For tissue samples, the total RNA for each sample was extracted by BGI according to their manufacturing procedure. Whereas, the total RNA for each discharge sample was extracted by TRIzol reagent before sending to BGI for further processing of the samples according to their manufacturing procedure. The small RNAs were filtered by separation on PAGE gel. Followed by 3' adaptor ligation, reverse primer annealing, and 5' adaptor ligation. Then the cDNA was synthesized and amplified. The library fragments were selected by separation of the amplified products of 100-120 bp by PAGE gel. The final step involved library quantitation and pooling cyclization.