Open Access Research article

Glycophenotyping of osteoarthritic cartilage and chondrocytes by RT-qPCR, mass spectrometry, histochemistry with plant/human lectins and lectin localization with a glycoprotein

Stefan Toegel1*, Daniela Bieder1, Sabine André2, Friedrich Altmann3, Sonja M Walzer1, Herbert Kaltner2, Jochen G Hofstaetter14, Reinhard Windhager1 and Hans-Joachim Gabius2

Author affiliations

1 Karl Chiari Lab for Orthopaedic Biology, Department of Orthopaedics, Medical University of Vienna, Waehringer 18-20 1090 Vienna, Austria

2 Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University Munich, Munich, Germany

3 Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria

4 2nd Department, Orthopaedic Hospital Vienna-Speising, Vienna, Austria

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Citation and License

Arthritis Research & Therapy 2013, 15:R147  doi:10.1186/ar4330

Published: 4 October 2013

Abstract

Introduction

This study aimed to characterize the glycophenotype of osteoarthritic cartilage and human chondrocytes.

Methods

Articular knee cartilage was obtained from nine osteoarthritis (OA) patients. mRNA levels for 27 glycosyltransferases were analyzed in OA chondrocytes using RT-qPCR. Additionally, N- and O-glycans were quantified using mass-spectrometry. Histologically, two cartilage areas with Mankin scores (MS) either ≤4 or ≥9 were selected from each patient representing areas of mild and severe OA, respectively. Tissue sections were stained with (1) a selected panel of plant lectins for probing into the OA glycophenotype, (2) the human lectins galectins-1 and -3, and (3) the glycoprotein asialofetuin (ASF) for visualizing β-galactoside-specific endogenous lectins.

Results

We found that OA chondrocytes expressed oligomannosidic structures as well as non-, mono- and disialylated complex-type N-glycans, and core 2 O-glycans. Reflecting B4GALNT3 mRNA presence in OA chondrocytes, LacdiNAc-terminated structures were detected. Staining profiles for plant and human lectins were dependent on the grade of cartilage degeneration, and ASF-positive cells were observed in significantly higher rates in areas of severe degeneration.

Conclusions

In summary, distinct aspects of the glycome in OA cartilage are altered with progressing degeneration. In particular, the alterations measured by galectin-3 and the pan-galectin sensor ASF encourage detailed studies of galectin functionality in OA.