The combined effect of azithromycin and insulin-like growth factor-1 on cultured human meibomian gland epithelial cells.

Abstract

Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease, a prevalent disorder severely affecting patients' quality of life but has no cure. We have discovered that azithromycin, a topical antibiotic used off-label to treat MGD-associated posterior blepharitis, directly acts on the human meibomian gland epithelial cells (HMGECs) to promote their differentiation, and in doing so, reduces cell proliferation. We have also found that insulin-like growth factor-1 (IGF-1), a drug approved by the Food and Drug Administration primarily used to treat dwarfism, stimulates the proliferation and lipid accumulation in these cells. We hypothesize that the combination of azithromycin and IGF-1 will promote cellular differentiation and lipid accumulation, while preserving the normal proliferation of HMGECs. We cultured immortalized HMGECs with vehicle, 10 nM IGF-1, 10 μg/mL azithromycin, or a combination of IGF-1 and azithromycin for 5 to 13 days. Cells were evaluated for intracellular neutral lipids and lysosome accumulation by different staining methods; lipid composition of cell lysates were analyzed using high-performance thin-layer chromatography; proteins of interest (sterol regulatory element binding protein-1 [SREBP-1], cyclins B1 and D1) were measured by immunoblotting, and cell numbers were counted using a hemocytometer. Our findings demonstrate that the combination of azithromycin and IGF-1 promotes the differentiation and lipid accumulation of HMGECs, while preserving their normal proliferation rate. This combined treatment also increased the levels of neutral lipids, phospholipids, and SREBP-1, and restored cyclin B1 content to control amounts. Our results support our hypothesis, and this combination regime may represent a unique and effective treatment of MGD.