Human-Induced Pluripotent Stem Cell-Derived Neural Progenitor Cells Showed Neuronal Differentiation, Neurite Extension, and Formation of Synaptic Structures in Rodent Ischemic Stroke Brains.

Ischemic stroke is a major cerebrovascular disease with high morbidity and mortality rates; however, effective treatments for ischemic stroke-related neurological dysfunction have yet to be developed. In this study, we generated neural progenitor cells from human leukocyte antigen major loci gene-homozygous-induced pluripotent stem cells (hiPSC-NPCs) and evaluated their therapeutic effects against ischemic stroke. hiPSC-NPCs were intracerebrally transplanted into rat ischemic brains produced by transient middle cerebral artery occlusion at either the subacute or acute stage, and their in vivo survival, differentiation, and efficacy for functional improvement in neurological dysfunction were evaluated. hiPSC-NPCs were histologically identified in host brain tissues and showed neuronal differentiation into vGLUT-positive glutamatergic neurons, extended neurites into both the ipsilateral infarct and contralateral healthy hemispheres, and synaptic structures formed 12 weeks after both acute and subacute stage transplantation. They also improved neurological function when transplanted at the subacute stage with γ-secretase inhibitor pretreatment. However, their effects were modest and not significant and showed a possible risk of cells remaining in their undifferentiated and immature status in acute-stage transplantation. These results suggest that hiPSC-NPCs show cell replacement effects in ischemic stroke-damaged neural tissues, but their efficacy is insufficient for neurological functional improvement after acute or subacute transplantation. Further optimization of cell preparation methods and the timing of transplantation is required to balance the efficacy and safety of hiPSC-NPC transplantation.

Evaluation of the susceptibility of neurons and neural stem/progenitor cells derived from human induced pluripotent stem cells to anticancer drugs.

Various chemicals, including pharmaceuticals, can induce acute or delayed neurotoxicity in humans. Because isolation of human primary neurons is extremely difficult, toxicity tests for these agents have been performed using in vivo or in vitro models. Human induced pluripotent stem cells (hiPSCs) can be used to establish hiPSC-derived neural stem/progenitor cells (hiPSC-NSPCs), which can then be used to obtain hiPSC-neurons. In this study, we differentiated hiPSC-NSPCs into neurons and evaluated the susceptibility of hiPSC-neurons and parental hiPSC-NSPCs to anticancer drugs in vitro by ATP assay and immunocytostaining. The hiPSC-neurons were more resistant to anticancer drugs than the parental hiPSC-NSPCs. In the toxicity tests, high-dose cisplatin reduced the levels of ELAVL3/4, a neuronal marker, in the hiPSC-neurons. These results suggest that our methodology is potentially applicable for efficient determination of the toxicity of any drug to hiPSC-neurons.

Small-scale screening of anticancer drugs acting specifically on neural stem/progenitor cells derived from human-induced pluripotent stem cells using a time-course cytotoxicity test.

Since the development of human-induced pluripotent stem cells (hiPSCs), various types of hiPSC-derived cells have been established for regenerative medicine and drug development. Neural stem/progenitor cells (NSPCs) derived from hiPSCs (hiPSC-NSPCs) have shown benefits for regenerative therapy of the central nervous system. However, owing to their intrinsic proliferative potential, therapies using transplanted hiPSC-NSPCs carry an inherent risk of undesired growth in vivo. Therefore, it is important to find cytotoxic drugs that can specifically target overproliferative transplanted hiPSC-NSPCs without damaging the intrinsic in vivo stem-cell system. Here, we examined the chemosensitivity of hiPSC-NSPCs and human neural tissue-derived NSPCs (hN-NSPCs) to the general anticancer drugs cisplatin, etoposide, mercaptopurine, and methotrexate. A time-course analysis of neurospheres in a microsphere array identified cisplatin and etoposide as fast-acting drugs, and mercaptopurine and methotrexate as slow-acting drugs. Notably, the slow-acting drugs were eventually cytotoxic to hiPSC-NSPCs but not to hN-NSPCs, a phenomenon not evident in the conventional endpoint assay on day 2 of treatment. Our results indicate that slow-acting drugs can distinguish hiPSC-NSPCs from hN-NSPCs and may provide an effective backup safety measure in stem-cell transplant therapies.

Systemic Intravenous Adoptive Transfer of Autologous Lymphokine-activated αß T-Cells Improves Temozolomide-induced Lymphopenia in Patients with Glioma.

In this clinical study, we investigated the safety and clinical usefulness of systemic adoptive immunotherapy using autologous lymphokine-activated αß T-cells (αß T-cells), combined with standard therapies, in patients with malignant brain tumors. Twenty-three patients with different malignant brain tumors, consisting of 14 treated with temozolomide (TMZ group) and 9 treated without temozolomide (non-TMZ group), received systemic intravenous injections of αß T-cells (mean=10.4 injections/patient for the TMZ group, and 4.78 for the non-TMZ group). No significant adverse effects associated with the αß T-cell injection were observed, and the total lymphocyte count (TLC) improved significantly in the TMZ group after five injections. Furthermore, CD8-positive or T-cell receptor V gamma -positive cells were increased with TLC in three patients with glioblastoma multiforme. These findings suggest that systemic αß T-cell immunotherapy is well tolerated, and may help restore an impaired and imbalanced T-cell immune status, and temozolomide- and/or radiotherapy-induced lymphopenia. Future prospective study is needed to clarify the clinical merits of this immunotherapy.

Establishment of Human Neural Progenitor Cells from Human Induced Pluripotent Stem Cells with Diverse Tissue Origins.

Human neural progenitor cells (hNPCs) have previously been generated from limited numbers of human induced pluripotent stem cell (hiPSC) clones. Here, 21 hiPSC clones derived from human dermal fibroblasts, cord blood cells, and peripheral blood mononuclear cells were differentiated using two neural induction methods, an embryoid body (EB) formation-based method and an EB formation method using dual SMAD inhibitors (dSMADi). Our results showed that expandable hNPCs could be generated from hiPSC clones with diverse somatic tissue origins. The established hNPCs exhibited a mid/hindbrain-type neural identity and uniform expression of neural progenitor genes.