Detecting Glycogen in Peripheral Blood Mononuclear Cells with Periodic Acid Schiff Staining

Summary

Periodic acid Schiff staining is a technique that visualizes the polysaccharide content of tissues. This article demonstrates periodic acid Schiff staining protocol adapted for use on peripheral blood mononuclear cells purified from human venous blood. Such samples are enriched for lymphocytes and other white blood cells of the immune system.

Abstract

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. Polysaccharides such as glycogen, glycoproteins, and glycolipids stain bright magenta making it easy to enumerate positive and negative cells within the tissue. In muscle cells PAS staining is used to determine the glycogen content in different types of muscle cells, while in blood cell samples PAS staining has been explored as a diagnostic tool for a variety of conditions. Blood contains a proportion of white blood cells that belong to the immune system. The notion that cells of the immune system possess glycogen and use it as an energy source has not been widely explored. Here, we describe an adapted version of the PAS staining protocol that can be applied on peripheral blood mononuclear immune cells from human venous blood. Small cells with PAS-positive granules and larger cells with diffuse PAS staining were observed. Treatment of samples with amylase abrogates these patterns confirming the specificity of the stain. An alternate technique based on enzymatic digestion confirmed the presence and amount of glycogen in the samples. This protocol is useful for hematologists or immunologists studying polysaccharide content in blood-derived lymphocytes.

Introduction

Periodic acid Schiff (PAS) staining is an immunohistochemical technique that is widely used in muscle research and diagnostics. It is also utilized as a diagnostic tool on blood samples. The technique works by applying periodic acid solution to the sample, which oxidizes units within the polysaccharide creating aldehyde groups that react with the colourless Schiff's reagent thereby producing a deep magenta product. The steps of this procedure are shown in Figure 1. The stain turns anything with polysaccharides magenta, including glycogen, glycoproteins, glycolipids, mucins, or other molecules with polysaccharide moieties.

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Protocol

Research with human blood samples was approved by Concordia University Ethics Review Board, certificate number 10000618. The work on mouse muscle was approved by Concordia University Ethics Review Board, certificate number 2010BERG.

1. PBMC Isolation from Whole Blood

NOTE: Carry out this procedure in a biosafety cabinet using sterile technique and manufacturer-sterilized equipment.

1. Carefully pour 10-15 ml of whole blood from the heparinized (anti-coagulant) blood collection tubes into a 50 ml sterile conical tube. For minor blood spills, wipe with ddH₂O and 70% EtOH using cleaning tissue.

Results

To validate the reagents and basic technique, PAS staining was performed according to manufacturer’s instructions on mouse soleus muscle sections. The staining was done same day as the sacrifice and in the last step of the staining, the sections were fixed by xylene. The soleus muscle is known to contain ~35% glycogen-positive cells⁹. The stained muscle cells displayed two distinct PAS-positive features- punctate granules within the cell, and a continuous line demarking the cell membrane (Figure 2A

Discussion

The critical steps of this video article were during washing and amylase treatment of the cells. While washing the slides, the key step was using a plastic squeezable washing bottle and letting the water gently run through the sample on the slide and not aiming directly onto the samples. Even the slightest direct water pressure would cause the cells to come off the slide. Another key step was to use the same slide for ± amylase conditions. After the PBMCs were adhered to the slide, the slide was carefully placed int.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Periodic Acid Shiff Kit	Sigma-Aldrich	395B	Bring to room temperature prior to use. Materials in this kit are toxic and harmful. Use caution.
α-Amylase from porcine pancreas	Sigma-Aldrich	A3176
Binocular Microscope	Carl Zeiss Microscopy	Axio Lab A0
Glycogen Assay Kit	Sigma-Aldrich	MAK016
Ficoll-Paque PLUS	VWR, GE Healthcare	17-1440-02	Nonionic synthetic polymer of sucrose.
Centrifuge			For PBMC isolation, swing buckets were used.