Abstract
Abstract: :
Purpose: We have discovered that 17ß–estradiol stimulates the expression of proinflammatory cytokine and matrix metalloproteinase genes in SV40 immortalized human corneal epithelial cells. However, a major question is whether these findings are physiologically relevant, or possibly an artifact of immortalization or cell culture. Our recent preliminary data indicated that the immortalized cells contain predominantly estrogen receptor (ER) ß, whereas corneal epithelial cells in vivo express primarily ERα. This variation in receptor expression may be very important, given that these receptor subtypes often mediate different effects. The purpose of this study was to determine whether the culture and/or immortalization of corneal epithelial cells does alter the relative expression of estrogen, as well as androgen (AR) and progestin (PR) receptors. Methods: Human corneoscleral rims were obtained from male and female donors for epithelial cell isolation and/or for the culture of explants or isolated epithelial cells. Primary cells, as well as SV40 (gift from Santen Pharmaceutical, Japan) and 'telomerase' (Gipson et al., IOVS 2003; 44: 2496–2506) immmortalized corneal cell lines, were maintained in keratinocyte serum free media in the presence or absence of phenol red. Cellular samples were processed for the purification of total RNA and the analysis of ERα, ERß, AR and PR mRNAs by real time PCR. Results: Our results show that the relative expression of sex steroid receptor mRNAs in human male and female corneal epithelial cells is typically AR > ERα > ER ß > PR. The pattern for ER is analogous to that observed in primary and 'telomerase' corneal epithelial cell cultures. In contrast, the SV40 immortalized cells showed a different profile, with ERß predominating over ERα. Of particular interest, the relative amount of ER mRNA in primary cultured cells was approximately 25–fold less than that present in corneal cells in vivo. In addition, the inclusion of phenol red in culture media appeared to increase the ERα/ER ß ratio about 2–fold in primary cells. Conclusions: Culture and immortalization of human corneal epithelial cells appears to influence the level, and sometimes the ratio, of ERα and ERß. These alterations in vitro may impact the nature of estrogen action on these cells.
Keywords: cornea: epithelium • cornea: tears/tear film/dry eye • cornea: basic science