An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

Summary

The ex vivo assay described in this study using gut homogenate extracts and immunofluorescence staining represents a novel method to examine the hyphal morphogenesis of Candida albicans in the GI tract. This method can be utilized to investigate the environmental signals regulating morphogenetic transition in the gut.

Abstract

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important role in the dissemination and pathogenesis of this opportunistic fungal pathogen. However, methods to visualize fungal hyphae in the GI tract in vivo are challenging which limits the understanding of environmental signals in controlling this morphogenesis process. The protocol described here demonstrates a novel ex vivo method for visualization of hyphal morphogenesis in gut homogenate extracts. Using an ex vivo assay, this study demonstrates that cecal contents from antibiotic treated mice, but not from untreated control mice, promote C. albicans hyphal morphogenesis in the gut content. Further, adding back specific groups of gut metabolites to the cecal contents from antibiotic-treated mice differentially regulates hyphal morphogenesis ex vivo. Taken together, this protocol represents a novel method to identify and investigate the environmental signals that control C. albicans hyphal morphogenesis in the GI tract.

Introduction

Candida albicans is an opportunistic, polymorphic fungal pathogen that is normally commensal, but can undergo a morphological change into a virulent form capable of causing life-threatening infections in immunocompromised individuals^{1,2,3,4,5,6,7,8,9,10,11,12}

Protocol

All animal protocols were approved by Midwestern University Institutional Animal Care and Use Committee (IACUC) as described before⁵⁷. The Institutional Animal Care and Use Committee at Midwestern University approved this study under MWU IACUC Protocol #2894. The MWU animal care policies follow the Public Health Service (PHS) Policy on Humane Care and Use of Laboratory Animals and the policies laid out in the Animal Welfare Act (AWA).

1. Mice study standard protocol

1. Use male and female C57BL/6J mice at least six weeks old. Supplement them with sterile water with or without cefoperazone (0.5 mg/mL).
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Results

These results along with previous findings from the Thangamani laboratory⁶⁰ indicate that when C. albicans is grown ex vivo in gut homogenate extracts taken from the stomach, small intestines and large intestines of untreated control and antibiotic-treated mice, C. albicans generally develops with a yeast morphology (Figure 1B). However, when grown in the cecal extract from antibiotic-treated mice, C. albicans readily undergoes morphogenesis.......

Discussion

The method described here presents a novel way to investigate the effect of antibiotic, dietary, xenobiotic and therapeutic impacts on C. albicans hyphal morphogenesis in the GI tract. Since the majority of systemic infections originate from the GI tract^{21,22,23,24,25,26,27,}

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1 - 10 µL Pipet Tips	Fisher Scientific	02-707-454	Misc
100 - 1000 µL Pipet Tips	Fisher Scientific	02-707-400	Misc
20 - 200 µL Pipet Tips	Fisher Scientific	02-707-451	Misc
2-methylbutyric acid	Sigma	193070-25G	hyphal-inhibitory compound
488 goat anti-rabbit IgG	Invitrogen (Fisher)	A11008	IF Staining secondary ab
Agar	Fisher	BP1423-500	YPD agar component
Automated Imaging Microscope	Keyence	BZX700
Candida Albicans Antibody	Invitrogen (Fisher)	PA1-27158	IF Staining primary ab
cefoperazone	Cayman	16113	antibiotic
deoxycholic acid	Sigma	30960	hyphal-inhibitory compound
D-Glucose	Fisher	D16-500	hyphal-promoting compound
forceps	Fisher	08-885
lactic acid	Alfa Aesar	AAAL13242-06	hyphal-inhibitory compound
lithocholic acid	Sigma	L6250-10G	hyphal-inhibitory compound
palmitic acid	Sigma	P5585-10G	hyphal-inhibitory compound
Paraformaldehyde	Alfa Aesar	A11313	IF Staining fixative
Phosphate-buffered saline (PBS), 10x	Alfa Aesar	J62692	PBS component
p-tolylacetic acid	SCBT	sc-257959	hyphal-inhibitory compound
sebacic acid	Sigma	283258-250G	hyphal-inhibitory compound
sharp ended scissors	Fisher	28301
sterile Milli-Q water	N/A	N/A	Misc
YPD Broth	BD Biosciences	242810	YPD agar component