Recent studies have disclosed that several genes are up-regulated in bone marrow (BM) mononuclear cells from rheumatoid arthritis (RA) patients. However, it remains unclear whether such abnormalities result from systemic inflammation or from abnormalities at stem cell level. The current study therefore examined the expression of several representative genes, including amphiregulin (AREG), chemokine receptor 4 (CXCR4), and FK506-binding protein 5 (FKBP5) in RA BM CD34+ cells.
BM samples were obtained from 52 patients with RA and 35 patients with osteroarthritis (OA) during joint operations. CD34+ cells were purified from the BM mononuclear cells by positive selection with magnetic beads. The mRNA expression for AREG, CXCR4, and FKBP5 was measured using quantitative real-time PCR.
The expression of mRNA for FKBP5, but not that of AREG or CXCR4, was significantly higher in RA BM CD34+ cells than in OA BM CD34+ cells. The FKBP5 mRNA expression level was not correlated with serum CRP or treatment. In addition, tumour necrosis factor-alpha did not enhance the expression of FKBP5 mRNA in BM CD34+ cells from healthy donors.
The results suggest that the enhanced expression of FKBP5 in BM CD34+ cells might be an intrinsic abnormality of RA BM CD34+ cells, whereas the enhanced expression of AREG and CXCR4 in BM mononuclear cells might be secondary to systemic inflammation.