Abstract
Purpose :
Impairment of small nerve fibers is considered the earliest alteration in diabetic neuropathy, which needs an objective and non-invasive biomarker for its detection. Cornea contains small nerve fibers and their alterations can be monitored with non-invasive in vivo microscopy, which may help to identify early peripheral nerve status of diabetic patients. Hyperglycemia can activate RhoA and spinal Deleted in liver cancer 2 (DLC2)/RhoA pathway was involved in inflammatory and neuropathic pain; but few studies focused on cornea. We aimed to non-invasively investigate corneal nerve injury and its association with intraepidermal nerve changes upon hyperglycemia and explore underlying pathogenesis.
Methods :
Methods: Hyperglycemia was induced in DLC2-/- and DLC2+/+ mice (N=6) expressing neural YFP by streptozotocin. At different times, body weight, blood glucose level and corneal sensitivity were measured while corneal nerves were visualized with in vivo confocal microscopy. Corneal and intraepidermal nerve analysis were performed on corneal flat mount and leg skin, using Imaris and Image J software.
Results :
There were no age-related changes in blood glucose level, corneal sensitivity and corneal nerve parameters in DLC2-/- and DLC2+/+ mice. Hyperglycemia resulted in reduction of corneal nerve fiber length(CNFL), corneal nerve fiber density(CNFD) and corneal nerve branch density. Central cornea of hyperglycemic DLC2+/+ mice started to show significant loss (26.7±6.1%) in CNFD at 20 weeks old, which commenced at 24 weeks old in peripheral cornea (33.4±7.7%). CNFL also significantly decreased while corneal nerve tortuosity increased on whole cornea. More importantly, these pathological structural changes occurred earlier than corneal functional loss and intraepidermal nerve changes. Compared with DLC2+/+ mice, hyperglycemic DLC2-/- mice displayed more severe corneal nerve damage at an earlier time (16 weeks old) (25.0±7.8%), indicating that deficiency of DLC2 exacerbated hyperglycemia-induced corneal nerve damage.
Conclusions :
Corneal nerve damage occurred earlier than intraepidermal nerves upon hyperglycemia, suggesting that monitoring of corneal nerve fiber may help in early diagnosis of diabetic neuropathy. DLC2/RhoA may play a role in diabetic corneal nerve injury and may serve as a potential therapeutic target in treatment of diabetic corneal neuropathy.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.