Restoration of spatial memory dysfunction of human APP transgenic mice by transplantation of neuronal precursors derived from human iPS cells

Cellular and molecular mechanisms of the restoration of human APP transgenic mouse cognitive dysfunction after transplant of human iPS cell-derived neural cells

Cholinergic neuronal loss is a common finding in patients with Alzheimer's disease (AD) and AD model mice. We previously transplanted neurons derived from human induced pluripotent stem (iPS) cells into the hippocampus of human amyloid precursor protein transgenic AD model mice. In the present study, we examined the cellular and molecular mechanisms involved in the alleviation of cognitive dysfunction in transplanted mice. After transplant, mice showed improvement in cognitive function, confirming our previous findings. Human choline acetyltransferase (ChAT)-positive cholinergic neurons were distributed throughout the cortex of the grafted mice. Human and mouse ChAT-positive neurons and alpha7 nicotinic acetylcholine receptor (α7nAChR)-positive neurons were significantly increased in the cortex and hippocampus of the grafted mice compared with the vehicle-injected mice. In addition, human and mouse vesicular GABA transporter (VGAT)-positive neurons were located mainly in the hippocampus and, though the number was small, human VGAT-positive neurons were observed in the cortex. In the grafted mouse cortex, the number of GABA receptor (GABAR)-positive neurons of both human origin and mouse origin were significantly increased compared with those in the vehicle-injected mouse cortex. The α7nAChR-positive and GABAR-positive neurons expressed phosphorylated Akt and c-fos in the cortex, suggesting that these receptor-expressing neurons were possibly activated by the neurotransmitters secreted from the grafted neurons. Collectively, the grafted and host neurons may form positive feedback loops via neurotransmitter secretion in both the cerebral cortex and hippocampus, leading to alleviation of cognitive dysfunction in dementia model mice.

Effects of stem cell transplantation on cognitive decline in animal models of Alzheimer's disease: A systematic review and meta-analysis

Alzheimer’s disease (AD), an irreversible progressive neurodegenerative disease, causes characteristic cognitive impairment, and no curative treatments are currently available. Stem cell transplantation offers a powerful tool for the treatment of AD. We conducted a systematic review and meta-analysis of data from controlled studies to study the impact of stem cell biology and experimental design on learning and memory function following stem cell transplantation in animal models of AD. A total of 58 eligible controlled studies were included by searching PubMed, EMBASE, and Web of Science up to April 13, 2015. Meta-analysis showed that stem cell transplantation could promote both learning and memory recovery. Stratified meta-analysis was used to explore the influence of the potential factors on the estimated effect size, and meta-regression analyses were undertaken to explore the sources of heterogeneity for learning and memory function. Publication bias was assessed using funnel plots and Egger’s test. The present review reinforces the evidence supporting stem cell transplantation in experimental AD. However, it highlights areas that require well-designed and well-reported animal studies.

Neuro-peptide treatment with Cerebrolysin improves the survival of neural stem cell grafts in an APP transgenic model of Alzheimer disease

Neural stem cells (NSCs) have been considered as potential therapy in Alzheimer's disease (AD) but their use is hampered by the poor survival of grafted cells. Supply of neurotrophic factors to the grafted cells has been proposed as a way to augment survival of the stem cells. In this context, we investigated the utility of Cerebrolysin (CBL), a peptidergic mixture with neurotrophic-like properties, as an adjunct to stem cell therapy in an APP transgenic (tg) model of AD. We grafted murine NSCs into the hippocampus of non-tg and APP tg that were treated systemically with CBL and analyzed after 1, 3, 6 and 9months post grafting. Compared to vehicle-treated non-tg mice, in the vehicle-treated APP tg mice there was considerable reduction in the survival of the grafted NSCs. Whereas, CBL treatment enhanced the survival of NSCs in both non-tg and APP tg with the majority of the surviving NSCs remaining as neuroblasts. The NSCs of the CBL treated mice displayed reduced numbers of caspase-3 and TUNEL positive cells and increased brain derived neurotrophic factor (BDNF) and furin immunoreactivity. These results suggest that CBL might protect grafted NSCs and as such be a potential adjuvant therapy when combined with grafting.

The promise of stem cells in the therapy of Alzheimer's disease

Alzheimer’s disease (AD), a common neurodegenerative disorder associated with gradually to dramatic neuronal death, synaptic loss and dementia, is considered to be one of the most obscure and intractable brain disorders in medicine. Currently, there is no therapy clinically available to induce marked symptomatic relief in AD patients. In recent years, the proof-of-concept studies using stem cell-based approaches in transgenic AD animal models provide new hope to develop stem cell-based therapies for the effective treatment of AD. The degeneration of basal forebrain cholinergic neurons (BFCNs) and the resultant cholinergic abnormalities in the brain contribute substantially to the cognitive decline of AD patients. The approches using stem cell-derived BFCNs as donor cells need to be developed, and to provide proof of principle that this subtype-specific neurons can induce functional recovery of AD animal models. With the continuous scientific advances in both academic and industrial fields, the potentials of stem cells in cellular neuroprotection and cell replacement in vivo have been elucidated, and stem cell-based therapy for repairing degenerative brains of AD is promising.

Retinoic acid as a therapeutic option in Alzheimer's disease: a focus on cholinergic restoration

Retinoic acid is a potent cell differentiating factor, which through its nuclear receptors affects a vast range of promoter sites in brain neuronal and glial cells in every step of embryonic and postnatal life. Its capacities, facilitating maturation of neurotransmitter phenotype in different groups of neurons, pave the way for its application as a potential therapeutic agent in neurodegenerative diseases including Alzheimer's disease. Retinoic acid was found to exert particularly strong enhancing effects on acetylcholine transmitter functions in brain cholinergic neurons, loss of which is tightly linked to the development of cognitive and memory deficits in course of different cholinergic encephalopathies. Here, we review cholinotrophic properties of retinoic acid and its derivatives, which may justify their application in the management of Alzheimer's disease and the related neurodegenerative conditions.