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In the normal rat retina the Thy-1 antigen is a specific marker of ganglion cells, but degeneration of ganglion cells in vivo does not remove completely the expression of Thy-1 in the retina. To reconcile these differences we have postulated that ganglion cell death could induce a glial response including the expression of Thy-1 in Müller cells, the main glial cell type in the retina. Using immunocytochemistry, we have shown that pure cultures of Müller cells were strongly labelled with antibodies against Thy-1. PCR amplification of cDNA reverse transcribed from Müller cell RNA indicated the presence of Thy-1 transcripts. Double labelling experiments with anti-Thy1 and anti-glutamine synthetase, a marker of Müller cells, indicated the presence of both antigens in the same cells. Although Müller cells expressed Thy-1 mRNA and protein when cultured in the absence of neuronal cells, when co-cultured with retinal neurons they were not labelled with antibodies against Thy-1. Our results suggest that Thy-1 is expressed by Müller cells following loss of retinal neurons. Thy-1 may have an important function during glial response to neuron death in retina.

We have studied the ability of bFGF to traverse and be trapped within basement membranes. An extract of EHS tumor (matrigel) coated on culture chamber filters was used as an in vitro model of basement membranes. Our results showed a slow diffusion of bFGF dependent on the amount of low affinity binding sites present within the matrigel. High amounts of bFGF and heparin increased the initial rate of diffusion by displacement of bFGF bound to matrigel. An in vitro corneal endothelium model (endothelial cells overlying matrigel) was also developed. This monolayer, with a weak permeability, decreased the kinetic rate of bFGF diffusion compared with matrigel alone. These results indicate that modulation of bFGF distribution in a tissue by a basement membrane is dependent on bFGF concentration, basement membrane composition, permeability of associated cells, and local presence of heparin. This selective control may be a regulating step in bFGF action.

aFGF expression was studied in normal and regenerating cornea of adult rats. aFGF mRNA and proteins were expressed mainly in corneal epithelium but not in stroma. After burning of the epithelium by iodine vapours, the intact epithelial cells migrated to cover the wounded area during the first 4 days and then divided to reconstitute a normal multilayered epithelium 6 days after injury. aFGF mRNA localized by in situ hybridization on regenerating epithelium showed a peak between 6 hr and 2 days after denudation, decreasing to basal levels 6 days later. This induction of aFGF mRNA preceded the increased amount of aFGF peptides, as assessed by indirect immunofluorescence staining. Thus aFGF overexpression is clearly correlated with active migration in epithelial wound healing.

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