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Samuel D Hanlon, Ali Behzad, Alan Robert Burns; Fibrillin microfibrillar networks in the mouse cornea: ultrastructural characterization and 3d reconstruction. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1949.
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© ARVO (1962-2015); The Authors (2016-present)
In non-ocular tissues where strength and resiliency are required, the presence of elastin-free fibrillin microfibril bundles (EFMBs or “oxytalan” fibers) contribute to tissue mechanics. EFMBs are present in corneas of various mammalian species including humans where they appear to be involved in embryonic and early post-natal development, as well as some disease states. While it is generally accepted that they do not exist in the mature adult cornea, the present study provides novel evidence of an elaborate 3D network of EFMBs within the cornea of adult mice.
All animals used in this study were C57BL/6 mice between 8-12 weeks of age. Excised corneas were fixed and embedded in resin blocks for histological sectioning. Serial block-face images (100 nm intervals with 500-1000 images/z-stack) were obtained using a Gatan 3View system mounted in a scanning electron microscope. Serial images were manually segmented and 3D reconstructed using Amira 5.2 software. Additional corneas, incubated with anti-fibrillin-1 antibody and fluorescent nanogold conjugated secondary antibody, were imaged with a fluorescence microscope and, after silver enhancement, with a transmission electron microscope (TEM).
3D reconstruction of serial block-face images provided novel ultrastructural evidence of a network of electron dense fibers located within and between collagen lamellae and running roughly parallel with the corneal surface. Immunofluorescence imaging revealed a similar extensive network of fibrillin-positive stromal fibers. TEM imaging showed the electron dense fibers to be composed of 10nm microfibrils, characteristic of fibrillin and also showed fibrillin-specific silver deposits following silver enhancement of the nanogold particles.
In the present study, novel serial block face imaging and 3D reconstruction show clear evidence of an extensive EFMB network in the adult mouse cornea. Previously published reports regarding EFMBs in the corneal stroma have largely concluded they disappear as animals/humans mature, except in disease. Research into corneal biomechanics and corneal disease has largely focused on the properties and arrangement of type I collagen and some of the other minor collagens. However, it may also be necessary to consider the contribution of fibrillin microfibrillar networks, particularly in research involving mouse cornea.
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