Raman spectroscopy of human vitreous collagen in diabetic retinopathy

In diabetes nonenzymatic glycation alters collagen throughout the body resulting in the histopathology that underlies diabetic disease in several organs. In the eye such changes in vitreous collagen could contribute to vitreous degeneration and the progression of proliferative diabetic retinopathy. Previous studies have demonstrated early glycation and advanced endproducts in the vitreous of humans with proliferative diabetic retinopathy. Near-infrared Fourier-transform Raman spectroscopy was performed on vitreous obtained at surgery from diabetic patients and from non-diabetic control subjects. The findings were compared to measurements obtained in untreated and glycated (in vitro) rat-tail tendon collagen. The results demonstrated substantial changes in diabetic vitreous collagen resulting from glycation, most likely advanced glycation endproducts. This approach appears to be useful as a means of characterizing the molecular changes induced by diabetes. Furthermore, this technique could be developed as a way of quantifying these changes in vivo in several tissues, so as to gauge the severity of non-enzymatic glycation and monitor the response to therapy.