Shuji Kubo

Endothelial Cells Support Survival, Proliferation, and Neuronal Differentiation of Transplanted Adult Ischemia‐Induced Neural Stem/Progenitor Cells After Cerebral Infarction

Transplantation of neural stem cells (NSCs) has been proposed as a therapy for a range of neurological disorders. To realize the potential of this approach, it is essential to control survival, proliferation, migration, and differentiation of NSCs after transplantation. NSCs are regulated in vivo, at least in part, by their specialized microenvironment or “niche.” In the adult central nervous system, neurogenic regions, such as the subventricular and subgranular zones, include NSCs residing in a vascular niche with endothelial cells. Although there is accumulating evidence that endothelial cells promote proliferation of NSCs in vitro, there is no description of their impact on transplanted NSCs. In this study, we grafted cortex‐derived stroke‐induced neural stem/progenitor cells, obtained from adult mice, onto poststroke cortex in the presence or absence of endothelial cells, and compared survival, proliferation, and neuronal differentiation of the neural precursors in vivo. Cotransplantation of endothelial cells and neural stem/progenitor cells increased survival and proliferation of ischemia‐induced neural stem/progenitor cells and also accelerated neuronal differentiation compared with transplantation of neural precursors alone. These data indicate that reconstitution of elements in the vascular niche enhances transplantation of adult neural progenitor cells. STEM CELLS 2009;27:2185–2195

Bone Marrow Mononuclear Cells Promote Proliferation of Endogenous Neural Stem Cells Through Vascular Niches After Cerebral Infarction

Increasing evidence shows that administration of bone marrow mononuclear cells (BMMCs) is a potential treatment for various ischemic diseases, such as ischemic stroke. Although angiogenesis has been considered primarily responsible for the effect of BMMCs, their direct contribution to endothelial cells (ECs) by being a functional elements of vascular niches for neural stem/progenitor cells (NSPCs) has not been considered. Herein, we examine whether BMMCs affected the properties of ECs and NSPCs, and whether they promoted neurogenesis and functional recovery after stroke. We compared i.v. transplantations 1 × 106 BMMCs and phosphate‐buffered saline in mice 2 days after cortical infarction. Systemically administered BMMCs preferentially accumulated at the postischemic cortex and peri‐infarct area in brains; cell proliferation of ECs (angiogenesis) at these regions was significantly increased in BMMCs‐treated mice compared with controls. We also found that endogenous NSPCs developed in close proximity to ECs in and around the poststroke cortex and that ECs were essential for proliferation of these ischemia‐induced NSPCs. Furthermore, BMMCs enhanced proliferation of NSPCs as well as ECs. Proliferation of NSPCs was suppressed by additional treatment with endostatin (known to inhibit proliferation of ECs) following BMMCs transplantation. Subsequently, neurogenesis and functional recovery were also promoted in BMMCs‐treated mice compared with controls. These results suggest that BMMCs can contribute to the proliferation of endogenous ischemia‐induced NSPCs through vascular niche regulation, which includes regulation of endothelial proliferation. In addition, these results suggest that BMMCs transplantation has potential as a novel therapeutic option in stroke treatment. STEM CELLS 2010;28:1292–1302

Isolation and characterization of neural stem/progenitor cells from post-stroke cerebral cortex in mice

The CNS has the potential to marshal strong reparative mechanisms, including activation of endogenous neurogenesis, after a brain injury such as stroke. However, the response of neural stem/progenitor cells to stroke is poorly understood. Recently, neural stem/progenitor cells have been identified in the cerebral cortex, as well as previously recognized regions such as the subventricular or subgranular zones of the hippocampus, suggesting that a contribution of cortex‐derived neural stem/progenitor cells may repair ischemic lesions of the cerebral cortex. In the present study, using a highly reproducible murine model of cortical infarction, we have found nestin‐positive cells in the post‐stroke cerebral cortex, but not in the non‐ischemic cortex. Cells obtained from the ischemic core of the post‐stroke cerebral cortex formed neurosphere‐like cell clusters expressing nestin; such cells had the capacity for self‐renewal and differentiated into electrophysiologically functional neurons, astrocytes and myelin‐producing oligodendrocytes. Nestin‐positive cells from the stroke‐affected cortex migrated into the peri‐infarct area and differentiated into glial cells in vivo. Although we could not detect differentiation of nestin‐positive cells into neurons in vivo, our current observations indicate that endogenous neural stem/progenitors with the potential to become neurons can develop within post‐stroke cerebral cortex.

Ischemia-Induced Neural Stem/Progenitor Cells in the Pia Mater Following Cortical Infarction

Increasing evidence shows that neural stem/progenitor cells (NSPCs) can be activated in the nonconventional neurogenic zones such as the cortex following ischemic stroke. However, the precise origin, identity, and subtypes of the ischemia-induced NSPCs (iNSPCs), which can contribute to cortical neurogenesis, is currently still unclear. In our present study, using an adult mouse cortical infarction model, we found that the leptomeninges (pia mater), which is widely distributed within and closely associated with blood vessels as microvascular pericytes/perivascular cells throughout central nervous system (CNS), have NSPC activity in response to ischemia and can generate neurons. These observations indicate that microvascular pericytes residing near blood vessels that are distributed from the leptomeninges to the cortex are potential sources of iNSPCs for neurogenesis following cortical infarction. In addition, our results propose a novel concept that the leptomeninges, which cover the entire brain, have an important role in CNS restoration following brain injury such as stroke.

Brain Vascular Pericytes Following Ischemia Have Multipotential Stem Cell Activity to Differentiate Into Neural and Vascular Lineage Cells

Brain vascular pericytes (PCs) are a key component of the blood‐brain barrier (BBB)/neurovascular unit, along with neural and endothelial cells. Besides their crucial role in maintaining the BBB, increasing evidence shows that PCs have multipotential stem cell activity. However, their multipotency has not been considered in the pathological brain, such as after an ischemic stroke. Here, we examined whether brain vascular PCs following ischemia (iPCs) have multipotential stem cell activity and differentiate into neural and vascular lineage cells to reconstruct the BBB/neurovascular unit. Using PCs extracted from ischemic regions (iPCs) from mouse brains and human brain PCs cultured under oxygen/glucose deprivation, we show that PCs developed stemness presumably through reprogramming. The iPCs revealed a complex phenotype of angioblasts, in addition to their original mesenchymal properties, and multidifferentiated into cells from both a neural and vascular lineage. These data indicate that under ischemic/hypoxic conditions, PCs can acquire multipotential stem cell activity and can differentiate into major components of the BBB/neurovascular unit. Thus, these findings support the novel concept that iPCs can contribute to both neurogenesis and vasculogenesis at the site of brain injuries. Stem Cells 2015;33:1962–1974

Complete regression of human malignant mesothelioma xenografts following local injection of midkine promoter-driven oncolytic adenovirus.

Malignant mesothelioma is a highly aggressive tumor with poor prognosis. We hypothesized that the tumor‐specific midkine (Mdk) promoter could confer transcriptional targeting to oncolytic adenoviruses for effective treatment of malignant mesothelioma.

Replication-competent retrovirus vector-mediated prodrug activator gene therapy in experimental models of human malignant mesothelioma

Replication-competent retrovirus (RCR) vectors have been shown to achieve significantly enhanced tumor transduction efficiency and therapeutic efficacy in various cancer models. In the present study, we investigated RCR vector-mediated prodrug activator gene therapy for the treatment of malignant mesothelioma, a highly aggressive tumor with poor prognosis. RCR-GFP vector expressing the green fluorescent protein marker gene successfully infected and efficiently replicated in human malignant mesothelioma cell lines, as compared with non-malignant mesothelial cells in vitro. In mice with pre-established subcutaneous tumor xenografts, RCR-GFP vector showed robust spread throughout entire tumor masses after intratumoral administration. Next, RCR-cytosine deaminase (RCR-CD), expressing the yeast CD prodrug activator gene, showed efficient transmission of the prodrug activator gene associated with replicative spread of the virus, resulting in efficient killing of malignant mesothelioma cells in a prodrug 5-fluorocytosine (5FC)-dose dependent manner in vitro. After a single intratumoral injection of RCR-CD followed by intraperitoneal administration of 5FC, RCR vector-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous tumor growth, and significantly prolonged survival in the disseminated peritoneal model of malignant mesothelioma. These data indicate the potential utility of RCR vector-mediated prodrug activator gene therapy in the treatment of malignant mesothelioma.

Modulation of innate immunity by IL-18

IL-18 is expressed in various reproductive organs and its expression in the uterus fluctuates in linkage with menstrual cycle, implantation, pregnancy and delivery. However, the roles of this cytokine in reproduction remain obscure. IL-18 is a pleiotropic cytokine and exerts apparently complicated and sometimes paradoxical functions in immune and inflammatory responses, and a consensus understanding of its action has not been attained. Recent investigations reveal that IL-18 activates anti-apoptotic signals and promotes both survival and proliferation of activated lymphocytes as well as various cells exposed to different stressors. Especially, IL-18 enhances the expansion of NK and gammadelta T cells isolated from the circulation and stimulated in various ways. The expansion of gammadelta T cells, stimulated by zoledronate and IL-2, was strongly promoted by exogenous IL-18 and was inhibited by neutralizing anti-IL-18 receptor antibody. The expansion of gammadelta T cells was coincident with an increased number of CD11c+ cells. The gammadelta T cells that expanded in the presence of zoledronate, IL-2 and IL-18 exhibited the phenotype of effector memory cells characterized as CD44+ CD27- CD45RA- cells. In addition, they expressed NKG2D, perforin, CD94, CD25 and CD122, and 30-40% of them were positive for CD56. Incubation of expanded gammadelta T cells with IL-18 induced production of GM-CSF, IFNgamma and TNFalpha at much higher levels than those incubated without IL-18. They showed strong cytotoxicity against tumor cells, including mesothelioma cells, and inhibited growth of mesothelioma xenografts in mice. These observations suggest that IL-18 can efficiently promote expansion of gammadelta T cells with potent cytotoxicity.

Enhanced antitumor efficacy of fiber-modified, midkine promoter-regulated oncolytic adenovirus in human malignant mesothelioma

Oncolytic virotherapy using adenoviruses has potential for therapeutic benefits in malignant mesothelioma. However, the downregulation of coxsackie virus/adenovirus receptor (CAR) expression is frequently a critical rate‐limiting factor that impedes the effectiveness of adenovirus serotype 5 (Ad5)‐based vectors in many cancer types. We evaluated CAR (Ad5 receptor) and CD46 (adenovirus serotype 35 [Ad35] receptor) expression in six human malignant mesothelioma cell lines. Very low CAR expression was observed in MSTO‐211H and NCI‐H2052 cells, whereas the other cell lines showed strong expression. In contrast, CD46 was highly expressed in all mesothelioma cell lines. On this basis, we replaced the CAR binding sequence of Ad5 with the CD46 binding sequence of Ad35 in the replication‐defective adenoviruses and the tumor‐specific midkine promoter‐regulated oncolytic adenoviruses. By this fiber modification, the infectivity, virus progeny production, and in vitro cytocidal effects of the adenoviruses were significantly enhanced in low CAR‐expressing MSTO‐211H and NCI‐H2052 cells, also resulting in similar or even higher levels in high CAR‐expressing mesothelioma cell lines. In MSTO‐211H xenograft models, the fiber‐modified oncolytic adenovirus significantly enhanced antitumor effect compared to its equivalent Ad5‐based vector. Our data demonstrate that Ad35 fiber modification of binding tropism in a midkine promoter‐regulated oncolytic Ad5 vector confers transductional targeting to oncolytic adenoviruses, thereby facilitating more effective treatment of malignant mesothelioma.

SAP155-Mediated Splicing of FUSE-Binding Protein-Interacting Repressor Serves as a Molecular Switch for c-myc Gene Expression

The Far UpStream Element (FUSE)-binding protein-interacting repressor (FIR), a c-myc transcriptional suppressor, is alternatively spliced removing the transcriptional repression domain within exon 2 (FIRΔexon2) in colorectal cancers. SAP155 is a subunit of the essential splicing factor 3b (SF3b) subcomplex in the spliceosome. This study aims to study the significance of the FIR–SAP155 interaction for the coordination of c-myc transcription, pre-mRNA splicing, and c-Myc protein modification, as well as to interrogate FIRΔexon2 for other functions relating to altered FIR pre-mRNA splicing. Knockdown of SAP155 or FIR was used to investigate their reciprocal influence on each other and on c-myc transcription, pre-mRNA splicing, and protein expression. Pull down from HeLa cell nuclear extracts revealed the association of FIR, FIRΔexon2, and SF3b subunits. FIR and FIRΔexon2 were coimmunoprecipitated with SAP155. FIR and FIRΔexon2 adenovirus vector (Ad–FIR and Ad–FIRΔexon2, respectively) were prepared to test for their influence on c-myc expression. FIR, SAP155, SAP130, and c-myc were coordinately upregulated in human colorectal cancer. These results reveal that SAP155 and FIR/FIRΔexon2 form a complex and are mutually upregulating. Ad–FIRΔexon2 antagonized Ad–FIR transcriptional repression of c-myc in HeLa cells. Because FIRΔexon2 still carries RRM1 and RRM2 and binding activity to FUSE, it is able to displace repression competent FIR from FUSE in electrophoretic mobility shift assays, thus thwarting FIR-mediated transcriptional repression by FUSE. Thus aberrant FIRΔexon2 production in turn sustained c-Myc expression. In conclusion, altered FIR and c-myc pre-mRNA splicing, in addition to c-Myc expression by augmented FIR/FIRΔexon2–SAP155 complex, potentially contribute to colorectal cancer development. Mol Cancer Res; 10(6); 787–99. ©2012 AACR.