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

Summary

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.

Abstract

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.

Introduction

Adipose tissue is an essential organ for energy storage and is characterized by dynamic remodelling and nearly unlimited expansion¹. In addition to energy homeostasis, adipose tissue also plays an essential role in hormone secretion of over 50 adipokines to modulate whole-body metabolic function². Adipose tissue has a diverse architecture comprising of various cell types including mature adipocytes, fibroblasts, endothelial cells, immune cells, and adipocyte progenitor cells³. Recent studies have shown that obesity and other metabolic dysfunction can significantly alter adipose tissue function and....

Protocol

All experimental animal protocols were approved by the Animal Care Committee of The Center for Phenogenomics (TCP) conformed to the standards of the Canadian Council on Animal Care. Mice were maintained on 12-h light/dark cycles and provided with free access to water and food. 7 month old C57BL/6J male mice were used in the whole-mount staining experiment.

NOTE: Sections 1 to 2 are in chronological order, with section 3 being an optional step right after section 1. Section 4 can be performed t.......

Discussion

Although conventional techniques such as histology and cryosection offer benefits for observing intracellular structure, whole-mount staining provides a different perspective in adipose tissue research, which enables 3D visualization of cellular architecture of minimally processed tissue.

In order to successfully perform whole-mount staining, the following suggestions should be taken into consideration. Different adipose tissue depots can yield various immunostaining results; thus, the type of.......

Materials

Name	Company	Catalog Number	Comments
LipidTox	Life Technologies	H34477
PECAM-1 primary antibody	Millipore	MAB1398Z(CH)
TH (tyrosine hydroxylase) primary antibody	Millipore	AB152, AB1542
DAPI stain	BD Pharmingen	564907
Nikon A1R confocal microscope	Nikon		Confocal microscope
Ultramicroscope I	LaVision BioTec		Light sheet image fluorescent microscope
Alexa Fluor secondary antibodies	Jackson ImmunoResearch		Wavelengths 488, 594 and 647 used
Purified Rat Anti-Mouse CD16/CD32	BioSciences	553141
Dichloromethane	Sigma-Aldrich	270997
Dibenzyl-ether	Sigma-Aldrich	33630
Methanol	Fisher Chemical	A452-1
30% Hydrogen Peroxide	BIO BASIC CANADA INC	HC4060
Dimethyl sulfoxide (DMSO)	Sigma-Aldrich	D2650
Glycine	Sigma-Aldrich	J7126
Heparin	Sigma-Aldrich	H3393
Lectin kit I, fluorescein labeled	VECTOR LABORATORIES	FLK-2100
F4/80	Bio-Rad	MCA497GA
VECTASHIELD Hard Set Mounting Medium with DAPI	VECTOR LABORATORIES	H-1500
Paraformaldehyde (PFA)
Phosphate Buffer Saline (PBS)
Triton-X
Tween
Animal serum (goat, donkey)