Multimodal Highlighting of Structural Abnormalities in Diabetic Rat and Human Corneas.
OBJECTIVE
This study aimed to highlight structural corneal changes in a model of type 2 diabetes, using in vivo corneal confocal microscopy (CCM). The abnormalities were also characterized by transmission electron microscopy (TEM) and second harmonic generation (SHG) microscopy in rat and human corneas.


METHODS
Goto-Kakizaki (GK) rats were observed at age 12 weeks (n= 3) and 1 year (n= 6), and compared to age-matched controls. After in vivo CCM examination, TEM and SHG microscopy were used to characterize the ultrastructure and the three-dimensional organization of the abnormalities. Human corneas from diabetic (n= 3) and nondiabetic (n= 3) patients were also included in the study.


RESULTS
In the basal epithelium of GK rats, CCM revealed focal hyper-reflective areas, and histology showed proliferative cells with irregular basement membrane. In the anterior stroma, extracellular matrix modifications were detected by CCM and confirmed in histology. In the Descemet's membrane periphery of all the diabetic corneas, hyper-reflective deposits were highlighted using CCM and characterized as long-spacing collagen fibrils by TEM. SHG microscopy revealed these deposits with high contrast, allowing specific detection in diabetic human and rat corneas without preparation and characterization of their three-dimensional organization.


CONCLUSIONS
Pathologic findings were observed early in the development of diabetes in GK rats. Similar abnormalities have been found in corneas from diabetic patients.


CONCLUSIONS
This multidisciplinary study highlights diabetes-induced corneal abnormalities in an animal model, but also in diabetic donors. This could constitute a potential early marker for diagnosis of hyperglycemia-induced tissue changes.
Laboratory of Applied Optics, ENSTA ParisTech - École Polytechnique - CNRS, chemin de la Hunière, Palaiseau cedex, France ; INSERM UMRS 872, Team17, Physiopathology of ocular diseases, therapeutic innovations, 15 rue de l'école de médecine, Paris, France ; Pierre et Marie Curie University, Centre de Recherches des Cordeliers, 15 rue de l'école de médecine, Paris, France ; Sorbonne Paris Cité, Paris Descartes University, AP-HP Hôtel-Dieu Hospital, Department of Ophthalmology, 1 place du Parvis Notre-Dame, Paris, France.
Laura
L
Kowalczuk
Gaël
G
Latour
Jean-Louis
JL
Bourges
Michèle
M
Savoldelli
Jean-Claude
JC
Jeanny
Karsten
K
Plamann
Marie-Claire
MC
Schanne-Klein
Francine
F
Behar-Cohen
confocal microscopy; corneas; diabetes; electron microscopy; multiphoton microscopy