Although serum microRNAs (miRNAs) play essential roles in the diagnosis of various diseases, little is known about circulating miRNAs in the aging process. Solexa sequencing technology was used for an initial miRNA screening of serum samples pooled from 21 healthy Chinese subjects with an average age of 22 years, 10 subjects with an average age of 40 years, 10 subjects with an average age of 59 years, and 9 subjects with an average age of 70 years. Other serum samples were obtained from 123 normal people with approximately 31 samples in each age period. A stem-loop quantitative reverse transcription-PCR assay was conducted to confirm the concentrations of the miRNAs altered in the aging process. 
Solexa sequencing demonstrated 10 markedly altered miRNAs in the aging process. Quantitative reverse transcription-PCR analysis identified five downregulated miRNAs (miR-29b, miR-106b, miR-130b, miR-142-5p, and miR-340) and three upregulated miRNAs (miR-92a, miR-222, and miR-375) with age. Their target genes, related diseases, molecular and cellular functions, and participated pathways were further analyzed
. The measurement of miRNAs in serum provides a novel, noninvasive approach for the identification of the aging process. Our bioinformatic analyses could form a useful knowledge base for the potential future development of novel therapeutic treatments.