Artificial Human Corneas
University of Ottawa, Ottawa, Ontario, Canada Cornea
(Impact Factor: 2.04).
11/2002; 21(7 Suppl):S54-61. DOI: 10.1097/01.ico.0000263120.68768.f8
To review the development of artificial corneas (prostheses and tissue equivalents) for transplantation, and to provide recent updates on our tissue-engineered replacement corneas.
Modified natural polymers and synthetic polymers were screened for their potential to replace damaged portions of the human cornea or the entire corneal thickness. These polymers, combined with cells derived from each of the three main corneal layers or stem cells, were used to develop artificial corneas. Functional testing was performed in vitro. Trials of biocompatibility and immune and inflammatory reactions were performed by implanting the most promising polymers into rabbit corneas.
Collagen-based biopolymers, combined with synthetic crosslinkers or copolymers, formed effective scaffolds for developing prototype artificial corneas that could be used as tissue replacements in the future. We have previously developed an artificial cornea that mimicked key morphologic and functional properties of the human cornea. The addition of synthetic polymers increased its toughness as it retained transparency and low light scattering, making the matrix scaffold more suitable for transplantation. These new composites were implanted into rabbits without causing any acute inflammation or immune response. We have also fabricated full-thickness composites that can be fully sutured. However, the long-term effects of these artificial corneas need to be evaluated.
Novel tissue-engineered corneas that comprise composites of natural and synthetic biopolymers together with corneal cell lines or stem cells will, in the future, replace portions of the cornea that are damaged. Our results provide a basis for the development of both implantable temporary and permanent corneal replacements.
Available from: Sylvain Guérin
- "Epithelial cells need to be cultured either on a support or on a stromal substitute to be air-lifted. So far, there have been reports of air-lifting epithelial cells using uncoated inserts , inserts coated with collagen , or coated with a mixture of collagen, fibronectin, and laminin , amniotic membranes [11,16], collagen gels [17-20], collagen sponges  or hydrogels [22,23]. "
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ABSTRACT: The purpose of this study was to produce and characterize human tissue-engineered corneas reconstructed using all three corneal cell types (epithelial, stromal, and endothelial cells) by the self-assembly approach.
Fibroblasts cultured in medium containing serum and ascorbic acid secreted their own extracellular matrix and formed sheets that were superposed to reconstruct a stromal tissue. Endothelial and epithelial cells were seeded on each side of the reconstructed stroma. After culturing at the air-liquid interface, the engineered corneas were fixed for histology and transmission electron microscopy (TEM). Immunofluorescence labeling of epithelial keratins, basement membrane components, Na+/K+-ATPase α1, and collagen type I was also performed.
Epithelial and endothelial cells adhered to the reconstructed stroma. After 10 days at the air-liquid interface, the corneal epithelial cells stratified (4 to 5 cell layers) and differentiated into well defined basal and wing cells that also expressed Na+/K+-ATPase α1 protein, keratin 3/12, and basic keratins. Basal epithelial cells from the reconstructed epithelium formed many hemidesmosomes and secreted a well defined basement membrane rich in laminin V and collagen VII. Endothelial cells formed a monolayer of tightly-packed cells and also expressed the function related protein Na+/K+-ATPase α1.
This study demonstrates the feasibility of producing a complete tissue-engineered human cornea, similar to native corneas, using untransformed fibroblasts, epithelial and endothelial cells, without the need for exogenous biomaterial.
Available from: Federico Castro-Munozledo
- "During the next years bioengineered substitutes will be available for experimental applications and to replace part or the full thickness of damaged or diseased corneas (Carlsson et al., 2003). These bioengineered substitutes vary from devices that solely address replacement of the cornea's function, to completely natural corneal replacements, or biosynthetic matrices that permit host tissue regeneration (Griffith et al., 2002; Li et al., 2003; Liu et al., 2006). Such devices will also be helpful in assessing the effects of diverse agents, Fig. 1. "
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ABSTRACT: Understanding of visual system function and the development of new therapies for corneal diseases and damages depend upon comprehension of the biological roles of the tissue. The in vitro cultivation of corneal epithelial cells and cell lines derived from them has become a powerful tool to analyze and understand such issues. Currently, researchers have developed well-defined and precisely described culture protocols and a collection of corneal epithelial cell lines. These cell lines have been obtained through different experimental approaches: (1) the ectopic expression of oncogenes, (2) the inactivation of p16 and p53 pathways and hTERT expression, and (3) the spontaneous establishment after serial cultivation of cells. The advantages or disadvantages for these approaches are discussed. In conclusion, the availability of several culture protocols and immortalized cell lines that express corneal epithelial phenotype will be useful for investigating issues such as gene regulation and tissue development, or for validating alternative methods in toxicology.
Available from: link.springer.com
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ABSTRACT: Herein, we reconstructed a rabbit corneal epithelium on a lyophilized amniotic membrane (LAM) using a modified version of
two Teflon rings (the Ahn’s supporter). We compared the corneal epithelial cells we had differentiated in vitro using air-liquid interface (6 days, 12 days) and submerged (6 days, 12 days) cultures and followed a six-day tilting dynamic
air-liquid interface culture with a six-day tilting submerged culture. We characterized the reconstructed corneal epithelium
using digital photography, histological imaging, and transmission electron microscopy. The reconstructed corneal epithelium
created under air-liquid interface culture exhibited a healthier basal corneal epithelial layer than that created under submerged
culture. The reconstructed corneal epithelium on the LAM that was produced using the tilting dymanic culture exhibited a healthy
basal layer. We therefore proposed that tilting submerged culture not only supplied nutrients from the medium to the corneal
epithelial cells on the LAM, but it also removed the horny layer in the upper part of the reconstructed corneal epithelium,
presumably by mimicking the effects of blinking. This study demonstrated that corneal epithelium reconstruction on a LAM using
a tilting submerged culture after a tilting air-liquid interface culture may be useful not only for allogeneic or autologous
transplantation, but also for in vitro toxicological test kits.
Keywordslyophilized amniotic membrane-corneal epithelium-blinking effects-horny layer
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