Monitoring mouse papillomavirus-associated cancer development using longitudinal Pap smear screening.

A substantial percentage of the population remains at risk for cervical cancer due to pre-existing human papillomavirus (HPV) infections, despite prophylactic vaccines. Early diagnosis and treatment are crucial for better disease outcomes. The development of new treatments heavily relies on suitable preclinical model systems. Recently, we established a mouse papillomavirus (MmuPV1) model that is relevant to HPV genital pathogenesis. In the current study, we validated the use of Papanicolaou (Pap) smears, a valuable early diagnostic tool for detecting HPV cervical cancer, to monitor disease progression in the MmuPV1 mouse model. Biweekly cervicovaginal swabs were collected from the MmuPV1-infected mice for viral DNA quantitation and cytology assessment. The Pap smear slides were evaluated for signs of epithelial cell abnormalities using the 2014 Bethesda system criteria. Tissues from the infected mice were harvested at various times post-viral infection for additional histological and virological assays. Over time, increased viral replication was consistent with higher levels of viral DNA, and it coincided with an uptick in epithelial cell abnormalities with higher severity scores noted as early as 10 weeks after viral infection. The cytological results also correlated with the histological evaluation of tissues harvested simultaneously. Both immunocompromised and immunocompetent mice with squamous cell carcinoma (SCC) cytology also developed vaginal SCCs. Notably, samples from the MmuPV1-infected mice exhibited similar cellular abnormalities compared to the corresponding human samples at similar disease stages. Hence, Pap smear screening proves to be an effective tool for the longitudinal monitoring of disease progression in the MmuPV1 mouse model. IMPORTANCE: Papanicolaou (Pap) smear has saved millions of women's lives as a valuable early screening tool for detecting human papillomavirus (HPV) cervical precancers and cancer. However, more than 200,000 women in the United States alone remain at risk for cervical cancer due to pre-existing HPV infection-induced precancers, as there are currently no effective treatments for HPV-associated precancers and cancers other than invasive procedures including a loop electrosurgical excision procedure (LEEP) to remove abnormal tissues. In the current study, we validated the use of Pap smears to monitor disease progression in our recently established mouse papillomavirus model. To the best of our knowledge, this is the first study that provides compelling evidence of applying Pap smears from cervicovaginal swabs to monitor disease progression in mice. This HPV-relevant cytology assay will enable us to develop and test novel antiviral and anti-tumor therapies using this model to eliminate HPV-associated diseases and cancers.

Mitochondrial Magnesium is the cationic rheostat for MCU-mediated mitochondrial Ca2+ uptake.

Calcium (Ca2+) uptake by mitochondria is essential in regulating bioenergetics, cell death, and cytosolic Ca2+ transients. Mitochondrial Calcium Uniporter (MCU) mediates the mitochondrial Ca2+ uptake. MCU is a heterooligomeric complex with a pore-forming component and accessory proteins required for channel activity. Though MCU regulation by MICUs is unequivocally established, there needs to be more knowledge of whether divalent cations regulate MCU. Here we set out to understand the mitochondrial matrix Mg2+-dependent regulation of MCU activity. We showed Mrs2 as the authentic mammalian mitochondrial Mg2+ channel using the planar lipid bilayer recordings. Using a liver-specific Mrs2 KO mouse model, we showed that decreased matrix [Mg2+] is associated with increased MCU activity and matrix Ca2+ overload. The disruption of Mg2+dependent MCU regulation significantly prompted mitochondrial permeability transition pore opening-mediated cell death during tissue IR injury. Our findings support a critical role for mMg2+ in regulating MCU activity and attenuating mCa2+ overload.

Computational 3D histological phenotyping of whole zebrafish by X-ray histotomography.

Organismal phenotypes frequently involve multiple organ systems. Histology is a powerful way to detect cellular and tissue phenotypes, but is largely descriptive and subjective. To determine how synchrotron-based X-ray micro-tomography (micro-CT) can yield 3-dimensional whole-organism images suitable for quantitative histological phenotyping, we scanned whole zebrafish, a small vertebrate model with diverse tissues, at ~1 micron voxel resolutions. Micro-CT optimized for cellular characterization (histotomography) allows brain nuclei to be computationally segmented and assigned to brain regions, and cell shapes and volumes to be computed for motor neurons and red blood cells. Striking individual phenotypic variation was apparent from color maps of computed densities of brain nuclei. Unlike histology, the histotomography also allows the study of 3-dimensional structures of millimeter scale that cross multiple tissue planes. We expect the computational and visual insights into 3D cell and tissue architecture provided by histotomography to be useful for reference atlases, hypothesis generation, comprehensive organismal screens, and diagnostics.

Rigid Embedding of Fixed and Stained, Whole, Millimeter-Scale Specimens for Section-free 3D Histology by Micro-Computed Tomography.

For over a hundred years, the histological study of tissues has been the gold standard for medical diagnosis because histology allows all cell types in every tissue to be identified and characterized. Our laboratory is actively working to make technological advances in X-ray micro-computed tomography (micro-CT) that will bring the diagnostic power of histology to the study of full tissue volumes at cellular resolution (i.e., an X-ray Histo-tomography modality). Toward this end, we have made targeted improvements to the sample preparation pipeline. One key optimization, and the focus of the present work, is a straightforward method for rigid embedding of fixed and stained millimeter-scale samples. Many of the published methods for sample immobilization and correlative micro-CT imaging rely on placing the samples in paraffin wax, agarose, or liquids such as alcohol. Our approach extends this work with custom procedures and the design of a 3-dimensional printable apparatus to embed the samples in an acrylic resin directly into polyimide tubing, which is relatively transparent to X-rays. Herein, sample preparation procedures are described for the samples from 0.5 to 10 mm in diameter, which would be suitable for whole zebrafish larvae and juveniles, or other animals and tissue samples of similar dimensions. As proof of concept, we have embedded the specimens from Danio, Drosophila, Daphnia, and a mouse embryo; representative images from 3-dimensional scans for three of these samples are shown. Importantly, our methodology leads to multiple benefits including rigid immobilization, long-term preservation of laboriously-created resources, and the ability to re-interrogate samples.

Comparative analysis of fixation and embedding techniques for optimized histological preparation of zebrafish.

In recognition of the importance of zebrafish as a model organism for studying human disease, we have created zebrafish content for a web-based reference atlas of microanatomy for comparing histology and histopathology between model systems and with humans (http://bio-atlas.psu.edu). Fixation, decalcification, embedding, and sectioning of zebrafish were optimized to maximize section quality. A comparison of protocols involving six fixatives showed that 10% Neutral Buffered Formalin at 21°C for 24h yielded excellent results. Sectioning of juveniles and adults requires bone decalcification; EDTA at 0.35M produced effective decalcification in 21-day-old juveniles through adults (≥~3Months). To improve section plane consistency in sets of larvae, we have developed new array casting molds based on the outside contours of larvae derived from 3D microCT images. Tissue discontinuity in sections, a common barrier to creating quality sections of zebrafish, was minimized by processing and embedding the formalin-fixed zebrafish tissues in plasticized forms of paraffin wax, and by periodic hydration of the block surface in ice water between sets of sections. Optimal H&E (Hematoxylin and Eosin) staining was achieved through refinement of standard protocols. High quality slide scans produced from glass histology slides were digitally processed to maximize image quality, and experimental replicates posted as full slides as part of this publication. Modifications to tissue processing are still needed to eliminate the need for block surface hydration. The further addition of slide collections from other model systems and 3D tools for visualizing tissue architecture would greatly increase the utility of the digital atlas.

Synchrotron microCT imaging of soft tissue in juvenile zebrafish reveals retinotectal projections.

Biomedical research and clinical diagnosis would benefit greatly from full volume determinations of anatomical phenotype. Comprehensive tools for morphological phenotyping are central for the emerging field of phenomics, which requires high-throughput, systematic, accurate, and reproducible data collection from organisms affected by genetic, disease, or environmental variables. Theoretically, complete anatomical phenotyping requires the assessment of every cell type in the whole organism, but this ideal is presently untenable due to the lack of an unbiased 3D imaging method that allows histopathological assessment of any cell type despite optical opacity. Histopathology, the current clinical standard for diagnostic phenotyping, involves the microscopic study of tissue sections to assess qualitative aspects of tissue architecture, disease mechanisms, and physiological state. However, quantitative features of tissue architecture such as cellular composition and cell counting in tissue volumes can only be approximated due to characteristics of tissue sectioning, including incomplete sampling and the constraints of 2D imaging of 5 micron thick tissue slabs. We have used a small, vertebrate organism, the zebrafish, to test the potential of microCT for systematic macroscopic and microscopic morphological phenotyping. While cell resolution is routinely achieved using methods such as light sheet fluorescence microscopy and optical tomography, these methods do not provide the pancellular perspective characteristic of histology, and are constrained by the limited penetration of visible light through pigmented and opaque specimens, as characterizes zebrafish juveniles. Here, we provide an example of neuroanatomy that can be studied by microCT of stained soft tissue at 1.43 micron isotropic voxel resolution. We conclude that synchrotron microCT is a form of 3D imaging that may potentially be adopted towards more reproducible, large-scale, morphological phenotyping of optically opaque tissues. Further development of soft tissue microCT, visualization and quantitative tools will enhance its utility.

Discovery of novel antitumor antimitotic agents that also reverse tumor resistance.

We have discovered a novel series of 7-benzyl-4-methyl-5-[(2-substituted phenyl)ethyl]-7H-pyrrolo[2,3-d]pyrimidin-2-amines, which possess antimitotic and antitumor activities against antimitotic-sensitive as well as resistant tumor cells. These agents bind to a site on tubulin that is distinct from the colchicine, vinca alkaloid, and paclitaxel binding sites and some, in addition to their antitumor activity, remarkably also reverse tumor resistance to antimitotic agents mediated via the P-glycoprotein efflux pump. The compounds were synthesized from N-(7-benzyl-5-ethynyl-4-methyl-7H-pyrrolo[2,3-d]pyrimidin-2-yl)-2,2-dimethylpropanamide 11 or the corresponding 5-iodo analog 14 via Sonogashira couplings with appropriate iodobenzenes or phenylacetylene followed by reduction and deprotection to afford the target analogs. Sodium and liquid NH3 afforded the debenzylated analogs. The most potent analog 1 was one to three digit nanomolar against the growth of both sensitive and resistant tumor cells in culture. Compounds of this series are promising novel antimitotic agents that have the potential for treating both sensitive and resistant tumors.

Synthesis, conformational analysis, and cytotoxicity of new analogues of the natural cyclodepsipeptide jaspamide.

Three analogues of the natural bioactive cyclodepsipeptide jaspamide (3-5) were efficiently synthesized using a combination of solid and solution phase techniques. The preliminary design of the molecules has involved the rational substitution and/or simplification of the most critical structural features of the lead compound. The synthetic products were subjected to pharmacological assays, and the conformational properties were investigated by MM (molecular mechanics) and MD (molecular dynamics) calculations, to describe the potential pharmacophoric core responsible for the observed activities.

Cyclohexyl-octahydro-pyrrolo[1,2-a]pyrazine-based inhibitors of human N-myristoyltransferase-1.

N-myristoyltransferase (NMT) is an emerging therapeutic target that catalyzes the attachment of myristate to the N terminus of an acceptor protein. We have developed a medium-throughput assay for screening potential small molecule inhibitors of human NMT-1 consisting of recombinant enzyme, biotinylated peptide substrate, and [3H]myristoyl-CoA. Approximately 16,000 diverse compounds have been evaluated, and significant inhibition of NMT was found with 0.8% of the compounds. From these hits, we have identified the cyclohexyl-octahydropyrrolo[1,2-a]pyrazine (COPP) chemotype as inhibitory toward human NMT-1. Thirty-two compounds containing this substructure inhibited NMT-1, with IC(50) values ranging from 6 microM to millimolar concentrations, and a quantitative structure-activity relationship equation (r(2) = 0.72) was derived for the series. The most potent inhibitor (24, containing 9-ethyl-9H-carbazole) demonstrated competitive inhibition for the peptide-binding site of NMT-1 and noncompetitive inhibition for the myristoyl-CoA site. Computational docking studies using the crystal structure of the highly homologous yeast NMT confirmed that 24 binds with excellent complementarity to the peptide-binding site of the enzyme. To evaluate the ability of 24 to inhibit NMT activity in intact cells, monkey CV-1 cells expressing an N-myristoylated green fluorescent protein (GFP) fusion protein were treated with a known NMT inhibitor or with 24. Each compound caused the redistribution of GFP from the plasma membrane to the cytosol. Furthermore, 24 inhibits cancer cell proliferation at doses similar to those that inhibit protein myristoylation. Overall, these studies establish an efficient assay for screening for inhibitors of human NMT and identify a novel family of inhibitors that compete at the peptide-binding site and have activity in intact cells.