Stroke is a major cause of death and disability, with very limited treatment option. Cell-based therapies have emerged as potential treatments for stroke. Indeed, studies have shown that transplantation of neural stem cells (NSCs) exerts functional benefits in stroke models. However, graft survival and integration with the host remain pressing concerns with cell-based treatments. The current study set out to investigate those very issues using a human NSC line, NSI-566RSC, in a rat model of ischemic stroke induced by transient occlusion of the middle cerebral artery. Seven days after stroke surgery, those animals that showed significant motor and neurological impairments were randomly assigned to receive NSI-566RSC intracerebral transplants at two sites within the striatum at three different doses: group A (0 cells/µl), group B (5,000 cells/µl), group C (10,000 cells/µl), and group D (20,000 cells/µl). Weekly behavioral tests, starting at seven days and continued up to 8 weeks after transplantation, revealed dose-dependent recovery from both motor and neurological deficits in transplanted stroke animals. Eight weeks after cell transplantation, immunohistochemical investigations via hematoxylin and eosin staining revealed infarct size was similar across all groups. To identify the cell graft, and estimate volume, immunohistochemistry was performed using two human-specific antibodies: one to detect all human nuclei (HuNu), and another to detect human neuron-specific enolase (hNSE). Surviving cell grafts were confirmed in 10/10 animals of group B, 9/10 group C, and 9/10 in group D. hNSE and HuNu staining revealed similar graft volume estimates in transplanted stroke animals. hNSE-immunoreactive fibers were also present within the corpus callosum, coursing in parallel with host tracts, suggesting a propensity to follow established neuroanatomical features. Despite absence of reduction in infarct volume, NSI-566RSC transplantation produced behavioral improvements possibly via robust engraftment and neuronal differentiation, supporting the use of this NSC line for stroke therapy.

Clinical management of primary and secondary central nervous system (CNS) malignancies frequently includes radiotherapy to forestall tumor growth and recurrence after surgical resection. While cranial radiotherapy remains beneficial, adult and pediatric brain tumor survivors suffer from a wide range of debilitating and progressive cognitive deficits. Although this has been recognized as a significant problem for decades, there remains no clinical recourse for the unintended neurocognitive sequelae associated with these types of cancer treatments. In previous work, multiple mechanisms have been identified that contribute to radiation-induced cognitive dysfunction, including the inhibition of neurogenesis caused by the depletion of radiosensitive populations of stem and progenitor cells in the hippocampus. To explore the potential neuroprotective properties of a pro-neurogenic compound NSI-189, Long-Evans rats were subjected to a clinically relevant fractionated irradiation protocol followed by four weeks of NSI-189 administered daily by oral gavage. Animals were then subjected to five different behavioral tasks followed by an analysis of neurogenesis, hippocampal volume and neuroinflammation. Irradiated cohorts manifested significant behavioral decrements on all four spontaneous exploration tasks. Importantly, NSI-189 treatment resulted in significantly improved performance in four of these tasks: novel place recognition, novel object recognition, object in place and temporal order. In addition, there was a trend of improved performance in the contextual phase of the fear conditioning task. Importantly, enhanced cognition in the NSI-189-treated cohort was found to persist one month after the cessation of drug treatment. These neurocognitive benefits of NSI-189 coincided with a significant increase in neurogenesis and a significant decrease in the numbers of activated microglia compared to the irradiated cohort that was given vehicle alone. The foregoing changes were not accompanied by major changes in hippocampal volume. These data demonstrate that oral administration of a pro-neurogenic compound exhibiting anti-inflammatory indications could impart long-term neurocognitive benefits in the irradiated brain.

Enhancing neurogenesis may be a powerful stroke therapy. Here, we tested in a rat model of ischemic stroke the beneficial effects of NSI‐189, an orally active, new molecular entity (mol. wt. 366) with enhanced neurogenic activity, and indicated as an anti‐depressant drug in a clinical trial (Fava et al., 2015, Molecular Psychiatry, DOI: 10.1038/mp.2015.178) and being tested in a Phase 2 efficacy trial (ClinicalTrials.gov, 2016, ClinicalTrials.gov Identifier: NCT02695472) for treatment of major depression. Oral administration of NSI‐189 in adult Sprague–Dawley rats starting at 6 hr after middle cerebral artery occlusion, and daily thereafter over the next 12 weeks resulted in significant amelioration of stroke‐induced motor and neurological deficits, which was maintained up to 24 weeks post‐stroke. Histopathological assessment of stroke brains from NSI‐189‐treated animals revealed significant increments in neurite outgrowth as evidenced by MAP2 immunoreactivity that was prominently detected in the hippocampus and partially in the cortex. These results suggest NSI‐189 actively stimulated remodeling of the stroke brain. Parallel in vitro studies further probed this remodeling process and demonstrated that oxygen glucose deprivation and reperfusion (OGD/R) initiated typical cell death processes, which were reversed by NSI‐189 treatment characterized by significant attenuation of OGD/R‐mediated hippocampal cell death and increased Ki67 and MAP2 expression, coupled with upregulation of neurogenic factors such as BDNF and SCF. These findings support the use of oral NSI‐189 as a therapeutic agent well beyond the initial 6‐hr time window to accelerate and enhance the overall functional improvement in the initial 6 months post stroke.

While peripheral neuropathy is the most common complication of long-term diabetes, cognitive deficits associated with encephalopathy and myelopathy also occur. Diabetes is a risk factor for Alzheimer disease (AD) and increases the risk of progression from mild cognitive impairment to AD. The only current recommendation for preventing or slowing the progression of peripheral neuropathy is to maintain close glycemic control, while there is no recommendation for central nervous system disorders. NSI-189 is a new chemical entity that when orally administered promotes neurogenesis in the adult hippocampus, increases hippocampal volume, enhances synaptic plasticity, and reduces cognitive dysfunction. To establish the potential for impact on peripheral neuropathy, we first showed that NSI-189 enhances neurite outgrowth and mitochondrial functions in cultured adult rat primary sensory neurons. Oral delivery of NSI-189 to murine models of type 1 (female) and type 2 (male) diabetes prevented multiple functional and structural indices of small and large fiber peripheral neuropathy, increased hippocampal neurogenesis, synaptic markers and volume, and protected long-term memory. NSI-189 also halted progression of established peripheral and central neuropathy. NSI-189, which is currently in clinical trials for treatment of major depressive disorder, offers the opportunity for the development of a single therapeutic agent against multiple indices of central and peripheral neuropathy.

Aims. Mitochondrial dysfunction contributes to many forms of peripheral and central nervous system degeneration. Therapies that protect mitochondrial number and function have the potential to impact the progression of conditions such as diabetic neuropathy. We therefore assessed indices of mitochondrial function in dorsal root ganglia (DRG) and brain cortex of the Zucker diabetic fatty (ZDF) rat model of type 2 diabetes and tested the therapeutic impact of a neurogenic compound, NSI-189, on both mitochondrial function and indices of peripheral and central neurological dysfunction. Materials and Methods. ZDF rats were maintained for 16 weeks of untreated diabetes before the start of oral treatment with NSI-189 for an additional 16 weeks. Nerve conduction velocity, sensitivity to tactile and thermal stimuli, and behavioral assays of cognitive function were assessed monthly. AMP-activated protein kinase (AMPK) phosphorylation, mitochondrial protein levels, and respiratory complex activities were assessed in the DRG and brain cortex after 16 weeks of treatment with NSI-189. Results. Treatment with NSI-189 selectively elevated the expression of protein subunits of complexes III and V and activities of respiratory complexes I and IV in the brain cortex, and this was accompanied by amelioration of impaired memory function and plasticity. In the sensory ganglia of ZDF rats, loss of AMPK activity was ameliorated by NSI-189, and this was accompanied by reversal of multiple indices of peripheral neuropathy. Conclusions. Efficacy of NSI-189 against dysfunction of the CNS and PNS function in type 2 diabetic rats was accompanied by improvement of mitochondrial function. NSI-189 exhibited actions at different levels of mitochondrial regulation in central and peripheral tissues.