Name: exploring adipose tissue structure by methylsalicylate clearing and 3d imaging
Uploaded: 2020-08-19T15:00:00
Description: Watch this Scientific Journal Video about Exploring Adipose Tissue Structure by Methylsalicylate Clearing and 3D Imaging at JoVE.com

This work was supported by INSERM, Universit&#233; C&#244;te d&#8217;Azur, and by grants from the French National Research Agency (ANR) through the Investments for the Future Labex SIGNALIFE (ANR-11-LABX-0028-01), the program UCA JEDI (ANR-15-IDEX-01) via Academy 2 &#8220;Syst&#232;mes Complexes&#8221; and Academy 4 &#8220;Complexit&#233; et diversit&#233; du vivant&#8221;, Fondation pour la Recherche M&#233;dical (&#201;quipe FRM DEQ20180839587), and the Young Investigator Program to J.G. (ANR18-CE14-0035-01-GILLERON). We also thank the Imaging Core Facility of C3M funded by the Conseil D&#233;partemental des Alpes-Maritimes and the R&#233;gion PACA, and which is also supported by the IBISA Microscopy and Imaging Platform C&#244;te d&#8217;Azur (MICA). We thank Marion Dussot for technical help in tissue preparation. We thank Abby Cuttriss, UCA International Scientific Visibility, for proof reading of the manuscript.

This protocol was tested and is validated for all mouse and human white adipose tissue depots. Human and mouse adipose tissues were collected accordingly to European laws and approved by French and Swedish Ethical committees.
1. Fixation of mouse and human white adipose tissue
<ol>
	<li>Immerse the harvested mouse or human white adipose tissues in at least 10 mL of PBS containing 4% paraformaldehyde (PFA) in a 15 mL plastic tube.</li>
	<li>Shake the plastic tube at room temperature on a roll...

<ol>
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The modifications that occur within the adipose tissue over the course of pathological progression, such as that of obesity, is fundamental to the understanding of the mechanisms behind the pathology. Pioneering studies that revealed such mechanisms in adipose tissue have been based on global approaches such as whole adipose tissue proteomics21, flow cytometry22,23, and transcriptomics24,<sup class="xref"...

Obesity is characterized by an increase in adipose tissue mass and has become a major worldwide public health issue, given that people with obesity have increased risk of developing cardiovascular disease, type-2 diabetes, liver diseases and some cancers.
A fundamental physiological function of adipose tissue is to modulate whole-body glucose and lipid homeostasis1,2. During the feeding period, the adipocytes (i.e., the main cells of the adipose tissue) store&#160;the excess of glucose and lipids provided by a meal into triglycerides. During fasting, the adipocytes break down the triglycerides into non-esterified fatty acids and glycerol to sustain the energy demand of the body. During the development of obesity, adipose tissue expand by increasing the size (hypertrophia) and/or the number (hyperplasia) of adipocytes1, to increase their storage capacity. When the expansion of adipose tissue reaches its limit, a constant highly variable among patients, the remaining lipids accumulates into other metabolic organs including muscles and liver3,4, leading to their functional failure and initiating obesity-related cardio-metabolic complications1,5. Therefore, identifying the mechanisms that govern adipose tissue expansion is a key clinical challenge.
The morphological modifications documented within adipose tissues during obesity are linked to its pathological dysfunction. Several staining procedures have been used to describe the tissue organization of the adipose tissue, including actin6, vascular markers7, lipid-droplet markers8, and specific immune cell markers9,10. However, because of the huge diameter of adipocytes (50 to 200 &#181;m)11, it is essential to analyze a large portion of the whole tissue in three dimensions in order to accurately analyze the dramatic structural AT changes observed during obesity. However, because the light does not penetrate an opaque tissue, imaging in 3D within a large tissue samples using fluorescence microscopy is not possible. Methods of tissue clearing to make them transparent have been reported in the literature (for a review, see12) allowing one to clear tissues and to perform in-depth, whole tissue fluorescence microscopy. These methods offer unprecedented opportunities to assess the 3D cellular organization in healthy and diseased tissue. Each of the described methods have advantages and drawbacks, and therefore need to be carefully selected depending on the studied tissue (for a review, see13). Indeed, some approaches require a long incubation period and/or the use of materials or compounds that are either expensive, toxic or difficult to obtain14,15,16,17,18,19. Taking advantage of one of the first compounds used a century ago by Werner Spalteholz to clear tissues20, we set up a user-friendly and inexpensive protocol that is very well adapted for the clearing of all mouse and human adipose tissue depots in any laboratory with typical equipment including a chemical hood, a temperature-controlled orbital shaker and a confocal microscope.

<table>
	<tbody>
		<tr>
			<td>1.5 mL microtubes</td>
			<td>Eppendorff tubes - Dutscher</td>
			<td>33528</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL plastic tubes</td>
			<td>Falcon tubes - Dutscher</td>
			<td>352096</td>
			<td></td>
		</tr>
		<tr>
			<td>18 mm round glass coverslip</td>
			<td>Mariendfeld</td>
			<td>0117580</td>
			<td></td>
		</tr>
		<tr>
			<td>20 mL glass bottle</td>
			<td>Wheaton</td>
			<td>986546</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-mouse-alexa647-conjugated antibody</td>
			<td>Jackson ImmunoResearch</td>
			<td>715-605-150</td>
			<td>Dilution: 1/100</td>
		</tr>
		<tr>
			<td>anti-rabbit-alexa647-conjugated antibody</td>
			<td>Jackson ImmunoResearch</td>
			<td>711-605-152</td>
			<td>Dilution: 1/100</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Sigma-aldrich</td>
			<td>A6003</td>
			<td></td>
		</tr>
		<tr>
			<td>CD301-PE antibody</td>
			<td>Biolegend</td>
			<td>BLE145703</td>
			<td>Dilution: 1/100</td>
		</tr>
		<tr>
			<td>CD31 antibody</td>
			<td>AbCam</td>
			<td>ab215912</td>
			<td>Dilution: 1/50</td>
		</tr>
		<tr>
			<td>Commercial 3D analysis software - IMARIS</td>
			<td>Oxford instrument</td>
			<td></td>
			<td>with Cell module</td>
		</tr>
		<tr>
			<td>Confocal microscope - Nikon A1R</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dapi</td>
			<td>ThermoFisher</td>
			<td>D1306</td>
			<td>Stock Concentration: 5 mg/mL; dilution 1/1000</td>
		</tr>
		<tr>
			<td>Deoxycholate</td>
			<td>Sigma-aldrich</td>
			<td>D6750</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma-aldrich</td>
			<td>D8418</td>
			<td></td>
		</tr>
		<tr>
			<td>Glut4 antibody</td>
			<td>Santa Cruz</td>
			<td>sc-53566</td>
			<td>Dilution: 1/50</td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma-aldrich</td>
			<td>G7126</td>
			<td></td>
		</tr>
		<tr>
			<td>Lectin-DyLight649</td>
			<td>Vector Lab</td>
			<td>DL-1178-1</td>
			<td>Stock Concentration : 2 &#181;g/&#181;L; IV Injection: 50 &#181;L/mice</td>
		</tr>
		<tr>
			<td>Metallic imaging chamber equipped with glass bottom - AttoFluor Chamber</td>
			<td>Thermofisher</td>
			<td>A7816</td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl salicylate</td>
			<td>Sigma-aldrich</td>
			<td>M6752</td>
			<td></td>
		</tr>
		<tr>
			<td>Perilipin antibody</td>
			<td>Progen</td>
			<td>651156</td>
			<td>Dilution: 1/50</td>
		</tr>
		<tr>
			<td>Phalloidin-alexa488</td>
			<td>ThermoFisher</td>
			<td>A12379</td>
			<td>Dilution: 1/100</td>
		</tr>
		<tr>
			<td>TCR-&#946;-PB antibody</td>
			<td>Biolegend</td>
			<td>BLE109225</td>
			<td>Dilution: 1/100</td>
		</tr>
		<tr>
			<td>TH antibody</td>
			<td>AbCam</td>
			<td>ab112</td>
			<td>Dilution: 1/50</td>
		</tr>
		<tr>
			<td>Triton X100</td>
			<td>Sigma-aldrich</td>
			<td>X100</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma-aldrich</td>
			<td>P416</td>
			<td></td>
		</tr>
	</tbody>
</table>

exploring adipose tissue structure by methylsalicylate clearing and 3d imaging

Obesity is a major worldwide public health issue that increases the risk to develop cardiovascular diseases, type-2 diabetes, and liver diseases. Obesity is characterized by an increase in adipose tissue (AT) mass due to adipocyte hyperplasia and/or hypertrophia, leading to profound remodeling of its three-dimensional structure. Indeed, the maximal capacity of AT to expand during obesity is pivotal to the development of obesity-associated pathologies. This AT expansion is an important homeostatic mechanism to enable adaptation to an excess of energy intake and to avoid deleterious lipid spillover to other metabolic organs, such as muscle and liver. Therefore, understanding the structural remodeling that leads to the failure of AT expansion is a fundamental question with high clinical applicability. In this article, we describe a simple and fast clearing method that is routinely used in our laboratory to explore the morphology of mouse and human white adipose tissue by fluorescent imaging. This optimized AT clearing method is easily performed in any standard laboratory equipped with a chemical hood, a temperature-controlled orbital shaker and a fluorescent microscope. Moreover, the chemical compounds used are readily available. Importantly, this method allows one to resolve the 3D AT structure by staining various markers to specifically visualize the adipocytes, the neuronal and vascular networks, and the innate and adaptive immune cells distribution.

Using the procedure described here and summarized in Figure 1, we were able to stain and optically clear human and mouse white adipose tissue as presented in Figure 2A and Figure 2B, respectively. The cleared tissue was transferred to the metallic imaging chamber to perform confocal imaging (Figure 3A). The clearing drastically improved the depth of the tissue images that we were able to acquire (<stron...

Watch this Scientific Journal Video about Exploring Adipose Tissue Structure by Methylsalicylate Clearing and 3D Imaging at JoVE.com

Exploring Adipose Tissue Structure by Methylsalicylate Clearing and 3D Imaging

Here, we describe a simple, inexpensive and fast clearing method to resolve the 3D structure of both mouse and human white adipose tissue using a combination of markers to visualize vasculature, nuclei, immune cells, neurons, and lipid-droplet coat proteins by fluorescent imaging.

Obesity is a major worldwide public health issue that increases the risk to develop cardiovascular diseases, type-2 diabetes, and liver diseases. Obesity ...

These protocol allows analysis of three-dimensional structure of Very large human on mouse adipose tissue ballet microscopy. Facilitating the linkage of pathological dysfunction with adipose tissue structural changes. This clearing process are very simple, very well adapted to clearing human on warm mice adipose tissue and use less toxic solvent such as ethanol or methyl salicylate compared to other clear protocols.Begin by immersing the harvested mouse or human white adipose tissue in at least 10 milliliters of 4%power formaldehyde in PBS in a 15 milliliter plastic tube preferentially under a chemical hood. Shake the tissue on a rolling plate at room temperature for one hour before transferring the tube to a rolling plate at four degrees Celsius overnight. The next morning rinse the fixed white adipose tissue in 10 milliliters of PBS for five minutes at room temperature to remove all traces of fixative and transfer the tissue to a 15 milliliter tube containing 10 milliliters of 0.3%glycine in PBS for a one hour incubation at room temperature on an orbital shaker at 100 revolutions per minute.When the remaining free aldehyde groups have been quenched, immerse the tissue in a 15 milliliter tube containing 10 milliliters of 0.2%Triton X-100 in PBS for a two hour incubation with shaking at 37 degrees Celsius. At the end of the incubation treat the tissue with 10 milliliters of 0.2%Triton X-100 and 20%DMSO with shaking at 37 degrees Celsius overnight. The next morning immerse the tissue in a 15 milliliter plastic tube containing 10 milliliters of 0.1%Tween 20, 0.1%Triton X-100, 0.1%deoxycholate and 20%DMSO in PBS for an at least 24 hour incubation at 37 degrees Celsius with shaking.At the end of the incubation, rinse the tissue with 10 milliliters of 0.2%Triton X-100 in PBS on an orbital shaker at 100 revolutions per minute for one hour. Followed by immersion in 15 milliliters of 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS for 12 hours at 37 degrees Celsius with shaking. For staining of the white adipose tissue.Transfer the tissue into 300 microliters of 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS, supplemented with the primary antibodies of interest in a 1.5 milliliter micro tube protect it from light with aluminum foil and place the tube into a 50 milliliter Falcon tube. Place the tube into the orbital shaker for a two day incubation at 37 degrees Celsius with shaking. At the end of the incubation rinse the tissue two times in 10 milliliters of 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS for five hours at 37 degrees Celsius with shaking and protection from light.After the second rinse wash the tissue in 10 milliliters of fresh 0.2%Triton X-100, 10%DMSO and 3%BSA and PBS for 16 to 48 hours at 37 degrees Celsius with shaking, then transfer the tissue to a 1.5 milliliter tube containing 300 microliters of 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS, supplemented with the appropriate secondary antibodies and protect the tube from light using aluminum foil. After a two day incubation at 37 degrees Celsius on a shaker, wash the tissue two times in 10 milliliters of 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS for five hours at 37 degrees Celsius with shaking protected from light. After the second wash, rinse the tissue into a tube containing 10 milliliters of fresh 0.2%Triton X-100, 10%DMSO and 3%BSA in PBS for 16 to 48 hours at 37 degrees Celsius with shaking and light protection.Followed by a two hour wash in 10 milliliters of PBS alone at 37 degrees Celsius with shaking and light protection. For white adipose tissue clearing at the end of the PBS wash immerse the tissue and 10 milliliters of an ascending sending ethanol concentration series for a two hour incubation per concentration at room temperature with shaking protected from light as indicated. The next morning immerse the tissue in a 20 milliliter glass bottle with a plastic cap containing five milliliters of methyl salicylate in a fume hood.The white adipose tissue is still clearly visible at this stage. Shake the container protect it from light at room temperature for at least two hours. The white adipose tissue becomes completely transplant.For 3D confocal imaging of the stained and cleared white adipose tissue mount a metallic imaging chamber equipped with a glass bottom and in a fume hood transfer the tissue to the chamber. Fill the chamber with fresh methyl salicylate. Finalize the mountaging of the chamber by adding a small cover slip to stabilize the tissue and a large cover slip to close the chamber.Place the chamber onto an inverted confocal microscope stage for tissue imaging at low magnification to generate a few cubic centimeter 3D maps of the whole adipose tissue sample. After 3D map generation, use a 20X long distance air objective that provides a good ratio between the resolution and depth to select several areas for tissue sampling at a higher magnification. For cell segmentation convert 3D stacks onto the software format to free up memory space.Before opening the cell module of the software. Change the cell detection setting to plasma membrane staining and select the fluorescent channel of the marker used to delineate the cell periphery. Then set up the thresholds, provide a range of the expected cell sizes and run the segmentation.The affects of clearing on human and mouse white adipose tissue can be observed with the naked eye. Clearing also drastically improves the image depth of the tissue that is able to be acquired. And facilitates whole tissue 3D imaging and 3D map generation out of 4X Magnification.3D mapping further enables the selection of different areas of interest to be acquired at a 20X magnification to a depth of two millimeters. Specific staining of lipid droplets and adipocytes can be achieved using perilipin and anti-GLUT4 antibodies respectively. Blood vessels can be detected using either CD31 antibody or intravenous injection of Lectin DyLight 649 shortly before sacrifice.Macrophages and T-cells can be visualized using anti CD301 phycoerythrin antibody and anti TCR beta Pacific blue antibody. The peripheral nerve network can be detected using anti Tyrosine Hydroxylase antibody. Using these labelings the mean size and size distribution of the adipocytes and the blood vessel network density within the adipose tissue can then be determined.It's crucial to follow occupation time as demonstrated because poor sample preparation will not result in a good image quality. This protocol can be combined with advanced imaging system or can be coupled to post-processing image analysis freeware.

exploring-adipose-tissue-structure-methylsalicylate-clearing-3d

Research

JoVE Journal

Biology

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

ACT-PRESTO: Biological Tissue Clearing and Immunolabeling Methods for Volume Imaging

The identification and exploration of the detailed organization of organs or of the whole body at the cellular level are fundamental challenges in biology. Transitional methods require a substantial amount of time and effort to obtain a 3D image and including sectioning the intact tissue, immunolabeling, and imaging serially-sectioned tissue, which produces a loss of information at each step of the process. In recently developed approaches for high-resolution imaging within intact tissue, molecular characterization has been restricted to the labeling of proteins. However, currently available protocols for organ clearing require a considerably long process time, making it difficult to implement tissue clearing techniques in the lab. We recently established a rapid and highly-reproducible protocol termed ACT-PRESTO (active clarity technique&#8211;pressure related efficient and stable transfer of macromolecules into organs), which allows for tissue clearance within several hours. Moreover, ACT-PRESTO enables rapid immunolabeling with conventional methods and accelerates antibody penetration into the deep layer of densely-formed, thick specimens by applying pressure or convection flow. We describe how to prepare tissues, how to clear by lipid removal using electrophoresis, and how to immuno-stain by a pressure-assisted delivery. The rapidity and consistency of the protocol will expedite the performance of 3D histological research and volume-based diagnoses.

ACT-PRESTO (active clarity technique&#8211;pressure related efficient and stable transfer of macromolecules into organs) enables rapid, efficient, but inexpensive tissue clearing and rapid antibody penetration into cleared tissues by passive diffusion or pressure-assisted delivery. Using this method, a wide range of tissues can be cleared, immunolabeled by multiple antibodies, and volume-imaged.

The identification and exploration of the detailed organization of organs or of the whole body at the cellular level are fundamental challenges in ...

Sample Preparation and Imaging of Exosomes by Transmission Electron Microscopy

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The contents and morphology of the secreted vesicles reflect cell behavior or physiological status, for example cell growth, migration, cleavage, and death. The exosomes&#39; role may depend highly on size, and the size of exosomes varies from 30 to 300 nm. The most widely used method for exosome imaging is negative staining, while other results are based on Cryo-Transmission Electron Microscopy, Scanning Electron Microscopy, and Atomic Force Microscopy. The typical exosome&#39;s morphology assessed through negative staining is a cup-shape, but further details are not yet clear. An exosome well-characterized through structural study is necessary particular in medical and pharmaceutical fields. Therefore, function-dependent morphology should be verified by electron microscopy techniques such as labeling a specific protein in the detailed structure of exosome. To observe detailed structure, ultrathin sectioned images and negative stained images of exosomes were compared. In this protocol, we suggest transmission electron microscopy for the imaging of exosomes including negative staining, whole mount immuno-staining, block preparation, thin section, and immuno-gold labelling.

This protocol describes the various techniques necessary for transmission electron microscopy including negative staining, ultrathin sectioning for detailed structure, and immuno-gold labelling to determine the positions of specific proteins in exosomes.

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The ...

Adipo-Clear: A Tissue Clearing Method for Three-Dimensional Imaging of Adipose Tissue

Adipose tissue plays a central role in energy homeostasis and thermoregulation. It is composed of different types of adipocytes, as well as adipocyte precursors, immune cells, fibroblasts, blood vessels, and nerve projections. Although the molecular control of cell type specification and how these cells interact have been increasingly delineated, a more comprehensive understanding of these adipose-resident cells can be achieved by visualizing their distribution and architecture throughout the whole tissue. Existing immunohistochemistry and immunofluorescence approaches to analyze adipose histology rely on thin paraffin-embedded sections. However, thin sections capture only a small portion of tissue; as a result, the conclusions can be biased by what portion of tissue is analyzed. We have therefore developed an adipose tissue clearing technique, Adipo-Clear, to permit comprehensive three-dimensional visualization of molecular and cellular patterns in whole adipose tissues. Adipo-Clear was adapted from iDISCO/iDISCO+, with specific modifications made to completely remove the lipid stored in the tissue while preserving native tissue morphology. In combination with light-sheet fluorescence microscopy, we demonstrate here the use of the Adipo-Clear method to obtain high-resolution volumetric images&#160;of an entire adipose tissue.

Due to the high lipid content, adipose tissue has been challenging to visualize using traditional histological methods. Adipo-Clear is a tissue clearing technique that allows robust labeling and high-resolution volumetric fluorescent imaging of adipose tissue. Here, we describe the methods for sample preparation, pretreatment, staining, clearing, and mounting for imaging.

Adipose tissue plays a central role in energy homeostasis and thermoregulation. It is composed of different types of adipocytes, as well as adipocyte ...

Visualization of 3D White Adipose Tissue Structure Using Whole-mount Staining

Adipose tissue is an important metabolic organ with high plasticity and is responsive to environmental stimuli and nutrient status. As such, various techniques have been developed to study the morphology and biology of adipose tissue. However, conventional visualization methods are limited to studying the tissue in 2D sections, failing to capture the 3D architecture of the whole organ. Here we present whole-mount staining, an immunohistochemistry method that preserves intact adipose tissue morphology with minimal processing steps. Hence, the structures of adipocytes and other cellular components are maintained without distortion, achieving the most representative 3D visualization of the tissue. In addition, whole-mount staining can be combined with lineage tracing methods to determine cell fate decisions. However, this technique has some limitations to providing accurate information regarding deeper parts of adipose tissue. To overcome this limitation, whole-mount staining can be further combined with tissue clearing techniques to remove the opaqueness of tissue and allow for complete visualization of entire adipose tissue anatomy using light-sheet fluorescent microscopy. Therefore, a higher resolution and more accurate representation of adipose tissue structures can be captured with the combination of these techniques.

The focus of the present study is to demonstrate the whole-mount immunostaining and visualization technique as an ideal method for 3D imaging of adipose tissue architecture and cellular component.

Adipose tissue is an important metabolic organ with high plasticity and is responsive to environmental stimuli and nutrient status. As such, various ...

Optical Clearing of Plant Tissues for Fluorescence Imaging

It is challenging to directly observe the internal structure of multi-layered and opaque plant specimens, without dissection, under a microscope. In addition, autofluorescence attributed to chlorophyll hampers the observation of fluorescent proteins in plants. For a long time, various clearing reagents have been used to make plants transparent. However, conventional clearing reagents diminish fluorescent signals; therefore, it has not been possible to observe the cellular and intracellular structures with fluorescent proteins. Reagents were developed that can clear plant tissues by removing chlorophyll while maintaining fluorescent protein stability. A detailed protocol is provided here for the optical clearing of plant tissues using clearing reagents, ClearSee (CS) or ClearSeeAlpha (CSA). The preparation of cleared plant tissues involves three steps: fixation, washing, and clearing. Fixation is a crucial step in maintaining the cellular structures and intracellular stability of fluorescent proteins. The incubation time for clearing depends on the tissue type and species. In Arabidopsis thaliana, the time required for clearing with CS was 4 days for leaves and roots, 7 days for seedlings, and 1 month for pistils. CS also required a relatively short time of 4 days to make the gametophytic leaves of Physcomitrium patens transparent. In contrast, pistils in tobacco and torenia produced brown pigment due to oxidation during CS treatment. CSA reduced the brown pigment by preventing oxidation and could make tobacco and torenia pistils transparent, although it took a relatively long time (1 or 2 months). CS and CSA were also compatible with staining using chemical dyes, such as DAPI (4',6-diamidino-2-phenylindole) and Hoechst 33342 for DNA and Calcofluor White, SR2200, and Direct Red 23 for the cell wall. This method can be useful for whole-plant imaging to reveal intact morphology, developmental processes, plant-microbe interactions, and nematode infections.

Here, a method is described for making plant tissues transparent while maintaining the stability of fluorescent proteins. This technique facilitates deep imaging of cleared plant tissues without physical sectioning.

It is challenging to directly observe the internal structure of multi-layered and opaque plant specimens, without dissection, under a microscope. In ...

Differentiation and Imaging of Brown Adipocytes from the Stromal Vascular Fraction of Interscapular Adipose Tissue from Newborn Mice

Brown adipose tissue (BAT) is only present in mammals and has a thermogenic function. Brown adipocytes are characterized by a multilocular cytoplasm with multiple lipid droplets, a central nucleus, a high mitochondrial content, and the expression of uncoupling protein 1 (UCP1). BAT has been proposed as a potential therapeutic target for obesity and its associated metabolic disorders due to its ability to dissipate metabolic energy as heat. To investigate BAT function and regulation, brown adipocyte culturing is indispensable. The present protocol optimizes tissue processing and cell differentiation for culturing brown adipocytes from newborn mice. Additionally, procedures for the imaging of differentiated adipocytes with both confocal immunofluorescence and transmission electron microscopy are shown. In the brown adipocytes differentiated with the techniques described herein, the major defining features of classical BAT are preserved, including high UCP1 levels, increased mitochondrial mass, and very close physical contact between the lipid droplets and mitochondria, making this method a valuable tool for BAT studies.

Preadipocytes are isolated from the stromal vascular fraction of interscapular brown adipose tissue from newborn mice and differentiated into cells that accumulate lipid droplets, express molecular markers, and show the mitochondrial morphology of mature brown adipocytes. These cells are further analyzed by immunofluorescence and transmission electron microscopy.

Brown adipose tissue (BAT) is only present in mammals and has a thermogenic function. Brown adipocytes are characterized by a multilocular cytoplasm with ...

Murine Adipose Tissue Excision

Shave the abdominal and inguinal regions of two sedated adult male Sprague Dawley rats. Disinfect the shaved regions with an iodine solution. Make a medial longitudinal incision from the sternum to the testicular region, Using a pair of sterile forceps, remove the adipose tissue from the epididymidis and the kidneys.Place the tissue in conical tubes containing 20 milliliters of cold, sterile PBS-AA solution.

Quantification of Intramuscular Adipose Tissue (IMAT) Lipid Droplet Metrics Using Confocal Imaging

To begin the quantification of stained IMAT lipid droplet metrics, open Confocal Stacks in ImageJ. Open the Threshold User Interface by selecting Image, then Adjust, then Threshold. In the user interface, select Intermodes as the thresholding type and ensure Dark Background is selected.Then click on Apply to run a thresholding algorithm. Run the watershed algorithm to separate touching lipid droplets by selecting Process, then Binary, and Watershed. Select Yes in a dialog box to process all the images in the stack to add a thin black line dividing larger areas of solid white.To set the maximum and minimum particle sizes, open the original image and outline the smallest and largest lipid droplet in view using the Oval tool. Then add these shapes to the ROI Manager by typing T.Select Analyze, then Set Measurements. In the dialog box, select the settings, check Area only, and click OK.Then select Measure from the ROI Manager.Use the two area measures from this results window as the size range and analyze particles. To identify the region of interest, or ROIs, with the analyze particles algorithm. Select Analyze, then Analyze Particles.A dialog box opens to set the selection settings. To output the ROI Measurements, select Analyze, then Set Measurements, and select Area, Centroid, Fit Ellipse, and Stack Position. Click on OK.Then select Measure from the ROI Manager.The data in the results table can be selected and copied into Excel for further analysis. For a detailed assessment of individual lipid droplet metrics and distribution, the BODIPY fluorescently labeled lipid droplets were imaged via confocal microscopy. Thresholding and shape segmentation provided a good first pass for generating ROIs for each lipid droplet.However, manual edits were needed to correct the errors. Deep lipid droplets, which appeared dim on the image, can be added by hand using the Oval tool in ImageJ. A group of lipid droplets mistakenly identified as a single ROI can also be corrected by deleting and replacing the original ROI with multiple new ROIs.Where a single lipid droplet was identified as a unique ROI in multiple slices, the duplicate ROIs were consolidated into a single ROI.

Dissection and Isolation of Murine Perivascular Adipose Tissue (PVAT)

Begin by spraying the properly euthanized mouse with 75%alcohol to disinfect the skin. Then place the mouse in a supine position. Lift the skin of the animal's abdominal region, and using surgical scissors, make a small incision in it.Then using the scissors, bluntly separate the skin and abdominal muscles from the pelvis to the neck, along the ventral midline. Expose the heart and lungs by cutting the diaphragm and ribs along both sides of the midline. Next, carefully remove the liver, spleen, bowels, and kidney, avoiding damage to the intestinal wall.Following that, remove the lungs and esophagus. Now gently lift the heart using forceps held in one hand and separate the aorta from the spine with surgical scissors held in the other hand. Then place the heart and aorta in a 60 millimeter petri dish, containing antibiotic supplemented PBS.Retrieve the microsurgical forceps and microsurgical scissors from the alcohol, and rinse them in 25 milliliters of PBS to remove excess alcohol. Working under a stereo microscope, remove the thymus and other tissues from the heart and aorta. Then remove the heart, leaving the aorta with the perivascular adipose tissues or PVATs.Transfer the aorta along with the PVATs to a clean 60 millimeter petri dish containing antibiotic supplemented PBS. Using one pair of microsurgical forceps, hold the aorta, and using another pair, pull off the attached adipose tissues to separate the PVATs from the aorta. Remove as much vascular tissue as possible while causing minimal harm to the PVATs.Finally, transfer the collected PVATs into a two milliliter microcentrifuge tube, containing antibiotic supplemented, high glucose, DMEM, placed on ice.