How can neuroplasticity be utilized to improve neuropathy symptoms?

Morpho-Functional Characterisation of the Rat Ventral Caudal Nerve in a Model of Axonal Peripheral Neuropathy

Peripheral Neuropathies (PN) are common conditions whose treatment is still lacking in most cases. Animal models are crucial, but experimental procedures should be refined in some cases. We performed a detailed characterization of the ventral caudal nerve to contribute to a more effective assessment of axonal damage in future PN studies. PN was induced via weekly systemic injection of a neurotoxic drug (paclitaxel); we compared the control and PN-affected rats, performing serial neurophysiological evaluations of the caudal nerve for its entire length. On the same nerve portions, we performed light microscopy and ultrastructural pathological observations to assess the severity of damage and verify the integrity of the surrounding structures. Neurophysiological and morphological analyses confirmed that a severe axonopathy had ensued in the PN group, with a length-dependent modality, matching morphological observations. The site of neurophysiological recording (e.g., distance from the base of the tail) was critical for achieving useful data. A flexible experimental paradigm should be considered in animal studies investigating axonal PN, particularly if the expected severity is relevant; the mid-portion of the tail might be the most appropriate site: there damage might be remarkable but neither as extreme as at the tip of the tail nor as mild as at the base of the tail.

Translating morphology from bench side to bed side via neurophysiology: 8-min protocol for peripheral neuropathy research

BACKGROUND

Peripheral neuropathy treatment is not always satisfactory. To fill this gap, inferences from bench side are warranted, where morphological and pathogenetic determinations can be performed. Nerve conduction studies (NCS) are ideal to translate results from preclinical to clinical setting.

NEW METHODS

We propose a comprehensive 8-minute protocol for sensory-motor neurophysiological assessment, similar to routine clinical practice: sensory proximal and distal caudal nerves, motor caudal nerve, and sensory digital nerve recordings were used and tested in 2 different experimental settings. In Experiment 1 we compared control (CTRL) animals to a severe sensory-motor polyneuropathy (animals treated with vincristine [VCR]), and in Experiment 2 CTRL animals were compared to a mild sensory polyneuropathy (animals treated with oxaliplatin [OHP]). NCS were performed after 1-month of chemotherapy and matched with confirmatory neuropathological analyses.

RESULTS

VCR treated animals showed, at NCS, a relevant sensory-motor polyneuropathy ensued at the end of treatment; whereas, OHP animals showed a mild distal sensory neuropathy. These patterns were confirmed by neuropathological analysis.

COMPARISON WITH EXISTING METHODS

In literature, the majority of proposed neurophysiological protocols relies mainly on a single nerve testing, rather than a combination of them, and only a few studies tested both caudal and sciatic nerve branches, nevertheless not aiming at fully reproduce clinical protocols (e.g., seeking for length-dependency); to provide evidence of appropriateness of our protocol we applied a gold standard: neuropathology.

CONCLUSION

The simple and rapid protocol here presented can be suggested as a good translation outcome measure in preclinical setting.

Addressing the Need of a Translational Approach in Peripheral Neuropathy Research: Morphology Meets Function

Peripheral neuropathies (PNs) are a type of common disease that hampers the quality of life of affected people. Treatment, in most cases, is just symptomatic and often ineffective. To improve drug discovery in this field, preclinical evidence is warranted. In vivo rodent models allow a multiparametric approach to test new therapeutic strategies, since they can allow pathogenetic and morphological studies different from the clinical setting. However, human readouts are warranted to promptly translate data from the bench to the bedside. A feasible solution would be neurophysiology, performed similarly at both sides. We describe a simple protocol that reproduces the standard clinical protocol of a neurophysiology hospital department. We devised the optimal montage for sensory and motor recordings (neurography) in mice, and we also implemented F wave testing and a short electromyography (EMG) protocol at rest. We challenged this algorithm by comparing control animals (BALB/c mice) with a model of mild neuropathy to grasp even subtle changes. The neurophysiological results were confirmed with neuropathology. The treatment group showed all expected alterations. Moreover, the neurophysiology matched the neuropathological analyses. Therefore, our protocol can be suggested to promptly translate data from the bench to the bedside and vice versa.