Delayed nerve regeneration in streptozotocin diabetic rats.
Nerve regeneration across a 10-mm gap was delayed in streptozotocin diabetic rats 3 and 4 weeks after transecting the sciatic nerve. Opposite ends of each cut nerve were introduced into a silicone tube, leaving a 10-mm gap. Electron microscopy was used to evaluate the progress of regeneration in sections at 2-mm intervals across the 10-mm gap. After 3 weeks, control axons had bridged the 10-mm gap, and myelin sheaths extended for 6-8 mm. By contrast, axons and their myelin sheaths were seen no further than 2 mm from the proximal stump in diabetic animals. By 4 weeks, axons had bridged the gap in diabetics; however, they appeared immature and showed dystrophic changes. The findings suggest that although regeneration does occur in diabetic nerves, it is significantly delayed and qualitatively impaired.