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Left ventricular unloading alters receptor tyrosine kinase expression in the failing human heart
Iván P Uray1, John H Connelly, Vilmos Thomázy
1Department of Integrative Biology and Pharmacology, University of Texas at Houston Medical School, Houston, Texas 77225, USA.
Background:
Experimental and clinical data suggest that the loss of membrane receptor tyrosine kinase (RTK) activity in cardiac myocytes results in increased frequency of apoptotic cell death and progression of heart failure. The goal of our study was to examine the expression characteristics of RTKs in ventricular myocardium obtained from patients before and after mechanical unloading.
Methods:
We extracted RNA from paired formalin-fixed, paraffin-embedded left ventricular tissue blocks obtained at the time of left ventricular assist device (LVAD) implantation and explantation from a cohort of 36 patients (median age 51 years). The duration of LVAD support ranged from 1 to 314 days (median 95 days), 17 patients had ischemic and 19 non-ischemic cardiomyopathy at the time of LVAD implantation. Using real-time reverse transcription-polymerase chain reaction (RT-PCR) we quantitated transcripts for atrial natriuretic factor (ANF) and tumor necrosis factor-alpha (TNF-alpha), markers of heart failure, and the RTKs Her2/neu, Her4 and gp130, regulators of cardiac cell survival.
Results:
In patients undergoing mechanical unloading, ANF and TNF-alpha mRNA levels were independently suppressed. Her2/neu, along with Her4 was upregulated, mostly in cases of ischemic cardiomyopathy, whereas gp130 levels decreased. Post-LVAD transcript levels of Her2 correlated tightly with gp130 in patients with non-pathologic entry values of gp130. Duration of treatment and age were also determining factors in the change of expression of these genes.
Conclusion:
Real-time quantitative (Q)-RT-PCR can be used to quantitate gene expression in archival myocardial tissue blocks. Mechanical unloading leads to a re-adjustment of RTK transcript levels, but not their reverting to control values in heart failure patients.
Insights
Mechanical unloading in heart failure patients alters receptor tyrosine kinase (RTK) expression. While some RTKs are upregulated, they do not return to normal levels, indicating a partial re-adjustment in cardiac myocytes.
Area of Science:
- Cardiovascular Biology
- Molecular Cardiology
- Regenerative Medicine
Background:
- Receptor tyrosine kinase (RTK) loss in cardiac myocytes is linked to heart failure progression.
- Mechanical unloading aims to improve cardiac function by reducing workload.
Purpose of the Study:
- To investigate the expression patterns of RTKs in ventricular myocardium before and after mechanical unloading.
- To assess changes in gene expression markers of heart failure.
Main Methods:
- RNA extraction from archival myocardial tissue of 36 heart failure patients.
- Quantitative real-time reverse transcription-polymerase chain reaction (Q-RT-PCR) for gene expression analysis.
- Analysis of heart failure markers (ANF, TNF-alpha) and RTKs (Her2/neu, Her4, gp130).
Main Results:
- Mechanical unloading suppressed ANF and TNF-alpha mRNA levels.
- Her2/neu and Her4 were upregulated, particularly in ischemic cardiomyopathy.
- gp130 levels decreased, with correlations observed between Her2 and gp130 post-unloading.
Conclusions:
- Q-RT-PCR is effective for gene expression analysis in archival myocardial tissue.
- Mechanical unloading partially re-adjusts RTK transcript levels in heart failure patients.
- RTK expression does not fully revert to control levels after mechanical unloading.