Dry eye disease is a common condition associated with age-related meibomian gland dysfunction (ARMGD). We have previously shown that ARMGD occurs in old mice, similar to that observed in human patients with MGD. To begin to understand the mechanism underlying ARMGD, we generated transcriptome profiles of eyelids excised from young and old mice of both sexes.

Current immunofluorescence protocols are limited as they do not provide reliable antibody staining within large tissue volumes (mm(3)) and cannot localise and quantify multiple antigens or cell populations in the same tissue at high resolution. To address this limitation, we have developed an approach to three-dimensionally visualise large tissue volumes (mm(3)) at high resolution (<1 µm) and with multiple antigen labelling, for volumetric and quantitative analysis. This is made possible through computer reconstruction of serial sectioned and sequentially immunostained butyl-methyl methacrylate (BMMA) embedded tissue. Using this novel immunofluorescent computed tomography (ICT) approach, we have three-dimensionally reconstructed part of the murine lower eyelid that contains the meibomian gland and localised cell nuclei (DAPI), Ki67 and cytokeratin 1 (CK1), as well as performing non-linear optical (NLO) microscopy imaging of collagen, to assess cell density, cell proliferation, gland keratinisation and gland volume respectively. Antigenicity was maintained after four iterative stains on the same tissue, suggesting that there is no defined limit to the number of antigens that can be immunostained for reconstruction, as long as the sections remain intact and the previous antibody has been successfully eluted. BMMA resin embedding also preserved fluorescence of transgenic proteins. We propose that ICT may provide valuable high resolution, three-dimensional biological maps of multiple biomolecules within a single tissue or organ to better characterise and quantify tissue structure and function.

Meibomian gland dysfunction (MGD) is frequent with aging and is the primary cause of dry eye disease, the most prevalent ocular complaint. We used a novel 3-D reconstruction technique, immunofluorescent computed tomography (ICT), to characterize meibomian gland keratinization and cell proliferation in a mouse model of age-related meibomian gland dysfunction (ARMGD). To visualize the changes associated with ARMGD, 5-month and 2-year old mouse eyelids were 3-D reconstructed by ICT using antibodies to cytokeratin (CK) 1, 5 and 6 and the proliferation marker Ki67. We quantified total gland, ductal and lipid volume from the reconstructions, observing a dramatic decrease in old glands. In young glands, proliferative ductules suggest a potential site of acinar progenitors that were found to be largely absent in aged, atrophic glands. In the aged mouse, we observed an anterior migration of the mucocutaneous junction (MCJ) and an absence of hyper-keratinization with meibomian gland atrophy. Thus, we propose that changes in the MCJ and glandular atrophy through a loss of meibocyte progenitors are most likely responsible for ARMGD and not ductal hyper-keratinization and gland obstruction.