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| May 2005 | Inside IOVS | Volume 46/5 |
Using ESI-MS/MS to Quantify Corneal KS and CS/DS Sulfated Disaccharides
Zhang et al. (p. 1604) describe a rapid, simple, accurate, and sufficiently sensitive mass spectrometric method that even the amount of extracellular matrix present in single sections of embryonic corneas provides sufficient material for the analysis of KS and CS/DS sulfated disaccharides. Their data suggest that the described method can be used to analyze the respective sulfated disaccharides released from various biological tissues other than the cornea. An important potential application of this method may be in the diagnosis of diseases related to KS and CS/DS, and in response to surgical procedures, such as LASIK and LASEK protocols in the cornea.
A Novel Tissue Engineering Approach for Ocular Surface Reconstruction
Currently, there is no autologous corneal epithelial stem cell source for patients with bilateral total limbal stem-cell deficiency. Hayashida et al. (p. 1632) evaluated the possibility of a new approach for ocular surface reconstruction using autologous oral mucosal epithelial stem cells expanded ex vivo on temperature-responsive cell culture surfaces. All cultured oral epithelial cells were nonenzymatically harvested as intact transplantable sheets by temperature reduction to 20°C. Cell sheets retain putative progenitor cells, and autologous transplantation to rabbit corneal surfaces demonstrated successful reconstruction with restoration of transparency. Promising clinical applications for autologous tissue-engineered epithelial cell sheets for ocular surface reconstruction are therefore potentially available.
Reduced Retinal Blood Flow Velocity after Smoking
Darkness normally induces an increased flow velocity in the central retinal artery and smokers are known to have reduced dark vision after smoking. Havelius et al. (p. 1698) studied 20 smokers and 20 non-smokers who were exposed to darkness as a "provocation test." The smokers were found to have a strongly decreased capacity to increase the retinal blood flow velocity in darkness. The finding probably explains the reduced dark vision after smoking and reflects the combined actions in smokers of increased blood viscosity, vasoconstriction of nicotine and reduced capacity of the blood to transport oxygen.
The IMPDH1 Gene and Dominant Retinitis Pigmentosa
The IMPDH1 gene is one of more than ten genes that can cause dominant retinitis pigmentosa. Clinicians are striving to find clinical differences that distinguish patients with disease caused by different retinitis pigmentosa genes. This study by Wada et al. (p. 1735) found that IMPDH1 mutations accounted for only approximately 2% of dominant retinitis pigmentosa cases, but in those patients the remaining functional retina appeared to produce more electrical activity than the retina in patients with dominant retinitis pigmentosa caused by other genes (RHO and RP1) that were evaluated.
Mitochondrial Dysfunction, RPE Cells, and Macular Degeneration
Mitochondrial dysfunction from aging or disease has been shown to cause changes in nuclear gene expression which compensate for the defect and result in increased cell survival. Miceli and Jazwinski (p. 1765) demonstrate that ARPE-19 cells with dysfunctional mitochondria upregulate genes associated with age-related macular degeneration (AMD). Since mitochondrial dysfunction in the retinal pigment epithelium has been suggested as one of the possible causes of AMD, these changes may help explain the unique aging phenotype seen in the RPE that leads the development of the disease.
Defects in the p53 Pathway in Uveal Melanoma
Uveal melanoma is often treated with radiation therapy. However, this cancer is extremely radioresistant and must be treated with high doses of radiation that frequently result in ocular damage and vision loss. The p53 tumor suppressor pathway plays a key role in the cellular response to radiation. Sun et al. (p. 1561) found that p53 is not mutated and responds normally to radiation in uveal melanoma cell lines. However, defects in downstream components of the p53 pathway are ubiquitous. This finding could lead to new therapeutic approaches aimed at rendering uveal melanomas more sensitive to radiation.
Corneal Stromal Precursor Cells Express Neural Cell Markers
Uchida et al. (p. 1620) isolated human corneal stromal precursor cells and demonstrated that they express neural cell markers. When the sphere-forming assay, well known as the method for the isolation of stem cells or progenitor cells, was used, human corneal stromal cells formed sphere colonies and cells migrated from the sphere colonies in vitro. The sphere colonies and the migrated cells expressed neural cell markers. The sphere-forming technique might be a useful method for the isolation of such cells from human cornea.
Long-Term Propagation of Keratocytes by Sphere Cultures
Yoshida et al. (p. 1653) describe a serum-free mass culture system for mouse keratocytes in which the dendritic morphology can be maintained for over 12 passages and can be differentiated into the fibroblastic and myofibroblastic phenotypes as observed in situ. P 12 keratocytes possess the same gene expression profile of keratocan, CD 34 and ALDH as primary seeded cells plated on plastic. This technique allows for the cultivation of sufficient cells from mouse tissue for investigating the biology of corneal stromal cells using a wide range of antibodies and transgenic mice previously not possible with larger mammals and human tissue.
Quantifying Change in Topography Images
Statistic image mapping is widely used in neuroimaging to quantify changes in images of the brain. Patterson et al. (p. 1659) apply this novel pixel-by-pixel analysis to longitudinal series of optic nerve head images. The techniques are shown to have better power at detecting structural changes as compared to current techniques. The technique requires no confirmatory tests, no normative database, and provides the clinician with a rate of change parameter. Results suggest that statistic image mapping may be clinically useful in monitoring patients with glaucoma.
Human RPE Cell Survival Factor Expression
RPE cell survival is crucially important in the normal eye and in diseases such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR). The nuclear transcription factor (NF)-kB is a major regulator of cell life and death. Tumor necrosis factor (TNF)-a is an important cytokine associated with AMD and PVR. Yang et al. (p. 1755) show that multiple survival factors are expressed in cultured as well as in situ human RPE cells. For some of these factors, TNF-a regulates expression in an NF-kB-dependent manner, while others are not influenced by TNF-a. RPE cell survival factors may protect RPE cells from cell death normally and in diseases such as AMD and PVR.
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