Z. Lin was supported by National Institutes of Health HL138454-01 and Masonic Medical Research Institute funds.

All mice were maintained in pathogen-free conditions, and all procedures were approved by Masonic Medical research Institutional Animal Care and Use Committee (IACUC). UCP1::Cre9 and Rosa 26tdTomato mice lines13 were reported previously. All mice were kept at room temperature with a 12 h light/dark cycle.
1. Preparing the Solutions and brown adipose tissue (BAT)
<ol>
	<li>Prepare digestion solution and separation solution in 15 mL centrifuge tubes.</li>
	<li>10 mL of BAT Digestion solution: To 10 mL of sterile phosphate-buffered saline (PBS), add 3.5 mg/mL Dispase II, 1 mg/mL Collagenase II and 10 mM CaCl2 to make BAT digestion solution.</li>
	<li>10 mL of 12% iodixanol solution (separation solution): Mix 1 mL of 10x PBS, 2 mL of 60% iodixanol, 0.01 mL of 1 M MgCl2, 0.025 mL of 1 M KCl, 0.1 mL of 0.2 M ethylenediaminetetraacetic acid (EDTA) and 6.865 mL of ddH2O to obtain 12% iodixanol.</li>
	<li>Euthanize one adult mouse with CO2 overdose. Briefly, fill the mouse cage with 100% CO2 at a displacement rate of 10-30% cage volume per min. 5 min later, confirm death by checking for the absence of visibly breathing.</li>
	<li>Dissect the animal and collect interscapular BAT. Remove WAT and muscle layers under a stereo microscope.</li>
	<li>To have sufficient digestion, cut each BAT lobe into ~ 3 mm3 parts and place them into a clean 50 mL flask with a metal stir bar and 5 mL digestion solution. Before starting digestion, let the flask containing BAT and digestion buffer sit on ice for 1 h. 
	&#8203;NOTE: In the following steps, around 80 mg BAT was used for brown adipocytes isolation.</li>
</ol>
2. BAs isolation procedure
<ol>
	<li>Place the flask on a magnetic stirrer that is enclosed in an incubator. Set the stirring speed at 60 rpm and the temperature of the incubator at 35 &#176;C, respectively. The digestion will last for around 30 min. If the BAT slices form clumps around the stirrer bar during digestion, use a 1 mL pipette tip to disrupt the aggregated tissues.</li>
	<li>Place a 70 &#181;m strainer filter on top of a clean 50 mL centrifuge tube. Pipette around 4 mL cell suspension through the strainer. Wash the strainer with 4 mL of 12% iodixanol solution. Pipette up and down to mix the cells and the iodixanol solution. Transfer the cell mixture into two clear 5 mL polystyrene test tubes. 
	NOTE: At the end of digestion, the digestion solution should be cloudy, indicating sufficient digestion. Use fresh digestion solution every time. Once prepared, the digestion solution should be used within 2 h.</li>
	<li>Repeat step 2.2 and 2.3 once more if the digestion is not sufficient.</li>
	<li>Leave the clear polystyrene tubes containing the separation solution and BAs on ice for 1 h. The BAs will form a layer on the top.</li>
	<li>Take out 20 &#181;L of the isolated BAs for microscope examination.</li>
</ol>
3. RNA and protein isolation from BAs
<ol>
	<li>Pipette the BAs layer into two 1.7 mL microcentrifuge tubes for RNA and protein isolation. Carefully remove the excessive iodixanol solution without disrupting the BAs layer.</li>
	<li>Add 1 mL Trizol&#160;to simultaneously isolate RNA, DNA, and protein into the cell solution. Mix sufficiently to lyse the cells.</li>
	<li>Add 200 &#181;L of Chloroform to separate the phases.</li>
	<li>Centrifuge the tube for 9,981 x g for 10 min at 4 &#176;C.</li>
	<li>After centrifugation, use the aqueous phase for RNA isolation. In this study, total RNA was used for reverse transcription, and quantitative RT-PCR was carried out with Real-Time PCR. Primer sequences are listed in Table of Materials.</li>
	<li>Transfer 300 &#181;L of the organic phase into a 2 mL microcentrifuge tube.</li>
	<li>To the organic&#160;phase, add 2.5 volume 100% ethanol and vortex for 10 s.</li>
	<li>Add 200 &#181;L of 1-Bromo-3-chloropropane and vortex for 10 s.</li>
	<li>Add 600 &#181;L of double distilled water and vortex for 10 s.</li>
	<li>Let the mixed solution stand for 10 min at room temperature.</li>
	<li>Centrifuge at 9,981 x g for 10 min at 4 &#176;C. At this step, the phases will be separated. The protein phase is localized in the middle layer.</li>
	<li>Remove the top aqueous solution. Add 1 mL 100% ethanol into the remaining solution.</li>
	<li>Centrifuge for 10 min, 9,981 x g, 4 &#176;C. After centrifugation, the protein pellet will form. Discard the supernatant.</li>
	<li>Wash the pellet with 1 mL 100% ethanol.</li>
	<li>Centrifuge for 10 min, 9981 x g, 4 &#176;C. Save the pellet and discard the supernatant.</li>
	<li>Air-dry the pellet for 10 min at room temperature.</li>
	<li>Measure the weight of the wet pellet. Add in 1% SDS solution at a ratio of 20 &#181;L/mg pellet.</li>
	<li>Dissolve the pellet by putting the tube in a heated shaker. Set the temperature at 55 &#176;C, and the speed at 11 x g. It usually takes 5-10 min to completely dissolve the protein pellet. 
	NOTE: The concentration of the dissolved protein can be measured by BCA assay14.</li>
</ol>

<ol>
	<li>Zwick, R. K., Guerrero-Juarez, C. F., Horsley, V., Plikus, M. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomical,+physiological,+and+functional+diversity+of+adipose+tissue.">Anatomical, physiological, and functional diversity of adipose tissue.</a> Cell Metabolism. 27, 68-83 (2018).</li><li>Symonds, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brown+adipose+tissue+growth+and+development.">Brown adipose tissue growth and development.</a> Scientifica. 2013, 305763 (2013).</li><li>Giralt, M., Villarroya, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=White,+brown,+beige/brite:+Different+adipose+cells+for+different+functions.">White, brown, beige/brite: Different adipose cells for different functions.</a> Endocrinology. 154, 2992-3000 (2013).</li><li>Cannon, B., Nedergaard, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brown+adipose+tissue:+function+and+physiological+significance.">Brown adipose tissue: function and physiological significance.</a> Physiological Reviews. 84, 277-359 (2004).</li><li>Cinti, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+adipose+organ.">The adipose organ.</a> Prostaglandins, Leukotrienes and Essential Fatty Acids. 73, 9-15 (2005).</li><li>Wu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beige+adipocytes+are+a+distinct+type+of+thermogenic+fat+cell+in+mouse+and+human.">Beige adipocytes are a distinct type of thermogenic fat cell in mouse and human.</a> Cell. 150, 366-376 (2012).</li><li>Cypess, A. 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P., Ussar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterogeneity+of+adipose+tissue+in+development+and+metabolic+function.">Heterogeneity of adipose tissue in development and metabolic function.</a> Journal of Experimental Biology. 221, (2018).</li><li>Kong, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IRF4+is+a+key+thermogenic+transcriptional+partner+of+PGC-1&#945;.">IRF4 is a key thermogenic transcriptional partner of PGC-1&#945;.</a> Cell. 158, 69-83 (2014).</li><li>Lee, Y. H., Petkova, A. P., Konkar, A. A., Granneman, J. 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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+cytometry+of+mouse+and+human+adipocytes+for+the+analysis+of+browning+and+cellular+heterogeneity.">Flow cytometry of mouse and human adipocytes for the analysis of browning and cellular heterogeneity.</a> Cell Report. 24, 2746-2756 (2018).</li><li>Madisen, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+robust+and+high-throughput+Cre+reporting+and+characterization+system+for+the+whole+mouse+brain.">A robust and high-throughput Cre reporting and characterization system for the whole mouse brain.</a> Nature Neuroscience. 13, 133-140 (2010).</li><li>Smith, P. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+method+for+simultaneous+isolation+of+proteins+and+nucleic+acids.">Improved method for simultaneous isolation of proteins and nucleic acids.</a> Analytical Biochemistry. 411, 164-166 (2011).</li><li>Ford, T., Graham, J., Rickwood, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Iodixanol:+A+nonionic+iso-osmotic+centrifugation+medium+for+the+formation+of+self-generated+gradients.">Iodixanol: A nonionic iso-osmotic centrifugation medium for the formation of self-generated gradients.</a> Analytical Biochemistry. 220, 360-366 (1994).</li><li>Kovacovicova, K., Vinciguerra, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+senescent+cells+by+iodixanol+(OptiPrep)+density+gradient-based+separation.">Isolation of senescent cells by iodixanol (OptiPrep) density gradient-based separation.</a> Cell Proliferation. 52, 12674 (2019).</li><li>Lock, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=versatile+manufacturing+of+recombinant+adeno-associated+viral+vectors+at+scale.">versatile manufacturing of recombinant adeno-associated viral vectors at scale.</a> Human Gene Therapy. 21, 1259-1271 (2010).</li><li>Marin, R. 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In this study, a new method of isolating BAs for gene and protein expression analysis was developed.
In a published BAs isolation protocol, 3% BSA solution was used to enrich BAs12. Nevertheless, the enriched BAs achieved by this published protocol could not be directly used for protein expression analysis. This is because the concentrated BSA existing in the BAs solution interferes with following-up protein extraction. When the BAs enriched in the 3% BSA solution were treated with Trizol reagent, sticky protein aggregates would form, the majority of which was not soluble in the GTPC protein extraction process. Additionally, in the GTPC protein extraction product, most of the protein was BSA (Figure 3B). In this new protocol, 3% BSA separation solution was replaced with 6% iodixanol for purifying BAs. 6% iodixanol solution efficiently separated the BAs from non-BAs, and the isolated BAs had preserved morphology (Figure 3D). Superior to 3% BSA solution, 6% iodixanol solution did not interfere with protein extraction, and the extracted protein was suitable for western blot analysis (Figure 4C,D).
Adipose tissue contains large amount of lipids, and lipids contamination in extracted protein samples obstructs protein concentration measurement. Recently, a protocol to remove lipids from protein extractions has been published. In this protocol, a series of low temperature centrifugations are required, which is tedious and needs a large amount of starting materials19. In the current study, an improved GTPC method15 was adopted to isolate protein from BAT. Different from the classical GTPC protocol, this improved GTPC protocol used ethanol, bromo-chloropropane and water to extract protein out of the organic phase. Our data showed that protein isolated with this improved GTPC method was compatible with bicinchoninic acid assay (BCA) based protein concentration measurement.
In the current BAs isolation protocol, before the start of the enzyme dissociation process, the BAT and digestion solution mixture were placed on ice for one hour. The purpose of this procedure is to reduce the cell metabolism and gene expression rate20, as well as to let the digestion enzymes efficiently perfuse into the brown adipose tissue.
The current study aimed to develop a straitforward method to isolate brown adiopocytes from interscapular BAT for gene expression study; however, white adipocytes contamination may exist in the isolated BAs. This is because interscapular BAT is sometimes attached by white adipose tissue, which cannot be completely removed during the BAT preparation step. The current protocol cannot separate BAs from WAs based on cell density. Therefore, if very high purity is essential, the isolated BAs need to be sorted by FACS before being analyzed.
The interscapular BAT (iBAT) contains abundant classical BAs that derived from the Myf5 cell lineage during embryonic development21. Here iBAT was used as an example for isolating BAs. Similar with the published protocol12, our method can also be used for isolating beige cells from WAT. Nevertheless, to acquire pure beige cells from WAT, the beige cells need to be labeled with fluorescence protein and be enriched by FACS. Following our current protocol, the FACS enriched beige cells can be used for both gene and protein expression analysis, which will greatly improve the efficiency of biological materials utilization.

Both mice and humans have two types of adipose tissues: white adipose tissue (WAT) and brown adipose tissue (BAT)1. WAT stores energy in the form of triglycerides in white adipocytes, and the brown adipocytes (BAs) of BAT dissipate chemical energy as heat2. Based on their developmental origin, BAs are further categorized into classical BAs (cBAs) that formed during embryo development and white adipocytes derived BAs (beige/brite cells, converted from white adipocytes under stress conditions)3. BAs are multilocular and express the thermogenic protein uncoupling protein 1 (UCP1)4. Interscapular BAT (iBAT) depot is one of the primary cBAs depots in small mammals5, whereas beige cells are dispersed within WAT6. 
Due to their nature of dissipating energy, BAs have received much attention as a therapeutic target for reducing obesity7. To exploit BAs for the purpose of treating obesity, it is essential to understand the molecular mechanisms that control BAs function, survival, and recruitment. Adipose tissues including BAT and WAT are heterogeneous. Except for adipocytes, adipose tissues contain many other cell types, such as endothelial cells, mesenchymal stem cells and macrophages8. Although genetic tools to specifically deplete candidate genes in mice BAs are available, such as UCP1::Cre line9, techniques for purifying BAs from BAT or WAT are limited, making it hard to study BAs at a single-cell type level. Additionally, without obtaining pure BAs, the relationship between BAs and non-BAs will not be clearly delineated. For instance, platelet-derived growth factor receptor alpha (PDGFR&#945;) has been used as a marker for undifferentiated mesenchymal cells, and it is expressed in the endothelial and interstitial cells of BAT. In cold stressed BAT, PDGFR&#945; positive progenitor cells give rise to new BAs10. PDGFR&#945; is activated by its ligand PDGF, a growth factor that regulates the growth and proliferation of mesenchymal cells11; however, it is unclear whether BAs influence the behavior of PDGFR&#945; positive progenitor cells by secreting PDGF. 
Recently, a BAs isolation protocol has been published, which is based on fluorescence-activated cell sorting (FACS)12. In this protocol, 3% bovine serum albumin (BSA) solution was used to separate BAs from non-BAs, and the enriched BAs were further purified by FACS. The application of this protocol is limited by the requirement of FACS process, which relies on both equipment and FACS operation experiences. In this study, a new protocol for isolating BAs from BAT was developed. The BAs isolated by this protocol can be directly used for gene and protein expression studies. Furthermore, data from this study suggest that BAs are a major PDGF resource.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antibodies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Antigen</td>
			<td>Company</td>
			<td>Catalog</td>
			<td></td>
		</tr>
		<tr>
			<td>PPAR&#947;</td>
			<td>LSBio</td>
			<td>Ls-C368478</td>
			<td></td>
		</tr>
		<tr>
			<td>PDGFRa</td>
			<td>Santa Cruz</td>
			<td>sc-398206</td>
			<td></td>
		</tr>
		<tr>
			<td>UCP1</td>
			<td>R&#38;D system</td>
			<td>IC6158P</td>
			<td></td>
		</tr>
		<tr>
			<td>Chemical and solutions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase, Type II</td>
			<td>Thermo Fisher Scientific</td>
			<td>17101015</td>
			<td></td>
		</tr>
		<tr>
			<td>1-Bromo-3-chloropropane</td>
			<td>Sigma-Aldrich</td>
			<td>B62404</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)&#160;</td>
			<td>Goldbio</td>
			<td>A-421-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Bio Basic</td>
			<td>CT1330</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>IBI Scientific</td>
			<td>IB05040</td>
			<td></td>
		</tr>
		<tr>
			<td>Dispase II, protease</td>
			<td>Sigma-Aldrich</td>
			<td>D5693</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Bio Basic</td>
			<td>EB0107</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>IBI Scientific</td>
			<td>IB15724</td>
			<td></td>
		</tr>
		<tr>
			<td>LiQuant Universal Green qPCR Master Mix</td>
			<td>LifeSct</td>
			<td>LS01131905Y</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium Chloride Hexahydrate</td>
			<td>Boston BioProducts</td>
			<td>P-855</td>
			<td></td>
		</tr>
		<tr>
			<td>OneScrip Plus cDNA Synthesis SuperMix</td>
			<td>ABM</td>
			<td>G454</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiPrep (Iodixanol)</td>
			<td>Cosmo Bio USA</td>
			<td>AXS-1114542</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (10x)</td>
			<td>Caisson Labs</td>
			<td>PBL07</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (1x)</td>
			<td>Caisson Labs</td>
			<td>PBL06</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce BCA Protein Assay Kit</td>
			<td>Thermo Fisher Scientific</td>
			<td>23227</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Boston BioProducts</td>
			<td>P-1435</td>
			<td></td>
		</tr>
		<tr>
			<td>SimplyBlue safe Stain</td>
			<td>Invitrogen</td>
			<td>LC6060</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate (SDS)</td>
			<td>Sigma-Aldrich</td>
			<td>75746</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizol reagent</td>
			<td>Life technoologies</td>
			<td>15596018</td>
			<td></td>
		</tr>
		<tr>
			<td>Primers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gene name (Species)&#160;</td>
			<td>Forward</td>
			<td>Reverse</td>
			<td></td>
		</tr>
		<tr>
			<td>Pdgfra (Mouse)</td>
			<td>CTCAGCTGTCTCCTCACAgG</td>
			<td>CAACGCATCTCAGAGAAAAGG</td>
			<td></td>
		</tr>
		<tr>
			<td>Pdgfa (Mouse)</td>
			<td>TGTGCCCATTCGCAGGAAGAG</td>
			<td>TTGGCCACCTTGACACTGCG</td>
			<td></td>
		</tr>
		<tr>
			<td>36B4(Mouse)</td>
			<td>TGCTGAACATCTCCCCCTTCTC</td>
			<td colspan="2">TCTCCACAGACAATGCCAGGAC</td>
		</tr>
		<tr>
			<td>Ucp1</td>
			<td>ACTGCCACACCTCCAGTCATT</td>
			<td>CTTTGCCTCACTCAGGATTGG</td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Application</td>
			<td></td>
		</tr>
		<tr>
			<td>Keyence BZ-X700</td>
			<td>Keyence</td>
			<td colspan="2">Imaging brown adipocytes</td>
		</tr>
		<tr>
			<td>Magnetic stirrer</td>
			<td>VWR</td>
			<td>Dissociate BAT</td>
			<td></td>
		</tr>
		<tr>
			<td>QuantStudio 6 Flex Real-Time PCR System</td>
			<td>Applied Biosystem</td>
			<td>Quantitative PCR</td>
			<td></td>
		</tr>
		<tr>
			<td>The Odyssey Fc Imaging system</td>
			<td>LI-COR</td>
			<td>Western blot immaging</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolating brown adipocytes from murine interscapular brown adipose tissue for gene and protein expression analysis

Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis in mammals, and brown adipocytes (BAs) are the functional units of BAT. BAs contain both multilocular lipid droplets and abundant mitochondria, and they express uncoupling protein 1 (UCP1). BAs are categorized into two sub-types based on their origin: embryo derived classical BAs (cBAs) and white adipocytes derived BAs. Due to their relatively low density, BAs cannot be isolated from BAT with traditional centrifugation method. In this study, a new method was developed to isolate BAs from mice for gene and protein expression analysis. In this protocol, interscapular BAT from adult mice was digested with Collagenase and Dispase solution, and the dissociated BAs were enriched with 6% iodixanol solution. Isolated BAs were then lysed with Trizol&#160;reagent for simultaneous isolation of RNA, DNA, and protein. After RNA isolation, the organic phase of the lysate was used for protein extraction. Our data showed that 6% iodixanol solution efficiently enriched BAs without interfering with follow-up gene and protein expression studies. Platelet-derived growth factor (PDGF) is a growth factor that regulates the growth and proliferation of mesenchymal cells. Compared to the brown adipose tissue, isolated BAs had significantly higher expression of Pdgfa. In summary, this new method provides a platform for studying the biology of brown adipocytes at a single cell-type level.

Preparation of interacapular BAT for brown adipocytes isolation 
The brown adipocytes (BAs) isolation process is depicted in Figure 1A. The whole process, from preparing BAT and digestion/separation solutions to obtaining isolated BAs will take around 4 h.
In adult mice, abundant BAT exists in the interscapular region. This interscapular BAT (iBAT) is covered by muscle layers and WAT (Figure 1B). Before starting the digestion procedure, the muscle layers and WAT need to be removed to yield out clean iBAT (Figure 1C). In a published BAs isolation protocol, minced BAT was used for BAs isolation12. In this study, digestion of 3 mm3 size BAT (Figure 1D) yielded out more BAs than minced BAT.
Separation of BAs from non-BAs with 3% BSA solution 
After iBAT digestion, dissociated BAs were mixed with non-BAs in the digestion product. Because BAs contain lipid droplets, their density is lower than non-BAs; however, the BAs density is not low enough to let them efficiently float to the top of a regular PBS solution. PBS containing 3% bovine serum albumin (BSA) has been used to separate BAs from non-BAs12, which was successfully repeated in this study (Figure 2A).
Rosa 26tdTomato is a reporter mouse line, which expresses strong tdTomato (tdTom) fluorescence protein following Cre-mediated recombination13. Ucp1::Cre transgenic mice express Cre recombinase in the BAs9. Ucp1::Cre mouse line was crossed with Rosa 26tdTomato mice to genetically label BAs with tdTom (Figure 2B). For validating the BAs isolation procedure, iBAT from Ucp1::Cre;tdTom/+ mice was dissociated. Most of the cells enriched in the top layer of BSA solution were raspberry shape and contained multilocular lipid droplets. Furthermore, most of these raspberry shape cells were tdTom positive (Figure 2C), confirming that they were brown adipocytes.
Separation of BAs from non-BAs with 6% iodixanol solution 
3% BSA separation solution enriched BAs. It was unclear whether these isolated BAs could be used for gene and protein expression analysis. RNA and protein were then extracted from the enriched BAs. RNA extraction was successfully performed according to the standard RNA isolation procedure. However, the standard Trizol protein isolation protocol, also known as Guanidinium thiocyanate-phenol-chloroform method (GTPC method), did not work well, which was tedious and had very low protein yield. Therefore, an improved protein isolation method was adopted to extract protein from Trizol-lysed BAs.
In this improved GTPC protocol, ethanol, bromo-chloropropane, and water was used for extracting protein from the organic phase15. After adding ethanol, bromo-chloropropane and water into the organic phase, and after centrifugation, protein pellet formed between the aqueous phase and the organic phase (Figure 3A). Protein pellet was then washed with 100% ethanol and dissolved in 1% SDS. This improved GTPC method was used to extract protein from iBAT and BSA solution-enriched BAs. Although the BAT protein pellet was easily dissolved in 1% SDS, major part of the isolated-BAs protein pellet was not soluble. Then the dissolved protein was examined with SDS-PAGE gel. As shown in a Coomassie blue stained SDS-PAGE gel (Figure 3B), a massive protein band around 60 kDa was present in the isolated BAs but not in the BAT samples. Because the molecular weight of BSA is 66 kDa, and abundant BSA exists in the BAs separation solution, this dominant protein band should be BSA. These data suggest that the BSA from the BAs separation solution interferes with protein extraction.
Iodixanol is a nonionic and iso-osmotic gradient medium16 that has been widely used for cell17 and adeno-associated virus (AAV) purification18. To avoid BSA interference of protein expression studies, iodixanol was used to replace BSA in a new BAs separation solution. 3% BSA solution has a density of 1.03, which is similar with 6% iodixanol. In 6% iodixanol solution, BAs floated to the top in 30-60 min (Figure 3C). The BAs isolated with this solution showed out typical raspberry shape and contained multilocular lipid droplets (Figure 3D). Proteins extracted from these isolated BAs were nicely separated in SDS-PAGE gel (Figure 3E).
To verify whether the 6% iodixanol solution efficiently separated BAs from non-BAs, we genetically labeled the BAs with tdTom and examined the cells residing in the clear 6% iodixanol solution. After separating the BAs from non-BAs (step 2.4), the 6% iodixanol solution below the BAs layer was diluted 6 times with PBS and was then centrifuged at 600 x g for 5 min. After centrifugation, a small red cell pellet was formed on the bottom, which might be stromal vascular fraction cells. As shown in Figure 3, cells from the BAs layer were tdTom positive cells (Figure 3F); however, cells recovered from the pellet were tdTom negative (Figure 3G). Additionally, no obvious lipid droplets were visible in the tdTom negative cells. These data suggest that our new protocol can efficiently separate the BAs from the non-fat cells.
Together, these data demonstrate that isolating BAs with 3% BSA solution interferes with following-up biochemistry studies and suggest that 6% iodixanol solution is better than 3% BSA solution for isolating BAs.
Gene and protein expression analysis with isolated BAs. 
For validating this new BAs isolation procedure on molecular level, the expression of three genes was compared between BAT and isolated BAs: Ucp1, Pdgfa and Pdgfra. In BAT, Pdgfra is expressed in endothelial cells and interstitial cells, and PDGFR&#945; positive cells are putative progenitor cells10. The mRNA levels of Ucp1 and Pdgfa were both significantly higher in the isolated BAs than in the BAT (Figure 4A,B). On the contrary, the mRNA of Pdgfra was only detected in BAT (Figure 4B).
PPAR&#947; is a transcriptional factor controlling adipose tissue development, UCP1 is a mitochondria protein, and PDGFR&#945; is a membrane receptor protein. These three proteins represent proteins distributed in different cellular compartments. Western blots were performed to test whether protein extracted from Trizol-lysed BAs and BAT was suitable for protein expression analysis. UCP1 and PPAR&#947; were detected in both BAs and BAT (Figure 4C,D), confirming that the total protein isolated from the Trizol-lysed BAs or BAT is suitable for western blot. Furthermore, consistent with the qRT-PCR results, UCP1 protein was enriched in BAs (Figure 4C); whereas PDGFR&#945; was only detected in BAT but not in pure BAs (Figure 4D). In summary, these data demonstrate that our new BAs isolation method is efficient and suggest that BAs enriched by this method can be directly used for gene and protein expression studies.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62332/62332fig01.jpg" /> 
Figure 1: Preparation of iBAT for brown adipocytes isolation. (A)&#160;Workflow of the brown adipocytes isolation procedure. (B)&#160;Ventral view of the interscapular tissue containing BAT, WAT and muscle layers. (C)&#160;Interscapular BAT (iBAT). Muscle layers and WAT adjacent to iBAT were removed. (D)&#160;A representative image of iBAT pieces used for brown adipocytes isolation. B-D, Scale bar= 5 mm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62332/62332fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62332/62332fig02.jpg" /> 
Figure 2: Separation of brown adipocytes from digestion solution. (A)&#160;Images of dissociated brown adipocytes before and after separation. 3% BSA solution was used to separate brown adipocytes from non-brown adipocytes. Scale bar = 1 cm. (B)&#160;Schematic view of genetic labeling brown adipocytes with tdTomato fluorescence protein. (C)&#160;Images of isolated brown adipocytes. DIC, differential interference contrast. Scale bar = 50 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62332/62332fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/62332/62332fig03.jpg" /> 
Figure 3: Extraction of total protein from lysed brown adipocytes. (A)&#160;Separation of protein phase from the organic phase. (B)&#160;Coomassie staining of SDS-PAGE gel. Total protein was extracted from BAT or 3% BSA solution purified brown adipocytes. BSA protein band was indicated by an arrow. (C)&#160;Brown adipocytes layer formed on top of 6% iodixanol solution. Scale bar = 1 cm. (D)&#160;Brown adipocytes isolated with 6% iodixanol solution. Brown adipocytes were indicated by yellow arrows. Scale bar = 50 &#181;m. (E)&#160;Coomassie staining of SDS-PAGE gel. Total protein was extracted from BAT or 6% iodixanol solution enriched BAs. (F) Images of tdTom labeled brown adipocytes. (G) Images of cells recovered from the iodixanol solution below the BAs layer. F and G, scale bar = 50 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62332/62332fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/62332/62332fig04.jpg" /> 
Figure 4: Gene and protein expression analysis of isolated brown adipocytes. Brown adipocytes isolated with the iodixanol method was used in these gene and protein expression studies. (A,B) qRT-PCR measurement of gene expression. mRNA levels were normalized to 36B4. N=3. Student t test, *, P&#60;0.01; **, P&#60;0.01. (C)&#160;Western blotting of PPAR&#947; and UCP1. (D)Western blotting of PDGFR&#945;. C and D, Ponceau S-stained membrane was used as loading control.&#160;<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62332/62332fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Isolating Brown Adipocytes from Murine Interscapular Brown Adipose Tissue for Gene and Protein Expression Analysis at JoVE.com

Isolating Brown Adipocytes from Murine Interscapular Brown Adipose Tissue for Gene and Protein Expression Analysis

This study describes a new method of isolating murine brown adipocytes for gene and protein expression analysis.

Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis in mammals, and brown adipocytes (BAs) are the functional units of BAT. BAs ...

isolating-brown-adipocytes-from-murine-interscapular-brown-adipose

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

5.2K Views.  Masonic Medical Research Institute. This study describes a new method of isolating murine brown adipocytes for gene and protein expression analysis.

Video: Isolating Brown Adipocytes from Murine Interscapular Brown Adipose Tissue for Gene and Protein Expression Analysis

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &beta;-arrestin

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to intracellular responses. GPCRs control diverse biological functions such as chemotaxis, intracellular calcium release, gene regulation in a ligand dependent manner via heterotrimeric G-proteins1-2. Ligand binding induces a series of conformational changes leading to activation of heterotrimeric G-proteins that modulate levels of second messengers such as cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3) and diacyl glycerol (DG). Concomitant with activation of the receptor ligand binding also initiates a series of events to attenuate the receptor signaling via desensitization, sequestration and/or internalization. The desensitization process of GPCRs occurs via receptor phosphorylation by G-protein receptor kinases (GRKs) and subsequent binding of &beta;-arrestins3. &beta;-arrestins are cytosolic proteins and translocate to membrane upon GPCR activation, binding to phosphorylated receptors (most cases) there by facilitating receptor internalization 4-6.
Leukotriene B4 (LTB4) is a pro-inflammatory lipid molecule derived from arachidonic acid pathway and mediates its actions via GPCRs, LTB4 receptor 1 (BLT1; a high affinity receptor) and LTB4 receptor 2 (BLT2; a low affinity receptor)7-9. The LTB4-BLT1 pathway has been shown to be critical in several inflammatory diseases including, asthma, arthritis and atherosclerosis10-17. The current paper describes the methodologies developed to monitor LTB4-induced leukocyte migration and the interactions of BLT1 with &beta;-arrestin and , receptor translocation in live cells using microscopy imaging techniques18-19.
Bone marrow derived dendritic cells from C57BL/6 mice were isolated and cultured as previously described 20-21. These cells were tested in live cell imaging methods to demonstrate LTB4 induced cell migration. The human BLT1 was tagged with red fluorescent protein (BLT1-RFP) at C-terminus and &beta;-arrestin1 tagged with green fluorescent protein (&beta;-arr-GFP) and transfected the both plasmids into Rat Basophilic Leukomia (RBL-2H3) cell lines18-19. The kinetics of interaction between these proteins and localization were monitored using live cell video microscopy. The methodologies in the current paper describe the use of microscopic techniques to investigate the functional responses of G-protein coupled receptors in live cells. The current paper also describes the use of Metamorph software to quantify the fluorescence intensities to determine the kinetics of receptor and cytosolic protein interactions.

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &#946;-arrestin

This paper describes the methodology to determine the chemotactic response of leukocytes to specific ligands and identify interactions between the cell surface receptors and cytosolic proteins using live cell imaging techniques.

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to ...

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

Differentiating Functional Roles of Gene Expression from Immune and Non-immune Cells in Mouse Colitis by Bone Marrow Transplantation

To understand the role of a gene in the development of colitis, we compared the responses of wild-type mice and gene-of-interest deficient knockout mice to colitis. If the gene-of-interest is expressed in both bone marrow derived cells and non-bone marrow derived cells of the host; however, it is possible to differentiate the role of a gene of interest in bone marrow derived cells and non- bone marrow derived cells by bone marrow transplantation technique. To change the bone marrow derived cell genotype of mice, the original bone marrow of recipient mice were destroyed by irradiation and then replaced by new donor bone marrow of different genotype. When wild-type mice donor bone marrow was transplanted to knockout mice, we could generate knockout mice with wild-type gene expression in bone marrow derived cells. Alternatively, when knockout mice donor bone marrow was transplanted to wild-type recipient mice, wild-type mice without gene-of-interest expressing from bone marrow derived cells were produced. However, bone marrow transplantation may not be 100% complete. Therefore, we utilized cluster of differentiation (CD) molecules (CD45.1 and CD45.2) as markers of donor and recipient cells to track the proportion of donor bone marrow derived cells in recipient mice and success of bone marrow transplantation. Wild-type mice with CD45.1 genotype and knockout mice with CD45.2 genotype were used. After irradiation of recipient mice, the donor bone marrow cells of different genotypes were infused into the recipient mice. When the new bone marrow regenerated to take over its immunity, the mice were challenged by chemical agent (dextran sodium sulfate, DSS 5%) to induce colitis. Here we also showed the method to induce colitis in mice and evaluate the role of the gene of interest expressed from bone-marrow derived cells. If the gene-of-interest from the bone derived cells plays an important role in the development of the disease (such as colitis), the phenotype of the recipient mice with bone marrow transplantation can be significantly altered. At the end of colitis experiments, the bone marrow derived cells in blood and bone marrow were labeled with antibodies against CD45.1 and CD45.2 and their quantitative ratio of existence could be used to evaluate the success of bone marrow transplantation by flow cytometry. Successful bone marrow transplantation should show a vast majority of donor genotype (in term of CD molecule marker) over recipient genotype in both the bone marrow and blood of recipient mice.

Bone marrow transplantation provides a way to change the genotype of the bone marrow derived cells. If the gene of interest is expressed in both bone marrow derived cells and non-bone marrow derived cells, bone marrow transplantation can change the bone marrow derived cells to a different genotype without changing the non-bone marrow derived cell genotype.

To understand the role of a gene in the development of colitis, we compared the responses of wild-type mice and gene-of-interest deficient knockout mice ...

Isolating And Immunostaining Lymphocytes and Dendritic Cells from Murine Peyer's Patches

Peyer's patches (PPs) are integral components of the gut-associated lymphoid tissues (GALT) and play a central role in intestinal immunosurveillance and homeostasis. Particulate antigens and microbes in the intestinal lumen are continuously sampled by PP M cells in the follicle-associated epithelium (FAE) and transported to an underlying network of dendritic cells (DCs), macrophages, and lymphocytes. In this article, we describe protocols in which murine PPs are (i) dissociated into single cell suspensions and subjected to flow cytometry and (ii) prepared for cryosectioning and immunostaining. For flow cytometry, PPs are mechanically dissociated and then filtered through 70 &mu;m membranes to generate single cell suspensions free of epithelial cells and large debris. Starting with 20-25 PPs (from four mice), this quick and reproducible method yields a population of &gt;2.5 x 106 cells with &gt;90% cell viability. For cryosectioning, freshly isolated PPs are immersed in Optimal Cutting Temperature (OCT) medium, snap-frozen in liquid nitrogen, and then sectioned using a cryomicrotome. Tissue sections (5-12 &mu;m) are air-dried, fixed with acetone or methanol, and then subjected to immunolabeling.

There is an increasing interest in understanding the immunological functions of specific subpopulations of cells in Peyer's patches (PPs), the primary inductive sites of gut-associated lymphoid tissues. Here we outline parallel protocols for preparing PP single cell preparations for flow cytometric analysis and PP cryosections for immunostaining.

Peyer's  patches (PPs) are integral components of the gut-associated lymphoid tissues  (GALT) and play a central role in intestinal immunosurveillance and ...

Isolation of Adipose Tissue Immune Cells

The discovery of increased macrophage infiltration in the adipose tissue (AT) of obese rodents and humans has led to an intensification of interest in immune cell contribution to local and systemic insulin resistance. Isolation and quantification of different immune cell populations in lean and obese AT is now a commonly utilized technique in immunometabolism laboratories; yet extreme care must be taken both in stromal vascular cell isolation and in the flow cytometry analysis so that the data obtained is reliable and interpretable. In this video we demonstrate how to mince, digest, and isolate the immune cell-enriched stromal vascular fraction. Subsequently, we show how to antibody label macrophages and T lymphocytes and how to properly gate on them in flow cytometry experiments. Representative flow cytometry plots from low fat-fed lean and high fat-fed obese mice are provided. A critical element of this analysis is the use of antibodies that do not fluoresce in channels where AT macrophages are naturally autofluorescent, as well as the use of proper compensation controls.

Adipose tissue (AT) is a site of intense immune cell activation and interaction. Almost all cells of the immune system are present in AT and their ratios are altered by obesity. Proper isolation, quantification, and characterization of AT immune cell populations are critical for understanding their role in immunometabolic disease.

The discovery of increased macrophage infiltration in  the adipose tissue (AT) of obese rodents and humans has led to an  intensification of interest in ...

Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation

During infection and inflammation, circulating monocytes leave the bloodstream and migrate into tissues, where they differentiate into macrophages. Macrophages express surface Toll-like receptors (TLRs), which recognize molecular patterns conserved through evolution in a wide range of microorganisms. TLRs play a central role in macrophage activation which is usually associated with gene expression alteration. Macrophages are critical in many diseases and have emerged as attractive targets for therapy. In the following protocol, we describe a procedure to isolate murine peritoneal macrophages using Brewer&#8217;s thioglycollate medium. The latter will boost monocyte migration into the peritoneum, accordingly this will raise macrophage yield by 10-fold. Several studies have been carried out using bone marrow, spleen or peritoneal derived macrophages. However, peritoneal macrophages were shown to be more mature upon isolation and are more stable in their functionality and phenotype. Thus, macrophages isolated from murine peritoneal cavity present an important cell population that can serve in different immunological and metabolic studies. Once isolated, macrophages were stimulated with different TLR ligands and consequently&#160;gene expression was evaluated.

We describe here a simple protocol to isolate murine peritoneal macrophages. This procedure is followed by RNA extraction to carry out gene expression analysis upon Toll-like receptors stimulation.

During infection and inflammation, circulating monocytes leave the bloodstream and migrate into tissues, where they differentiate into macrophages. ...

Qualitative and Quantitative Assays for Detection and Characterization of Protein Antimicrobials

Initial evaluations of large microbial libraries for potential producers of novel antimicrobial proteins require both qualitative and quantitative methods to screen for target enzymes prior to investing greater research effort and resources. The goal of this protocol is to demonstrate two complementary assays for conducting these initial evaluations. The microslide diffusion assay provides an initial or simple detection screen to enable the qualitative and rapid assessment of proteolytic activity against an array of both viable and heat-killed bacterial target substrates. As a counterpart, the increased sensitivity and reproducibility of the dye-release assay provides a quantitative platform for evaluating and comparing environmental influences affecting the hydrolytic activity of protein antimicrobials. The ability to label specific heat-killed cell culture substrates with Remazol brilliant blue R dye expands this capability to tailor the dye-release assay to characterize enzymatic activity of interest.

Here, we present protocols to rapidly screen and characterize enzymes for antimicrobial activity. The microslide diffusion assay and the dye-release assay utilize target bacterial substrates for qualitative and quantitative enzymatic activity evaluation.

Initial evaluations of large microbial libraries for potential producers of novel antimicrobial proteins require both qualitative and quantitative methods ...

SILAC Based Proteomic Characterization of Exosomes from HIV-1 Infected Cells

Proteomics is the large-scale analysis of proteins. Proteomic techniques, such as liquid chromatography tandem mass spectroscopy (LC-MS/MS), can characterize thousands of proteins at a time. These powerful techniques allow us to have a systemic understanding of cellular changes, especially when cells are subjected to various stimuli, such as infections, stresses, and specific test conditions. Even with recent developments, analyzing the exosomal proteome is time-consuming and often involves complex methodologies. In addition, the resultant large dataset often needs robust and streamlined analysis in order for researchers to perform further downstream studies. Here, we describe a SILAC-based protocol for characterizing the exosomal proteome when cells are infected with HIV-1. The method is based on simple isotope labeling, isolation of exosomes from differentially labeled cells, and mass spectrometry analysis. This is followed by detailed data mining and bioinformatics analysis of the proteomic hits. The resultant datasets and candidates are easy to understand and often offer a wealth of information that is useful for downstream analysis. This protocol is applicable to other subcellular compartments and a wide range of test conditions.

Here, we describe a quantitative proteomics method using the technique of stable isotope labeling by amino acids in cell culture (SILAC) to analyze the effects of HIV-1 infection on host exosomal proteomes. This protocol can be easily adapted to cells under different stress or infection conditions.

Proteomics is the large-scale analysis of proteins. Proteomic techniques, such as liquid chromatography tandem mass spectroscopy (LC-MS/MS), can ...

Isolating Lymphocytes from the Mouse Small Intestinal Immune System

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to dietary antigens and commensal bacteria while mounting effective immune responses to enteropathogenic microbes. In addition, it has become clear that local intestinal immunity has a profound impact on distant and systemic immunity. Therefore, it is important to study how an intestinal immune response is induced and what the immunologic outcome of the response is. Here, a detailed protocol is described for the isolation of lymphocytes from small intestine inductive sites like the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes and effector sites like the lamina propria and the intestinal epithelium. This technique ensures isolation of a large numbers of lymphocytes from small intestinal tissues with optimal purity and viability and minimal cross compartmental contamination within acceptable time constraints. The technical capability to isolate lymphocytes and other immune cells from intestinal tissues enables the understanding of immune responses to gastrointestinal infections, cancers, and inflammatory diseases.

Here we describe a detailed protocol for the isolation of lymphocytes from the inductive sites including the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes, and the effector sites including the lamina propria and the intestinal epithelium of the small intestinal immune system.

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to ...

Co-staining Blood Vessels and Nerve Fibers in Adipose Tissue

Recent studies have highlighted the critical role of angiogenesis and sympathetic innervation in adipose tissue remodeling during the development of obesity. Therefore, developing an easy and efficient method to document the dynamic changes in adipose tissue is necessary. Here, we describe a modified immunofluorescent approach that efficiently co-stains blood vessels and nerve fibers in adipose tissues. Compared to traditional and recently developed methods, our approach is relatively easy to follow and more efficient in labeling the blood vessels and nerve fibers with higher densities and less background. Moreover, the higher resolution of the images further allows us to accurately measure the area of the vessels, amount of branching, and length of the fibers by open source software. As a demonstration using our method, we show that brown adipose tissue (BAT) contains higher amounts of blood vessels and nerve fibers compared to white adipose tissue (WAT). We further find that among the WATs, subcutaneous WAT (sWAT) has more blood vessels and nerve fibers compared to epididymal WAT (eWAT). Our method thus provides a useful tool for investigating adipose tissue remodeling.

New blood vessel formation and sympathetic innervation play pivotal roles in adipose tissue remodeling. However, there remain technical issues in visualizing and quantitatively measuring adipose tissue. Here we present a protocol to successfully label and quantitatively compare the densities of blood vessels and nerve fibers in different adipose tissues.

Recent studies have highlighted the critical role of angiogenesis and sympathetic innervation in adipose tissue remodeling during the development of ...

Isolating Brown Adipocytes from Murine Interscapular Brown Adipose Tissue for Gene and Protein Expression Analysis

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Chapters in this video

Real-time Imaging of Leukotriene B₄ Mediated Cell Migration and BLT1 Interactions with β-arrestin

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

Differentiating Functional Roles of Gene Expression from Immune and Non-immune Cells in Mouse Colitis by Bone Marrow Transplantation

Isolating And Immunostaining Lymphocytes and Dendritic Cells from Murine Peyer's Patches

Isolation of Adipose Tissue Immune Cells

Isolation of Murine Peritoneal Macrophages to Carry Out Gene Expression Analysis Upon Toll-like Receptors Stimulation

Qualitative and Quantitative Assays for Detection and Characterization of Protein Antimicrobials

SILAC Based Proteomic Characterization of Exosomes from HIV-1 Infected Cells

Isolating Lymphocytes from the Mouse Small Intestinal Immune System

Co-staining Blood Vessels and Nerve Fibers in Adipose Tissue