Comprehensive ECG reference intervals in C57BL/6N substrains provide a generalizable guide for cardiac electrophysiology studies in mice.

Reference ranges provide a powerful tool for diagnostic decision-making in clinical medicine and are enormously valuable for understanding normality in pre-clinical scientific research that uses in vivo models. As yet, there are no published reference ranges for electrocardiography (ECG) in the laboratory mouse. The first mouse-specific reference ranges for the assessment of electrical conduction are reported herein generated from an ECG dataset of unprecedented scale. International Mouse Phenotyping Consortium data from over 26,000 conscious or anesthetized C57BL/6N wildtype control mice were stratified by sex and age to develop robust ECG reference ranges. Interesting findings include that heart rate and key elements from the ECG waveform (RR-, PR-, ST-, QT-interval, QT corrected, and QRS complex) demonstrate minimal sexual dimorphism. As expected, anesthesia induces a decrease in heart rate and was shown for both inhalation (isoflurane) and injectable (tribromoethanol) anesthesia. In the absence of pharmacological, environmental, or genetic challenges, we did not observe major age-related ECG changes in C57BL/6N-inbred mice as the differences in the reference ranges of 12-week-old compared to 62-week-old mice were negligible. The generalizability of the C57BL/6N substrain reference ranges was demonstrated by comparison with ECG data from a wide range of non-IMPC studies. The close overlap in data from a wide range of mouse strains suggests that the C57BL/6N-based reference ranges can be used as a robust and comprehensive indicator of normality. We report a unique ECG reference resource of fundamental importance for any experimental study of cardiac function in mice.

Genetic and pharmacological evaluation of cathepsin s in a mouse model of asthma.

Cathepsin S (Cat S) is predominantly expressed in antigen-presenting cells and is up-regulated in several preclinical models of antigen-induced inflammation, suggesting a role in the allergic response. Prophylactic dosing of an irreversible Cat S inhibitor has been shown to attenuate pulmonary eosinophilia in mice, supporting the hypothesis that Cat S inhibition before the initiation of airway inflammation is beneficial in airway disease. In addition, Cat S has been shown to play a role in more distal events in the allergic response. To determine where Cat S inhibition may affect the allergic response, we used complementary genetic and pharmacological approaches to investigate the role of Cat S in the early and downstream allergic events in a murine model of antigen-induced lung inflammation. Cat S knockout mice did not develop ovalbumin-induced pulmonary inflammation, consistent with a role for Cat S in the development of the allergic response. Alternatively, wild-type mice were treated with a reversible, highly selective Cat S inhibitor in prophylactic and therapeutic dosing paradigms and assessed for changes in airway inflammation. Although both treatment paradigms resulted in potent Cat S inhibition, only prophylactic Cat S inhibitor dosing blocked lung inflammation, consistent with our findings in Cat S knockout mice. The findings indicate that although Cat S is up-regulated in allergic models, it does not appear to play a significant role in the downstream effector inflammatory phase in this model; however, our results demonstrate that Cat S inhibition in a prophylactic paradigm would ameliorate airway inflammation.

Ultrasound-Guided Approaches to Improve Orthotopic Mouse Xenograft Models for Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer death worldwide. While curative approaches for early stage HCC exist, effective treatment options for advanced HCC are lacking. Furthermore, there are no efficient chemopreventive strategies to limit HCC development once cirrhosis is established. One challenge for drug development is unsatisfactory animal models. In this article, we describe an orthotopic xenograft mouse model of human liver cancer cell lines through image-guided injection into the liver. This technique provides a less invasive yet highly efficient approach to engraft human HCC into mouse liver. Similarly, image-guided injections are used to deliver chemotherapeutics locally, enabling reduction in potential systemic adverse effects, while reducing the required dose for a therapeutic effect. In summary, this image-guided strategy provides a novel and convenient approach to improve current HCC mouse models. © 2019 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Identification of a functional site on the type I TGF-beta receptor by mutational analysis of its ectodomain.

Six charged amino acid residues located in the ectodomain of the full-length type I transforming growth factor (TGF)-beta receptor were individually mutated to alanine. Mutation of residues D47, D98, K102 and E104 resulted in functionally impaired receptors as demonstrated by a marked decrease in ligand-dependent signaling and ligand internalization relative to the wild-type receptor. The other two mutants (K39A and K87A) exhibited wild-type-like activity. Molecular modeling indicates that the four functionally important residues are located on the convex face of the ectodomain structure. Since mutation of these four residues affects signaling and ligand internalization but not ligand binding, we propose that this functional site is an interacting site between type I and II receptors.

Site-directed mutagenesis of the type II TGF-beta receptor indicates a ligand-binding site distinct from that of the type II activin receptor.

Site-directed mutagenesis was used to map the ligand-binding surface of the type II transforming growth factor-beta receptor extracellular domain (TbetaRII-ECD). Two putative ligand-binding sites were probed, the first being a predicted hydrophobic patch, the second being the finger 1 surface loop. Nine residues were mutated in the context of full-length TbetaRII and the effect of these mutations on ligand-binding and receptor signaling was analyzed. Complementary information was obtained by examining 'natural' evolutionary TbetaRII mutations. Together, the results indicate that residues within the finger 1 region, but not the hydrophobic patch, of the TbetaRII-ECD are required for productive ligand-binding. We conclude that, surprisingly, the ECDs of TbetaRII and type II activin receptor utilize distinct interacting surfaces for binding their respective ligands.

Oligo safety working group exaggerated pharmacology subcommittee consensus document.

This document summarizes the current consensus opinion of the Exaggerated Pharmacology (EP) Subcommittee of the Oligonucleotide Safety Working Group on the appropriate strategies to assess potential adverse effects caused by an "exaggerated" degree of the intended pharmacologic activity of an oligonucleotide (ON). The Subcommittee focused its discussions primarily on the ON subclasses that impact expression of "host" (i.e., human gene products--antisense, small interfering RNAs, and related ONs that target messenger RNA), with later and more limited discussions on aptamer, immunostimulatory, and microRNA subclasses. It is expected that many of these principles will be relevant to other subclasses but will need to be carefully considered as those development programs advance towards clinical trials. The recommendations may also serve as a frame of reference when designing Good Laboratory Practice safety studies with ONs, with regard to the study design elements that address assessment of EP. It is also hoped that these recommendations will establish a foundation for discussion with regulatory agencies on this subject.

Identification of genes and networks driving cardiovascular and metabolic phenotypes in a mouse F2 intercross.

To identify the genes and pathways that underlie cardiovascular and metabolic phenotypes we performed an integrated analysis of a mouse C57BL/6JxA/J F2 (B6AF2) cross by relating genome-wide gene expression data from adipose, kidney, and liver tissues to physiological endpoints measured in the population. We have identified a large number of trait QTLs including loci driving variation in cardiac function on chromosomes 2 and 6 and a hotspot for adiposity, energy metabolism, and glucose traits on chromosome 8. Integration of adipose gene expression data identified a core set of genes that drive the chromosome 8 adiposity QTL. This chromosome 8 trans eQTL signature contains genes associated with mitochondrial function and oxidative phosphorylation and maps to a subnetwork with conserved function in humans that was previously implicated in human obesity. In addition, human eSNPs corresponding to orthologous genes from the signature show enrichment for association to type II diabetes in the DIAGRAM cohort, supporting the idea that the chromosome 8 locus perturbs a molecular network that in humans senses variations in DNA and in turn affects metabolic disease risk. We functionally validate predictions from this approach by demonstrating metabolic phenotypes in knockout mice for three genes from the trans eQTL signature, Akr1b8, Emr1, and Rgs2. In addition we show that the transcriptional signatures for knockout of two of these genes, Akr1b8 and Rgs2, map to the F2 network modules associated with the chromosome 8 trans eQTL signature and that these modules are in turn very significantly correlated with adiposity in the F2 population. Overall this study demonstrates how integrating gene expression data with QTL analysis in a network-based framework can aid in the elucidation of the molecular drivers of disease that can be translated from mice to humans.

Advantageous toxicity profile of inhaled antisense oligonucleotides following chronic dosing in non-human primates.

TPI ASM8 and TPI 1100 are two products containing modified phosphorothioate antisense oligonucleotides (AONs), which are undergoing development for the treatment of asthma and chronic obstructive pulmonary disease (COPD), respectively. TPI ASM8 is comprised of two AONs, one targeting the human chemokine receptor 3 (CCR3) and the other targeting the common beta-chain of the IL-3/IL-5/GM-CSF receptors. TPI 1100 is also a dual-AON compound targeting the phosphodiesterase (PDE) 4 and 7 isotypes. For both products, the AONs are present in a 1:1 ratio by weight. Both products will be administered by inhalation to patients, and TPI ASM8 is currently undergoing Phase 2 clinical trials. As part of the safety assessment of both products, the toxicity and disposition (i.e., pharmacokinetics of the AON components in plasma and tissues) were investigated in 14-day inhalation studies in monkeys at doses ranging from 0.05 to 2.5mg/kg/day. Results indicated that both products were safe and well tolerated at all dose levels. Reversible treatment-related alterations were only observed at the high dose levels tested and were limited to changes in the respiratory tract which were characterized primarily by the presence of alveolar macrophages in the absence of a generalized inflammatory response. Plasma pharmacokinetic profiles showed very low plasma concentrations, and no plasma accumulation was observed after repeated doses. While significant amounts of the AONs of both TPI ASM8 and TPI 1100 were measured in trachea and lung, only limited amounts of the AONs could be measured in kidney and liver, which, in combination with the low plasma level data, is indicative of very low systemic exposure. Taken together, these results demonstrate that these two new AON-based products are safe and that delivery via the inhaled route achieves localized deposition in the pulmonary tract with very limited systemic exposure and reduced toxicity compared to other routes of AON administration.

Quantitative ultrasonic tissue characterization as a new tool for continuous monitoring of chronic liver remodelling in mice.

BACKGROUND/AIM: Recognition of the limitations of liver biopsies has led to the need for non-invasive tests to assess liver fibrosis from intensity and kinetic point of views. The aim of the present study was to evaluate non-invasive ultrasonic tissue characterization for the continuous monitoring of this process in mice. METHODS: Twelve-week-old male and female C57Bl6/J mice were submitted to repetitive carbon-tetrachloride (CCl4) intraperitoneal injections during 8 weeks or analysed 28 days after common bile duct ligation (BDL). The extent and kinetic of the disease progression were followed by the measurement of ultrasound backscatter intensity. This was compared with histological and blood parameter analysis. RESULTS: CCl4 induced a progressive increase in in vivo liver tissue backscatter intensity in both males and females. This increase was mainly correlated with interstitial fibrosis and, to a lower extent, with nuclear surface of the hepatocytes. A similar result was found after BDL. CONCLUSIONS: These data demonstrate for the first time in a systematic study that ultrasound tissue characterization can be used as a reliable tool to follow liver remodelling in mice continuously.

Expression of TGF-beta type II receptor antisense RNA impairs TGF-beta signaling in vitro and promotes mammary gland differentiation in vivo.

In order to clarify the role of TGF-beta in mammary development and tumorigenesis, we investigated the efficacy of full- or partial-length TbetaRII antisense RNA specifically to reduce TbetaRII levels in both in vitro and in vivo model systems. Here we show that the expression of TbetaRII antisense RNA in vitro reduced TbetaRII cell surface expression and inhibited the antiproliferative and transcriptional responses to exogenous TGF-beta. Expression of full-length TbetaRII antisense RNA in a transgenic mouse model under control of the mouse mammary tumor virus promotor resulted in precocious lobuloalveolar development of the mammary gland, a phenotype that resembles that of early pregnancy. These data demonstrate that TbetaRII plays a critical role in maintaining the nondifferentiated character of virgin mammary gland epithelium.