Abstract
Purpose :
Direct intercellular contacts between stromal and epithelial cells are involved in a number of functions critical to the development and repair of the cornea. We recently identified a crucial role for the carbohydrate-binding protein galectin-3 in promoting matrix metalloproteinase 9 (MMP9) in epithelial cells through its interaction with the cell surface receptor CD147. The goal of this study was to determine whether the interaction of fibroblasts with epithelial cells regulates the expression and function of galectin-3.
Methods :
Primary human corneal fibroblasts and immortalized human corneal-limbal epithelial cells were maintained in DMEM medium supplemented with 10% serum and keratinocyte serum-free medium, respectively. The presence of galectin-3 and CD147 in whole cell lysates was quantified by Western blot. Affinity chromatography was performed using a sepharose-conjugated galectin-3 column. MMP9 secretion was determined by gel zymography.
Results :
Both fibroblasts and epithelial cells produced galectin-3. Epithelial cells expressed the highly glycosylated forms of CD147, known to induce MMP production, whereas fibroblasts expressed glycoforms of lower molecular weight. CD147 from epithelial and fibroblast origin bound to galectin-3 in a galactose-dependent manner, however, exogenous galectin-3 failed to induce MMPs in fibroblasts, in contrast to epithelial cells. Co-culture of fibroblasts with epithelial cells resulted in an upregulation of galectin-3, concomitant with an enhanced expression of CD147 and MMP9. The increase in MMP9 was time-dependent, reaching its maximum at 24-48 h, and was directly related to the number of fibroblasts in culture.
Conclusions :
Our results indicate that galectin-3 expression is dependent on the interaction between epithelial and stromal cells, and suggest that sustained upregulation of galectin-3 may potentially lead to stromal matrix degradation and therefore may be clinically relevant to corneal disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.