Differential Expression of Vascular Endothelial Growth Factor Implies the Limbal Origin of Pterygia
Received 23 September 2004; accepted 3 January 2005. published online 09 May 2005.
Objective
To study the distribution of isoforms of vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 in pterygia and to compare it with that in healthy conjunctivas.
Design
Nonrandomized comparative (cadaver controlled) study with histopathologic correlations.
Methods
Tissue specimens from 75 patients treated for primary pterygia were analyzed using immunohistochemical studies as well as different molecular biological examinations. Healthy conjunctivas from 33 patients treated for cataracts as well as specimens from the conjunctiva, limbus, and lens of both eyes of 12 body donors served as controls.
Testing
Surgical specimens of pterygia and normal conjunctiva specimens were processed with paraffin, sectioned, stained using specific antibodies against VEGF and its receptors, and examined by light microscopy. The other part of both groups of specimens as well as specimens from body donors were prepared and analyzed by means of reverse-transcription polymerase chain reaction (RT-PCR), real-time RT-PCR, enzyme-linked immunosorbent assay, and Western blots.
Main Outcome Parameters
Vascular endothelial growth factor and VEGFR1 and VEGFR2 were analyzed to indentify the splice variants of VEGF as well as the distribution and amount of VEGF and both receptors in pterygia and the control tissues.
Results
In analysis of specimens from pterygium patients as well as normal conjunctivas, VEGF121 and VEGF165 were identified as the only VEGF splice forms expressed. In addition to VEGF, VEGFR1 and VEGFR2 were detected in pterygia and conjunctivas and immunostained within the epithelium of pterygia and conjunctivas and on intrapterygial and intraconjunctival endothelial cells. Levels of VEGFR1 and VEGFR2 mRNA were lower in pterygia than in conjunctivas but similar in limbal and pterygium samples. Vascular endothelial growth factor levels were higher in pterygia than in conjunctivas, but were similar in the limbus and pterygia.
Conclusions
The results reveal similar behaviors in limbal and pterygium epithelial cells in terms of VEGF and VEGFR expression, with the presumption that pterygia arise from limbal epithelial cells and that human conjunctivas are not a suitable control for the analysis of pterygia. Moreover, the results suggest that VEGF might play an active role in the physiology of conjunctival epithelial cells.
1Department of Anatomy, Christian Albrecht University of Kiel, Kiel, Germany.
2Department of Ophthalmology, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
3Department of Anatomy and Cell Biology, Martin-Luther University of Halle-Wittenberg, Halle, Germany.
4Department of Ophthalmology, Christian Albrecht University of Kiel, Kiel, Germany.
5Department of Ophthalmology, University of Lübeck, Lübeck, Germany.
Reprint requests to Prof Dr Friedrich Paulsen, Department of Anatomy and Cell Biology, Grosse Steinstrasse 52, D-06097 Halle (Saale), Germany.
Manuscript no. 2004-134.
Supported by the Deutsche Forschungsgemeinschaft (German Research Foundation), Bonn, Germany (program grant no.: PA 738/6-1) and the Wilhelm Roux program, Halle, Germany (FKZ 9/17).
ABSTRACT