Selective ablation of rat knee joint innervation with injected immunotoxin: A potential new model for the study of neuropathic arthritis

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Abstract
Neuropathic arthropathy is a severe chronic degenerative condition associated with decreased or absent I sensory innervation of the involved joint. Existing animal models of neuropathic arthritis are limited by the technical difficulties of obtaining either highly selective or complete joint denervation in a minimally invasive fashion. We undertook experiments to determine the feasibility of using the newly described method of selective neuronal lesioning with injected immunotoxin as a means of creating a more tractable model of neuropathic arthritis. Retrograde tracing with fluorochrome revealed that the knee joint of the female Wistar rat is supplied by 581 ± 31 (mean ± SD) joint afferents. Immunohistochemistry confirmed that virtually all sensory neurons in the rat express the cell surface receptor Thy I. Injection of rat knee joints with an immunotoxin targeted toward Thy 1 resulted in the selective ablation of an average of 88% of the joint afferents identified with fluorochroime that are normally found in the ipsilateral L3 and L4 ganglia.