Apolipoprotein D as a novel marker in human end-stage heart failure: a preliminary study

Apolipoprotein D (Apo D) is reported to be in close association with developing and mature blood vessels, and involved in enhanced smooth muscle cell migration after injury. This study was designed to clarify the expression pattern of Apo D and the possibility of Apo D as a new marker in human end-stage heart failure. Individual RNA samples obtained from independent left ventricular tissue of six heart failure patients derived from cardiomyopathies of different aetiologies during cardiac transplantation and six non-failing control subjects were hybridized to the gene microarray containing, in total, 35 000 well-characterized Homo sapiens genes. Apo D was one of the highly expressed genes (3.3-fold upregulated) detected by microarray, which was further confirmed by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) (5.88-fold upregulated) in failing hearts compared with non-failing hearts. Both Western blotting and immunohistochemistry analyses also demonstrated the higher levels of Apo D protein in failing hearts. Importantly, we observed elevated levels of plasma Apo D in heart failure patients compared with non-failing control subjects. We demonstrated, for the first time to our knowledge, that Apo D was highly expressed in the mRNA and protein levels in human failing hearts compared with non-failing hearts. Furthermore, our finding of elevated plasma Apo D levels in patients with heart failure provides clues that Apo D may act not only as a cardiac molecular marker but also as a circulating biomarker in patients with heart failure.