Partial Reconstruction of the Nigrostriatal Circuit along a Preformed Molecular Guidance Pathway.

The overall goal of our research is to establish a preformed molecular guidance pathway to direct the growth of dopaminergic axons from embryonic ventral mesencephalon (VM), tissue placed within the substantia nigra (SN), into the striatum to reconstruct the nigrostriatal pathway in a hemi-Parkinson's disease rat model. Guidance pathways were prepared by injecting lentivirus encoding either GFP or a combination of glial-cell-line-derived neurotrophic factor (GDNF) with either GDNF family receptor α1 (GFRα1) or netrin1. In another cohort of animals, adeno-associated virus (AAV) encoding brain-derived neurotrophic factor (BDNF) was injected within the striatum after guidance pathway formation. GDNF combined with either GFRα1 or netrin significantly increased growth of dopaminergic axons out of transplants and along the pathway, resulting in a significant reduction in the number of amphetamine-induced rotations. Retrograde tract tracing showed that the dopaminergic axons innervating the striatum were from A9 neurons within the transplant. Increased dopaminergic innervation of the striatum and improved behavioral recovery were observed with the addition of BDNF. Preformed guidance pathways using a combination of GDNF and netrin1 can be used to reconstruct the nigrostriatal pathway and improve motor recovery.

Quality of life in psychogenic nonepileptic seizures and epilepsy: the role of somatization and alexithymia.

It is clear that many individuals with psychogenic nonepileptic seizures (PNESs) often present with poorer quality of life compared with those with epileptic seizures (ESs). However, the mechanisms linking seizure diagnosis to quality-of-life outcomes are much less clear. Alexithymia and somatization are emotional markers of psychological functioning that may explain these differences in quality of life. In the current study, patients from an epilepsy monitoring unit with vEEG-confirmed diagnosis of PNESs or ESs were compared on measures of alexithymia, somatization, quality of life, and a variety of demographic and medical variables. Two models using alexithymia and somatization individually as mediators of the relations between diagnosis and quality of life were tested. Results indicated that patients with PNESs had significantly poorer quality of life compared with those with ESs. Alexithymia was associated with poor quality of life in both groups but did not differentiate between diagnostic groups. Further, alexithymia did not mediate the relationship between diagnosis and quality of life. Somatization was associated with poor quality of life, and patients with PNESs reported greater somatization compared with patients with ESs. Somatization also significantly mediated the relationship between diagnosis and quality of life. In conclusion, somatization may be one mechanism affecting poor quality of life among patients with PNESs compared with ESs and should be a target of comprehensive treatments for PNESs. Alexithymia proved to be an important factor impacting quality of life in both groups and should also be targeted in treatment for patients with PNESs and patients with ESs.

Timing of antiepileptic drug withdrawal in adult epilepsy patients after neocortical surgical resection: a critically appraised topic.

BACKGROUND: The ideal efficacy outcome after surgery for medically refractory epilepsy is seizure freedom without need for antiepileptic drug (AED) therapy but the appropriate timing of AED withdrawal and other prognostic factors remain unclear. OBJECTIVE: To critically evaluate current evidence regarding factors that influence the risk of seizure relapse after tapering AEDs in adult postepilepsy surgery patients. METHODS: The objective was addressed through the development of a structured, critically appraised topic. This included a clinical scenario, structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom-line conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and a content expert in the field of epilepsy. RESULTS: A structured literature search led to selection and appraisal of a retrospective cohort study. Of 147 patients who underwent AED tapering after epilepsy surgery, 61 (41.5%) ended up seizure-free off AEDs, 47 (32%) were seizure-free with AED continuation, and 39 (26.5%) continued to have seizures while on AEDs. Risk factors associated with seizure recurrence included: less time to AED reduction [<9 mo vs. ≥9 mo; P<0.001; hazard ratio (HR)=2.83; 95% confidence interval (CI)=1.62-4.94), seizure recurrence before AED reduction (P=0.002; HR=2.43; 95% CI=1.37-4.31], normal preoperative magnetic resonance imaging (P=0.01; HR=1.96; 95% CI=1.15-3.34), and longer epilepsy duration (>11 y vs. ≤11 y; P=0.02; HR=1.75; 95% CI=1.09-2.81). Cortical location of the epileptic focus was not associated with taper success. CONCLUSION: In adults who have undergone neocortical resection surgery for medically refractory epilepsy, longer time from surgery to beginning AED taper (eg, greater than 9 months) is associated with a greater proportion of patients maintaining seizure freedom. Other risk factors associated with lower rate of seizure freedom after AED taper include longer duration of epilepsy, normal preoperative magnetic resonance imaging, and occurrence of postoperative seizures before initiation of AED withdrawal, but not cortical location of the epilepsy focus.

Do antiepileptic drugs increase the risk of suicidality in adult patients with epilepsy?: a critically appraised topic.

BACKGROUND: The US Food and Drug Administration (FDA) released an alert in 2008 regarding an increased risk of suicidality in patients taking antiepileptic drugs (AEDs). The analysis that prompted this blanket warning has since been criticized for multiple flaws, and its relevance to patients with epilepsy is unclear. OBJECTIVE: To critically assess current evidence regarding the risk of suicidality in adult patients with epilepsy taking commonly prescribed AEDs as monotherapy. METHODS: The objective was addressed through the development of a structured critically appraised topic. This included a clinical scenario, structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom-line conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and a content expert in the field of epilepsy. RESULTS: A structured literature search led to selection of one article providing the highest level of evidence currently available to answer our clinical question: a recent cohort study. The primary results of this study were based on comparisons of several AEDs to topiramate as a reference drug for any indication (including epilepsy), and identified gabapentin, lamotrigine, oxcarbazepine, tiagabine, and valproate as increasing risk of suicidality. A secondary analysis using carbamazepine as the reference drug failed to show statistically significant differences. A subgroup analysis of patients with epilepsy revealed an increased risk of suicidality in patients taking gabapentin as compared with those taking carbamazepine (relative risk, 13.92; 95% confidence interval, 1.82-106.38). CONCLUSION: Evidence of increased suicidality in patients taking AEDs for epilepsy is sparse. On the basis of this critical appraisal, gabapentin is one drug that may increase risk of suicide attempts and completions in these patients.

Axon growth across a lesion site along a preformed guidance pathway in the brain.

Our previous studies showed that axonal outgrowth from dorsal root ganglia (DRG) transplants in the adult rat brain could be directed toward a specific target location using a preformed growth-supportive pathway. This pathway induced axon growth within the corpus callosum across the midline to the opposite hemisphere. In this study, we examined whether such pathways would also support axon growth either through or around a lesion of the corpus callosum. Pathways expressing GFP, NGF, or FGF2/NGF were set up by multiple injections of adenovirus along the corpus callosum. Each pathway included the transplantation site in the left corpus callosum, 2.8 mm away from the midline, and a target site in the right corpus callosum, 2.5 mm from the midline. At the same time, a 1 mm lesion was made through the corpus callosum at the midline in an anteroposterior direction. A group of control animals received lesions and Ad-NGF injections only at the transplant and target sites, without a bridging pathway. DRG cell suspensions from postnatal day 1 or 2 rats were injected at the transplantation site three to four days later. Two weeks after transplantation, brain sections were stained using an anti-CGRP antibody. The CGRP+ axons were counted at 0.5 mm and 1.5 mm from the lesion site in both hemispheres. Few axons grew past the lesion in animals with control pathways, but there was robust axon growth across the lesion site in the FGF2/NGF and NGF-expressing pathways. This study indicated that preformed NGF and combination guidance pathways support more axon growth past a lesion in the adult mammalian brain.

Targeting axon growth from neuronal transplants along preformed guidance pathways in the adult CNS.

To re-establish neuronal circuits lost after CNS injury, transplanted neurons must be able to extend axons toward their appropriate targets. Such growth is highly restricted within the adult CNS attributable to the expression of inhibitory molecules and general lack of guidance cues to direct axon growth. This environment typically induces random patterns of growth and aberrant innervation, if growth occurs at all. To target the growth of axons from neuronal transplants, we are using viral vectors to create guidance pathways before neuronal transplantation. In this study, we transplanted postnatal rat dorsal root ganglia neurons into the corpus callosum of adult rats. Replication-incompetent adenoviruses encoding growth or guidance factors were injected along the desired pathway 1 week before cell transplantation, allowing time for sufficient protein expression by host glial cells. With expression of nerve growth factor (NGF) and basic fibroblast growth factor, sensory axons were able to grow along the corpus callosum, across the midline, and toward an NGF-expressing target in either the contralateral striatum or cortex: a distance of 7-8 mm including a 90 degree turn from white matter into gray matter. Furthermore, expression of semaphorin 3A slightly dorsal and lateral to the turning point increased the number of axons turning into the striatal target. These results show that judicious expression of neuron-specific chemoattractant and chemorepellant molecules using viral vectors can support and target axon growth from neuronal transplants in the adult CNS.

Evaluation of cellular organization and axonal regeneration through linear PLA foam implants in acute and chronic spinal cord injury.

There are few studies of neural implants in spinal cord injury (SCI) focused on supporting directed axon growth. In this study, we fabricated a macroporous poly (lactic acid) (PLA) foam with oriented inner channels. Amorphous foam without linear channels served as a control in an acute SCI injury model, and the effectiveness of foam with linear channels was further investigated in a chronic SCI model. Implants were placed into a 2 mm hemisection lesion cavity at the T8 spinal cord level in adult rats. Two weeks post-implantation, tissue sections including the implants were examined using antibodies against GFAP, p75, ED-1, laminin, GAP-43, and CGRP. Foam implants were well-integrated with the host spinal cord. In linear foams, numerous DAPI-stained cells were found within the inner channels. Schwann cells but not astrocytes had migrated within the channels. Intense laminin staining was observed throughout the extracellular matrix substrate. GAP-43- and CGRP-positive axons grew through the implants following the linear channels. In the amorphous control foams, DAPI staining distributed evenly through the pores. However, the growth of GAP-43 or CGRP-positive axons was misguided and impeded at the entrance area of the foam. Higher numbers of GAP-43 and CGRP-positive axons grew into linear foam implants after chronic SCI than acute SCI. These results suggest the potential application of linear foam implants in cell and axon guidance for SCI repair, especially for chronic SCI.

The fate of HDL particles in vivo after SR-BI-mediated selective lipid uptake.

Scavenger receptor class B type I (SR-BI) delivers cholesterol ester from HDL to cells via a selective uptake mechanism, whereby lipid is transferred from the core of the particle without concomitant degradation of the protein moiety. The precise metabolic fate of HDL particles after selective lipid uptake is not known. To characterize SR-BI-mediated HDL processing in vivo, we expressed high levels of this receptor in livers of apoA-I(-/-) mice by adenoviral vector gene transfer, and then injected the mice with a bolus of human HDL(2) traced with (125)I-dilactitol tyramine. HDL recovered from apoA-I(-/-) mice over-expressing SR-BI was significantly smaller than HDL recovered from control mice as measured by non-denaturing gel electrophoresis. When injected into C57BL/6 mice, these HDL "remnants" were rapidly converted to HDL(2)-sized lipoprotein particles, and were cleared from the plasma at a rate similar to HDL(2). In assays in cultured cells, HDL remnants did not stimulate ATP-binding cassette transporter A1-dependent cholesterol efflux. When mixed with mouse plasma ex vivo, HDL remnants rapidly converted to larger HDL particles. These studies identify a previously ill-defined pathway in HDL metabolism, whereby SR-BI generates small, dense HDL particles that are rapidly remodeled in plasma. This remodeling pathway may represent a process that is important in determining the rate of apoA-I catabolism and HDL-mediated reverse cholesterol transport.