Abstract
Purpose: :
Growth factors play a critical role in the proliferation and differentiation of sebaceous gland epithelial cells. Given that the meibomian gland is a large sebaceous gland, we hypothesize that growth factors exert analogous effects on human meibomian gland epithelial cells. We sought to test this hypothesis in the present study.
Methods: :
Human meibomian gland epithelial cells were immortalized with a retrovirus containing telomerase reverse transcriptase. Cells (3 wells/condition/experiment) were cultured for varying time intervals in MCDB 153 or keratinocyte serum-free basal media (SFM) in the presence or absence of epidermal growth factor (EGF; 5 ng/ml) and bovine pituitary extract (BPE; 50 µg/ml). Proliferating cells were enumerated by measuring the incorporation of 5-bromo-2-deoxyuridine into DNA. Total cells were also counted. Cell differentiation was assessed with Oil red O, a dye that stains neutral lipids and accumulates in sebaceous gland epithelial cells during maturation.
Results: :
Our findings demonstrate that growth factors have a significant, time-dependent impact on the proliferation of human meibomian gland epithelial cells. For example, in passage 50 cells plated at 20-30% confluence, cell proliferation rates increased most rapidly following exposure to combined EGF+BPE treatment, and least with EGF alone. After 5 days of culture, total cell counts increased 3.3-, 12.8-, and 18.2-fold in EGF, BPE, and EGF+BPE containing SFM media, respectively. For comparison, the MCDB 153 medium and SFM alone supported minimal to no cell proliferation. The extent of the growth factor and media influence on proliferation was dependent upon the cell seeding density and the cell passage number. Administration of EGF+BPE to cells cultured at 70-80% confluence appeared to promote differentiation. However, this cellular maturation, which was similar to that achieved with 1.2 mM calcium or 10% FBS exposure, may have been due to cells reaching confluence.
Conclusions: :
Our results support our hypothesis that growth factors stimulate the proliferation, and possibly differentiation, of human meibomian gland epithelial cells.
Keywords: cornea: tears/tear film/dry eye • cell survival • eyelid