Collagen type XII is undetectable in keratoconus Bowman's layer.

Abstract

PURPOSE:

Corneal biomechanical failure is the hallmark of keratoconus (KC); however, the cause of this failure remains elusive. Collagen type XII (COL12A1), which localises to Bowman's layer (BL), is thought to function in stress-bearing areas, such as BL. Given the putative protective role of COL12A1 in biomechanical stability, this study aims to characterise COL12A1 expression in all corneal layers involved in KC.

METHODS:

TaqMan quantitative PCR was performed on 31 corneal epithelium samples of progressive KC and myopic control eyes. Tissue microarrays were constructed using full-thickness corneas from 61 KC cases during keratoplasty and 18 non-KC autopsy eyes and stained with an antibody specific to COL12A1. Additionally, COL12A1 was knocked out in vitro in immortalised HEK293 cells.

RESULTS:

COL12A1 expression was reduced at transcript levels in KC epithelium compared with controls (ratio: 0.58, p<0.03). Immunohistochemical studies demonstrated that COL12A1 protein expression in BL was undetectable, with reduced expression in KC epithelium, basement membrane and stroma.

CONCLUSIONS:

The apparent absence of COL12A1 in KC BL, together with the functional importance that COL12A1 is thought to have in stress bearing areas, suggests that COL12A1 may play a role in the pathogenesis of KC. Further studies are necessary to investigate the mechanisms that lead to COL12A1 dysregulation in KC.

• Authors: Mohammed Rigi, Hyeck-Soo Son, Loren Moon, Mario Matthaei, Divya Srikumaran, Albert S Jun, Charles G Eberhart, Uri S Soiberman
• Journal: The British journal of ophthalmology (Br J Ophthalmol) (Feb 06 2023) ISSN: 1468-2079 [Electronic] England
• PMID: 36746614 (Publication Type: Journal Article)
• Copyright: © Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.