Implantation of Hydroxyapatite–Titanium Corneal Implants in Rat Cornea

PURPOSE:To evaluate the biocompatibility of hydroxyapatite-coated titanium (HA/Ti) corneal implants at the molecular levels with histopathology. METHODS:Eighty Sprague-Dawley rats were divided into 2 equal groups. In the study group, HA/Ti prosthetics were implanted into the right corneal stroma. The control group received a sham incision. Corneas were collected and studied with histopathological examination (HE), immunohistochemical, and other stains, including scanned electron microscopy and reverse transcription-polymerase chain reaction, to evaluate inflammatory reactions, tissue repair, and expression of various biological factors during healing. RESULTS:In the control group, corneal neovascularization occurred 7 days after surgery, and the corneas recovered 28 days after surgery. In the study group, corneal vascularization increased substantially on day 7 and stabilized on day 28. For both groups, reverse transcription-polymerase chain reaction detected expressions of 6 primers at all time points. The amplified sequences were consistent with the designed sequences. The expression of matrix metalloproteinase-2, matrix metalloproteinase-9, bFGF, vascular endothelial growth factor, and type III collagen were delayed in the study group compared with the control group. Histological analyses showed a tight attachment of the corneal tissue to the HA/Ti implant on day 28. CONCLUSIONS:The HA/Ti corneal implants can remain stable in corneal tissue for a long time, induce corneal neovascularization, and stimulate inflammatory cells and keratocytes to synthesize or activate matrix metalloproteinases. Artificial cornea made from this material show enhanced stability and biocompatibility in vivo.