Objective To explore the difference of transfer RNA-derived small RNA (tsRNA) expression profile before and after acute myocardial infarction (AMI) and the diagnostic value of tsRNA for AMI.

Methods Age- and weight-matched male C57 mice (8-10 weeks) were randomly divided into MI group and Sham group, with 4 in each group. AMI model was surgically induced in mice in MI group. After 24 h of modeling, RNA was extracted from left ventricular myocardial tissue. After removing modifications, total RNA of each sample was sequentially ligated to 3' and 5' small RNA adapters. Subsequently, reverse transcription PCR was performed. cDNA was then synthesized and amplified. The amplified products corresponding to the size of 15-40 nt RNA were screened to construct a library for sequencing. The sequencing results were compared with the mature tRNA and tRNA precursor sequences in GtRNAdb database. Differentially expressed tsRNA profiles before and after AMI were obtained. The alterations of the cleaved patterns of tRNA corresponding to the same codon before and after AMI were analyzed. According to the profile of differentially expressed tsRNA before and after AMI, tsRNA only abundantly expressed in MI group were selected and verified in myocardial tissue and plasma of mice to explore the potential of these tsRNAs as diagnostic markers of AMI.

Results tsRNA profile showed good repeatability within the same group and great distinctiveness between the different groups. After AMI occurred, the cleaved patterns of a variety of tRNAs changed, including tRNA Asn-GTT, Glu-TTC, Gly-ACC, Gly-GCC, His-GTG, Ile-AAT, Ile-GAT, Pro-TGG, Ser-AGA, and Trp-CCA. Compared with the Sham group, 268 tsRNAs significantly up-regulated and 1 228 tsRNAs down-regulated in MI group, and 64 tsRNAs were uniquely expressed in MI group. tRF-Gly-CCC-2-31, tiRNA-Val-CAC-1-32, tiRNA-Val-AAC-2-32, tiRNA-Glu-TTC-2-32, and tiRNA-Lys-TTT-1-34 were specifically expressed in cardiac tissue on the 1^st day post AMI. Among them, tiRNA-Val-AAC-2-32 and tiRNA-Lys-TTT-1-34 showed specifically abundant levels in plasma from MI group and dynamically changed with AMI duration.

Conclusions The expression profile of tsRNA is significantly different before and after AMI. tiRNA-Val-AAC-2-32 and tiRNA-Lys-TTT-1-34 are uniquely highly expressed in myocardial tissue and plasma from AMI mice, and might have the potential as diagnostic markers of AMI.