Butovich, I. A. | bioRxiv Science

bioRxiv2025

Lipid composition determines thermotropic properties of meibum of animals and humans with Meibomian gland disorders

Meibum - a lipid-rich secretion produced by holocrine Meibomian glands (MG) - plays a central role in maintaining ocular surface homeostasis. Previously, changes in MG lipidomes induced by inactivation of critical genes of meibogenesis, such as Elovl3, Soat1, Awat2, and others, were shown to cause MG-dysfunction- and dry eye-like signs in mice. Here, we describe the impact of the lipid composition of meibum on its physiological properties, specifically thermotropic/melting characteristics, using various wild type and mutant animals, and compare them with meibum of healthy humans and patients with abnormal meibum. Meibum samples were analyzed using liquid chromatography/mass spectrometry (LC/MS) and differential scanning microcalorimetry (DSC). We found that changes in the balance between major lipid classes in meibum - wax esters, cholesteryl esters, triacylglycerols and free cholesterol - cause detrimental changes in its properties, leading to the loss of cohesiveness, abnormal expressibility from MG, a decline in its protective functions, and, ultimately, abnormal phenotypes of the eyes and adnexa. We conclude that tested animal species can be valuable models for studying human diseases. A combination of LC/MS and DSC can be a powerful diagnostic tool and may help to determine the molecular reasons of various pathologies in human subjects and animals.

biochemistry↗

bioRxiv2022

Primary cilia regulate Meibomian glands development and dimensions without impairing the lipid composition of the meibum

PurposePrimary cilia regulate the development of various ectoderm-derived tissues, including the corneal epithelium, skin, hair follicle and sebaceous glands. We aimed to investigate their role in meibomian gland (MG) development. MethodsPrimary cilium ablation in MGs was achieved by crossing a floxed Ift88 mouse (Ift88fl/fl) with a mouse expressing the Cre recombinase under the keratin 14 (K14) promoter, to generate K14-Cre;Ift88fl/fl mice. MG morphology was evaluated by histology and immunostaining, as well as lipid staining and 2-photon microscopy on whole mount tarsal plates. MG lipid profiles were assessed by chromatography. ResultsWe showed that most of MG cells are ciliated during early stages of MG development and that MG ciliated rate decreases throughout morphogenesis. In morphologically mature glands, only the MG central duct and ductules are ciliated, and meibocytes lose their cilia as they differentiate and become filled with lipids. Primary cilium ablation induces enlargement of MGs, dilation of the MG central duct, and an increased production of lipids, without dramatically changing the lipid profiles. In addition, primary cilia regulate MG elongation and the spatial distribution of proliferating and dying cells within MGs, without changing the total cell proliferation and death rates. ConclusionsThese findings indicate that primary cilia are not necessary for normal MG development. However, they promote MG enlargement and lipid production, suggesting that primary cilia could be an interesting target for treatments of ocular surface diseases involving MGs, like dry eye disease.

developmental biology↗