Comparative experiments for in vivo fibroplasia and biological stability of four porous polymers intended for use in the Seoul-type keratoprosthesis

Abstract

Aims: To evaluate in vivo fibroplasia and biological stability of porous polymers intended for use in the Seoul-type keratoprosthesis (S-KPro).

Methods: Four porous polymers (polypropylene, two kinds of polyethylene terephthalate (PE70 and PE50), and polyurethane) were investigated. Discs of polymers were inserted into the corneal stroma of rabbits for a 2 and 5 month period. Corneal oedema and neovascularisation were evaluated. The fibroplasia and collagen deposition were examined under light and transmission electron microscopy. S-KPros, whose skirt was made of four types of polymer, were implanted into the rabbits' eyes. The retention time and complications were evaluated.

Results: Neovascularisation and corneal oedema were found in all of the disc inserted eyes, but the corneal oedema subsided within 2 months in most of the eyes. The mean number of fibroblasts increased significantly in polypropylene and PE50 disc inserted eyes compared with polyurethane disc inserted eyes. Plentiful collagen deposition was also found in both polypropylene and PE50 disc inserted eyes. Mean retention time in the polypropylene SK-Pro implanted eyes was longer than that of the other eyes (20.7 weeks). The PE70 skirt induced corneal melting around the prosthesis.

Conclusion: Polypropylene encourages fibroblast ingrowth and shows good biological stability when used as a skirt material in S-KPro.

Figure 1

(A) Schematic design of the S-KPro. (B) Schematic illustration showed the double fixed method. It includes suturing of a skirt to the cornea and fixation of the haptics to the sclera.

Figure 2

Scanning electron microscopy demonstrated that the pore diameter of all the given polymers was larger than 30 μm to allow fibroblast invasion. (A) Polyethylene terephthalate (PE70; C307NW), (B) polyethylene terephthalate (PE50; K205NW), (C) polypropylene (Q2030NW), (D) polyurethane.

Figure 3

Transmission electron microscope showed collagen accumulation 2 months postoperatively in the polymer that was implanted into the cornea. Black arrows indicate collagen deposition. (A) Polyethylene terephthalate (PE70; C307NW) (×8100), (B) polyethylene terephthalate (PE50; K205NW) (×5800), (C) polypropylene (Q2030NW) (×5800), (D) polyurethane (×4500).

Figure 4

Histological findings of the corneas after polymer insertion for fibroplasia and collagen accumulation 5 months postoperatively. (A–C) Haematoxylin and eosin staining (×400). Arrows indicate fibroblasts. The arrowheads indicate giant cells (histiocytes). (A) Polyethylene terephthalate (PE50; K205NW), (B) polypropylene (Q2030NW), (C) polyurethane. (D–F) Vimentin staining (×400). Arrows indicate a cytoplasmic stained fibroblast. (D) Polyethylene terephthalate (PE50; K205NW), (E) polypropylene (Q2030NW), (F) polyurethane. (G–I) Masson-Trichrome staining (×400). Arrows demonstrate collagen deposition. (G) Polyethylene terephthalate (PE50; K205NW), (H) polypropylene (Q2030NW), (I) polyurethane.

Figure 4

Histological findings of the corneas after polymer insertion for fibroplasia and collagen accumulation 5 months postoperatively. (A–C) Haematoxylin and eosin staining (×400). Arrows indicate fibroblasts. The arrowheads indicate giant cells (histiocytes). (A) Polyethylene terephthalate (PE50; K205NW), (B) polypropylene (Q2030NW), (C) polyurethane. (D–F) Vimentin staining (×400). Arrows indicate a cytoplasmic stained fibroblast. (D) Polyethylene terephthalate (PE50; K205NW), (E) polypropylene (Q2030NW), (F) polyurethane. (G–I) Masson-Trichrome staining (×400). Arrows demonstrate collagen deposition. (G) Polyethylene terephthalate (PE50; K205NW), (H) polypropylene (Q2030NW), (I) polyurethane.

Figure 5

A well placed S-KPro made of a polypropylene skirt after 15 months.