laser-capture-microdissection-highly-pure-trabecular-meshwork-from

Laser Capture Microdissection of Highly Pure Trabecular Meshwork from Mouse Eyes for Gene Expression Analysis

Laser capture microdissection (LCM) has allowed gene expression analysis of single cells and enriched cell populations in tissue sections. LCM is a great ...

National Institute of Environmental Health Sciences, NIH

Riddelliineis a naturally occurring pyrrolizidine alkaloid found in certain poisonous rangeland plants of the western United States. In National Toxicology Program 2-year studies, riddelliine induced high incidences of hemangiosarcoma in the liver of F344/N rats (both sexes) and B6C3F1 mice (males). To understand this pathogenesis, we tested short-term effects of riddelliine. Three groups (control; 1.0 mg/kg/day, high dose used in the 2-year study; and 2.5 mg/kg/day) of seven male F344/N rats per group were terminated after 8 consecutive doses and 30 doses (6 weeks, excluding weekends). Serum vascular endothelial growth factor (VEGF), histological, immunohistochemical [factor VIII-related antigen/von Willebrand factor (fVIII-ra/vWf)], VEGF, VEGF receptor-2 (VEGFR2), glutathione S-transferase-pi, S-phase (BrdU), p53, apoptosis, and ultrastructural evaluations were performed on the liver. Following 8 doses of 1.0 and 2.5 mg/kg/day, increased numbers of apoptotic and S-phase nuclei appeared in hepatocytes and endothelial cells. Following 30 doses of 1.0 and 2.5 mg/kg/day, hepatocytes exhibited reduced mitosis, fewer S-phase nuclei, increased hypertrophy, and fatty degeneration, while endothelial cells showed karyomegaly, cytomegaly, decreased apoptosis, more S-phase nuclei, and p53 positivity. Hepatocytes of treated animals expressed higher VEGF immunopositivity. That altered endothelial cells were fVIII-ra/vWf and VEGFR2 positive confirmed their identity. These changes may have promoted hemangiosarcoma development upon long-term exposure through endothelial adduct formation, apoptosis, proliferation of endothelial cells having undamaged and/or damaged DNA, and mutation. Endothelial proliferation may also have been promoted through endothelial arrest at S phase, which was associated with endothelial karyo- and cytomegaly, resulting in hepatocytic hypoxia, triggering VEGF induction.

The hepatic endothelial carcinogen riddelliine induces endothelial apoptosis, mitosis, S phase, and p53 and hepatocytic vascular endothelial growth factor expression after short-term exposure.

We demonstrated previously that exposure of rats to 2-butoxyethanol (BE) was associated with morphological changes in red blood cells, hemolytic anemia, and disseminated thrombosis and infarction in different organs including the eyes. In order to elucidate the mechanism of thrombosis formation, we examined in this study the histology and immunohistochemical expression of vascular cell adhesion molecule-1 (VCAM-1), endothelial intercellular adhesion molecule-1 (ICAM-1), and P-selectin in the eyes of the female F344 rat exposed to 2, 3, or 4 daily doses of BE/250 mg/kg body weight. In this BE hemolysis and thrombosis model, positive VCAM-1 expression occurred only in eyes of rats exposed to 3 and 4 doses and was localized in the iris (epithelium lining the posterior surface, anterior mesenchymal epithelium), ciliary processes (lining epithelium, stromal cells), and retina (hypertrophic retinal pigment epithelium). Only weak immunolabeling was seen in eyes exposed to 2 doses. The appearance of VCAM-1 immunostaining correlated with the development of thrombosis located in the same structures. No change in ICAM-1 or P-selectin expression was seen. This immunolabeling distribution suggests that VCAM-1 functions in the pathogenesis of BE-related thrombosis by promoting adhesion of erythrocytes to the endothelium.

Ocular expression of vascular cell adhesion molecule (VCAM-1) in 2-butoxyethanol-induced hemolysis and thrombosis in female rats.

Because of possible side effects of herbal medicines containing ephedrine and guarana-derived caffeine, including increased risk of stroke, myocardial infarction, and sudden death, the Food and Drug Administration recently banned the sale of ephedra-containing products, specifically over-the-counter dietary supplements. We report cardiac in 7- and 14-week-old male F344 rats exposed by gavage to ephedrine(25 mg/kg) and caffeine (30 mg/kg) administered in combination for one or two days. The ephedrine-caffeine dosage was approximately 12- and 1.4-fold, respectively, above average human exposure, based on a mg/m2 body surface-area comparison. Several (5/7) of the exposed 14-week-old rats died or were sacrificed in extremis 4-5 h after the first dosing. In these hearts, changes were observed chiefly in the interventricular septum but also left and right ventricular walls. Massive interstitial hemorrhage, with degeneration of myofibers, occurred at the subendocardial myocardium of the left ventricle and interventricular septum. Immunostaining for cleaved caspase-3 and hyperphosphorylated H2A.X, a histone variant that becomes hyperphosphorylated during apoptosis, indicated multifocal generalized positive staining of degenerating myofibers and fragmenting nuclei, respectively. The Barbeito-Lopez trichrome stain revealed generalized patchy yellow myofibers consistent with degeneration and/or coagulative necrosis. In ephedrine-caffeine-treated animals terminated after the second dosing, foci of myocardial degeneration and necrosis were already infiltrated by mixed inflammatory cells. The myocardial necrosis may occur secondarily to intense diffuse vasoconstriction of the coronary arterial system with decreased myocardial perfusion. Our work shows the direct relationship between combined ephedrine and caffeine exposure and cardiac pathology.

Acute hemorrhagic myocardial necrosis and sudden death of rats exposed to a combination of ephedrine and caffeine.

Changes in the serum proteome were identified during early, fulminant, and recovery phases of liver injury from acetaminophen in the rat. Male F344 rats received a single, noninjury dose or a high, injury-producing dose of acetaminophen for evaluation at 6 to 120 h. Two-dimensional gel electrophoresis of immunodepleted serum separated approximately 800 stained proteins per sample from which differentially expressed proteins were identified by mass spectrometry. Serum alanine aminotransferase/aspartate aminotransferase levels and histopathology revealed the greatest liver damage at 24 and 48 h after high-dose acetaminophen corresponding to the time of greatest serum protein alterations. After 24 h, 68 serum proteins were significantly altered of which 23 proteins were increased by >5-fold and 20 proteins were newly present compared with controls. Only minimal changes in serum proteins were noted at the low dose without any histopathology. Of the 54 total protein isoforms identified by mass spectrometry, gene ontology processes for 38 unique serum proteins revealed involvement of acute phase response, coagulation, protein degradation, intermediary metabolism, and various carrier proteins. Elevated serum tumor necrosis factor-alpha from 24 to 48 h suggested a mild inflammatory response accompanied by increased antioxidant capability demonstrated by increased serum catalase activity. Antibody array and enzyme-linked immunosorbent assay analyses also showed elevation in the chemokine monocyte chemoattractant protein-1 and the metalloprotease inhibitor tissue inhibitor of metalloproteinases-1 during this same period of liver injury. This study demonstrates that serum proteome alterations probably reflect both liver damage and a concerted, complex response of the body for organ repair and recovery during acute hepatic injury.

Alterations in the rat serum proteome during liver injury from acetaminophen exposure.

Different degrees of a toxic response between and within the various lobes of the liver have been observed in rodents following treatment with acetaminophen. This study was designed to compare 2 sampling methods of the rat liver for gene-expression analysis. Ten male Fischer 344/N rats, 12-14 weeks of age, were treated with vehicle (0.5% aqueous ethyl cellulose) or acetaminophen (APAP, 1500 mg/kg) and sacrificed 24 hours following dose administration. Two representative sections were collected from the left liver lobe, stained with hematoxylin and eosin (H&E), and evaluated independently by 2 pathologists. The central core of the left lobe was cubed and frozen. Five random cubes were conserved, while the remaining left lobe core was pulverized. From each of the 10 animals, 2 random cubes and 2 samples from the homogeneous, pulverized samples were prepared for microarray analysis. Histopathologic evaluation revealed a variable response of centrilobular necrosis within the left lobe. Multiple methods used to analyze the microarray data indicated that sampling technique was not a major contributor to the variability observed in the gene expression data; however, only the powdered samples clustered for all animals, even those with disparate histopathologic results. Additionally, a powdered sample provided the advantages of a homogenous sample pool and the ability to use sample aliquots for other analyses to include proteomics, metabonomics, and other molecular techniques.

Optimal sampling of rat liver tissue for toxicogenomic studies.

Peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) is a member of the transcriptional coactivator family that plays a central role in the regulation of cellular energy metabolism under various physiological stimuli. During fasting, PGC-1α is induced in the liver and together with estrogen-related receptor a and γ (ERRα and ERRγ, orphan nuclear receptors with no known endogenous ligand, regulate sets of genes that participate in the energy balance program. We found that PGC-1α, ERRα and ERRγ was highly expressed in human kidney HK2 cells and that PGC-1α induced dynamic protein interactions on the ERRα chromatin. However, the effect of fasting on the expression of endogenous PGC-1α, ERRα and ERRγ in the kidney is not known.

Fasting induces the expression of PGC-1α and ERR isoforms in the outer stripe of the outer medulla (OSOM) of the mouse kidney.

Archival tissues from laboratory studies represent a unique opportunity to explore the relationship between genomic changes and agent-induced disease. In this study, we evaluated the applicability of qPCR for detecting genomic changes in formalin-fixed, paraffin-embedded (FFPE) tissues by determining if a subset of 14 genes from a 90-gene signature derived from microarray data and associated with eventual tumor development could be detected in archival liver, kidney, and lung of rats exposed to aflatoxin B1 (AFB1) for 90 days in feed at 1 ppm. These tissues originated from the same rats used in the microarray study. The 14 genes evaluated were Adam8, Cdh13, Ddit4l, Mybl2, Akr7a3, Akr7a2, Fhit, Wwox, Abcb1b, Abcc3, Cxcl1, Gsta5, Grin2c, and the C8orf46 homologue. The qPCR FFPE liver results were compared to the original liver microarray data and to qPCR results using RNA from fresh frozen liver. Archival liver paraffin blocks yielded 30 to 50 μg of degraded RNA that ranged in size from 0.1 to 4 kB. qPCR results from FFPE and fresh frozen liver samples were positively correlated (p ≤ 0.05) by regression analysis and showed good agreement in direction and proportion of change with microarray data for 11 of 14 genes. All 14 transcripts could be amplified from FFPE kidney RNA except the glutamate receptor gene Grin2c; however, only Abcb1b was significantly upregulated from control. Abundant constitutive transcripts, S18 and β-actin, could be amplified from lung FFPE samples, but the narrow RNA size range (25-500 bp length) prevented consistent detection of target transcripts. Overall, a discrete gene signature derived from prior transcript profiling and representing cell cycle progression, DNA damage response, and xenosensor and detoxication pathways was successfully applied to archival liver and kidney by qPCR and indicated that gene expression changes in response to subchronic AFB1 exposure occurred predominantly in the liver, the primary target for AFB1-induced tumors. We conclude that an evaluation of gene signatures in archival tissues can be an important toxicological tool for evaluating critical molecular events associated with chemical exposures.

Testing an aflatoxin B1 gene signature in rat archival tissues.

Store-operated Ca(2+) entry (SOCE) is a major Ca(2+) influx pathway in most non-excitable cell types and Orai1 was recently identified as an essential pore-subunit of SOCE channels. Here we investigate the physiological role of Orai1 in bone homeostasis using Orai1-deficient mice (Orai1(-/-)). Orai1(-/-) mice developed osteopenia with decreased bone mineral density and trabecular bone volume. To identify the nature and origin of the bone defect, bone-resorbing osteoclasts and bone-forming osteoblasts from Orai1(-/-) mice were examined. Orai1-mediated SOCE was completely abolished in Orai1(-/-) osteoclast precursor cells and osteoclastogenesis in vitro from Orai1(-/-) mice was impaired due to a defect in cell fusion of pre-osteoclasts. Also, resorption activity in vitro was comparable but the size of pits formed by Orai1(-/-) osteoclasts was smaller. We next assessed the role of Orai1 in osteoblast differentiation and function by using a pre-osteoblast cell line, as well as primary osteoblasts from wild-type and Orai1(-/-) mice. SOCE in MC3T3-E1 pre-osteoblastic cells was inactivated by lentiviral overexpression of a pore-dead Orai1 mutant. Lack of SOCE in MC3T3-E1 had no effect on alkaline phosphatase staining and expression but substantially inhibited mineralized nodule formation. Consistent with this finding, Orai1-mediated SOCE was markedly reduced in Orai1(-/-) osteoblast precursor cells and osteoblastogenesis in vitro from Orai1(-/-) stromal cells showed impaired mineral deposition but no change in differentiation. This indicates that Orai1 is involved in the function but not in the differentiation of osteoblasts. Together, these results suggest that Orai1 plays a critical role in bone homeostasis by regulating both osteoblasts and osteoclasts.

Deletion of Orai1 alters expression of multiple genes during osteoclast and osteoblast maturation.

Mammalian mitochondrial DNA (mtDNA) is replicated by the heterotrimeric Pol γ comprised of a single catalytic subunit, encoded by Polg, and a homodimeric accessory subunit encoded by the Polg2 gene. While the catalytic subunit has been shown to be essential for embryo development, genetic data regarding the accessory subunit are lacking in mammalian systems. Here, we describe the generation of heterozygous (Polg2(+/-)) and homozygous (Polg2(-/-)) knockout (KO) mice. Polg2(+/-) mice are haplosufficient and develop normally with no discernable difference in mitochondrial function through 2 years of age. In contrast, the Polg2(-/-) is embryonic lethal at day 8.0-8.5 p.c. with concomitant loss of mtDNA and mtDNA gene products. Electron microscopy shows severe ultra-structural defects and loss of organized cristae in mitochondria of the Polg2(-/-) embryos as well as an increase in lipid accumulation compared with both wild-type (WT) and Polg2(+/-) embryos. Our data indicate that Polg2 function is critical to mammalian embryogenesis and mtDNA replication, and that a single copy of Polg2 is sufficient to sustain life.

Polg2 is essential for mammalian embryogenesis and is required for mtDNA maintenance.

N, N-dimethyl-p-toluidine (DMPT; Cas No. 99-97-8), an accelerant for methyl methacrylate monomers in medical devices, is a nasal cavity carcinogen according to a 2-yr cancer study of male and female F344/N rats, with the nasal tumors arising from the transitional cell epithelium. In this study, we exposed male F344/N rats for 5 days to DMPT (0, 1, 6, 20, 60, or 120 mg/kg [oral gavage]) to explore the early changes in the nasal cavity after short-term exposure. Lesions occurred in the nasal cavity including hyperplasia of transitional cell epithelium (60 and 120 mg/kg). Nasal tissue was rapidly removed and preserved for subsequent laser capture microdissection and isolation of the transitional cell epithelium (0 and 120 mg/kg) for transcriptomic studies. DMPT transitional cell epithelium gene transcript patterns were characteristic of an antioxidative damage response (e.g., Akr7a3, Maff, and Mgst3), cell proliferation, and decrease in signals for apoptosis. The transcripts of amino acid transporters were upregulated (e.g., Slc7a11). The DMPT nasal transcript expression pattern was similar to that found in the rat nasal cavity after formaldehyde exposure, with over 1,000 transcripts in common. Molecular changes in the nasal cavity after DMPT exposure suggest that oxidative damage is a mechanism of the DMPT toxic and/or carcinogenic effects.

Molecular Changes in the Nasal Cavity after N, N-dimethyl-p-toluidine Exposure.

There are currently no reports describing mammary gland development in the Harlan Sprague-Dawley (HSD) rat, the current strain of choice for National Toxicology Program (NTP) testing. Our goals were to empower the NTP, contract labs, and other researchers in understanding and interpreting chemical effects in this rat strain. To delineate similarities/differences between the female and male mammary gland, data were compiled starting on embryonic day 15.5 through postnatal day 70. Mammary gland whole mounts, histology sections, and immunohistochemically stained tissues for estrogen, progesterone, and androgen receptors were evaluated in both sexes; qualitative and quantitative differences are highlighted using a comprehensive visual timeline. Research on endocrine disrupting chemicals in animal models has highlighted chemically induced mammary gland anomalies that may potentially impact human health. In order to investigate these effects within the HSD strain, 2,3,7,8-tetrachlorodibenzo-p-dioxin, diethylstilbestrol, or vehicle control was gavage dosed on gestation day 15 and 18 to demonstrate delayed, accelerated, and control mammary gland growth in offspring, respectively. We provide illustrations of normal and chemically altered mammary gland development in HSD male and female rats to help inform researchers unfamiliar with the tissue and may facilitate enhanced evaluation of both male and female mammary glands in juvenile toxicity studies.

Mammary Gland Evaluation in Juvenile Toxicity Studies: Temporal Developmental Patterns in the Male and Female Harlan Sprague-Dawley Rat.

Poly(A) tail length and mRNA deadenylation play important roles in gene regulation. However, how they regulate embryonic development and pluripotent cell fate is not fully understood. Here we present evidence that CNOT3-dependent mRNA deadenylation governs the pluripotent state. We show that CNOT3, a component of the Ccr4-Not deadenylase complex, is required for mouse epiblast maintenance. It is highly expressed in blastocysts and its deletion leads to peri-implantation lethality. The epiblast cells in Cnot3 deletion embryos are quickly lost during diapause and fail to outgrow in culture. Mechanistically, CNOT3 C terminus is required for its interaction with the complex and its function in embryonic stem cells (ESCs). Furthermore, Cnot3 deletion results in increases in the poly(A) tail lengths, half-lives, and steady-state levels of differentiation gene mRNAs. The half-lives of CNOT3 target mRNAs are shorter in ESCs and become longer during normal differentiation. Together, we propose that CNOT3 maintains the pluripotent state by promoting differentiation gene mRNA deadenylation and degradation, and we identify poly(A) tail-length regulation as a post-transcriptional mechanism that controls pluripotency.

CNOT3-Dependent mRNA Deadenylation Safeguards the Pluripotent State.

Methionine metabolism is critical for epigenetic maintenance, redox homeostasis, and animal development. However, the regulation of methionine metabolism remains unclear. Here, we provide evidence that SIRT1, the most conserved mammalian NAD-dependent protein deacetylase, is critically involved in modulating methionine metabolism, thereby impacting maintenance of mouse embryonic stem cells (mESCs) and subsequent embryogenesis. We demonstrate that SIRT1-deficient mESCs are hypersensitive to methionine restriction/depletion-induced differentiation and apoptosis, primarily due to a reduced conversion of methionine to S-adenosylmethionine. This reduction markedly decreases methylation levels of histones, resulting in dramatic alterations in gene expression profiles. Mechanistically, we discover that the enzyme converting methionine to S-adenosylmethionine in mESCs, methionine adenosyltransferase 2a (MAT2a), is under control of Myc and SIRT1. Consistently, SIRT1 KO embryos display reduced  expression and histone methylation and are sensitive to maternal methionine restriction-induced lethality, whereas maternal methionine supplementation increases the survival of SIRT1 KO newborn mice. Our findings uncover a novel regulatory mechanism for methionine metabolism and highlight the importance of methionine metabolism in SIRT1-mediated mESC maintenance and embryonic development.

Article	Year
The hepatic endothelial carcinogen riddelliine induces endothelial apoptosis, mitosis, S phase, and p53 and hepatocytic vascular endothelial growth factor expression after short-term exposur... Toxicology and applied pharmacology\| PubMed ID: 12460743	2002
Ocular expression of vascular cell adhesion molecule (VCAM-1) in 2-butoxyethanol-induced hemolysis and thrombosis in female rats. Experimental and toxicologic pathology : official journal of the Gesellschaft fur Toxikologische Pathologie\| PubMed ID: 14703767	2003
Acute hemorrhagic myocardial necrosis and sudden death of rats exposed to a combination of ephedrine and caffeine. Toxicological sciences : an official journal of the Society of Toxicology\| PubMed ID: 15537744	2005
Alterations in the rat serum proteome during liver injury from acetaminophen exposure. The Journal of pharmacology and experimental therapeutics\| PubMed ID: 16687475	2006
Optimal sampling of rat liver tissue for toxicogenomic studies. Toxicologic pathology\| PubMed ID: 17162537	2006
Fasting induces the expression of PGC-1α and ERR isoforms in the outer stripe of the outer medulla (OSOM) of the mouse kidney. PloS one\| PubMed ID: 22073226	2011
Testing an aflatoxin B1 gene signature in rat archival tissues. Chemical research in toxicology\| PubMed ID: 22545673	2012
Deletion of Orai1 alters expression of multiple genes during osteoclast and osteoblast maturation. Cell calcium\| PubMed ID: 23122304	2012
Polg2 is essential for mammalian embryogenesis and is required for mtDNA maintenance. Human molecular genetics\| PubMed ID: 23197651	2013
Molecular Changes in the Nasal Cavity after N, N-dimethyl-p-toluidine Exposure. Toxicologic pathology\| PubMed ID: 27099258	2016
Mammary Gland Evaluation in Juvenile Toxicity Studies: Temporal Developmental Patterns in the Male and Female Harlan Sprague-Dawley Rat. Toxicologic pathology\| PubMed ID: 27613106	2016
CNOT3-Dependent mRNA Deadenylation Safeguards the Pluripotent State. Stem cell reports\| PubMed ID: 27746116	2016
Methionine metabolism is essential for SIRT1-regulated mouse embryonic stem cell maintenance and embryonic development. The EMBO journal\| PubMed ID: 29021282	2017

Julie Foley

Biography

JoVE Journal Publications

Other Publications