Abstract
Purpose: :
To elucidate the role(s) of collagens XII and XIV in the regulation of corneal endothelial structure and function at different ages using wild type, Col12a1-/-,Col14a1-/- and double knockout Col 12a1/Col14a1 mice.
Methods: :
Corneal thickness and endothelial morphology were studied using in vivo laser confocal microscopy (HRT Rostock Cornea Module, Heidelberg Engineering) at ages P10 and P30. Transmission electron microscopy (TEM) examination of the posterior stroma, Descemet’s membrane and endothelium was done at ages P4, P14 and P30. Scanning electron microscopy (SEM) on corneal flat mounts with the endothelial side face-up was also performed. Collagen XII and XIV expression was analyzed using immuno-chemical methods at P4 to P30.
Results: :
Transmission electron microscopy clearly showed large intracellular "vacuoles" like structures in the endothelial cells of all mice strains including wild type at age P4. These structures decreased in number in wild type and Col12a1-/- mice at age P14. No significant changes in the size or number of these vacuoles like structures was noted in Col14a1-/- or double knockout Col 12a1/Col14a1. At age P30, wild type and Col12a1-/- mice showed compact endothelial cells with no intracellular vacuoles. In contrast, Col14a1-/- and double knockout Col 12a1/Col14a1 continued to have intracellular "vacuoles" like structures. These findings were confirmed by both, in vivo laser confocal microscopy and SEM, that showed the presence of these vacuoles only in the Col14a1-/- mice corneas at P30. SEM of endothelial flat mounts showed normal hexagonal morphology in Col12a1-/- and wild type mice.
Conclusions: :
Col14a1-/- and double knockout Col 12a1/Col14a1 mice present significant morphological changes in the corneal endothelium. The structural alterations suggest functional changes. However, studies are needed to better understand the molecular mechanisms responsible for these changes and their functional implications.
Keywords: extracellular matrix • cornea: basic science