Human epicardial cell-conditioned medium contains HGF/IgG complexes that phosphorylate RYK and protect against vascular injury

Cardiovasc Res. 2015 Jul 15;107(2):277-86. doi: 10.1093/cvr/cvv168. Epub 2015 May 29.


Aims: The aim of this study was to evaluate the paracrine activity of human epicardial-derived cells (hEPDCs) to screen for secreted vasoprotective factors and develop therapeutics to treat vascular reperfusion injury.

Methods and results: Epicardial cells support cardiac development, repair, and remodelling after injury in part, through paracrine activity. We hypothesized that secreted ligands from hEPDCs would protect vascular integrity after myocardial infarction (MI) with reperfusion. During simulated ischaemia in culture (24-48 h), concentrated hEPDC-conditioned medium (EPI CdM) increased survival of primary cardiac endothelial cells. In a rat MI model, EPI CdM treatment reduced vascular injury in vivo after reperfusion. By phospho-receptor tyrosine kinase (RTK) arrays, ELISA, and neutralizing antibody screens, we identified hepatocyte growth factor (HGF) as a key vasoprotective factor in EPI CdM. Unexpectedly, we observed that some of the HGF in EPI CdM formed complexes with polyclonal IgG. Following reperfusion, preparations of HGF/IgG complexes provided greater vascular protection than free HGF with IgG. HGF/IgG complexes localized to blood vessels in vivo and increased HGF retention time after administration. In subsequent screens, we found that 'related to tyrosine kinase' (RYK) receptor was phosphorylated after exposure of cardiac endothelial cells to HGF/IgG complexes, but not to free HGF with IgG. The enhanced protection conferred by HGF/IgG complexes was lost after antibody blockade of RYK. Notably, the HGF/IgG complex is the first 'ligand' shown to promote phosphorylation of RYK.

Conclusion: Early treatment with HGF/IgG complexes after myocardial ischaemia with reperfusion may rescue tissue through vasoprotection conferred by c-Met and RYK signalling.

Keywords: EPDC; Epicardial; HGF; Myocardial infarction; Precursor cell; Progenitor cell; Reperfusion.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Hepatocyte Growth Factor / immunology
  • Hepatocyte Growth Factor / metabolism*
  • Humans
  • Immunoglobulin G / immunology
  • Male
  • Myocardial Infarction / metabolism*
  • Myocardial Ischemia / metabolism
  • Rats, Inbred F344
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Vascular System Injuries / metabolism*


  • HGF protein, human
  • Immunoglobulin G
  • Hepatocyte Growth Factor
  • RYK protein, human
  • Receptor Protein-Tyrosine Kinases
  • Ryk protein, rat