FGF-2 is required to prevent astrogliosis in the facial nucleus after facial nerve injury and mechanical stimulation of denervated vibrissal muscles

Recently,we have shown that manual stimulation of paralyzed vibrissal muscles after facial-facial anastomosis reduced the poly-innervation of neuromuscular junctions and restored vibrissal whisking.Using gene knock outs,we found a differential dependence of manual stimulation effects on growth factors.Thus,insulin-like growth factor-1 and brain-derived neurotrophic factor are required to underpin manual stimulation-mediated improvements,whereas FGF-2 is not.The lack of dependence on FGF-2 in mediating these peripheral effects prompted us to look centrally,i.e.within the facial nucleus where increased astrogliosis after facial-facial anastomosis follows ＂synaptic stripping＂.We measured the intensity of Cy3-fluorescence after immunostaining for glial fibrillary acidic protein（GFAP） as an indirect indicator of synaptic coverage of axotomized neurons in the facial nucleus of mice lacking FGF-2（FGF-2^（-/-） mice）.There was no difference in GFAP-Cy3-fluorescence（pixel number,gray value range17-103） between intact wildtype mice（2.12± 0.37×10~7） and their intact FGF-2^（-/-） counterparts（2.12±0.27×10~7） nor after facial-facial anastomosis ＋handling（wildtype：4.06±0.32×10~7;FGF-2^（-/-）：4.39±0.17×10~7）.However,after facial-facial anastomosis,GFAP-Cy3-fluorescence remained elevated in FGF-2^（-/-）-animals（4.54±0.12×10~7）,whereas manual otimulation reduced the intensity of GFAP-immunofluorescence in wild type mice to values that were not significantly different from intact mice（2.63±0.39×10）.We conclude that FGF-2 is not required to underpin the beneficial effects of manual stimulation at the neuro-muscular junction,but it is required to minimize astrogliosis in the brainstem and,by implication,restore synaptic coverage of recovering facial motoneurons.

Working toward an integrated plasticity/network framework for repetitive transcranial magnetic stimulation to inform tailored treatments

Non-invasive brain stimulation techniques(NIBS),including repetitive transcranial magnetic stimulation(rTMS) and transcranial electric stim ulation(tES),are increasingly being adopted clinically for treatment of neuropsychiatric and neurological disorders,albeit with varying success.The rationale behind the use of NIBS has historically been that stim ulation techniques modulate neuronal activity in the targeted region and consequently induce plasticity which can lead to therapeutic outcomes.

Optimising repetitive transcranial magnetic stimulation for neural circuit repair following traumatic brain injury

While it is well-known that neuronal activity promotes plasticity and connectivity, the success of activity-based neural rehabilitation programs remains extremely limited in human clinical experience because they cannot adequately control neuronal excitability and activity within the injured brain in order to induce repair. However, it is possible to non-invasively modulate brain plasticity using brain stimu- lation techniques such as repetitive transcranial （rTMS） and transcranial direct current stimulation （tDCS） techniques, which show promise for repairing injured neural circuits （Henrich-Noack et al., 2013; Lefaucher et al., 2014）. Yet we are far from having full control of these techniques to repair the brain following neurotrauma and need more fundamen- tal research （Ellaway et al., 2014; Lefaucher et al., 2014）. In this perspective we discuss the mechanisms by which rTMS may facilitate neurorehabilitation and propose experimental techniques with which magnetic stimulation may be investi- gated in order to optimise its treatment potential.

Strategies to limit dysmyelination during secondary degeneration following neurotrauma

Following trauma to the central nervous system （CNS）, cells in the lesion site die rapidly. In addition, neurons and glia be- yond the initial lesion are vulnerable. These cells can undergo delayed death due to metabolic events that follow the initial trauma, via mechanisms thought to he triggered by gluta- mate-induced excitotoxicity and Ca2＋ overload, leading to mitochondrial dysfunction, associated with increased oxida- tive stress （Camello-Almaraz et al., 2006; Peng and Jou, 2010）. The resultant death of areas of grey and white matter adjacent to the lesion site is termed secondary degeneration, and is a feature of brain and spinal cord injury （Park et al., 2004; Gi- aume et al., 2007）. Secondary degeneration contributes sub- stantially to functional loss following neurotrauma （Profyris et al., 2004; Farkas and Povlishock, 2007） and rescuing this intact, but vulnerable, tissue is considered critical to mini- mising adverse sequelae and improving long term functional outcomes after CNS trauma （Fehlings et al., 2012）. However, our understanding of many of the metabolic events thought to contribute to secondary degeneration is based largely on in vitro studies （Khodorov, 2004; Tretter et al., 2007; Peng and Jou, 2010） and there is a need to confirm the relevance of these mechanisms in vivo, as well as their structural and func- tional consequences.

The complex contribution of the astrocyte scar

It is tempting to assign positive or negative roles to components of neurotrauma pathology,in an effort to generate an ordered picture and design therapeutic strategies accordingly.However nature is seldom so obliging.This principle is elegantly illustrated in a recent publication from Anderson,

Delayed treatment of secondary degeneration following acute optic nerve transection using a combination of ion channel inhibitors

Studies have shown that a combined application of several ion channel inhibitors immediately after central nervous system injury can inhibit secondary degeneration. However, for clinical use, it is necessary to determine how long after injury the combined treatment of several ion channel inhibitors can be delayed and efficacy maintained. In this study, we delivered Ca^2＋ entry-inhibiting P2X7 receptor antagonist oxidized-ATP and AMPA receptor antagonist YM872 to the optic nerve injury site via an iPRECIO-@ pump immediately, 6 hours, 24 hours and 7 days after partial optic nerve transection surgery. In addition, all of the ion channel inhibitor treated rats were administered with calcium channel antagonist lomerizine hydrochloride. It is important to note that as a result of implantation of the particular pumps required for programmable delivery of therapeutics directly to the injury site, seromas occurred in a significant proportion of animals, indicating infection around the pumps in these animals. Improvements in visual function were observed only when treatment was delayed by 6 hours; phosphorylated Tau was reduced when treatment was delayed by 24 hours or 7 days. Improvements in structure of node/paranode of Ranvier and reductions in oxidative stress indicators were also only observed when treatment was delayed for 6 hours, 24 hours, or 7 days. Benefits of ion channel inhibitors were only observed with time-delayed treatment, suggesting that delayed therapy of Ca^2＋ ion channel inhibitors produces better neuroprotective effects on secondary degeneration, at least in the presence of seromas.

Developmental transcription factors in age-related CNS disease: a phoenix rising from the ashes?

Few would doubt that understanding the developmental landscape from which a mature neuron is derived is essential to understand its biology.The temporal and spatial position of a cell from the very earliest stages of development predicts the unique combinations of growth factors it will subsequently be exposed to.