Age-related decrease of miRNA-92a levels in human CD8⁺ T-cells correlates with a reduction of naïve T lymphocytes

MicroRNA (miR)-17-92a expression plays a crucial role in lymphocyte ontogeny. We therefore set out to determine miR-92a expression levels in peripheral blood lymphocytes from healthy subjects to ascertain any association between these levels and ageing. We found a positive correlation between the miR-92a expression level and the percentages of RO-CD8⁺CD27⁺ (P = 0.0046) and CD3⁺CD8⁺CD62L⁺ (P = 0.0011). This suggests that the majority of miR-92a of CD8⁺ T cells is derived from naïve cells, and the miR-92a expression level in CD8⁺ T cells declines progressively with age. These results indicate that the age-related attrition of naïve T cells is linked to a reduction of miR-92a in human T -lymphocytes. Therefore, we should careful attention when evaluating human miRNA levels in T lymphocytes to use normal control values.