Posterior stromal cell apoptosis triggered by mechanical endothelial injury and basement membrane component nidogen-1 production in the cornea

Abstract

This study was performed to determine whether cells in the posterior stroma undergo apoptosis in response to endothelial cell injury and to determine whether basement membrane component nidogen-1 was present in the cornea. New Zealand White rabbits had an olive tip cannula inserted into the anterior chamber to mechanically injure corneal endothelial cells over an 8 mm diameter area of central cornea with minimal injury to Descemet's membrane. At 1 h (6 rabbits) and 4 h (6 rabbits) after injury, three corneas at each time point were cryopreserved in OCT for terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunohistochemistry (IHC) for vimentin and nidogen-1, and three corneas at each time point were fixed for transmission electron microscopy (TEM). Uninjured corneas were controls. Stromal cells over approximately the posterior 25% of the stroma overlying to the site of corneal endothelial injury underwent apoptosis detected by the TUNEL assay. Many of these apoptotic cells were vimentin+, suggesting they were likely keratocytes or corneal fibroblasts. Stromal cells peripheral to the site of endothelial injury and more anterior stromal cells overlying the site of endothelial injury did not undergo apoptosis. Stromal cell death was confirmed to be apoptosis by TEM. No apoptosis of stromal cells was detected in control, uninjured corneas. Nidogen-1 was detected in the stroma of unwounded corneas, with higher nidogen-1 in the posterior stroma than the anterior stroma. After endothelial scrape injury, concentrations of nidogen-1 appeared to be in the extracellular matrix of the posterior stroma and, possibly, within apoptotic bodies of stromal cells. Thus, posterior stromal cells, likely including keratocytes, undergo apoptosis in response to corneal endothelial injury, analogous to anterior keratocytes undergoing apoptosis in response to epithelial injury.

The Corneal Basement Membranes and Stromal Fibrosis

“…Posterior fibrosis does not occur if the endothelium alone is removed over an 8-mm-diameter circle using an olive tip cannula, despite apoptosis of the overlying posterior stromal keratocytes and the ensuing stromal wound healing response. 77 This experiment confirms that Descemet's BM is the critical modulator of posterior corneal fibrosis, as the EBM is for anterior corneal fibrosis. Further study is needed to fully understand the role Descemet's BM plays in the modulation of posterior corneal fibrosis that occurs after corneal infections, diseases, trauma, and surgeries.…”

A Rabbit Corneal Endothelial Dysfunction Model Using Endothelial-Mesenchymal Transformed Cells

“…It is worth noting that transplanted Fresh-RCECs contributed to prevent such changes in the corneal stroma. It has also been reported that mechanical corneal endothelial injury in rabbits triggers apoptosis of posterior stromal cells in the short term 41 . Further studies are required elucidate how cell apoptosis and fibroblastic cells affects wound healing in the long term.…”

Assessment of Topical Therapies for Improving the Optical Clarity Following Stromal Wounding in a Novel Ex Vivo Canine Cornea Model

“…In addition, recent evidence suggests that a posterior wound healing response is triggered upon disruption of the corneal endothelium. 90 This could potentially cause fibrosis to form in the posterior stroma, which would confound assessment of anterior stromal haze. In the present study, fibrosis was limited to the anterior-to midstroma in all wounded corneas, based on slit-lamp examination and post hoc immunofluorescent microscopic evaluation.…”