'Association for Research in Vision and Ophthalmology (ARVO)'
Abstract
Purpose : To characterise and compare the elastic fibre system of mouse and human posterior cornea.
Methods : 4 adult human corneas were obtained from a UK eye bank and 20 corneas taken from 3 month old C5BL/6 mice which had been euthanized. The samples were examined using Serial block face scanning electron microscopy (SBF-SEM) and transmission electron microscopy (TEM). The corneas were fixed and processed for SBF-SEM through a series of staining solutions prior to embedding and polymerization in epoxy resin blocks. The sample blocks were trimmed and transferred to a Zeiss Sigma VP FEG scanning electron microscope equipped with a Gatan 3View system, where data sets of up to 1000 images were acquired of the block surface every 50nm through automated sectioning. Selected serial image sequences were extracted and 3D reconstructions were generated using Amira 6.4 software. For electron microscopy ultrathin sections were prepared and examined in a JEOL 1010 TEM. The corneas were also examined using immunofluorescence labelling of elastin and fibrillin-1.
Results : Immunofluorescence revealed an extensive fibrillin-1-rich microfibril system running throughout the mouse corneal stroma. Human corneas were also positive for fibrillin-1 within the posterior cornea, but in addition exhibited positive elastin staining confined to the posterior peripheral cornea. TEM confirmed the presence of true elastic fibres containing an amorphous elastin core in peripheral human corneas, which were absent within the mouse microfibrils. Clear structural differences at the convergence of the trabecular meshwork (TM) into the elastic fibre system were also observed between mouse and human cornea using SBF-SEM. In mouse cornea the TM merged directly with Descemet’s membrane whereas in human cornea the TM inserted into the elastic fibre system anterior to Descemet’s.
Conclusions : Clear differences exist between the elastic fibre system and TM anatomy of mouse and human cornea. These differences suggest the fibre system of mouse and human have different biomechanical properties and function
