EXPRESSION OF MACROPHAGE-MIGRATION INHIBITORY FACTOR IN CORNEAL WOUND-HEALING IN RATS

Purpose. The study was conducted to evaluate the expression of macroph age migration inhibitory factor (MIF) during penetrating corneal injur y. Method. A penetrating linear incision (2 mm) was made in the center of the right cornea with a razor blade. The expression of MIF in the lacerated eye and in the contralateral eye was examined by immunohisto chemistry at 3, 6, 24, 48, and 72 hours after injury. Concentrations o f MIF in the aqueous humor of the injured and contralateral eyes were also measured by enzyme-linked immunosorbent assay. The expression of MIF messenger RNA (mRNA) in the injured cornea was quantified by rever se transcription-polymerase chain reaction and subsequent Southern blo t analysis. Results. Positive migration inhibitory factor staining was observed in the basal cells of epithelial and endothelial cells of th e normal rat cornea. The positive staining of the central corneal epit helium diminished at 3 hours after injury. At 6 hours after injury, po sitive MIF staining reappeared on the basal cells of the injured area, whereas the staining of the contralateral eye remained unchanged. Enz yme-linked immunosorbent assay of the aqueous humor revealed that the MIF concentration was elevated in both the injured and the contralater al eyes. The maximum concentration of aqueous MIF was observed at 6 ho urs after injury in both eyes. Reverse transcription-polymerase chain reaction and Southern blot analysis revealed that MIF-mRNA expression in the injured cornea increased from 6 to 48 hours after injury. Concl usion. The results of immunohistochemistry suggest the possibility tha t MIF is released from the corneal epithelial cells of the injured eye within 3 hours. Conversely, the MIF-mRNA level of the injured cornea is increased from 6 to 48 hours after injury and then diminished. In a ddition, unilateral corneal injury induces bilateral upregulation of M IF in the aqueous humor.