P3507Heterozygous cardiomyocyte-specific deletion of ErbB4 sensitizes to development of pregnancy-related cardiomyopathy

Background

Peripartum cardiomyopathy (PPCM) is a potentially life-threatening disease in women without known cardiovascular disease; PPCM is characterized by left ventricular (LV) systolic dysfunction towards the end of pregnancy and/or in the first months postpartum. The underlying mechanisms of PPCM are incompletely understood, but there is recent evidence that impaired cardiomyocyte expression of the tyrosine kinase ErbB4 receptor plays a role. ErbB4 is the main receptor of neuregulin-1, a protective and regenerative paracrine factor in the heart. Homozygous deletion of ErbB4 is lethal.

Purpose

To test the hypothesis that mice with heterozygous (HZ) cardiomyocyte-specific deletion of ErbB4 (ErbB4+/−) are more susceptible to PPCM.

Methods

Cardiac morphology and function was evaluated by echocardiography with a Vevo 2100 Imaging System during 2 pregnancies and 6 weeks postpartum (n=7–9) or during non-pregnant control conditions in HZ (ErbB4+/−) and wild type controls (n=9–10). Then, hearts were excised for analyses of myocardial fibrosis, macrophage infiltration, capillary density and cardiomyocyte cross sectional area.

Results

When compared to pregnant wild type controls, pregnant ErbB4+/− mice developed significant LV dilatation (2 weeks after the 2nd delivery: LVIDd +16% ± 2%, p<0.05) and dysfunction (6 weeks after the 2nd delivery: EF −23% ± 3%, p<0.001), increased heart to body weight ratio (+7% ± 4%, p<0.05) and increased cardiomyocyte cross sectional area (+28% ± 7%, p<0.01). Non-pregnant ErbB4+/− mice also developed LV dilatation and dysfunction, albeit slower than pregnant ErbB4+/− mice. On histology, however, myocardial tissue of pregnant ErbB4+/− mice did not show macrophage infiltration, neither fibrosis, nor reduced capillary density.

Conclusions

Heterozygous cardiomyocyte-specific deletion of ErbB4 sensitizes to peripartum LV dilatation and cardiomyocyte hypertrophy and systolic dysfunction without profound cardiac injury, features that are frequently present in PPCM patients and may explain their high chance for recovery. These data reinforce a compensatory role for neuregulin-ErbB4 signaling during hemodynamic overload, and confirm that this signaling pathway is important to protect the maternal heart during peripartum stress.

Acknowledgement/Funding

Fund scientific research Flanders; University Antwerp

P316The cardiac endothelial cell transcriptome in neonatal, adult, and remodeling hearts

Background

Cardiac microvascular endothelial cells (CMVECs) are the most numerous cells in the myocardium and orchestrate cardiogenesis during development, regulate adult cardiac function, and modulate pathophysiology of heart failure. It has been shown that the transcriptome of CMVECs differs from other endothelial cell types, but transcriptomic changes in cardiac endothelial cells during cardiac maturation and cardiac remodeling have not been studied earlier.

Purpose

To study changes in the transcriptome of CMVECs during cardiac maturation and cardiac remodeling, and to test the hypothesis that the fetal gene program is reactivated during cardiac remodeling in CVMECs.

Methods

CMVECs were isolated from rat hearts based on CD31 expression and were immediately processed for RNA sequencing, without an in vitro propagation step. We compared gene expression levels from primary CMVECs of neonatal hearts, normal adult hearts, and infarcted-hearts (4 weeks post LAD ligation).

Results

Between neonatal and adult CMVECs, 6838 genes were differentially expressed indicating that CMVECs undergo a substantial transformation during postnatal cardiac growth. A large fraction of genes upregulated in neonatal CMVECs are part of mitosis pathways, whereas a large fraction of genes upregulated in adult CMVECs are part of cellular response, secretory, signaling, and cell adhesion pathways. Between CMVECs of normal adult hearts and infarcted hearts, 159 genes were differentially expressed. We found a limited degree of overlap (55 genes) between the differentially expressed genes in neonatal and infarcted-hearts. Of 46 significantly upregulated genes in the infarcted heart, 46% were also upregulated in neonatal hearts relative to sham. Of 113 significantly downregulated genes in the infarcted-hearts, 30% were also downregulated in neonatal hearts relative to sham.

Conclusion

These data demonstrate that CMVECs undergo dramatic changes from neonatal to adult and more subtle changes between normal state and cardiac remodeling. During cardiac remodeling, a small part of the fetal gene program is reactivated in CMVECs.

Acknowledgement/Funding

IOF/SBO research grant (PID34923), Fund for Scientific Research Flanders (Application numbers 1501118N and 1842219N).