Anatomically incomplete spinal cord injuries can be followed by functional recovery mediated, in part, by the formation of intraspinal detour circuits. Here, we show that adult mice recover tactile and proprioceptive function following a unilateral dorsal column lesion. We therefore investigated the basis of this recovery and focused on the plasticity of the dorsal column-medial lemniscus pathway. We show that ascending dorsal root ganglion (DRG) axons branch in the spinal grey matter and substantially increase the number of these collaterals following injury. These sensory fibers exhibit synapsin-positive varicosities, indicating their integration into spinal networks. Using a monosynaptic circuit tracing with rabies viruses injected into the cuneate nucleus, we show the presence of spinal cord neurons that provide a detour pathway to the original target area of DRG axons. Notably the number of contacts between DRG collaterals and those spinal neurons increases by more than 300% after injury. We then characterized these interneurons and showed that the lesion triggers a remodeling of the connectivity pattern. Finally, using re-lesion experiments after initial remodeling of connections, we show that these detour circuits are responsible for the recovery of tactile and proprioceptive function. Taken together our study reveals that detour circuits represent a common blueprint for axonal rewiring after injury.

PURPOSE:To prospectively investigate whether Lipiodol can be used as a potential imaging biomarker of tumor response after conventional transarterial chemoembolization (cTACE) for both primary and secondary liver cancer. MATERIALS AND METHODS: This prospective single-center single-arm clinical trial enrolled a total of 39 patients with primary or secondary liver malignancy [hepatocellular carcinoma (HCC), n = 22 and non-HCC, n = 17]. Patients were treated with cTACE according to a standardized protocol and underwent multimodality imaging at baseline [magnetic resonance imaging (MRI)/computed tomography (CT)/positron emission tomography (PET)]; at 24 hours post-TACE (CT); and at 30, 90, and 180 days post-TACE (MRI/CT/PET). Image data analysis included quantitative assessment of tumor characteristics, Lipiodol deposition, fluorodeoxyglucose uptake, and tumor response assessment. Statistical analysis included linear regression, Student's t tests, Wilcoxon rank sum and signed rank test, Chi-square, and Fisher's exact test. RESULTS: Image analysis demonstrated that baseline tumor diameter (R2 = 0.4, P = .0001), area (R2 = 0.45, P < .0001), volume (R2 = 0.3, P < .002), and enhancing volume (cm3, R2 = 0.23, P < .002) at baseline correlated inversely with Lipiodol tumor coverage and response rates. Baseline tumor enhancement in % of the total tumor was the only parameter to positively correlate with Lipiodol coverage (R2 = 0.189, P = .0456). Patients with high Lipiodol coverage of the tumors showed a higher tumor quantitative European Association for the Study of the Liver response rate at 30-day follow-up (P = .004). Lipiodol retention in both primary and secondary liver tumors was sustained over time, while nontarget hepatic deposits demonstrated near-complete elimination at 30-day follow-up (P < .001). CONCLUSION: Lipiodol deposition in liver tumors can be predicted using quantitative baseline imaging characteristics and correlates with tumor response. This supports another role for Lipiodol, namely, that of an imaging biomarker of tumor response after cTACE.