Histological Findings in the Eyes of Abcc6 Knockout Rat Model of Pseudoxanthoma Elasticum.

PURPOSE: To describe the ocular findings of murine pseudoxanthoma elasticum (PXE) models with ATP-binding cassette subfamily C member 6 (Abcc6) gene knockout.

METHODS

This experiment was conducted in four Abcc6-/- rats and compared with six wild-type Abcc6+/+ control rats. The animals underwent necropsy at 6 months of age. Histological examination of the eyes was performed.

RESULTS

Histological examination of eight eyes from four Abcc6-/- rats revealed multiple nodular foci of calcification in the uvea, sclera, and conjunctiva, focally in perivascular distribution, as well as linear and nodular calcification of Bruch's membrane. Calcific foci were not associated with inflammation in the knockout rats. There was no evidence of calcification in control eyes.

DISCUSSION: The Abcc6-/- rat model shows that PXE can affect multiple ocular tissues beyond the calcification in Bruch's membrane noted in human eyes. Nodular calcific foci probably correspond to comet lesions seen in patients with PXE. The presence of ectopic calcium without inflammation distinguishes it from inflammatory calcium deposition in atherosclerosis. Further studies are needed to determine why PXE does not cause inflammatory infiltration.

TRANSLATIONAL RELEVANCE: The Abcc6-/- murine model may be suitable for studying ocular PXE pathophysiology and ectopic calcification and developing effective therapies.