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N. Beecher, S. Chakravarti, J. Paul, K.M. Meek, A.J. Quantock; Stromal Structure in the Mouse Cornea at Eye-Opening and the Effect of a Lumican-Null Mutation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2144.
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Purpose: Lumican is a small leucine-rich repeat proteoglycan (SLRP) found in various collagenous connective tissues such as cornea. Lumican and other SLRPs are thought to bind collagen and have been implicated in the regulation of collagen fibril diameter and arrangement in collagenous matrices. Our current research focuses on ascertaining the collagenous architecture of wild-type and transgenic neonatal mouse corneal stroma before, during, and after eye-opening. Methods: Corneas from young wild-type and lumican-null mice (neonatal days 8, 12, and 14) were excised and immediately immersed in fixative. Specimens were subsequently studied by synchotron x-ray diffraction to obtain information regarding the average spacing of collagen fibrils in the tissues. Results: Average interfibrillar Bragg spacing in the corneas of 8 day-old wild-type mice (n=6) were just below the value of 48nm found previously in the corneas of 6 month-old wild-type mice when examined in this manner. In two of three 12 day-old corneas, collagen spacing was elevated. At post-natal day 14, three of the four corneas examined had average interfibrillar spacings below 45nm. It was established that collagen interfibrillar Bragg spacing in the corneas of 8 day-old mice homozygous for a null mutation in lumican (n=6) were consistently higher than in the corneas of their age-matched counterparts. Conclusions: Recent work with neonatal mice has indicated that the cornea is thicker just before eye-opening (day 12) than at times just before and after this period. Our data suggests that, in most cases, this may be due to an increase in the average collagen interfibrillar distance. The finding that average collagen interfibrillar spacings were consistently higher in the corneas of lumican deficient mice than they were at this time in the corneas of wild-type mice is supportive of a structural role for lumican early in corneal stromal development.
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