Tissue Organoids Research Articles

Microfluidic Bioprinting for Engineering Vascularized Tissues and Organoids.

Engineering vascularized tissue constructs and organoids has been historically challenging. Here we describe a novel method based on microfluidic bioprinting to generate a scaffold with multilayer interlacing hydrogel microfibers. To achieve smooth bioprinting, a core-sheath microfluidic printhead containing a composite bioink formulation extruded from the core flow and the crosslinking solution carried by the sheath flow, was designed and fitted onto the bioprinter. By blending gelatin methacryloyl (GelMA) with alginate, a polysaccharide that undergoes instantaneous ionic crosslinking in the presence of select divalent ions, followed by a secondary photocrosslinking of the GelMA component to achieve permanent stabilization, a microfibrous scaffold could be obtained using this bioprinting strategy. Importantly, the endothelial cells encapsulated inside the bioprinted microfibers can form the lumen-like structures resembling the vasculature over the course of culture for 16 days. The endothelialized microfibrous scaffold may be further used as a vascular bed to construct a vascularized tissue through subsequent seeding of the secondary cell type into the interstitial space of the microfibers. Microfluidic bioprinting provides a generalized strategy in convenient engineering of vascularized tissues at high fidelity.

Linked read sequencing resolves complex genomic rearrangements in gastric cancer metastases

BackgroundGenome rearrangements are critical oncogenic driver events in many malignancies. However, the identification and resolution of the structure of cancer genomic rearrangements remain challenging even with whole genome sequencing.MethodsTo identify oncogenic genomic rearrangements and resolve their structure, we analyzed linked read sequencing. This approach relies on a microfluidic droplet technology to produce libraries derived from single, high molecular weight DNA molecules, 50 kb in size or greater. After sequencing, the barcoded sequence reads provide long range genomic information, identify individual high molecular weight DNA molecules, determine the haplotype context of genetic variants that occur across contiguous megabase-length segments of the genome and delineate the structure of complex rearrangements. We applied linked read sequencing of whole genomes to the analysis of a set of synchronous metastatic diffuse gastric cancers that occurred in the same individual.ResultsWhen comparing metastatic sites, our analysis implicated a complex somatic rearrangement that was present in the metastatic tumor. The oncogenic event associated with the identified complex rearrangement resulted in an amplification of the known cancer driver gene FGFR2. With further investigation using these linked read data, the FGFR2 copy number alteration was determined to be a deletion-inversion motif that underwent tandem duplication, with unique breakpoints in each metastasis. Using a three-dimensional organoid tissue model, we functionally validated the metastatic potential of an FGFR2 amplification in gastric cancer.ConclusionsOur study demonstrates that linked read sequencing is useful in characterizing oncogenic rearrangements in cancer metastasis.

Fused cerebral organoids model interactions between brain regions.

Human brain development involves complex interactions between different areas, including long distance neuronal migration or formation of major axonal tracts. 3D cerebral organoids allow the growth of diverse brain regions in vitro, but the random arrangement of regional identities limits the reliable analysis of complex phenotypes. Here, we describe a co-culture method combining various brain regions of choice within one organoid tissue. By fusing organoids specified toward dorsal and ventral forebrain, we generate a dorsal-ventral axis. Using fluorescent reporters, we demonstrate robust directional GABAergic interneuron migration from ventral into dorsal forebrain. We describe methodology for time-lapse imaging of human interneuron migration that is inhibited by the CXCR4 antagonist AMD3100. Our results demonstrate that cerebral organoid fusion cultures can model complex interactions between different brain regions. Combined with reprogramming technology, fusions offer the possibility to analyze complex neurodevelopmental defects using cells from neurological disease patients, and to test potential therapeutic compounds.

3D hydrogel-based microwell arrays as a tumor microenvironment model to study breast cancer growth

The tumor microenvironment (TME) is distinctly heterogeneous and is involved in tumor growth, metastasis, and drug resistance. Mimicking this diverse microenvironment is essential for understanding tumor growth and metastasis. Despite the substantial scientific progress made with traditional cell culture methods, microfabricated three-dimensional (3D) cell cultures that can be precisely controlled to mimic the changes occur in the TME over tumor progression are necessary for simulating organ-specific TME in vitro. In this research, to simulate the breast cancer TME, microwell arrays of defined geometry and dimensions were fabricated using photo-reactive hydrogels for a cancer cell line and primary explant tissue culture. Microwell arrays fabricated from 4-arm polyethylene glycol acrylate and methacrylated gelatin with different degrees of methacrylation for controlled cell–matrix interactions and tunable stiffness were used to create a platform for studying the effects of distinct hydrogel compositions and stiffness on tumor formation. Using these microwell arrays, size-controlled spheroids of human breast cancer cell line HCC1806 were formed and the cell attachment properties, viability, metabolic activity, and migration levels of these spheroids were examined. In addition, primary mammary organoid tissues explanted from mice were successfully cultured in these hydrogel-based microwell arrays and the organoid morphology and viability, as well as organoid branching were studied. The microwell array platform developed and characterized in this study could be useful for generating a tissue-specific TME for in vitro high throughput studies of breast cancer development and progression as well as in drug screening studies for breast cancer treatment.

Metabolic Imaging of Head and Neck Cancer Organoids.

Head and neck cancer patients suffer from toxicities, morbidities, and mortalities, and these ailments could be minimized through improved therapies. Drug discovery is a long, expensive, and complex process, so optimized assays can improve the success rate of drug candidates. This study applies optical imaging of cell metabolism to three-dimensional in vitro cultures of head and neck cancer grown from primary tumor tissue (organoids). This technique is advantageous because it measures cell metabolism using intrinsic fluorescence from NAD(P)H and FAD on a single cell level for a three-dimensional in vitro model. Head and neck cancer organoids are characterized alone and after treatment with standard therapies, including an antibody therapy, a chemotherapy, and combination therapy. Additionally, organoid cellular heterogeneity is analyzed quantitatively and qualitatively. Gold standard measures of treatment response, including cell proliferation, cell death, and in vivo tumor volume, validate therapeutic efficacy for each treatment group in a parallel study. Results indicate that optical metabolic imaging is sensitive to therapeutic response in organoids after 1 day of treatment (p<0.05) and resolves cell subpopulations with distinct metabolic phenotypes. Ultimately, this platform could provide a sensitive high-throughput assay to streamline the drug discovery process for head and neck cancer.

Organotypic Models of Lung Cancer.

Human lung cancer is one of the leading causes of death worldwide, with nearly 2 million of new cases diagnosed each year, often too late for a successful therapeutic intervention. In this chapter, organotypic models of lung cancer will be reviewed. Ex vivo tissue explants, spheroids, organoids, and novel bioengineering approaches are currently being used to study human lung cancer. Although there is no ideal method that will fully recapitulate the complex human lung architecture, the three-dimensional (3D) organotypic models described here represent a major advance from classical two-dimensional (2D) tissue culture models. Organotypic tissue cultures are better at predicting in vivo tissue responses to anticancer drugs or carcinogenic toxins. In addition, there is also a possibility to use these systems as part of personalized medicine (e.g., to assist clinicians in selecting appropriate therapeutic choices based on individual patient-derived tissue responses to drugs in vitro). There is still a need for improvement in the 3D culture systems, such as automation for high-throughput testing and reduction of costs. However, given the large number of failed clinical trials due to safety or efficacy reasons, more attention should be given to these more physiologically relevant 3D organotypic tissue culture models.

Integrin suppresses neurogenesis and regulates brain tissue assembly in planarian regeneration.

Animals capable of adult regeneration require specific signaling to control injury-induced cell proliferation, specification and patterning, but comparatively little is known about how the regeneration blastema assembles differentiating cells into well-structured functional tissues. Using the planarian Schmidtea mediterranea as a model, we identify β1-integrin as a crucial regulator of blastema architecture. β1-integrin(RNAi) animals formed small head blastemas with severe tissue disorganization, including ectopic neural spheroids containing differentiated neurons normally found in distinct organs. By mimicking aspects of normal brain architecture but without normal cell-type regionalization, these spheroids bore a resemblance to mammalian tissue organoids synthesized in vitro We identified one of four planarian integrin-alpha subunits inhibition of which phenocopied these effects, suggesting that a specific receptor controls brain organization through regeneration. Neoblast stem cells and progenitor cells were mislocalized in β1-integrin(RNAi) animals without significantly altered body-wide patterning. Furthermore, tissue disorganization phenotypes were most pronounced in animals undergoing brain regeneration and not homeostatic maintenance or regeneration-induced remodeling of the brain. These results suggest that integrin signaling ensures proper progenitor recruitment after injury, enabling the generation of large-scale tissue organization within the regeneration blastema.

Concise Review: Salivary Gland Regeneration: Therapeutic Approaches from Stem Cells to Tissue Organoids.

The human salivary gland (SG) has an elegant architecture of epithelial acini, connecting ductal branching structures, vascular and neuronal networks that together function to produce and secrete saliva. This review focuses on the translation of cell- and tissue-based research toward therapies for patients suffering from SG hypofunction and related dry mouth syndrome (xerostomia), as a consequence of radiation therapy or systemic disease. We will broadly review the recent literature and discuss the clinical prospects of stem/progenitor cell and tissue-based therapies for SG repair and/or regeneration. Thus far, several strategies have been proposed for the purpose of restoring SG function: (1) transplanting autologous SG-derived epithelial stem/progenitor cells; (2) exploiting nonepithelial cells and/or their bioactive lysates; and (3) tissue engineering approaches using 3D (three-dimensional) biomaterials loaded with SG cells and/or bioactive cues to mimic in vivo SGs. We predict that further scientific improvement in each of these areas will translate to effective therapies toward the repair of damaged glands and the development of miniature SG organoids for the fundamental restoration of saliva secretion.

Correction to: Hum Gene Ther 2016;27(6):417-418.

Human Gene TherapyVol. 27, No. 7 Correction NoticesFree AccessCorrection to: Hum Gene Ther 2016;27(6):417–418Published Online:18 Jul 2016https://doi.org/10.1089/hum.2016.29029.amg.correxAboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail In the June 2016 issue of Human Gene Therapy (vol. 27, no. 7, pp. 417–418), the editorial article “Gene Editing: Practical Application in the Lab,” by Dr. Aron M. Geurts and Dr. Stephen C. Ekker, when describing the content of the Takata et al. article in this same issue referred to human stem cells rather than mouse stem cells. They also cited a target gene as “FGF5” as a human gene rather than the mouse version “Fgf5.” To clarify, the text reading:“Finally, in an elegant example of cellular genome editing, Takata et al. describe herein a simple design method for inserting reporter genes into human stem cells and 3D tissue organoids, which they call GET (genome editing with targeting vector), further expanding the examples and utility of genome editing in human stem cell systems. Their approach was complemented by transposon-based RNA interference (RNAi) to fine-tune inducible knockdown of a target gene, FGF5, in a titratable and time-dependent fashion.”should instead read:“Finally, in an elegant example of cellular genome editing, Takata et al. describe herein a simple design method for inserting reporter genes into mouse stem cells and 3D tissue organoids, which they call GET (genome editing with targeting vector), further expanding the examples and utility of genome editing in mouse stem cell systems. Their approach was complemented by transposon-based RNA interference (RNAi) to fine-tune inducible knockdown of a target gene, Fgf5, in a titratable and time-dependent fashion.”The online version of the article has been corrected to reflect this change.The authors wish to apologize for the error.FiguresReferencesRelatedDetails Volume 27Issue 7Jul 2016 InformationCopyright 2016, Mary Ann Liebert, Inc.To cite this article:Correction to: Hum Gene Ther 2016;27(6):417–418.Human Gene Therapy.Jul 2016.559-559.http://doi.org/10.1089/hum.2016.29029.amg.correxPublished in Volume: 27 Issue 7: July 18, 2016PDF download

Shape Transformations of Epithelial Shells

Regulated deformations of epithelial sheets are frequently foreshadowed by patterning of their mechanical properties. The connection between patterns of cell properties and the emerging tissue deformations is studied in multiple experimental systems, but the general principles remain poorly understood. For instance, it is in general unclear what determines the direction in which the patterned sheet is going to bend and whether the resulting shape transformation will be discontinuous or smooth. Here these questions are explored computationally, using vertex models of epithelial shells assembled from prismlike cells. In response to rings and patches of apical cell contractility, model epithelia smoothly deform into invaginated or evaginated shapes similar to those observed in embryos and tissue organoids. Most of the observed effects can be captured by a simpler model with polygonal cells, modified to include the effects of the apicobasal polarity and natural curvature of epithelia. Our models can be readily extended to include the effects of multiple constraints and used to describe a wide range of morphogenetic processes.

SP-0584: The potential of normal tissue organoid cultures

SP-0584: The potential of normal tissue organoid cultures

Multi-compartmental biomaterial scaffolds for patterning neural tissue organoids in models of neurodevelopment and tissue regeneration

Biomaterials are becoming an essential tool in the study and application of stem cell research. Various types of biomaterials enable three-dimensional culture of stem cells, and, more recently, also enable high-resolution patterning and organization of multicellular architectures. Biomaterials also hold potential to provide many additional advantages over cell transplants alone in regenerative medicine. This article describes novel designs for functionalized biomaterial constructs that guide tissue development to targeted regional identities and structures. Such designs comprise compartmentalized regions in the biomaterial structure that are functionalized with molecular factors that form concentration gradients through the construct and guide stem cell development, axis patterning, and tissue architecture, including rostral/caudal, ventral/dorsal, or medial/lateral identities of the central nervous system. The ability to recapitulate innate developmental processes in a three-dimensional environment and under specific controlled conditions has vital application to advanced models of neurodevelopment and for repair of specific sites of damaged or diseased neural tissue.

VSX2 and ASCL1 Are Indicators of Neurogenic Competence in Human Retinal Progenitor Cultures.

Three dimensional (3D) culture techniques are frequently used for CNS tissue modeling and organoid production, including generation of retina-like tissues. A proposed advantage of these 3D systems is their potential to more closely approximate in vivo cellular microenvironments, which could translate into improved manufacture and/or maintenance of neuronal populations. Visual System Homeobox 2 (VSX2) labels all multipotent retinal progenitor cells (RPCs) and is known to play important roles in retinal development. In contrast, the proneural transcription factor Acheate scute-like 1 (ASCL1) is expressed transiently in a subset of RPCs, but is required for the production of most retinal neurons. Therefore, we asked whether the presence of VSX2 and ASCL1 could gauge neurogenic potential in 3D retinal cultures derived from human prenatal tissue or ES cells (hESCs). Short term prenatal 3D retinal cultures displayed multiple characteristics of human RPCs (hRPCs) found in situ, including robust expression of VSX2. Upon initiation of hRPC differentiation, there was a small increase in co-labeling of VSX2+ cells with ASCL1, along with a modest increase in the number of PKCα+ neurons. However, 3D prenatal retinal cultures lost expression of VSX2 and ASCL1 over time while concurrently becoming refractory to neuronal differentiation. Conversely, 3D optic vesicles derived from hESCs (hESC-OVs) maintained a robust VSX2+ hRPC population that could spontaneously co-express ASCL1 and generate photoreceptors and other retinal neurons for an extended period of time. These results show that VSX2 and ASCL1 can serve as markers for neurogenic potential in cultured hRPCs. Furthermore, unlike hESC-OVs, maintenance of 3D structure does not independently convey an advantage in the culture of prenatal hRPCs, further illustrating differences in the survival and differentiation requirements of hRPCs extracted from native tissue vs. those generated entirely in vitro.

Abstract 3461: RSK2 is a driver of estrogen receptor positive breast cancer

Abstract For unknown reasons, high levels of active Ser/Thr protein kinase RSK in estrogen receptor α (ERα)-positive (ER+) breast cancer patients correlate with better responsiveness to anti-estrogen therapies. Investigation of these surprising observations led us to discover an unanticipated mechanism in which ERα controls RSK2 nuclear accumulation. RSK2 is retained in the nucleus by physical association with ERα and this interaction is disrupted by anti-estrogen treatment. Consistent with these findings, in primary human ER+ breast tissue organoids, 4-hydroxy-tamoxifen (4-OHT) drove export of RSK2 to the cytoplasm. Importantly, RSK2 nuclear accumulation is critical for the expression of the oncogene, cyclin D1. This conclusion is supported by the observations that a RSK2 mutant, which cannot accumulate in the nucleus, does not rescue cyclin D1 in cells silenced for endogenous RSK2. Analysis of RNAseq data shows that ERα and RSK2 cooperatively regulate a transcriptional program, which includes cyclin D1. The physiological relevance of these conclusions is supported by our observations that in ∼60% of ER+ breast cancer patients, active nuclear RSK correlates with ERα and cyclin D1 levels. Taken together, these findings suggest that responsiveness to endocrine-based therapy is driven by reduced RSK2 nuclear accumulation, which in turn reduces expression of cyclin D1 and of other tumor-promoting effectors. Based on these observations we hypothesized that nuclear RSK2 cooperates with ERα and is a physiologically relevant driver of ER+ breast cancer. To test this hypothesis we generated a transgenic mouse model in which the MMTV promoter controls expression of RSK2 fused with the nuclear localization signal (NLS) of SV40. Strikingly, in ∼50% of transgenic mice forced nuclear accumulation of RSK2 in the mammary gland caused hyperplasia and ductal carcinoma in situ (DCIS). These results are the first demonstration that RSK2 can drive proliferation and transformation in vivo. Transgenic animals had a 4-fold increase in the number of cyclin D1 expressing cells and a 6-fold increase in Ki67 levels. Surprisingly, in vivo expression of nuclear RSK2 expanded the population of ER+ cells. These results demonstrate, for the first time, that nuclear RSK2 drives the amplification of the cell population relevant to ER+ breast cancer. In agreement with these observations we found that overexpression of ERα in the mouse mammary gland expands exclusively, by ∼3 fold, the cell population that co-expresses ERα and active nuclear RSK. These results further support our hypothesis that RSK2 cooperates with ERα and is an important drug target for ER+ breast cancer. Citation Format: Katarzyna Ludwik, Deborah Lannigan. RSK2 is a driver of estrogen receptor positive breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3461. doi:10.1158/1538-7445.AM2015-3461

Abstract 223: Generation of single cell-derived normal, benign and cancer mini-prostates from primary patient-derived tissues

Abstract Clinically effective next generation androgen deprivation therapy (ADT) and androgen receptor (AR)-directed therapies have been developed to treat castration-resistant prostate cancer (CRPC). However, disease progression inevitably occurs, and majority of relapsed tumors continue to overexpress AR. AR mutations and constitutively active AR splice variants (AR-Vs) are detected during ADT and may lead to drug resistance. Therefore, there is dire need to develop models that provide a better understanding of AR signaling and determine markers of ADT resistance in prostate cancer patient cells. Mouse models and existing human prostate cancer cell lines have inherent limitations for deciphering mechanisms of therapy resistance. Unlike the recently reported prostate tissue organoids that were derived at a low efficiency from 7/49 metastatic prostate cancer samples, we have developed a novel and exciting technology to generate normal, benign prostatic hyperplasia (BPH) and cancer “mini-prostates” from both early-stage and advanced prostate cancer patient samples. We have successfully rederived mini-prostates from 17 out of 19 primary prostatectomy tissues. We incorporated developmental epithelial and mesenchymal signals, stem-like cells and growth requirements in 3D cultures for maintaining primary normal, BPH and prostate cancer patient-derived cells as stem-like cell-derived organoids. Our preliminary data show the establishment of patient- single cell-derived normal, BPH and cancer mini-prostates comprised of organoids with glandular tissues that have a thick basement membrane, an outer mesenchymal and inner epithelial cells conveying AR signaling, expressing cytokeratins and secreting PSA. RNA sequencing, expression profiling and ADT revealed that mini-prostate cells maintain the genetic, chemoresistance, and growth rate features of the primary prostate. To model tumor heterogeneity, prostate cells from surgical tissues were isolated upon digital imaging and tissue mapping in mirror sections for AMACR, AR, AR-Vs, p63, Ki67, ERG expression and FISH analysis for TMPRSS2-ERG fusion. Living cells from mapped BPH and cancer clones are being utilized to derive single cells into mini-prostates. Our studies generated novel therapy sensitivity and drug discovery models that would allow for precision medicine and coclinical approaches to be enlisted to reveal chemo- or hormonal-resistance profiles in genetically defined mini-prostates, apply combinatory-targeted therapies and study therapy-induced clonal selection processes to ultimately guide future clinical trials. Citation Format: Monica Bartucci, Michele Patrizii, Eric Huselid, Shamila Yussuf, Nitu Bansal, Kathleen Flaherty, Denis Tolkunov, Hua Zhong, Mark N. Stein, Joseph Bertino, Robert DiPaola, Isaac Kim, Hatem E. Sabaawy. Generation of single cell-derived normal, benign and cancer mini-prostates from primary patient-derived tissues. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 223. doi:10.1158/1538-7445.AM2015-223

Liver-Tumor Hybrid Organoids for Modeling Tumor Growth and Drug Response In Vitro.

Current in vitro models for tumor growth and metastasis are poor facsimiles of in vivo cancer physiology and thus, are not optimal for anti-cancer drug development. Three dimensional (3D) tissue organoid systems, which utilize human cells in a tailored microenvironment, have the potential to recapitulate in vivo conditions and address the drawbacks of current tissue culture dish 2D models. In this study, we created liver-based cell organoids in a rotating wall vessel bioreactor. The organoids were further inoculated with colon carcinoma cells in order to create liver-tumor organoids for in vitro modeling of liver metastasis. Immunofluorescent staining revealed notable phenotypic differences between tumor cells in 2D and inside the organoids. In 2D they displayed an epithelial phenotype, and only after transition to the organoids did the cells present with a mesenchymal phenotype. The cell surface marker expression results suggested that WNT pathway might be involved in the phenotypic changes observed between cells in 2D and organoid conditions, and may lead to changes in cell proliferation. Manipulating the WNT pathway with an agonist and antagonist showed significant changes in sensitivity to the anti-proliferative drug 5-fluoruracil. Collectively, the results show the potential of in vitro 3D liver-tumor organoids to serve as a model for metastasis growth and for testing the response of tumor cells to current and newly discovered drugs.

Biomaterials for integration with 3-D bioprinting.

Bioprinting has emerged in recent years as an attractive method for creating 3-D tissues and organs in the laboratory, and therefore is a promising technology in a number of regenerative medicine applications. It has the potential to (i) create fully functional replacements for damaged tissues in patients, and (ii) rapidly fabricate small-sized human-based tissue models, or organoids, for diagnostics, pathology modeling, and drug development. A number of bioprinting modalities have been explored, including cellular inkjet printing, extrusion-based technologies, soft lithography, and laser-induced forward transfer. Despite the innovation of each of these technologies, successful implementation of bioprinting relies heavily on integration with compatible biomaterials that are responsible for supporting the cellular components during and after biofabrication, and that are compatible with the bioprinting device requirements. In this review, we will evaluate a variety of biomaterials, such as curable synthetic polymers, synthetic gels, and naturally derived hydrogels. Specifically we will describe how they are integrated with the bioprinting technologies above to generate bioprinted constructs with practical application in medicine.

Abstract IA1: Modeling pancreatic cancer biology and medicine

Abstract Pancreatic ductal adenocarcinoma (PDA) tumors characteristically contain an abundant desmoplastic stroma that impedes drug delivery and promotes drug resistance. We have found through genetic, cellular and pharmacological approaches that a variety of cell intrinsic and extrinsic pathways promote pancreatic cancer progression and drug resistance, and methods to modulate such processes will be discussed here. These observations were made first in genetically engineered mouse models of PDA, and have prompted multiple translational efforts to seek patient benefit. Finally, methods to accelerate the discovery to translation process using primary tissue organoids will be introduced. Citation Format: David A. Tuveson. Modeling pancreatic cancer biology and medicine. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr IA1.

Cell and tissue polarity in the intestinal tract during tumourigenesis: cells still know the right way up, but tissue organization is lost

Cell and tissue polarity are tightly coupled and are vital for normal tissue homeostasis. Changes in cellular and tissue organization are common to even early stages of disease, particularly cancer. The digestive tract is the site of the second most common cause of cancer deaths in the developed world. Tumours in this tissue arise in an epithelium that has a number of axes of cell and tissue polarity. Changes in cell and tissue polarity in response to genetic changes that are known to underpin disease progression provide clues about the link between molecular-, cellular- and tissue-based mechanisms that accompany cancer. Mutations in adenomatous polyposis coli (APC) are common to most colorectal cancers in humans and are sufficient to cause tumours in mouse intestine. Tissue organoids mimic many features of whole tissue and permit identifying changes at different times after inactivation of APC. Using gut organoids, we show that tissue polarity is lost very early during cancer progression, whereas cell polarity, at least apical–basal polarity, is maintained and changes only at later stages. These observations reflect the situation in tumours and validate tissue organoids as a useful system to investigate the relationship between cell polarity and tissue organization.

Microstructured Extracellular Matrices in Tissue Engineering and Development: An Update

Microstructured extracellular matrix (ECM), which contains heterogeneous features of the same size scale (5-100μm) as tissue organoids, has become an important material for the engineering of functional tissues and for the study of tissue-level biology. This review describes methods to generate this class of ECM, and highlights recent advances in the application of microstructured ECM to problems in basic and applied biology. It also discusses computational techniques to analyze and optimize the microstructural patterns for a desired functional output.