Altered subcellular localization of heat shock protein 90 is associated with impaired expression of the aryl hydrocarbon receptor pathway in dogs

Urine-based Detection of Congenital Portosystemic Shunt in C57BL/6 Mice

Sporadic occurrence of congenital portosystemic shunt (PSS) at a rate of ∼1 out of 10 among C57BL/6 J mice, which are widely used in biomedical research, results in aberrancies in serologic, metabolic, and physiologic parameters. Therefore, mice with PSS should be identified as outliers in research. Accordingly, we sought methods to, reliably and efficiently, identify PSS mice. Serum total bile acids ≥ 40 µm is a bona fide biomarker of PSS in mice but utility of this biomarker is limited by its cost and invasiveness, particularly if large numbers of mice are to be screened. This led us to investigate if assay of urine might serve as a simple, inexpensive, noninvasive means of PSS diagnosis. Metabolome profiling uncovered that Krebs cycle intermediates, that is, citrate, α-ketoglutarate, and fumarate, were strikingly and distinctly elevated in the urine of PSS mice. We leveraged the iron-chelating and pH-lowering properties of such metabolites as the basis for 3 urine-based PSS screening tests: urinary iron-chelation assay, pH strip test, and phenol red assay. Our findings demonstrate the feasibility of using these colorimetric assays, whereby their readout can be assessed by direct observation, to diagnose PSS in an inexpensive, rapid, and noninvasive manner. Application of our urinary PSS screening protocols can aid biomedical research by enabling stratification of PSS mice, which, at present, likely confound numerous ongoing studies.

Bioprinting of Human Liver-Derived Epithelial Organoids for Toxicity Studies

There is a need for long-lived hepatic in vitro models to better predict drug induced liver injury (DILI). Human liver-derived epithelial organoids are a promising cell source for advanced in vitro models. Here, organoid technology is combined with biofabrication techniques, which holds great potential for the design of in vitro models with complex and customizable architectures. Here, porous constructs with human hepatocyte-like cells derived from organoids are generated using extrusion-based printing technology. Cell viability of bioprinted organoids remains stable for up to ten days (88-107% cell viability compared to the day of printing). The expression of hepatic markers, transporters, and phase I enzymes increased compared to undifferentiated controls, and is comparable to non-printed controls. Exposure to acetaminophen, a well-known hepatotoxic compound, decreases cell viability of bioprinted liver organoids to 21-51% (p < 0.05) compared to the start of exposure, and elevated levels of damage marker miR-122 are observed in the culture medium, indicating the potential use of the bioprinted constructs for toxicity testing. In conclusion, human liver-derived epithelial organoids can be combined with a biofabrication approach, thereby paving the way to create perfusable, complex constructs which can be used as toxicology- and disease-models.

Reduced FXR Target Gene Expression in Copper-Laden Livers of COMMD1-Deficient Dogs

Wilson’s disease (WD), an autosomal recessive disorder, results in copper accumulation in the liver as a consequence of mutations in the gene ATPase copper transporting beta (ATP7B). The disease is characterized by chronic hepatitis, eventually resulting in liver cirrhosis. Recent studies have shown that dysregulation of nuclear receptors (NR) by high hepatic copper levels is an important event in the pathogenesis of liver disease in WD. Intracellular trafficking of ATP7B is mediated by COMMD1 and, in Bedlington terriers, a mutation in the COMMD1 gene results in high hepatic copper levels. Here, we demonstrate a reduced Farnesoid X nuclear receptor (FXR)-activity in liver biopsies of COMMD1-deficient dogs with copper toxicosis, a unique large animal model of WD. FXR-induced target genes, small heterodimer partner (SHP), and apolipoprotein E (ApoE) were down-regulated in liver samples from COMMD1-deficient dogs with hepatic copper accumulation. In contrast, the relative mRNA levels of the two CYP-enzymes (reduced by FXR activity) was similar in both groups. These data are in line with the previously observed reduced FXR activity in livers of ATP7B−/− mice and WD patients. Therefore, these data further corroborate on the importance of the COMMD1-deficient dogs as a large animal model for WD.

Hepatocyte-like cells generated by direct reprogramming from murine somatic cells can repopulate decellularized livers

Direct reprogramming represents an easy technique to generate induced hepatocytes (iHeps) from somatic cells. However, current protocols are accompanied by several drawbacks as iHeps are heterogenous and lack fully mature phenotypes of primary hepatocytes. Here, we established a polycistronic expression system to induce the direct reprogramming of mouse embryonic fibroblasts towards hepatocytes. The resulting iHeps are homogenous and display key properties of primary hepatocytes, such as expression of hepatocyte markers, albumin secretion, and presence of liver transaminases. iHeps also possess the capacity to repopulate decellularized liver tissue and exhibit enhanced hepatic maturation. As such, we present a novel strategy to generate homogenous and functional iHeps for applications in tissue engineering and cell therapy.

The mRNA expression of PTTG1 is a strong prognostic indicator for recurrence after hypophysectomy in dogs with corticotroph pituitary adenomas

Pituitary-dependent hypercortisolism (PDH) is a common endocrinopathy in dogs, but the promotors and initiators of the tumourigenesis of corticotroph pituitary adenomas remain unknown. Based on human data, we investigated mRNA expression of pituitary tumour transforming gene 1 (PTTG1) with quantitative RT-PCR in canine corticotroph pituitary adenomas. PTTG1 was overexpressed in adenomas approximately 3-fold. A strong association was observed between PTTG1 expression and disease-free interval; dogs with high PTTG1 expression had a significantly (4 times; P=0.02) shorter disease-free interval than dogs with low PTTG1 expression. This paper shows that PTTG1 expression is a negative prognosticator in relation to disease-free interval and recurrence in dogs undergoing transsphenoidal hypophysectomy as treatment for PDH.

Bioengineered bile ducts recapitulate key cholangiocyte functions

Investigation of diseases of the bile duct system and identification of potential therapeutic targets are hampered by the lack of tractable in vitro systems to model cholangiocyte biology. Here, we show a step-wise method for the differentiation of murine Lgr5⁺ liver stem cells (organoids) into cholangiocyte-like cells (CLCs) using a combination of growth factors and extracellular matrix components. Organoid-derived CLCs display key properties of primary cholangiocytes, such as expressing cholangiocyte markers, forming primary cilia, transporting small molecules and responding to farnesoid X receptor agonist. Integration of organoid-derived cholangiocytes with collagen-coated polyethersulfone hollow fiber membranes yielded bioengineered bile ducts that morphologically resembled native bile ducts and possessed polarized bile acid transport activity. As such, we present a novel in vitro model for studying and therapeutically modulating cholangiocyte function.

An intronic LINE-1 insertion in MERTK is strongly associated with retinopathy in Swedish Vallhund dogs

The domestic dog segregates a significant number of inherited progressive retinal diseases, several of which mirror human retinal diseases and which are collectively termed progressive retinal atrophy (PRA). In 2014, a novel form of PRA was reported in the Swedish Vallhund breed, and the disease was mapped to canine chromosome 17. The causal mutation was not identified, but expression analyses of the retinas of affected Vallhunds demonstrated a 6-fold increased expression of the MERTK gene compared to unaffected dogs. Using 24 retinopathy cases and 97 controls with no clinical signs of retinopathy, we replicated the chromosome 17 association in Swedish Vallhunds from the UK and aimed to elucidate the causal variant underlying this association using whole genome sequencing (WGS) of an affected dog. This revealed a 6-8 kb insertion in intron 1 of MERTK that was not present in WGS of 49 dogs of other breeds. Sequencing and BLASTN analysis of the inserted segment was consistent with the insertion comprising a full-length intact LINE-1 retroelement. Testing of the LINE-1 insertion for association with retinopathy in the UK set of 24 cases and 97 controls revealed a strong statistical association (P-value 6.0 x 10-11) that was subsequently replicated in the original Finnish study set (49 cases and 89 controls (P-value 4.3 x 10-19). In a pooled analysis of both studies (73 cases and 186 controls), the LINE-1 insertion was associated with a ~20-fold increased risk of retinopathy (odds ratio 23.41, 95% confidence intervals 10.99-49.86, P-value 1.3 x 10-27). Our study adds further support for regulatory disruption of MERTK in Swedish Vallhund retinopathy; however, further work is required to establish a functional overexpression model. Future work to characterise the mechanism by which this intronic mutation disrupts gene regulation will further improve the understanding of MERTK biology and its role in retinal function.

HELZ2 Is an IFN Effector Mediating Suppression of Dengue Virus

Flaviviral infections including dengue virus are an increasing clinical problem worldwide. Dengue infection triggers host production of the type 1 IFN, IFN alpha, one of the strongest and broadest acting antivirals known. However, dengue virus subverts host IFN signaling at early steps of IFN signal transduction. This subversion allows unbridled viral replication which subsequently triggers ongoing production of IFN which, again, is subverted. Identification of downstream IFN antiviral effectors will provide targets which could be activated to restore broad acting antiviral activity, stopping the signal to produce endogenous IFN at toxic levels. To this end, we performed a targeted functional genomic screen for IFN antiviral effector genes (IEGs), identifying 56 IEGs required for antiviral effects of IFN against fully infectious dengue virus. Dengue IEGs were enriched for genes encoding nuclear receptor interacting proteins, including HELZ2, MAP2K4, SLC27A2, HSP90AA1, and HSP90AB1. We focused on HELZ2 (Helicase With Zinc Finger 2), an IFN stimulated gene and IEG which encodes a promiscuous nuclear factor coactivator that exists in two isoforms. The two unique HELZ2 isoforms are both IFN responsive, contain ISRE elements, and gene products increase in the nucleus upon IFN stimulation. Chromatin immunoprecipitation-sequencing revealed that the HELZ2 complex interacts with triglyceride-regulator LMF1. Mass spectrometry revealed that HELZ2 knockdown cells are depleted of triglyceride subsets. We thus sought to determine whether HELZ2 interacts with a nuclear receptor known to regulate immune response and lipid metabolism, AHR, and identified HELZ2:AHR interactions via co-immunoprecipitation, found that AHR is a dengue IEG, and that an AHR ligand, FICZ, exhibits anti-dengue activity. Primary bone marrow derived macrophages from HELZ2 knockout mice, compared to wild type controls, exhibit enhanced dengue infectivity. Overall, these findings reveal that IFN antiviral response is mediated by HELZ2 transcriptional upregulation, enrichment of HELZ2 protein levels in the nucleus, and activation of a transcriptional program that appears to modulate intracellular lipid state. IEGs identified in this study may serve as both (1) potential targets for host directed antiviral design, downstream of the common flaviviral subversion point, as well as (2) possible biomarkers, whose variation, natural, or iatrogenic, could affect host response to viral infections.

Obesity--a disease with many aetiologies disguised in the same oversized phenotype: has the overeating theory failed?

Evolution has led to metabolic thrift in humans--a genetic heritage that, when exposed to the modern 'obesogenic' milieu with energy-dense food and a sedentary lifestyle, predisposes to obesity. The current paradigm that overeating of easily digestible carbohydrates and the resulting imbalance between energy in and out as the cause of overweight has recently been challenged. Indeed, studies suggest that the host response to various nutrients contributes to overeating and fat accumulation. Alterations in neurotransmitter functions, changes in the epigenome, dysbiosis of gut microbiota and effects of specific nutrients (or lack of such nutrients) on mitochondrial function and signalling pathways may promote fat accumulation independent of calories. Whereas nutrients that stimulate generation of uric acid (such as fructose and purine-rich food) cause insulin resistance and fat accumulation, other nutrients (such as antioxidants, plant food, probiotics, nuts, soy and omega-3) counteract the negative effects of a calorie-rich diet by salutary effects on mitochondrial biogenesis. Thus, the specific metabolic effects of different nutrients may be more important than its total energy content. By studying the impact of nutrients on mitochondrial health, as well as the trans-generational impact of nutrients during fetal life, and how specific bacterial species correlate with fat mass accumulation, new dietary targets for obesity management may emerge. Overeating and overshooting of calories could to a large extent represent a symptom rather than a cause of obesity; therefore, hypocaloric diets should probably not be the main, and certainly not the only, focus for treatment of the obese patient.

Loss of Nrf2 in mice evokes a congenital intrahepatic shunt that alters hepatic oxygen and protein expression gradients and toxicity

The transcription factor Nrf2 (Nfe2l2 nuclear factor, erythroid 2-like 2) regulates gene expression directly, controlling pharmacological and toxicological responses. These processes may also be influenced by the structure of the hepatic vasculature, which distributes blood flow through compartmentalized microenvironments to maintain organismal stability. Castings of the hepatic portal vasculature of albino C57BL/6J but not ICR Nrf2(-/-) mice revealed a congenital intrahepatic shunt that was present in two thirds of Nrf2-disrupted mice. This shunt directly connected the portal vein to the inferior vena cava and displayed characteristics of a patent ductus venosus. Immunohistochemistry revealed that Nrf2(-/-) mice with an intrahepatic shunt manifest changes to hepatic oxygen and protein expression gradients when compared with wild-type (WT) and non-shunted Nrf2(-/-) mice. Centrilobular hypoxia found in WT and Nrf2(-/-) mice without shunts was reduced in Nrf2(-/-) livers with a shunt. Hepatic protein expression of phosphoenolpyruvate carboxykinase (Pepck), normally confined to the periportal zone, exhibited both periportal and centrilobular zonal expression in livers from Nrf2(-/-) mice with an intrahepatic shunt. Centrilobular expression of Cytochrome P450 2E1 (Cyp2e1) was diminished in shunted Nrf2(-/-) livers compared with WT and Nrf2(-/-) livers without shunts. The intrahepatic shunt in Nrf2(-/-) mice was further found to diminish acetaminophen hepatoxicity compared with WT and Nrf2(-/-) non-shunted mice following a 6 h challenge with 250 mg/kg acetaminophen. The presence of an intrahepatic shunt influences several physiological and pathophysiological properties of Nrf2(-/-) mice through changes in blood flow, hepatic oxygenation, and protein expression that extent beyond loss of canonical transactivation of Nrf2 target genes.

The two main forms of histiocytic sarcoma in the predisposed Flatcoated retriever dog display variation in gene expression

Examination of gene functions in specific tumor types improves insight in tumorigenesis and helps design better treatments. Due to the rarity of histiocytic/dendritic cell sarcoma in humans, it is difficult to accrue such knowledge. Therefore, comparative research of these cancers in predisposed dog breeds, such as the Flatcoated retriever, can be of value. Histiocytic sarcoma in the dog can be grouped into a soft tissue- and visceral form. The soft tissue form at first is localized, while the visceral form progresses more quickly to a terminal state, which might be related to variations in gene expression. Microarray analyses were performed on fresh-frozen tissue from Flatcoated retrievers with either soft tissue- or visceral histiocytic sarcoma. Expression differences of ten most significantly differentially expressed genes were validated with quantitative real-time PCR (q PCR) analyses. Q PCR analyses confirmed the significantly aberrant expression of three of the selected genes: C6 was up-regulated; CLEC12A and CCL5 were down-regulated in the visceral histiocytic sarcoma compared to the soft tissue form. The findings of our study indicate that these two forms of histiocytic sarcoma in the dog display a variation in gene expression and warrant analysis of functional changes in the expression of those genes in these rare sarcomas in man.

Gene expression profiling of histiocytic sarcomas in a canine model: the predisposed flatcoated retriever dog

BACKGROUND

The determination of altered expression of genes in specific tumor types and their effect upon cellular processes may create insight in tumorigenesis and help to design better treatments. The Flatcoated retriever is a dog breed with an exceptionally high incidence of histiocytic sarcomas. The breed develops two distinct entities of histiocytic neoplasia, a soft tissue form and a visceral form. Gene expression studies of these tumors have value for comparable human diseases such as histiocytic/dendritic cell sarcoma for which knowledge is difficult to accrue due to their rare occurrence. In addition, such studies may help in the search for genetic aberrations underlying the genetic predisposition in this dog breed.

METHODS

Microarray analysis and pathway analyses were performed on fresh-frozen tissues obtained from Flatcoated retrievers with localized, soft tissue histiocytic sarcomas (STHS) and disseminated, visceral histiocytic sarcomas (VHS) and on normal canine spleens from various breeds. Expression differences of nine genes were validated with quantitative real-time PCR (qPCR) analyses.

RESULTS

QPCR analyses identified the significantly altered expression of nine genes; PPBP, SpiC, VCAM1, ENPEP, ITGAD (down-regulated), and GTSF1, Col3a1, CD90 and LUM (up-regulated) in the comparison of both the soft tissue and the visceral form with healthy spleen. DAVID pathway analyses revealed 24 pathways that were significantly involved in the development of HS in general, most of which were involved in the DNA repair and replication process.

CONCLUSIONS

This study identified altered expression of nine genes not yet implicated in histiocytic sarcoma manifestations in the dog nor in comparable human histiocytic/dendritic sarcomas. Exploration of the downside effect of canine inbreeding strategies for the study of similar sarcomas in humans might also lead to the identification of genes related to these rare malignancies in the human.