Adenosine stimulates canine retinal microvascular endothelial cell migration and tube formation.
OBJECTIVE
To evaluate the effects of adenosine and related substances on events that occur during vasculogenesis and angiogenesis, using in vitro assays.


METHODS
Adenosine (ADO), inosine (INO, an adenosine catabolite), and 5'-(N-ethylcarboxamido) adenosine (NECA, an adenosine agonist) were evaluated for their effect on the proliferation of canine retinal microvascular endothelial cells (DRME), using a cell count assay. Also, these substances and ADO receptor selective agonists and antagonists were evaluated in an assay for DRME chemokinesis by measuring random migration into a wound made in a confluent cellular monolayer. Finally, the effects of these substances on DRME cord formation were evaluated in a 3-dimensional collagen gel. Bovine retinal extract (RE) was used as a positive control for all assays.


RESULTS
There was no effect on proliferation of DRME by any of the substances related to adenosine, but VEGF yielded a 30% stimulation of proliferation. Retinal extract, 10 microM ADO and 1.2 nM VEGF stimulation of DRME migration was 2- to 2.5-fold greater than 10 microM INO yielded. In addition, a combination of 1.2 nM VEGF with 10 microM ADO exceeded the stimulation in migration by ADO only and VEGF only. The total length of tubes formed in the presence of 10 microM ADO was comparable to that formed in the presence of RE and was 11-fold greater than with 10 microM INO. Tube length with a combination of VEGF plus ADO was 36% greater than with retinal extract. Use of selective ADO receptor antagonists suggested that tube formation and the migration response may be mediated through both adenosine A1 and A2 receptors, but use of selective ADO agonists suggests that A2 receptors may be more important than A1 for endothelial cell migration.


CONCLUSIONS
This in vitro analysis suggests that adenosine may stimulate retinal vasculogenesis, an event which involves migration of angioblasts and their assembly into vascular cords, prior to canalization.
Lutty
G A
GA
Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. galutty@welchlink.welch.jhu.edu
Mathews
M K
MK
Merges
C
C
McLeod
D S
DS
D000241:Adenosine / Q000494:pharmacology*; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D004285:Dogs; D016228:Endothelial Growth Factors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects; D007288:Inosine / Q000494:pharmacology; D008222:Lymphokines / Q000494:pharmacology; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D012171:Retinal Vessels / Q000166:cytology* / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014665:Vasodilator Agents / Q000494:pharmacology*
D016228:Endothelial Growth Factors; D008222:Lymphokines; D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014665:Vasodilator Agents; D019830:Adenosine-5'-(N-ethylcarboxamide); D007288:Inosine; D000241:Adenosine