Abstract
Purpose::
The healing of corneal epithelial wounds is often delayed in individuals with diabetes mellitus. This study sought to investigate whether and how high glucose impairs cell function during corneal epithelial wound healing.
Methods::
SV40-immortalized human corneal epithelial (THCE) cells were cultured in Defined Keratinocyte Serum Free Medium containing normal D-glucose (NG, 5 mM), high D-glucose (HG, 25 mM) and high D-mannitol (HM, 20 mM). Effects of high glucose on cell adhesion to different extracellular matrix proteins and on cell migration were determine by in vitro cell adhesion and by scratch wound assay, respectively. The glucose induced changes in focal adhesion kinase (FAK), mitogen-activated protein (MAP) kinases, and NF-ΚB were analyzed by Western blotting. Cell proliferation was determined by counting cells at each passage using Cell Counter and cell apoptosis was evaluated by TUNEL staining.
Results::
HG increased THCE cell adhesion to collagen IV, but not fibronectin and laminin V, and impaired cell migration during epithelial wound closure in vitro. Exposure of the cells to HG induced tyrosine phosphorylation of extracellular signal regulated kinase (ERK), JNK, p38 of the MAP kinases as well as NF-ΚB activation whereas the tyrosine phosphorylation of FAK (tyr397) was inhibited. Cell proliferation in cells cultured in HG for 5 passages was significantly attenuated as compared to cells in NG and in HM. Chronic (24 or 48 hours) as well as short exposure of the cells to HG resulted in an increase in cell apoptosis.
Conclusions::
HG have adverse effects on cell signaling in response to wounding and cause an increase in cell adhesion to collagen IV and apoptosis and a decrease in cell proliferation and migration. These alterations may account for impaired corneal epithelial wound healing in diabetic keratopathy.
Keywords: cornea: epithelium • diabetes • wound healing