title: The combined effect of azithromycin and insulin-like growth factor-1 on cultured human meibomian gland epithelial cells.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Our results support our hypothesis, and this combination regime may represent a unique and effective treatment of MGD.
authors.affiliation: Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Ding
mesh_terms: D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004359:Drug Therapy, Combination; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D050356:Lipid Metabolism / Q000187:drug effects; D008247:Lysosomes / Q000378:metabolism; D008537:Meibomian Glands / Q000166:cytology*
chemical_list: D000900:Anti-Bacterial Agents; D007334:Insulin-Like Growth Factor I; D017963:Azithromycin
keywords: IGF-1; azithromycin; meibomian gland