MicroRNA expression in adult and aged lung. Semi-quantitative RT-PCR from adult and aged lung tissue revealed a number of miRNAs that were highly expressed irrespective of age. Higher expression is equivalent to a smaller ΔCT value (CT value of miRNA – CT value of 18 s). Statistical significance was measured using Student's t-test (p < 0.05) and data is represented as the mean ΔCT +/- S.E.M. (CT value of gene – CT value of 18 s) of 5 animals.