Topische Dexamethason-Therapie

Zusammenfassung

Untersuchungsziel. Ermittlung der Wirkung von Dexamethason auf antigenpräsentierende Zellen (APCs) der Hornhaut und deren Einfluss auf die Überlebenszeit MHC-differenter Hornhauttransplantate der Maus.

Methoden. Mittels EDTA präparierte epitheliale Flatmounts und tangentiale Gefrierschnitte des Hornhautstromas von unbehandelten und 7 Tage mit Dexamethason Augentropfen vorbehandelten BALB/c Mäusen (n=6) wurden immunhistologisch auf F4/80+- und MHC II+-Zellen untersucht. Weiterhin wurden an unbehandelten und entsprechend vorbehandelten Mäusen (n=8) allogene (C3H) Keratoplastiken durchgeführt.

Ergebnisse. Im Hornhautepithel, nicht aber im Hornhautstroma reduzierte Dexamethason drastisch die F4/80+- und die MHC II+-Zellen (p<0,01). Die Transplantate der unbehandelten Tiere überlebten 16±4 Tage, die der Dexamethason-vorbehandelten 16±3 Tage.

Abstract

Objective. To determine the influence of dexamethasone treatment on APCs and the time of graft survival of MHC-disparate grafts.

Methods. Flatmounts of the ocular surface prepared with EDTA and tangential frozen sections of the remaining corneal stroma from untreated eyes of normal mice (n=6) and from eyes treated for 7 days with dexamethasone (n=6) were immunohistologically examined for content of F4/80+ and MHC II+ cells.Furthermore, corneas of C₃H mice without and with 7-day dexamethasone eye drop treatment (n=8) were grafted into BALB/c mice receiving the same treatment.

Results. The number of positive cells within the epithelial flatmounts showed a dramatic reduction in the dexamethasone-pretreated group (p<0.01 compared to the untreated control group).The number of positive cells in the corneal stroma remained unchanged. The grafts of untreated control mice survived 16±4 days, the treated grafts 16±3 days.

Conclusions. Most investigators assume that normal murine corneas contain no APCs such as macrophages and Langerhans cells. For the first time we were able to detect APCs in flatmounts of the ocular surface and frozen sections of corneal stroma.Our investigations show that, in contrast to the ocular surface, the number of F4/80+ cells in the corneal stroma is not influenced by dexamethasone treatment.Transplantation of corneas containing donor-derived APCs promotes acute rejection (direct pathway of allorecognition).Thus,dexamethasone treatment did not prolong the time of allograft survival.