Chronic spinal cord injury (SCI) is a formidable hurdle that prevents a large number of injured axons from crossing the lesion, particularly the corticospinal tract (CST). This study shows that Pten deletion in the adult mouse cortex enhances compensatory sprouting of uninjured CST axons. Furthermore, forced upregulation of mammalian target of rapamycin (mTOR) initiated either 1 month or 1 year after injury promoted regeneration of CST axons.Ourresultsindicatethatbothdevelopmentalandinjury-inducedmTORdownregulationincorticospinalmotorneuronscanbereversedinadults. Modulating neuronal mTOR activity is a potential strategy for axon regeneration after chronic SCI.

Cell-type-specific G protein-coupled receptor (GPCR) signaling regulates distinct neuronal responses to various stimuli and is essential for axon guidance and targeting during development. However, its function in axonal regeneration in the mature CNS remains elusive. We found that subtypes of intrinsically photosensitive retinal ganglion cells (ipRGCs) in mice maintained high mammalian target of rapamycin (mTOR) levels after axotomy and that the light-sensitive GPCR melanopsin mediated this sustained expression. Melanopsin overexpression in the RGCs stimulated axonal regeneration after optic nerve crush by up-regulating mTOR complex 1 (mTORC1). The extent of the regeneration was comparable to that observed after phosphatase and tensin homolog (Pten) knockdown. Both the axon regeneration and mTOR activity that were enhanced by melanopsin required light stimulation and Gq/11 signaling. Specifically, activating Gq in RGCs elevated mTOR activation and promoted axonal regeneration. Melanopsin overexpression in RGCs enhanced the amplitude and duration of their light response, and silencing them with Kir2.1 significantly suppressed the increased mTOR signaling and axon regeneration that were induced by melanopsin. Thus, our results provide a strategy to promote axon regeneration after CNS injury by modulating neuronal activity through GPCR signaling.axon regeneration | neuronal activity | melanopsin | GPCR | mTOR S evered axons in the adult mammalian CNS do not spontaneously regenerate to restore lost functions. The failure of axons to regenerate is mainly attributed to the diminished growth capacity of neurons as well as an inhibitory environment (1-6). Optic nerves have been extensively studied for mechanisms regulating axon regeneration in CNS. When presented with permissive substrates such as a sciatic nerve graft, only axons of small populations of retinal ganglion cells (RGCs) regrow into the graft (7). When the intrinsic growth program is boosted, distinct subtypes of RGCs regenerate their axons (8). These findings indicate that the differential responses of RGCs to axotomy and growth stimulation are related to their intrinsic properties. One of the critical determinants of the intrinsic regenerative abilities of adult RGCs is neuronal mammalian target of rapamycin (mTOR) activity (9). In retinal axons, the loss of the potential to regrow is accompanied by down-regulation of mTOR activity in RGCs with maturation, and further reduction after axotomy. However, a small percentage of RGCs maintain high mTOR activation levels after optic nerve crush (9, 10). One can ask whether specific subsets of RGCs differ in their ability to maintain mTOR activation. Deciphering the physiological mechanism behind the mTOR maintenance could help elucidate the differential responses of neurons to injury signals and develop strategies to promote axon regeneration.Type 1 melanopsin expressing intrinsically photosensitive retinal ganglion cells (M1 ipRGCs) and αRGCs are resistant to axotomy-induced cell death (8, 11). M1 ipRGCs mainl...

Purpose: To investigate the morphological feature, visual acuity, and prevalence of macular complications in highly myopic eyes with different categories of myopic maculopathy (MM) according to the META-PM classification system. Methods: The clinical records of 1,132 consecutive patients (1,841 eyes) with high myopia (refractive error ≤ −6D and axial length ≥26.5 mm), who visited the High Myopia Clinic at the Zhongshan Ophthalmic Center from January 2014 to July 2017, were reviewed. Fundus photograph, optical coherence tomography, axial length, refractive error, and best-corrected visual acuity were measured in each patient. Myopic maculopathy was graded from fundus photographs according to the META-PM classification, including tessellated fundus (C1), diffuse chorioretinal atrophy (C2), patchy atrophy (C3), and macular atrophy (C4). Other macular complications, including foveoschisis, extrafoveal schisis, full-thickness macular hole, epiretinal membrane, lacquer cracks, Fuchs spot, choroidal neovascularization, macular hemorrhage, and dome-shaped macula, were also investigated. Results: Among the 1,841 eyes, 58 (3.15%) had no MM (C0), 779 (42.31%) had tessellated fundus only (C1), 524 (28.46%) had diffuse chorioretinal atrophy (C2), 352 (19.12%) had patchy chorioretinal atrophy (C3), and 128 (6.95%) had macular atrophy (C4). Age increased and best-corrected visual acuity became worse with the severity of MM (P < 0.01). Axial length was significantly longer with the severity of MM from C0 to C3 (P < 0.01), and spherical equivalent was greater with the severity of MM from C0 to C3 (P < 0.01) but was not different between C3 and C4 (P > 0.05). Subfoveal and parafoveal choroidal thicknesses were significantly thinner from C0 to C3 (P < 0.01). However, no significant difference was found between C3 and C4 in parafoveal choroidal thickness (P > 0.05). The complications were different among C0 to C4 correlated with MM (P < 0.01). The complications of foveoschisis, choroidal neovascularization, hemorrhage, lacquer cracks, Fuchs spot, dome-shaped macula, and epiretinal membrane were different between C1 and C2 (P < 0.01), but none of the complications were different between C3 and C4 (P > 0.05) except Fuchs spot (P = 0.009). Conclusion: The morphological and functional characteristics in eyes with high myopia were positively correlated with the severity of C0 to C3 MM. However, no morphological difference was found between C3 and C4. The absence of the progressive relationship between C3 and C4 might be determined.