Expression of BCL-2 via adeno-associated virus vectors rescues thalamic neurons after visual cortex lesion in the adult rat

Reciprocal Connections Between Cortex and Thalamus Contribute to Retinal Axon Targeting to Dorsal Lateral Geniculate Nucleus

The dorsal Lateral Geniculate Nucleus (dLGN) is the primary image-forming target of the retina and shares a reciprocal connection with primary visual cortex (V1). Previous studies showed that corticothalamic input is essential for the development of thalamocortical projections, but less is known about the potential role of this reciprocal connection in the development of retinal projections. Here, we show a deficit of retinal innervation in the dLGN around E18.5 in Tra2β conditional knockout (cKO) "cortexless" mice, an age when apoptosis occurs along the thalamocortical tract and in some dLGN neurons. In vivo electrophysiology experiments in the dLGN further confirmed the loss of functional retinal input. Experiments with N-methyl-d-aspartic acid-induced V1 lesion as well as Fezf2 cKO mice confirmed that the disruption of connections between the dLGN and V1 lead to abnormal retinal projections to the dLGN. Interestingly, retinal projections to the ventral Lateral Geniculate Nucleus (vLGN) and Superior Colliculus (SC) were normal in all 3 mice models. Finally, we show that the cortexless mice had worse performance than control mice in a go-no go task with visual cues. Our results provide evidence that the wiring of visual circuit from the retina to the dLGN and V1 thereafter is coordinated at a surprisingly early stage of circuit development.

Impaired regeneration of bcl-2 lacking peripheral nerves

OBJECT

The outcome of peripheral nerve damage in still not satisfactory, despite the general capacity of peripheral nervous system to regenerate. The molecular mechanisms underlying nerve regeneration are still not clear, but it is likely that apoptosis regulating genes plays a crucial role in these processes. The aim of the present study was to establish the role of the anti-apoptotic gene bcl-2 in peripheral nerve repair.

MATERIAL AND METHODS

Sciatic nerves of bcl-2-deficient and wild type mice were transected, and immediately re-sutured. The regeneration was assessed functionally and morphologically throughout the 4-week follow-up.

RESULTS

We found markedly worse sciatic function index outcome, as well as more significant atrophy of denervated muscles in bcl-2 knock-out animals when compared with wild-type ones. The intensity of histological regeneration features, including GAP-43-positive growth cones, Schwann cells and macrophages in the distal stump of the transected nerve, was also decreased. The number of motor and sensory neurons in the relevant cross-sections of spinal cord was similar in both groups of mice.

CONCLUSION

We concluded that the bcl-2 gene plays an important role in peripheral nerve regeneration, influencing nerve injury site clearing, fiber regrowth and myelination.

L-dopa methyl ester attenuates amblyopia-induced neuronal injury in visual cortex of amblyopic cat

In the present study, we aimed to assess the potential anti-amblyopic effects of L-dopa methyl ester (LDME) on visual cortex area 17 in an amblyopic feline model induced by monocular vision deprivation. After LDME administration, pathophysiologic and ultrastructural observations were utilized to examine the morphological changes of nerve cells in visual cortex area 17. Dopamine (DA) and its metabolite contents in visual cortex area 17 were investigated through HPLC analysis. Apoptotic cells in visual cortex area 17 were evaluated by TUNEL assay. Additionally, the c-fos expression both at gene and protein levels was assessed using RT-PCR and immunohistochemistry analyses, respectively. The contents of DA and its metabolites were elevated in visual cortex area 17. Neuronal rejuvenation which occurred in visual cortex area 17 was observed through anatomical and physiological assessments. Similarly, TUNEL results showed that neuronal apoptosis was inhibited in the visual cortex of amblyopic cats by both L-dopa and LDME therapies. Meanwhile, the c-fos expression was notably up-regulated at both the mRNA and protein levels by the treatments. These findings suggested that LDME treatment could effectively increase DA and its metabolite contents, and restrain the apoptotic process, as well as elevate the c-fos expression in nerve cells of visual cortex area 17. Taken together, LDME might ameliorate the functional cytoarchitecture in visual cortex area 17 through mechanisms that elevate DA content and increase endogenous c-fos expression, as well as inhibit neuronal lesion in visual cortex tissue.

Carbon nanotube-mediated wireless cell permeabilization: drug and gene uptake

Aim: This work aims to exploit the ‘antenna’ properties of multiwalled carbon nanotubes (MWCNTs). They can be used to induce cell permeabilization in order to transfer drugs (normally impermeable to cell membranes) both in in vitro and in vivo models. Material & Methods: The performance of the MWCNTs as receiver antenna was modeled by finite element modeling. Once the appropriate field has been identified, the antenna properties of MWCNTs were investigated in sequential experiments involving immortalized fibroblast cell line (drug model: doxorubicin chemothererapeutic agent) and living mice (drug model: bcl-2 antiapoptotic gene) following stereotactic injection in the cerebral motor cortex. Results: Finite element modeling analysis predicts that our MWCNTs irradiated in the radiofrequency field resemble thin-wire dipole antennas. In vitro experiments confirmed that combination of MWCNTs and electromagnetic field treatment dramatically favors intracellular drug uptake and, most importantly, drug nuclear localization. Finally, the brain of each irradiated animal exhibits a significantly higher number of transfected cells compared with the appropriate controls. Conclusion: This wireless application has the potential for MWCNT-based intracellular drug delivery and electro-stimulation therapies.

Tf-lipoplex-mediated NGF gene transfer to the CNS: neuronal protection and recovery in an excitotoxic model of brain injury

The development of efficient systems for in vivo gene transfer to the central nervous system (CNS) may provide a useful therapeutic strategy for the alleviation of several neurological disorders. In this study, we evaluated the feasibility of nonviral gene therapy to the CNS mediated by cationic liposomes. We present evidence of the successful delivery and expression of both a reporter and a therapeutic gene in the rodent brain, as evaluated by immunohistochemical assays. Our results indicate that transferrin-associated cationic liposome/DNA complexes (Tf-lipoplexes) allow a significant enhancement of transfection activity as compared to plain complexes, and that 8/1 (+/-) Tf-lipoplexes constitute the best formulation to mediate in vivo gene transfer. We demonstrated that Tf-lipoplex-mediated nerve growth factor transgene expression attenuates the morphological damages of the kainic acid-induced lesion as assessed by 2,3,5-triphenyltetrazolium chloride (TTC) vital staining. These findings suggest the usefulness of these lipid-based vectors in mediating the delivery of therapeutic genes to the CNS.

Four-dimensional visualization of the simultaneous activity of alternative adeno-associated virus replication origins

The adeno-associated virus (AAV) inverted terminal repeats (ITRs) contain the AAV Rep protein-binding site (RBS) and the terminal resolution site (TRS), which together act as a minimal origin of DNA replication. The AAV p5 promoter also contains an RBS, which is involved in Rep-mediated regulation of promoter activity, as well as a functional TRS, and origin activity of these signals has in fact been demonstrated previously in the presence of adenovirus helper functions. Here, we show that in the presence of herpes simplex virus type 1 (HSV-1) and AAV Rep protein, p5 promoter-bearing plasmids are efficiently amplified to form large head-to-tail concatemers, which are readily packaged in HSV-1 virions if an HSV-1 DNA-packaging/cleavage signal is provided in cis. We also demonstrate simultaneous and independent replication from the two alternative AAV replication origins, p5 and ITR, on the single-cell level using multicolor-fluorescence live imaging, a finding which raises the possibility that both origins may contribute to the AAV life cycle. Furthermore, we assess the differential affinities of Rep for the two different replication origins, p5 and ITR, both in vitro and in live cells and identify this as a potential mechanism to control the replicative and promoter activities of p5.

Inflammation in areas of remote changes following focal brain lesion

Focal brain lesions can lead to metabolic and structural changes in areas distant from but connected to the lesion site. After focal ischemic or excitotoxic lesions of the cortex and/or striatum, secondary changes have been observed in the thalamus, substantia nigra pars reticulata, hippocampus and spinal cord. In all these regions, inflammatory changes characterized by activation of microglia and astrocytes appear. In the thalamus, substantia nigra pars reticulata and hippocampus, an expression of proinflammatory cytokine like tumor necrosis factor-alpha and interleukin-1beta is induced. However, time course of expression and cellular localisation differ between these regions. Neuronal damage has consistently been observed in the thalamus, substantia nigra and spinal cord. It can be present in the hippocampus depending on the procedure of induction of focal cerebral ischemia. This secondary neuronal damage has been linked to antero- and retrograde degeneration. Anterograde degeneration is associated with somewhat later expression of cytokines, which is localised in neurons. In case of retrograde degeneration, the expression of cytokines is earlier and is localised in astrocytes. Pharmacological intervention aiming at reducing expression of tumor necrosis factor-alpha leads to reduction of secondary neuronal damage. These first results suggest that the inflammatory changes in remote areas might be involved in the pathogenesis of secondary neuronal damage.

BDNF down-regulates the caspase 3 pathway in injured geniculo-cortical neurones

Visual cortex ablation in newborn rats causes a rapid and almost complete degeneration of neurones in the dorsal lateral geniculate nucleus (dLGN), as a consequence of the axotomy of geniculo-cortical fibres. Death of dLGN neurones occurs by apoptosis and is partially prevented (approximately 50%) by intraocular delivery of brain-derived neurotrophic factor (BDNF). Here we investigated the molecular mechanisms of BDNF-mediated neuroprotection. We found that exogenous administration of BDNF partially decreases (approximately 50%) the up-regulation of apoptotic proteins (phosphorylated c-Jun, cytochrome C and cleaved caspase 3), that occurs in dLGN neurones following visual cortex ablation at postnatal day 7. These results demonstrate that the neuroprotective action of BDNF on axotomised dLGN neurones involves the partial blockade of well-characterised apoptotic pathways.

Bcl-2 overexpression does not promote axonal regeneration of the entorhino-hippocampal connections in vitro after axotomy

CNS lesions trigger cell death in injured neurons and glia. Genes of the bcl-2 family play crucial roles in the control of apoptosis and cell survival in the CNS. Recently, it has been suggested that overexpression of bcl-2 induces axonal elongation and regeneration in vitro and in vivo. Here, we analyze the regenerative potential of bcl-2 overexpression in the axotomized entorhino-hippocampal connection in organotypic slice cocultures. Our results show that in slice cocultures from bcl-2-overexpressing mice, there is a decrease in the number of dead neurons in the entorhinal cortex. In addition, axonal regeneration is not enhanced after axotomy. Thus, in the entorhino-hippocampal formation in vitro, bcl-2 overexpression rescues neurons from axotomy-induced cell death but fails to enhance the regeneration of the entorhino-hippocampal connection.

Bcl-2 deficiency deprives peripheral nerves of neurotrophic activity against injured optic nerve

Optic nerve injury leads to retinal ganglion cell apoptosis, thus preventing fiber regeneration. Peripheral nerve grafts are known to promote survival and regeneration in injured adult mammalian central nervous system, including optic nerve, but the mechanisms of their activity remain unclear. It is likely that they attenuate the apoptotic cascade triggered by axotomy in retinal ganglion cells. The aim of this work was to examine the role of the antiapoptotic gene bcl-2 in the optic nerve regeneration induced by such grafts. Experiments were carried out on bcl-2-deficient and wild-type mice. We have reported previously that predegeneration markedly enhances neurotrophic activity of peripheral nerve grafts, so we applied both predegenerated and non-predegenerated implants to the transected optic nerves. We studied the neurotrophic effects of bcl-2-deficient grafts on wild-type and bcl-2 knock-out optic nerves, as well as wild-type grafts on both strains of mouse optic nerves. After application of fluorescent dye to the end of the graft, we counted the stained retinal ganglion cells. Predegenerated wild-type grafts promoted survival and outgrowth of retinal ganglion cells axons in both types of mice. By contrast, non-predegenerated and predegenerated bcl-2-deficient grafts induced little or no regeneration in the optic nerves. These results indicate that the lack of bcl-2 gene does not deprive retinal ganglion cells of their regenerative potential. At the same time, we found that bcl-2 knock-out dispossesses peripheral nerves of their neurotrophic activity.

Provision of brain-derived neurotrophic factor via anterograde transport from the eye preserves the physiological responses of axotomized geniculate neurons

The neurotrophic factors of the nerve growth factor family (neurotrophins) have been shown to promote neuronal survival after brain injury and in various models of neurodegenerative conditions. However, it has not been determined whether neurotrophin treatment results in the maintenance of function of the rescued cells. Here we have used the retrograde degeneration of geniculate neurons as a model system to evaluate neuronal rescue and sparing of function after administration of brain-derived neurotrophic factor (BDNF). Death of geniculate neurons was induced by a visual cortex lesion in adult rats, and exogenous BDNF was delivered to the axotomized geniculate cells via anterograde transport after injection into the eye. By microelectrode recordings from the geniculate in vivo we have measured several physiological parameters such as contrast threshold, spatial resolution (visual acuity), signal-to-noise ratio, temporal resolution, and response latency. In control lesioned animals we found that geniculate cell dysfunction precedes the onset of neuronal death, indicating that an assessment of neuronal number per se is not predictive of functional performance. The administration of BDNF resulted in a highly significant cell-saving effect up to 2 weeks after the cortical damage and maintained nearly normal physiological responses in the geniculate. This preservation of function in adult axotomized neurons suggests possible therapeutic applications of BDNF.