Inhibition of Gli1 suppressed hyperglycemia-induced meibomian gland dysfunction by promoting pparγ expression.

Diabetes is one of the risk factors for meibomian gland dysfunction (MGD); however, the underlying molecular mechanism remains unknown. The current study aims to examine the effects of glioma-associated oncogene homolog 1 (Gli1), a transcription factor of the sonic hedgehog (Shh) pathway, in the modulation of diabetic-related MGD. Here, using RNA sequencing and qRT-PCR, we examined the mRNA changes of Shh pathway involving genes. mRNA sequencing analysis showed that the Shh pathway involving genes Shh and Gli1 were markedly upregulated in diabetic MG, and qRT-PCR detection of Shh pathway-associated genes found that Gli1 expression increased most significantly. Contrary to the elevation of Gli1 level, the expression of pparγ was downregulated in diabetic MG and in high glucose treated organotypic cultured mouse MG. GANT61, an inhibitor of Gli1, effectively inhibited the reduction of pparγ expression and lipid accumulation induced by high glucose, which was suppressed by pparγ inhibitor T0070907. We further demonstrated that advanced glycation end products (AGEs) treatment also promoted the expression of Gli1 and pparγ in organotypic cultured mouse MG. AGEs inhibitor Aminoguanidine suppressed high glucose caused Gli1 upregulation in organotypic cultured mouse MG. These results suggest that suppression of Gli1 may be a potentially useful therapeutic option for diabetic-related MGD.

Hedgehog Signaling Pathway Regulates the Proliferation and Differentiation of Rat Meibomian Gland Epithelial Cells.

Purpose: Meibomian glands play a vital role in maintaining ocular surface stability. This study aimed to investigate whether Hedgehog signaling is involved in the regulation of meibomian gland epithelial cells. Methods: Rat meibomian glands epithelial cells (RMGECs) were isolated from ducts and ductules, and then were cultivated to passage two on Matrigel coated wells in meibomian gland epithelial cells medium (MGECM). Cells were switched from MGECM to differentiation medium (DM) or DM added 10 µg/mL azithromycin (DM + AZM) when reached 50% to 60% confluence. The effects of the Smoothened (Smo) agonist (Smo agonist [SAG]) and antagonist (by cyclopamine) on RMGECs were analyzed using quantitative RT-PCR, cell proliferation analysis, immunofluorescence staining, and Nile red staining. Results: The Hedgehog receptor, Smo, and its downstream molecules, Glis, were expressed both in vivo and in vitro. Smo and Gli1 both decreased with the increase of differentiation in vitro. Smo antagonist, cyclopamine, reduced cell numbers, and the expression of Ki67 in MGECM, and promoted the expression of SREBP1 and lipid production in DM + AZM. Smo agonist, SAG, inhibited the expression of SREBP1 and lipid accumulation in DM + AZM but showed no significant effects on raising cell numbers and the expression of Ki67 in MGECM. Conclusions: The Hedgehog signaling pathway appears to play important roles in RMGECs proliferation and differentiation. This may provide a potential therapeutic way to treat meibomian gland dysfunction (MGD).

Meibomian Gland Dysfunction: What Have Animal Models Taught Us?

Studies have estimated that currently 344 million people worldwide and 16.4 million adults in the US have some form of dry eye disease (DED). It is believed that approximately 70% of DED cases are due to some form of evaporative dry eye, for which Meibomian gland dysfunction (MGD) is the major cause. Unfortunately, currently there is no effective treatment for MGD, and solely palliative care is available. Given the importance of MGD in DED, there has been a growing interest in studying Meibomian gland development, homeostasis and pathology, and, also, in developing therapies for treating and/or preventing MGD. For such, animal models have shown to be a vital tool. Much of what is known today about the Meibomian gland and MGD was learnt from these important animal models. In particular, canine and rabbit models have been essential for studying the physiopathology and progression of DED, and the mouse model, which includes different knockout strains, has enabled the identification of specific pathways potentially involved in MGD. Herein, we provide a bibliographic review on the various animal models that have been used to study Meibomian gland development, Meibomian gland homeostasis and MGD, primarily focusing on publications between 2000 and 2020.

Shared gene signature between pterygium and meibomian gland dysfunction uncovered through gene-expression meta-analysis.

BACKGROUND: Pterygium and meibomian gland dysfunction (MGD) are two clinically correlated ocular diseases. We propose to investigate the shared gene signature between pterygium and MGD. METHODS: Microarray datasets were retrieved from the Gene Expression Omnibus (GEO) database. Initial processing of the data was performed using the R programming package. Gene-expression values were log2 transformed and normalized by quantile normalization. The differentially expressed genes (DEGs) in each individual dataset were analyzed by the limma package. The integration of different pterygium datasets and gene-expression meta-analysis was conducted by the NetworkAnalyst package. A Venn diagram was created to find the overlapped DEGs between MGD and pterygium datasets. Gene ontology enrichment and pathway analysis were performed using the ToppGene Suite. RESULTS: We found 193 DEGs significantly up-regulated in pterygium, with the combined effect sizes ranging from 1.53 to 3.78. A gene signature consisting of 11 DEGs were found to be shared by pterygium and MGD (SPRR3, SERPINB13, NMU, KRT10, IL37, KRT6B, PI3, S100A2, MAL, AURKA, and RGCC), and bioinformatics analyses showed that these overlapped DEGs were significantly enriched in pathways related to keratinization, cell-cycle regulation, and formation of the cornified envelope. CONCLUSION: We identified a shared gene signature between pterygium and MGD through gene-expression meta-analysis. The analysis of this signature underlined that keratinization-related pathways may play important roles in the development of these two clinically correlated pathologies.

On the pivotal role of Elovl3/ELOVL3 in meibogenesis and ocular physiology of mice.

The purpose of this study was to examine the role of Elovl3 gene in meibogenesis and the impact of ELOVL3 protein ablation on the physiology of the mouse ocular surface and Meibomian glands (MGs). Elovl3 knockout, ELOVL3-ablated (E3hom) mice and their wild type littermates (E3wt) were studied side by side. E3hom mice had abnormal ocular phenotypes such as delayed eye opening, weeping eyes, crusty eyelids, eyelid edema, highly vascularized cornea and tarsal plates (TPs), slit eye, and increased tearing that resemble symptoms observed in human subjects with various forms of dry eye, MG dysfunction and blepharitis. Lipid profiling of E3hom TPs was conducted using chromatography and mass spectrometry. The analyses revealed that the lipid composition of E3hom TPs was strikingly different from that of their E3wt littermates. The mutation affected major classes of meibomian lipids - cholesteryl esters, wax esters, and cholesteryl esters of (O)-acylated w-hydroxy fatty acids. The studies illuminated the central role of ELOVL3 in producing C21:0-C29:0 fatty acids, including odd-chain and branched ones. Ablation of ELOVL3 leads to selective changes in the lipid composition of meibum, making E3hom mice instrumental in studying the mechanisms of the biosynthesis of meibum and modeling various pathologies of human ocular surface and adnexa.-Butovich, I. A., Wilkerson, A., Bhat, N., McMahon, A., Yuksel, S. On the pivotal role of Elovl3/ELOVL3 in meibogenesis and ocular physiology of mice.

Prediction of potential drugs and targets based on meibomian gland dysfunction module classification to guide individualized treatment.

Meibomian gland dysfunction (MGD) is an epidemic chronic ocular inflammation. However, little is known about its effective treatment. Here, this study identified important MGD-related genes, core regulators, and potential drugs and their targets though integrating a series of bioinformational analyses. First, there were 665 differentially expression genes (DEGs) were identified. Then, 56 coexpression modules were exacted based on the expression of DEGs and their interactors. Moreover, core transcription factors (TF) significantly regulated modules were identified, including RELA, HIF1A, SIRT1, and MYC, which related to variety of eye diseases. Finally, the prediction of potential drugs and the identification of their target were performed. The results showed that artenimol, copper, and glutathione may have the remarkable curative effect or the toxicology to MGD. Moreover, their targets module gene LDHA (lactate dehydrogenase A), ENO1 (enolase 1), ALB (albumin), and PKM (pyruvate kinase M) are play important role in eye diseases. It suggests that these potential drugs may be useful for the treatment of MGD by acting on their targets. It provides valuable references for drug redirection and new drug development for drug developers, and provides individualized treatment strategies for tarsal gland dysfunction.