[The expression level of MMP-2 and collagen of hydroxyapatite modified titanium for keratoprosthesis in the corneal stroma of rabbits].

OBJECTIVE: To investigate the expression level of metalloproteinases-2(MMP-2) and Collagen in a hydroxyapatite surfaced-modified of three Pan type titanium keratoprosthesis after that implanted into the corneal stroma of rabbits, further evaluate its biological compatibility. METHODS: Experimental study. Twenty-four New Zealand white rabbits, 2.0-2.5 kg, were respectively divided into three groups. Surgery was performed in right eye of all animals. skirt of HA-Ti and Ti were respectively inserted into the corneal stroma of rabbit of experimental group A and group B; only a sack was made without implantation in control group C . Cornea edema and corneal neovascularization were observed at scheduled times after operation; animals were sacrificed 2, 4 and 16 weeks after operation and their cornea was removed and examined under light microscopy; the surface of skirt was observed under scanning electron microscope. RESULTS: During the study period, all skirts were stable without infected, dissolved and excluded. Different degree of cornea edema and neovascularization was revealed after surgery. MMP-2 were absent in the normal corneal matrix. The expression level of MMP-2 in group A was higher than group C at all time points (F = 6.083, P < 0.05), and was increased than group B at 4th (F = 47.074, P < 0.01), and was increased than group C at 16th weeks too (F = 6.079, P < 0.05) . Corneal organization has a large green 4 weeks type III collagen and yellow red type I collagen, 16 weeks corneal mainly for bright red when within the collagen type I, still have a small amount of collagen type III. CONCLUSIONS: Rabbit cornea implanted HA-Ti skirts cause MMP-2 activation, continuous high expression didn't cause the cornea to dissolve; Collagen -III turned into collagen-I gradually in the extracellular matrix around the skirts. Hydroxyapatite modified titanium for Keratoprosthesis promoted the corneal neovascularization and improve the interfacial bio integration of skirt and host cornea.

[Biocompatible study of modified titanium skirt for keratoprosthesis].

OBJECTIVE: The research is engaged in developing an improved titanium skirt for keratoprosthesis, the aim of this study was to evaluate biocompatible of keratoprosthesis of novel design. METHODS: The pure titanium skirt for keratoprosthesis with three hands were first Sandblasted, and then bioactive hydroxyapatite coated on Sandblasted titanium for keratoprosthesis by a acid-alkali chemical treatment. A total of 18 New Zealand white rabbits and 18 alkali burned rabbit corneas were respectively divided into three groups (Group A, B and C; Group E, F and G) with simple random sampling methods. The modified titanium skirt was inserted into the corneal stroma of Group A and E, and then the control skirt was inserted into Group B and F. Group C and H did not insert skirt as surgery control. The interfacial biointegration of skirt/cornea were examined under light microscopy by HE, TEM and SEM. The transparent center was implanted to rabbit corneas with modified titanium skirt after 3 months. RESULTS: Dense hydroxyapatite coating was deposited on the Sandblasted specimens by an acid-alkali chemical treatment. The number of corneal fibroblasts increased significantly in Group A compared with Group B. The extracellular matrix deposited on the surface of modified titanium skirt was more dense and tight than that of control skirt. There was a significant difference in the shear force of skirt among groups A and B (t = 3.297, P < 0.05), E and F (t = 4.237, P < 0.05), and taking out the skirt in Group A and E were more difficulty than that in Group B and F after 3 months. The observation of the tissue sections of modified skirt inserted eyes revealed that there were cells and collagen-like fibres perpendicular to or at an angle to the rough interface and the cellular function was extremely active, in accordance with the results of TEM. Compared with healthy host tissue, skirt/cornea healing after alkali burn was impaired. CONCLUSIONS: Hydroxyapatite modified Sandblasted titanium skirt for keratoprosthesis can promote the interfacial biointegration of skirt and host cornea, no matter in healthy cornea or diseased cornea (alkali burn cornea). Hydroxyapatite coating improved the bioactivity of titanium.