Cytokine therapy‐mediated neuroprotection in a Friedreich's ataxia mouse model

Abstract

ObjectivesFriedreich's ataxia is a devastating neurological disease currently lacking any proven treatment. We studied the neuroprotective effects of the cytokines, granulocyte‐colony stimulating factor (G‐CSF) and stem cell factor (SCF) in a humanized murine model of Friedreich's ataxia.MethodsMice received monthly subcutaneous infusions of cytokines while also being assessed at monthly time points using an extensive range of behavioral motor performance tests. After 6 months of treatment, neurophysiological evaluation of both sensory and motor nerve conduction was performed. Subsequently, mice were sacrificed for messenger RNA, protein, and histological analysis of the dorsal root ganglia, spinal cord, and cerebellum.ResultsCytokine administration resulted in significant reversal of biochemical, neuropathological, neurophysiological, and behavioural deficits associated with Friedreich's ataxia. Both G‐CSF and SCF had pronounced effects on frataxin levels (the primary molecular defect in the pathogenesis of the disease) and a regulators of frataxin expression. Sustained improvements in motor coordination and locomotor activity were observed, even after onset of neurological symptoms. Treatment also restored the duration of sensory nerve compound potentials. Improvements in peripheral nerve conduction positively correlated with cytokine‐induced increases in frataxin expression, providing a link between increases in frataxin and neurophysiological function. Abrogation of disease‐related pathology was also evident, with reductions in inflammation/gliosis and increased neural stem cell numbers in areas of tissue injury.InterpretationThese experiments show that cytokines already clinically used in other conditions offer the prospect of a novel, rapidly translatable, disease‐modifying, and neuroprotective treatment for Friedreich's ataxia. Ann Neurol 2017;81:212–226

Bone marrow transplantation stimulates neural repair in Friedreich's ataxia mice

“…We recently demonstrated that the BM stem cell–mobilizing cytokines G‐CSF and SCF display strong neuroprotective effects in the YG8R mouse model (without prior BMT) 16. Here, we show that the combination of G‐CSF and SCF not only displays direct neuroprotective effects in FA,16 but also aids the delivery of BM cells to sites of FA‐associated injury, stimulating neural repair.…”

“…These mice are frataxin‐deficient and develop progressive neurodegeneration and cardiac pathology 16, 21, 30…”

“…These mice are frataxindeficient and develop progressive neurodegeneration and cardiac pathology. 16,21,30 Detection of EGFP-BM Chimerism and Mobilization of PB Mononuclear Cells in Mice with FA We successfully established chimeric (wild-type control or YG8R) mice stably reconstituted with EGFP-expressing BM cells containing wild-type copies of the Fxn gene (see Fig 1). At 6 weeks post-transplantation, approximately 95% of nucleated cells within the PB of transplanted mice were EGFP-positive and thus donorderived.…”

“…Impaired mobilization of progenitor cells may be inherent to the disease 37 ; in support of this, we have previously reported a deficiency in neural precursors found throughout the nervous system of YG8R mice. 16 EGFP-expressing BM cells expressed wild-type frataxin, and neurological improvements may relate to the elevated levels of frataxin within the nervous system. Our protein expression and histological studies support an increase in neuronal frataxin levels post-transplant.…”

“…Immunofluorescent labeling and microscopic imaging has been described previously. 16 Primary antibodies used were ßIIItubulin (ab78078, 1:250; Abcam, Cambridge, MA), calbindin-D28K (C2724, 1:500; Sigma-Aldrich, St Louis, MO), CD11b/ c (ab1211, 1:100, Abcam), EGFP (ab6556, 1:500, Abcam), glial fibrillary acidic protein (GFAP; ab33922, 1:200, Abcam), IBA-1 (ab5076, 1:200, Abcam), NeuN (ab177487, 1:500 and ab104224, 1:500, Abcam), S100 (MAB079, 1:200; Millipore, Billerica, MA), S100 (Z0311, 1:200; Dako, Carpinteria, CA). Secondary antibodies were Alexa Fluor 488/555, goat/donkey antimouse (1:500), Alexa Fluor 488/555, goat/donkey anti-rabbit Experimental protocol using wild-type (WT) and YG8R mice to investigate the effects of allogeneic BMT.…”