miR-223 is overexpressed in T-lymphocytes of patients affected by rheumatoid arthritis.

miRNAs have recently emerged as key regulators of the immune system, being involved in lymphocyte selection and proliferation, in T(reg) cells differentiation, and in hematopoiesis in general. Rheumatoid arthritis (RA) is an autoimmune pathology the etiology of which is still obscure. Although a multifactorial pathogenesis has been hypothesized, the precise mechanisms leading to the disease are still poorly understood at the molecular level. miRNA expression profile analysis highlighted that miR-223 is the only miRNA that is strikingly deregulated in peripheral T-lymphocytes from RA patients compared with healthy donors. Further analysis by quantitative reverse transcription-polymerase chain analysis confirmed that miR-223 is overexpressed in T-lymphocytes from RA patients (n = 28) compared with healthy donors (n = 10). Moreover, purification of different T-lymphocyte populations from RA patients highlights that miR-223 is expressed at higher levels in naive CD4(+) lymphocytes, whereas its expression is barely detectable in T(h)-17 cells. In summary, our data provide a first characterization of the miRNA expression profiles of peripheral T-lymphocytes of RA patients, identifying miR-223 as overexpressed in CD4(+) naive T-lymphocytes from these individuals. A deeper analysis of the biologic functions and effects of the expression of miR-223 in T-lymphocytes is needed to clarify the exact link between our observation and the disease.