Figure 2

Amphiregulin expression in peripheral blood and synovial fluid samples. (A) The concentrations of AREG in plasma and synovial fluid samples are plotted as log-values on the y-axis of box-plots. Significant differences are shown by asterisks (**P < 0.01). RA: samples from RA patients; OA: samples from OA patients; HC: samples from healthy volunteers. (B) The AREG mRNA expression levels in PBMCs and AREG protein concentrations in plasma are shown. Venous blood samples from 6 RA patients and 6 healthy volunteers (HC) were separated into plasma and PBMCs. Total RNAs were extracted from PBMCs and subjected to cDNA synthesis. The AREG mRNA levels were measured by real-time PCR and normalized by the GAPDH mRNA levels. The relative AREG mRNA level relative to the GAPDH mRNA level is plotted as the log ratio on the primary y-axis (left), while the plasma concentration of AREG protein measured by ELISA is plotted as the log value on the secondary y-axis (right). The correlation coefficient (ρ) of the protein level in plasma to the mRNA level in PBMCs is -0.378 (P = 0.2104). (C) PBMCs from 4 RA patients and 2 HCs were separated by CD14 microbeads, and the AREG mRNA level in each fraction was measured by real-time PCR. The log ratio of the AREG mRNA level relative to the GAPDH mRNA level is plotted on the y-axis.