OP0240 A MULTIMODAL MASS SPECTROMETRY APPROACH REVEALS SPECIFIC CARTILAGE MOLECULAR PROFILES ASSOCIATED TO TYPE 2 DIABETIC PATIENTS
Authors: M. Eveque, P. Emans, B. Claes, F. Bouwman, R. M. A. Heeren, B. Cillero-Pastor
Journal: Annals of the Rheumatic Diseases (2020)

Background: Osteoarthritis (OA) is mainly characterized by the progressive deterioration of articular cartilage. Recent studies support that type 2 diabetes (TD2) is a risk factor to develop OA [1, 2]. However, the molecular cartilage profile of patients combining these two diseases remains unclear, and a better understanding of the different OA phenotypes should be considered for the development of personalized medicine. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is used to investigate the bimolecular distribution of proteins, lipids or metabolites through the in-situ analysis of tissue sections. Bottom-up proteomics focuses on the relative quantification of proteins. The combination of both technologies could be considered to reveal specific molecular profiles and help for patient classification. Objectives: The main goal of this study is to apply a multimodal mass spectrometry approach on cartilage to reveal specific lipidomic and proteomic profiles associated to TD2 patients. Methods: Human cartilages from OA (n a =10) and OA/TD2 human patients (n b =10) were obtained from donors undergoing total knee joint replacement. Cartilage punches of 8*8mm were sectioned at 12 µm thickness for MALDI-MSI and bottom-up proteomics. For MALDI-MSI experiments (n a =6; n b =6), norharmane matrix was sprayed over the samples for the detection of lipids. Experiments were then performed in positive ion polarity at 50 µm of lateral resolution using a RapifleX MALDI Tissue-typer instrument. LipostarMSI and in-house ChemomeTricks toolbox for MATLAB software were used for data processing and analysis. For bottom-up proteomics experiment (n a =10; n b =10), proteins were extracted, separated using SDS-PAGE and digested prior to liquid chromatography separation coupled to an orbitrap MS Q-Exactive HF mass spectrometer. Proteome Discoverer, enrichR and Reactome software were used for data processing and analysis. Results: MALDI-MSI showed overall differences between OA and OA/TD2 patients based on their specific lipidomic profiles. In particular, sphingomyelin and phosphatidylcholine species were significantly more abundant in OA patients whereas lysolipids such as lysophosphatidylcholine species were mainly present in OA/TD2 patients, providing therefore phenotype-specific OA molecular panels. Additionally, we observed that phosphatidylcholine and sphingomyelin species were more present in the superficial layer of the cartilage whereas lysophosphatidylcholine species were more abundant in the deep layer (Fig. 1A, B). Proteomics experiments applied on cartilage enables the quantification of 114 proteins. Among those, 73 were overexpressed in OA samples whereas 41 were overexpressed in OA/TD2 patients. Among the differentially regulated proteins (Fig. 1C), phospholipase A2 was increased in the diabetic cohort, in line with the elevated level of lysolipids found in the imaging data. Our results also involved the fatty acid omega oxidation and the fatty acid biosynthesis pathways as relevant to explain this deregulation of the lipid metabolism. Conclusion: MALDI–MSI combined with proteomics experiments showed different profiles between OA and OA/TD2 patients and could be employed for patient classification. References: [1]Louati, K., et al., Association between diabetes mellitus and osteoarthritis: systematic literature review and meta-analysis. RMD Open, 2015. 1 (1): p. e000077. [2]Williams, M.F., et al., Type 2 diabetes and osteoarthritis: a systematic review and meta-analysis. J Diabetes Complications, 2016. 30 (5): p. 944-50. Acknowledgments: The Dutch Province of Limburg and MUMC institutional grant. Disclosure of Interests: Maxime Eveque: None declared, Pieter Emans Shareholder of: Shareholder and cofounder start-up company Chondropeptix, Grant/research support from: Institution received grants from STW, ReumaNederland, InSciTE, Consultant of: Consultancy to Kiomed, Speakers bureau: Payment for lectures by Kiomed, Episurf, Britt Claes: None declared, Freek Bouwman: None declared, Ron M A Heeren: None declared, Berta Cillero-Pastor: None declared