Laser doppler perfusion imaging of skin territory to reflect autonomic functional recovery following sciatic nerve autografting repair in rats

Abstract

Peripheral nerve repair requires comprehensive evaluation of functional outcomes of nerve regeneration; however, autonomic nerve function is seldom evaluated probably due to lack of suitable quantitative methods. This study sought to determine whether autonomic functional recovery could be reflected by cold-induced vasodilation (CIVD) within target skin territory, as monitored by laser Doppler perfusion imaging (LDPI). Rats with sciatic nerve defect injury received autologous nerve grafting, and the plantar surface of the hind feet was subjected to LDPI analysis following nerve repair. The results indicated that at 3 and 6 months after autologous nerve grafting, the plantar surface of the hind foot exhibited the same level of CIVD as contralateral normal side, whereas rats in nerve defect group (negative control) showed significantly reduced CIVD. In addition, suitable nerve regeneration and functional recovery were achieved as assessed by pain sensation tests as well as electrophysiological and immunohistological examinations. Based on the potential influence of local autonomic nerve signals on CIVD, it was possible to evaluate functional recovery of autonomic nerves by using LDPI measurements of dermal CIVD.

The role of C-afferents in mediating neurogenic vasodilatation in plantar skin after acute sciatic nerve injury in rats

“…In the present study, the refinement and reduction of research animals were enforced by using minimal numbers of rats for each experiment, involving experienced and proficient experimenters in rodent surgery, and employing blind approach in data collection. A limitation of the present study is that the vascular physiology of rats may be different to some extent from that in humans, as indicated in our previous studies [7,9]. However, as rodents are the most widely used models in studying neuro-vascular control mechanisms, the findings in the present study have implications in understanding the pathophysiological sequela of peripheral nerve injuries in humans and the development of novel assessment of nerve regeneration in experimental settings [44].…”

“…Vasomotor activities of dermal vasculature in response to local thermal challenges mainly involve neural control mechanisms, including both sympathetic and sensory nerve fibers [1,6]. In previous studies, we found that both baseline blood perfusion and local thermal challengesinduced perfusion change in the skin were altered after peripheral nerve injury [7][8][9]. In rats, transection injury to the sciatic nerve or tibial nerve promptly resulted in a substantial increase in blood perfusion by several fold in ipsilateral plantar skin [8,9], whereas chronically denervated plantar skin did not exhibit a significant difference in blood perfusion as compared to the contralateral normal side [9].…”

“…In previous studies, we found that both baseline blood perfusion and local thermal challengesinduced perfusion change in the skin were altered after peripheral nerve injury [7][8][9]. In rats, transection injury to the sciatic nerve or tibial nerve promptly resulted in a substantial increase in blood perfusion by several fold in ipsilateral plantar skin [8,9], whereas chronically denervated plantar skin did not exhibit a significant difference in blood perfusion as compared to the contralateral normal side [9]. It remains elusive whether sympathetic nerve fibers or sensory ones or both are responsible for neurogenic vasodilatation following nerve injury.…”

A New Computerized Morphometric Analysis for Peripheral Nerve Study

“…16,17 Another quantification approach involves immunostaining nerve cross sections for neurofilament-200 and viewing with fluorescent microscopy. 18 These diverse methods have been performed successfully and with satisfactory results, but there are disadvantages that exist for each. While random sampling of a nerve cross section can be done relatively inexpensively, the method is time-consuming and the risk of bias still exists.…”

“…Slides were then prepared as follows: the specimens were directly immersed into a 2.5% glutaraldehyde/phosphate-buffered saline. They were then processed routinely and embedded in a mixture (Ted Pella Inc., Redding, CA) consisting of 76.0 g Medcast, 18.0 g Araldite 502, 39.0 g dodecenyl succinic anhydride (DDSA), 61.0 g nadic methyl anhydride (NMA), and 2.0 to 3.5% 2,4,6-tri (dimethyl aminomethyl) phenol-30 (DMP-30) by volume. Semithin 0.5 µm transverse sections were cut and stained with toluidine blue.…”