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Artificial tissues constructed from therapeutic cells offer a promising approach for improving the treatment of severe peripheral nerve injuries. In this study the effectiveness of using CTX0E03, a conditionally immortalised human neural stem cell line, as a source of allogeneic cells for constructing living artificial nerve repair tissue was tested. CTX0E03 cells were differentiated then combined with collagen to form engineered neural tissue (EngNT-CTX), stable aligned sheets of cellular hydrogel. EngNT-CTX sheets were delivered within collagen tubes to repair a 12 mm sciatic nerve injury model in athymic nude rats. Autologous nerve grafts (autografts) and empty tubes were used for comparison. After 8 weeks functional repair was assessed using electrophysiology. Further, detailed histological and electron microscopic analysis of the repaired nerves was performed. Results indicated that EngNT-CTX supported growth of neurites and vasculature through the injury site and facilitated reinnervation of the target muscle. These findings indicate for the first time that a clinically validated allogeneic neural stem cell line can be used to construct EngNT. This provides a potential ‘off the shelf’ tissue engineering solution for the treatment of nerve injury, overcoming the limitations associated with nerve autografts or the reliance on autologous cells for populating repair constructs.

The method of delivery of stem cells is a major factor to consider in the design of clinical trials of cell therapy. Different methods of delivery will be associated with different risks to the patient, and may also be associated with different potential for benefit. Current approaches are partly informed by the routes selected for study in animal models of focal ischaemia and CNS transplantation, but there has been little work comparing the efficacy of different routes of administration. Direct intraparenchymal delivery of cells has been employed in several preliminary clinical trials, and data on the safety of this approach are reviewed.

Applicants in Europe are left with few options for the patent protection of hES cell-related technology.

Two experiments were conducted with Sprague-Dawley rats, chronically implanted with medial septal stimulating and subicular recording electrodes, to test the hypothesis that low-frequency electrical stimulation of the septal area, driving the hippocampal theta rhythm, has frequency-dependent proactive efects on behavior: specifically, that theta-driving stimulation at 7.5 Hz gives rise to tolerance for subsequent frustrative nonreward, whereas stimulation at 7.7 Hz sensitizes the animal to this event. After a 10-day stimulation regime (fifteen 6-sec stimulation trains at a 30-sec intertrain interval daily; 7.5 Hz in Experiment 1, 7.7 Hz in Experiment 2), rats were trained to run in a straight alley for food reward at 1 trial/day for 16 days on either a continuous reinforcement (CRF) or a partial reinforcement (PRF) reinforcement schedule followed by extinction; implanted controls were not stimulated but were otherwise treated identically. As predicted by the hypothesis, the partial reinforcement extinction effect (PREE; i.e., greater resistance to extinction after PRF than after CRF training) was proactively reduced by 7.5-Hz stimulation, owing to lowered resistance to extinction in the stimulated PRF-trained animals relative to their nonstimulated controls; whereas, again as predicted, the PREE was increased by 7.7-Hz stimulation, owing both to increased resistance to extinction in the stimulated PRF condition and reduced resistance to extinction in the stimulated CRF condition relative to the respective non-stimulated control groups. Thus the proactive behavioral effects of 7.5- and 7.7-Hz stimulation were opposite in sign, dependent in both cases upon the schedule of reinforcement encountered subsequent to stimulation, and consistent, respectively, with stimulation-induced tolerance for nonreward (7.5 Hz) or sensitization of the response to nonreward (7.7 Hz).

Two experiments were run in which rats were rewarded with food for running in a straight alley at one trial a day, followed by extinction of the running response. During acquisition of the response, reward was delivered either on a continuous reinforcement (CRF) or on a quasirandom 50% partial reinforcement (PRF) schedule. The groups given PRF were more resistant to extinction than those given CRF, the well-known partial reinforcement extinction effect. In Experiment 1 different groups of rats were injected during acquisition only with 1, 5 or 10 mg/kg of the benzodiazepine antagonist, RO 15-1788, or with placebo. In Experiment 2, 5 mg/kg RO 15-1788 or placebo were administered in a full cross-over design during acquisition, extinction or both. At the end of Experiment 2 only [3H]-flunitrazepam binding was measured in either the presence or absence of added gamma-aminobutyrate (GABA) in homogenates of hippocampi dissected from the animals that had received behavioural training. The drug affected running speeds during both acquisition and extinction in different ways depending upon the schedule of reinforcement (CRF or PRF) and also gave rise to enhanced GABA stimulation of [3H]-flunitrazepam binding. The results are discussed in relation to the hypothesis that the neurochemical pathways by which reinforcement schedules modify behaviour include a step influenced by benzodiazepine receptors.