Regenerative Medicine for Spinal Cord Injury Using Induced Pluripotent Stem Cells.

Spinal cord injury (SCI) is a devastating injury that causes permanent neurological dysfunction. To develop a new treatment strategy for SCI, a clinical trial of transplantation of human-induced pluripotent stem cell-derived neural precursor cells (NPCs) in patients in the subacute phase of SCI was recently initiated. The formation of synaptic connections with host neural tissues is one of the therapeutic mechanisms of cell transplantation, and this beneficial efficacy has been directly demonstrated using a chemogenetic tool. This research focuses on the establishment of cell therapy for chronic SCI, which is more challenging owing to cavity and scar formation. Thus, neurogenic NPC transplantation is more effective in forming functional synapses with the host neurons. Furthermore, combinatory rehabilitation therapy is useful to enhance the efficacy of this strategy, and a valid rehabilitative training program has been established for SCI animal models that received NPC transplantation in the chronic phase. Therefore, the use of regenerative medicine for chronic SCI is expected to increase.

Neurorehabilitation using a voluntary driven exoskeletal robot improves trunk function in patients with chronic spinal cord injury: a single-arm study.

Body weight-supported treadmill training with the voluntary driven exoskeleton (VDE-BWSTT) has been shown to improve the gait function of patients with chronic spinal cord injury. However, little is known whether VDE-BWSTT can effectively improve the trunk function of patients with chronic spinal cord injury. In this open-label, single-arm study, nine patients with chronic spinal cord injury at the cervical or thoracic level (six males and three females, aged 37.8 ± 15.6 years, and time since injury 51.1 ± 31.8 months) who underwent outpatient VDE-BWSTT training program at Keio University Hospital, Japan from September 2017 to March 2019 were included. All patients underwent twenty 60-minute gait training sessions using VDE. Trunk muscular strength, i.e., the maximum force against which patient could maintain a sitting posture without any support, was evaluated in four directions: anterior, posterior, and lateral (right and left) after 10 and 20 training sessions. After intervention, lateral muscular strength significantly improved. In addition, a significant positive correlation was detected between the change in lateral trunk muscular strength after 20 training sessions relative to baseline and gait speed. The change in trunk muscular strength after 20 training sessions relative to baseline was greatly correlated with patient age. This suggests that older adult patients with chronic spinal cord injury achieved a greater improvement in trunk muscle strength following VDE-BWSTT. All these findings suggest that VDE-BWSTT can improve the trunk function of patients with chronic spinal cord injury and the effect might be greater in older adult patients. The study was approved by the Keio University of Medicine Ethics Committee (IRB No. 20150355-3) on September 26, 2017.

Internet survey on factors associated with care-seeking behaviours of people with chronic musculoskeletal pain in Japan.

Purpose: Many people with chronic musculoskeletal pain (CMP) seek healthcare from conventional and complementary and alternative medicine. However, treatment/therapy is not always adequate, patients often change healthcare providers, and some patients are left untreated. This study clarified care-seeking behaviours and explored factors behind the behaviours in people with CMP. Methods: Using a Japanese cross-sectional online survey, participants aged ≥ 20 years with non-cancer/fracture CMP lasting for ≥ 6 months and presenting ≤1 month, interfering with daily living activities and/or work were enrolled. We summarized and analysed the characteristics and factors associated with choice of healthcare providers; information on socio-demographics, including employment; ability to use healthcare, including income; and need for healthcare, including pain intensity, using a logistic regression model. Results: Among the 9105 respondents, 24.5% consulted physicians, 18.3% complementary and alternative medicine practitioners, and 57.2% were untreated. More respondents who had moderate-severe pain visited physician, more regularly employed and with high income visited complementary and alternative medicine, and less respondents who had moderate-severe pain were untreated. These were found to be associated with the respective healthcare use versus untreated. Conclusions: People with severe conditions, higher income and regular employment, and less severe conditions have visited physicians, complementary and alternative medicine practitioners and none, respectively. By applying this result at each type of healthcare provider, it may be possible to treat patients more appropriately.

Influence of body weight-supported treadmill training with voluntary-driven exoskeleton on the quality of life of persons with chronic spinal cord injury: a pilot study.

The aim of this study was to investigate whether body weight-supported treadmill training with voluntary-driven exoskeleton body weight-supported treadmill training (VDE-BWSTT) improves the quality of life (QOL) of persons with chronic spinal cord injury (SCI). Nineteen individuals with chronic SCI with walking limitation underwent a total of 20 sessions of VDE-BWSTT using the hybrid assistant limb. The QOL was measured using the Short Form-36v2 (SF-36v2) questionnaire at preintervention and postintervention. The Walking Index for SCI-II (WISCI-II), Functional Independence Measure (FIM) motor score, and Neuropathic Pain Symptom Inventory (NPSI) self-questionnaire were also administered/completed. In SF-36v2, the mean values of all subscales in our participants were lower than those in healthy individuals. None of the measures showed significant improvement, even in individuals with some residual walking ability (baseline WISCI-II score of 6 or higher). In the correlation analysis between the baselines WISCI-II, FIM, or NPSI values and the mean SF-36v2 subscale changes throughout the training, the baseline FIM motor score was positively correlated with the mean changes in Role Emotional and Mental Health. In addition, NPSI was negatively correlated with the mean change in Vitality and Mental Health. In our protocol, although VDE-BWSTT did not improve the QOL of persons with chronic SCI, those with higher functional independence or lower pain at preintervention likely improved. Further study with combination of task-specific training or pain-targeting treatment with more patients should be considered to more effectively improve their QOL.

First-in-human clinical trial of transplantation of iPSC-derived NS/PCs in subacute complete spinal cord injury: Study protocol.

INTRODUCTION: Our group has conducted extensive basic and preclinical studies of the use of human induced pluripotent cell (iPSC)-derived neural stem/progenitor cell (hiPSC-NS/PC) grafts in models of spinal cord injury (SCI). Evidence from animal experiments suggests this approach is safe and effective. We are preparing to initiate a first-in-human clinical study of hiPSC-NS/PC transplantation in subacute SCI. SETTING: NS/PCs were prepared at a Good Manufacturing Practice-grade cell processing facility at Osaka National Hospital using a clinical-grade integration-free hiPSC line established by the iPSC Stock Project organized by the Kyoto University Center for iPS Cell Research and Application. After performing all quality checks, the long-term safety and efficacy of cells were confirmed using immunodeficient mouse models. METHODS: The forthcoming clinical study uses an open-label, single-arm design. The initial follow-up period is 1 year. The primary objective is to assess the safety of hiPSC-NS/PC transplantation in patients with subacute SCI. The secondary objective is to obtain preliminary evidence of its impact on neurological function and quality-of-life outcomes. Four patients with C3/4-Th10 level, complete subacute (within 24 days post-injury) SCI will be recruited. After obtaining consent, cryopreserved cells will be thawed and prepared following a multi-step process including treatment with a γ-secretase inhibitor to promote cell differentiation. A total of 2 × 106 cells will be transplanted into the injured spinal cord parenchyma 14-28 days post-injury. Patients will also receive transient immunosuppression. This study protocol has been reviewed and approved by the Certified Committee for Regenerative Medicine and the Japanese Ministry of Health, Labor and Welfare (University Hospital Medical Information Network Clinical Trials Registry [UMIN-CTR] number, UMIN000035074; Japan Registry of Clinical Trials [jRCT] number, jRCTa031190228). DISCUSSION/CONCLUSION: We plan to start recruiting a patient as soon as the COVID-19 epidemic subsides. The primary focus of this clinical study is safety, and the number of transplanted cells may be too low to confirm efficacy. After confirming safety, a dose-escalation study is planned.

Awareness of Locomotive Syndrome and Factors Associated with Awareness: A Community-Based Cross-Sectional Study.

Locomotive syndrome is a condition of reduced mobility, and patients have a high risk of requiring nursing care. In order to investigate the level of awareness of the term "locomotive syndrome" and the factors relating to awareness in a community, awareness of locomotive syndrome was included in a questionnaire survey on health and daily life conducted in Koumi Town (Japan), which was distributed to 3181 eligible residents aged 40 years or older. Information on age, sex, marital status, educational attainment, lifestyle, and social environment was also collected, and the association of awareness with various factors was analyzed with two multivariable Poisson regression models. As a result, awareness among respondents was 44.6%. Awareness was significantly higher among women, those who were 60-79 years old, married, and had received higher education. Additionally, awareness was significantly associated with social factors, especially attendance at regional events within the last one year, in both women and men: the adjusted prevalence ratios (95% confidence intervals) were 1.26 (1.10-1.43) and 1.48 (1.19-1.83), respectively. In conclusion, in addition to strengthen awareness rising campaigns targeting men and for younger people, providing health education at social settings such as regional events may help improve future musculoskeletal health in the elderly.

Knee pain and future decline in higher-level functional competence in community-dwelling older Japanese: the Kurabuchi cohort study.

BACKGROUND: The effect of knee osteoarthritis, which causes knee pain, on higher-level functional competence (HLFC) is not clear. OBJECTIVE: To clarify the effect of knee pain on HLFC in older people. DESIGN: Community-based prospective cohort study. SETTING: Kurabuchi town, Gumma prefecture, Japan. SUBJECTS: Community-dwelling individuals aged 65 and older. METHODS: A total of 808 residents participated to the baseline examinations. The frequency of knee pain, degree of pain and functional impairment resulting from the pain were asked at baseline (2005-2006) via a self-administered questionnaire in Japanese based on an English version of the Western Ontario and McMaster Universities Osteoarthritis Index. Information on HLFC at baseline and during home visits were collected annually until 2014 with the Tokyo Metropolitan Institute of Gerontology Index of Competence. The association between baseline knee pain and HLFC decline was assessed with a Cox proportional hazards model. RESULTS: Two factors, persistent knee pain and severe functional impairment caused by the pain, were significantly associated with future declines in total HLFC, with adjusted hazard ratios (95% confidence intervals) of 1.51 (1.08-2.11) and 1.49 (1.10-2.00). In analysis by subcategory, persistent knee pain had a significant adverse effect on participants' intellectual and social activities, and that severe physical functional impairment also had a significant impact on social activities. CONCLUSIONS: The clear association of the frequency of knee pain and resultant functional impairment with future HLFC decline indicates that collecting information about these factors may be useful in identifying older people at high risk of future HLFC decline.

Gait ability required to achieve therapeutic effect in gait and balance function with the voluntary driven exoskeleton in patients with chronic spinal cord injury: a clinical study.

STUDY DESIGN: A non-randomized open-label single-arm clinical trial. OBJECTIVES: To analyze the effect of body weight supported treadmill training (BWSTT) with the voluntary driven exoskeleton (VDE) in persons with differing levels and completeness of spinal cord injury (SCI) and differing walking abilities. SETTING: Keio University Hospital, Tokyo, Japan. METHODS: Twenty individuals with chronic SCI (age, 43 ± 17 years) classified as American Spinal Injury Association Impairment Scale grade A (n = 2), B (n = 4), C (n = 8), or D (n = 6) who had reached a plateau in recovery. Participants underwent twenty 60 min sessions of BWSTT with the hybrid assisted limb. The speed, distance, and duration walked in every 60 min training session were recorded. The Walking Index for SCI Scale II (WISCI-II), 10 meters walk test (10MWT), 2 min walk test, timed up and go (TUG) test, Berg Balance Scale (BBS), lower extremity motor score (LEMS), Barthel Index, and Functional Independence Measure were evaluated at pre and post intervention. RESULTS: There was a significant improvement in 10MWT, TUG, and BBS after the intervention. Walking ability significantly improved in participants with high walking ability at baseline (WISCI-II score 6-20; n = 12) but not in participants with low walking ability (WISCI-II score 0-3; n = 8). Significant improvement of BBS was also shown in participants with high walking ability at baseline. CONCLUSIONS: Patients with high walking ability at baseline responded better to the training than those with low walking ability.

Association Between Muscle Strength, Mobility, and the Progression of Hyperkyphosis in the Elderly: The Kurabuchi Cohort Study.

BACKGROUND: The progression of hyperkyphosis is a significant factor in declining general health. The purpose of this study was to investigate whether muscle strength and/or mobility is associated with the progression of hyperkyphosis in elderly people. METHODS: As part of a cohort study of community-dwelling elderly people, handgrip strength and mobility (evaluated with the Timed Up and Go Test: TUG) were assessed at baseline (2005-2006). Kyphosis was also evaluated at baseline and in follow-up examinations 4 years later, with the block method. To exclude the measurement error, the progression of kyphosis was defined as increase of 2 or more blocks. The association of kyphosis progression in each group with handgrip strength and/or mobility was assessed using Poisson regression analysis. RESULTS: Results on 403 participants were available for the final analysis, and kyphosis progression was observed in 53 (13.1%) of them. Multivariable analysis adjusted for sex, age, baseline block number, bone stiffness, TUG performance, or handgrip strength simultaneously revealed that low handgrip strength (<26 kg in men, <18 kg in women) and low mobility (>13.5 seconds) at baseline were both independently associated with kyphosis progression (adjusted risk ratio [95% confidence interval]: 2.11 [1.06-4.20] and 2.48 [1.26-4.89], respectively). CONCLUSIONS: Our study showed that low handgrip strength and low mobility are clearly associated with the progression of kyphosis. Further study is needed on the applicability of these results to preventive measures.

Concise Review: Laying the Groundwork for a First-In-Human Study of an Induced Pluripotent Stem Cell-Based Intervention for Spinal Cord Injury.

There have been numerous attempts to develop stem cell transplantation approaches to promote the regeneration of spinal cord injury (SCI). Our multicenter team is currently planning to launch a first-in-human clinical study of an induced pluripotent stem cell (iPSC)-based cell transplant intervention for subacute SCI. This trial was conducted as class I regenerative medicine protocol as provided for under Japan's Act on the Safety of Regenerative Medicine, using neural stem/progenitor cells derived from a clinical-grade, integration-free human "iPSC stock" generated by the Kyoto University Center for iPS Cell Research and Application. In the present article, we describe how we are preparing to initiate this clinical study, including addressing the issues of safety and tumorigenesis as well as practical problems that must be overcome to enable the development of therapeutic interventions for patients with chronic SCI. Stem Cells 2019;37:6-13.

Selective Ablation of Tumorigenic Cells Following Human Induced Pluripotent Stem Cell-Derived Neural Stem/Progenitor Cell Transplantation in Spinal Cord Injury.

Tumorigenesis is an important problem that needs to be addressed in the field of human stem/progenitor cell transplantation for the treatment of subacute spinal cord injury (SCI). When certain "tumorigenic" cell lines are transplanted into the spinal cord of SCI mice model, there is initial improvement of motor function, followed by abrupt deterioration secondary to the effect of tumor growth. A significant proportion of the transplanted cells remains undifferentiated after transplantation and is thought to increase the risk of tumorigenesis. In this study, using lentiviral vectors, we introduced the herpes simplex virus type 1 thymidine kinase (HSVtk) gene into a human induced pluripotent stem cell-derived neural stem/progenitor cell (hiPSC-NS/PC) line that is known to undergo tumorigenic transformation. Such approach enables selective ablation of the immature proliferating cells and thereby prevents subsequent tumor formation. In vitro, the HSVtk system successfully ablated the immature proliferative neural cells while preserving mature postmitotic neuronal cells. Similar results were observed in vivo following transplantation into the injured spinal cords of immune-deficient (nonobese diabetic-severe combined immune-deficient) mice. Ablation of the proliferating cells exerted a protective effect on the motor function which was regained after transplantation, simultaneously defending the spinal cord from the harmful tumor growth. These results suggest a potentially promising role of suicide genes in opposing tumorigenesis during stem cell therapy. This system allows both preventing and treating tumorigenesis following hiPSC-NS/PC transplantation without sacrificing the improved motor function. Stem Cells Translational Medicine 2019;8:260&270.

Association between visual classification of kyphosis and future ADL decline in community-dwelling elderly people: the Kurabuchi study.

This cohort study conducted in Japan showed that severe age-related kyphosis was visually detected. The visual assessment of kyphosis was associated with declines in ADL, suggesting that we can easily identify people at high risk to develop future ADL reduction in the community setting. PURPOSE: Age-related kyphosis is related with declines in activities of daily living (ADL). Its conventional diagnosis has been made by orthopedic surgeons and trained examiners using specialized equipment such as X-rays. We investigated whether visual classification of kyphosis by laypersons accurately predicted future ADL decline. METHODS: This study was part of the Kurabuchi Study, a cohort study of community-dwelling elderly Japanese. Between 2009 and 2010, three layperson raters used reference illustrations to classify 532 participants without ADL decline at study baseline into four categories. Other examiners used conventional methods to assess kyphosis in the same participants: curve ruler, Spinal Mouse, and the block method. ADL decline was defined as the development of dependence according to the Katz Index, admission to a nursing home, or certification of long-term care need. RESULTS: Thirty-five of the participants (6.6%) were classified with the most severe degree of kyphosis at baseline by visual assessment. Interrater agreement was high (Kappa = 0.73) for the most severe group. During 4.5 years of follow-up, 106 participants (19.9%) showed ADL decline. On the basis of visual assessment, the adjusted risk ratio for ADL decline among the participants with the most severe kyphosis was 2.6 (95% CI: 1.4-4.6). Assessments of kyphosis made with the Spinal Mouse also accurately predicted ADL decline. CONCLUSIONS: Visual assessment of kyphosis predicted future declines in ADL in this study. Since our method requires no special tools or training, it may be useful for identifying those at high risk of ADL decline.

Association Between Knee Pain, Impaired Function, and Development of Depressive Symptoms.

OBJECTIVES: To examine the association between knee pain and function and depressive symptoms in older Japanese adults. DESIGN: Community-based prospective cohort study. SETTING: Kurabuchi Town, Gumma Prefecture, Japan. PARTICIPANTS: Individuals aged 65 and older (N = 573; n = 260 men, n = 313 women) without depressive symptoms participated in baseline examinations in 2005 and 2006; 95.6% participated in follow-up interviews (2007-08). MEASUREMENTS: Degree of knee pain and functional impairment was assessed at baseline using a self-administered questionnaire in Japanese based on an English version of the Western Ontario and McMaster Universities Osteoarthritis Index. The Geriatric Depression Scale was used to identify depressive symptoms in face-to-face home-visit interviews conducted 2 years later, and the association between knee pain and functional impairment and depressive symptoms was assessed using logistic regression. RESULTS: During the 2-year follow-up, 11.9% of participants developed depressive symptoms, and pain and functional impairment were found to be associated with development of these symptoms. Pain at night while in bed (adjusted odds ratio (aOR) = 2.6, 95% confidence interval (CI) = 1.4-4.9) and difficulty putting on socks (aOR = 3.7, 95% CI: 1.8-7.5), getting into and out of a car (aOR = 3.4, 95% CI = 1.8-6.5), and taking off socks (aOR = 3.1, 95% CI = 1.5-6.5) were found to be most strongly associated with development of depressive symptoms. CONCLUSION: Examining elderly people's responses to questions about pain at night and difficulties performing daily activities may be an efficient way of identifying those at high risk of developing depressive symptoms.

Low immunogenicity of mouse induced pluripotent stem cell-derived neural stem/progenitor cells.

Resolving the immunogenicity of cells derived from induced pluripotent stem cells (iPSCs) remains an important challenge for cell transplant strategies that use banked allogeneic cells. Thus, we evaluated the immunogenicity of mouse fetal neural stem/progenitor cells (fetus-NSPCs) and iPSC-derived neural stem/progenitor cells (iPSC-NSPCs) both in vitro and in vivo. Flow cytometry revealed the low expression of immunological surface antigens, and these cells survived in all mice when transplanted syngeneically into subcutaneous tissue and the spinal cord. In contrast, an allogeneic transplantation into subcutaneous tissue was rejected in all mice, and allogeneic cells transplanted into intact and injured spinal cords survived for 3 months in approximately 20% of mice. In addition, cell survival was increased after co-treatment with an immunosuppressive agent. Thus, the immunogenicity and post-transplantation immunological dynamics of iPSC-NSPCs resemble those of fetus-NSPCs.

Chronic musculoskeletal pain in Japan (the final report of the 3-year longitudinal study): Association with a future decline in activities of daily living.

BACKGROUND: Previous epidemiological surveys conducted in Japan highlighted problems with conventional approaches to treating chronic musculoskeletal pain. On the basis of prior studies, we initiated the "longitudinal investigation of chronic musculoskeletal pain" in 2010. In our first two reports, we revealed a high prevalence of chronic musculoskeletal pain, low satisfaction with treatment, and reduced quality of life. Those with severe and consistent low back pain had the highest risk of the persisting pain. The risk factors for developing chronic pain also included working in a professional, managerial, or clerical/specialist occupation, being female, having a body mass index ≥25, currently using alcohol or cigarettes, and having completed an educational level of vocational school or higher. As the final step of the epidemiological survey, the present study examined the effect of chronic musculoskeletal pain on a future decline in activities of daily living (ADL). METHODS: A questionnaire was sent to individuals who participated in the research project in 2010. Follow-up research examining loss of basic or instrumental ADL, or certification of long-term care requirements, was conducted in 2013 ( n = 4989 subjects). RESULTS: The 3-year follow-up data revealed that chronic musculoskeletal pain was associated with a decline in ADL, even after adjusting for covariables such as age, sex, and smoking (adjusted odds ratio, 1.56; 95% confidential interval, 1.16-2.10). CONCLUSIONS: Chronic musculoskeletal pain is associated with future declines in ADL; therefore, relief of the chronic musculoskeletal pain may be important to maintain an active elderly population.

Regulation of RhoA by STAT3 coordinates glial scar formation.

Understanding how the transcription factor signal transducer and activator of transcription-3 (STAT3) controls glial scar formation may have important clinical implications. We show that astrocytic STAT3 is associated with greater amounts of secreted MMP2, a crucial protease in scar formation. Moreover, we report that STAT3 inhibits the small GTPase RhoA and thereby controls actomyosin tonus, adhesion turnover, and migration of reactive astrocytes, as well as corralling of leukocytes in vitro. The inhibition of RhoA by STAT3 involves ezrin, the phosphorylation of which is reduced in STAT3-CKO astrocytes. Reduction of phosphatase and tensin homologue (PTEN) levels in STAT3-CKO rescues reactive astrocytes dynamics in vitro. By specific targeting of lesion-proximal, reactive astrocytes in Nestin-Cre mice, we show that reduction of PTEN rescues glial scar formation in Nestin-Stat3+/- mice. These findings reveal novel intracellular signaling mechanisms underlying the contribution of reactive astrocyte dynamics to glial scar formation.

Fail-Safe System against Potential Tumorigenicity after Transplantation of iPSC Derivatives.

Human induced pluripotent stem cells (iPSCs) are promising in regenerative medicine. However, the risks of teratoma formation and the overgrowth of the transplanted cells continue to be major hurdles that must be overcome. Here, we examined the efficacy of the inducible caspase-9 (iCaspase9) gene as a fail-safe against undesired tumorigenic transformation of iPSC-derived somatic cells. We used a lentiviral vector to transduce iCaspase9 into two iPSC lines and assessed its efficacy in vitro and in vivo. In vitro, the iCaspase9 system induced apoptosis in approximately 95% of both iPSCs and iPSC-derived neural stem/progenitor cells (iPSC-NS/PCs). To determine in vivo function, we transplanted iPSC-NS/PCs into the injured spinal cord of NOD/SCID mice. All transplanted cells whose mass effect was hindering motor function recovery were ablated upon transduction of iCaspase9. Our results suggest that the iCaspase9 system may serve as an important countermeasure against post-transplantation adverse events in stem cell transplant therapies.

Evaluation of the immunogenicity of human iPS cell-derived neural stem/progenitor cells in vitro.

To achieve the goal of a first-in-human trial for human induced pluripotent stem cell (hiPSC)-based transplantation for the treatment of various diseases, allogeneic human leukocyte antigen (HLA)-matched hiPSC cell banks represent a realistic tool from the perspective of quality control and cost performance. Furthermore, considering the limited therapeutic time-window for acute injuries, including neurotraumatic injuries, an iPS cell bank is of potential interest. However, due to the relatively immunoprivileged environment of the central nervous system, it is unclear whether HLA matching is required in hiPSC-derived neural stem/progenitor cell (hiPSC-NS/PC) transplantation for the treatment of neurodegenerative diseases and neurotraumatic injuries. In this study, we evaluated the significance of HLA matching in hiPSC-NS/PC transplantation by performing modified mixed lymphocyte reaction (MLR) assays with hiPSC-NS/PCs. Compared to fetus-derived NS/PCs, the expression levels of human leukocyte antigen-antigen D related (HLA-DR) and co-stimulatory molecules on hiPSC-NS/PCs were significantly low, even with the addition of tumor necrosis factor-α (TNFα) and/or interferon-γ (IFNγ) to mimic the inflammatory environment surrounding transplanted hiPSC-NS/PCs in injured tissues. Interestingly, both the allogeneic HLA-matched and the HLA-mismatched responses were similarly low in the modified MLR assay. Furthermore, the autologous response was also similar to the allogeneic response. hiPSC-NS/PCs suppressed the proliferative responses of allogeneic HLA-mismatched peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner. Thus, the low antigen-presenting function and immunosuppressive effects of hiPSC-NS/PCs result in a depressed immune response, even in an allogeneic HLA-mismatched setting. It is crucial to verify whether these in vitro results are reproducible in a clinical setting.

Pretreatment with a γ-Secretase Inhibitor Prevents Tumor-like Overgrowth in Human iPSC-Derived Transplants for Spinal Cord Injury.

Neural stem/progenitor cells (NS/PCs) derived from human induced pluripotent stem cells (hiPSCs) are considered to be a promising cell source for cell-based interventions that target CNS disorders. We previously reported that transplanting certain hiPSC-NS/PCs in the spinal cord results in tumor-like overgrowth of hiPSC-NS/PCs and subsequent deterioration of motor function. Remnant immature cells should be removed or induced into more mature cell types to avoid adverse effects of hiPSC-NS/PC transplantation. Because Notch signaling plays a role in maintaining NS/PCs, we evaluated the effects of γ-secretase inhibitor (GSI) and found that pretreating hiPSC-NS/PCs with GSI promoted neuronal differentiation and maturation in vitro, and GSI pretreatment also reduced the overgrowth of transplanted hiPSC-NS/PCs and inhibited the deterioration of motor function in vivo. These results indicate that pretreatment with hiPSC-NS/PCs decreases the proliferative capacity of transplanted hiPSC-NS/PCs, triggers neuronal commitment, and improves the safety of hiPSC-based approaches in regenerative medicine.

Pathological classification of human iPSC-derived neural stem/progenitor cells towards safety assessment of transplantation therapy for CNS diseases.

The risk of tumorigenicity is a hurdle for regenerative medicine using induced pluripotent stem cells (iPSCs). Although teratoma formation is readily distinguishable, the malignant transformation of iPSC derivatives has not been clearly defined due to insufficient analysis of histology and phenotype. In the present study, we evaluated the histology of neural stem/progenitor cells (NSPCs) generated from integration-free human peripheral blood mononuclear cell (PBMC)-derived iPSCs (iPSC-NSPCs) following transplantation into central nervous system (CNS) of immunodeficient mice. We found that transplanted iPSC-NSPCs produced differentiation patterns resembling those in embryonic CNS development, and that the microenvironment of the final site of migration affected their maturational stage. Genomic instability of iPSCs correlated with increased proliferation of transplants, although no carcinogenesis was evident. The histological classifications presented here may provide cues for addressing potential safety issues confronting regenerative medicine involving iPSCs.