Strain Differences in the Branching of the Sciatic Nerve in Rats

Pigment epithelium-derived factor enhances peripheral nerve regeneration through modulating oxidative stress and stem cells: An experimental study

Peripheral nerve injury is common and negatively affects an individual's quality of life. Drugs used for peripheral nerve regeneration should aim to eliminate symptoms such as neuropathic pain and have therapeutic effects. In recent studies, pigment epithelium-derived factor (PEDF) has been considered an essential therapeutic agent because of its potential neuroprotective properties. In this study, we aimed to investigate the efficacy of locally applied PEDF for peripheral nerve regeneration. Twenty-four Wistar albino male rats were used. The study groups included Injury (n = 12) and Injury+PEDF (n = 12). An injury model was created by applying 50 N pressure to the right sciatic nerves in groups, and 10 μg/kg local PEDF was injected into the Injury+PEDF group. After 28 days of recovery, functional tests and stereological, immunohistochemical, and biochemical analyses were performed. A significant difference was found between the Injury and Injury+PEDF groups in amplitude, whereas no difference was found in latency. The number of myelinated axons and the myelinated axon area increased significantly in the Injury+PEDF group, while no statistically significant difference was found in myelin sheath thickness. Superoxide dismutase, catalase, and glutathione peroxidase activities were increased by PEDF, whereas they were suppressed in mesenchymal stem cells. PEDF exerts functional, quantitative, and antioxidative effects on sciatic nerve injury during neuroregeneration. In addition, when oxidative stress parameters were examined, it was seen that PEDF reduced oxidative stress following sciatic nerve injury.

Anatomic variations of brachial and lumbosacral plexus models in different rat strains

PURPOSE

Selection of an appropriate model for preclinical assessment of new methods of peripheral nerve injury management is crucial. This report presents anatomic variations within brachial and lumbosacral plexuses in three selected rat strains Sprague Dawley (Hsd:Sprague Dawley SD), Lewis (LEW/SsNHsd), and Athymic Nude (Hsd:RH-Foxn1^rnu ) rats.

METHODS

Based on their strain eighteen rats were divided into three groups. A total of 90 brachial plexus nerves (axillary, musculocutaneous, median, ulnar, and radial nerves) and 72 lumbosacral plexus nerves (sciatic, tibial, common peroneal, and sural nerves) were analyzed for the length, diameter and correlation with the body weight. A detailed anatomic course of each nerve within the brachial and lumbosacral plexuses was outlined.

RESULTS

The sural nerve was the longest nerve in all studied rat strains, whereas the sciatic nerve had the largest diameter. Comparison of all the nerves' length demonstrated that the Lewis rat sciatic and sural nerves were significantly shorter (P < 0.05). No significant differences in nerve diameters were found among the analyzed rat strain groups. Significant correlation was revealed between the length of sciatic nerve and the rats' weight, which is irrelevant to the rats' genetic background.

CONCLUSIONS

This study confirmed that nerves' length within rat's brachial and lumbosacral plexus depends on the inter-individual variations within the rat strains rather than on the differences in the peripheral nerve development, which is inherent to the specific rat strain. Correlation between the nerve length and body weight, suggests that bigger rats should be considered for studies requiring access to the long nerves. © 2016 Wiley Periodicals, Inc. Microsurgery 37:327-333, 2017.

The sciatic nerve injury model in pre-clinical research

In the pre-clinical view, the study of peripheral nerve repair and regeneration still needs to be carried out in animal models due to the structural complexity of this organ which can be only partly simulated in vitro. The far most used experimental model is based on the injury of the sciatic nerve, the largest nerve trunk in mammals. In this paper, the potential application of the sciatic nerve injury model in pre-clinical research is critically reviewed. This paper is aimed at helping researchers in properly employing this in vivo model for the study of nerve repair and regeneration as well as interpreting the results in a clinical translation perspective.

A novel internal fixator device for peripheral nerve regeneration

Recovery from peripheral nerve damage, especially for a transected nerve, is rarely complete, resulting in impaired motor function, sensory loss, and chronic pain with inappropriate autonomic responses that seriously impair quality of life. In consequence, strategies for enhancing peripheral nerve repair are of high clinical importance. Tension is a key determinant of neuronal growth and function. In vitro and in vivo experiments have shown that moderate levels of imposed tension (strain) can encourage axonal outgrowth; however, few strategies of peripheral nerve repair emphasize the mechanical environment of the injured nerve. Toward the development of more effective nerve regeneration strategies, we demonstrate the design, fabrication, and implementation of a novel, modular nerve-lengthening device, which allows the imposition of moderate tensile loads in parallel with existing scaffold-based tissue engineering strategies for nerve repair. This concept would enable nerve regeneration in two superposed regimes of nerve extension--traditional extension through axonal outgrowth into a scaffold and extension in intact regions of the proximal nerve, such as that occurring during growth or limb-lengthening. Self-sizing silicone nerve cuffs were fabricated to grip nerve stumps without slippage, and nerves were deformed by actuating a telescoping internal fixator. Poly(lactic co-glycolic) acid (PLGA) constructs mounted on the telescoping rods were apposed to the nerve stumps to guide axonal outgrowth. Neuronal cells were exposed to PLGA using direct contact and extract methods, and they exhibited no signs of cytotoxic effects in terms of cell morphology and viability. We confirmed the feasibility of implanting and actuating our device within a sciatic nerve gap and observed axonal outgrowth following device implantation. The successful fabrication and implementation of our device provides a novel method for examining mechanical influences on nerve regeneration.

Electrophysiologic assessment of sciatic nerve regeneration in the rat: Surrounding limb muscles feature strongly in recordings from the gastrocnemius muscle

Striking inconsistencies between the results of morphometric and electrophysiologic examinations of the regenerating nerve were observed in a previous study featuring the bridging of a 14 mm gap in the rat sciatic nerve. To shed light on this dichotomy, seven further rats were subjected to permanent sciatic nerve transection and assessed electrophysiologically, histologically and by retrograde axonal tracing at various postoperative intervals (1 h to 8 weeks). The results of the histological examinations and retrograde tracing revealed that in spite of the fact that compound muscle action potentials could be recorded in the gastrocnemius muscle, no reinnervation of the gastrocnemius muscle, either physiological or aberrant, had actually taken place. Furthermore, it was established that the electrical activity recorded in the gastrocnemius muscle after stimulation of the proximal or distal stump is generated by surrounding hind limb muscles unaffected by denervation. These are stimulated either directly, or indirectly due to spreading of the impulse. It is therefore strongly recommended that caution should be exercised when interpreting recordings from the gastrocnemius muscle after stimulation of a regenerating sciatic nerve in laboratory rodents.