Descemet’s basement membrane modulation of corneal fibrosis

Abstract

Purpose : To evaluate the effect of removal of Descemet’s basement membrane and endothelium (DBME) compared to removal of the endothelium alone on posterior corneal fibrosis.

Methods : Six NZW rabbits had removal of the 8 mm of central DBME. Six rabbits had 8 mm endothelial removal with an olive-tipped cannula. All corneas developed stromal edema. Corneas in both groups were excised at one month after injury and cryofixed in OCT. Corneal sections had immunohistochemistry (IHC) for alpha-smooth muscle actin (SMA), keratocan, CD45, nidogen-1, vimentin and Ki-67. Sections from each cornea were also analyzed with the TUNEL assay.

Results : Six of 6 corneas that had DBME removal developed posterior stromal fibrosis populated with SMA+ myofibroblasts whereas 0 of 6 corneas that had endothelium removal alone developed fibrosis or SMA+ myofibroblasts (p<0.01). Myofibroblasts in the fibrotic zone of corneas that had DBME removal were undergoing both mitosis and apoptosis. A zone between keratocan+ keratocytes and SMA+ myofibroblasts contained keratocan- SMA- vimentin+ cells that were likely CD45- corneal fibroblasts and CD45+ fibrocytes.

Conclusions : Descemet’s basement membrane has an important role in modulating posterior corneal fibrosis after injury that is analogous to the role of the epithelial basement membrane in modulating anterior corneal fibrosis after injury. This role is likely mediated by BM components like perlecan and nidogens in Descemet's membrane that regulate the entry of aqueous humor TGF-beta into the corneal stroma to drive the development of myofibroblasts from both fibrocytes and keratocytes/corneal fibroblasts. Fibrotic areas had myofibroblasts undergoing mitosis and apoptosis, indicating that the fibrosis following injury is in dynamic flux.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Duplex IHC for keratocan (green) and SMA (red) was performed in panels A and B. A. Keratocan was localized within keratocytes (arrowheads), and the surrounding corneal stroma, in an unwounded control cornea. Arrows indicate endothelium. e is epithelium. Blue is DAPI. No SMA+ cells were detected in normal unwounded corneas. B. At 4 weeks after DBME removal over the central 8mm of the cornea, there was a zone of fibrosis (f) that occupied the posterior corneal stroma populated with SMA+ (red) myofibroblasts. The anterior stroma (k) in this cornea was occupied by keratocan+ keratocytes. Corneas that had endothelial cell removal alone were similar to A after 4 weeks (not shown). Mag 100X.