Persistent Orthostatic Hypotension Following Surgery for Adult Spinal Deformity: Prevalence, Risk Factors, and Cardiovascular Evaluation.

STUDY DESIGN: Retrospective case-control study. PURPOSE: To understand the prevalence of persistent orthostatic hypotension (POH), as well as its risk factors and cardiovascular pathology, in patients receiving surgery for the adult spinal deformity (ASD). OVERVIEW OF LITERATURE: Although reports of the incidence of and risk factors for POH in different spinal disorders have recently been published, we are not aware of the comprehensive evaluation of POH following surgery for ASD. METHODS: We examined medical records from a single central database for 65 patients receiving surgical treatment for ASD. Statistical comparisons were made between patients who experienced postoperative POH and those who did not, by examining patient and operative characteristics, such as age, sex, comorbidities, functional status, preoperative neurological function, vertebral fractures, three-column osteotomy, total operative time, estimated blood loss, length of stay, and radiographic parameters. The determinants of POH were assessed using multiple logistic regression. RESULTS: We showed that postoperative POH was a complication of ASD surgery, with a 9% incidence rate. Patients with POH were statistically considerably more likely to require supported walkers due to partial paralysis and to have comorbidities including diabetes and neurodegenerative disease (ND). Furthermore, ND was an independent risk factor for postoperative POH (odds ratio, 4.073; 95% confidence interval, 1.094-8.362; p =0.020). Moreover, perioperative evaluation of the inferior vena cava showed that patients with postoperative POH had preoperative congestive heart failure and had hypovolemia lower postoperative diameter of the inferior vena cava than patients without POH. CONCLUSIONS: Postoperative POH is a potential complication of ASD surgery. The most pertinent risk factor is having an ND. According to our study, patients who have surgery for ASD may experience alterations in their hemodynamics.

Natural history and surgical outcomes of idiopathic spinal cord herniation.

STUDY DESIGN: Retrospective multicenter study. OBJECTIVES: Although surgery is frequently selected for the treatment of idiopathic spinal cord herniation (ISCH), its impact on functional outcomes has yet to be fully understood given the limited number of patients in previous studies. This study aims to evaluate the symptomatic history and surgical outcomes of ISCH. SETTING: Three institutions in Japan. METHODS: A total of 34 subjects with ISCH were retrospectively enrolled and followed up for at least 2 years. Demographic information, imaging findings, and clinical outcomes were collected. Functional status was assessed using the JOA score. RESULTS: The types of neurologic deficit were monoparesis, Brown-Sequard, and paraparesis in 5, 17, and 12 cases, with their mean disease duration being 1.2, 4.2, and 5.8 years, respectively. Significant differences in disease duration were observed between the monoparesis and Brown-Sequard groups (p < 0.01) and between the monoparesis and paraparesis groups (p = 0.04). Surgery promoted significantly better recovery rates from baseline. Correlations were observed between age at surgery and recovery rate (p < 0.01) and between disease duration and recovery rate (p = 0.04). The mean recovery rates were 82.6%, 51.6%, and 29.1% in the monoparesis, Brown-Sequard, and paraparesis groups, respectively. The monoparesis group had a significantly higher recovery rate than did the Brown-Sequard (p = 0.045) and paraparesis groups (p < 0.01). CONCLUSIONS: Longer disease duration was correlated with the progression of neurologic deficit. Older age, and worse preoperative neurologic status hindered postoperative functional recovery. These results highlight the need to consider surgical timing before neurologic symptoms deteriorate.

Improvement of Coxarthrosis Due to Realignment of Pelvic Retroversion Following Spinal Corrective Surgery: A Case Report.

CASE: A 70-year-old woman presented with severe trunk deformity, gait disturbance, and bilateral hip pain. Radiography and magnetic resonance imaging revealed severe spinal kyphosis, bilateral osteoarthritis of the hip joints, and lumbar canal stenosis. A 2-stage corrective surgery for the treatment of spinal kyphosis was performed. Subsequently, the spinopelvic alignment changed remarkably. The spinal symptoms and radiographic parameters improved postoperatively, and bilateral hip pain and range of motion also showed improvement. CONCLUSION: Corrective surgery for the treatment of degenerative spinal kyphosis affected the spinopelvic alignment, and the symptoms of simultaneous coxarthrosis also improved after the corrective surgery.

In vivo monitoring of remnant undifferentiated neural cells following human induced pluripotent stem cell-derived neural stem/progenitor cells transplantation.

Transplantation of human-induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs) is a promising treatment for a variety of neuropathological conditions. Although previous reports have indicated the effectiveness of hiPSC-NS/PCs transplantation into the injured spinal cord of rodents and nonhuman primates, long-term observation of hiPSC-NS/PCs post-transplantation suggested some "unsafe" differentiation-resistant properties, resulting in disordered overgrowth. These findings suggest that, even if "safe" NS/PCs are transplanted into the human central nervous system (CNS), the dynamics of cellular differentiation of stem cells should be noninvasively tracked to ensure safety. Positron emission tomography (PET) provides molecular-functional information and helps to detect specific disease conditions. The current study was conducted to visualize Nestin (an NS/PC marker)-positive undifferentiated neural cells in the CNS of immune-deficient (nonobese diabetic-severe combined immune-deficient) mice after hiPSC-NS/PCs transplantation with PET, using 18 kDa translocator protein (TSPO) ligands as labels. TSPO was recently found to be expressed in rodent NS/PCs, and its expression decreased with the progression of neuronal differentiation. We hypothesized that TSPO would also be present in hiPSC-NS/PCs and expressed strongly in residual immature neural cells after transplantation. The results showed high levels of TSPO expression in immature hiPSC-NS/PCs-derived cells, and decreased TSPO expression as neural differentiation progressed in vitro. Furthermore, PET with [18 F] FEDAC (a TSPO radioligand) was able to visualize the remnant undifferentiated hiPSC-NS/PCs-derived cells consisting of TSPO and Nestin+ cells in vivo. These findings suggest that PET with [18 F] FEDAC could play a key role in the safe clinical application of CNS repair in regenerative medicine.

An NMF-based approach to discover overlooked differentially expressed gene regions from single-cell RNA-seq data.

Single-cell RNA sequencing has enabled researchers to quantify the transcriptomes of individual cells, infer cell types and investigate differential expression among cell types, which will lead to a better understanding of the regulatory mechanisms of cell states. Transcript diversity caused by phenomena such as aberrant splicing events have been revealed, and differential expression of previously unannotated transcripts might be overlooked by annotation-based analyses. Accordingly, we have developed an approach to discover overlooked differentially expressed (DE) gene regions that complements annotation-based methods. Our algorithm decomposes mapped count data matrix for a gene region using non-negative matrix factorization, quantifies the differential expression level based on the decomposed matrix, and compares the differential expression level based on annotation-based approach to discover previously unannotated DE transcripts. We performed single-cell RNA sequencing for human neural stem cells and applied our algorithm to the dataset. We also applied our algorithm to two public single-cell RNA sequencing datasets correspond to mouse ES and primitive endoderm cells, and human preimplantation embryos. As a result, we discovered several intriguing DE transcripts, including a transcript related to the modulation of neural stem/progenitor cell differentiation.

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.

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.

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.

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.

Whole-Genome DNA Methylation Analyses Revealed Epigenetic Instability in Tumorigenic Human iPS Cell-Derived Neural Stem/Progenitor Cells.

Although human induced pluripotent stem cell (hiPSC) derivatives are considered promising cellular resources for regenerative medicine, their tumorigenicity potentially limits their clinical application in hiPSC technologies. We previously demonstrated that oncogenic hiPSC-derived neural stem/progenitor cells (hiPSC-NS/PCs) produced tumor-like tissues that were distinct from teratomas. To gain insight into the mechanisms underlying the regulation of tumorigenicity in hiPSC-NS/PCs, we performed an integrated analysis using the Infinium HumanMethylation450 BeadChip array and the HumanHT-12 v4.0 Expression BeadChip array to compare the comprehensive DNA methylation and gene expression profiles of tumorigenic hiPSC-NS/PCs (253G1-NS/PCs) and non-tumorigenic cells (201B7-NS/PCs). Although the DNA methylation profiles of 253G1-hiPSCs and 201B7-hiPSCs were similar regardless of passage number, the methylation status of the global DNA methylation profiles of 253G1-NS/PCs and 201B7-NS/PCs differed; the genomic regions surrounding the transcriptional start site of the CAT and PSMD5 genes were hypermethylated in 253G1-NS/PCs but not in 201B7-NS/PCs. Interestingly, the aberrant DNA methylation profile was more pronounced in 253G1-NS/PCs that had been passaged more than 15 times. In addition, we identified aberrations in DNA methylation at the RBP1 gene locus; the DNA methylation frequency in RBP1 changed as 253G1-NS/PCs were sequentially passaged. These results indicate that different NS/PC clones have different DNA methylomes and that DNA methylation patterns are unstable as cells are passaged. Therefore, DNA methylation profiles should be included in the criteria used to evaluate the tumorigenicity of hiPSC-NS/PCs in the clinical setting. Stem Cells 2017;35:1316-1327.

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.