Development of a rabbit corneal equivalent using an acellular corneal matrix of a porcine substrate

The tissue equivalent that mimics the structure and function of normal tissue is a major bioengineering challenge. Tissue engineered replacement of diseased or damaged tissue has become a reality for some types of tissue such as skin and cartilage. The tissue engineered corneal epithelium, stroma, and endothelium scaffold are promising concepts in overcoming the current limitations of a cornea replacement with an allograft.

The acellular corneal matrix from porcine (ACMP) was examined as a potential corneal cell sheet frame. The physical and mechanical properties of strength, expansion, transparency, and water content of the ACMP were measured. The major antigens of the cell components were completely removed with series of extraction methods, the major antigens of the cell components were identified by hematoxylin and eosin (HE), immunofluorescence staining, and scanning electron microscopy. The structural properties were investigated by HE stain and scanning electron microscopy. The three types of rabbit corneal cells were cultured in vitro, and characteristics were investigated by colony formation efficiency (CFE), BrdU staining, immunofluorescence staining, and western blot assay of keratin 3 (K3), vimentin, and aquaporin A. The biocompatibility of the ACMP was investigated for one month using rabbit corneal stroma and three types of cultured corneal cells both in vivo and in vitro. The three types of cultured rabbit corneal cells were seeded onto ACMP of each side at a cell density of 5.0 x 10(3) cells/mm(2).

The optical and mechanical properties of the ACMP were similar to the normal porcine cornea. The collagen fiber interconnected to the network, formed regular collagen bundles of the ACMP, and was parallel to the corneal surface. The ACMP was transferred to the rabbit cornea stroma, which showed an intact epithelium and keratocytes in the implant region. There were no inflamed cells or new vessel invasion one month after transplantation. The three types of cultured rabbit corneal cells were positive for K3, vimentin, and aquaporin A. CFE and BrdU (5-bromo-2'-deoxyuridine) staining showed no statistical difference. The cultured rabbit corneal limbal epithelial cells, keratocyte cells, and endothelial cells formed a confluent cell sheet on the ACMP, which consisted of one to two cell layers. Immunofluorescence and scanning electron microscopy examination showed that the cells steadily adhered to the surface of the ACMP and maintained their conformation and special molecule expression such as K3, vimentin, and aquaporin A. Rabbit corneal epithelium-ACMP, keratocytes-ACMP, and endothelium-ACMP scaffold was built in vitro.

The rabbit corneal scaffold was made by the ACMP as a frame with three types of allogeneic rabbit corneal cells. This is a new concept in treating injured corneas.