Enhancing pre-clinical research with simplified intestinal cell line models

Two-dimensional culture remains widely employed to determine the bioavailability of orally delivered drugs. To gain more knowledge about drug uptake mechanisms and risk assessment for the patient after oral drug admission, intestinal in vitro models demonstrating a closer similarity to the in vivo situation are needed. In particular, Caco-2 cell-based Transwell® models show advantages as they are reproducible, cost-efficient, and standardized. However, cellular complexity is impaired and cell function is strongly modified as important transporters in the apical membrane are missing. To overcome these limitations, primary organoid-based human small intestinal tissue models were developed recently but the application of these cultures in pre-clinical research still represents an enormous challenge, as culture setup is complex as well as time- and cost-intensive. To overcome these hurdles, we demonstrate the establishment of primary organoid-derived intestinal cell lines by immortalization. Besides exhibiting cellular diversity of the organoid, these immortalized cell lines enable a standardized and more cost-efficient culture. Further, our cell line-based Transwell®-like models display an organ-specific epithelial barrier integrity, ultrastructural features and representative transport functions. Altogether, our novel model systems are cost-efficient with close similarity to the in vivo situation, therefore favoring their use in bioavailability studies in the context of pre-clinical screenings.

Biomimetic Connection of Transcutaneous Implants with Skin

Bacterial infection is a crucial complication in implant restoration, in particular in permanent skin-penetrating implants. Therein, the resulting gap between transcutaneous implant and skin represents a permanent infection risk, limiting the field of application and the duration of application. To overcome this limitation, a tight physiological connection is required to achieve a biological and mechanical welding for a long-term stable closure including self-healing probabilities. This study describes a new approach, wherein the implant is connected covalently to a highly porous electrospun fleece featuring physiological dermal integration potential. The integrative potential of the scaffold is shown in vitro and confirmed in vivo, further demonstrating tissue integration by neovascularization, extracellular matrix formation, and prevention of encapsulation. To achieve a covalent connection between fleece and implant surface, self-initiated photografting and photopolymerization of hydroxyethylmethacrylate is combined with a new crosslinker (methacrylic acid coordinated titanium-oxo clusters) on proton-abstractable implant surfaces. For implant modification, the attached fleece is directed perpendicular from the implant surface into the surrounding dermal tissue. First in vitro skin implantations demonstrate the implants' dermal integration capability as well as wound closure potential on top of the fleece by epithelialization, establishing a bacteria-proof and self-healing connection of skin and transcutaneous implant.

Human isogenic cells of the neurovascular unit exert transcriptomic cell type-specific effects on a blood-brain barrier in vitro model of late-onset Alzheimer disease

BACKGROUND

The function of the blood-brain barrier (BBB) is impaired in late-onset Alzheimer disease (LOAD), but the associated molecular mechanisms, particularly with respect to the high-risk APOE4/4 genotype, are not well understood. For this purpose, we developed a multicellular isogenic model of the neurovascular unit (NVU) based on human induced pluripotent stem cells.

METHODS

The human NVU was modeled in vitro using isogenic co-cultures of astrocytes, brain capillary endothelial-like cells (BCECs), microglia-like cells, neural stem cells (NSCs), and pericytes. Physiological and pathophysiological properties were investigated as well as the influence of each single cell type on the characteristics and function of BCECs. The barriers established by BCECs were analyzed for specific gene transcription using high-throughput quantitative PCR.

RESULTS

Co-cultures were found to tighten the barrier of BCECs and alter its transcriptomic profile under both healthy and disease conditions. In vitro differentiation of brain cell types that constitute the NVU was not affected by the LOAD background. The supportive effect of NSCs on the barrier established by BCECs was diminished under LOAD conditions. Transcriptomes of LOAD BCECs were modulated by different brain cell types. NSCs were found to have the strongest effect on BCEC gene regulation and maintenance of the BBB. Co-cultures showed cell type-specific functional contributions to BBB integrity under healthy and LOAD conditions.

CONCLUSIONS

Cell type-dependent transcriptional effects on LOAD BCECs were identified. Our study suggests that different brain cell types of the NVU have unique roles in maintaining barrier integrity that vary under healthy and LOAD conditions. .

Challenges in Permeability Assessment for Oral Drug Product Development

Drug permeation across the intestinal epithelium is a prerequisite for successful oral drug delivery. The increased interest in oral administration of peptides, as well as poorly soluble and poorly permeable compounds such as drugs for targeted protein degradation, have made permeability a key parameter in oral drug product development. This review describes the various in vitro, in silico and in vivo methodologies that are applied to determine drug permeability in the human gastrointestinal tract and identifies how they are applied in the different stages of drug development. The various methods used to predict, estimate or measure permeability values, ranging from in silico and in vitro methods all the way to studies in animals and humans, are discussed with regard to their advantages, limitations and applications. A special focus is put on novel techniques such as computational approaches, gut-on-chip models and human tissue-based models, where significant progress has been made in the last few years. In addition, the impact of permeability estimations on PK predictions in PBPK modeling, the degree to which excipients can affect drug permeability in clinical studies and the requirements for colonic drug absorption are addressed.

Overcoming the blood-brain barrier? - prediction of blood-brain permeability of hydrophobically modified polyethylenimine polyplexes for siRNA delivery into the brain with in vitro and in vivo models

The blood-brain barrier (BBB) is a highly selective biological barrier that represents a major bottleneck in the treatment of all types of central nervous system (CNS) disorders. Small interfering RNA (siRNA) offers in principle a promising therapeutic approach, e.g., for brain tumors, by downregulating brain tumor-related genes and inhibiting tumor growth via RNA interference. In an effort to develop efficient siRNA nanocarriers for crossing the BBB, we utilized polyethyleneimine (PEI) polymers hydrophobically modified with either stearic-acid (SA) or dodecylacrylamide (DAA) subunits and evaluated their suitability for delivering siRNA across the BBB in in vitro and in vivo BBB models depending on their structure. Physicochemical characteristics of siRNA-polymer complexes (polyplexes (PXs)), e.g., particle size and surface charge, were measured by dynamic light scattering and laser Doppler anemometry, whereas siRNA condensation ability of polymers and polyplex stability was evaluated by spectrophotometric methods. The composition of the biomolecule corona that absorbs on polyplexes upon encountering physiological fluids was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. Cellular internalization abilities of PXs into brain endothelial cells (hCMEC/D3) was confirmed, and a BBB permeation assay using a human induced pluripotent stem cell (hiPSC)-derived BBB model revealed similar abilities to cross the BBB for all formulations under physiological conditions. However, biodistribution studies of radiolabeled PXs in mice were inconsistent with in vitro results as the detected amount of radiolabeled siRNA in the brain delivered with PEI PXs was higher compared to PEI-SA PXs. Taken together, PEI PXs were shown to be a suitable nanocarrier to deliver small amounts of siRNA across the BBB into the brain but more sophisticated human BBB models that better represent physiological conditions and biodistribution are required to provide highly predictive in vitro data for human CNS drug development in the future.

Locked Out: Phoenixin-14 Does Not Cross a Stem-Cell-Derived Blood-Brain Barrier Model

Phoenixin-14 is a recently discovered peptide regulating appetite. Interestingly, it is expressed in the gastrointestinal tract; however, its supposed receptor, GPR173, is predominantly found in hypothalamic areas. To date, it is unknown how peripherally secreted phoenixin-14 is able to reach its centrally located receptor. To investigate whether phoenixin is able to pass the blood-brain barrier, we used an in vitro mono-culture blood-brain barrier (BBB) model consisting of brain capillary-like endothelial cells derived from human induced-pluripotent stem cells (hiPSC-BCECs). The passage of 1 nMol and 10 nMol of phoenixin-14 via the mono-culture was measured after 30, 60, 90, 120, 150, 180, 210, and 240 min using a commercial ELISA kit. The permeability coefficients (PC) of 1 nMol and 10 nMol phoenixin-14 were 0.021 ± 0.003 and 0.044 ± 0.013 µm/min, respectively. In comparison with the PC of solutes known to cross the BBB in vivo, those of phoenixin-14 in both concentrations are very low. Here, we show that phoenixin-14 alone is not able to cross the BBB, suggesting that the effects of peripherally secreted phoenixin-14 depend on a co-transport mechanism at the BBB in vivo. The mechanisms responsible for phoenixin-14's orexigenic property along the gut-brain axis warrant further research.

A primary cell-based in vitro model of the human small intestine reveals host olfactomedin 4 induction in response to Salmonella Typhimurium infection

Infection research largely relies on classical cell culture or mouse models. Despite having delivered invaluable insights into host-pathogen interactions, both have limitations in translating mechanistic principles to human pathologies. Alternatives can be derived from modern Tissue Engineering approaches, allowing the reconstruction of functional tissue models in vitro. Here, we combined a biological extracellular matrix with primary tissue-derived enteroids to establish an in vitro model of the human small intestinal epithelium exhibiting in vivo-like characteristics. Using the foodborne pathogen Salmonella enterica serovar Typhimurium, we demonstrated the applicability of our model to enteric infection research in the human context. Infection assays coupled to spatio-temporal readouts recapitulated the established key steps of epithelial infection by this pathogen in our model. Besides, we detected the upregulation of olfactomedin 4 in infected cells, a hitherto unrecognized aspect of the host response to Salmonella infection. Together, this primary human small intestinal tissue model fills the gap between simplistic cell culture and animal models of infection, and shall prove valuable in uncovering human-specific features of host-pathogen interplay.

A Human Stem Cell-Derived Brain-Liver Chip for Assessing Blood-Brain-Barrier Permeation of Pharmaceutical Drugs

Significant advancements in the field of preclinical in vitro blood-brain barrier (BBB) models have been achieved in recent years, by developing monolayer-based culture systems towards complex multi-cellular assays. The coupling of those models with other relevant organoid systems to integrate the investigation of blood-brain barrier permeation in the larger picture of drug distribution and metabolization is still missing. Here, we report for the first time the combination of a human induced pluripotent stem cell (hiPSC)-derived blood-brain barrier model with a cortical brain and a liver spheroid model from the same donor in a closed microfluidic system (MPS). The two model compounds atenolol and propranolol were used to measure permeation at the blood–brain barrier and to assess metabolization. Both substances showed an in vivo-like permeation behavior and were metabolized in vitro. Therefore, the novel multi-organ system enabled not only the measurement of parent compound concentrations but also of metabolite distribution at the blood-brain barrier.

Establishment of the SIS scaffold-based 3D model of human peritoneum for studying the dissemination of ovarian cancer

Ovarian cancer is the second most common gynecological malignancy in women. More than 70% of the cases are diagnosed at the advanced stage, presenting as primary peritoneal metastasis, which results in a poor 5-year survival rate of around 40%. Mechanisms of peritoneal metastasis, including adhesion, migration, and invasion, are still not completely understood and therapeutic options are extremely limited. Therefore, there is a strong requirement for a 3D model mimicking the in vivo situation. In this study, we describe the establishment of a 3D tissue model of the human peritoneum based on decellularized porcine small intestinal submucosa (SIS) scaffold. The SIS scaffold was populated with human dermal fibroblasts, with LP-9 cells on the apical side representing the peritoneal mesothelium, while HUVEC cells on the basal side of the scaffold served to mimic the endothelial cell layer. Functional analyses of the transepithelial electrical resistance (TEER) and the FITC-dextran assay indicated the high barrier integrity of our model. The histological, immunohistochemical, and ultrastructural analyses showed the main characteristics of the site of adhesion. Initial experiments using the SKOV-3 cell line as representative for ovarian carcinoma demonstrated the usefulness of our models for studying tumor cell adhesion, as well as the effect of tumor cells on endothelial cell-to-cell contacts. Taken together, our data show that the novel peritoneal 3D tissue model is a promising tool for studying the peritoneal dissemination of ovarian cancer.

Protein Kinase D2 drives chylomicron-mediated lipid transport in the intestine and promotes obesity

Lipids are the most energy-dense components of the diet, and their overconsumption promotes obesity and diabetes. Dietary fat content has been linked to the lipid processing activity by the intestine and its overall capacity to absorb triglycerides (TG). However, the signaling cascades driving intestinal lipid absorption in response to elevated dietary fat are largely unknown. Here, we describe an unexpected role of the protein kinase D2 (PKD2) in lipid homeostasis. We demonstrate that PKD2 activity promotes chylomicron-mediated TG transfer in enterocytes. PKD2 increases chylomicron size to enhance the TG secretion on the basolateral side of the mouse and human enterocytes, which is associated with decreased abundance of APOA4. PKD2 activation in intestine also correlates positively with circulating TG in obese human patients. Importantly, deletion, inactivation, or inhibition of PKD2 ameliorates high-fat diet-induced obesity and diabetes and improves gut microbiota profile in mice. Taken together, our findings suggest that PKD2 represents a key signaling node promoting dietary fat absorption and may serve as an attractive target for the treatment of obesity.

Trajectory of extracellular fluid volume over time and subsequent risks of end-stage kidney disease and mortality in chronic kidney disease: a prospective cohort study

BACKGROUND

Extracellular fluid volume (ECF) is independently associated with chronic kidney disease (CKD) progression and mortality in patients with CKD, but the prognostic value of the trajectory of ECF over time beyond that of baseline value is unknown.

OBJECTIVES

To characterize ECF trajectory and evaluate its association with the risks of end-stage kidney disease (ESKD) and mortality.

METHODS

From the prospective tricentric NephroTest cohort, we included 1588 patients with baseline measured glomerular filtration rate (mGFR) ≥15 mL min^-1 /1.73 m² and ECF measurement. ECF and GFR were measured repeatedly using the distribution volume and clearance of ⁵¹ Cr-EDTA, respectively. ESKD and mortality were traced through record linkage with the national registries. Adjusted shared random-effect joint models were used to analyse the association between the trajectory of ECF over time and the two competing outcomes.

RESULTS

Patients were mean age 58.7 years, 66.7% men, mean mGFR of 43.6 ± 18.6 mL min^-1 /1.73 m² and mean ECF of 16.1 ± 3.6 L. Over a median follow-up of 5.3 [IQR: 3.0;7.4] years, ECF increased by 136 [95%CI 106;167] mL per year on average, whilst diuretic prescription and 24-hour urinary sodium excretion remained stable. ESKD occurred in 324 (20.4%) patients, and 185 (11.6%) patients died before ESKD. A higher current value of ECF was associated with increased hazards of ESKD (adjusted hazard ratio [aHR]: 1.12 [95%CI 1.06;1.18]; P < 0.001 per 1 L increase in ECF), and death before ESKD (aHR: 1.10 [95%CI 1.04;1.17]; P = 0.002).

CONCLUSIONS

The current value of ECF was associated with the risks of ESKD and mortality, independent of multiple potential confounders, including kidney function decline. This highlights the need for a close monitoring and adjustment of treatment to avoid fluid overload in CKD patients.

Triple co-culture and perfusion bioreactor for studying the interaction between Neisseria gonorrhoeae and neutrophils: A novel 3D tissue model for bacterial infection and immunity

Gonorrhea, a sexually transmitted disease caused by the bacteria Neisseria gonorrhoeae, is characterized by a large number of neutrophils recruited to the site of infection. Therefore, proper modeling of the N. gonorrhoeae interaction with neutrophils is very important for investigating and understanding the mechanisms that gonococci use to evade the immune response. We have used a combination of a unique human 3D tissue model together with a dynamic culture system to study neutrophil transmigration to the site of N. gonorrhoeae infection. The triple co-culture model consisted of epithelial cells (T84 human colorectal carcinoma cells), human primary dermal fibroblasts, and human umbilical vein endothelial cells on a biological scaffold (SIS). After the infection of the tissue model with N. gonorrhoeae, we introduced primary human neutrophils to the endothelial side of the model using a perfusion-based bioreactor system. By this approach, we were able to demonstrate the activation and transmigration of neutrophils across the 3D tissue model and their recruitment to the site of infection. In summary, the triple co-culture model supplemented by neutrophils represents a promising tool for investigating N. gonorrhoeae and other bacterial infections and interactions with the innate immunity cells under conditions closely resembling the native tissue environment.

Enteroids Generated from Patients with Severe Inflammation in Crohn's Disease Maintain Alterations of Junctional Proteins

BACKGROUND

The mechanisms underlying loss of intestinal epithelial barrier [IEB] function in Crohn's disease [CD] are poorly understood. We tested whether human enteroids generated from isolated intestinal crypts of CD patients serve as an appropriate in vitro model to analyse changes of IEB proteins observed in patients' specimens.

METHODS

Gut samples from CD patients and healthy individuals who underwent surgery were collected. Enteroids were generated from intestinal crypts and analyses of junctional proteins in comparison to full wall samples were performed.

RESULTS

Histopathology confirmed the presence of CD and the extent of inflammation in intestinal full wall sections. As revealed by immunostaining and Western blot analysis, profound changes in expression patterns of tight junction, adherens junction and desmosomal proteins were observed in full wall specimens when CD was present. Unexpectedly, when enteroids were generated from specimens of CD patients with severe inflammation, alterations of most tight junction proteins and the majority of changes in desmosomal proteins but not E-cadherin were maintained under culture conditions. Importantly, these changes were maintained without any additional stimulation of cytokines. Interestingly, qRT-PCR demonstrated that mRNA levels of junctional proteins were not different when enteroids from CD patients were compared to enteroids from healthy controls.

CONCLUSIONS

These data indicate that enteroids generated from patients with severe inflammation in CD maintain some characteristics of intestinal barrier protein changes on a post-transcriptional level. The enteroid in vitro model represents an appropriate tool to gain further cellular and molecular insights into the pathogenesis of barrier dysfunction in CD.

Matrix decoded - A pancreatic extracellular matrix with organ specific cues guiding human iPSC differentiation

The extracellular matrix represents a dynamic microenvironment regulating essential cell functions in vivo. Tissue engineering approaches aim to recreate the native niche in vitro using biological scaffolds generated by organ decellularization. So far, the organ specific origin of such scaffolds was less considered and potential consequences for in vitro cell culture remain largely elusive. Here, we show that organ specific cues of biological scaffolds affect cellular behavior. In detail, we report on the generation of a well-preserved pancreatic bioscaffold and introduce a scoring system allowing standardized inter-study quality assessment. Using multiple analysis tools for in-depth-characterization of the biological scaffold, we reveal unique compositional, physico-structural, and biophysical properties. Finally, we prove the functional relevance of the biological origin by demonstrating a regulatory effect of the matrix on multi-lineage differentiation of human induced pluripotent stem cells emphasizing the significance of matrix specificity for cellular behavior in artificial microenvironments.

A three-dimensional intestinal tissue model reveals factors and small regulatory RNAs important for colonization with Campylobacter jejuni

The Gram-negative Epsilonproteobacterium Campylobacter jejuni is currently the most prevalent bacterial foodborne pathogen. Like for many other human pathogens, infection studies with C. jejuni mainly employ artificial animal or cell culture models that can be limited in their ability to reflect the in-vivo environment within the human host. Here, we report the development and application of a human three-dimensional (3D) infection model based on tissue engineering to study host-pathogen interactions. Our intestinal 3D tissue model is built on a decellularized extracellular matrix scaffold, which is reseeded with human Caco-2 cells. Dynamic culture conditions enable the formation of a polarized mucosal epithelial barrier reminiscent of the 3D microarchitecture of the human small intestine. Infection with C. jejuni demonstrates that the 3D tissue model can reveal isolate-dependent colonization and barrier disruption phenotypes accompanied by perturbed localization of cell-cell junctions. Pathogenesis-related phenotypes of C. jejuni mutant strains in the 3D model deviated from those obtained with 2D-monolayers, but recapitulated phenotypes previously observed in animal models. Moreover, we demonstrate the involvement of a small regulatory RNA pair, CJnc180/190, during infections and observe different phenotypes of CJnc180/190 mutant strains in 2D vs. 3D infection models. Hereby, the CJnc190 sRNA exerts its pathogenic influence, at least in part, via repression of PtmG, which is involved in flagellin modification. Our results suggest that the Caco-2 cell-based 3D tissue model is a valuable and biologically relevant tool between in-vitro and in-vivo infection models to study virulence of C. jejuni and other gastrointestinal pathogens.

Enteric pathogens have evolved numerous strategies to successfully colonize and persist in the human gastrointestinal tract. However, especially for the research of virulence mechanisms of human pathogens, often only limited infection models are available. Here, we have applied and further advanced a tissue-engineered human intestinal tissue model based on an extracellular matrix scaffold reseeded with human cells that can faithfully mimic pathogenesis-determining processes of the zoonotic pathogen Campylobacter jejuni. Our three-dimensional (3D) intestinal infection model allows for the assessment of epithelial barrier function during infection as well as for the quantification of bacterial adherence, internalization, and transmigration. Investigation of C. jejuni mutant strains in our 3D tissue model revealed isolate-specific infection phenotypes, in-vivo relevant infection outcomes, and uncovered the involvement of a small RNA pair during C. jejuni pathogenesis. Overall, our results demonstrate the power of tissue-engineered models for studying host-pathogen interactions, and our model will also be helpful to investigate other gastrointestinal pathogens.

Investigation of Cellular Function and DNA Integrity during 2D in vitro Culture of Human Salivary Gland Epithelial Cells

In vitro culture of human salivary gland epithelial cells (SGEC) is still a challenge. A high quantity and quality of cells are needed for the cultivation of 3D matrices. Furthermore, it is known that DNA damage is supposed to be an important factor involved in carcinogenesis. This study investigates cellular function and DNA integrity of human SGEC during 3 passage steps in 2 groups (group 1: n = 10; group 2: n = 9). Cellular function was analyzed by immunofluorescence, transmission electron microscopy (TEM), and quantitative real-time polymerase chain reaction (qPCR). DNA integrity was tested via the comet assay. Immunohistochemistry and qPCR results showed stable α-amylase and pan-cytokeratin levels; TEM revealed functional cells; and no significant DNA damage could be detected in the comet assay during 3 culture steps. The study shows that not only at cellular but also at DNA level human SGEC can be safely quantified over 3 passages for preclinical tissue engineering without loss of differentiation and function.

Characterization of Biostable Atomic Layer Deposited (ALD) Multilayer Passivation Coatings for Active Implants

The next generation of flexible, electrically active implants, such as brain implants or retina chips require a flexible, biostable as well as biocompatible passivation, ensuring a degradation-free usage for long time periods on the order of several years. Until today, these passivations are prepared mostly by polyimides or parylene, both of which are water vapor permeable to a certain degree. To remedy this deficiency, Atomic Layer Deposited (ALD) thin films are characterized regarding their electrical passivating features under conditions of accelerated aging, such as elevated temperatures in a liquid environment. The initial electrical passivation by various ALD deposited multilayers, combining alternating thin Al₂O₃ and TiO₂ layers is the goal of this research as well as the stability of these layers under induced degradation. Such layers, in combination with a parylene passivation, would ensure a water vapor impermeable and biocompatible coating.

Postnatal human enteric neurospheres show a remarkable molecular complexity

BACKGROUND

The enteric nervous system (ENS), a complex network of neurons and glial cells, coordinates major gastrointestinal functions. Impaired development or secondary aberrations cause severe enteric neuropathies. Neural crest-derived stem cells as well as enteric neuronal progenitor cells, which form enteric neurospheres, represent a promising tool to unravel molecular pathomechanisms and to develop novel therapy options. However, so far little is known about the detailed cellular composition and the proportional distribution of enteric neurospheres. Comprehensive knowledge will not only be essential for basic research but also for prospective cell replacement therapies to restore or to improve enteric neuronal dysfunction.

METHODS

Human enteric neurospheres were generated from three individuals with varying age. For detailed molecular characterization, nCounter target gene expression analyses focusing on stem, progenitor, neuronal, glial, muscular, and epithelial cell markers were performed. Corresponding archived paraffin-embedded individuals' specimens were analyzed accordingly.

KEY RESULTS

Our data revealed a remarkable molecular complexity of enteric neurospheres and archived specimens. Amongst the expression of multipotent stem cell, progenitor cell, neuronal, glial, muscle and epithelial cell markers, moderate levels for the pluripotency marker POU5F1 were observed. Furthermore, besides the interindividual variability, we identified highly distinct intraindividual expression profiles.

CONCLUSIONS & INFERENCES

Our results emphasize the assessment of molecular signatures to be essential for standardized use, optimization of experimental approaches, and elimination of potential risk factors, as the formation of tumors. Our study pipeline may serve as a blueprint implemented into the characterization procedure of enteric neurospheres for various future applications.

Neurotrophic factor GDNF regulates intestinal barrier function in inflammatory bowel disease

Impaired intestinal epithelial barrier (IEB) function with loss of desmosomal junctional protein desmoglein 2 (DSG2) is a hallmark in the pathogenesis of inflammatory bowel disease (IBD). While previous studies have reported that glial cell line-derived neurotrophic factor (GDNF) promotes IEB function, the mechanisms are poorly understood. We hypothesized that GDNF is involved in the loss of DSG2, resulting in impaired IEB function as seen in IBD. In the inflamed intestine of patients with IBD, there was a decrease in GDNF concentrations accompanied by a loss of DSG2, changes of the intermediate filament system, and increased phosphorylation of p38 MAPK and cytokeratins. DSG2-deficient and RET-deficient Caco2 cells revealed that GDNF specifically recruits DSG2 to the cell borders, resulting in increased DSG2-mediated intercellular adhesion via the RET receptor. Challenge of Caco2 cells and enteroids with proinflammatory cytokines as well as dextran sulfate sodium-induced (DSS-induced) colitis in C57Bl/6 mice led to impaired IEB function with reduced DSG2 mediated by p38 MAPK-dependent phosphorylation of cytokeratins. GDNF blocked all inflammation-induced changes in the IEB. GDNF attenuates inflammation-induced impairment of IEB function caused by the loss of DSG2 through p38 MAPK-dependent phosphorylation of cytokeratin. The reduced GDNF in patients with IBD indicates a disease-relevant contribution to the development of IEB dysfunction.

Induced Pluripotent Stem Cell-Derived Brain Endothelial Cells as a Cellular Model to Study Neisseria meningitidis Infection

Meningococcal meningitis is a severe central nervous system infection that occurs when Neisseria meningitidis (Nm) penetrates brain endothelial cells (BECs) of the meningeal blood-cerebrospinal fluid barrier. As a human-specific pathogen, in vivo models are greatly limited and pose a significant challenge. In vitro cell models have been developed, however, most lack critical BEC phenotypes limiting their usefulness. Human BECs generated from induced pluripotent stem cells (iPSCs) retain BEC properties and offer the prospect of modeling the human-specific Nm interaction with BECs. Here, we exploit iPSC-BECs as a novel cellular model to study Nm host-pathogen interactions, and provide an overview of host responses to Nm infection. Using iPSC-BECs, we first confirmed that multiple Nm strains and mutants follow similar phenotypes to previously described models. The recruitment of the recently published pilus adhesin receptor CD147 underneath meningococcal microcolonies could be verified in iPSC-BECs. Nm was also observed to significantly increase the expression of pro-inflammatory and neutrophil-specific chemokines IL6, CXCL1, CXCL2, CXCL8, and CCL20, and the secretion of IFN-γ and RANTES. For the first time, we directly observe that Nm disrupts the three tight junction proteins ZO-1, Occludin, and Claudin-5, which become frayed and/or discontinuous in BECs upon Nm challenge. In accordance with tight junction loss, a sharp loss in trans-endothelial electrical resistance, and an increase in sodium fluorescein permeability and in bacterial transmigration, was observed. Finally, we established RNA-Seq of sorted, infected iPSC-BECs, providing expression data of Nm-responsive host genes. Altogether, this model provides novel insights into Nm pathogenesis, including an impact of Nm on barrier properties and tight junction complexes, and suggests that the paracellular route may contribute to Nm traversal of BECs.

Human Pluripotent Stem Cell-Derived Multipotent Vascular Progenitors of the Mesothelium Lineage Have Utility in Tissue Engineering and Repair

In this report we describe a human pluripotent stem cell-derived vascular progenitor (MesoT) cell of the mesothelium lineage. MesoT cells are multipotent and generate smooth muscle cells, endothelial cells, and pericytes and self-assemble into vessel-like networks in vitro. MesoT cells transplanted into mechanically damaged neonatal mouse heart migrate into the injured tissue and contribute to nascent coronary vessels in the repair zone. When seeded onto decellularized vascular scaffolds, MesoT cells differentiate into the major vascular lineages and self-assemble into vasculature capable of supporting peripheral blood flow following transplantation. These findings demonstrate in vivo functionality and the potential utility of MesoT cells in vascular engineering applications.

Altered pancreatic islet morphology and function in SGLT1 knockout mice on a glucose-deficient, fat-enriched diet

OBJECTIVES

Glycemic control by medical treatment represents one therapeutic strategy for diabetic patients. The Na+-d-glucose cotransporter 1 (SGLT1) is currently of high interest in this context. SGLT1 is known to mediate glucose absorption and incretin secretion in the small intestine. Recently, inhibition of SGLT1 function was shown to improve postprandial hyperglycemia. In view of the lately demonstrated SGLT1 expression in pancreatic islets, we investigated if loss of SGLT1 affects islet morphology and function.

METHODS

Effects associated with the loss of SGLT1 on pancreatic islet (cyto) morphology and function were investigated by analyzing islets of a SGLT1 knockout mouse model, that were fed a glucose-deficient, fat-enriched diet (SGLT1^-/--GDFE) to circumvent the glucose-galactose malabsorption syndrome. To distinguish diet- and Sglt1^-/--dependent effects, wildtype mice on either standard chow (WT-SC) or the glucose-free, fat-enriched diet (WT-GDFE) were used as controls. Feeding a glucose-deficient, fat-enriched diet further required the analysis of intestinal SGLT1 expression and function under diet-conditions.

RESULTS

Consistent with literature, our data provide evidence that small intestinal SGLT1 mRNA expression and function is regulated by nutrition. In contrast, pancreatic SGLT1 mRNA levels were not affected by the applied diet, suggesting different regulatory mechanisms for SGLT1 in diverse tissues. Morphological changes such as increased islet sizes and cell numbers associated with changes in proliferation and apoptosis and alterations of the β- and α-cell population are specifically observed for pancreatic islets of SGLT1^-/--GDFE mice. Glucose stimulation revealed no insulin response in SGLT1^-/--GDFE mice while WT-GDFE mice displayed only a minor increase of blood insulin. Irregular glucagon responses were observed for both, SGLT1^-/--GDFE and WT-GDFE mice. Further, both animal groups showed a sustained release of GLP-1 compared to WT-SC controls.

CONCLUSION

Loss or impairment of SGLT1 results in abnormal pancreatic islet (cyto)morphology and disturbed islet function regarding the insulin or glucagon release capacity from β- or α-cells, respectively. Consequently, our findings propose a new, additional role for SGLT1 maintaining proper islet structure and function.

Impact of sex and glucose-lowering treatments on hypoglycaemic symptoms in people with type 2 diabetes and chronic kidney disease. The French Chronic Kidney Disease - Renal Epidemiology and Information Network (CKD-REIN) Study

AIM

To describe current practices of glucose-lowering treatments in people with diabetes and chronic kidney disease (CKD), the associated glucose control and hypoglycaemic symptoms, with an emphasis on sex differences.

METHODS

Among the 3033 patients with CKD stages 3-5 recruited into the French CKD-REIN study, 645 men and 288 women had type 2 diabetes and were treated by glucose-lowering drugs.

RESULTS

Overall, 31% were treated only with insulin, 28% with combinations of insulin and another drug, 42% with non-insulin glucose-lowering drugs. In CKD stage 3, 40% of patients used metformin, 12% at stages 4&5, similar for men and women; in CKD stage 3, 53% used insulin, similar for men and women, but at stages 4&5, 59% of men and 77% of women used insulin. Patients were reasonably well controlled, with a median HbA1c of 7.1% (54mmol/mol) in men, 7.4% (57mmol/mol) in women (P=0.0003). Hypoglycaemic symptoms were reported by 40% of men and 59% of women; they were not associated with the estimated glomerular filtration rate, nor with albuminuria or with HbA1c in multivariable analyses, but they were more frequent in people treated with insulin, particularly with fast-acting and pre-mixed insulins.

CONCLUSION

Glucose-lowering treatment, HbA1c and hypoglycaemic symptoms were sex dependent. Metformin use was similar in men and women, but unexpectedly low in CKD stage 3; its use could be encouraged rather than resorting to insulin. Hypoglycaemic symptoms were frequent and need to be more closely monitored, with appropriate patient-education, especially in women.

Nanoparticle-Based Mucosal Vaccines Targeting Tumor-Associated Antigens to Human Dendritic Cells

The induction of effective T cell-mediated immune responses is the main objective of vaccination against cancer. T cell responses are initiated by dendritic cells (DCs) as the most potent antigen-presenting cells. Designing vaccines for efficient delivery of tumor antigens to these cells in immunogenic fashion is, therefore, a major task in tumor immunology. In this human-based in vitro study we investigated the suitability of different polymeric nanoparticles (NPs) for delivering the tumor-associated antigen Her2/neu to DCs for induction of T cell responses by mucosal vaccination. The natural polymer chitosan and novel functionalized PLGA-based polymers were used for NP production. All NPs were efficiently taken up by DCs. Her2/neu delivered by NPs was more efficiently processed and presented by DCs than the soluble protein and induced more vigorous CD4+ and CD8+ T cell proliferation, and cytotoxic T cells. Testing the suitability of this platform for mucosal vaccination, NPs were applied to the apical side of an intestinal epithelium model and found to be efficiently transported across the epithelial layer to become available to basolateral DCs. Thus, chitosan and PLGA-based NPs are efficient carriers for delivery of antigens to DCs for induction of T cell-based immunity, and suitable for mucosal vaccine formulations.

Evaluation of a Miniaturized Biologically Vascularized Scaffold in vitro and in vivo

In tissue engineering, the generation and functional maintenance of dense voluminous tissues is mainly restricted due to insufficient nutrient supply. Larger three-dimensional constructs, which exceed the nutrient diffusion limit become necrotic and/or apoptotic in long-term culture if not provided with an appropriate vascularization. Here, we established protocols for the generation of a pre-vascularized biological scaffold with intact arterio-venous capillary loops from rat intestine, which is decellularized under preservation of the feeding and draining vascular tree. Vessel integrity was proven by marker expression, media/blood reflow and endothelial LDL uptake. In vitro maintenance persisted up to 7 weeks in a bioreactor system allowing a stepwise reconstruction of fully vascularized human tissues and successful in vivo implantation for up to 4 weeks, although with time-dependent decrease of cell viability. The vascularization of the construct lead to a 1.5× increase in cellular drug release compared to a conventional static culture in vitro. For the first time, we performed proof-of-concept studies demonstrating that 3D tissues can be maintained within a miniaturized vascularized scaffold in vitro and successfully implanted after re-anastomosis to the intrinsic blood circulation in vivo. We hypothesize that this technology could serve as a powerful platform technology in tissue engineering and regenerative medicine.

The OsteoLaus Cohort Study

Eine indirekte Beurteilung der Mikroarchitektur (MA) ist in der täglichen Praxis anhand des TBS (Trabecular Bone Score) näherungsweise möglich. Das Ziel der OsteoLaus-Kohorte besteht darin, klinische Risikofaktoren und Informationen aus der DXA (Knochenmineraldichte [BMD], TBS und Wirbelkörperfrakturerkennung [VFA]) zu kombinieren, um Frauen mit hohem Frakturrisiko leichter zu erkennen. Wir nahmen 631 Frauen im mittleren Alter von 67,4 ± 6,7 J. und mit einem BMI von 26,1 ± 4,6 auf. Es bestand eine schwache Korrelation zwischen BMD und Zentrums-gematchtem TBS (r2 = 0,16). Die Prävalenz von Wirbelfrakturen (VFx) Grad 2/3, größeren osteoporotischen (OP) Frakturen und allen OP-Frakturen betrug 8,4 %, 17,0 % bzw. 26,0 %. Alters- und BMI-adjustierte OR (nach abnehmender SD) lagen bei 1,8 (1,2–2,5), 1,6 (1,2–2,1) bzw. 1,3 (1,1–1,6) für BMD und 2,0 (1,4–3,0), 1,9 (1,4–2,5) bzw. 1,4 (1,1–1,7) für TBS. Die TBS OR (nach abnehmender SD), adjustiert nach Alter, BMI und Wirbelsäulen-BMD, für VFx Grad 2/3, größere und alle OP-Frakturen betrugen 1,7 (1,1–2,7), 1,6 (1,2–2,2) bzw. 1,3 (1,0–1,7). Nur 35 bis 44 % der Frauen mit OP-Frakturen hatten eine BMD <−2,5 SD oder einen TBS < 1.200. Durch Kombination eines BMD < −2,5 SD oder TBS < 1,200 werden 54 bis 60 % der Frauen mit OP-Fraktur erkannt. Somit können wir anhand von VFA, BMD und TBS aus einem einfachen und strahlenarmen Röntgenverfahren, der DXA, Zusatzinformationen gewinnen, die für den Patienten im Praxisalltag von Nutzen sind.

Mucus Detachment by Host Metalloprotease Meprin β Requires Shedding of Its Inactive Pro-form, which Is Abrogated by the Pathogenic Protease RgpB

The host metalloprotease meprin β is required for mucin 2 (MUC2) cleavage, which drives intestinal mucus detachment and prevents bacterial overgrowth. To gain access to the cleavage site in MUC2, meprin β must be proteolytically shed from epithelial cells. Hence, regulation of meprin β shedding and activation is important for physiological and pathophysiological conditions. Here, we demonstrate that meprin β activation and shedding are mutually exclusive events. Employing ex vivo small intestinal organoid and cell culture experiments, we found that ADAM-mediated shedding is restricted to the inactive pro-form of meprin β and is completely inhibited upon its conversion to the active form at the cell surface. This strict regulation of meprin β activity can be overridden by pathogens, as demonstrated for the bacterial protease Arg-gingipain (RgpB). This secreted cysteine protease potently converts membrane-bound meprin β into its active form, impairing meprin β shedding and its function as a mucus-detaching protease.

Evaluation of Decellularized Porcine Jejunum as a Matrix for Lacrimal Gland Reconstruction In Vitro for Treatment of Dry Eye Syndrome

Purpose

Dry eye syndrome (DES) can cause blindness in severe cases, but mainly palliative treatments exist. A tissue-engineered lacrimal gland (LG) could provide a curative treatment. We aimed to evaluate decellularized porcine jejunum (SIS-Muc) as a scaffold for porcine LG epithelial cells.

Methods

To evaluate SIS-Muc as a potential scaffold, basement membrane proteins in SIS-Muc and native LG were compared (immunohistochemistry [IHC]). Porcine LG epithelial cells cultured on plastic were characterized (immunocytochemistry), and their culture supernatant was compared with porcine tears (proteomics). Epithelial cells were then seeded onto SIS-Muc in either a static (cell crown) or dynamic culture (within a perfusion chamber) and metabolic (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and secretory capacities (β-hexosaminidase assay), protein expression (IHC), and ultrastructure transmission electron microscopy (TEM) compared in each.

Results

Collagen IV and laminin were found in both native LG and SIS-Muc. When cultured on plastic, LG epithelial cells expressed pan-cytokeratin, Rab3D, HexA, and produced mucins, but lysozyme and lactoferrin expression was nearly absent. Some porcine tear proteins (lipocalin-2 and lactoferrin) were found in LG epithelial cell culture supernatants. When LG cells were cultured on SIS-Muc, metabolic and β-hexosaminidase activities were greater in dynamic cultures than static cultures (P < 0.05). In both static and dynamic cultures, cells expressed pan-cytokeratin, Rab3D, lysozyme, and lactoferrin and produced mucins, and TEM revealed cell polarization at the apical surface and cell-cell and cell-scaffold contacts.

Conclusions

SIS-Muc is a suitable scaffold for LG cell expansion and may be useful toward reconstruction of LG tissue to provide a curative treatment for DES. Dynamic culture enhances cell metabolic and functional activities.

miR-16 and miR-103 impact 5-HT4 receptor signalling and correlate with symptom profile in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a gut-brain disorder involving alterations in intestinal sensitivity and motility. Serotonin 5-HT4 receptors are promising candidates in IBS pathophysiology since they regulate gut motor function and stool consistency, and targeted 5-HT4R selective drug intervention has been proven beneficial in subgroups of patients. We identified a single nucleotide polymorphism (SNP) (rs201253747) c.*61 T > C within the 5-HT4 receptor gene HTR4 to be predominantly present in diarrhoea-IBS patients (IBS-D). It affects a binding site for the miR-16 family and miR-103/miR-107 within the isoforms HTR4b/i and putatively impairs HTR4 expression. Subsequent miRNA-profiling revealed downregulation of miR-16 and miR-103 in the jejunum of IBS-D patients correlating with symptoms. In vitro assays confirmed expression regulation via three 3'UTR binding sites. The novel isoform HTR4b_2 lacking two of the three miRNA binding sites escapes miR-16/103/107 regulation in SNP carriers. We provide the first evidence that HTR4 expression is fine-tuned by miRNAs, and that this regulation is impaired either by the SNP c.*61 T > C or by diminished levels of miR-16 and miR-103 suggesting that HTR4 might be involved in the development of IBS-D.

Development of Human Salivary Gland-Like Tissue In Vitro

The loss of salivary gland function caused by radiation therapy of the head and neck is a serious condition and it affects a patient's quality of life. The current lack of effective therapies demands new options to be explored. This study tested whether human salivary gland epithelial cells (SGECs) could be successfully cultured on a decellularized porcine gut matrix (SIS-muc) in both mono- and coculture with microvascular endothelial cells (mvECs). By performing immunofluorescence imaging, transmission as well as scanning electron microscopy (SEM), quantitative polymerase chain reaction (qPCR), and an amylase enzyme assay, it was investigated as to what extent the three-dimensional (3D)-cultured cells could maintain their molecular differentiation and the production of working α-amylase (α-AMY) compared with two-dimensional (2D) culture. In both 3D mono- and coculture, SGECs were successfully cultured and formed acinar-like structures. Those findings were confirmed by SEM imaging. Immunofluorescence imaging revealed that 3D-cultured cells expressed α-AMY, Claudin-1 (CL-1), and water channel protein aquaporin-5 (AQP-5). Two-dimensional-cultured cells only were positive for α-AMY. Real time (RT)-qPCR analysis showed that α-AMY relative gene expression was higher in both 3D mono- and coculture than in 2D culture. In α-AMY enzyme assay, cocultured SGECs showed about 25 times increased enzyme activity compared with 2D-cultured cells. In conclusion, the SIS-muc combined with endothelial coculture seems a suitable culture setting for the tissue engineering of functional human salivary gland tissue.