Protective effects of gonadal hormones on spinal motoneurons following spinal cord injury

Abstract

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. The majority of treatment strategies after SCI have concentrated on the damaged spinal cord, for example working to reduce lesion size or spread, or encouraging regrowth of severed descending axonal projections through the lesion, hoping to re-establish synaptic connectivity with caudal targets. In our work, we have focused on a novel target for treatment after SCI, surviving spinal motoneurons and their target musculature, with the hope of developing effective treatments to preserve or restore lost function following SCI. We previously demonstrated that motoneurons, and the muscles they innervate, show pronounced atrophy after SCI. Importantly, SCI-induced atrophy of motoneuron dendrites can be attenuated by treatment with gonadal hormones, testosterone and its active metabolites, estradiol and dihydrotestosterone. Similarly, SCI-induced reductions in muscle fiber cross-sectional areas can be prevented by treatment with androgens. Together, these findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be ameliorated by treatment with gonadal hormones, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

Keywords

• testosterone; dihydrotestosterone; estradiol; steroids; atrophy; neuroprotection; morphology; dendrites; muscle fibers; retrograde labeling