MALDI MS imaging as a powerful tool for investigating synovial tissue

Abstract

Objective To identify and image protein biomarker candidates in the synovial tissue of patients with rheumatoid arthritis (RA) and patients with osteoarthritis (OA). Methods A novel matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) technique was applied to the analysis of synovial tissue. Patients were classified according to the American College of Rheumatology (ACR) criteria for RA. Frozen sections were stained to obtain morphological data. Serial sections were desiccated, and spotted with matrix for MALDI analysis. Ions generated by laser irradiation of the tissue were separated in time, based on their m/z ratio, and were subsequently detected. IMS was used in a ‘profiling’ mode to detect discrete spots for rapid evaluation of proteomic patterns in various tissue compartments. Photomicrographs of the stained tissue images were reviewed by a pathologist. Areas of interest (10 discrete areas/compartment) were marked digitally and the histology-annotated images were merged to form a photomicrograph of the section taken before the MALDI measurement. Pixel coordinates of these areas were transferred to a robotic spotter, the matrix was spotted, and the coordinates of the spots were transferred to a mass spectrometer for spectral acquisition. The data generated were then subjected to biocomputation analysis to reveal the biomarker candidates. Results Several peaks (m/z) consistent in mass with calgranulins, defensins, and thymosins were detected and their distribution in various synovial compartments (synovial lining and sublining layer) was demonstrated. Conclusion MALDI IMS is a powerful tool for the rapid detection of numerous proteins (in situ proteomics) and was applied here for the analysis of the distribution of proteins in synovial tissue sections.

Reliable Entity Subtyping in Non-small Cell Lung Cancer by Matrix-assisted Laser Desorption/Ionization Imaging Mass Spectrometry on Formalin-fixed Paraffin-embedded Tissue Specimens

“…Promising results using this technology could be obtained in several diseases and different types of cancer (9,(22)(23)(24).…”

“…A total of 1600 spectra in 200-shots increment were summed for each laser spot position using the Random Walk raster pattern as described previously (supplemental Fig. S1) (9,14). A peptide calibration standard mix including angiotensin II, angiotensin I, substance P, bombesin, ACTH clip 1-17, ACTH clip 18 -39, and somatostatin 28 (Bruker Daltonik) was used for external calibration.…”

Application of metabolomics in autoimmune diseases: Insight into biomarkers and pathology

“…This technique is becoming increasingly useful for metabolomics application. In ADs, IMS has been successfully applied to synovial tissue of patients with RA and OA (Kriegsmann et al, 2012). Furthermore, comprehensive "omics-based" strategies by combining genomic, epigenomic, transcriptomic levels and downstream changes at the proteomic and ultimately metabolomics levels would provide complete system biology approaches.…”

Osteoarthritis year 2012 in review: biomarkers

“…A new technique known as MALDI imaging mass spectrometry (IMS) has been developed for correlating protein expression to specific anatomical areas of joint tissues 52 . This technology has been applied to the analysis of synovial tissues from OA and RA patients.…”

“…Proteins identifications are then linked back to the anatomical locations. MALDI IMS is a powerful tool for the rapid in situ detection of proteins in cartilage and synovial tissue sections 52 . Further refinements in this technology and the addition of quantitative capability will make this one of the most powerful technologies in future studies of OA biomarkers.…”