Abstract
Purpose: :
The composition and distribution of collagens in the human fetal eye is very complex, and little has been documented about the exact localization of specific collagens (Cs) and their possible changes over time. We have investigated the immunolocalization of 4 different Cs during fetal development of the human eye with particular emphasis on the posterior segment.
Methods: :
Immunoreactivity against antibodies to C type IV, V, IX, and XVII was studied in 16 human fetal eyes between 9 and 27 weeks of gestation (male: 8, female: 5, unknown: 3). All eyes were obtained after medical abortion, fixed in paraformaldehyde, and opened horizontally prior to embedding. There was no evidence of ocular disease or abnormality in any of the specimens included in this study. Routine staining with Hematoxylin&Eosin and PAS as well as immunohistochemistry were performed on paraffin sections, and the immunoreaction product was visualized using AEC as chromogen. For comparison, 3 mature eyes (1 enucleated for malignant melanoma, 68ys, 1 for posttraumatic "phthisis", 28ys, 1 post mortem enucleation in a child, 5ys ) were reacted in a similar fashion.
Results: :
For each of the Cs examined there was a distinct staining pattern that remained fairly stable over the time course available for investigation. CIV localized to the basement membrane of vascular structures in the retina, the choroid and the tunica vasculosa lentis. CV labelled retinal vessels more intensely compared to the choroidal vasculature, and in addition it strongly stained the sclera. Bruch's membrane reacted with C IV and partially also with CV. CIX was much less evident in vascular basement membrane but localized to Mueller cell endfeet and the vitreoretinal interface/inner limiting membrane. Another distinct finding was labelling of CIX to the area of the developing outer limiting membrane. With CXVII, no significant immunoreactivity was seen in the posterior part of the eye.In the adult eye, labelling patterns were mostly similar; only CXVII revealed - unlike in the fetal eye - some labelling of Mueller cell endfeet.
Conclusions: :
We present new findings on the distribution of specific collagens in the human fetal eye that allow for further investigation of the precise development of the vascular system and associated structures in the retina as well as in the choroid. CIX appears of particular importance in the development of Mueller cells and their impact on retinal architecture, and CXVII could play a major role during postnatal development.
Keywords: retinal development • immunohistochemistry • choroid