Upregulation of Apol8 by Epothilone D facilitates the neuronal relay of transplanted NSCs in spinal cord injury

Background Microtubule-stabilizing agents have been demonstrated to modulate axonal sprouting during neuronal disease. One such agent, Epothilone D, has been used to treat spinal cord injury (SCI) by promoting axonal sprouting at the lesion site after SCI. However, the role of Epothilone D in the differentiation of neural stem cells (NSCs) in SCI repair is unknown. In the present study, we mainly explored the effects and mechanisms of Epothilone D on the neuronal differentiation of NSCs and revealed a potential new SCI treatment. Methods In vitro differentiation assays, western blotting, and quantitative real-time polymerase chain reaction were used to detect the effects of Epothilone D on NSC differentiation. Retrograde tracing using a pseudotyped rabies virus was then used to detect neuronal circuit construction. RNA sequencing (RNA-Seq) was valuable for exploring the target gene involved in the neuronal differentiation stimulated by Epothilone D. In addition, lentivirus-induced overexpression and RNA interference technology were applied to demonstrate the function of the target gene. Last, an Apol8-NSC-linear ordered collagen scaffold (LOCS) graft was prepared to treat a mouse model of SCI, and functional and electrophysiological evaluations were performed. Results We first revealed that Epothilone D promoted the neuronal differentiation of cultured NSCs and facilitated neuronal relay formation in the injured site after SCI. Furthermore, the RNA-Seq results demonstrated that Apol8 was upregulated during Epothilone D-induced neuronal relay formation. Lentivirus-mediated Apol8 overexpression in NSCs (Apol8-NSCs) promoted NSC differentiation toward neurons, and an Apol8 interference assay showed that Apol8 had a role in promoting neuronal differentiation under the induction of Epothilone D. Last, Apol8-NSC transplantation with LOCS promoted the neuronal differentiation of transplanted NSCs in the lesion site as well as synapse formation, thus improving the motor function of mice with complete spinal cord transection. Conclusions Epothilone D can promote the neuronal differentiation of NSCs by upregulating Apol8, which may provide a promising therapeutic target for SCI repair.

Taurine Promotes Axonal Sprouting Through Mitochondrial Improvement in Stroke

BackgroundBrain plasticity including axonal sprouting has been recognized in restoring motor function in ischemic stroke. Mitochondrion plays a crucial role in determining axonal sprouting in ischemic injury. Taurine (TAU) could protect brain against experimental stroke as one of the richest amino acids. However, the role of TAU on axonal sprouting and the specific potential mechanism on mitochondria of stroke were unclear. MethodsFocal cerebral cortical ischemia in C57BL/6 mice was preceded. Motor function was assayed by the Rota-Rod test on D7, D14, and D28 after stroke. Axonal sprouting was detected using immunocytochemistry with biotinylated dextran amine (BDA). The expressions of mitochondrial DNA (mtDNA), Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG-1a) and Transcription factor A of mitochondria (TFAM) were measured by RT-qPCR. ResultsTAU treatment significantly recovered the motor function of focal cerebral cortical ischemic mice. And TAU promoted axonal sprouting. It was also observed that TAU enhanced mtDNA content, increased the levels of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG-1a) and Transcription factor A of mitochondria (TFAM). ConclusionsCollectively, the data illustrated that TAU exerted a promoting influence on axonal sprouting, through mitochondrial improvement in cerebral ischemic stroke.

The neuroprotective effect of meloxicam in a transient ischemia model involves an increase in axonal sprouting but a decrease in new neuron formation after 7 days of reperfusion

The inflammatory response plays an important role in neuroprotection and regeneration after ischemic insult. The use of non-steroidal anti-inflammatory drugs has been a matter of debate as to whether they have beneficial or detrimental effects. In this context, the effects of the anti-inflammatory agent meloxicam have been scarcely documented after stroke, but its ability to inhibit both cyclooxygenase isoforms (1 and 2) could be a promising strategy to modulate post-ischemic inflammation. This study analyzed the effect of the anti-inflammatory agent meloxicam in a transient focal ischemia model in rats, measuring its neuroprotective effect after 48 hours and 7 days of reperfusion and the effects of the treatment on the glial scar and regenerative events such as the generation of new progenitors in the subventricular zone and axonal sprouting at the edge of the damaged area. We show that meloxicam's neuroprotective effects remained after 7 days of reperfusion even if its administration was restricted to the two first days after ischemia. Moreover, meloxicam treatment modulated glial scar reactivity, which matched with an increase in axonal sprouting. However, this treatment decreased the formation of neuronal progenitor cells. This study discusses the dual role of anti-inflammatory treatments after stroke and encourages the careful analysis of both the neuroprotective and the regenerative effects in preclinical studies.

Neonatal 6-OHDA lesion of the SNc induces striatal compensatory sprouting from surviving SNc dopaminergic neurons without VTA contribution

Dopamine (DA) neurons of the substantia nigra pars compacta (SNc) are uniquely vulnerable to neurodegeneration in Parkinson’s disease (PD). We hypothesize that their large axonal arbor is a key factor underlying their vulnerability, due to increased bioenergetic, proteostatic and oxidative stress. In keeping with this model, other DAergic populations with smaller axonal arbors are mostly spared during the course of PD and are more resistant to experimental lesions in animal models. Aiming to improve mouse PD models, we examined if neonatal partial SNc lesions could lead to adult mice with fewer SNc DA neurons that are endowed with larger axonal arbors because of compensatory mechanisms. We injected 6-hydroxydopamine (6-OHDA) unilaterally in the SNc at an early postnatal stage at a dose selected to induce loss of approximately 50% of SNc DA neurons. We find that at 10- and 90-days after the lesion, the axons of SNc DA neurons show massive compensatory sprouting, as revealed by the proportionally smaller decrease in tyrosine hydroxylase (TH) in the striatum compared to the loss of SNc DA neuron cell bodies. The extent and origin of this axonal sprouting was further investigated by AAV-mediated expression of eYFP in SNc or ventral tegmental area (VTA) DA neurons of adult mice. Our results reveal that SNc DA neurons have the capacity to substantially increase their axonal arbor size and suggest that mice designed to have reduced numbers of SNc DA neurons could potentially be used to develop better mouse models of PD, with elevated neuronal vulnerability.Graphical abstract textWe describe a technique to induce the loss of approximately 50% of SNc DA neurons in neonate mice using unilateral intranigral 6-OHDA (left panel).Compensatory axonal sprouting was observed in the striatum as early as 10 days following the lesion (at P15), with effects lasting until adulthood (P90).Conditional AAV-mediated expression of eYFP (green) reveals SNc DA neurons, projecting to the dorsal striatum (middle panel), and not VTA DA neurons, projecting to the ventral striatum (right panel), as the main source of compensatory axonal sprouting.Graphical abstract

Tongxinluo promotes axonal plasticity and functional recovery after stroke

BackgroundThe aim of this study was to investigate the neural plasticity in contralesional cortex and the effects of tongxinluo (TXL) in cerebral ischemic rats.MethodologyWe used stroke-prone renovascular hypertensive (RHRSP) cerebral ischemia rat models to study the effect of TXL and the underlying mechanisms. We performed foot-fault and beam-walking tests to evaluate the motor function of rats after cortical infarction. Biotinylated dextran amine (BDA) was used to track axonal sprouting and neural connections.ResultsTXL enhanced the recovery of motor function in cerebral infarction rats. TXL increased axonal sprouting in the peri-infarcted area but not in the corpus callosum, indicating in situ origination instead of crossing between cortical hemispheres through the corpus callosum. TXL promoted the sprouting of corticospinal axons into the denervated side of spinal gray matter. The synaptophysin (SYN)-positive intensity in the peri-infarcted area of TXL-treated group was greater than that in the vehicle group. We observed co-localization of SYN with BDA-positive fibers in the denervated spinal cord gray matter in the TXL group, suggesting that axonal remodeling and synaptic connections were promoted by TXL.ConclusionTXL may promote the recovery of neurological function by promoting the axonal remodeling and synapse formation of motor neuronal fibers after focal cortical infarction in hypertensive rats.