| ObjectiveTo analyze the long-term biocompatibility following the implantation of Ti-frame keratoprosthesis, and to investigate the effect of nano-structural HA-coating by aerosol deposition (AD) method on soft tissue bonding, cell activity and corneal healing response.Methods1.85 patients (85 eyes) who received MICOF keratoprosthesis surgery from January 2000 through December 2009 in General Hospital of PLA were studied retrospectively. Postoperatively, the corneal melting, tissue proliferations anterior to and posterior to the optical cylinder of KPro were observed and treated. The tissue around KPro and superficial tissue proliferation (STP) were investigated by histological and immunohistochemical methods.2. Thirty-six samples (10×40mm) were made of pure-Ti, and two methods, aerosol deposition (AD) and Ion beam assisted deposition (IBAD) were employed to form nano-hydroxyapatite coating on pure-Ti surface. Surface features were analyzed by SEM and AFM. The coated and uncoated titanium implants were surgically inserted into the rabbit paraspine muscles. Soft-tissue attachment was evaluated by pull-out testing using a universal testing device. Rupture forces were registered and compared, after which the implants and muscles were examined by SEM and histological analysis respectively.3. The samples (10×10×0.13mm) made of pure-Ti were divided to three groups, AD and IBAD methods were applied for surface modification on Ti. Cell morphology was studied using scanning electron microscopy, and cell proliferation was analyzed by MTT at different timepoint. Cell migration was studied by scratch wound assay. The expression ofβ4 integrin was studied by RT-PCR and flow cytometry. 4. Twenty-four coin-shaped samples (3-mm diameter,130-μm-thick) made of pure-Ti were divided into two groups, AD group and control group. Samples in AD group were modificated by aerosol deposition. All samples were implanted into healthy rabbit cornea and followed up by AS-OCT for 12 weeks. After 1 week,4 weeks, and 12 weeks, the eyes were enucleated, and analyzed by histological methods.Results1. Postoperatively,74 eyes (87%) obtained visual acuity of 20/200 or better,37.6% (32/85) patients occurred stromal melting,25.9%(22/85) patients presented superficial tissue proliferation, and 17.6%(15/85) presented RPM during the follow-up. Histologically, the superficial membrane was composed of proliferative epithelium and fibrovascular tissue incorporating inflammatory cells. The immunohistochemical staining demonstrated increased expression of PCNA in the epithelium, compared with control cornea and conjunctiva. some CD45RO(+)T cells, CDllc(+)dendritic cells, and CD68(+)macrophages were detected.2. The three groups showed distinctive surface morphologies. HA-coating groups developed a high pull-out force compared with control group, significantly (P<0.01). Higher rupture forces were measured for AD coated implants than IBAD coated implants. The implants were encapsulated by a fibrous tissue.3. Keratocyte tended to be thinner shaped on pure-Ti surface, while on AD-coating, cell spreaded well and migration was superior to IBAD-coating.β4 integrin expression was highest on AD-coating surface among three groups.4. The AD-Ti implants were retained stably in the rabbit cornea, while the corneal stroma anterior to implants became thinner in the control group. There was no encapsulation in all cases. Some fibroblasts and a few eosinophis were showed around the periphery of the implants.Conclusions1. Stromal melting was the most common complication which related to the biocompatibility and threatened anatomical success.2. The mechanical attachment on soft tissue of the implant was increased by nano-HA-coating.3. Nano-structural HA-coating on Ti surface can improve cell spreading, migration, and increase the expression ofβ4 integrin.4. AD-Ti implants were very well tolerated in the rabbit cornea. |
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