Protocol improvement and multisite validation of a digital soft agar colony formation assay for tumorigenic transformed cells intermingled in cell therapy products

BACKGROUND AIMS

The administration of human cell-processed therapeutic products (hCTPs) is associated with a risk of tumorigenesis due to the transformed cellular contaminants. To mitigate this risk, these impurities should be detected using sensitive and validated assays. The digital soft agar colony formation (D-SAC) assay is an ultrasensitive in vitro test for detecting tumorigenic transformed cells in hCTPs.

METHODS

In this study, we first evaluated the colony formation efficiency (CFE) precision of tumorigenic reference cells in positive control samples according to a previously reported D-SAC assay protocol (Protocol I) from multiple laboratories. However, the CFE varied widely among laboratories. Thus, we improved and optimized the test protocol as Protocol II to reduce variability in the CFE of tumorigenic reference cells. Subsequently, the improved protocol was validated at multiple sites. Human mesenchymal stromal cells (hMSCs) were used as model cells, and positive control samples were prepared by spiking them with HeLa cells.

RESULTS

Based on the previously reported protocol, the CFE was estimated using an ultra-low concentration (0.0001%) of positive control samples in multiple plates. Next, we improved the protocol to reduce the CFE variability. Based on the CFE results, we estimated the sample size as the number of wells (Protocol II) and assessed the detectability of 0.0001% HeLa cells in hMSCs to validate the protocol at multiple sites. Using Protocol I yielded low CFEs (mean: 30%) and high variability between laboratories (reproducibility coefficient of variance [CV]: 72%). In contrast, Protocol II, which incorporated a relatively high concentration (0.002%) of HeLa cells in the positive control samples, resulted in higher CFE values (mean: 63%) and lower variability (reproducibility CV: 18%). Moreover, the sample sizes for testing were estimated as the number of wells per laboratory (314-570 wells) based on the laboratory-specific CFE (42-76%). Under these conditions, all laboratories achieved a detection limit of 0.0001% HeLa cells in hMSCs in a predetermined number of wells. Moreover, colony formation was not observed in the wells seeded with hMSCs alone.

CONCLUSIONS

The D-SAC assay is a highly sensitive and robust test for detecting malignant cells as impurities in hCTPs. In addition, optimal assay conditions were established to test tumorigenic impurities in hCTPs with high sensitivity and an arbitrary false negative rate.

Single-Cell RNA-Seq Reveals LRRC75A-Expressing Cell Population Involved in VEGF Secretion of Multipotent Mesenchymal Stromal/Stem Cells Under Ischemia

Human multipotent mesenchymal stromal/stem cells (MSCs) have been utilized in cell therapy for various diseases and their clinical applications are expected to increase in the future. However, the variation in MSC-based product quality due to the MSC heterogeneity has resulted in significant constraints in the clinical utility of MSCs. Therefore, we hypothesized that it might be important to identify and ensure/enrich suitable cell subpopulations for therapies using MSC-based products. In this study, we aimed to identify functional cell subpopulations to predict the efficacy of angiogenic therapy using bone marrow-derived MSCs (BM-MSCs). To assess its angiogenic potency, we observed various levels of vascular endothelial growth factor (VEGF) secretion among 11 donor-derived BM-MSC lines under in vitro ischemic culture conditions. Next, by clarifying the heterogeneity of BM-MSCs using single-cell RNA-sequencing analysis, we identified a functional cell subpopulation that contributed to the overall VEGF production in BM-MSC lines under ischemic conditions. We also found that leucine-rich repeat-containing 75A (LRRC75A) was more highly expressed in this cell subpopulation than in the others. Importantly, knockdown of LRRC75A using small interfering RNA resulted in significant inhibition of VEGF secretion in ischemic BM-MSCs, indicating that LRRC75A regulates VEGF secretion under ischemic conditions. Therefore, LRRC75A may be a useful biomarker to identify cell subpopulations that contribute to the angiogenic effects of BM-MSCs. Our work provides evidence that a strategy based on single-cell transcriptome profiles is effective for identifying functional cell subpopulations in heterogeneous MSC-based products.

International evaluation study of a highly efficient culture assay for detection of residual human pluripotent stem cells in cell therapies

Aim & methods: The Health and Environmental Sciences Institute Cell Therapy-TRAcking, Circulation & Safety Technical Committee launched an international, multisite study to evaluate the sensitivity and reproducibility of the highly efficient culture (HEC) assay, an in vitro assay to detect residual undifferentiated human pluripotent stem cells (hPSCs) in cell therapy products. Results: All facilities detected colonies of human induced pluripotent stem cells (hiPSCs) when five hiPSCs were spiked into 1 million hiPSC-derived cardiomyocytes. Spiking with a trace amount of hiPSCs revealed that repeatability accounts for the majority of reproducibility while the true positive rate was high. Conclusion: The results indicate that the HEC assay is highly sensitive and robust and can be generally applicable for tumorigenicity evaluation of hPSC-derived cell therapy products.

Evaluation of the reproducibility and positive controls of cellular immortality test for the detection of immortalized cellular impurities in human cell-processed therapeutic products

INTRODUCTION

Contamination of human cell-processed therapeutic products (hCTPs) with tumorigenic/immortalized cellular impurities is a major concern in the manufacturing and quality control of hCTPs. The cellular immortality test based on cell growth analysis is a method for detecting tumorigenic/immortalized cellular impurities in hCTPs. However, the performance of the cellular immortality test has not yet been well characterized. In this study, we examined the reproducibility of the cellular immortality test in detecting HeLa cells as a model of tumorigenic cellular impurities, as well as the applicability of other models of cellular impurities with different tumorigenicity to the cellular immortality test.

METHODS

Using HeLa cells as a model for cellular impurities, we measured the growth rate of human mesenchymal stem cells (hMSCs) supplemented with HeLa cells at concentrations ranging from 0.01 to 0.0001% at each passage in three laboratories and evaluated the reproducibility of the detection of immortalized cellular impurities. In addition, HEK293 cells (another immortalized cell line) and MRC-5 cells (a non-immortalized cell line) were employed as cellular impurity models that exhibit different growth characteristics from HeLa cells, and the ability of the cellular immortality test to detect these different impurities when mixed with hMSCs was examined.

RESULTS

In the multisite study, the growth rate of hMSCs supplemented with 1 and 10 HeLa cells (0.0001% and 0.001%) significantly increased and reached a plateau in all three laboratories, whereas those of hMSCs alone eventually decreased. Moreover, when hMSCs were supplemented with 10 and 100 HEK293 and MRC-5 cells (0.001% and 0.01%), the growth rate significantly increased. The growth rate of hMSCs supplemented with HEK293 cells increased with passage and remained high, whereas that of hMSCs supplemented with MRC-5 cells eventually decreased, as in the case of hMSCs alone.

CONCLUSIONS

These results indicate that the cellular immortality test is reproducible and can detect immortalized (i.e., potentially tumorigenic) cells such as HEK293 cells with a lower growth rate than HeLa cells by discriminating against normal cells, which could contribute to ensuring the safety and quality of hCTPs.

Research and Development Strategy for Future Embryonic Stem Cell-Based Therapy in Japan

Herewith, we review an updated progress of regenerative medical products using human embryonic stem cells (ESCs) in Japan. Two groups from Kyoto University and the National Center for Child Health and Development (NCCHD) established a novel derivation/cultivation system of ESCs for potential application in translational and clinical research. At the first stage of ESC derivation, murine feeder cells have been used in line with Japanese guidelines on public health associated with the implementation of the xenograft. To avoid exposure of ESCs to animal products in culture media, a xeno-free cultivating system has been established. Twelve ESCs (KhES-1, KhES-2, KhES-3, KhES-4, KhES-5, SEES-1, SEES-2, SEES-3, SEES-4, SEES-5, SEES-6, and SEES-7) are now available under a clinically relevant platform for industrially and clinically applicable regenerative medical products. NCCHD submitted an investigative new drug application to the Pharmaceuticals and Medical Devices Agency (PMDA) for using ESC-based products in patients with hyperammonemia due to genetic defects on March 2018 under the Pharmaceutical Affairs Law (now revised to the Pharmaceuticals, Medical Devices, and Other Therapeutic Products Act). Currently, up to ten ESC-based products are being prepared for intractable and rare disorders in Japan.

Multisite studies for validation and improvement of a highly efficient culture assay for detection of undifferentiated human pluripotent stem cells intermingled in cell therapy products

BACKGROUND AIMS

The Multisite Evaluation Study on Analytical Methods for Non-Clinical Safety Assessment of Human-Derived Regenerative Medical Products (MEASURE) is a Japanese experimental public-private partnership initiative, which aims to standardize methodology for tumorigenicity evaluation of human pluripotent stem cell (hPSC)-derived cell therapy products (CTPs). Undifferentiated hPSCs possess tumorigenic potential, and thus residual undifferentiated hPSCs are one of the major hazards for the risk of tumor formation from hPSC-derived CTPs. Among currently available assays, a highly efficient culture (HEC) assay is reported to be one of the most sensitive for the detection of residual undifferentiated hPSCs.

METHODS

MEASURE first validated the detection sensitivity of HEC assay and then investigated the feasibility of magnetic-activated cell sorting (MACS) to improve sensitivity.

RESULTS

The multisite experiments confirmed that the lower limit of detection under various conditions to which the human induced pluripotent stem cell lines and culture medium/substrate were subjected was 0.001%. In addition, MACS concentrated cells expressing undifferentiated cell markers and consequently achieved a detection sensitivity of 0.00002%.

CONCLUSIONS

These results indicate that HEC assay is highly sensitive and robust and that the application of MACS on this assay is a promising tool for further mitigation of the potential tumorigenicity risk of hPSC-derived CTPs.

Tumorigenicity-associated characteristics of human iPS cell lines

Human induced pluripotent stem cells (hiPSCs) represent promising raw materials of human cell-based therapeutic products (hCTPs). As undifferentiated hiPSCs exhibit intrinsic tumorigenicity properties that enable them to form teratomas, hCTPs containing residual undifferentiated hiPSCs may cause tumor formation following transplantation. We first established quantitative and sensitive tumorigenicity testing of hiPSCs dissociated into single cells using NOD/Shi-scid IL2Rγnull (NOG) mice by inhibiting apoptosis of hiPSCs with a Rho kinase inhibitor. To examine different features in tumorigenicity of various hiPSCs, 10 commonly available hiPSC lines were subjected to in vivo tumorigenicity testing. Transplanted hiPSC lines showed remarkable variation in tumor incidence, formation latency, and volumes. Most of the tumors formed were classified as immature teratomas. However, no signs of malignancies, such as carcinoma and sarcoma, were recognized in the tumors. Characteristics associated tumorigenicity of hiPSCs were investigated with microarray analysis, karyotype analysis, and whole exome sequencing. Gene expression profiling and pathway analysis supported different features of hiPSC lines in tumorigenicity. hiPSC lines showed chromosomal abnormalities in some lines and 61-77 variants of cancer-related genes carrying effective nonsynonymous mutations, which were confirmed in the COSMIC databases. In this study, the chromosomal abnormalities and cancer-related gene mutations observed in hiPSC lines did not lead to the malignancy of tumors derived from hiPSCs. Our results suggest that the potential tumorigenicity risk of hCTPs containing residual undifferentiated hiPSCs is dependent on not only amounts of undifferentiated hiPSCs but also features of the cell lines used as raw materials, a finding that should be considered from the perspective of quality of hCTPs used.

Identification of a Gene Encoding Slow Skeletal Muscle Troponin T as a Novel Marker for Immortalization of Retinal Pigment Epithelial Cells

Human pluripotent stem cells (hPSCs) are leading candidate raw materials for cell-based therapeutic products (CTPs). In the development of hPSC-derived CTPs, it is imperative to ensure that they do not form tumors after transplantation for safety reasons. Because cellular immortalization is a landmark of malignant transformation and a common feature of cancer cells, we aimed to develop an in vitro assay for detecting immortalized cells in CTPs. We employed retinal pigment epithelial (RPE) cells as a model of hPSC-derived products and identified a gene encoding slow skeletal muscle troponin T (TNNT1) as a novel marker of immortalized RPE cells by comprehensive microarray analysis. TNNT1 mRNA was commonly upregulated in immortalized RPE cells and human induced pluripotent stem cells (hiPSCs), which have self-renewal ability. Additionally, we demonstrated that TNNT1 mRNA expression is higher in several cancer tissues than in normal tissues. Furthermore, stable expression of TNNT1 in ARPE-19 cells affected actin filament organization and enhanced their migration ability. Finally, we established a simple and rapid qRT-PCR assay targeting TNNT1 transcripts that detected as low as 3% of ARPE-19 cells contained in normal primary RPE cells. Purified hiPSC-derived RPE cells showed TNNT1 expression levels below the detection limit determined with primary RPE cells. Our qRT-PCR method is expected to greatly contribute to process validation and quality control of CTPs.

Ultra-sensitive detection of tumorigenic cellular impurities in human cell-processed therapeutic products by digital analysis of soft agar colony formation

Contamination with tumorigenic cellular impurities is one of the most pressing concerns for human cell-processed therapeutic products (hCTPs). The soft agar colony formation (SACF) assay, which is a well-known in vitro assay for the detection of malignant transformed cells, is applicable for the quality assessment of hCTPs. Here we established an image-based screening system for the SACF assay using a high-content cell analyzer termed the digital SACF assay. Dual fluorescence staining of formed colonies and the dissolution of soft agar led to accurate detection of transformed cells with the imaging cytometer. Partitioning a cell sample into multiple wells of culture plates enabled digital readout of the presence of colonies and elevated the sensitivity for their detection. In practice, the digital SACF assay detected impurity levels as low as 0.00001% of the hCTPs, i.e. only one HeLa cell contained in 10,000,000 human mesenchymal stem cells, within 30 days. The digital SACF assay saves time, is more sensitive than in vivo tumorigenicity tests, and would be useful for the quality control of hCTPs in the manufacturing process.

Highly sensitive droplet digital PCR method for detection of residual undifferentiated cells in cardiomyocytes derived from human pluripotent stem cells

Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), are leading candidate cells as raw materials for cell therapy products, because of their capacity for pluripotent differentiation and unlimited self-renewal. hPSC-derived products have already entered the scope of clinical application. However, the assessment and control of their tumorigenicity remains to be a critical challenge. Sensitive detection of the pluripotent cellular impurities is necessary for the safety and quality control of the hPSC-derived products. In the present study, we established a sensitive assay for detection of the residual undifferentiated hiPSCs in cardiomyocytes, using droplet digital PCR (ddPCR). The ddPCR method with a probe and primers for LIN28 significantly detected as low as 0.001% undifferentiated hiPSCs in primary cardiomyocytes, which is equivalent to the ratio of a single hiPSC to 1 × 10⁵ cardiomyocytes. The ddPCR also showed that LIN28 expression is extremely low in human tissues including liver, heart, pancreas, kidney, spinal cord, corneal epithelium and lung. These results suggest that the ddPCR method targeting LIN28 transcripts is highly sensitive and useful for the quality assessment of various cell therapy products derived from hPSCs.

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A highly sensitive in vitro assay for detection of residual undifferentiated hiPSCs in hiPSC-derived cell therapy products.

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LIN28 mRNA is highly sensitive marker of residual undifferentiated hiPSCs in hiPSC-derived cardiomyocytes.

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The ddPCR assay using LIN28 as a target is able to detect 0.001% undifferentiated hiPSCs in primary cardiomyocytes.

Characterization of in vivo tumorigenicity tests using severe immunodeficient NOD/Shi-scid IL2Rγnull mice for detection of tumorigenic cellular impurities in human cell-processed therapeutic products

The contamination of human cell-processed therapeutic products (hCTPs) with tumorigenic cells is one of the major concerns in the manufacturing and quality control of hCTPs. However, no quantitative method for detecting the tumorigenic cellular impurities is currently standardized. NOD/Shi-scid IL2Rγnull (NOG) mice have shown high xeno-engraftment potential compared with other well-known immunodeficient strains, e.g. nude mice. Hypothesizing that tumorigenicity test using NOG mice could be a sensitive and quantitative method to detect a small amount of tumorigenic cells in hCTPs, we examined tumor formation after subcutaneous transplantation of HeLa cells, as a model of tumorigenic cells, in NOG mice and nude mice. Sixteen weeks after inoculation, the 50% tumor-producing dose (TPD50) values of HeLa cells were stable at 1.3 × 104 and 4.0 × 105 cells in NOG and nude mice, respectively, indicating a 30-fold higher sensitivity of NOG mice compared to that of nude mice. Transplanting HeLa cells embedded with Matrigel in NOG mice further decreased the TPD50 value to 7.9 × 10 cells, leading to a 5000-fold higher sensitivity, compared with that of nude mice. Additionally, when HeLa cells were mixed with 106 or 107 human mesenchymal stem cells as well as Matrigel, the TPD50 values in NOG mice were comparable to those of HeLa cells alone with Matrigel. These results suggest that the in vivo tumorigenicity test using NOG mice with Matrigel is a highly sensitive and quantitative method to detect a trace amount of tumorigenic cellular impurities in human somatic cells, which can be useful in the quality assessment of hCTPs.

Highly sensitive in vitro methods for detection of residual undifferentiated cells in retinal pigment epithelial cells derived from human iPS cells

Human induced pluripotent stem cells (hiPSCs) possess the capabilities of self-renewal and differentiation into multiple cell types, and they are free of the ethical problems associated with human embryonic stem cells (hESCs). These characteristics make hiPSCs a promising choice for future regenerative medicine research. There are significant obstacles, however, preventing the clinical use of hiPSCs. One of the most obvious safety issues is the presence of residual undifferentiated cells that have tumorigenic potential. To locate residual undifferentiated cells, in vivo teratoma formation assays have been performed with immunodeficient animals, which is both costly and time-consuming. Here, we examined three in vitro assay methods to detect undifferentiated cells (designated an in vitro tumorigenicity assay): soft agar colony formation assay, flow cytometry assay and quantitative real-time polymerase chain reaction assay (qRT-PCR). Although the soft agar colony formation assay was unable to detect hiPSCs even in the presence of a ROCK inhibitor that permits survival of dissociated hiPSCs/hESCs, the flow cytometry assay using anti-TRA-1-60 antibody detected 0.1% undifferentiated hiPSCs that were spiked in primary retinal pigment epithelial (RPE) cells. Moreover, qRT-PCR with a specific probe and primers was found to detect a trace amount of Lin28 mRNA, which is equivalent to that present in a mixture of a single hiPSC and 5.0×10⁴ RPE cells. Our findings provide highly sensitive and quantitative in vitro assays essential for facilitating safety profiling of hiPSC-derived products for future regenerative medicine research.

The mood stabilizer valproic acid improves defective neurite formation caused by Charcot-Marie-Tooth disease-associated mutant Rab7 through the JNK signaling pathway

Charcot-Marie-Tooth (CMT) disease is the most frequent peripheral neuropathy affecting the Schwann cells and neurons. CMT disease type 2 (CMT2) neuropathies are characterized by peripheral nerve aberrance. Four missense mutations of Rab7, a small GTPase of the Rab family involved in intracellular vesicular trafficking, are associated with the CMT2B phenotype. Despite a growing body of evidence concerning the gene structures responsible for genetically heterogenous CMT2B and other CMT2 neuropathies, little is known about the in vitro neuropathy model and how CMT2B-associated mutation-caused aberrant neuritogenesis is properly reversed. Here, we show that valproic acid (VPA), a classical mood-stabilizing drug, improves defective neurite formation in N1E-115 neuroblastoma cells regardless of which CMT2B-associated Rab7 mutant protein is expressed. The effect is mediated by c-Jun N-terminal kinase (JNK) signaling, but not by deacetylase inhibition activity of VPA itself. Furthermore, VPA has similar effects in dorsal root ganglion (DRG) neurons expressing any of the four mutant Rab7 proteins. Thus, VPA has a previously unknown potential to improve defective neuritogenesis associated with CMT2B in vitro, indicating that JNK should be a potential therapeutic target for treatments aimed at improving neuritogenesis.

Fluoxetine promotes gliogenesis during neural differentiation in mouse embryonic stem cells

Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed for treatment of mood disorders and depression, even during pregnancy and lactation. SSRIs are thought to be much safer than tricyclic antidepressants, with a low risk of embryonic toxicity. Several recent studies, however, have reported that fetal exposure to SSRIs increases the risk of adverse effects during fetal and neonatal development. This is consistent with our previous finding that fluoxetine, a prototypical SSRI, profoundly affected the viability of cultured embryonic stem (ES) cells as well as their ability to differentiate into cardiomyocytes. Furthermore, we found that fluoxetine induced fluctuations in ectodermal marker gene expression during ES cell differentiation, which suggests that fluoxetine may affect neural development. In the present study, we investigated the effects of fluoxetine on the process of differentiation from ES cells into neural cells using the stromal cell-derived inducing activity (SDIA) method. Fluoxetine treatment was found to enhance the expression of glial marker genes following neural differentiation, as observed by immunocytochemical analysis or quantitative RT-PCR. The promoter activity of glial marker genes was also significantly enhanced when cells were treated with fluoxetine, as observed by luciferase reporter assay. The expression of neuronal markers during ES cell differentiation into neural cells, on the other hand, was inhibited by fluoxetine treatment. In addition, FACS analysis revealed an increased population of glial cells in the differentiating ES cells treated with fluoxetine. These results suggest that fluoxetine could facilitate the differentiation of mouse ES cells into glial cell lineage, which may affect fetal neural development.

Enhanced effect of neuropeptide Y on food intake caused by blockade of the V(1A) vasopressin receptor

Food intake is regulated by various factors such as neuropeptide Y. Neuropeptide Y potently induces an increase in food intake, and simultaneously stimulates arginine-vasopressin (AVP) secretion in the brain. Recently, we reported that V(1A) vasopressin receptor-deficient (V(1A)R(-/-)) mice exhibited altered daily food intake accompanied with hyperglycemia and hyperleptinemia. Here, we further study the involvement of the AVP/V(1A) receptor in the appetite regulation of neuropeptide Y with V(1A)R(-/-) mice and antagonists for the AVP receptor. The intra-cerebral-ventricle administration of neuropeptide Y induced greater food consumption in V(1A)R(-/-) mice than wild-type (WT) mice, whereas an anorexigenic effect of leptin was not different between the two groups. This finding suggests that the orexigenic effect of neuropeptide Y was enhanced in V(1A)R(-/-) mice, leading to the increased food intake in response to the neuropeptide Y stimulation. In addition, the neuropeptide Y-induced orexigenic effect was enhanced by co-administration of OPC-21268, an antagonist for the V(1A) vasopressin receptor, into the cerebral ventricle in WT mice, whereas the neuropeptide Y-induced orexigenic effect was not affected by co-administration of SSR-149415, an antagonist for the V(1B) vasopressin receptor. These results indicate that AVP could suppress the neuropeptide Y-induced orexigenic effect via the V(1A) vasopressin receptor, and that blockade or inhibition of the AVP/V(1A) receptor signal resulted in the enhanced neuropeptide Y-induced orexigenic effect. Thus, we show that the AVP/V(1A) receptor is involved in appetite regulation as an anorexigenic factor for the neuropeptide Y-induced orexigenic effect.

Valproic acid-inducible Arl4D and cytohesin-2/ARNO, acting through the downstream Arf6, regulate neurite outgrowth in N1E-115 cells

The mood-stabilizing agent valproic acid (VPA) potently promotes neuronal differentiation. As yet, however, little is known about the underlying molecular mechanism. Here, we show that VPA upregulates cytohesin-2 and mediates neurite outgrowth in N1E-115 neuroblastoma cells. Cytohesin-2 is the guanine-nucleotide exchange factor (GEF) for small GTPases of the Arf family; it regulates many aspects of cellular functions including morphological changes. Treatment with the specific cytohesin family inhibitor SecinH3 or knockdown of cytohesin-2 with its siRNA results in blunted induction of neurite outgrowth in N1E-115 cells. The outgrowth is specifically inhibited by siRNA knockdown of Arf6, but not by that of Arf1. Furthermore, VPA upregulates Arl4D, an Arf-like small GTPase that has recently been identified as the regulator that binds to cytohesin-2. Arl4D knockdown displays an inhibitory effect on neurite outgrowth resulting from VPA, while expression of constitutively active Arl4D induces outgrowth. We also demonstrate that the addition of cell-permeable peptide, coupling the cytohesin-2-binding region of Arl4D into cells, reduces the effect of VPA. Thus, Arl4D is a previously unknown regulator of neurite formation through cytohesin-2 and Arf6, providing another example that the functional interaction of two different small GTPases controls an important cellular function.

Neurofibromatosis 2 tumor suppressor, the gene induced by valproic acid, mediates neurite outgrowth through interaction with paxillin

Valproic acid (VPA), the drug for bipolar disorder and epilepsy, has a potent ability to induce neuronal differentiation, yet comparatively little is presently known about the underlying mechanism. We previously demonstrated that c-Jun N-terminal kinase (JNK) phosphorylation of the focal adhesion protein paxillin mediates differentiation in N1E-115 neuroblastoma cells. Here, we show that VPA up-regulates the neurofibromatosis type 2 (NF2) tumor suppressor, merlin, to regulate neurite outgrowth through the interaction with paxillin. The inhibition of merlin function by its knockdown or expression of merlin harboring the Gln-538-to-Pro mutation, a naturally occurring NF2 missense mutation deficient in linking merlin to the actin cytoskeleton, decreases VPA-induced neurite outgrowth. Importantly, the expression of merlin by itself is not sufficient to induce neurite outgrowth, which requires co-expression with paxillin, the binding partner of merlin. In fact, the missense mutation Trp-60-to-Cys or Phe-62-to-Ser, that is deficient in binding to paxillin, reduces neurite outgrowth induced by VPA. In addition, co-expression of a paxillin construct harboring the mutation at the JNK phosphorylation site with merlin results in blunted induction of the outgrowth. We also find that the first LIM domain of paxillin is a major binding region with merlin and that expression of the isolated first LIM domain blocks the effects of VPA. Furthermore, similar findings that merlin regulates neurite outgrowth through the interaction with paxillin have been observed in several kinds of neuronal cells. These results suggest that merlin is an as yet unknown regulator of neurite outgrowth through the interaction with paxillin, providing a possibly common mechanism regulating neurite formation.

Involvement of protein-tyrosine phosphatase PTPMEG in motor learning and cerebellar long-term depression

Although protein-tyrosine phosphorylation is important for hippocampus-dependent learning, its role in cerebellum-dependent learning remains unclear. We previously found that PTPMEG, a cytoplasmic protein-tyrosine phosphatase expressed in Purkinje cells (PCs), bound to the carboxyl-terminus of the glutamate receptor delta2 via the postsynaptic density-95/discs-large/ZO-1 domain of PTPMEG. In the present study, we generated PTPMEG-knockout (KO) mice, and addressed whether PTPMEG is involved in cerebellar plasticity and cerebellum-dependent learning. The structure of the cerebellum in PTPMEG-KO mice appeared grossly normal. However, we found that PTPMEG-KO mice showed severe impairment in the accelerated rotarod test. These mice also exhibited impairment in rapid acquisition of the cerebellum-dependent delay eyeblink conditioning, in which conditioned stimulus (450-ms tone) and unconditioned stimulus (100-ms periorbital electrical shock) were co-terminated. Moreover, long-term depression at parallel fiber-PC synapses was significantly attenuated in these mice. Developmental elimination of surplus climbing fibers and the physiological properties of excitatory synaptic inputs to PCs appeared normal in PTPMEG-KO mice. These results suggest that tyrosine dephosphorylation events regulated by PTPMEG are important for both motor learning and cerebellar synaptic plasticity.

Inhibition of stress-induced adrenocorticotropin and prolactin secretion mediating hypophysiotropic factors by antagonist of AMPA type glutamate receptor

Glutamate is the dominant excitatory neurotransmitter in a large number of physiological processes including neuroendocrine regulation. Some pharmacological studies have shown that different subtypes of glutamate receptor, such as the N-methyl-D-aspartic acid (NMDA) and alpha-amino-3-hydroxy-5-methy-4-isoxazolepropionic acid (AMPA) receptors, are involved in stress-induced adrenocorticotropin (ACTH) and prolactin secretion. However, the roles of the respective glutamate receptors and the mechanism of ACTH and prolactin secretion during stress via these receptors have not been investigated in detail. In the present study, we evaluated the role of AMPA-type glutamate receptor in ACTH and prolactin regulation under restraint stress in adult male rats. Male rats pretreated with a selective AMPA receptor antagonist, 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX; 50 microg), through a lateral ventricle cannula were stressed by immobilization. Administration of NBQX inhibited ACTH and prolactin secretion in response to restraint stress. However, NBQX had no significant effects on the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine biosynthesis, as measured by the accumulation of 3, 4-dihydroxyphenylalanine (DOPA). In addition, administration of NBQX suppressed stress-induced prolactin secretion in the male rats pretreated with alpha-MT, an inhibitor of dopamine synthesis, and infused with dopamine solution (2.5 microg/200 microl/10 min). These results indicated that the effects of NBQX on prolactin secretion might be mediated by non-dopamine mechanisms. The contents of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) in the median eminence (ME) of the male rats decreased during restraint stress; however, the fluctuations in CRH and AVP were eliminated by NBQX administration. These results suggest that stress-induced ACTH and prolactin release mediated by neurotransmission via AMPA receptors might be partly attributable to hypophysiotropic regulatory factors in the hypothalamus.

M(3) muscarinic acetylcholine receptor plays a critical role in parasympathetic control of salivation in mice

The M(1) and M(3) subtypes are the major muscarinic acetylcholine receptors in the salivary gland and M(3) is reported to be more abundant. However, despite initial reports of salivation abnormalities in M(3)-knockout (M(3)KO) mice, it is still unclear which subtype is functionally relevant in physiological salivation. In the present study, salivary secretory function was examined using mice lacking specific subtype(s) of muscarinic receptor. The carbachol-induced [Ca(2+)](i) increase was markedly impaired in submandibular gland cells from M(3)KO mice and completely absent in those from M(1)/M(3)KO mice. This demonstrates that M(3) and M(1) play major and minor roles, respectively, in the cholinergically induced [Ca(2+)](i) increase. Two-dimensional Ca(2+)-imaging analysis revealed the patchy distribution of M(1) in submandibular gland acini, in contrast to the ubiquitous distribution of M(3). In vivo administration of a high dose of pilocarpine (10 mg kg(-1), s.c.) to M(3)KO mice caused salivation comparable to that in wild-type mice, while no salivation was induced in M(1)/M(3)KO mice, indicating that salivation in M(3)KO mice is caused by an M(1)-mediated [Ca(2+)](i) increase. In contrast, a lower dose of pilocarpine (1 mg kg(-1), s.c.) failed to induce salivation in M(3)KO mice, but induced abundant salivation in wild-type mice, indicating that M(3)-mediated salivation has a lower threshold than M(1)-mediated salivation. In addition, M(3)KO mice, but not M(1)KO mice, had difficulty in eating dry food, as shown by frequent drinking during feeding, suggesting that salivation during eating is mediated by M(3) and that M(1) plays no practical role in it. These results show that the M(3) subtype is essential for parasympathetic control of salivation and a reasonable target for the drug treatment and gene therapy of xerostomia, including Sjögren's syndrome.

Relationship between incidence and onset age of mammary tumours and uterine adenomyosis in four strains of mice: comparison with the findings of 40 generations previously

Like most characteristics studied in research, mammary tumourigenesis and uterine adenomyosis in mice are regulated by both genetic and environmental factors and information about the degree of participation of each factor in these lesions is important in the use of mice for investigations. Several parameters on spontaneous mammary tumours and uterine adenomyosis in four strains of mice with different potentials for these lesions were compared in those before and after more than 40 generations or more than 10 years (1987). During these periods, the mice were exposed to several different intangible or unavoidable environmental factors, although they are quite stable genetically by maintenance with full-sib mating. Nevertheless, small differences were observed between the present and 1987 regarding strain-related characteristics, such as the onset age, the cumulative incidence and the growth of mammary tumours and uterine adenomyosis. It is suggested that genetics is more influential than environmental factors regarding the maintenance of strain-related characteristics of mammary and uterine lesions.

Two inbred strains of mice with high and low mammary tumor potentials established from the same basal stock of Swiss albino (SHN and SLN): history of mammary tumorigenesis and reproduction after the 30th generation of full-sib mating

We established SHN and SLN strains of mice with a high and a low mammary tumor potentials from the same basal stock of Swiss albino. The selection history of females (mothers) for subsequent generations, mammary tumorigenesis and reproduction up to recent generations are presented and compared with the results up to F30 published in 1979. The changes with generation of each parameter varied in both strains except the conditions of female (mother) selection for subsequent generations, which were generally constant. However, the fluctuations in parameters up to F30 became generally smaller with advancing generations. Based on the fluctuations from generation to generation of mammary tumorigenic and reproductive parameters, an interdependency between mammary tumor potential and reproductivity is suggested in SLN, but less so in SHN. The pup growth rate was increased and associated with selection for mammary tumorigenesis in SHN; this parameter is usually used as an indicator of mother lactational performance in mice. The significance of selection for mammary tumor potential in association with reproductivity was further discussed.

Comparison of plasma component levels in four strains of female mice with different mammary tumour potentials

Based on the importance of general metabolic activity to mammary tumourigenesis, plasma component levels were examined at 6 and 10 months of age in female virgin mice of four strains, which in mammary tumour potential, rank in the descending order of SHN, GR/A, SLN and C3H/He. The plasma aspartate aminotransferase level elevated from 6 to 10 months of age in the SHN and GR/A, but not in the SLN and C3H/He strains. The total bilirubin level was higher in the former two strains than the latter two at both 6 and 10 months. The blood urea nitrogen level was highest in SHN. C3H/He had the lowest plasma levels of these components as well as amylase at both ages. The results indicate the signifcance to the mammary tumourigenic potential of plasma levels of certain components related to general metabolic activity.

Accidental poisoning of children in Japan: a report from the Japan Poison Information Center

The Japan Poison Information Center (JPIC) was founded only 6 years ago as a result of co-operation between the Ministry of Health and Welfare, the Japanese Association for Acute Medicine, the Japan Pediatric Society and other related medical organizations. The JPIC is the only poison information center admitted by the Ministry of Health and Welfare to provide toxicological information to medical personnel and the general public, and has two offices on duty in alternating 24 h shifts. Every year, JPIC receives about 30,000 inquiries. About 82% of these inquiries are from the general public and 84% of the patients are children 5 years and younger. We contrasted the data in the fiscal year 1991 with the data of the American Association of Poison Control Centers (AAPCC). Child poison exposure in Japan is characterized by a high exposure rate of children under 1 year of age to (mostly) household products. The JPIC also analyzed the cause of tobacco ingestion. It is considered that the Japanese lifestyle causes differences from those reported by AAPCC. We report the accidental poisoning of children in Japan.

Sequence characterization of the matrix protein genes of parainfluenza virus types 4A and 4B

The complete nucleotide sequences of the matrix protein (M) genes of parainfluenza virus types 4A and 4B (PIV-4A and -4B) were determined from cDNA of the mRNA, and found to be 1548 bases in length, exclusive of poly(A) sequences. The sequences contained a large open reading frame of 1146 nucleotides encoding 362 amino acids. A high degree of identity (96.1%) was observed between the amino acid sequences of PIV-4A and PIV-4B M. These M sequences were compared with those of 10 other paramyxoviruses and a phylogenetic tree was constructed.

Collateral circulation in Kawasaki disease with coronary occlusion or severe stenosis

Forty patients with Kawasaki disease with severe coronary sequelae were investigated. All had at least a 90% reduction in the diameter of the major coronary artery. Collateral vessels were seen in 32 of 33 (97%) patients with total occlusion. All patients with severe stenosis but not total occlusion had no or poorly developed collateral vessels. Analysis according to the presence or absence of collateral vessels showed no significant differences in the results of treadmill stress testing and myocardial imaging between these two groups. In patients treated surgically, the abnormalities recognized by these tests were normalized or improved when the bypass was patent. These data indicate that collateral circulation in patients with Kawasaki disease cannot be seen angiographically unless there is total occlusion and the presence of collateral circulation cannot provide protection against stress-induced myocardial ischemia.

Results from an international survey of Kawasaki disease in 1979-82

Kawasaki disease is a febrile illness of unknown etiology affecting mainly children younger than five years, 20% of whom develop coronary artery aneurysms. The disease was first reported in Japan, but case reports have come from several countries; epidemics apparently occur every two to three years. A committee of the International Society and Federation of Cardiology (ISFC) collaborated on an international, retrospective survey in mid-1983 through 1984, asking about Kawasaki disease cases seen in 1979-82 and their outcomes. Responses were received from 53 countries; reports from 20 countries indicated that no cases were seen in the years surveyed. Kawasaki disease did not always follow the Japanese pattern. An indication of 'epidemic' increases was found in some years in some countries. Recognition of Kawasaki disease varies considerably, but further educational efforts are likely to uncover additional cases, and intensive epidemiological efforts would be possible in a number of countries.

Long-term prognosis of Kawasaki disease patients with coronary artery obstruction

The prognosis of coronary artery obstruction was studied in patients with Kawasaki disease. Between May 1973 and December 1987, coronary artery obstruction was diagnosed by coronary angiography in 30 patients (21 males, 9 females), of whom, only 8 (26.7%) had clinical symptoms. One patient died after 9 years of illness. Two complained of frequent chest pain, which disappeared after bypass surgery in one case and spontaneously in the other. Five had symptomatic myocardial infarction. Myocardial ischemia was diagnosed in 31.8% by treadmill stress testing, but was well demonstrated in 85.7% by thallium-201 myocardial tomography. Frequent ventricular premature beats, Wenckebach-type atrioventricular block, and ST-segment depression accompanied by chest pain were recognized by 24-h Holter monitoring. In the past, the methods used to determine the prognosis of Kawasaki disease patients with coronary artery obstruction were not adequate. However, the examinations used in this study revealed an improved ability to determine the prognosis in this disease. Myocardial tomography, in particular, provided a more accurate evaluation of myocardial damage. Ventricular arrhythmias seem to be a serious problem in these patients. Therefore, careful observation using these tests, especially myocardial tomography and Holter monitoring, should be done even if the patients are free of symptoms.

Long-term prognosis of giant coronary aneurysm in Kawasaki disease: an angiographic study

The incidence of coronary obstruction subsequent to giant coronary aneurysm in Kawasaki disease was studied. In 20 cases, aneurysms with a maximal diameter greater than 8 mm were identified by coronary angiography 2 to 120 months (mean 16.9 months) after onset. There were 25 giant aneurysms among these 20 patients, all of whom underwent coronary angiography between 12 and 134 months (mean 31.7 months) after initial examination. Coronary obstruction occurred in six cases (30.0%), all within 4 years of onset of disease. There were five obstructive aneurysms in the right coronary artery (5/12; 41.7%) and two in the left coronary artery (2/13; 15.4%). One of these patients developed symptomatic myocardial infarction. Two had abnormal electrocardiographic findings suggesting myocardial infarction. In five cases, persistent perfusion defects were found by myocardial imaging. On the other hand, in two patients giant aneurysms persisted without obstructive changes for greater than 10 years. In both cases the aneurysm was in the left coronary artery and obstruction of the right coronary artery was found at initial angiography. These results seem to indicate the limited efficacy of antiplatelet therapy for giant coronary aneurysms in Kawasaki disease and that giant aneurysms are likely to progress to become obstructive within a few years even if antiplatelet therapy is given. Other forms of treatment, including surgery, should therefore be considered in such patients.

Ring chromosome 15 in a mother and her children

A case of ring chromosome 15 passed on to the index patient's two children is reported, and possible reasons for the infrequent records of inheritance of ring chromosome are suggested.

Myocarditis with myocardial infarction like findings in a 3-year old girl

A 3 year-old Japanese girl had an acute onset associated with vomiting. The electrocardiogram (ECG) indicated changes similar to those of acute myocardial infarction (MI); there was no past history of kawasaki disease. Selective coronary angiography taken on the 28th day of illness revealed no abnormality. Thallium 201 scintigraphy was also performed and it revealed that the area of absent myocardial uptake was in the anterior wall. In serological findings, antibody titers against Coxsackie B-3 virus had risen significantly; therefore acute myocarditis caused by Coxsackie B-3 virus infection was diagnosed.

Effects of fatness on the electrocardiogram in children aged 12-15 years

Using the 4-Lead Set Japanese Pediatric ECG Screening Criteria Proposal, the effects of fatness on the electrocardiograms were analyzed in 1025 junior high school children, aged 12-15 years (of whom 114 were obese). As the results show, significant differences were detected by the 1% two-sided test between the averages of the nonfat group and the middle- and high-fat groups with regard to S amplitude in leads V1-V3 for boys and girls, R amplitude in leads V4 and V5, SV1 + RV6, SV1 + RV5, and SV3 + RV3 for boys, and S amplitude in leads V4-V6 for girls. High R amplitudes were observed in leads V3 and V4 for the middle- and high-fat group of girls. When applying conventional ECG criteria for left ventricular hypertrophy to the middle- and high-fat groups of boys, the value of SV1 + RV6 greater than or equal to 4.5 mV instead of SV1 + RV6 greater than or equal to 5.0 mV is recommended.

Immunological studies on Kawasaki disease. I. Appearance of Hanganutziu-Deicher antibodies

Sera of patients with Kawasaki disease were studied for heterophile antibodies by means of enzyme immunoassay (EIA) with enzyme conjugated antisera to human IgM, IgG, IgA and IgE. Antibodies of IgM (43%), IgG (3%), IgA (11%) and IgE (49%) classes were demonstrated that combined with high molecular weight glycoprotein (HMWGP) of bovine red blood cells (BRBC) one of the antigenic preparations of the Hanganutziu-Deicher (H-D) heterophile system. Studies on sequential sera of the patients revealed that HMWGP antibodies of IgM and IgE classes began to appear in the second week, reached their peaks in the third week of the disease and declined gradually thereafter. Absorption studies on the positive sera showed that the HMWGP antibody activities were abolished by BRBC, sheep red blood cells and guinea-pig kidney tissues, confirming H-D specificity of these antibodies. EIA inhibition studies showed that the antibody activity was inhibited by HMWGP and partially by asialo-HMWGP and NGNA ganglioside rich preparation of BRBC but not by purified Paul-Bunnell or Forssman antigens. These results indicate that the H-D antibodies under investigation consist of antibodies of two different specificities; one directed against asialo-HMWGP and the other NGNA ganglioside of BRBC. Circulating immune complexes (IC) were demonstrated in 23% of the patients by means of anti-antibody inhibition test. Evidence was presented that IC in the sera of five patients were composed of H-D (HMWGP) antigen and its corresponding antibodies.

Development of a heart disease screening system for school children and its results in the Tokyo area in 1980

After the revision of the School Health Law in Japan the systems for heart disease screening for school children showed a great advance and the computerized devices for automatic evaluation of selected leads ECG and PCG were developed rapidly and have been improved in Japan. Two systems of heart disease screening for school children have been developed, that is, the Tokyo system and the "ECG-PCG for all children system". The Tokyo system utilizes a questionnaire, a physical examination by school physicians and a chest X-ray for the primary screening procedure and ECG-PCG for the secondary procedure. The "ECG-PCG for all children system" utilizes a questionnaire, a chest X-ray and ECG-PCG. The superiority of the ECG-PCG system was shown in comparison with the Tokyo system. Nearly twice as many cases of congenital heart disease were detected by the ECG-PCG system as compared with the Tokyo system, and many cases were disclosed for the first time. The "ECG-PCG for all children system" will probably be more popular in the near future in accordance with the advance of computerized systems.

The throat culture in Kawasaki disease

Recently, Kawasaki disease has been attracting more attention as a new acquired heart disease in pediatrics, but the etiology of this disease has still not been established. In this study, the authors performed throat cultures not only on the patients themselves but also on their parents in order to investigate its etiology. No abnormal and specific bacterium was found in the present study. However, there have been many reports which may suggest bacterial or viral involvement at the onset of this disease. Therefore, it may be necessary to continue bacteriological analysis more systematically.

Early and late postoperative studies in coronary arterial lesions resulting from Kawasaki's disease in children

From October, 1976, to February, 1980, eight children with coronary arterial lesions resulting from Kawasaki's disease underwent surgical treatment--aorta-coronary bypass, aorta-coronary bypass combined with right coronary aneurysmectomy, and aorta-coronary bypass combined with left ventricular aneurysmectomy. The autogenous saphenous vein was used for the bypass grafts. Selective angiography preformed 1 month after the operation revealed an early patency rate of 85%. Seven patients are now leading a normal school life, but one patient died suddenly during relatively strenuous exercise 3 years after the operation. Angiography performed in five patients 1 to 3 years after the operation and autopsy examination in one decreased patient revealed the late patency rate to be 56%. The relatively higher attrition rate of the grafts in the later stage might be ascribed to the smaller caliber of the coronary artery and saphenous vein, to possible inflammatory changes in both the graft and coronary arteries, or to unknown metabolic differences between children and adults.

Cardiac surgery of eight children with Kawasaki disease (mucocutaneous lymph node syndrome)

The coronary arterial lesions of Kawasaki disease are characterized by multiple stenoses and aneurysms, which might lead to myocardial ischemia, myocardial infarction, mitral insufficiency due to ischemic papillary muscle dysfunction, ventricular aneurysm, etc. Eight children aged 6 to 13 years with Kawasaki disease underwent surgical treatments. These were coronary bypass surgery, coronary bypass surgery combined with right coronary aneurysmectomy and coronary bypass surgery combined with left ventricular aneurysmectomy. The postoperative course was smooth in all the patients. The selective angiography performed 1 month after the operation revealed the patency rate of 85% of the bypass grafts. However, 1 patient died suddenly during strenuous exercise 3 years after the surgery. Several points to be considered in the aortocoronary bypass in the patients with Kawasaki disease are discussed. These include the unknown fate of saphenous vein grafts and the possibility of higher incidences of graft failure in the growing children. Since the long-term postoperative results are as yet not fully understood, close follow-up of the patients treated by aortocoronary bypass surgery would be mandatory.

Surgical experience with coronary arterial sequelae of Kawasaki disease in children

The coronary arterial sequelae due to Kawasaki disease have been treated surgically in five children ranged from 6 to 9 years old. The procedures were aortocoronary bypass surgery in all cases, coronary artery aneurysmectomy in one case and left ventricular aneurysmectomy in one case. The early results of operated cases have been good with the graft patency of 86% confirmed by angiography one month after surgery. The characteristic features of coronary artery damage in patients with Kawasaki disease are coronary artery aneurysms, which manifest wall irregularity, thrombus, calcification and stenosis. The significant stenosis of coronary artery could often be observed at the inlet or outlet of the aneurysm in major coronary artery branches. Although the early results of aortocoronary bypass surgery in the children with Kawasaki disease have been good, long-term follow up is mandatory to investigate the status of autogenous saphenous vein grafted in children.