Kiminori Nakamura

Antitumor effect of genetically engineered mesenchymal stem cells in a rat glioma model

The prognosis of patients with malignant glioma is extremely poor, despite the extensive surgical treatment that they receive and recent improvements in adjuvant radio- and chemotherapy. In the present study, we propose the use of gene-modified mesenchymal stem cells (MSCs) as a new tool for gene therapy of malignant brain neoplasms. Primary MSCs isolated from Fischer 344 rats possessed excellent migratory ability and exerted inhibitory effects on the proliferation of 9L glioma cell in vitro. We also confirmed the migratory capacity of MSCs in vivo and showed that when they were inoculated into the contralateral hemisphere, they migrated towards 9L glioma cells through the corpus callosum. MSCs implanted directly into the tumor localized mainly at the border between the 9L tumor cells and normal brain parenchyma, and also infiltrated into the tumor bed. Intratumoral injection of MSCs caused significant inhibition of 9L tumor growth and increased the survival of 9L glioma-bearing rats. Gene-modification of MSCs by infection with an adenoviral vector encoding human interleukin-2 (IL-2) clearly augmented the antitumor effect and further prolonged the survival of tumor-bearing rats. Thus, gene therapy employing MSCs as a targeting vehicle would be promising as a new therapeutic approach for refractory brain tumor.

Mesenchymal stem cells (MSC) as therapeutic cytoreagents for gene therapy

We developed human mesenchymal stem cell (MSC) lines that could differentiate into various tissue cells including bone, neural cells, bone marrow (BM) stromal cells supporting the growth of hematopoietic stem cell (HSC), and so‐called ‘tumor stromal cells’ mixing with tumor cells. We investigated the applicability of MSC as therapeutic cell transplanting reagents (cytoreagents). Telomerized human BM derived stromal cells exhibited a prolonged lifespan and supported the growth of hematopoietic clonogenic cells. The gene transfer of Indian hedgehog (Ihh) remarkably enhanced the HSC expansion supported by the human BM stromal cells. Gene‐modified MSC are useful as therapeutic tools for brain tissue damage (e.g. brain infarction) and malignant brain neoplasms. MSC transplantation protected the brain tissue from acute ischemic damage in the midcerebral artery occlusion (MCAO) animal model. Brain‐derived neurotrophic factor (BDNF)‐gene transduction further enhanced the protective efficacy against the ischemic damage. MSC possessed excellent migratory ability and exerted inhibitory effects on the proliferation of glioma cells. Gene‐modification of MSC with therapeutic cytokines clearly augmented the antitumor effect and prolonged the survival of tumor‐bearing animals. Gene therapy employing MSC as a tissue‐protecting and targeting cytoreagent would be a promising approach. (Cancer Sci 2005; 96: 149–156)

Graft-versus-host disease disrupts intestinal microbial ecology by inhibiting Paneth cell production of α-defensins

Allogeneic hematopoietic stem cell transplantation (SCT) is a curative therapy for various hematologic disorders. Graft-versus-host disease (GVHD) and infections are the major complications of SCT, and their close relationship has been suggested. In this study, we evaluated a link between 2 complications in mouse models. The intestinal microbial communities are actively regulated by Paneth cells through their secretion of antimicrobial peptides, α-defensins. We discovered that Paneth cells are targeted by GVHD, resulting in marked reduction in the expression of α-defensins, which selectively kill noncommensals, while preserving commensals. Molecular profiling of intestinal microbial communities showed loss of physiologic diversity among the microflora and the overwhelming expansion of otherwise rare bacteria Escherichia coli, which caused septicemia. These changes occurred only in mice with GVHD, independently on conditioning-induced intestinal injury, and there was a significant correlation between alteration in the intestinal microbiota and GVHD severity. Oral administration of polymyxin B inhibited outgrowth of E coli and ameliorated GVHD. These results reveal the novel mechanism responsible for shift in the gut flora from commensals toward the widespread prevalence of pathogens and the previously unrecognized association between GVHD and infection after allogeneic SCT.

Efficient BMP2 gene transfer and bone formation of mesenchymal stem cells by a fiber-mutant adenoviral vector

Strategies using mesenchymal stem cell (MSC)-mediated gene therapy have been developed to improve bone healing. However, transduction efficiency into MSCs by each vector is not always high. To overcome this problem, we used a modified adenoviral vector (Adv-F/RGD) with an RGD-containing peptide in the HI loop of the fiber knob domain of adenovirus type 5 (Ad5). Transduction efficiency into bone marrow-derived MSCs with Adv-F/RGD increased 12-fold compared with a vector containing the wild-type fiber (Adv-F/wt) by beta-galactosidase chemiluminescent assay. As a next step, we constructed AxCAhBMP2-F/RGD and AxCAhBMP2-F/wt carrying human bone morphogenetic protein 2 (BMP2). At the same multiplicity of infection, MSCs infected with AxCAhBMP2-F/RGD produced higher amounts of BMP2 than cells infected with AxCAhBMP2-F/wt, and also differentiated towards the osteogenic lineage more efficiently in vitro. Furthermore, using ex vivo gene transduction, we evaluated the potential for ectopic bone formation by the transduced MSCs in vivo. Transduction with AxCAhBMP2-F/RGD exhibited greatly enhanced new bone formation. These data suggest that Adv-F/RGD is useful for introducing foreign genes into MSCs and that it will be a powerful gene therapy tool for bone regeneration and other tissue engineering.

Telomerized human multipotent mesenchymal cells can differentiate into hematopoietic and cobblestone area-supporting cells.

OBJECTIVE To compare the hematopoietic support provided by telomerized human mesenchymal stem cells (MSCs) and telomerized MSC-derived stromal cells. METHODS We transfected the human telomerase catalytic subunit (hTERT) gene into primary MSCs to establish hTERT-transduced MSCs (hTERT-MSCs). Stromal induction of hTERT-MSCs was performed by replacing the culture medium with Dexter-type culture medium. Hematopoietic support was examined by coculture with cord blood CD34(+) cells. RESULTS The hTERT-MSCs were morphologically identical with the primary MSCs and expressed surface antigens including CD105, CD73, and CD166. hTERT-MSCs showed a similar doubling time as primary MSCs and continued to proliferate to over 80 population doublings (PD), although the primary MSCs underwent crisis in vitro at 16 PD. The osteogenic, chondrogenic, adipogenic, neurogenic, and stromal differentiation potential of hTERT-MSCs were maintained up to at least 40 PD. The degree of expansion of CD34(+) cells and total number of colony-forming units in culture (CFU-C) upon 12-day coculture with the hTERT-MSC-derived stromal cells were nearly the same as those upon 12-day coculture with hTERT-MSCs (CD34, 33.0-fold+/-2.8-fold vs 36.1-fold+/-1.7-fold of the initial cell number; CFUs, 344.4-fold+/-62.5-fold vs 239.3-fold+/-87.0-fold; CFU-mix, 368.4-fold+/-113.7-fold vs 341.3-fold+/-234.3-fold). However, on day 18 of coculture, the number of cobblestone areas (CA) observed beneath the stromal cells was 15 times higher than that beneath hTERT-MSCs (CA, 146.9+/-54.6 vs 9.4+/-8.1, p<0.01). CONCLUSION Stromal induction of hTERT-MSCs exclusively enhanced the support of CA formation provided by hTERT-MSCs. Our human hTERT-MSCs will be useful for elucidating the mechanism of the formation of CAs.

Adenoviral delivered angiopoietin-1 reduces the infarction and attenuates the progression of cardiac dysfunction in the rat model of acute myocardial infarction

In acute myocardial infarction (AMI), prognosis and mortality rate are closely related to the infarct size and the progression of postinfarction cardiac failure. Angiogenic gene therapy has presented a new approach for the treatment of AMI. Angiopoietin-1 (Ang1) is a critical angiogenic factor for vascular maturation and enhances vascular endothelial growth factor (VEGF)-induced angiogenesis in a complementary manner. We hypothesized that gene therapy using Ang1 for AMI might promote angiogenesis cooperatively with intrinsic VEGF, since high concentrations of circulating VEGF have been reported in AMI. To evaluate our hypothesis, we employed a rat AMI model and adenoviral Ang1 (HGMW-approved gene symbol ANGPT1) gene transfer to the heart. A significant increase in capillary density and reduction in infarct sizes were noted in the infarcted hearts with adenoviral Ang1 gene treatment compared with control infarcted hearts treated with saline or adenoviral vector containing the beta-galactosidase gene. Furthermore, the Ang1 group showed significantly higher cardiac performance in echocardiography (55.0% of ejection fraction, P < 0.05 vs control) than the saline or adenoviral controls (36.0 or 40.5%, respectively) 4 weeks after myocardial infarction. The adenoviral delivery of Ang1 during the acute phase of myocardial infarction would be feasible to attenuate the progression of cardiac dysfunction in the rat model.

Wnt3/RhoA/ROCK signaling pathway is involved in adhesion-mediated drug resistance of multiple myeloma in an autocrine mechanism

Adhesion of myeloma cells to bone marrow stromal cells is now considered to play a critical role in chemoresistance. However, little is known about the molecular mechanism governing cell adhesion–mediated drug resistance (CAM-DR) of myeloma cells. In this study, we focused our interests on the implication of the Wnt signal in CAM-DR. We first screened the expression of Wnt family in myeloma cell lines and found that Wnt3 was overexpressed in all the myeloma cells examined. KMS-5 and ARH77, which highly expressed Wnt3 protein, tightly adhered to human bone marrow stromal cells, and accumulation of β-catenin and GTP-bounded RhoA was observed in these myeloma cell lines. Conversely, RPMI8226 and MM1S, which modestly expressed Wnt3 protein, rather weakly adhered to human bone marrow stromal. We then examined the relevance of Wnt3 expression to adhesive property to stromal cells and to CAM-DR of myeloma cells. KMS-5 and ARH-77 exhibited apparent CAM-DR against doxorubicin. This CAM-DR was significantly reduced by anti-integrin β1 antibody, anti-integrin α6 antibody and a Wnt-receptor competitor, secreted Frizzled-related protein-1, and Rho kinase inhibitor Y27632, but not by the specific inhibitor of canonical signaling (Dickkopf-1), indicating that Wnt-mediated CAM-DR that is dependent on integrin α6/β1 (VLA-6)–mediated attachment to stromal cells is induced by the Wnt/RhoA/Rho kinase pathway signal. This CAM-DR was also significantly reduced by Wnt3 small interfering RNA transfer to KMS-5. These results indicate that Wnt3 contributes to VLA-6–mediated CAM-DR via the Wnt/RhoA/ROCK pathway of myeloma cells in an autocrine manner. Thus, the Wnt3 signaling pathway could be a promising molecular target to overcome CAM-DR of myeloma cells. [Mol Cancer Ther 2007;6(6):1774–82]

Pre-administration of angiopoietin-1 followed by VEGF induces functional and mature vascular formation in a rabbit ischemic model

Angiopoietin‐1 (Ang1) and vascular endothelial growth factor (VEGF) play important roles in vascular formation and maturation, suggesting that the combination of these two would be a promising therapy for ischemia. However, it remains unclear what the best schedule of administration of these cytokines might be.

Bcl-xL Gene Transfer Inhibits Bax Translocation and Prolongs Cardiac Cold Preservation Time in Rats

Background—Apoptosis is an important cause of early graft loss after heart transplantation. Bcl-xL was reported to protect the heart against normothermic ischemia and reperfusion injury. In this study, we determined whether overexpression of Bcl-xL could inhibit tissue injury resulting from prolonged cold preservation followed by warm reperfusion of heart transplants. Methods and Results—Lewis rat hearts were transduced with an adenovirus vector harboring Bcl-xL cDNA (AxCAhBclxL) 4 days before collection of tissue. After preservation in University of Wisconsin solution at 4°C for 24 hours, the heart was either perfused with a Langendorff device ex vivo or used for heterotopic heart transplantation in vivo. Bcl-xL gene transfer significantly reduced the infarct size (23.0±2.6% versus 47.7±7.0% in saline control and 48.6±6.1% in vector control, P<0.01) after 2-hour reperfusion at 37°C with the Langendorff device and significantly decreased creatine kinase release (0.82±0.27 IU, versus 1.57±0.33 and 1.50±0.37 IU in saline and vector controls, respectively; P<0.05). In heart transplantation, overexpresson of Bcl-xL inhibited Bax translocation from the cytosol to the mitochondria, resulting in decreased cytochrome c release from the mitochondria; it also significantly decreased cardiac cell apoptosis and improved graft survival rate after long cold preservation, followed by warm reperfusion. Conclusions—Bcl-xL gene transfer inhibited the translocation of Bax and prolonged the cold preservation time of cardiac transplants. This may be a potential therapeutic method in clinical practice.

Bactericidal Activity of Mouse α-Defensin, Cryptdin-4 Predominantly Affects Noncommensal Bacteria

Mouse Paneth cell α-defensins, termed cryptdins, are secreted into the intestinal lumen, have microbicidal activity, and contribute to intestinal innate immunity. Among them, cryptdin-4 (Crp4) has the most potent microbicidal activity. In the intestinal lumen, commensal bacteria colonize and elicit beneficial effects in the host. However, the effects of Crp4 against commensal bacteria are poorly understood. Thus, we investigated the bactericidal activities of Crp4 against commensal bacteria compared to noncommensal bacteria. Oxidized Crp4 showed only minimal or no bactericidal activity against 8 out of 12 commensal bacterial species, including Bifidobacterium bifidum and Lactobacillus casei. We further addressed a role of the conserved disulfide bonds of Crp4 by analyzing reduced Crp4 (r-Crp4). r-Crp4 demonstrated significantly greater bactericidal activities against 7 of 12 commensal bacteria than did oxidized Crp4. Oxidized Crp4 and r-Crp4 elicited equivalently potent bactericidal activities against 11 of the 11 noncommensal bacteria tested, such as Salmonella enterica serovar Typhimurium,and against 5 of 12 commensal bacteria. Furthermore, when r-Crp4 was exposed to a processing enzyme of cryptdins, i.e. MMP-7, r-Crp4 was degraded and the bactericidal activities disappeared. These findings suggest that Crp4 has selective bactericidal activities against intestinal microbiota and that the activities are dependent on the disulfide bonds.