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Immunology and Infection

Lung microRNA Profiling Across the Estrous Cycle in Ozone-exposed Mice

Published: January 7th, 2019



1Pulmonary, Immunology and Physiology Laboratory, Department of Pediatrics, Pennsylvania State University College of Medicine, 2Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine

Here we describe a method to assess lung expression of miRNAs that are predicted to regulate inflammatory genes using mice exposed to ozone or filtered air at different stages of the estrous cycle.

MicroRNA (miRNA) profiling has become of interest to researchers working in various research areas of biology and medicine. Current studies show a promising future of using miRNAs in the diagnosis and care of lung diseases. Here, we define a protocol for miRNA profiling to measure the relative abundance of a group of miRNAs predicted to regulate inflammatory genes in the lung tissue from of an ozone-induced airway inflammation mouse model. Because it has been shown that circulating sex hormone levels can affect the regulation of lung innate immunity in females, the purpose of this method is to describe an inflammatory miRNA profiling protocol in female mice, taking into consideration the estrous cycle stage of each animal at the time of ozone exposure. We also address applicable bioinformatics approaches to miRNA discovery and target identification methods using limma, an R/Bioconductor software, and functional analysis software to understand the biological context and pathways associated with differential miRNA expression.

microRNAs (miRNAs) are short (19 to 25 nucleotides), naturally occurring, non-coding RNA molecules.Sequences of miRNAs are evolutionary conserved across species, suggesting the importance of miRNAs in regulating physiological functions1. microRNA expression profiling has been proven to be helpful for identifying miRNAs that are important in the regulation of a variety of processes, including the immune response, cell differentiation, developmental processes, and apoptosis2. More recently, miRNAs have been recognized for their potential use in disease diagnostics and therapeutics. For researchers studying mechanisms of ge....

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All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Penn State University.

1. Assessment of the Estrous Cycle Stage

  1. Properly restrain a female C57BL/6 mouse (8–9 weeks old) using the one-handed mouse restraint technique described in Machholz et al.10.
  2. Fill the sterile plastic pipette with 10 μL of ultra-pure water.
  3. Introduce the tip of plastic pipette into the vagina.
  4. .......

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The different cell types observed in smears are used to identify the mouse estrous cycle stage (Figure 1). These are identified by cell morphology. During proestrus, cells are almost exclusively clusters of round-shaped, well-formed nucleated epithelial cells (Figure 1A). When the mouse is in the estrus stage, cells are cornified squamous epithelial cells, present in densely packed clusters (Figure 1B

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MicroRNA profiling is an advantageous technique for both disease diagnosis and mechanistic research. In this manuscript, we defined a protocol to evaluate the expression of miRNAs that are predicted to regulate inflammatory genes in the lungs of female mice exposed to ozone in different estrous cycle stages. Methods for the determination of the estrous cycle, such as the visual detection method, have been described16. However, these rely on one-time measurements, and therefore are unreliable. To a.......

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This research was supported by grants from NIH K01HL133520 (PS) and K12HD055882 (PS). The authors thank Dr. Joanna Floros for the assistance with ozone exposure experiments.


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Name Company Catalog Number Comments
C57BL/6J mice The Jackson Laboratory 000664 8 weeks old
UltraPure Water Thermo Fisher Scientific 10813012
Sterile plastic pipette Fisher Scientific 13-711-25 Capacity: 1.7mL
Frosted Microscope Slides Thermo Fisher Scientific 2951TS
Light microscope Microscope World MW3-H5 10X and 20X objective
Ketathesia- Ketamine HCl Injection USP Henry Schein Animal Health 55853 90 mg/kg. Controlled drug.
Xylazine Sterile Solution Lloyd Laboratories 139-236 10mg/kg. Controlled Drug.
Ethanol Fisher Scientific BP2818100 Dilute to 70% ethanol with water.
21G gauge needle BD Biosciences 305165
Syringe Fisher Scientific 329654 1mL
Operating Scissors World Precision Instruments 501221, 504613 14cm, Sharp/Blunt, Curved and 9 cm, Straight, Fine Sharp Tip
Tweezer Kit World Precision Instruments 504616
-80 ˚C freezer Forma 7240
Spectrum Bessman Tissue Pulverizers Fisher Scientific 08-418-1 Capacity: 10 to 50mg
RNase-free Microfuge Tubes Thermo Fisher Scientific AM12400 1.5 mL
TRIzol Reagent Thermo Fisher Scientific 15596026
Direct-zol RNA MiniPrep Plus Zymo Research R2071
NanoDrop Thermo Fisher Scientific ND-ONE-W
miScript II RT kit Qiagen 218161
Mouse Inflammatory Response & Autoimmunity miRNA PCR Array Qiagen MIMM-105Z
Thin-walled, DNase-free, RNase-free PCR tubes Thermo Fisher Scientific AM12225 for 20 μl reactions
miRNeasy Serum/Plasma Spike-in Control Qiagen 219610
Microsoft Excel Microsoft Corporation
Ingenuity Pathway Analysis Qiagen
R Software The R Foundation
Thermal cycler or chilling/heating block General Lab Supplier
Microcentrifuge General Lab Supplier
Real-time PCR cycler General Lab Supplier
Multichannel pipettor General Lab Supplier
RNA wash buffer Zymo Research R1003-3-48 48 mL
DNA digestion buffer Zymo Research E1010-1-4 4 mL
RNA pre-wash buffer Zymo Research R1020-2-25 25 mL
Ultraviolet ozone analyzer Teledyne API Model T400
Mass flow controllers Sierra Instruments Inc Flobox 951/954

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