title: Erythropoietin and VEGF promote neural outgrowth from retinal explants in postnatal rats.
abstract: OBJECTIVE
  Recent studies have reported neuroprotective effects of erythropoietin (EPO) and vascular endothelial growth factor (VEGF). The purpose of the present study was to clarify their influence on neurite outgrowth and regeneration of rat retinal ganglion cells (RGCs) in vitro and to elucidate the expression of corresponding receptors in the rat retina in vivo.
  
  
  METHODS
  Retinal explants from postnatal rats were stimulated with VEGF alone; VEGF in combination with anti-VEGF-receptor (VEGF-R)-2 antibody or T-type Ca2+ channel blocker ethosuximide (ESX); EPO alone; or EPO in combination with anti-EPO-receptor antibody or ESX. The presence of the corresponding receptors in the rat retina was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and by immunohistochemistry.
  
  
  RESULTS
  EPO induced a stable improvement of neurite outgrowth of RGCs in a dose-dependent manner (5 x 10(-15) M to 5 x 10(-13) M) up to 169% (P < 0.05). Treatment of the explants with anti-EPO-R antibody (1:80 dilution) and with ESX (5 microM) totally inhibited EPO-mediated effects on RGCs. In comparison, VEGF (50 ng/mL), induced neurite outgrowth of retina explants up to 167% (P < 0.05), which again was inhibited in the presence of anti-VEGF-R2 antibody or ESX. Transcripts of EPO-R, VEGF-R1, and VEGF-R2 were detected by RT-PCR. Intense immunoreactivity for VEGF-R1, VEGF-R2, and EPO-R were found in the RGC layer of the retina.
  
  
  CONCLUSIONS
  The data demonstrate for the first time that EPO and VEGF have a significant and specific biological effect on neurite regrowth of axotomized RGCs. Therefore, these results imply that EPO and VEGF have not only a neuroprotective but also a neuroregenerative role in ischemic retinal conditions.
authors.affiliation: Institute of Anatomy, Christian-Albrechts-University of Kiel, Kiel, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Böcker-Meffert
authors.forename: Philip
authors.initials: P
authors.lastname: Rosenstiel
authors.forename: Claudia
authors.initials: C
authors.lastname: Röhl
authors.forename: Nils
authors.initials: N
authors.lastname: Warneke
authors.forename: Janka
authors.initials: J
authors.lastname: Held-Feindt
authors.forename: Jobst
authors.initials: J
authors.lastname: Sievers
authors.forename: Ralph
authors.initials: R
authors.lastname: Lucius
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D016228:Endothelial Growth Factors / Q000494:pharmacology*; D004921:Erythropoietin / Q000494:pharmacology*; D005013:Ethosuximide / Q000494:pharmacology; D005260:Female; D007150:Immunohistochemistry; D008222:Lymphokines / Q000494:pharmacology*; D008297:Male; D009416:Nerve Regeneration / Q000187:drug effects; D016501:Neurites / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors
chemical_list: D004338:Drug Combinations; D016228:Endothelial Growth Factors; D008222:Lymphokines; D011518:Proto-Oncogene Proteins; D017467:Receptors, Erythropoietin; D017978:Receptors, Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D004921:Erythropoietin; D005013:Ethosuximide; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1