We are greatly appreciative for the assistance from the Cattle Fever tick Laboratory in Edinburg, Texas. We would like to thank Michael Moses, Jason Tidwell, James Hellums, Cesario Agado, and Homer Vasquez. We would also like to acknowledge the assistance of Sarah Sharpton, Elizabeth Lohstroh, Amy Filip, Kelsey Johnson, Kelli Kochcan, Andrew Hillhouse, Charluz Arocho Rosario, and Stephanie Guzman Valencia throughout the project. We would like to thank the Texas A&#38;M Aggie Women in Entomology (AWE) Writing Group for their help and advice during the writing of this manuscript. The following reagents were provided by Centers for Disease Control and Prevention for distribution by BEI Resources, NIAID, NIH: Ixodes scapularis Adult (Live), NR-42510. Female I. scapularis ticks were also received from the Tick Rearing Facility at Oklahoma State University. This project was funded by Texas A&#38;M University T3: triads for transformation grant and the cooperative agreement #58-3094-1-003 by the USDA-ARS to AOC.

All animal experiments were performed following animal usage protocol (AUP#2020-0026) approved by the institutional animal care and use committee (AICUC) at Texas A&#38;M University. The tick species, Ixodes scapularis&#160;and Rhipicephalus (Boophilus) microplus, and New Zealand Male White Rabbits, 42-72 days of age, were used for the present study. I. scapularis was received from the Center for Disease Control (CDC) and Oklahoma State University, certified as pathogen-free.&#160;R. microp...

The current protocol provides a detailed methodology for extracting miRNA from salivary glands and EVs. However, there are important considerations, all of which are detailed in the notes for each section of this protocol. The capsule and mesh netting must be secured during tick feeding to prevent ticks from escaping. The capsule preparation and placement are described in Koga et al.40. Several replicates of the tick dissections need to be done if an unsuitable sample is discarded. Additionally, s...

Ticks are ectoparasites that vector many pathogens to wildlife, livestock, humans, and their pets1,2. Tick feeding results in significant economic loss by causing damage to hide, reducing weight and milk production due to severe anemia, and the transmission of potentially deadly disease-causing pathogens1,3,4,5. Current control practices for managing tick populations are focused on the use of acaricides. Nevertheless, the continuous emergence of acaricide resistance in ticks parasitizing livestock5,6, the increased incidence of tick bites7, and pathogen transmission within residential areas8,9, have led to a need for unique tick control alternatives.
The tick salivary glands are essential organs that ensure a tick&#39;s biological success. They are formed by different acinus types (I, II, III, and IV) with various physiological functions. The salivary glands are responsible for osmoregulation, both off and on the host, by returning water excess and iron content to the host via salivation2,10. Type I acini are also involved in the uptake of water from the atmosphere by the secretion of hygroscopic saliva10,11. Salivary effector proteins, such as cement and cystatins, are produced within secretory cells in type II and III acini10,12. Type I acini do not affect tick feeding, indicating that the bloodmeal intake does not trigger morphological and physiological changes in these acini type13,14. On the other hand, Acini type II and III are activated during feeding and present very little activity pre-attachment. Thus, feeding is necessary to trigger the enlargement of the secretory cells within type II acini and the production of bioactive compounds. Type III acini are reduced in size during feeding due to the secretion within the secretory granules12.
The salivary glands are also the site of pathogen infection in the tick and route of transmission. During feeding, ticks secrete several compounds with pharmaceutical effects that are needed for successful completion of the bloodmeal10,15,16. These compounds have anti-inflammatory, immunosuppressive, and vasodilatory properties10,15,17. Recent studies have shown that extracellular vesicles (EVs) derived from tick salivary glands harbor several of these compounds, inducing anti-inflammatory and immuno-modulatory effects18,19,20. &#34;Extracellular vesicles&#34; is an umbrella term used to describe vesicles classified as exosomes and microvesicles based on their size and biogenesis. Overall, EVs are lipid blebs with bilayer membranes that are ~40 nm-1 &#181;m in size21; generally, exosomes are described as being 40-150 nm in size, whereas microvesicles are between 150 nm-1 &#181;m in size21,22,23. However, the size is not indicative of the EVs biogenesis pathway22.
The biogenesis of exosomes starts with the sequential invagination of the plasma membrane. This invagination leads to the formation of multivesicular bodies and finally results in the deformation of the vesicular membrane by the action of ESCRT complexes or sphingomyelinases (sMases)24,25. The exosomes can either be lysed within the lysosomes to maintain cellular homeostasis or exit via vesicular fusion to the plasma membrane to deliver cellular constituents to the recipient cells21,24. On the other hand, microvesicles are formed by the action of flopasses and flipasses, changing the conformation of lipids in the plasma membrane26. EVs are essential for cell-to-cell communication, serving as a transport system for intracellular cargo, such as lipids, proteins, nucleic acids, and microRNAs (miRNAs)21,27,28. Once transported, these vesicles deliver their cargo into the cytoplasm of the recipient cells, generating phenotypic changes in the receiving cell22,29. Due to the importance of extracellular vesicles in tick feeding and the manipulation of host immune and wound healing responses18,20, the cargo within extracellular vesicles presents potential targets for the development of anti-tick therapeutics and a unique mechanism to disrupt tick feeding. This includes miRNAs within tick salivary glands and salivary gland-derived extracellular vesicles.
miRNAs are short non-coding sequences, ~18-22 nucleotide (nt) in length, that can post-transcriptionally regulate, degrade, or silence mRNA sequences30,31. During transcription, the pri-miRNAs are cleaved by Dicer (RNA polymerase III) to form a distinctive hairpin-like structure, becoming a pre-miRNA. The pre-miRNA is cut once again by Drosha (RNA polymerase III) to form a mature miRNA duplex. The mature sequence becomes integrated into the RNA-induced silencing complex (RISC) complementary to the mRNA sequence, causing translation repression or mRNA degradation28,30,32. During host feeding, miRNAs within the tick saliva can modulate host gene expression to suppress immune responses and enhance pathogen transmission33,34,35,36,37. Although extensive studies on EVs and miRNAs exist, their roles during feeding at the tick-host interface are still poorly understood. Optimizing protocols that can easily result in the isolation and purification of high-quality miRNAs is crucial for advancing our knowledge on these topics.
Multiple options can be utilized to isolate EVs, such as ultracentrifugation, exosome precipitation, polymer precipitation, immunoaffinity chromatography, and size-based exclusion techniques38. However, these techniques cannot distinguish between exosomes or microvesicles. Thus, as mentioned previously, EV is used as an umbrella term when isolating EVs from different samples. The vesicles isolated in the experiments described herein represent a mixture of vesicles derived from different biogenesis pathways. Further purification of a specific population of extracellular vesicles can be achieved by immunoprecipitation using beads coated with antibodies against markers (i.e., exosomal markers, tumor markers) unique to the vesicle population of interest39,40. miRNAs can also be extracted via different commercially available isolation kits7,41,42.
The objective of this project was to develop a protocol that combines commonly applied methods to isolate EVs and extract miRNA from both EVs and fed-tick salivary glands. Because the secretion of bioactive compounds is activated by feeding12, ticks should be allowed to feed to identify miRNAs that may be important for manipulating host immune and wound healing responses. The present protocol requires a small number of ticks (20 ticks) to isolate EVs and their respective miRNAs, compared to other previously described studies that required 2000 ticks43. Further, it avoids the contamination of salivary secretions with pilocarpine44, which could influence experiments studying the effect of EVs and their miRNAs on host cells.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.22 &#181;m syringe filter</td>
			<td>GenClone</td>
			<td>25-240</td>
			<td></td>
		</tr>
		<tr>
			<td>1 &#181;m nylon syringe filter</td>
			<td>Tisch Scientific</td>
			<td>283129028</td>
			<td></td>
		</tr>
		<tr>
			<td>1 inch black adhesive</td>
			<td>Amazon</td>
			<td>B00FQ937NM</td>
			<td>Capsule</td>
		</tr>
		<tr>
			<td>10 mL needeless syringe</td>
			<td>Exelint</td>
			<td>26265</td>
			<td></td>
		</tr>
		<tr>
			<td>3&#39; and 5&#39; Adapters</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-Seq Kit</td>
		</tr>
		<tr>
			<td>4 mm vannas scissors</td>
			<td>Fine Science Tools</td>
			<td>15000-08</td>
			<td></td>
		</tr>
		<tr>
			<td>4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid</td>
			<td>Sigma-Aldrich</td>
			<td>1.1523</td>
			<td></td>
		</tr>
		<tr>
			<td>70Ti rotor</td>
			<td>Beckman Coulter</td>
			<td>337922</td>
			<td></td>
		</tr>
		<tr>
			<td>Amphotericin</td>
			<td>Corning</td>
			<td>30-003-CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Beads</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-Seq Kit</td>
		</tr>
		<tr>
			<td>Bioanalyzer</td>
			<td>Agilent</td>
			<td>G2939BA</td>
			<td></td>
		</tr>
		<tr>
			<td>Bioanalyzer kit</td>
			<td>Agilent</td>
			<td>5067-1513</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge 5425</td>
			<td>Eppendorf</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Macron</td>
			<td>UN1888</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyverse Discovery Enviornment</td>
			<td></td>
			<td></td>
			<td>https://cyverse.org/discovery-environment</td>
		</tr>
		<tr>
			<td>Dissecting microscope</td>
			<td>Nikon</td>
			<td>SMZ745</td>
			<td></td>
		</tr>
		<tr>
			<td>Double-sideded carpet tape</td>
			<td>amazon</td>
			<td>&#8206;286373</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon Tubes, 50 mL</td>
			<td>VWR</td>
			<td>21008-940</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Gibco</td>
			<td>FBS-02-0050</td>
			<td></td>
		</tr>
		<tr>
			<td>fine forceps</td>
			<td>Excelta</td>
			<td>5-S-SE</td>
			<td></td>
		</tr>
		<tr>
			<td>Foamies, 2 mm</td>
			<td>Amazon</td>
			<td>B004M5QGBQ</td>
			<td>Capsule</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Phoenix Pharmaceuticals manfactured</td>
			<td>193.33165.3</td>
			<td></td>
		</tr>
		<tr>
			<td>Ixodes scaplaris</td>
			<td>CDC, Oklahoma State University</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>L15C300 medium</td>
			<td>In-lab</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>lipoprotein-cholesterol concentrate</td>
			<td>MPI</td>
			<td>02191476-CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slide</td>
			<td>VWR</td>
			<td>10118-596</td>
			<td></td>
		</tr>
		<tr>
			<td>miRDeep2</td>
			<td></td>
			<td></td>
			<td>https://github.com/rajewsky-lab/mirdeep2</td>
		</tr>
		<tr>
			<td>M-MuLV Reverse Transcriptase</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-Seq Kit</td>
		</tr>
		<tr>
			<td>molecular grade ethanol</td>
			<td>Fischer Bioreagents</td>
			<td>UN1170</td>
			<td></td>
		</tr>
		<tr>
			<td>multi-well 24 well tissue culture treated plate</td>
			<td>Corning</td>
			<td>353047</td>
			<td></td>
		</tr>
		<tr>
			<td>Nanopaticle Tracking Analyzer machine</td>
			<td>Malvern Panalytical</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nanosep with 300K Omega filter</td>
			<td>Pall Corporation</td>
			<td>OD3003C33</td>
			<td></td>
		</tr>
		<tr>
			<td>NEXTFLEX Small RNA-Seq Kit v3</td>
			<td>PerkinElmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NextSeq 500/550 High Output Kit (75 cycles)</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td></td>
		</tr>
		<tr>
			<td>Optima XPN 90 Ultracentrifuge</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin</td>
			<td>Thermofischer Scientific</td>
			<td>ICN19453780</td>
			<td></td>
		</tr>
		<tr>
			<td>Pippettes</td>
			<td>Ependorff</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>polycarbonate centrifuge bottle</td>
			<td>Beckman Coulter</td>
			<td>355618</td>
			<td></td>
		</tr>
		<tr>
			<td>Qiagen miRNeasy kit</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAzol lysis reagent</td>
			<td>Qiagen</td>
			<td>79306</td>
			<td></td>
		</tr>
		<tr>
			<td>Qubit</td>
			<td>Thermofisher</td>
			<td>Q32880</td>
			<td></td>
		</tr>
		<tr>
			<td>Qubit kit</td>
			<td>Thermofisher</td>
			<td>Q10212</td>
			<td></td>
		</tr>
		<tr>
			<td>Rabbits</td>
			<td>Charles River</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Reverse Universal Primer</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-Seq Kit</td>
		</tr>
		<tr>
			<td>Rhipicephalus microplus</td>
			<td>Cattle Fever Tick Research Labratoty</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rifampicin</td>
			<td>Fischer Bioreagents</td>
			<td>215544</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAlater</td>
			<td>Invitrogen</td>
			<td>833280</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAse free tubes</td>
			<td>VWR</td>
			<td>87003294</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAse inhibitor</td>
			<td>Thermo Fischer</td>
			<td>11111729</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAse/DNAse free water</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Minelute spin column</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td>Qiagen miRNeasy kit</td>
		</tr>
		<tr>
			<td>RPE Buffer</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td>Qiagen miRNeasy kit</td>
		</tr>
		<tr>
			<td>RT Buffer</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-seq kit</td>
		</tr>
		<tr>
			<td>RT Forward Primer</td>
			<td>Illumina</td>
			<td>20024906</td>
			<td>NEXTFLEX Small RNA-seq kit</td>
		</tr>
		<tr>
			<td>RTE Buffer</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td>Qiagen miRNeasy kit</td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Sigma-Aldrich</td>
			<td>S6014-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall ST16</td>
			<td>Thermo Fischer</td>
			<td>75004380</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilized Gauze sponges</td>
			<td>Covidien</td>
			<td>2187</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilized PBS</td>
			<td>Sigma</td>
			<td>RNBK0694</td>
			<td></td>
		</tr>
		<tr>
			<td>streptomycin</td>
			<td>thermofischer Scientific</td>
			<td>15240062</td>
			<td></td>
		</tr>
		<tr>
			<td>TapeStation</td>
			<td>Aligent</td>
			<td>G2991BA</td>
			<td></td>
		</tr>
		<tr>
			<td>Tear Mender Instant Fabric and Leather Adhesive</td>
			<td>Amazon</td>
			<td>7.42836E+11</td>
			<td>Capsule</td>
		</tr>
		<tr>
			<td>Tissue Adhesive</td>
			<td>3M VetBond</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Triple Antibiotics</td>
			<td>dechra</td>
			<td>17033-122-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptose phosphate broth</td>
			<td>BD</td>
			<td>BD 260300</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation of micrornas from tick ex vivo salivary gland cultures and extracellular vesicles

Ticks are important ectoparasites that can vector multiple pathogens. The salivary glands of ticks are essential for feeding as their saliva contains many effectors with pharmaceutical properties that can diminish host immune responses and enhance pathogen transmission. One group of such effectors are microRNAs (miRNAs). miRNAs are short non-coding sequences that regulate host gene expression at the tick-host interface and within the organs of the tick. These small RNAs are transported in the tick saliva via extracellular vesicles (EVs), which serve inter-and intracellular communication. Vesicles containing miRNAs have been identified in the saliva of ticks. However, little is known about the roles and profiles of the miRNAs in tick salivary vesicles and glands. Furthermore, the study of vesicles and miRNAs in tick saliva requires tedious procedures to collect tick saliva. This protocol aims to develop and validate a method for isolating miRNAs from purified extracellular vesicles produced by ex vivo organ cultures. The materials and methodology needed to extract miRNAs from extracellular vesicles and tick salivary glands are described herein.

The present protocol provides a detailed methodology to extract miRNAs from salivary glands and EVs. According to the results, this protocol is effective for the isolation of miRNA from adults of two different tick species, I. scapularis and R. microplus, and can potentially be used in other tick species as well. The EVs concentration (particles/mL) was measured via NTA. For R. microplus, each gender and life stage contained three biological replicates measured in three technical repli...

Watch this Scientific Journal Video about Isolation of microRNAs from Tick Ex Vivo Salivary Gland Cultures and Extracellular Vesicles at JoVE.com

Isolation of microRNAs from Tick Ex Vivo Salivary Gland Cultures and Extracellular Vesicles

The present protocol describes the isolation of microRNAs from tick salivary glands and purified extracellular vesicles. This is a universal procedure that combines commonly used reagents and supplies. The method also allows the use of a small number of ticks, resulting in quality microRNAs that can be readily sequenced.

Isolation of microRNAs from Tick Ex Vivo Salivary Gland Cultures and Extracellular Vesicles

Ticks are important ectoparasites that can vector multiple pathogens. The salivary glands of ticks are essential for feeding as their saliva contains many ...

This protocol allows us to use a reduced number of ticks which reduces the cost of colony maintenance and decreases the number of vertebrae animals needed for tick feeding. This protocol requires approximately 20 ticks. However, the main advantage aside from using a small sample size is that this protocol can be applied to multiple tick species and different life stages.Aside from tick dissections or the application towards host-parasite interactions, the effect of pathogen infection on microRNA secretion and the effect of physiological changes on microRNA secreted by ticks. To begin, prepare vesicle-free media by adding fetal bovine serum, tryptose phosphate broth, 10%lipoprotein cholesterol concentrate, 5%sodium bicarbonate, HEPES, and L15C300 medium into a 26.3 milliliter polycarbonate centrifuge bottle and adjust the volume as required. Now ultracentrifuge the medium at 100, 000 times G at four degrees Celsius for 18 hours.Carefully remove the supernatant without disturbing the pellet and transfer the supernatant to a fresh centrifuge tube. Ultracentrifuge the tube once again. Take the supernatant and pass it through a 0.22 micrometer filter to remove contaminants.Pipette the supernatant into a 50 milliliter centrifuge tube and store it at minus 20 degrees Celsius until required or up to three years. Add an appropriate amount of antibiotics to 500 microliters of the vesicle-free medium in each well of a 24-well culture plate. Now, add PBS with rifampicin to the wells that do not contain vesicle-free medium to prevent bacterial growth.Place the ticks on a glass slide with double-sided carpet tape under a dissecting microscope. Before dissection, add PBS containing rifampicin to the tick and using four millimeter Vannas scissors, make an incision of approximately one millimeter on the side of each female. Now, remove the tick's dorsal side and salivary glands, then put 20 to 40 tick salivary glands in 500 microliters of vesicle-free medium added to a single well in a 24-well tissue culture treated plate.Incubate the salivary gland samples at 32 degrees Celsius for 24 hours to allow the secretion of the extracellular vesicles. At the end of the incubation, pipette all the medium containing the salivary glands into a 1.5 milliliter microcentrifuge tube and centrifuge at 300 times G at four degrees Celsius for 10 minutes. Transfer the supernatant into a new 1.5 milliliter microcentrifuge tube.Resuspend the pellet containing the salivary glands in RNA later and store at minus 80 degrees Celsius until used or indefinitely. Now, remove the cellular debris by centrifuging the supernatant at 2, 000 times G at four degrees Celsius for 10 minutes and pipette the supernatant into a new 1.5 milliliter microcentrifuge tube. Next, centrifuge at 10, 000 times G for 30 minutes at four degrees Celsius to remove apoptotic bodies and larger extracellular vesicles and transfer the supernatant to a fresh 1.5 milliliter microcentrifuge tube.Then assemble a one micrometer nylon syringe filter on a 10 milliliter syringe and keep it on an ultracentrifuge tube. Then add the sample and fill the syringe with 10 milliliters of PBS. Pass the supernatant through the filter into the tube.After filtering and balancing the tubes, place them into a 70 Ti rotor and ultracentrifuge the tubes at 100, 000 times G for 18 hours at four degrees Celsius. The concentrated extracellular vesicles form a pellet after ultracentrifugation. Remove the supernatant without disturbing the pellet and resuspend the pellet in PBS.Pipette 500 microliters of the extracellular vesicle into a 300 K centrifugal filter and centrifuge at 8, 000 times G for 10 minutes at ambient temperature and repeat this procedure until all extracellular vesicles are filtered. Finally, add 400 microliters of sterilized PBS to the column and mix thoroughly to remove extracellular vesicles attached to the membrane. Then put the sample into a 1.5 milliliter DNAase RNAse free tube.The concentration and size of extracellular vesicles varied depending on the gender and the life stage of the ticks in between the biological replicates for females, males, and nymphs. For all combined biological replicates, similar results were observed. Analysis of small RNAs isolated from the salivary gland showed bands corresponding to ribosomal RNA and microRNAs.However, the ribosomal RNAs were absent in the vesicles isolated from the salivary glands, and microRNA samples purified from extracellular vesicles showed more degradation. After enrichment, the microRNA samples purified from EVs showed minimal degradation and sufficient microRNA concentration for cDNA library synthesis. The expected band size of approximately 150 base pairs after cDNA library preparation was obtained signifies small RNA cDNA libraries.During vesicle-free preparation, ensure to follow the steps to prevent external vesicle contamination. During well plate preparation, make sure to add antibiotics to prevent bacterial contamination from the tick microbiome. The microRNAs extracted using this protocol can be used for profiling and functional experiments to validate microRNA roles such as predicting microRNA pathway targets, inhibition, and mimicry experiments.

Isolation of microRNAs from Tick Ex Vivo Salivary Gland Cultures and Extracellular Vesicles

Abstract