Shigeharu Yabe

Pdx1-transfected adipose tissue-derived stem cells differentiate into insulin-producing cells in vivo and reduce hyperglycemia in diabetic mice

Insulin-dependent diabetes mellitus (IDDM) is characterized by the rapid development of potentially severe metabolic abnormalities resulting from insulin deficiency. The transplantation of insulin-producing cells is a promising approach for the treatment of IDDM. The transcription factor pancreatic duodenal homeobox 1 (Pdx1) plays an important role in the differentiation of pancreatic beta cells. In this study, the human Pdx1 gene was transduced and expressed in murine adipose tissue-derived stem cells (ASCs). To evaluate pancreatic repair, we used a mouse model of pancreatic damage resulting in hyperglycemia, which involves injection of mice with streptozotocin (STZ). STZ-treated mice transplanted with Pdx1-transduced ASCs (Pdx1-ASCs) showed significantly decreased blood glucose levels and increased survival, when compared with control mice. While stable expression of Pdx1 in ASCs did not induce the pancreatic phenotype in vitro in our experiment, the transplanted stem cells became engrafted in the pancreas, wherein they expressed insulin and C-peptide, which is a marker of insulin-producing cells. These results suggest that Pdx1-ASCs are stably engrafted in the pancreas, acquire a functional beta-cell phenotype, and partially restore pancreatic function in vivo. The ease and safety associated with extirpating high numbers of cells from adipose tissues support the applicability of this system to developing a new cell therapy for IDDM.

Cloning and characterization of the T‐box gene Tbx6 in Xenopus laevis

Tbx6 is a member of the T‐box gene family. Studies of knockout mice indicate that Tbx6 is involved in somite differentiation. In the present study, we cloned Tbx6 from another vertebrate species, namely Xenopus laevis, and studied its roles in development. The expression of Tbx6 in Xenopus started from the early gastrula stage, reached a peak during the late gastrula to neurula stages and then declined. Initial expression of Tbx6 was observed in the paraxial mesoderm during the gastrula stage. The Tbx6‐expressing region spread anteriorly and ventrally in the neurula stage. In the tailbud stage, the area of expression shrank caudally and was finally restricted to the tip of the tailbud. Overexpression of Tbx6 mRNA in dorsal blastomeres caused atrophy of the neural tube and inhibited differentiation of the notochord. Animal cap explants overexpressing Tbx6 or Tbx6VP16 mRNA, but not Tbx6EnR mRNA, differentiated mainly into ventral mesodermal tissues. This suggests that Tbx6 is a transcriptional activator. Higher doses of Tbx6 or Tbx6VP16 mRNA caused hardly any muscular differentiation. However, coinjection of Tbx6 mRNA with noggin mRNA elicited marked muscle differentiation. These results suggest that Tbx6 is implicated in ventral mesoderm specification but is involved in muscle differentiation when acting together with the dorsalizing factor noggin.

pMesogenin1 and 2 function directly downstream of Xtbx6 in Xenopus somitogenesis and myogenesis

T‐box transcription factor tbx6 and basic‐helix‐loop‐helix transcription factor pMesogenin1 are reported to be involved in paraxial mesodermal differentiation. To clarify the relationship between these genes in Xenopus laevis, we isolated pMesogenin2, which showed high homology with pMesogenin1. Both pMesogenin1 and 2 appeared to be transcriptional activators and were induced by a hormone‐inducible version of Xtbx6 without secondary protein synthesis in animal cap assays. The pMesogenin2 promoter contained three potential T‐box binding sites with which Xtbx6 protein was shown to interact, and a reporter gene construct containing these sites was activated by Xtbx6. Xtbx6 knockdown reduced pMesogenin1 and 2 expressions, but not vice versa. Xtbx6 and pMesogenin1 and 2 knockdowns caused similar phenotypic abnormalities including somite malformation and ventral body wall muscle hypoplasia, suggesting that Xtbx6 is a direct regulator of pMesogenin1 and 2, which are both involved in somitogenesis and myogenesis including that of body wall muscle in Xenopus laevis. Developmental Dynamics 237:3749–3761, 2008.

Paraxial T-box genes, Tbx6 and Tbx1, are required for cranial chondrogenesis and myogenesis.

We previously reported that Tbx6, a T-box transcription factor, is required for the differentiation of ventral body wall muscle and for segment formation and somitic muscle differentiation. Here, we show that Tbx6 is also involved, at later stages, in cartilage differentiation from the cranial neural crest and head muscle development. In Tbx6 knockdown embryos, the cranial neural crest was shown to be correctly induced at the border of the neural plate and migrated in a slightly delayed manner, but finally reached positions in the pharyngeal arches nearly similar to those in the normal embryos as revealed by in situ hybridization and the neural crest-transplantation experiments. However, the neural crest cells failed to maintain Sox9 expression. Tbx6 knockdown also reduced the expression of Tbx1, another T-box gene expressed in more anterior paraxial structures. Tbx1 knockdown caused phenotypes milder but similar to those of Tbx6 morphants, including reduced formation of head muscles and cartilages, and attenuated Sox9 expression. Furthermore, the phenotypes caused by Tbx6 knockdown were partially rescued by Tbx1 plasmid injection. These results suggest that Tbx6 is involved in the cranial cartilage and head muscle development by regulating anterior paraxial genes such as Tbx1 and Sox9.

Establishment of maturity-onset diabetes of the young-induced pluripotent stem cells from a Japanese patient

Maturity‐onset diabetes of the young (MODY) is a heterozygous monogenic diabetes; more than 13 disease genes have been identified. However, the pathogenesis of MODY is not fully understood, because the pancreatic β‐cells of the patients are inaccessable. Therefore, we attempted to establish MODY patient‐derived induced pluripotent stem cells (MODY‐iPS) cells to investigate the pathogenic mechanism of MODY by inducing pancreatic β‐cells. We established MODY5‐iPS cells from a Japanese patient with MODY5 (R177X), and confirmed that MODY5‐iPS cells possessed the characteristics of pluripotent stem cells. In the course of differentiation from MODY5‐iPS cells into pancreatic β‐cells, we examined the disease gene, HNF1B messenger ribonucleic acid. We found that the amount of R177X mutant transcripts was much less than that of wild ones, but they increased after adding cycloheximide to the medium. These results suggest that these R177X mutant messenger ribonucleic acids are disrupted by nonsense‐mediated messenger ribonucleic acid decay in MODY‐iPS cells during the developmental stages of pancreatic β‐cells.

Efficient Generation of Functional Pancreatic β Cells from Human iPS Cells.

Insulin‐secreting cells have been generated from human embryonic or induced pluripotent stem cells (iPSCs) by mimicking developmental processes. However, these cells do not always secrete glucose‐responsive insulin, one of the most important characteristics of pancreatic β‐cells. We focused on the importance of endodermal differentiation from human iPSCs in order to obtain functional pancreatic β‐cells.

Efficient generation of functional pancreatic β-cells from human induced pluripotent stem cells.

Insulin‐secreting cells have been generated from human embryonic or induced pluripotent stem cells (iPSCs) by mimicking developmental processes. However, these cells do not always secrete glucose‐responsive insulin, one of the most important characteristics of pancreatic β‐cells. We focused on the importance of endodermal differentiation from human iPSCs in order to obtain functional pancreatic β‐cells.

Safety assessment of bone marrow derived MSC grown in platelet-rich plasma

The injection of endothelial progenitor cells and mononuclear cells derived from bone marrow at the ischemic region of peripheral artery disease patients is reported to be effective for therapeutic angiogenesis; however, these cell therapies require large amounts of bone marrow to obtain sufficient numbers of cells. To solve this problem, we attempted to culture bone-marrow-derived mesenchymal stem cells (BM-MSC), which are supposed to secrete several cytokines that promote angiogenesis. We also focused on using platelet-rich plasma (PRP) as a supplement for cell culture instead of fetal bovine serum. Human BM-MSC obtained from healthy volunteers expanded rapidly when cultured with 10% PRP prepared from their own blood. FACS analysis revealed that these cultured human MSC were homogeneous populations, and chromosomal analysis showed a normal karyotype. Moreover, the angiogenetic effect was apparent two weeks after human BM-MSC were injected into the ischemic muscle in SCID mice. Tumor formation was not detected three months after injection into SCID mice either subcutaneously or intramuscularly. To simulate clinical settings, canine BM-MSC were grown with canine PRP and injected into their ischemic muscles. We confirmed that donor cells existed in situ two and six weeks after operation without any side effects. These results suggest that cultured human BM-MSC can be a promising cell source for therapeutic angiogenesis.

Suppressive Effects of Mesenchymal Stem Cells in Adipose Tissue on Allergic Contact Dermatitis

Background Allergic contact dermatitis (ACD), which is accelerated by interferon (IFN)-γ and suppressed by interleukin (IL)-10 as regulators, is generally self-limited after removal of the contact allergen. Adipose tissue-derived multipotent mesenchymal stem cells (ASCs) potentially exert immunomodulatory effects. Considering that subcutaneous adipose tissue is located close to the site of ACD and includes mesenchymal stem cells (MSCs), the MSCs in adipose tissue could contribute to the self-limiting course of ACD. Objective The aims of the present study were to elucidate the effects of MSCs in adipose tissue on ACD and to examine any cytokine-mediated mechanisms involved. Methods Ear thickness in a C57BL/6 mouse model of ACD using contact hypersensitivity (CHS) elicited by 2,4,6-trinitro-1-chlorobenzene was evaluated as a marker of inflammation level. Five and nine mice were injected with ASCs and phosphate-buffered saline (PBS), respectively. After ASC or PBS injection, real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were performed. Results Histology showed that CHS was self-limited and ear thickness was suppressed by ASCs in a dose-dependent manner. IFN-γ expression in the elicited skin site and regional lymph nodes was significantly lower in ASC-treated mice than in control mice. IL-10 expression did not differ between treated and control mice. The suppressive effects of ASCs on CHS response did not differ between IL-10 knock-out C57BL/6 mice and wild-type mice. Conclusion The present findings suggest that MSCs in adipose tissue may contribute to the self-limiting course of ACD through decreased expression of IFN-γ, but not through increased expression of IL-10.

Murine Insulinoma Cell-Conditioned Medium with ÃÂETA2/Neurod1 Transduction Efficiently Induces the Differentiation of Adipose-DerivedMesenchymal Stem Cells into ò-Like Cells both In Vitro and In Vivo

Background: Mesenchymal stem cells (MSCs), including adipose tissue-derived mesenchymal stem cells (ADSCs), are multipotent and can differentiate into various cell types, including pancreatic β cells. Therefore, ADSCs present a potential cell source for the treatment of type 1 diabetes mellitus (T1DM). However, current in vitro protocols are insufficient to induce fully matured insulin-producing β cells. In this study, we assessed the effectiveness of overexpression of ΒETA2 (NeuroD1), a member of the basic helix–loop–helix transcription factor family, with murine insulinoma cell line-derived conditioned medium (MIN6-CM) to improve the differentiation capacity of ADSCs into insulin-producing cells. Method: Murine ADSCs were isolated from C57BL/6 mice, transduced with several transcriptional factors (TFs), and stable transfectants were established. MIN6-CM was prepared. Syngeneic recipient mice were rendered diabetic by a single injection of streptozotocin, and differentiated cells were transplanted under the kidney capsule of recipient mice. Next, blood glucose levels were monitored. Results: CM alone was sufficient to induce insulin mRNA expression in vitro. However, other TFs were not detected. ADSCs cultured with MIN6-CM induced insulin expressions in vitro, but other β cell-related TFs were been detected. However, BETA2 transduction in MIN6-CM resulted in robust expression of multiple β cell phenotypic markers. Moreover, insulin content analysis revealed insulin protein expression in vitro. Furthermore, in vivo transplant studies revealed the effectiveness of the simultaneous use of BETA2 transduction with the CM. Conclusion: These results suggest that the balance of cytokines and growth factors in addition to gene manipulation would benefit the efficient differentiation of ADSCs into pancreatic β cells. Our technology could provide a path to β cell differentiation and novel cell replacement-based therapies for T1DM.