Methods for in vivo studies in rodents of chemotherapy induced peripheral neuropathy

Abstract

Peripheral neuropathy is one of the most common, dose limiting, and long-lasting disabling adverse events of chemotherapy treatment. Unfortunately, no treatment has proven efficacy to prevent this adverse effect in patients or improve the nerve regeneration, once it is established. Experimental models, particularly using rats and mice, are useful to investigate the mechanisms related to axonal or neuronal degeneration and target loss of function induced by neurotoxic drugs, as well as to test new strategies to prevent the development of neuropathy and to improve functional restitution. Therefore, objective and reliable methods should be applied for the assessment of function and innervation in adequately designed in vivo studies of CIPN, taking into account the impact of age, sex and species/strains features. This review gives an overview of the most useful methods to assess sensory, motor and autonomic functions, electrophysiological and morphological tests in rodent models of peripheral neuropathy, focused on CIPN. We include as well a proposal of protocols that may improve the quality and comparability of studies undertaken in different laboratories. It is recommended to apply more than one functional method for each type of function, and to perform parallel morphological studies in the same targets and models.

Keywords: Chemotherapy; Electrophysiology; Functional evaluation; Histology; Immunohistochemistry; Locomotion; Mouse; Neurotoxicity; Pain testing; Peripheral neuropathy; Rat.

Figure 1.

Electrophysiological recordings of the CMAP from the interosseus plantar muscle (A, D), the CNAPs from the fourth digital nerve (B, E) and from the tail nerve (C, F) in a control mouse (A, B, C) and in a mouse treated with cisplatin (D, E, F). Note the longer latency and the smaller amplitude of the potentials, most evident in the nerve recordings, in the cisplatin-treated mouse compared with the untreated mouse. A,D: letters signal the M wave and the H reflex wave; B,C,E,F: the arrow points to the peak of the CNAP.

Figure 2.

Pain sensibility tests. A. An electronic Von Frey device for the mechanical algesimetry test. B. Image of the stimulation with the tip of the Von Frey probe pressing the lateral side of the sole. Note the different position of the intact paw (top) and the denervated paw (bottom) of the rat. C. Plantar algesimetry apparatus for the hot algesimetry test. D. Image of rat being stimulated with the hot light beam under the paw. Reproduced with permission from Navarro, Eur. J. Neurosci. 2016; 43:271–286.

Figure 3.

Immunohistochemical images of the plantar pad of a control mouse (A, B) and a mouse treated with cisplatin (C, D), labeled against PGP9.5. The images show densely innervated sweat glands in the dermis, the subepidermal nerve plexus underlying the epidermis, the Meissner corpuscles at the papillae of the pad tip (top part of the pad), and the numerous intraepidermal nerve fibers (IENF) crossing the epidermis. Boxes in A,C are the area of epidermis magnified in B,D. Note the reduction in number of IENF and the degenerating appearance of some IENF (arrows) in the skin of the cisplatin-treated mouse.