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Jemin Chae, Joshep Choi, Walter Stark, Jennifer Elisseeff; Extracellular matrix characterization of the acellular gamma-irradiated cornea. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5257.
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To assess and investigate the extracellular matrix (ECM) of the human acellular gamma-irradiated cornea (AGC) with respect to structural, physical, mechanical and biological properties.
The properties of the AGC and the equivalent fresh human cornea (FHC) were evaluated. The structure of corneas were observed by transmission electron microscopy (TEM) and light microscopy. The physical and mechanical properties of ECM were evaluated by differential scanning calorimetry (DSC), compressive modulus testing and light transmission testing. To assess the biological properties, a cell migration test with human keratocytes and a DNA content analysis were performed.
The structural properties of the AGC were generally similar to those of the FHC but the density of collagen fibers in the AGC was lower than that of the HFC and some cell debris was observed. These findings were also supported by light microscopy. The AGC showed a higher light transmission rate, which corresponds with clarity, compared to the FHC across the entire range of the visible light spectrum even though there was no statistical significance. In the compressive modulus test, very similar values of young’s modulus were found between the AGC (25.1 ± 5.8 kPa) and the HFC (24.4 ± 6.4 kPa). However, in the DSC analysis, the transitional temperature (Tm), which shows matrix organization, of the AGC was significantly lower (61.7 ± 1.1C) than that of the HFC (65.7 ± 1.8 C). The DNA content was significantly decreased in the AGC (1.05 ± 0.22 µg / mg), when compared to the HFC (1.90 ± 0.11 µg /mg). In the cell migration test, more keratocytes were able to migrate through the AGC (317± 38.7/mm2) than through the HFC (176.4±48.2/mm2).
In this study, we found the AGC is similar to the HFC with respect to mechanical properties and transparency. In addition, the AGCs allow for more keratocyte migration and include less DNA content than HFCs, properties that are potentially beneficial in corneal substitutes. The gamma-irradiation reduces the density of collagen fibers and changes the thermal properties of melting. However, the effects of gamma irradiation are not great enough to alter the mechanical properties of corneal ECM. This promising corneal substitute could be used in various applications of ophthalmic practice including corneal transplantation, which may not need viable endothelial cells, as well as in glaucoma patch grafting.
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