April 28, 2021
Speakers: Matthew Hartness, Brenda Finney, Emilyanne Leonard, and Ian Roman
Educational Levels: Advanced, Emerging

- Advances in the Measurement of Thyroid Hormones to Assess Endocrine Disruption Potential of Chemicals in the Rat

Endocrine disruptors are substances that can cause harmful effects to the endocrine system. Test guidelines on the screening and testing of chemicals published by the Organisation for Economic Co-operation and Development (OECD) have been updated to include thyroid hormone measurements for assessing endocrine disrupter potency. Meaningful measurement of circulating levels of thyroid hormones is not without its challenges due to intra- and inter-animal variability. Several guidelines require analysis in juvenile rats, which requires sensitive assays with low sample volumes. Consequently, sampling regimes need to be carefully designed and controlled with regard to time and duration of collection, randomization, sampling route, and volume. Thyroid hormone analysis can be performed by different methods, including radioimmunoassay, microtiter plate-based enzyme-linked immunosorbent assay, automated immunoassay, and mass spectroscopy, each with its own strengths and weaknesses. Sequani have recently validated the Rat Thyroid Hormone Panel (Merck) using the MAGPIX platform (Luminex), which enables multiplexing of T3, T4, and TSH in a single analysis. This method facilitated sample volume reduction by 90 % and was shown to be suitable to detect changes in all three analytes in both juvenile and adult rats.

- Spatial Biology—Localization and Quantification of the Invisible

Selected by Nature Methods to be the Method of the Year for 2020, spatially resolved transcriptomics is rapidly changing the way we use tissue sections. The GeoMX DSP platform from NanoString is being used by Propath UK to aid their clients’ research, enhancing the information that can be obtained from a single section of FFPE tissue over standard IHC or ISH or even multiplexed IHC. Using the GeoMx, up to 96 protein targets or 18,000 RNA targets can be quantitatively assessed and physically localized within the tissue section. Regions of Interest (ROI) can be specifically selected by the research team. Quantitative readouts are produced using either the nCounter (NanoString) platform or NGS platform and linked back to their spatial location within the GeoMx software. Expression results can then be normalized, reviewed, grouped, and visualized as needed based on the research question. This case study showcases the GeoMx workflow using a study on mouse syngeneic tumor tissue samples that utilized IHC results for a specific protein of interest on adjacent sections to guide ROI selection. This enabled a deeper dive into the differences in biology that were happening in separate regions of the tumors.  

- In Vivo Bone Marrow Toxicology Investigations in Combination Oncology Therapy

Measuring bone marrow toxicity is a critical piece of the safety puzzle, particularly when evaluating oncology compounds in combination. Utilizing a flow cytometry panel to enumerate myeloid, erythroid, lymphoid, and platelet cell populations in rat femurs, we investigated two oncology drugs in monotherapy and combination to evaluate potential toxicology after 14 days of dosing. The monotherapy group demonstrated fewer significant changes in the bone marrow cell populations compared with the combination therapy group.

- Platelet Indices: Useful or Just More Numbers?

Cardiovascular complication is one of the primary causes of marketed drug withdrawals. Current core parameter measurements measured during the preclinical and clinical safety assessment of novel medicines are based on recommendations that are nearly 21 years old and only include absolute platelet counts and by their nature are not ideally designed to identify drug-induced platelet alteration in safety and efficacy studies (Schultze et al., 2013). We investigated the use of the additional platelet parameters on the Siemens Advia 2120 in the hope that they may give earlier indications of platelet alteration in beagle dogs. We found that some of these parameters, such as MPV, PDW, and MPC, could be of use in certain conditions; however, there were limitations that have to be considered.