Name: enrichment of native lipoprotein particles with microrna and subsequent determination of their absolute/relative microrna content and their cellular transfer rate
Uploaded: 2019-05-09T15:00:00
Duration: 11 min 13 s
Description: Watch this Scientific Journal Video about Enrichment of Native Lipoprotein Particles with microRNA and Subsequent Determination of Their Absolute/Relative microRNA Content and Their Cellular Transfer

This work was supported by the Austrian Science Fund Project P29110-B21, the &#8220;Hochschuljubil&#228;umsstiftung der Stadt Wien zur F&#246;rderung der Wissenschaft&#8221; Project H-3065/2011, the European Fund for Regional Development (EFRE, IWB2020), the Federal State of Upper Austria, and the &#8220;Land O&#214; Basisfinanzierung&#8221;.

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The authors have nothing to disclose.

Here, the isolation of lipoprotein particle fractions from human blood and the determination of their individual miRNA content is described step-by-step. It is critical to work in an RNase-free environment while handling isolated and synthesized miRNA&#8212;particle-embedded miRNA is obviously sheltered from enzymatic degradation. As the miRNA/particle ratio of native lipoprotein particles is rather low, artificial enrichment with miRNA is required to study the holo particle uptake of cells. Thereby, the reconstitution of HDL particles as described previously7 is modified to incorporate miRNA strands. Additionally, the separation of the lipid and protein fraction during this procedure allows scientists to examine lipid- and protein-associated components of the lipoprotein particle19. In a similar way, the labeling procedure of LDL particles is adapted. Interestingly, the addition of spermine&#8212;a natural stabilizer of nucleotides&#8212;did not influence the miRNA/particle ratio. It should be noted that, in principle, the method allows the infolding of other substances than miRNA within a lipoprotein particle. Of course, there is a limit with regard to the physical size of the substance based on the overall size of HDL (diameter: 5-12 nm) and LDL particles (diameter: 18-25 nm).
Concerning the quality control of reconstituted/labeled lipoprotein particles, HS-AFM is an applicable method to characterize HDL/LDL particles at the single particle level. In comparison to EM, it allows for shorter preparation times and near-physiological conditions (wet, room temperature).
Due to its inherent sensitivity and amplification, qPCR is the method of choice to detect low miRNA concentrations. Alternatively, single-molecule sensitive fluorescence microscopy, which is able to detect even individual molecules, would not be suitable due to the low concentrations of, for instance, fluorescently labeled miRNA strands per particle. Thus, the ratio of miRNA strands per native lipoprotein particle has been found to be 10-8. Artificial enrichment increases the ratio by a factor of 10,000, which facilitates the estimation of the cellular lipoprotein uptake rate (no significant difference is detected using native lipoprotein particles 19). The high sensitivity of qPCR makes it possible to determine this uptake rate by measuring the number of miRNA strands after the incubation time and the miRNA/particle ratio. It should be noted that the calculated value ignores cellular degradation and release of miRNA and, thus, represents at least a lower limit for the lipoprotein particle uptake ratio.
In the future, the method can be adapted to transfer pharmaceutical substances (notably also lipophilic ones) in cells and correlate their biological effect to the intracellular concentration (determined via the uptake rate of lipoprotein particles).

Lipoprotein particles are composed of a monolayer of amphiphilic lipids and cholesterol enclosing a core of cholesteryl esters and triglyceride fats. The whole particle is stabilized by membrane-embedded apolipoproteins, which define the particle&#8217;s biological functionality. Lipoprotein particles can be distinguished according to their respective increasing density and, thus, decreasing size, namely as very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), LDL, and HDL particles. Despite the transportation of water-insoluble components in the bloodstream, it has been demonstrated that HDL particles carry noncoding strands of miRNA1,2. Micro-RNAs are a class of short (usually two dozen nucleotides) RNA strands, which degrade intracellularly complementary mRNA strands and, thereby, alter the expression profile of certain proteins3,4,5,6. Furthermore, alterations of the miRNA profile have been found in a variety of diseases and, thus, the profile is applicable as a biomarker for diagnosis and prognosis. The extracellular transport of miRNAs between cells via lipoprotein particles may serve as an additional mechanism for intercellular mRNA level modulation. To quantitatively estimate the biological effect, knowledge regarding the absolute and relative miRNA content of lipoprotein particles is needed.
Quantitative real-time PCR is a suitable and relatively quick method to gain this information. Hence, the relative quantification (RQ) value can be calculated, and relative differences between different samples and lipoprotein fractions are estimable. Multiwell microfluidic array cards are a fast and easy-to-use method to determine the relative presence (equates to the RQ value) of miRNAs in a sample. Multiwell microfluidic array cards consist of 96 or 384 individual reaction chambers for individual qPCR reactions embedded in a microfluidic device. Each chamber contains the required hydrolysis probe and specific qPCR primers for one individual miRNA. The advantages are a short handling time due to standardization, a simple workflow, and a reduced number of pipetting steps. Moreover, the required sample volume is minimized. In contrast to the relative quantification, the absolute miRNA content requires a comparison of qPCR sample results with standard curves of known absolute numbers of miRNA strands. It should be noted that, due to their relatively low miRNA content, standard and, moreover, even single-molecule sensitive imaging techniques are not feasible&#8212;the artificial enrichment of lipoprotein particles with miRNA is inevitable to study cellular lipoprotein particle interaction and miRNA transfer. Regarding this, delipidation of the HDL particle followed with subsequent relipidation7 allows the incorporation of and, thus, enrichment with miRNA strands. Similar enrichment of LDL particles with miRNA is not feasible due to the hydrophobicity of the apoB-100 protein, which is the main constituent of the LDL particle. However, by addition of the polar solvent dimethyl sulfoxide (DMSO), which is able to penetrate lipid membranes, LDL particles can be artificially loaded with miRNA strands as well.
High-speed atomic force microscopy (HS-AFM) is a powerful tool for the characterization of biological specimens offering subnanometer spatial and subsecond temporal resolution8. Hence, it is a well-suited technique for the quality control of modified lipoprotein particles as native/reconstituted/labeled lipoprotein particles can be imaged under a near-physiological environment.
Here, a qPCR-based protocol is presented step-by-step to determine the absolute/relative miRNA content of lipoprotein particles and cell samples, which allows an estimation of the cellular lipoprotein particle uptake rate. Moreover, a method for the enrichment of lipoprotein particles with miRNA is demonstrated. This method may be adapted for the general manipulation of lipoprotein content and, hence, demonstrates the applicability of lipoprotein particles as targets for drug delivery.

<table>
	<tbody>
		<tr>
			<td>Ultracentrifuge</td>
			<td>Beckman</td>
			<td>Optima L-100 XP</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Ultracentrifuge rotor</td>
			<td>Beckman</td>
			<td>TI 55.2</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Vacutainer (EDTA)</td>
			<td>Becton Dickinson</td>
			<td>366643</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Kaliumbromid</td>
			<td>Sigma Aldrich</td>
			<td>2110</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Ultracentrifuge tubes</td>
			<td>Beckman</td>
			<td>342414</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Ultracentrifuge tube sealer</td>
			<td>Beckman</td>
			<td>342428</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Sodiumchlorid</td>
			<td>Carl Roth GmbH</td>
			<td>P029.2</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Fisher Scientific</td>
			<td>D/0650/50</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>Dialysis tubes, MWCO 12 - 14k</td>
			<td>Spectra</td>
			<td>132700</td>
			<td>Lipoprotein isolation</td>
		</tr>
		<tr>
			<td>synthetic miRNA</td>
			<td>microSynth</td>
			<td>-</td>
			<td>synthetic miRNA</td>
		</tr>
		<tr>
			<td>TRIS buffer pH 7</td>
			<td>Ambion</td>
			<td>AM9850G</td>
			<td>synthetic miRNA</td>
		</tr>
		<tr>
			<td>TRIS buffer pH 8</td>
			<td>Ambion</td>
			<td>AM9855G</td>
			<td>synthetic miRNA</td>
		</tr>
		<tr>
			<td>sterile tubes</td>
			<td>Carl Roth GmbH</td>
			<td>ENE8.1</td>
			<td>synthetic miRNA</td>
		</tr>
		<tr>
			<td>Photometer</td>
			<td>Eppendorf</td>
			<td>Eppendorf Biophotometer</td>
			<td>Bradford assay</td>
		</tr>
		<tr>
			<td>Cuvette</td>
			<td>Carl Roth GmbH</td>
			<td>XK20</td>
			<td>Bradford assay</td>
		</tr>
		<tr>
			<td>Coomassie G-250 Stain</td>
			<td>BioRad GmbH</td>
			<td>161-0786</td>
			<td>Bradford assay</td>
		</tr>
		<tr>
			<td>Sodiumchlorid</td>
			<td>Carl Roth GmbH</td>
			<td>3957.1</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Fluka Analytical</td>
			<td>03690-100ML</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>TRIS buffer pH 8.0</td>
			<td>Ambion</td>
			<td>AM9855G</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>Ethanol 100%</td>
			<td>AustrAlco</td>
			<td>Ethanol Absolut 99.9%</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>Diethyl ether</td>
			<td>Carl Roth GmbH</td>
			<td>3942.1</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Thermo Scientific</td>
			<td>Multifuge X3R</td>
			<td>Delipitation</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Carl Roth GmbH</td>
			<td>3313.1</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carl Roth GmbH</td>
			<td>4627.1</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Phosphatidylcholine</td>
			<td>Sigma Aldrich GmbH</td>
			<td>P3556-25mg</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Cholesterol oleate</td>
			<td>Sigma Aldrich GmbH</td>
			<td>C-9253-250mg</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>cholesterol</td>
			<td>Sigma Aldrich GmbH</td>
			<td>C8667-500mg</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>glass tubes</td>
			<td>Carl Roth GmbH</td>
			<td>K226.1</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>spermine</td>
			<td>Sigma Aldrich GmbH</td>
			<td>S3256-1G</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Thermomixer</td>
			<td>Eppendorf</td>
			<td>Thermomixer comfort</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Sodium deoxycholate</td>
			<td>Sigma Aldrich GmbH</td>
			<td>3097-25G</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>Magnetic stir bar</td>
			<td>Carl Roth GmbH</td>
			<td>0955.2</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>100&#181;L micropipettes</td>
			<td>Carl Roth GmbH</td>
			<td>A762.1</td>
			<td>Reconstitution</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Carl Roth GmbH</td>
			<td>9143.2</td>
			<td>Dialysis</td>
		</tr>
		<tr>
			<td>Amberlite XAD-2 beads</td>
			<td>Sigma Aldrich GmbH</td>
			<td>10357</td>
			<td>Dialysis</td>
		</tr>
		<tr>
			<td>Slide-A-Lyzer casette (cut-off 20 kDa)</td>
			<td>Thermo Scientific</td>
			<td>66003</td>
			<td>Dialysis</td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>Braun</td>
			<td>9161406V</td>
			<td>Dialysis</td>
		</tr>
		<tr>
			<td>Syringe needle</td>
			<td>Braun</td>
			<td>465 76 83</td>
			<td>Dialysis</td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Carl Roth GmbH</td>
			<td>3054.2</td>
			<td>Labeling of LDL particles</td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>life technologies</td>
			<td>D12345</td>
			<td>Labeling of LDL particles</td>
		</tr>
		<tr>
			<td>Atomic Force Microscope</td>
			<td>RIBM</td>
			<td>SS-NEX</td>
			<td>Quality control of reconstituted/labeled lipoprotein particles</td>
		</tr>
		<tr>
			<td>Muscovite Mica (V-1 Grade)</td>
			<td>Christine Gr&#246;pl</td>
			<td>G250-1/V1</td>
			<td>Quality control of reconstituted/labeled lipoprotein particles</td>
		</tr>
		<tr>
			<td>AFM Cantilever</td>
			<td>Nanoworld</td>
			<td>USC-F1.2-k0.15</td>
			<td>Quality control of reconstituted/labeled lipoprotein particles</td>
		</tr>
		<tr>
			<td>Gwyddion 2.49</td>
			<td>Czech Metrology Institute</td>
			<td>http://gwyddion.net</td>
			<td>Quality control of reconstituted/labeled lipoprotein particles</td>
		</tr>
		<tr>
			<td>Chamber slides, Nunc Lab-Tek</td>
			<td>VWR</td>
			<td>734-2122</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>HBSS</td>
			<td>Carl Roth GmbH</td>
			<td>9117.1</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Cell counter</td>
			<td>Omni Life Science GmbH</td>
			<td>Casy</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>miRNeasy Mini Kit</td>
			<td>QIAGEN</td>
			<td>217004</td>
			<td>miRNA extraction</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf</td>
			<td>5415R</td>
			<td>miRNA extraction</td>
		</tr>
		<tr>
			<td>20G needle</td>
			<td>Braun</td>
			<td>Sterican 465 75 19</td>
			<td>miRNA extraction</td>
		</tr>
		<tr>
			<td>5ml syringe</td>
			<td>Becton Dickinson</td>
			<td>309050</td>
			<td>miRNA extraction</td>
		</tr>
		<tr>
			<td>PCR cabinet</td>
			<td>Esco</td>
			<td>PCR-3A1</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>TaqMan Reverse Transcription Kit</td>
			<td>Thermo Scientific</td>
			<td>4366596</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>Rnase-free water</td>
			<td>Carl Roth GmbH</td>
			<td>T143</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>0.2 ml tubes</td>
			<td>Brand</td>
			<td>781305</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Carl Roth GmbH</td>
			<td>Microcentrifuge AL</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>Thermocycler</td>
			<td>Sensoquest</td>
			<td>Labcycler</td>
			<td>Reverse Transcription</td>
		</tr>
		<tr>
			<td>TaqMan Primer</td>
			<td>Thermo Scientific</td>
			<td>-</td>
			<td>qPCR</td>
		</tr>
		<tr>
			<td>iTaq Universal probe supermix</td>
			<td>BioRad GmbH</td>
			<td>1725131</td>
			<td>qPCR</td>
		</tr>
		<tr>
			<td>PCR machine</td>
			<td>Corbett</td>
			<td>Rotor-Gene RG-6000</td>
			<td>qPCR</td>
		</tr>
		<tr>
			<td>TaqMan MicroRNA Reverse Transcription Kit</td>
			<td>Applied Biosystems</td>
			<td>4366596</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>Megaplex RT Primers, Human Pool A v2.1</td>
			<td>Applied Biosystems</td>
			<td>4399966</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>TaqMan PreAmp Master Mix</td>
			<td>Applied Biosystems</td>
			<td>4391128</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>Megaplex PreAmp Primers, Human Pool A v2.1</td>
			<td>Applied Biosystems</td>
			<td>4399933</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>TaqMan Universal Master Mix II, no UNG</td>
			<td>Applied Biosystems</td>
			<td>4440040</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>TaqMan Advanced miRNA Human A Cards</td>
			<td>Applied Biosystems</td>
			<td>A31805</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>Nuclease-free water</td>
			<td>Thermo Scientific</td>
			<td>R0581</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>MgCl2 (25mM)</td>
			<td>Thermo Scientific</td>
			<td>R0971</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>TE, pH 8.0</td>
			<td>Invitrogen</td>
			<td>AM9849</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>7900HT Fast Real-Time PCR System</td>
			<td>Applied Biosystems</td>
			<td>4351405</td>
			<td>TaqMan Array</td>
		</tr>
		<tr>
			<td>TaqMan Array Card Sealer</td>
			<td>Applied Biosystems</td>
			<td>-</td>
			<td>TaqMan Array</td>
		</tr>
	</tbody>
</table>

enrichment of native lipoprotein particles with microrna and subsequent determination of their absolute/relative microrna content and their cellular transfer rate

Lipoprotein particles are predominately transporters of lipids and cholesterol in the bloodstream. Furthermore, they contain small amounts of strands of noncoding microRNA (miRNA). In general, miRNA alters the protein expression profile due to interactions with messenger-RNA (mRNA). Thus, knowledge of the relative and absolute miRNA content of lipoprotein particles is essential to estimate the biological effect of cellular particle uptake. Here, a quantitative real-time polymerase chain reaction (qPCR)-based protocol is presented to determine the absolute miRNA content of lipoprotein particles&#8212;exemplified shown for native and miRNA-enriched lipoprotein particles. The relative miRNA content is quantified using multiwell microfluidic array cards. Furthermore, this protocol allows scientists to estimate the cellular miRNA and, thus, the lipoprotein particle uptake rate. A significant increase of the cellular miRNA level is observable when using high-density lipoprotein (HDL) particles artificially loaded with miRNA, whereas incubation with native HDL particles yields no significant effect due to their rather low miRNA content. In contrast, the cellular uptake of low-density lipoprotein (LDL) particles&#8212;neither with native miRNA nor artificially loaded with it&#8212;did not alter the cellular miRNA level.

Watch this Scientific Journal Video about Enrichment of Native Lipoprotein Particles with microRNA and Subsequent Determination of Their Absolute/Relative microRNA Content and Their Cellular Transfer 

Enrichment of Native Lipoprotein Particles with microRNA and Subsequent Determination of Their Absolute/Relative microRNA Content and Their Cellular Transfer Rate

Here, a quantitative real-time polymerase chain reaction-based protocol is presented for the determination of the native micro-RNA content (absolute/relative) of lipoprotein particles. In addition, a method for increasing the micro-RNA level, as well as a method for determining the cellular uptake rate of lipoprotein particles, is demonstrated.

Lipoprotein particles are predominately transporters of lipids and cholesterol in the bloodstream. Furthermore, they contain small amounts of strands of ...

Research

JoVE Journal

Biochemistry

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Spectrophotometric Determination of Phycobiliprotein Content in Cyanobacterium Synechocystis

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