GABAergic neurons in human spinal cord cultures: a computer-aided analysis of normal and thienyl-phencyclidine-treated cells

Long-term fate of human telencephalic progenitor cells grafted into the adult mouse brain: effects of previous amplification in vitro

We assessed the developmental potential of human telencephalic progenitor cells, with and without previous amplification in vitro, following grafting into the nonlesioned adult mouse CNS. Cell suspensions, shown to contain neuroepithelium-like and neuroblast-like cells, were injected into the subventricular zone (SVZ) and the striatum. These two regions were selected for comparative studies because one, the SVZ, is mitotically active, whereas the other, the striatum, is mitotically inactive. In situ hybridization with a human-specific Alu probe showed that the cells survived for up to 30 weeks in both targets and migrated away from the injection site. Fresh cells continued to proliferate and gave rise to very extended grafts before differentiating into neurons and glia. We further show that, when grown in vitro prior to grafting, human cells acquired new properties: Their proliferation was very limited, and they differentiated more rapidly. This study therefore provides new information about the use of these cells, which are a potential tool for both cellular and gene therapy.

Transplant therapy: recovery of function after spinal cord injury

Spinal cord injuries (SCI) result in devastating loss of function and altered sensation. Presently, victims of SCI have few remedies for the loss of motor function and the altered sensation often experienced subsequent to the injury. A goal in SCI research is to improve function in both acute and chronic injuries. Among the most successful interventions is the utilization of transplanted tissues toward improved recovery. The theory is that the transplanted tissue could (1) bridge the spinal lesion and provide chemical and/or mechanical guidance for host neurons to grow across the lesion, (2) bridge the spinal lesion and provide additional cellular elements to repair the damaged circuitry, (3) provide factors that would rescue neurons that would otherwise die and/or modulate neural circuits to improve function. A variety of tissues and cells have been added to the adult mammalian spinal cord to encourage restoration of function. These include Schwann cells, motor neurons, dorsal root ganglia, adrenal tissue, hybridomas, peripheral nerves, and fetal spinal cord (FSC) tissue en bloc or as disassociated cells. It is postulated that these tissues would rescue or replace injured adult neurons, which would then integrate or promote the regeneration of the spinal cord circuitry and restore function. In some instances, host-appropriate circuitry is supplied by the transplant and functional improvement is demonstrated. In this presentation, specific examples of recent work with transplanted tissue and cells that demonstrate improved behavioral outcome are presented. New recent work describing the in vitro propagation and characterization of human fetal spinal cord multipotential progenitor cells are also described in the context of a potential resource for transplantable cells. Additionally, data from transplantation experiments of human FSC cells into nonimmunosuppressed rat spinal cord are described, and the resultant improvements in behavioral outcome reported. Lastly, directions for future SCI research are proposed.

Cryopreserved GABAergic neurons in cultures of rat cerebral cortex and mesencephalon: a comparative morphometric study with anti-GABA antibodies

Blocks of embryonic rat cerebral cortex and mesencephalon were cryopreserved and stored for up to 1 year in liquid nitrogen at -196 degrees C with 7.5% dimethylsulfoxide (DMSO) as cryoprotectant. After thawing, these tissues were only mechanically dissociated and the cells were cultured for 2-7 weeks before immunocytochemical staining with anti-GABA (gamma-aminobutyric acid) antibodies. The freeze-stored GABA-immunoreactive (IR) mesencephalic neurons were compared, with computerized morphometry, to fresh mesencephalic cells and to their fresh and frozen cerebral cortical counterparts. A part of the cortical cells was treated with thienyl-phencyclidine (TCP) in order to assess the potential morphological effects of this neuroprotective agent upon these cortical neurons. Two types of GABA-IR neurons (small and large neuritic field cells) could be evidenced in both structures without any difference between fresh and frozen materials, but with significant quantitative morphological differences linked to their anatomical source. GABAergic phenotype is expressed similarly in fresh and frozen cultured neurons with intrinsically programmed morphological features and only minor influences of epigenetic factors. Small and large neuritic field GABA-IR neurons represent, respectively, local and long-range circuits of inhibition, strongly reminiscent of those described in vivo and which remain unchanged in culture even after freeze-storage.

Hypotensive and hypertensive effects of catecholamines intrathecally injected in anesthetized rats

The cardiovascular effects of catecholamines intrathecally (i.t.) injected at the T12-L1 level were analyzed in pentobarbital anesthetized rats. Volumes of injection were not greater than 3 microliters. Noradrenaline in doses ranging from 0.03 to 0.3 micrograms (i.t.) did not alter the mean blood pressure (MBP) while higher doses (1, 3 and 10 micrograms, i.t.) caused a dose-dependent increase in MBP. Adrenaline induced hypotensive effects at low doses (0.03-0.3 micrograms i.t.) and pressor effects at high doses (3 and 10 micrograms, i.t.). Neither adrenaline nor noradrenaline modified the heart rate. The pressor responses to both catecholamines were antagonized by the alpha 1-adrenoceptor blocker prazosin (0.05-1 microgram, i.t.) and by the selective alpha 1A-adrenoceptor antagonist 5-methyl urapidil (10 and 15 micrograms, i.t.). In contrast, these pressor effects were not modified by the alpha 1B-adrenoceptor antagonist chloroethylclonidine (90 micrograms i.t.). In animals pretreated with 1 microgram prazosin (i.t.), low doses of noradrenaline (0.03 and 0.1 microgram, i.t.) caused a hypotensive effect. Prazosin (1 microgram i.t.) failed to alter the hypotension caused by 0.1 microgram adrenaline. The hypotensive response induced by either 0.1 microgram noradrenaline (in the presence of prazosin) or 0.1 microgram adrenaline was blocked by the alpha 2-adrenoceptor antagonist yohimbine (1 mg/kg, i.v.), by the GABA-A antagonists bicuculline (3.2 micrograms, i.t.) and picrotoxin (2.7 micrograms, i.t.), and by the GABA-B antagonist 2-hydroxy saclofen (30 micrograms, i.t.). The glycine-receptor antagonist strychnine (25 micrograms, i.t.) did not modify the hypotension induced by either noradrenaline (in the presence of prazosin) or adrenaline. These findings suggest that in the low thoracolumbar spinal cord of pentobarbital-anesthetized rats, noradrenaline and adrenaline have excitatory as well as inhibitory effects on the control of the BP. The pressor responses of high doses of i.t. injected catecholamines could be mediated by the activation of spinal alpha 1A-adrenoceptors, although the participation of alpha 1B-adrenoceptors cannot be rule out entirely. The hypotensive responses induced by low doses of i.t. injected catecholamines seem to involve the activation of spinal alpha 2A-adrenoceptors and the stimulation of an inhibitory GABAergic neuron in the spinal cord.

Comparative distribution of GAD65 and GAD67 mRNAs and proteins in the rat spinal cord supports a differential regulation of these two glutamate decarboxylases in vivo

Gamma-aminobutyric acid (GABA) synthesis can result from the action of at least two glutamic acid decarboxylase (GAD) isoforms, GAD65 and GAD67, possibly involved in distinct mechanisms. We have made the hypothesis that GAD65 may respond to short-term changes and is present in neurons with a phasic activity, while GAD67 may rather provide GABA for the metabolic pool and for supporting tonic levels of synaptic transmission (Erlander et al.: Neuron 7:91-100, 1991; Feldblum et al.: J Neurosci Res 34:689-706, 1993). In the present work we have tested this hypothesis in the rat spinal cord where both types of activities have been identified. The correlation of GABA immunodetection with the distribution of GAD65 and GAD67 mRNAs and proteins has evinced in the dorsal horn a differential regulation of the two isoforms. In situ hybridization has revealed, in the dorsal horn, relatively higher levels of GAD67 mRNA than of GAD65, while immunodetection of the proteins demonstrated numerous punctate profiles with both GAD antisera. Reverse transcription-polymerase chain reaction (RT-PCR) data confirmed the abundance of the GAD67 transcripts compared to GAD65 in the rat spinal cord. In contrast, within the ventral horn, there was a greter number of GAD67-immunoreactive (IR) profiles mostly located around motoneurons. The paucity of GAD65 immunoreactivity in the ventral horn cannot be related to a different accessibility of the antigens to the epitopes since on the same section a dense GAD65 staining was detected in the dorsal horn. Hence, a number of biochemical and electrophysiological data support the concept of the involvement of glycine as the major inhibitory system within the ventral horn which may explain the low levels of GAD transcription in this region. The paucity of GAD65 in the ventral horn may also reflect a functional difference, suggesting a predominance of GAD67 in neurons under tonic activity. In the dorsal horn, where neurons with phasic and tonic firing patterns have been disclosed, GAD65 may, in addition, provide GABA for responses to short-term changes.

Primary dissociated cultures of human brainstem cells: a useful tool for their characterization and neuroprotection study

Dissociated cell cultures were prepared from brainstems of 5- to 10-week-old human fetuses. Catecholamine- as well as indolamine-containing cells were visualized using respectively dopamine (DA), noradrenaline (NA) and serotonin (5HT) as immunocytochemical markers. NA-, DA-, and 5HT-stained cells were characterized in the rhombencephalic cultures, representing respectively the fetal localization of the locus coeruleus and raphe nuclei. DA-stained cells were characterized in the mesencephalic cultures; these DA-cells originating from the substantia nigra presented morphological aspects different from the DA-rhombencephalic cells. Two types of GABA neurons and glial cells presenting glial fibrillary acidic protein (GFA-P) reactivity were also found in all the cultures. Two non-competitive N-methyl-D-aspartate antagonists, 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP) and cis-Pip/Me 1-[1-(2-thienyl)-2-methylcyclohexyl]piperidine (GK11) in enantiomeric form (-), have been investigated for survival on rhombencephalic cultured cells. The number of 5HT-cells was found to be greater in the treated cultures than in the control ones. This in vitro system appears to be a useful tool for the investigation of the development of central nervous system (CNS) cells as well as the study of neuroprotection.

Cryopreserved neuronal cells in long-term cultures of dissociated rat cerebral cortex: survival and morphometric characteristics as revealed by immunocytochemistry

Blocks of fresh tissue from embryonic rat cerebral cortex, dissociated either prior to or after freezing, were stored for up to 10 months in liquid nitrogen at -196 degrees C with 7% dimethylsulfoxide (DMSO) as cryoprotectant. Slow freezing and rapid thawing, a reduced medium volume and moderate elevation of both extracellular K+ (20 mM) and sera (20%) promoted survival of neurons (up to 7 weeks) on polylysine-coated glass coverslips. Although there was cell loss associated with freezing, the surviving cells developed morphological and immunocytochemical properties similar to those expressed by unfrozen cells when using anti-GFAP (glial fibrillary acidic protein), anti-NSE (neuron specific enolase) and anti-GABA (gamma-aminobutyric acid) antibodies. A comparative computer-aided analysis of the morphometric patterns of GABA-IR neurons allowed the individualization of two similar populations in both fresh and frozen controls. NSE- and GABA-immunoreactive (IR) cells were counted in frozen controls and thienyl-phencyclidine (TCP)-treated cultures. The latter yielded fewer cells whereas it was the opposite in fresh TCP-treated cultures. In view of these findings, a detailed analysis of the effects of both neuroprotective and neurotoxic agents on frozen cells is undertaken before considering that cryopreservation might be a suitable storage method for clinical trials of neuron grafting.

Neuroprotective effect of N-methyl-D-aspartate non-competitive antagonists (arylcyclohexylamine derivatives) on human cultured spinal cord cells

The non-competitive N-methyl-D-aspartate antagonist cis-Pip/Me 1-[1-(2-thienyl)-2-methyl-cyclohexyl] piperidine (GK11) either in racemic(+/-) or (-) enantiomeric form has been investigated on survival of human fetal spinal cord cells in culture. The treated cultured cells were processed for immunocytochemical detection of GABA at different time intervals ranging from 3 to 27 weeks. The number of GABA-stained cells was found to be greater in the treated cultures than in the control ones. The qualitative and quantitative morphological features of both control and treated cells were analysed by computer-assisted methods which allowed us to individualize three different populations: (1) all control and treated small neuritic field neurons, (2) young control and old treated large neuritic field neurons and (3) old control neurons with large neuritic fields.