Abstract
BackgroundRheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial joints. Early intervention followed by early diagnosis can result in disease remission; however, both early stage diagnosis and provision of effective treatment have been impeded by the heterogeneity of RA, which details of pathological mechanism are unclear. Regardless of numerous investigations of RA by means of genomic and proteomic approaches, proteins interplaying in RA synovial tissues that contain various types of synoviocytes, are not yet sufficiently understood. Hence we have conducted an HPLC/mass spectrometry-based exploratory proteomic analysis focusing on synoviocyte lesions laser-microdissected (LMD) from formalin-fixed paraffin-embedded (FFPE) synovial tissues (RA, n = 15; OA, n = 5), where those of Osteoarthritis (OA) were used as the control.ResultsA total of 508 proteins were identified from the RA and OA groups. With the semi-quantitative comparisons, the spectral index (SpI), log2 protein ratio (RSC) based on spectral counting, and statistical G-test, 98 proteins were found to be significant (pair-wise p < 0.05) to the RA synovial tissues. These include stromelysin-1 (MMP3), proteins S100-A8 and S100-A9, plastin-2, galectin-3, calreticulin, cathepsin Z, HLA-A, HLA-DRB1, ferritin, neutrophil defensin 1, CD14, MMP9 etc.ConclusionsOur results confirmed the involvement of known RA biomarkers such as stromelysin-1 (MMP3) and proteins S100-A8 and S100-A9, and also that of leukocyte antigens such as HLA-DRB1. Network analyses of protein–protein interaction for those proteins significant to RA revealed a dominant participation of ribosome pathway (p = 5.91 × 10−45), and, interestingly, the associations of the p53 signaling (p = 2.34 × 10−5). An involvement of proteins including CD14, S100-A8/S100-A9 seems to suggest an activation of the NF-kB/MAPK signaling pathway. Our strategy of laser-microdissected FFPE-tissue proteomic analysis in Rheumatoid Arthritis thus demonstrated its technical feasibility in profiling proteins expressed in synovial tissues, which may play important roles in the RA pathogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12014-015-9091-8) contains supplementary material, which is available to authorized users.
Highlights
Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial joints
Differential protein expression analysis has been performed by using the spectral index (SpI), [36] the fold change of a expressed protein in the base 2 logarithmic scale (RSC) [37] which are based on spectral counting
We have employed in this study an exploratory proteomic analysis of laser-microdissected formalin-fixed paraffin-embedded (FFPE)-tissues to elucidate protein expression profiles at synoviocyte lesions obtained from RA and OA patients, in which the OA samples served as the control
Summary
Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial joints. A series of reports has compared “fingerprint” profiles using a proteomic approach, which has found some RAspecific proteins including S100A9/A8, serum amyloid A, galectin, and ubiquitin–proteasome pathway components [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] Most of these studies were conducted with peripheral blood, synovial fluid (SF), or cultured synovial cells from patients with RA, when most synoviocytes responsible for the inflammatory joint disorders in RA are found in the whole RA synovial tissue. Selective collection of target cells from formalin fixed paraffin embedded (FFPE) tissues by laser microdissection (LMD) will allow access to tissues of a variety of cell types with a definite diagnosis. [31,32,33,34] we have applied this approach in order to attain a proteomic profile of RA from laser-microdissected FFPE synoviocyte lesions, which will help better understand the molecular mechanisms involved in RA
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