Chromatin Remodeling in Patient-Derived Colorectal Cancer Models

Patient-Derived Organoids (PDO) and Xenografts (PDX) are the current gold standards for patient-derived models of cancer (PDMC). Nevertheless, how patient tumor cells evolve in these models and the impact on drug response remains unclear. Herein, the transcriptomic and chromatin accessibility landscapes of matched colorectal cancer (CRC) PDO, PDX, PDO-derived PDX (PDOX), and original patient tumors (PT) are compared. Two major remodeling axes are discovered. The first axis delineates PDMC from PT, and the second axis distinguishes PDX and PDO. PDOX are more similar to PDX than PDO, indicating the growth environment is a driving force for chromatin adaptation. Transcription factors (TF) that differentially bind to open chromatins between matched PDO and PDOX are identified. Among them, KLF14 and EGR2 footprints are enriched in PDOX relative to matched PDO, and silencing of KLF14 or EGR2 promoted tumor growth. Furthermore, EPHA4, a shared downstream target gene of KLF14 and EGR2, altered tumor sensitivity to MEK inhibitor treatment. Altogether, patient-derived CRC cells undergo both common and distinct chromatin remodeling in PDO and PDX/PDOX, driven largely by their respective microenvironments, which results in differences in growth and drug sensitivity and needs to be taken into consideration when interpreting their ability to predict clinical outcome.

Human organoids are superior to cell culture models for intestinal barrier research

Loss of intestinal epithelial barrier function is a hallmark in digestive tract inflammation. The detailed mechanisms remain unclear due to the lack of suitable cell-based models in barrier research. Here we performed a detailed functional characterization of human intestinal organoid cultures under different conditions with the aim to suggest an optimized ex-vivo model to further analyse inflammation-induced intestinal epithelial barrier dysfunction. Differentiated Caco2 cells as a traditional model for intestinal epithelial barrier research displayed mature barrier functions which were reduced after challenge with cytomix (TNFα, IFN-γ, IL-1ß) to mimic inflammatory conditions. Human intestinal organoids grown in culture medium were highly proliferative, displayed high levels of LGR5 with overall low rates of intercellular adhesion and immature barrier function resembling conditions usually found in intestinal crypts. WNT-depletion resulted in the differentiation of intestinal organoids with reduced LGR5 levels and upregulation of markers representing the presence of all cell types present along the crypt-villus axis. This was paralleled by barrier maturation with junctional proteins regularly distributed at the cell borders. Application of cytomix in immature human intestinal organoid cultures resulted in reduced barrier function that was accompanied with cell fragmentation, cell death and overall loss of junctional proteins, demonstrating a high susceptibility of the organoid culture to inflammatory stimuli. In differentiated organoid cultures, cytomix induced a hierarchical sequence of changes beginning with loss of cell adhesion, redistribution of junctional proteins from the cell border, protein degradation which was accompanied by loss of epithelial barrier function. Cell viability was observed to decrease with time but was preserved when initial barrier changes were evident. In summary, differentiated intestinal organoid cultures represent an optimized human ex-vivo model which allows a comprehensive reflection to the situation observed in patients with intestinal inflammation. Our data suggest a hierarchical sequence of inflammation-induced intestinal barrier dysfunction starting with loss of intercellular adhesion, followed by redistribution and loss of junctional proteins resulting in reduced barrier function with consecutive epithelial death.

Development of Plasmodium falciparum liver-stages in hepatocytes derived from human fetal liver organoid cultures

Plasmodium falciparum (Pf) parasite development in liver represents the initial step of the life-cycle in the human host after a Pf-infected mosquito bite. While an attractive stage for life-cycle interruption, understanding of parasite-hepatocyte interaction is inadequate due to limitations of existing in vitro models. We explore the suitability of hepatocyte organoids (HepOrgs) for Pf-development and show that these cells permitted parasite invasion, differentiation and maturation of different Pf strains. Single-cell messenger RNA sequencing (scRNAseq) of Pf-infected HepOrg cells has identified 80 Pf-transcripts upregulated on day 5 post-infection. Transcriptional profile changes are found involving distinct metabolic pathways in hepatocytes with Scavenger Receptor B1 (SR-B1) transcripts highly upregulated. A novel functional involvement in schizont maturation is confirmed in fresh primary hepatocytes. Thus, HepOrgs provide a strong foundation for a versatile in vitro model for Pf liver-stages accommodating basic biological studies and accelerated clinical development of novel tools for malaria control.

Modelling adult stem cells and their niche in health and disease with epithelial organoids

Adult stem cells are responsible for homoeostasis and regeneration of epithelial tissues. Stem cell function is regulated by both cell autonomous mechanisms as well as the niche. Deregulated stem cell function contributes to diseases such as cancer. Epithelial organoid cultures generated from tissue-resident adult stem cells have allowed unprecedented insights into the biology of epithelial tissues. The subsequent adaptation of organoid technology enabled the modelling of the communication of stem cells with their cellular and non-cellular niche as well as diseases. Starting from its first model described in 2009, the murine small intestinal organoid, we discuss here how epithelial organoid cultures have been become a prime in vitro research tool for cell and developmental biology, bioengineering, and biomedicine in the last decade.

Uncovering the mode of action of engineered T cells in patient cancer organoids

Extending the success of cellular immunotherapies against blood cancers to the realm of solid tumors will require improved in vitro models that reveal therapeutic modes of action at the molecular level. Here we describe a system, called BEHAV3D, developed to study the dynamic interactions of immune cells and patient cancer organoids by means of imaging and transcriptomics. We apply BEHAV3D to live-track >150,000 engineered T cells cultured with patient-derived, solid-tumor organoids, identifying a 'super engager' behavioral cluster comprising T cells with potent serial killing capacity. Among other T cell concepts we also study cancer metabolome-sensing engineered T cells (TEGs) and detect behavior-specific gene signatures that include a group of 27 genes with no previously described T cell function that are expressed by super engager killer TEGs. We further show that type I interferon can prime resistant organoids for TEG-mediated killing. BEHAV3D is a promising tool for the characterization of behavioral-phenotypic heterogeneity of cellular immunotherapies and may support the optimization of personalized solid-tumor-targeting cell therapies.

Troy/Tnfrsf19 marks epidermal cells that govern interfollicular epidermal renewal and cornification

The skin epidermis is a highly compartmentalized tissue consisting of a cornifying epithelium called the interfollicular epidermis (IFE) and associated hair follicles (HFs). Several stem cell populations have been described that mark specific compartments in the skin but none of them is specific to the IFE. Here, we identify Troy as a marker of IFE and HF infundibulum basal layer cells in developing and adult human and mouse epidermis. Genetic lineage-tracing experiments demonstrate that Troy-expressing basal cells contribute to long-term renewal of all layers of the cornifying epithelium. Single-cell transcriptomics and organoid assays of Troy-expressing cells, as well as their progeny, confirmed stem cell identity as well as the ability to generate differentiating daughter cells. In conclusion, we define Troy as a marker of epidermal basal cells that govern interfollicular epidermal renewal and cornification.

Generation and Characterization of Murine Oral Mucosal Organoid Cultures

The mucous lining covering the inside of our mouth, the oral mucosa, is a highly compartmentalized tissue and can be subdivided into the buccal mucosa, gingiva, lips, palate, and tongue. Its uppermost layer, the oral epithelium, is maintained by adult stem cells throughout life. Proliferation and differentiation of adult epithelial stem cells have been intensively studied using in vivo mouse models as well as two-dimensional (2D) feeder-cell based in vitro models. Complementary to these methods is organoid technology, where adult stem cells are embedded into an extracellular matrix (ECM)-rich hydrogel and provided with a culture medium containing a defined cocktail of growth factors. Under these conditions, adult stem cells proliferate and spontaneously form three-dimensional (3D) cell clusters, the so-called organoids. Organoid cultures were initially established from murine small intestinal epithelial stem cells. However, the method has since been adapted for other epithelial stem cell types. Here, we describe a protocol for the generation and characterization of murine oral mucosal organoid cultures. Primary epithelial cells are isolated from murine tongue tissue, embedded into an ECM hydrogel, and cultured in a medium containing: epidermal growth factor (EGF), R-spondin, and fibroblast growth factor (FGF) 10. Within 7 to 14 days of initial seeding, the resulting organoids can be passaged for further expansion and cryopreservation. We additionally present strategies for the characterization of established organoid cultures via 3D whole-mount imaging and gene-expression analysis. This protocol may serve as a tool to investigate oral epithelial stem cell behavior ex vivo in a reductionist manner.

Cancer research using organoid technology

Organoid technology has rapidly transformed basic biomedical research and contributed to significant discoveries in the last decade. With the application of protocols to generate organoids from cancer tissue, organoid technology has opened up new opportunities for cancer research and therapy. Using organoid cultures derived from healthy tissues, different aspects of tumour initiation and progression are widely studied including the role of pathogens or specific cancer genes. Cancer organoid cultures, on the other hand, are applied to generate biobanks, perform drug screens, and study mutational signatures. With the incorporation of cellular components of the tumour microenvironment such as immune cells into the organoid cultures, the technology is now also exploited in the rapidly advancing field of immuno-oncology. In this review, I discuss how organoid technology is currently being utilised in cancer research and what obstacles are still to be overcome for its broader use in anti-cancer therapy.

Intestinal Regeneration: Regulation by the Microenvironment

Damage to the intestinal stem cell niche can result from mechanical stress, infections, chronic inflammation or cytotoxic therapies. Progenitor cells can compensate for insults to the stem cell population through dedifferentiation. The microenvironment modulates this regenerative response by influencing the activity of signaling pathways, including Wnt, Notch, and YAP/TAZ. For instance, mesenchymal cells and immune cells become more abundant after damage and secrete signaling molecules that promote the regenerative process. Furthermore, regeneration is influenced by the nutritional state, microbiome, and extracellular matrix. Here, we review how all these components cooperate to restore epithelial homeostasis in the intestine after injury.

Establishment of patient-derived cancer organoids for drug-screening applications

Adult stem cell-based organoid technology is a versatile tool for the generation and long-term maintenance of near-native 3D epithelial tissues in vitro. The generation of cancer organoids from primary patient material enables a range of therapeutic agents to be tested in the resulting organoid cultures. Patient-derived cancer organoids therefore hold great promise for personalized medicine. Here, we provide an overview of the protocols used by different groups to establish organoids from various epithelial tissues and cancers, plus the different protocols subsequently used to test the in vitro therapy sensitivity of these patient-derived organoids. We also provide an in-depth protocol for the generation of head and neck squamous cell carcinoma organoids and their subsequent use in semi-automated therapy screens. Establishment of organoids and subsequent screening can be performed within 3 months, although this timeline is highly dependent on a.o. starting material and the number of therapies tested. The protocol provided may serve as a reference to successfully establish organoids from other cancer types and perform drug screenings thereof.

High-Resolution mRNA and Secretome Atlas of Human Enteroendocrine Cells

Enteroendocrine cells (EECs) sense intestinal content and release hormones to regulate gastrointestinal activity, systemic metabolism, and food intake. Little is known about the molecular make-up of human EEC subtypes and the regulated secretion of individual hormones. Here, we describe an organoid-based platform for functional studies of human EECs. EEC formation is induced in vitro by transient expression of NEUROG3. A set of gut organoids was engineered in which the major hormones are fluorescently tagged. A single-cell mRNA atlas was generated for the different EEC subtypes, and their secreted products were recorded by mass-spectrometry. We note key differences to murine EECs, including hormones, sensory receptors, and transcription factors. Notably, several hormone-like molecules were identified. Inter-EEC communication is exemplified by secretin-induced GLP-1 secretion. Indeed, individual EEC subtypes carry receptors for various EEC hormones. This study provides a rich resource to study human EEC development and function.

Extracellular matrix hydrogel derived from decellularized tissues enables endodermal organoid culture

Organoids have extensive therapeutic potential and are increasingly opening up new avenues within regenerative medicine. However, their clinical application is greatly limited by the lack of effective GMP-compliant systems for organoid expansion in culture. Here, we envisage that the use of extracellular matrix (ECM) hydrogels derived from decellularized tissues (DT) can provide an environment capable of directing cell growth. These gels possess the biochemical signature of tissue-specific ECM and have the potential for clinical translation. Gels from decellularized porcine small intestine (SI) mucosa/submucosa enable formation and growth of endoderm-derived human organoids, such as gastric, hepatic, pancreatic, and SI. ECM gels can be used as a tool for direct human organoid derivation, for cell growth with a stable transcriptomic signature, and for in vivo organoid delivery. The development of these ECM-derived hydrogels opens up the potential for human organoids to be used clinically.

IFN-γ: The T cell’s license to kill stem cells in the inflamed intestine

IFN-γ produced by T cells directly induces intestinal stem cell death upon inflammation-induced intestinal injury (see the related Research Article byTakashimaet al.).

Establishment and characterization of a canine keratinocyte organoid culture system

BACKGROUND

Perturbations of epidermal and follicular homeostasis have been attributed to a variety of skin diseases affecting dogs. The availability of an in vitro system to investigate these diseases is important to understand underlying pathomechanisms.

OBJECTIVES

To establish an accurate and reliable in vitro 3D system of canine keratinocyte organoids to lay the basis for studying functional defects in interfollicular epidermis (IFE) and hair follicle (HF) morphogenesis, reconstitution and differentiation that lead to alopecic and epidermal diseases.

ANIMALS

Skin biopsies were obtained from freshly euthanized dogs of different breeds with no skin abnormalities.

METHODS

Cells derived from microdissected IFE and HFs were seeded in Matrigel and keratinocyte organoids were grown and characterized using immunohistochemistry, RT-qPCR and RNA sequencing.

RESULTS

Both organoid lines develop into a basal IFE-like cell type. Gene and protein expression analysis revealed high mRNA and protein levels of keratins 5 and 14, IFE differentiation markers and intercellular molecules. Key markers of HF stem cells were lacking. Withdrawal of growth factors resulted in upregulation of markers such as KRT16, Involucrin, KRT17 and SOX9, showing the potential of the organoids to develop towards more differentiated tissue.

CONCLUSION AND CLINICAL IMPORTANCE

Our 3D in vitro culture system provides the basis to explore epidermal function, to investigate the culture conditions necessary for the development of organoids with a HF signature and to address cutaneous disorders in dogs. However, for induction of HF signatures or hair growth, addition of different growth factors or co-culture with dermal papilla will be required.

Distinct Cellular Basis for Early Cardiac Arrhythmias, the Cardinal Manifestation of Arrhythmogenic Cardiomyopathy, and the Skin Phenotype of Cardiocutaneous Syndromes

RATIONALE

Arrhythmogenic cardiomyopathy is caused primarily by mutations in genes encoding desmosome proteins. Ventricular arrhythmias are the cardinal and typically early manifestations, whereas myocardial fibroadiposis is the pathological hallmark. Homozygous DSP (desmoplakin) and JUP (junction protein plakoglobin) mutations are responsible for a subset of patients with arrhythmogenic cardiomyopathy who exhibit cardiac arrhythmias and dysfunction, palmoplanter keratosis, and hair abnormalities (cardiocutaneous syndromes).

OBJECTIVE

To determine phenotypic consequences of deletion of Dsp in a subset of cells common to the heart and skin.

METHODS AND RESULTS

Expression of CSPG4 (chondroitin sulfate proteoglycan 4) was detected in epidermal keratinocytes and the cardiac conduction system. CSPG4^pos cells constituted ≈5.6±3.3% of the nonmyocyte cells in the mouse heart. Inducible postnatal deletion of Dsp under the transcriptional control of the Cspg4 locus led to ventricular arrhythmias, atrial fibrillation, atrioventricular conduction defects, and death by 4 months of age. Cardiac arrhythmias occurred early and in the absence of cardiac dysfunction and excess cardiac fibroadipocytes, as in human arrhythmogenic cardiomyopathy. The mice exhibited palmoplantar keratosis and progressive alopecia, leading to alopecia totalis, associated with accelerated proliferation and impaired terminal differentiation of keratinocytes. The phenotype is similar to human cardiocutaneous syndromes caused by homozygous mutations in DSP.

CONCLUSIONS

Deletion of Dsp under the transcriptional regulation of the CSPG4 locus led to lethal cardiac arrhythmias in the absence of cardiac dysfunction or fibroadiposis, palmoplantar keratosis, and alopecia, resembling the human cardiocutaneous syndromes. The findings offer a cellular basis for early cardiac arrhythmias in patients with arrhythmogenic cardiomyopathy and cardiocutaneous syndromes.

Organoids: Modeling Development and the Stem Cell Niche in a Dish

Organoids are three-dimensional in-vitro-grown cell clusters with near-native microanatomy that arise from self-organizing mammalian pluripotent or adult stem cells. Although monolayer stem cell cultures were established more than 40 years ago, organoid technology has recently emerged as an essential tool for both fundamental and biomedical research. For developmental biologists, organoids provide powerful means for ex vivo modeling of tissue morphogenesis and organogenesis. Here we discuss how organoid cultures of the intestine and other tissues have been established and how they are utilized as an in vitro model system for stem cell research and developmental biology.

Wnt/β-catenin signaling in adult mammalian epithelial stem cells

Adult stem cells self-renew and replenish differentiated cells in various organs and tissues throughout a mammal's life. Over the last 25 years an ever-growing body of knowledge has unraveled the essential regulation of adult mammalian epithelia by the canonical Wnt signaling with its key intracellular effector β-catenin. In this review, we discuss the principles of the signaling pathway and its role in adult epithelial stem cells of the intestine and skin during homeostasis and tumorigenesis. We further highlight the research that led to the identification of new stem cell markers and methods to study adult stem cells ex vivo.

Wounding induces dedifferentiation of epidermal Gata6+ cells and acquisition of stem cell properties

The epidermis is maintained by multiple stem cell populations whose progeny differentiate along diverse, and spatially distinct, lineages. Here we show that the transcription factor Gata6 controls the identity of the previously uncharacterized sebaceous duct (SD) lineage and identify the Gata6 downstream transcription factor network that specifies a lineage switch between sebocytes and SD cells. During wound healing differentiated Gata6⁺ cells migrate from the SD into the interfollicular epidermis and dedifferentiate, acquiring the ability to undergo long-term self-renewal and differentiate into a much wider range of epidermal lineages than in undamaged tissue. Our data not only demonstrate that the structural and functional complexity of the junctional zone is regulated by Gata6, but also reveal that dedifferentiation is a previously unrecognized property of post-mitotic, terminally differentiated cells that have lost contact with the basement membrane. This resolves the long-standing debate about the contribution of terminally differentiated cells to epidermal wound repair.

Replacement of Lost Lgr5-Positive Stem Cells through Plasticity of Their Enterocyte-Lineage Daughters

Intestinal crypts display robust regeneration upon injury. The relatively rare secretory precursors can replace lost stem cells, but it is unknown if the abundant enterocyte progenitors that express the Alkaline phosphate intestinal (Alpi) gene also have this capacity. We created an Alpi-IRES-CreERT2 (Alpi(CreER)) knockin allele for lineage tracing. Marked clones consist entirely of enterocytes and are all lost from villus tips within days. Genetic fate-mapping of Alpi(+) cells before or during targeted ablation of Lgr5-expressing stem cells generated numerous long-lived crypt-villus "ribbons," indicative of dedifferentiation of enterocyte precursors into Lgr5(+) stems. By single-cell analysis of dedifferentiating enterocytes, we observed the generation of Paneth-like cells and proliferative stem cells. We conclude that the highly proliferative, short-lived enterocyte precursors serve as a large reservoir of potential stem cells during crypt regeneration.

Compartmentalized Epidermal Activation of β-Catenin Differentially Affects Lineage Reprogramming and Underlies Tumor Heterogeneity

Wnt/β-catenin activation in adult epidermis can induce new hair follicle formation and tumor development. We used lineage tracing to uncover the relative contribution of different stem cell populations. LGR6(+) and LRIG1(+) stem cells contributed to ectopic hair follicles formed in the sebaceous gland upon β-catenin activation, whereas LGR5(+) cells did not. Lgr6, but not Lrig1 or Lgr5, was expressed in a subpopulation of interfollicular epidermal cells that were competent to form new hair follicles. Oncogenic β-catenin expression in LGR5(+) cells led to formation of pilomatricomas, while LRIG1(+) cells formed trichoadenomas and LGR6(+) cells formed dermatofibromas. Tumor formation was always accompanied by a local increase in dermal fibroblast density and transient extracellular matrix remodeling. However, each tumor had a distinct stromal signature in terms of immune cell infiltrate and expression of CD26 and CD44. We conclude that compartmentalization of epidermal stem cells underlies different responses to β-catenin and skin tumor heterogeneity.

The Androgen Receptor Antagonizes Wnt/β-Catenin Signaling in Epidermal Stem Cells

Activation of Wnt/β-catenin signaling in adult mouse epidermis leads to expansion of the stem cell compartment and redirects keratinocytes in the interfollicular epidermis and sebaceous glands (SGs) to differentiate along the hair follicle (HF) lineages. Here we demonstrate that during epidermal development and homeostasis there is reciprocal activation of the androgen receptor (AR) and β-catenin in cells of the HF bulb. AR activation reduced β-catenin-dependent transcription, blocked β-catenin-induced induction of HF growth, and prevented β-catenin-mediated conversion of SGs into HFs. Conversely, AR inhibition enhanced the effects of β-catenin activation, promoting HF proliferation and differentiation, culminating in the formation of benign HF tumors and a complete loss of SG identity. We conclude that AR signaling has a key role in epidermal stem cell fate selection by modulating responses to β-catenin in adult mouse skin.

Fate of Prominin-1 Expressing Dermal Papilla Cells during Homeostasis, Wound Healing and Wnt Activation

Prominin-1/CD133 (Prom1) is expressed by fibroblasts in the dermal papilla (DP) of the hair follicle (HF). By examining endogenous Prom1 expression and expression of LacZ in the skin of Prom1CreERLacZ (Prom1C-L) mice, in which a CreERT2-IRES-nuclear LacZ cassette is knocked into the first ATG codon of Prom1, we confirmed that Prom1 is expressed in the DP of all developing HFs and also by postnatal anagen follicles. To analyze the fate of Prom1+ DP cells, we crossed Prom1C-L mice with Rosa26-CAG flox/stop/flox tdTomato reporter mice and applied 4-hydroxytamoxifen (4OHT) to back skin at postnatal day (P) 1 and P2. We detected tdTomato+ cells in ~50% of DPs. The proportion of labeled cells per DP increased between P5 and P63, while the total number of cells per DP declined. Following full thickness wounding, there was no migration of tdTomato-labeled cells out of the DP. When β-catenin was activated in Prom1+ DP cells there was an increase in the size of anagen and telogen DP, but the proportion of tdTomato-labeled cells did not increase. We conclude that Prom1+ DP cells do not contribute to dermal repair but are nevertheless capable of regulating DP size via β-catenin-mediated intercellular communication.

Markers of epidermal stem cell subpopulations in adult mammalian skin

The epidermis is the outermost layer of mammalian skin and comprises a multilayered epithelium, the interfollicular epidermis, with associated hair follicles, sebaceous glands, and eccrine sweat glands. As in other epithelia, adult stem cells within the epidermis maintain tissue homeostasis and contribute to repair of tissue damage. The bulge of hair follicles, where DNA-label-retaining cells reside, was traditionally regarded as the sole epidermal stem cell compartment. However, in recent years multiple stem cell populations have been identified. In this review, we discuss the different stem cell compartments of adult murine and human epidermis, the markers that they express, and the assays that are used to characterize epidermal stem cell properties.

Sox2 modulates the function of two distinct cell lineages in mouse skin

In postnatal skin the transcription factor Sox2 is expressed in the dermal papilla (DP) of guard/awl/auchene hair follicles and by mechanosensory Merkel cells in the touch domes of guard hairs. To investigate the consequences of Sox2 ablation in skin we deleted Sox2 in DP cells via Blimp1Cre and in Merkel cells via K14Cre. Loss of Sox2 from the DP did not inhibit hair follicle morphogenesis or establishment of the dermis and hypodermis. However, Sox2 expression in the DP was necessary for postnatal maintenance of awl/auchene hair follicles. Deletion of Sox2 via K14Cre resulted in a decreased number of Merkel cells but had no effect on other epithelial compartments or on the dermis. The reduced number of Merkel cells did not affect the number or patterning of guard hairs, nerve density or the interaction of nerve cells with the touch domes. We conclude that Sox2 is a marker of two distinct lineages in the skin and regulates the number of differentiated cells in the case of the Merkel cell lineage and hair follicle type in the case of the DP.

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Sox2 is a marker of two distinct lineages in the skin.

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Sox2 is required for postnatal maintenance of awl/auchene hair follicles.

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Loss of Sox2 results in a reduction in Merkel cells.

Lineage tracing

Lineage tracing is the identification of all progeny of a single cell. Although its origins date back to developmental biology of invertebrates in the 19(th) century, lineage tracing is now an essential tool for studying stem cell properties in adult mammalian tissues. Lineage tracing provides a powerful means of understanding tissue development, homeostasis, and disease, especially when it is combined with experimental manipulation of signals regulating cell-fate decisions. Recently, the combination of inducible recombinases, multicolor reporter constructs, and live-cell imaging has provided unprecedented insights into stem cell biology. Here we discuss the different experimental strategies currently available for lineage tracing, their associated caveats, and new opportunities to integrate lineage tracing with the monitoring of intracellular signaling pathways.

Reprogramming adult dermis to a neonatal state through epidermal activation of β-catenin

Hair follicle formation depends on reciprocal epidermal-dermal interactions and occurs during skin development, but not in adult life. This suggests that the properties of dermal fibroblasts change during postnatal development. To examine this, we used a PdgfraEGFP mouse line to isolate GFP-positive fibroblasts from neonatal skin, adult telogen and anagen skin and adult skin in which ectopic hair follicles had been induced by transgenic epidermal activation of β-catenin (EF skin). We also isolated epidermal cells from each mouse. The gene expression profile of EF epidermis was most similar to that of anagen epidermis, consistent with activation of β-catenin signalling. By contrast, adult dermis with ectopic hair follicles more closely resembled neonatal dermis than adult telogen or anagen dermis. In particular, genes associated with mitosis were upregulated and extracellular matrix-associated genes were downregulated in neonatal and EF fibroblasts. We confirmed that sustained epidermal β-catenin activation stimulated fibroblasts to proliferate to reach the high cell density of neonatal skin. In addition, the extracellular matrix was comprehensively remodelled, with mature collagen being replaced by collagen subtypes normally present only in developing skin. The changes in proliferation and extracellular matrix composition originated from a specific subpopulation of fibroblasts located beneath the sebaceous gland. Our results show that adult dermis is an unexpectedly plastic tissue that can be reprogrammed to acquire the molecular, cellular and structural characteristics of neonatal dermis in response to cues from the overlying epidermis.

The Association between White Matter Lesions, Stroke and Activities of Daily Living - The MEMO Study on the KORA Platform Augsburg

Modern brain imaging methods have shown that vascular brain changes are a frequent finding in elderly individuals. The clinical relevance of subcortical white matter lesions is subject of debate, their impact on the functional status of those affected unclear. We assessed the prevalence of large white matter lesions and stroke, defined by Magnetic Resonance (MRI) criteria and by questionnaire reports, among 268 participants of the Memory and Morbidity in Augsburg Elderly Study, a 1997/98 follow up project of the MONICA survey S2 (1989/90), and evaluated the association of both types of brain changes with limitations in activities of daily living. The prevalence of large white matter lesions was 37 % (n = 69), that of any stroke or TIA 19.4 % (n = 52) and 12 % (n = 32) were affected by both brain changes. The latter group performed significantly worse in geriatric performance tests and had considerable impairments in their daily functioning. Vascular brain changes are very prevalent in older populations and have a measurable and considerable impact on functional capabilities of those affected.

Degenerative diseases of the spine. The role of myelography and myelo-CT

The role of myelography combined with myelo-CT in the evaluation of degenerative disease of the spine is judged differently. If MRI cannot be performed at a technically 'state of the art' standard, myelography combined with CT is the most informative link in the diagnostic chain, providing additional information to plain CT or technically inadequate MRI examinations, contributing to the final diagnosis and substantially directing the therapeutic strategy. For the preoperative evaluation of spinal stenoses, any compression of the nerve roots or the spinal cord by osseous spurs or soft tissue structures is best assessed after intrathecal administration of contrast medium.

[Value of computerized tomography and magnetic resonance tomography in psychiatric diagnosis]

This paper evaluates the role of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of psychiatric disorders according to the "International Classification of Diseases" (ICD-10). Indications for CT/MRI can be derived from ICD-10 for the identification or exclusion of defined cerebral lesions resp. for the etiology in organic disorders. Due to the lack of specific morphological findings, CT/MRI do not contribute to the classification of all other diagnoses. CT/ MRI can only exclude causal organic factors. However, ICD-10 provides only few guidelines for ruling out cerebral pathology (e.g. tumors in bulimic anorexia). Therefore, recommendations for routine CT/MRI-investigations for the exclusion of organic disorders are required and might be developed by the quality assurance. Application of CT or MRI: CT plays an important role in diagnostic imaging in routine as well as in emergency situations (haemorraghe, hamatoma, infaction, head injury, tumour, vascular malformation). MRI on the other hand, is more sensitive in the diagnosis of inflammatory diseases, skull base lesions, degenerative changes of the white matter and in the imaging of hydrocephalus and epilepsy.

Intrathymically expressed c-kit ligand (stem cell factor) is a major factor driving expansion of very immature thymocytes in vivo

To investigate the role of the receptor-type tyrosine kinase, c-kit and its ligand, stem cell factor (SCF) in T cell development, we analyzed c-kit (W/W) and SCF (SI/SI) deficient mice. We also engrafted wild-type or SCF-deficient fetal thymi onto wild-type recipient mice and analyzed the rate of proliferation by in vivo bromodeoxyuridine labeling. The results show that the most immature thymocyte compartment defined as CD3-CD4-CD8- is significantly reduced in SI/SI grafts and W/W thymi compared with wild-type counterparts. Also, the expansion rate of these immature thymocytes in SI/SI graft is reduced by -50%. These experiments provide direct evidence for an important role for c-kit-SCF interactions in expansion of very early thymocytes.

Laboratory scale production of monoclonal antibodies in a tumbling chamber

A simple device for laboratory scale production of monoclonal antibodies has been developed. Hybridomas were cultured in four individual dialysis tubes containing 40-50 ml medium with 10% foetal calf serum, surrounded by 1.5-2 litres supply medium without any serum supplement. Once placed on a roller the special design of the apparatus leads to an eccentric rotation, thus keeping the cells in a stable homogeneous suspension. The system is automatically gassed, and this makes long term cultivation possible. Several hybridomas were tested over a culture period of at least 3 weeks, with supply medium changes every 3-4 days. Cell densities of up to 2.5 x 10(7)/ml and antibody concentrations of 0.3-1.9 mg/ml after purification were obtained. Results with this in vitro system allow a complete renunciation of the established in vivo method. The so called 'tumbling chamber' apparatus is easy to handle and to sterilize, is economic and universally adaptable in any research laboratory.

Identification of pro-thymocytes in murine fetal blood: T lineage commitment can precede thymus colonization

Phenotype and commitment of thymus-colonizing precursors are unknown. Here we report the identification of T lineage-committed precursors (designated prothymocytes) in murine fetal blood at day 15.5 of development. Fetal blood pro-thymocytes are Thy-1+c-kit(low)CD3- in contrast to fetal blood-derived pluripotent hematopoietic progenitors which are Thy-1-c-kit+. Upon transfer into the thymus, fetal blood pro-thymocytes generate a single wave of CD4+CD8+ thymocytes and subsequently mature TCR alpha beta+ peripheral T cells. However, fetal blood pro-thymocytes lack multipotent progenitor potential since they fail to reconstitute B lymphocytes and myeloid and erythroid lineages. In contrast, T and B lymphocytes as well as myeloid and erythroid lineages are reconstituted from fetal blood-derived pluripotent progenitors. Pro-thymocytes are equally present in peripheral blood of athymic fetal mice, suggesting that this novel precursor population is T lineage-committed prior to thymus colonization and represents the earliest T lineage precursor identified.

[Depressive disorders after cerebral infarct. Relations to infarct site, brain atrophy and cognitive deficits]

We studied the effects of the localisation and size of ischemic brain infarcts and the influence of potential covariates (gender, age, time since infarction, physical handicap, cognitive impairment, aphasia, cortical atrophy and ventricular size) on 'post-stroke depression'. During an 18-months period all patients who underwent a CT-scan at the Central Institute of Mental Health and who had a single unilateral ischemic hemisphere infarct were initially included. Patients with severe aphasia or cognitive impairment who could not communicate well enough for the administration of depression rating scales were excluded. This led to a selection bias towards larger infarct sizes in the right hemisphere. In order to overcome this potentially critical selection artefact all patients with infarct sizes over 23 cm2 and/or with 'mini Mental State Scores' under 20 were excluded. The data from the remaining 30 patients (mean age 68 years; 15 male; 13 left hemisphere infarcts were used for the analysis. Their scores on the Hamilton depression rating scale, the Zung self rating depression scale and the von Zerssen clinical self-rating depression scale correlated significantly with one another (r greater than 0.73; p less than 0.001). Backward stepwise regression analysis carried out on the covariates mentioned above demonstrated a significant relationship only between cognitive impairment or cortical atrophy and a higher depression score.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomography in depression: association between ventricular size and psychopathology

The relationship between psychopathology and brain alterations, measured by computed tomography (CT), was investigated in 44 depressed patients. Comparisons of ventricle-brain ratio (VBR) between "endogenous" vs. "nonendogenous" subgroups, classified by six distinct diagnostic systems, revealed no significant differences. The VBR and the width of the third ventricle correlated significantly with scores on the Brief Psychiatric Rating Scale, the Global Assessment Scale, the Bech-Rafaelsen Melancholia Scale, the Rating for Emotional Blunting, and the Scale for the Assessment of Negative Symptoms, but not with scores on the Hamilton Rating Scale for Depression and the Hamilton Rating Scale for Anxiety. Item analyses of the Bech-Rafaelsen Melancholia Scale revealed that retardation-related items were most significantly correlated with ventricular size. The wider diameter of the third ventricle in psychotic patients was associated with higher scores on retardation in the psychotic subgroup, whereas the greater distances of both Sylvian fissures showed no relationship to psychomotor retardation. No significant correlations were found between CT values and anxiety, suicidal impulses, somatic complaints, and sleep disturbances.

[The risk of endocrine activation in interventional procedures on paraganglioma of the head and neck]

In the literature on paragangliomas or glomus tumors of the head and neck, the question rarely arises as to whether in endocrine inactive paragangliomas the tumor necrosis resulting from the embolization can release the stored substances. Based on 34 paragangliomas after surgical treatment, the angiographic and immunohistological characteristics of the paraganglionic, angiomatous and adenomatous tumors are presented. No catecholamine secretion occurred as a result of interventional or surgical treatment.

Sonography and computed tomography in the diagnosis of orbitocranial malformations and tumors

Standardized sonography and CT scanning have distinct advantages and disadvantages in the evaluation of patients with orbital diseases. Echography provides an efficient screening examination in patients presenting with signs and symptoms of orbital pathology. It allows the detection, localization, measurement and in almost 80% differentiation of orbital lesions. High resolution CT scanning gives an excellent topographic display of masses in the orbit. In visualization of intracranial causes of orbital processes and demonstration of changes in the posterior third of the orbit, in the orbital bones and the periorbital sinuses it is superior to ultrasonography.

Advantage of magnetic resonance imaging in the diagnosis of cerebral infections

18 patients with cerebral infections were investigated with a 1.5 Tesla-Magnetom. The results are compared to CT-findings obtained at the same time. In the majority of cases (n = 11) MR is superior to CT because it allows earlier detection of the disease, a more exact definition of the spread and a more detailed representation of complex inflammatory processes. MRI should rank first among all examination methods, especially in the determination of herpes simplex-encephalitis as it allows earlier detection and treatment of this disease.

Computed tomography in affective disorders. Part I. Ventricular and sulcal measurements

Sixty patients with affective illness were examined by computed tomography (CT) and compared to 60 age- and sex-matched controls. Using three different methods of measurement, no differences in ventricular brain ratio (VBR) between patients and controls could be detected. However, linear ventricular values of the frontal horns plus the bicaudate distance (Huckmann number) and the third ventricle were enlarged in the total group of patients. This was also found in subgroups of older, male, psychotic, unipolar, Dexamethasone Suppression Test (DST) positive, and lithium-treated patients when compared to individually matched controls. Younger, nonpsychotic, female, bipolar, DST-normal and non-lithium-treated patients did not differ from controls. The Huckmann number correlated with the duration of illness, as measured by the first episode and the number of episodes. The comparison between the subgroups of patients yielded higher linear and VBR values in older subjects, in men, and in psychotic subjects, whereas no differences were found in comparisons between unipolar versus bipolar, DST-positive versus DST-negative, and lithium-treated versus non-lithium-treated patients.

Computed tomography in affective disorders. Part II. Brain density

The attenuation values of brain density were investigated in 53 patients with affective disorder and 53 individually age- and sex-matched controls by computed tomography (CT). Asymmetry of density distribution, with higher values in most regions of the left hemisphere, was found in patients as well as in controls. Patients tended to display higher attenuation values than controls. In patients, an association between higher density of the parenchyma and smaller ventricular size was observed, but not in controls. Corresponding greater density in patients, compared to controls, was found in those subgroups (women, nonpsychotics, and bipolars) that did not differ in ventricle size from controls. Comparisons within subgroups of patients revealed lower attenuation values in psychotic than in nonpsychotic subjects, lower values in men than in women, lower values in lithium-treated than in non-lithium-treated patients, and lower values in unipolar than in bipolar patients. No differences were observed between older and younger patients or Dexamethasone Suppression Test (DST) normal versus DST-abnormal patients. No correlations between age and density were obtained in patients and controls.

Bilateral lesions of the putamina

13 cases of bilateral necrosis of the putamina in children and adults are reported. CT shows similar parenchymal defects, though clinical data reveal different histories, causes and circumstances of the damage. The relationship between CT findings and clinical symptoms is investigated, and the neurological dysfunctions resulting from symmetrical areas of necrosis in each putamen are discussed.