Multimodal Highlighting of Structural Abnormalities in Diabetic Rat and Human Corneas.

PURPOSE: 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. CONCLUSION: Pathologic findings were observed early in the development of diabetes in GK rats. Similar abnormalities have been found in corneas from diabetic patients. TRANSLATIONAL RELEVANCE: 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

Optique non-linéaire et chiralité

Nous étudions les propriétés physiques des molécules chirales en étendant les techniques d'optique non-linéaire aux effets chiroptiques pour ainsi mesurer une “activité optique non-linéaire”. La génération de second harmonique en surface est particulièrement sensible à la chiralité moléculaire, avec des rotations de polarisation du second harmonique et des différences circulaires et linéaires très importantes. Pour comprendre l'origine physique de ces effets chiroptiques, nous généralisons les principaux modèles microscopiques de chiralité aux effets non-linéaires d'ordre deux et montrons qu'une chiralité à un électron n'a pas la même signature à l'ordre deux qu'une chiralité par couplage excitonique. Des expériences avec des molécules test pour ces deux types de chiralité montrent un bon accord avec ces modélisations théoriques