We evaluated the teratoma-forming propensity of secondary neurospheres (SNS) generated from 36 mouse induced pluripotent stem (iPS) cell lines derived in 11 different ways. Teratoma-formation of SNS from embryonic fibroblast-derived iPS cells was similar to that of SNS from embryonic stem (ES) cells. In contrast, SNS from iPS cells derived from different adult tissues varied substantially in their teratoma-forming propensity, which correlated with the persistence of undifferentiated cells.

Once their safety is confirmed, human-induced pluripotent stem cells (hiPSCs), which do not entail ethical concerns, may become a preferred cell source for regenerative medicine. Here, we investigated the therapeutic potential of transplanting hiPSC-derived neurospheres (hiPSC-NSs) into nonobese diabetic (NOD)-severe combined immunodeficient (SCID) mice to treat spinal cord injury (SCI). For this, we used a hiPSC clone (201B7), established by transducing four reprogramming factors (Oct3/4, Sox2, Klf4, and cMyc) into adult human fibroblasts. Grafted hiPSC-NSs survived, migrated, and differentiated into the three major neural lineages (neurons, astrocytes, and oligodendrocytes) within the injured spinal cord. They showed both cell-autonomous and noncellautonomous (trophic) effects, including synapse formation between hiPSC-NS-derived neurons and host mouse neurons, expression of neurotrophic factors, angiogenesis, axonal regrowth, and increased amounts of myelin in the injured area. These positive effects resulted in significantly better functional recovery compared with vehicle-treated control animals, and the recovery persisted through the end of the observation period, 112 d post-SCI. No tumor formation was observed in the hiPSC-NS-grafted mice. These findings suggest that hiPSCs give rise to neural stem/progenitor cells that support improved function post-SCI and are a promising cell source for its treatment.stem-cell-based medicine | cell transplantation | neurotrauma | synaptic connection S tem-cell-based approaches, such as the transplantation of neural stem/progenitor cells (NS/PCs), are promising sources of therapies for various central nervous system disorders (1-3). Previous studies reported functional recovery after transplantation of NS/PCs into the injured spinal cord of rodents and nonhuman primates (4-9). Furthermore, recent studies revealed that embryonic stem cells (ESCs) can generate neural cells including NS/PCs (10-12) and oligodendrocyte precursor cells (OPCs) (13,14). Therefore, human ESC-based therapies are moving out of the laboratory and into clinical treatments for spinal cord injury (SCI) (12,13,15). However, the use of human ESC-based therapies is complicated by ethical concerns in certain countries. To avoid the problems associated with ESCs, we previously established induced pluripotent stem cells (iPSCs) from mouse fibroblasts (16, 17) and confirmed the therapeutic potential of iPSC-derived neurospheres (iPSC-NSs) for treating SCI in animal models (18).Here, aiming at human iPSC-based therapies for SCI patients, we examined the therapeutic potential of human iPSC-NSs by transplanting them into nonobese diabetic severe combined immunodeficient (NOD-SCID) SCI model mice. We used a clone from human iPSCs (hiPSCs) that we established from adult human dermal fibroblasts by the retroviral transduction of four reprogramming factors; for the clone used in this study, 201B7, the factors were Oct3/4, Sox2, Klf4, and c-Myc (19). These grafted hiPSC-NSs survived, migrated, and differentiated in...

Alzheimer's disease (AD) is the most common form of age-related dementia, characterized by progressive memory loss and cognitive disturbance. Mutations of presenilin 1 (PS1) and presenilin 2 (PS2) are causative factors for autosomal-dominant early-onset familial AD (FAD). Induced pluripotent stem cell (iPSC) technology can be used to model human disorders and provide novel opportunities to study cellular mechanisms and establish therapeutic strategies against various diseases, including neurodegenerative diseases. Here we generate iPSCs from fibroblasts of FAD patients with mutations in PS1 (A246E) and PS2 (N141I), and characterize the differentiation of these cells into neurons. We find that FAD-iPSC-derived differentiated neurons have increased amyloid β42 secretion, recapitulating the molecular pathogenesis of mutant presenilins. Furthermore, secretion of amyloid β42 from these neurons sharply responds to γ-secretase inhibitors and modulators, indicating the potential for identification and validation of candidate drugs. Our findings demonstrate that the FAD-iPSC-derived neuron is a valid model of AD and provides an innovative strategy for the study of age-related neurodegenerative diseases.

Various types of induced pluripotent stem (iPS) cells have been established by different methods, and each type exhibits different biological properties. Before iPS cell-based clinical applications can be initiated, detailed evaluations of the cells, including their differentiation potentials and tumorigenic activities in different contexts, should be investigated to establish their safety and effectiveness for cell transplantation therapies. Here we show the directed neural differentiation of murine iPS cells and examine their therapeutic potential in a mouse spinal cord injury (SCI) model. "Safe" iPS-derived neurospheres, which had been pre-evaluated as nontumorigenic by their transplantation into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse brain, produced electrophysiologically functional neurons, astrocytes, and oligodendrocytes in vitro. Furthermore, when the safe iPS-derived neurospheres were transplanted into the spinal cord 9 d after contusive injury, they differentiated into all three neural lineages without forming teratomas or other tumors. They also participated in remyelination and induced the axonal regrowth of host 5HT + serotonergic fibers, promoting locomotor function recovery. However, the transplantation of iPSderived neurospheres pre-evaluated as "unsafe" showed robust teratoma formation and sudden locomotor functional loss after functional recovery in the SCI model. These findings suggest that preevaluated safe iPS clone-derived neural stem/progenitor cells may be a promising cell source for transplantation therapy for SCI.neural stem/progenitor cell | cell transplantation | regenerative medicine | remyelination | axonal regrowth