Ophthalmological Monitoring of Diabetic Neuropathy in a Mouse Model

Patients with diabetes mellitus suffer from late damage, including microvascular and macrovascular complications and diabetic polyneuropathy, even though blood glucose is well controlled and the HbA1c value normalised. Peripheral nerves are affected, and when these are damaged, this can result in disturbed sensation and pain. Such nerves are mainly Ad und C fibres, which are present in the skin, but also in the subbasal nerve plexus of the cornea. Imaging of the subbasal nerve plexus usingmicroscopic techniques allows a very early and objective view of neuropathy, which is only possible invasively by skin biopsy. We have used a thy1-YFP mouse strain in which the peripheral nerves are detectable by fluorescence excitation. Using two photon microscopy, we produced high resolution three dimensional images of the corneal subbasal nerve plexus of these mice. We induced diabetes mellitus in thy1-YFP mice by injection of streptocotocin. We showed that the increase in blood glucosewas accompanied by a loss of subbasal nerve fibres, mainly in the centre of the cornea. Subsequent treatment of the animals with insulin normalised blood glucose and was accompanied by an increase in subbasal nerve fibres. Thus, this model is highly suited to investigate the pathogenesis of diabetic polyneuropathy, with the aim of developing new causal strategies to treat the disease.