Abstract
Purpose: :
VEGF165 elevates permeability, proliferation and migration rates of retinal endothelial cells (REC) and these effects are completely restored by the VEGF-binding Fab-fragment ranibizumab. Whereas basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1) or placental-growth factor-1 (PlGF-1) as single agents do not influence endothelial barrier function after treatment for 2 d, the effect of PlGF-2 is unclear. Here we investigated whether combination of growth factors enhance or diminish the long-term effect of VEGF165/121 on barrier function and whether combined effects can be restored by VEGF-inhibition alone. In addition we studied whether stimulation of proliferation or migration rates by VEGF in concert with bFGF, IGF-1, PlGF-1/-2 can be inhibited by ranibizumab.
Methods: :
Influence of growth factor combinations on transendothelial resistance (TER) of immortalized bovine REC (iBREC) was measured over several days. Expression of Claudin-1, as an additional indicator of functional tight junctions, was assessed by Western blot analyses. Influence of growth factor combinations on proliferation and migration rates of iBREC was studied in the presence and absence of ranibizumab.
Results: :
PlGF-2 like PlGF-1 as single agent did not influence TER or expression of Claudin-1 during treatment of iBREC for 2 days. In combination with VEGF165, PlGF-2/-1 neither diminished nor enhanced VEGF's effects on TER or Claudin-1 expression. Interestingly, TER and Claudin-1 expression reduced by treatment with a combination of all growth factors for 2 days was completely restored by addition of ranibizumab. In contrast to proliferation which was stimulated by all growth factors tested, iBREC migration was not influenced by PlGF-1/-2 or VEGF121. Whereas migration stimulated by combination of VEGF, PlGF, bFGF and IGF-1 was significantly inhibited by ranibizumab, the VEGF-inhibitor did not effect proliferation stimulated by this growth factor combination.
Conclusions: :
VEGF but not PlGF impairs barrier function of retinal endothelial cells. Whereas VEGF-inhibition is sufficient to completely restore elevation of permeability induced by a combination of VEGF165/121 with PlGF, bFGF and IGF-1, migration or proliferation stimulated by combination of these factors can not be inhibited completely by VEGF-inhibition alone.
Keywords: diabetic retinopathy • growth factors/growth factor receptors • pump/barrier function