Curr Pharm Design. 2014; 20:4906-4910

The Developing Role of Neuregulin1 in Cardiac Regenerative Stem Cell Therapy

 

Christopher P. Blomberg, Juyong Lee, James P. Morgan

Cardiovascular Medicine, Steward St. Elizabeth’s Medical Center, Boston, MA 02135. James.Morgan@steward.org.

 

Abstract

Myocardial infarction, heart failure, and chronic ischemic heart disease account for the majority of the cardiovascular burden. The current treatment strategies focus on limiting the progression of disease and preserving cardiac myocardium. The goal of stem cell therapy, on the other hand, is to reverse or replace damaged cardiac tissue. Over the past two decades many studies have been conducted to understand stem cell performance, survival, and the potential for cardiac repair. Neuregulin1, an epidermal growth factor family member, promotes embryonic stem cell differentiation into the cardiac lineage and improves survival in bone marrow-derived mesenchymal stem cell and embryonic endothelial progenitor cells. Current clinical trials are actively pursuing Neuregulin1’s therapeutic potential in the areas of heart failure and cardiac ischemia. Here, we review the current knowledge of Neuregulin1in stem cell biology and discuss the potential of using Neuregulin1 to improve stem cell therapy for cardiac repair.

PMID: 24283951

 

Supplement

Neuregulin1 (NRG1) proteins are members of the epidermal growth factor (EGF) family. Neuregulins had long been investigated for their roles in cancer biology (Heregulin), neurological pathophysiology (glial growth factor – GGF), and in skeletal muscle differentiation (acetylcholine receptor-inducing activity – ARIA). Only in the past two decades have we started to understand NRG1’s role in cardiac development and function. NRG1 proteins and their ErbB receptors (ErbB2, ErbB3 and ErbB4) are essential for cardiac development, in particular, ventricular trabeculae formation. In an adult heart, NRG1 proteins are produced by endothelial cells of the cardiac microvasculature. ErbB receptors are detected in both cardiomyocytes and endothelial cells. NRG1 proteins directly bind to ErbB3 and ErbB4, while recruiting ErbB2 as a co-receptor.

We studied the expression of NRG1α and NRG1β isoforms, as well as ErbB receptors during hanging-drop induced mouse embryonic stem cell (mESCs) cardiac differentiation. We found that NRG1α expression was gradually increased during the course of mESCs differentiation, while NRG1β expression was biphasic, with the first peak observed during day 5-7 and the second peak at day 14. This was associated with increased expression of Brachyury, a mesoderm maker. We then studied the effects of NRG1β treatment during different development windows. When NRG1β was added during day 5-7, it significantly increased expressions of transcriptional factors Nkx2.5, GATA4, MEF2c, structure proteins cardiac troponin T (cTnT), myosin light chain 2a (MLC2a), as well as connexin 40, a marker of cardiac conduction system. These results suggest that NRG1β promotes cardiac differentiation of mESCs at the stage of mesoderm formation. We then used ErbB2 and ErbB4 specific inhibitors to study the effects of inhibiting these two NRG1 receptors which are expressed on cardiomyocytes. We found that inhibiting ErbB2 or ErbB4 decreased the expressions of Nkx2.5 and cTnT, as well as the number of embryonic bodies (EBs) containing beating areas. These were associated with decreased activation of Akt and ERK1/2. These results have demonstrated that ErbB2 and ErbB4 receptors are necessary for mESCs cardiac differentiation [1].

In addition to signaling pathways, our studies show that NRG1β proteins may promote mESCs cardiac differentiation by regulating microRNA expression. By analyzing microRNAs that are regulated by NRG1 stimulation and/or ErbB2/4 inhibition, we identified new microRNAs that may be important for promoting or inhibiting ESCs cardiac differentiation. We found that miR-296-3p and miR-200c expressions were up-regulated by NRG1 treatment, but down-regulated by ErbB2/4 inhibitors, while miR-465b-5p expression was down-regulated by NRG1 and up-regulated by ErbB2/4 inhibitors. Further, miR-296-3p and miR-200c were up-regulated, while miR-465b-5p was down-regulated during mesoderm formation. The correlation of microRNA expression with the NRG1 signaling activation as well as mesodermal formation suggests that these microRNAs may mediate NRG1’s effects on ESCs cardiac differentiation [1].

Studies from Morisaki’s group showed that ErbB1, ErbB2 and ErbB4 receptor transcripts were gradually increased during EBs development. Recombinant NRG1β significantly increased Nkx2.5 expressing cells. Further, inhibition of ErbB receptors by small molecule tyrosine kinase inhibitors reduced EBs development into beating cardiomyocytes and ESCs-derived cardiomyocyte survival [2].

Studies from Dai’s group showed that NRG1 treatment increased the expression of transcriptional factors Nkx2.5 and GATA4, structure proteins α-MHC, β-MHC and Troponin T, as well as the number of EBs containing beating areas. ErbB inhibitor AG1478 inhibited NRG1- induced increased expression of Nkx2.5 [3].

Laflamme’s group found that activation of the recombinant NRG1 caused an increase in the working-type of hESC-derived cardiomyocytes, whereas the inhibition of this pathway with anti-NRG1 antibody or AG1478 drove hESC-derived cardiomyocytes into the nodal phenotype. Most recently, studies from Wang’s group also showed that inhibition ErbB receptors up-regulated HCN4 and Tbx3, markers of nodal cardiomyocytes in mESCs [4, 5].

Studies from Sawyer’s Jiang and Xie have shown that the NRG1 proteins improve survival in bone marrow-derived mesenchymal stem cells and embryonic endothelial progenitor cells [6-8].

 

Significance

Studies have suggested that NRG1 proteins may significantly improve the efficacy of cardiac stem therapy by promoting stem cell survival and differentiation into cardiomyocytes.

 

Acknowledgements

We thank Dr. Xinhua Yan for her primary role in preparation of this supplement.

JM fig1

References

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Contact

James P. Morgan, M.D., Ph.D.

Chief of Cardiology

Steward Carney Hospital

2100 Dorchester Avenue

Boston, MA 02124

Email: James.Morgan@steward.org

 

 

 

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