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The integration of microporous polymer into tissues is of great interest for the production of keratoprosthetic devices. Our previous studies showed functional differentiated cells and collagen synthesis in the pore of an expanded polytetrafluoroethylene implant. This study identifies and quantifies collagen types synthesized in the implant. Expanded polytetrafluoroethylene polymers were implanted in the rabbit corneas. The collagen extracted from the polymer and implanted stroma after 1, 3 and 6 months was quantified by measuring hydroxyproline. The relative proportions of collagen types were determined by densitometric analysis after SDS-PAGE. The collagen-to-protein ratio in the polymer increased from 0.22 to 0.70 between the first and third month after implantation becoming similar to control cornea. So that of the protein and collagen densities in the polymer and implanted stroma were similar to the control from the third month. The collagen synthesized in the polymer was mainly type I (87%) plus a small amount of type III (8%) 1 month after implantation. The collagen distribution from the third month after implantation was similar to that of the controls and remained constant thereafter in the polymer implant and in the implanted stroma. Immunogold labelling techniques confirmed these results. Implantation of this PTFE disc induced no obvious modification of the corneal stroma, confirming that this polymer is a good interface that is compatible with the native corneal stroma. The keratocytes in this polymer rapidly adopted a corneal phenotype, distinct from the dermal or scaring phenotype as shown by the collagen types produced in the implant.

Prior to a clinical trial in humans, we studied the effect and pharmacological distribution of recombinant human basic fibroblast growth-factor (Rh-bFGF) in vivo. Healing experiments on de-epithelialized rabbits corneas (n = 24 animals) compared the efficacy of three bFGF doses to controls and revealed a significantly increased healing rate for both 200 ng and 500 ng per application Rh-bFGF treatment groups compared to the control groups. To assess possible side effects of Rh-bFGF (500 ng topically applied for up to 7 days, twice daily), ten rabbits were involved in a model of an anterior keratectomy wound (performed with Draeger's roto-keratome to a depth of 0.15 mm). Light microscopy of thin sections of treated corneas showed an increased fibrogenesis in the anterior stroma with a more pronounced activation of keratocytes. No evidence for abnormal neovascularization or inflammation was observed when compared to control corneas. Ocular penetration and systemic distribution of topically applied labelled 125I FGF was assessed in three models (iodine vapour epithelial burn, anterior keratectomy and penetrating autokeratoplasty) in 24 rabbits. No intraocular penetration of bFGF occurred as shown by direct gamma counting. Macroautoradiography showed a selective labelling of epithelial basement membrane when denuded and intact, as previously described. Evidence for systemic absorption of breakdown products was confirmed by heparin-sepharose chromatography of blood and urine samples. Under these conditions, we suggest that topical Rh-bFGF promotes corneal wound healing without morphological adverse reaction or intraocular and systemic penetration.