109]
Things such as epithelial metabolism can also be modelled. [111]
Intestinal organoids grown from rectal biopsies using culture protocols established by the Clevers group have been used to model cystic fibrosis, [112] and led to the first application of organoids for personalised treatment. [113] Cystic fibrosis is an inherited disease that is caused by gene mutations of the cystic fibrosis transmembrane conductance regulator gene that encodes an epithelial ion channel necessary for healthy epithelial surface fluids. Studies by the laboratory of Jeffrey Beekman (Wilhelmina Children's Hospital, University Medical Center Utrecht, The Netherlands) described in 2013 that stimulation of colorectal organoids with cAMP-raising agonists such as forskolin or cholera toxin induced rapid swelling of organoids in a fully CFTR dependent manner. [112] Whereas organoids from non-cystic fibrosis subjects swell in response to forskolin as a consequence of fluid transport into the organoids' lumens, this is severely reduced or absent in organoids derived from people with cystic fibrosis. Swelling could be restored by therapeutics that repair the CFTR protein (CFTR modulators), indicating that individual responses to CFTR modulating therapy could be quantitated in a preclinical laboratory setting. Schwank et al. also demonstrated that the intestinal cystic fibrosis organoid phenotype could be repaired by CRISPR-Cas9 gene editing in 2013. [114]
Follow-up studies by Dekkers et al. in 2016 revealed that quantitative differences in forskolin-induced swelling between intestinal organoids derived from people with cystic fibrosis associate with known diagnostic and prognostic markers such as CFTR gene mutations or in vivo biomarkers of CFTR function. [113] In addition, the authors demonstrated that CFTR modulator responses in intestinal organoids with specific CFTR mutations correlated with published clinical trial data of these treatments. This led to preclinical studies where organoids from patients with extremely rare CFTR mutations for who no treatment was registered were found to respond strongly to a clinically available CFTR modulator. The suggested clinical benefit of treatment for these subjects based on the preclinical organoid test was subsequently confirmed upon clinical introduction of treatment by members of the clinical CF center under supervision of Kors van der Ent (Department of Paediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, The Netherlands). These studies show for the first time that organoids can be used for the individual tailoring of therapy or personalised medicine.
The self-renewal and regenerative properties of intestinal organoids make them promising candidates for transplantation therapies, particularly for disease involving epithelial barrier disruption. Notably, transplantation of organoids into the duodenum of mice has been shown to aid in the recovery of mucosal damages on mice with ischemia-reperfusion injury. [115]
The first successful transplantation of an organoid into a human, a patient with ulcerative colitis whose cells were used for the organoid, was carried out in 2022. [116] [117]
Organoids offer researchers an exceptional model to study developmental biology. [118] Since the identification of pluripotent stem cells, there have been great advancements in directing pluripotent stem cells fate in vitro using 2D cultures. [118] These advancements in PSC fate direction, coupled with the advancements in 3D culturing techniques allowed for the creation of organoids that recapitulate the properties of various specific subregions of a multitude of organs. [118] The use of these organoids has thus greatly contributed to expanding our understanding of the processes of organogenesis, and the field of developmental biology. [118] In central nervous system development, for example, organoids have contributed to our understanding of the physical forces that underlie retinal cup formation. [118] [119] More recent work has extended cortical organoid growth periods extensively and at nearly a year under specific differentiation conditions, the organoids persist and have some features of human fetal development stages. [120]
A fibroblast is a type of biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells of connective tissue in animals.
Gastrulation is the stage in the early embryonic development of most animals, during which the blastula, or in mammals the blastocyst, is reorganized into a two-layered or three-layered embryo known as the gastrula. Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body, and internalized one or more cell types including the prospective gut.
Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose, but is not limited to applications involving cells and tissue scaffolds. While it was once categorized as a sub-field of biomaterials, having grown in scope and importance, it can be considered as a field of its own.
Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells, they can be found in juvenile, adult animals, and humans, unlike embryonic stem cells.
Induced pluripotent stem cells are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka and Kazutoshi Takahashi in Kyoto, Japan, who together showed in 2006 that the introduction of four specific genes, collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. Shinya Yamanaka was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent."
Renal stem cells are self-renewing, multipotent stem cells which are able to give rise to all the cell types of the kidney. It is involved in the homeostasis and repair of the kidney, and holds therapeutic potential for treatment of kidney failure.
An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system. It constitutes the subject matter of significant biomedical engineering research, more precisely in bio-MEMS. The convergence of labs-on-chips (LOCs) and cell biology has permitted the study of human physiology in an organ-specific context. By acting as a more sophisticated in vitro approximation of complex tissues than standard cell culture, they provide the potential as an alternative to animal models for drug development and toxin testing.
A neural, or brain organoid, describes an artificially grown, in vitro, tissue resembling parts of the human brain. Neural organoids are created by culturing pluripotent stem cells into a three-dimensional culture that can be maintained for years. The brain is an extremely complex system of heterogeneous tissues and consists of a diverse array of neurons and glial cells. This complexity has made studying the brain and understanding how it works a difficult task in neuroscience, especially when it comes to neurodevelopmental and neurodegenerative diseases. The purpose of creating an in vitro neurological model is to study these diseases in a more defined setting. This 3D model is free of many potential in vivo limitations. The varying physiology between human and other mammalian models limits the scope of animal studies in neurological disorders. Neural organoids contain several types of nerve cells and have anatomical features that recapitulate regions of the nervous system. Some neural organoids are most similar to neurons of the cortex. In some cases, the retina, spinal cord, thalamus and hippocampus. Other neural organoids are unguided and contain a diversity of neural and non-neural cells. Stem cells have the potential to grow into many different types of tissues, and their fate is dependent on many factors. Below is an image showing some of the chemical factors that can lead stem cells to differentiate into various neural tissues; a more in-depth table of generating specific organoid identity has been published. Similar techniques are used on stem cells used to grow cerebral organoids.
Directed differentiation is a bioengineering methodology at the interface of stem cell biology, developmental biology and tissue engineering. It is essentially harnessing the potential of stem cells by constraining their differentiation in vitro toward a specific cell type or tissue of interest. Stem cells are by definition pluripotent, able to differentiate into several cell types such as neurons, cardiomyocytes, hepatocytes, etc. Efficient directed differentiation requires a detailed understanding of the lineage and cell fate decision, often provided by developmental biology.
Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, or partial regeneration, which involves closing up the injury site with some gradation of scar tissue. Some tissues such as skin, the vas deferens, and large organs including the liver can regrow quite readily, while others have been thought to have little or no capacity for regeneration following an injury.
Melissa Helen Little is an Australian scientist and academic who has served as director of Cell Biology at the Murdoch Children's Research Institute since 2019. She is also a Professor in the Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, and Program Leader of Stem Cells Australia. In January 2022, she became CEO of the Novo Nordisk Foundation Center for Stem Cell Medicine reNEW, an international stem cell research center based at University of Copenhagen, and a collaboration between the University of Copenhagen, Denmark, Murdoch Children’s Research Institute, Australia, and Leiden University Medical Center, The Netherlands.
Air liquid interface cell culture (ALI) is a method of cell culture by which basal stem cells are grown with their basal surfaces in contact with media, and the top of the cellular layer is exposed to the air. The cells are then lifted and media is changed until the development of a mucociliary phenotype of a pseudostratified epithelium, similar to the tracheal epithelium.
Sergiu P. Pașca is a Romanian-American scientist and physician at Stanford University in California. He is renowned for his groundbreaking work creating and developing stem cell-based models of the human brain to gain insights into neuropsychiatric disease. His lab was the first to develop and name assembloids: multi-unit self-organizing structures created in 3D cultures that allow for the study of human neural circuit and systems functions in vitro. Pașca’s lab generated and published human cortico-striatal and cortico-motor assembloids in 2020. Combining regionalized neural organoids pioneered in the lab and studies with human forebrain assembloids and transplantation, in 2024, Pașca developed a therapeutic for a severe genetic disorder called Timothy Syndrome, which was published on the cover of Nature.
Cultrex Basement Membrane Extract (BME) is the trade name for a extracellular protein mixture secreted by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells and manufactured into a hydrogel by R&D Systems, a brand of Bio-Techne. Similar to Matrigel, this hydrogel is a natural extracellular matrix that mimics the complex extracellular environment within complex tissues. It is used as a general cell culture substrate across a wide variety of research applications.
Experimental models of Alzheimer's disease are organism or cellular models used in research to investigate biological questions about Alzheimer's disease as well as develop and test novel therapeutic treatments. Alzheimer's disease is a progressive neurodegenerative disorder associated with aging, which occurs both sporadically or due to familial passed mutations in genes associated with Alzheimer's pathology. Common symptoms associated with Alzheimer's disease include: memory loss, confusion, and mood changes.
Samira Musah is an American biomedical engineer and professor at the Duke University Pratt School of Engineering. She is known for her work in biomimetic systems, in particular for her work in developing an organ-on-a-chip model of the kidney glomerulus during her postdoctoral fellowship.
Intestines-on-a-chip are microfluidic bioengineered 3D-models of the real organ, which better mimic physiological features than conventional 3D intestinal organoid culture. A variety of different intestine-on-a-chip models systems have been developed and refined, all holding their individual strengths and weaknesses and collectively holding great promise to the ultimate goal of establishing these systems as reliable high-throughput platforms for drug testing and personalised medicine. The intestine is a highly complex organ system performing a diverse set of vital tasks, from nutrient digestion and absorption, hormone secretion, and immunological processes to neuronal activity, which makes it particularly challenging to model in vitro.
Meritxell Huch is a stem cell biologist and director at the Max Planck Institute of Molecular Cell Biology and Genetics. Her research considers tissue regeneration and the development of tissue-specific disease models for human organs. She was awarded a European Research Council Consolidator Grant in 2023.
A myelinoid or myelin organoid is a three dimensional in vitro cultured model derived from human pluripotent stem cells (hPSCs) that represents various brain regions, the spinal cord or the peripheral nervous system in early fetal human development. Myelinoids have the capacity to recapitulate aspects of brain developmental processes, microenvironments, cell to cell interaction, structural organization and cellular composition. The differentiating aspect dictating whether an organoid is deemed a cerebral organoid/brain organoid or myelinoid is the presence of myelination and compact myelin formation that is a defining feature of myelinoids. Due to the complex nature of the human brain, there is a need for model systems which can closely mimic complicated biological processes. Myelinoids provide a unique in vitro model through which myelin pathology, neurodegenerative diseases, developmental processes and therapeutic screening can be accomplished.
An assembloid is an in vitro model that combines two or more organoids, spheroids, or cultured cell types to recapitulate structural and functional properties of an organ. They are typically derived from induced pluripotent stem cells. Assembloids have been used to study cell migration, neural circuit assembly, neuro-immune interactions, metastasis, and other complex tissue processes. The term "assembloid" was coined by Sergiu P. Pașca's lab in 2017.