Distinct mitral valve proteomic profiles in rheumatic heart disease and myxomatous degeneration

Abstract

Rheumatic heart disease (RHD) affects heart-valve tissue and is the most serious consequence of group A Streptococcus infection. Myxomatous degeneration (MXD) is the most frequent valvopathy in the western world. In the present work, key protein expression alterations in the heart-valve tissue of RHD and MXD patients were identified and characterized, with controls from cadaveric organ donors. Proteins were separated by two-dimensional (2D)-electrophoresis and identified by mass spectrometry. We found 17 differentially expressed protein spots, as compared to control samples. We observed an increased expression of ASAP-2 in the RHD patients' valves, while collagen-VI, haptoglobin-related protein, prolargin, and cartilage oligomeric protein showed reduced expression. Valve tissue of MXD patients, on the other hand, presented lower expression of annexin-A1 and A2, septin-2, SOD (Cu/Zn), and transgelin. Tissue samples from both valvopathies displayed higher expression of apolipoprotein-A1. Biglycan was downexpressed in both diseases. Vimentin and lumican showed higher expression in RHD and lower in MXD. These results suggest that key pathogenetic mechanisms are intrinsically distinct in RHD and MXD.

Keywords: 2DE-DIGE; IPA; heart-valve proteins; myxomatous degeneration; rheumatic heart disease.

Figure 1

Preparative gel and differentially expressed spots. 2D-DIGE analysis of homogenates from a representative gel. The arrows represent the identification of the differentially expressed spots, according to UNIPROT accession codes for human proteins. Differences were considered to be statistically significant for P < 0.05 between groups.

Figure 2

Differential protein profile. Hierarchical clustering of 27 spots with differential expression between the gels was grouped according to protein expression profile. Each line represents a protein spot, and each column, a sample. Distance measure: Pearson, with complete linkage between neighbor spots and samples. Valve tissue from patients: RHD (n = 6) and MXD (n = 4); CTL (n = 4). The symbol # denotes the sample identifications.

Figure 3

In silico analysis of the proteins differentially expressed in the valvopathies. IPA^® was used to build a network of direct (solid lines) and indirect (dashed lines) interactions between proteins with differential expressions compared to the control group. Symbols in red denote proteins with increased expression and green decreased expression. The molecules in blank were added by the software and are predicted to be altered in each figure. (A) Network of protein–protein interactions for RHD: score of 13 and (B) the same network for MXD: score of 14.