Cardiac fibroblasts regulate sympathetic nerve sprouting and neurocardiac synapse stability

PLoS One. 2013 Nov 14;8(11):e79068. doi: 10.1371/journal.pone.0079068. eCollection 2013.

Abstract

Sympathetic nervous system (SNS) plays a key role in cardiac homeostasis and its deregulations always associate with bad clinical outcomes. To date, little is known about molecular mechanisms regulating cardiac sympathetic innervation. The aim of the study was to determine the role of fibroblasts in heart sympathetic innervation. RT-qPCR and western-blots analysis performed in cardiomyocytes and fibroblasts isolated from healthy adult rat hearts revealed that Pro-Nerve growth factor (NGF) and pro-differentiating mature NGF were the most abundant neurotrophins expressed in cardiac fibroblasts while barely detectable in cardiomyocytes. When cultured with cardiac fibroblasts or fibroblast-conditioned medium, PC12 cells differentiated into/sympathetic-like neurons expressing axonal marker Tau-1 at neurites in contact with cardiomyocytes. This was prevented by anti-NGF blocking antibodies suggesting a paracrine action of NGF secreted by fibroblasts. When co-cultured with cardiomyocytes to mimic neurocardiac synapse, differentiated PC12 cells exhibited enhanced norepinephrine secretion as quantified by HPLC compared to PC12 cultured alone while co-culture with fibroblasts had no effect. However, when supplemented to PC12-cardiomyocytes co-culture, fibroblasts allowed long-term survival of the neurocardiac synapse. Activated fibroblasts (myofibroblasts) isolated from myocardial infarction rat hearts exhibited significantly higher mature NGF expression than normal fibroblasts and also promoted PC12 cells differentiation. Within the ischemic area lacking cardiomyocytes and neurocardiac synapses, tyrosine hydroxylase immunoreactivity was increased and associated with local anarchical and immature sympathetic hyperinnervation but tissue norepinephrine content was similar to that of normal cardiac tissue, suggesting depressed sympathetic function. Collectively, these findings demonstrate for the first time that fibroblasts are essential for the setting of cardiac sympathetic innervation and neurocardiac synapse stability. They also suggest that neurocardiac synapse functionality relies on a triptych with tight interaction between sympathetic nerve endings, cardiomyocytes and fibroblasts. Deregulations of this triptych may be involved in pathophysiology of cardiac diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / metabolism*
  • Coculture Techniques
  • Fibroblasts / cytology
  • Fibroblasts / metabolism*
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Nerve Growth Factor / metabolism*
  • PC12 Cells
  • Rats
  • Rats, Inbred Lew
  • Sympathetic Nervous System / cytology
  • Sympathetic Nervous System / metabolism*
  • Synapses / metabolism*

Substances

  • Nerve Growth Factor

Grant support

This work was supported by grant from Société Française d'Hypertension Artérielle (SFHTA) to C.G. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.