OBJECTIVEEarlier studies have confirmed that mesenchymal stem cells (MSCs) can transdifferentiate into myocytes and improve heart function in 2 weeks. But the mechanism is not clear. In this study, the mechanism of improvement of heart function after transplantation of MSCs was examined with suppression subtractive hybridization (SSH).

METHODSMSCs were isolated from thighone and tibia of Wistar rats, purified by adhesion-screening method, and expanded in vitro. Intraperitoneal injection of doxorubicin (at 2.5 mg/kg/time and total doses of 15 mg/kg) established cardiomyopathy models. MSCs were transplanted into cardiomyocytes. The differential genes between tester (rats with cardiomyopathy that were injected with MSCs) and driver (rats with cardiomyopathy that were injected with equivalent volume of culture medium) were screened with suppression subtractive hybridization.

RESULTSAfter 4 weeks of intraperitoneal injection of doxorubicin, left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) decreased by 26.48% and 40.61%, respectively (P < 0.01), as compared with those of normal group. Cardiomyopathy model was established successfully. And the heart function of the rats with cardiomyopathy was significantly improved after transplantation. Sixteen gene fragments were detected, and 12 of them were up-regulated in testers. They were rattus norvegicus mitochondrial BN/SsNHsdMCW, rattus norvegicus strain mitochondrial F344 X BN F1, rattus norvegicus mitochondrion H(+)-ATP synthase alphase subunit (Atp5al) mRNA, rattus norvegicus BHE/Cdb tRNA-Lys gene, rat mitochondrial H(+)-ATP synthase alpha subunit mRNA, rattus norvegic (wild-caught animal) complete mitochondrial genome, rattus norvegic clone BB.1.4.1 unknown Glu-Pro dipeptide repeat protein mRNA, Arabidopsis thaliana transgenic line C DNA, rat mitochondrial ATP synthase beta subunit mRNA, rattus norvegic mitochondrial genome, rat cardiac troponin T mRNA and rat mRNA for beta-globin. Four gene fragments were down-regulated in testers. They were rat mRNA for sarcomeric mitochondrial creatine kinase, rat mRNA for ribosomal phosphoprotein P2, rat alpha-crystallin B chain mRNA and rattus norvegicus NADH-ubiquinone oxidoreductase Fe-S protein 7 mRNA.

CONCLUSIONThe expression of the genes relating to mitochondrial synthesizing and contracting proteins synthesizing increased after MSC transplantation. The genes might enhance energy synthesis and promote MSC transdifferentiate into myocytes, and then improve heart function of rats with cardiomyopathy.