Collagen fiber changes related to keratoconus with secondary corneal amyloidosis

Abstract

We describe the histological changes in the collagen fibers of a 50-year-old male who presented keratoconus with secondary corneal amyloidosis. Corneal tissue from the patient was obtained following a penetrating keratoplasty and was subjected to histochemical analysis using Masson’s trichrome staining, Congo red staining, anti-lactoferrin antibody, and anti-transforming growth factor-beta-induced protein (TGFBIp) antibody. A Congo red-positive region was detected in the anterior half of the stroma in the center and inferior cornea. Although hemotoxylin and eosin staining revealed irregularity in the Congo red-positive region, other parts of the stroma did not show any abnormalities. Positive staining both by anti-TGFBIp and anti-lactoferrin antibodies was observed in the Congo red-positive region. Interestingly, all the layers of the corneal stroma, including the peripheral region, were positively stained by anti-TFGBIp antibody, even in the Congo red-negative area. Masson’s trichrome staining also showed irregular staining throughout the corneal stroma, even outside of the Congo red-positive region. Additionally, Bowman’s layer, which consists of collagen type IV, was damaged. TGFBIp was strongly expressed and Masson’s trichrome staining was reduced throughout the entire keratoconic stroma. The constant qualitative changes in keratoconic collagen fibers, along with the observed abnormality in the Bowman’s membrane, might point to the pathogenesis of secondary corneal amyloidosis in keratoconus.

Graft rejection-like reactions in the early postoperative period after deep anterior lamellar keratoplasty for keratoconus: a retrospective study

“…However, the host corneal stroma, which contributes to amyloid deposition in KC, may be related to graft rejection, even though the deposition is subclinical. 18 , 19 …”

Comparison of morphological changes of corneal collagen fibers treated with collagen crosslinking agents using second harmonic generation images

“…Corneal collagen is organized in a depth-dependent fashion [27] and collagen fibers always show a regular packaging [27,28]. However, this regular pattern has been shown to change with pathologies [29], including keratoconus [30,31], after surgical procedures [32], and after CXL treatment [4]. Due to this, both classification and quantification of collagen arrangement might be a powerful tool in biomedicine as well as in medical studies.…”