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Comparative Study
. 2005 Feb 16;25(7):1645-53.
doi: 10.1523/JNEUROSCI.3269-04.2005.

Conditioning injury-induced spinal axon regeneration requires signal transducer and activator of transcription 3 activation

Jin Qiu  1 , William B J Cafferty, Stephen B McMahon, Stephen W N Thompson
Affiliations
Comparative Study

Conditioning injury-induced spinal axon regeneration requires signal transducer and activator of transcription 3 activation

Jin Qiu et al. J Neurosci. .

Abstract

Sensory axons in the adult spinal cord do not regenerate after injury. This is essentially because of inhibitory components in the damaged CNS, such as myelin-associated inhibitors and the glial scar. However, if the sciatic nerve is axotomized before injury of the dorsal column, injured axons can regenerate a short distance in the spinal cord. Here, we show that sciatic nerve transection results in time-dependent phosphorylation and activation of the transcription factor, signal transducer and activator of transcription 3 (STAT3), in dorsal root ganglion (DRG) neurons. This effect is specific to peripheral injuries and does not occur when the dorsal column is crushed. Sustained perineural infusion of the Janus kinase 2 (JAK2) inhibitor AG490 to the proximal nerve stump can block STAT3 phosphorylation after sciatic nerve transection and results in reduced growth-associated protein 43 upregulation and compromised neurite outgrowth in vitro. Importantly, in vivo perineural infusion of AG490 also significantly attenuates dorsal column axonal regeneration in the adult spinal cord after a preconditioning sciatic nerve transection. We conclude that STAT3 activation is necessary for increased growth ability of DRG neurons and improved axonal regeneration in the spinal cord after a conditioning injury.

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Figures

Figure 1.
Figure 1.
Time course of STAT3 phosphorylation in response to sciatic nerve transection and dorsal column crush. pSTAT3 immunoreactivity was analyzed in L4 and L5 DRGs after left sciatic nerve transection at the midthigh level or bilateral dorsal column crush. The percentage of pSTAT3-positive cells was calculated against the total number of neurons with DAPI staining. In DRG sections from naive animals (A) and all contralateral ganglia (B), pSTAT3 staining was minimal (7.3 ± 4.3 and 10.7 ± 6.2%, respectively). Six hours (C), 2 d (D), 1 week (E), and 1 month (F) after sciatic nerve transection, there was a significant increase in the proportion of nuclear profiles expressing pSTAT3 compared with contralateral DRGs (90.2 ± 12.7, 68.4 ± 9.5, 34.9 ± 11.2, and 24.1 ± 6.2% compared with 10.7 ± 6.2%; p < 0.05 in all cases; Student's t test; n = 5). This elevation in pSTAT was not observed at the same time points after dorsal column (DC) crush (data not shown). Scale bar, 50 μm. G, Quantification of the proportion of nuclear profiles expressing pSTAT3 in DRGs after left sciatic nerve (SN) transection and bilateral dorsal column crush. Con, Control; Non-op., nonoperated. *p < 0.05.
Figure 2.
Figure 2.
STAT3 phosphorylation induced by sciatic nerve transection is blocked by perineural infusion of the JAK2 inhibitor AG490. pSTAT3 immunoreactivity was analyzed in L4 and L5 DRGs after left sciatic nerve transection at the midthigh level and continuous perineural infusion of either saline or 500 μm AG490 to the proximal stump at the time of injury. The proportion of nuclear profiles expressing pSTAT3 in ipsilateral ganglia was calculated against the total number of neurons with DAPI staining. A, Contralateral DRGs treated with either saline or AG490 expressed a minimal amount of pSTAT. Continuous infusion of AG490 (C) to the proximal nerve stump for 4 weeks significantly reduced the proportion of nuclear profiles expressing pSTAT3 compared with the saline treatment group (B) (16.3 ± 5.1 compared with 26.3 ± 6.4%, respectively; p < 0.05; Student's t test; n = 5). Scale bar, 50 μm. D, Quantification of pSTAT3 staining in contralateral [C] and ipsilateral [I] L4 and L5 DRGs after left sciatic nerve transection and continuous infusion of either saline or a JAK2 inhibitor, AG490. *p < 0.05.
Figure 3.
Figure 3.
Increased expression of GAP43 induced by sciatic nerve transection is blocked by JAK2 inhibition. Expression of GAP43 (A-C) and NF200 (D-F) was analyzed in contralateral (A, D, G) and ipsilateral (B, C, E, F, H, I) L4 and L5 DRGs after left sciatic nerve transection at the midthigh level and continuous perineural infusion of either saline (B, E, H) or 500 μm AG490 (C, F, I) to the proximal stump at the time of injury. Overlay of the GAP43 and NF200 immunoreactivity is shown in G-I. GAP43 expression is significantly elevated in ipsilateral ganglia after sciatic nerve transection (B), and the effect is reduced by perineural infusion of AG490 (C). The proportion of neuronal profiles coexpressing GAP43 and NF200 (yellow profiles) is also significantly reduced after perineural infusion of AG490 (H, I). Scale bar, 50 μm. J, Quantification of the proportion of neuronal profiles expressing GAP43 in contralateral [C] and ipsilateral [I] L4 and L5 DRGs after left sciatic nerve transection and continuous infusion of either saline or the JAK2 inhibitor AG490. K, Quantification of the proportion of neuronal profiles coexpressing NF200 and GAP43 in contralateral [C] and ipsilateral [I] L4 and L5 DRGs after left sciatic nerve transection and continuous infusion of either saline or a JAK2 inhibitor, AG490. *p < 0.05.
Figure 4.
Figure 4.
JAK2 inhibition at the time of injury blocks the conditioning effect of sciatic nerve transection on neurite outgrowth in vitro. Neurite outgrowth analysis was performed with contralateral (A, C) and ipsilateral (B, D) L4 and L5 DRG neurons after left sciatic nerve transection at the midthigh level and continuous perineural infusion of either saline (A, B) or 500 μm AG490 (C, D) to the proximal stump for 1 week. Dissociated DRG neurons were cultured for 18 h and then fixed and immunostained for β-tubulin. Scale bar, 100 μm. Perineural infusion of 500 μm AG490 at the time of injury significantly reduced neurite elongation (E) within the culture period (179.6 ± 22.3 compared with 333.4 ± 19.7%; *p < 0.05; Student's t test; n = 9) but had no effect on the percentage of neurite-bearing cells (F) (64.9 ± 1.9 compared with 73.7 ± 13.9%).
Figure 5.
Figure 5.
Conditioning lesion-induced dorsal column axonal regeneration in vivo is attenuated by perineural infusion of the JAK2 inhibitor AG490. In uninjured animals, dorsal column axons terminated in the gracile nucleus of the caudal medulla as revealed by transganglionic CTB tracing (A). A bilateral crush lesion at the T6 spinal cord level completely severed the entire dorsal column projection, which resulted in a loss of CTB immunoreactivity in the brainstem (B). The left sciatic nerve was transected, and either saline or 500 μm AG490 was infused perineurally to the proximal stump. One week later, dorsal column axons were crushed at the T6 spinal level, and tissues were harvested for analysis 1 month later. Staining of longitudinal spinal cord sections (20 μm) of CTB-traced axonal fibers shows that, in saline-treated animals (C), many dorsal column axons grow toward the lesion epicenter, and some manage to grow into or around the injury site. Continuous perineural administration of AG490 for 1 month (D) abolished regeneration of dorsal column axons after a conditioning lesion, and very few CTB-labeled axon fibers were observed immediately caudal to the injury site. E, F, CTB-labeled axonal fibers in the lumbar spinal cord in saline- and AG490-treated animals. Scale bars: A, B, 200 μm; C, D, 500 μm; E, F, 100 μm.
Figure 6.
Figure 6.
Quantification of CTB-labeled regenerating axons in longitudinal spinal cord sections from animals that received dorsal column lesion (CL) 1 week after left sciatic nerve transection and continuous infusion of either saline or the JAK2 inhibitor (inh.) AG490. Fluorescent intensity was measured at defined intervals caudal and rostral to the lesion epicenter (*p < 0.05; Student's t test; n = 5).
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References

    1. Aaronson DS, Horvath CM (2002) A road map for those who don't know JAK-STAT. Science 296: 1653-1655. - PubMed
    1. Andersen LB, Schreyer DJ (1999) Constitutive expression of GAP-43 correlates with rapid, but not slow regrowth of injured dorsal root axons in the adult rat. Exp Neurol 155: 157-164. - PubMed
    1. Banner LR, Patterson PH (1993) Major changes in the expression of the mRNAs for cholinergic differentiation factor/leukemia inhibitory factor and its receptor after injury to adult peripheral nerves and ganglia. Proc Natl Acad Sci USA 91: 7109-7113. - PMC - PubMed
    1. Bolin LM, Verity AN, Silver JE, Shooter EM, Abrams JS (1995) Interleukin-6 production by Schwann cells and induction in sciatic nerve injury. J Neurochem 64: 850-858. - PubMed
    1. Bomze HM, Bulsara KR, Iskandar BJ, Caroni P, Skene JH (2001) Spinal axon regeneration evoked by replacing two growth cone proteins in adult neurons. Nat Neurosci 4: 38-43. - PubMed

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