Study on biocompatibility of complexes of collagen-chitosan-sodium hyaluronate and cornea.

In this study we investigated the biocompatibility of collagen-chitosan-sodium hyaluronate (Col-Chi-NaHA) complexes and cornea tissue, and the feasibility of Col-Chi-NaHA complexes as substrates for cultivating rabbit corneal cells. Different components of Col-Chi-NaHA complexes were prepared and tested. A circular complex film with a diameter of 6 mm was inserted into rabbit stomal pocket and traced for a period of 5 months. Clinical examination was made. Rabbit limbal corneal epithelial cells, corneal endothelial cells, and keratocytes were cultured primarily on complexes. Phase contrast microscope examination was made daily. Histological, immunohistochemical, and scanning electron microscopic examinations were carried out. The complexes of 20% collagen, 10% chitosan, and 0.5% sodium hyaluronate showed rather weak corneal edema and other responses. The degradation of materials was obvious after 5 months. Corneas were transparent and translucent. Cells seeded on Col-Chi-NaHA were allowed to proliferate and partly form confluent monolayer after 9 days in culture. Cultured cells were well attached to the complexes of 20% collagen, 10% chitosan, and 0.5% sodium hyaluronate, or 10% chitosan and 0.5% sodium hyaluronate. The results showed that Col-Chi-NaHA complexes had good biocompatibility with cornea. The complexes can degrade and be absorbed in cornea. Col-Chi-NaHA complex may be a suitable substrate for cultivating corneal cells and a feasible material as a scaffold of tissue-engineered cornea.

Preliminary clinical study on perforating prosthokeratoplasty.

PURPOSE: To observe the effects of perforating prosthokeratoplasty on patients with leucoma who failed in keratoplasty or were not suitable for keratoplasty, and improved their vision. METHODS: Five cases with leucoma (4 with chemical burn and 1 with blast) received Yakimenko Style keratoprosthesis implantation. Preoperative examination showed the visual acuity in 4 of the 5 cases was light perception, and that of the other one was FC/20 cm. The light orientation in 3 patients was definite, and that in the other two was indefinite. RESULTS: The vision improved in 4 of 5 patients in the follow-up period of 9 months to 3 years. Their visual acuity showed 0.09 to 0.8. And there was no change of vision in the other 1 case. CONCLUSIONS: Prosthokeratoplasty is the first choice for rehabilitation of the blind that have leucoma but are not suitable for or failed in penetrating keratoplasty.

[The study of FK506 eye drops preventing and treating immune rejection on limbal allograft transplantation].

OBJECTIVE: To evaluate the general cause of limbal allograft transplantation rejection and the effects of the immunosuppressant FK506. METHODS: Limbal deficiency models were established in 48 New Zealand rabbits, which were randomized into three groups of 16 rabbits each. Limbal allograft transplantation was performed one month later. After transplantation, the FK506 group, the CsA group and the untreated group were treated with FK506 eye drops (0.5 g/L), 1% CsA eye drops and physiological saline, respectively. Graft survival and ocular surface were observed clinically for 10 weeks. Impression cytology was performed on the central cornea of the rabbit one month after limbal ablation, 1 day before allograft transplantation, and two and four weeks after transplantation. The expression of CD25 in peripheral T cells was identified dynamically one day before and one and eight weeks after transplantation. The expression of CD25 on the limbal allograft and lymphocyte infiltration was also identified dynamically the fourth, eighth and tenth week after transplantation. RESULTS: Conjunctivalization of corneal epithelium was found in the limbal deficiency model by impression cytology. Two weeks after limbal allograft transplantation, the central corneal epithelium regained corneal phenotype. Four weeks later, the ocular surface of FK506 group and CsA group continued to express corneal phenotype. Epithelium rejection appeared first in the untreated group (P < 0.05), which had the highest level of the lymphocyte infiltration and the expression of CD25 in peripheral blood and allografts after limbal allograft transplantation (P < 0.05). Epithelium rejection occurred next with the CsA group. FK506 group epithelium rejection occurred last and had the lowest level of the lymphocyte infiltration and the expression of CD25 in peripheral T cell and limbal allografts. CONCLUSIONS: Topically administered FK506 eye drops early after limbal allograft transplantation can delay allograft rejection by effectively inhibiting the expression of CD25 in peripheral T cells and limbal allografts. Also, FK506 is more effective than CsA.