Abstract
Purpose: :
We have previously shown that corneal basement membranes (BMs) are composed of different structural components. The adult epithelial BM displays "horizontal" heterogeneity in laminin and type IV collagen isoforms between central area (with Bowman's layer present) and peripheral corneoscleral limbus. Descemet's membrane (DM) shows "vertical" heterogeneity, with different composition of its stromal and endothelial faces. Our purpose was to identify corneal basement membrane changes during postnatal development.
Methods: :
Thirty adult healthy corneas and 10 corneas from six 12–day to 3 year–old children (within 30 h postmortem, obtained from NDRI) were studied by immunofluorescence with antibodies to BM components.
Results: :
Children's corneas had type IV collagen α1/α2 chains in central epithelial BM that changed after 3 years of life to α3/α4 chains, with α1/α2 chains retained only in the limbal BM. Compared to children's corneas, laminin α2 and ß2 chains appeared in the adult limbal BM. In 3 year–old corneas, laminin ß2 chain already had an adult distribution. In children's DM, laminin–10, type IV collagen α1–α6 chains, perlecan, nidogen–1, nidogen–2 and ß–netrin were found on both faces but they all remained only on the endothelial face in adult DM. Stromal face of the children's but not the adult DM stained for tenascin–C (containing A–1 repeat), fibrillin–1, BM–40/SPARC, and laminin–5. DM type VIII collagen shifted from the endothelial face in the children's to the stromal face in the adult, and matrilin–4 completely disappeared after 3 years. Corneas of a 13–year old individual already had adult patterns of all markers studied. We provide the first description of corneal distribution of nidogen–2, ß–netrin, matrilin–2, matrilin–4, and type XXIII collagen.
Conclusions: :
The observed differences may relate to changes in corneal cell adhesion, differentiation and mechanical strength of corneal BMs in the process of postnatal corneal maturation.
Keywords: cornea: epithelium • extracellular matrix • development