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MicroRNAs have already been considered as biomarkers in different cardiovascular diseases. In order to evaluate whether circulating microRNAs may serve as markers in the diagnosis of TTC, plasma samples from patients of the International Takotsubo Registry (www.takotsubo-registry.com) were collected within 24 h after the onset of symptoms and compared to those of patients with ST-segment elevation acute myocardial infarction (STEMI) and healthy persons. For the screening of differentially regulated miRNAs, five RNA samples of each group were pooled and miRNA expression was measured by TaqMan Human MicroRNA Card A and B array, version 2.0 (Applied Biosystems).
According to the results of miRNA profiling, eight miRNAs were selected for verification by real-time quantitative reverse transcription polymerase chain reaction in patients with TTC (n= 36), ST-segment elevation acute myocardial infarction (STEMI, n = 27), and healthy controls (n = 28). In patients with TTC an up-regulation was confirmed of miR-16 and miR-26a compared with healthy subjects (both, P< 0.001), and up-regulation of miR-16, miR-26a, and let-7f compared with STEMI patients (P< 0.0001, P<0.05, and P< 0.05, respectively). Consistent with previous publications, cardiac specific miR-1 and miR-133a were up-regulated in STEMI patients compared with healthy controls (both, P< 0.0001). Moreover, miR- 133a was substantially increased in patients with STEMI compared with TTC (P<0.05). A unique signature comprising miR-1, miR-16, miR-26a, and miR-133a differentiated TTC from healthy subjects [area under the curve (AUC) 0.835, 95% CI 0.733–0.937, P< 0.0001] and from STEMI patients (AUC 0.881, 95% CI 0.793–0.968, P<0.0001). This signature yielded a sensitivity of 74.19% and a specificity of 78.57% for TTC vs. healthy subjects, and a sensitivity of 96.77% and a specificity of 70.37% for TTC vs. STEMI patients. Also, a decrease of the endothelin-1 (ET-1)-regulating miRNA-125a-5p in parallel with a robust increase of ET-1 plasma levels in TTC compared with healthy subjects (P<0.05) was measured.
Comments In the present study Jaguszewski et al. demonstrated that the same miRNAs might be upregulated in the plasma in different cardiac diseases, however at a different quantity. Whereas miR-1, miR-133a is highly upregulated in STEMI patients these molecules are only weakly expressed in TTC patients. In contrast miR-16 and miR-26a was significantly upregulated in TTC patients but not in STEMI patients or healthy controls. Taken together these four miRNAs describe a signature which is unique for TTC patients. Also, it is interesting to note that the upregulation of the stress-and depression related miR-16 and miR-26 is in line with the high incidence of psychosocial or mental triggers often preceding the TTC event in these patients. On the other hand a decrease of the ET-1 regulating miRNA-125a-5p was measured in patients with TTC implicating this miRNA as regulator of vasomotor homeostasis. Notably, a significant increase of ET-1 in the plasma was found TTC patients which might reflect the potential role of ET-1 as a mediator of microvascular spasm. These investigations represent an important step forward to the early diagnosis of TTC. However limitations are given by the fact that it is unclear whether the signature changes if the plasma samples are collected later than 24h after the onset of symptoms. It would also be interesting to evaluate the signature of miRNA expression directly in the heart tissue samples of TTC patients to exclude any influence which is not due to the disease-related changes in the heart.
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