Shigeo Ookawara

Hes genes regulate size, shape and histogenesis of the nervous system by control of the timing of neural stem cell differentiation

Radial glial cells derive from neuroepithelial cells, and both cell types are identified as neural stem cells. Neural stem cells are known to change their competency over time during development: they initially undergo self-renewal only and then give rise to neurons first and glial cells later. Maintenance of neural stem cells until late stages is thus believed to be essential for generation of cells in correct numbers and diverse types, but little is known about how the timing of cell differentiation is regulated and how its deregulation influences brain organogenesis. Here, we report that inactivation of Hes1 and Hes5, known Notch effectors, and additional inactivation of Hes3 extensively accelerate cell differentiation and cause a wide range of defects in brain formation. In Hes-deficient embryos, initially formed neuroepithelial cells are not properly maintained, and radial glial cells are prematurely differentiated into neurons and depleted without generation of late-born cells. Furthermore, loss of radial glia disrupts the inner and outer barriers of the neural tube, disorganizing the histogenesis. In addition, the forebrain lacks the optic vesicles and the ganglionic eminences. Thus, Hes genes are essential for generation of brain structures of appropriate size, shape and cell arrangement by controlling the timing of cell differentiation. Our data also indicate that embryonic neural stem cells change their characters over time in the following order: Hes-independent neuroepithelial cells, transitory Hes-dependent neuroepithelial cells and Hes-dependent radial glial cells.

Disruption of Aquaporin-11 Produces Polycystic Kidneys following Vacuolization of the Proximal Tubule

ABSTRACT Aquaporin-11 (AQP11) has been identified with unusual pore-forming NPA (asparagine-proline-alanine) boxes, but its function is unknown. We investigated its potential contribution to the kidney. Immunohistochemistry revealed that AQP11 was localized intracellularly in the proximal tubule. When AQP11 was transfected in CHO-K1 cells, it was localized in intracellular organelles. AQP11-null mice were generated; these mice exhibited vacuolization and cyst formation of the proximal tubule. AQP11-null mice were born normally but died before weaning due to advanced renal failure with polycystic kidneys, in which cysts occupied the whole cortex. Remarkably, cyst epithelia contained vacuoles. These vacuoles were present in the proximal tubules of newborn mice. In 3-week-old mice, these tubules contained multiple cysts. Primary cultured cells of the proximal tubule revealed an endosomal acidification defect in AQP11-null mice. These data demonstrate that AQP11 is essential for the proximal tubular function. AQP11-null mice are a novel model for polycystic kidney diseases and will provide a new mechanism for cystogenesis.

Localization of mechanosensitive channel TRPV4 in mouse skin.

A transient receptor potential (TRP) family, TRPV4, is a calcium-permeable swell-activated channel, playing a role in cutaneous mechanosensation. To elucidate the localization in the mechanosensitive endings, we found with immunohistochemistry in mice that TRPV4 was expressed both by small (low threshold) and large (high threshold) dorsal root ganglia neurons. In addition to free nerve endings, TRPV4 was specifically located at cutaneous mechanosensory terminals co-localized with neurofilament 200, including Meissner, Merkel, penicillate and intraepidermal terminals but not including hair follicle palisades. The distribution suggests that the sensation of pressure by mechanosensitive TRPV4 channel is transmitted through A- as well as C-fiber.

Fluvastatin induces apoptosis in rat neonatal cardiac myocytes: A possible mechanism of statin-attenuated cardiac hypertrophy

Hydroxymethylglutaryl CoA (HMG-CoA) reductase inhibitors (statins) have been shown to reduce atherosclerotic cardiovascular mortality and morbidity. Recent evidence indicates that statins may also exert direct effects on vascular wall cells (including endothelial cells and smooth muscle cells) independently of their hypocholesterolemic properties. However, little is known about whether statins have direct effects on myocardium. The effect of lipophilic and hydrophilic statins (fluvastatin and pravastatin) on apoptosis and protein synthesis in rat neonatal cardiac myocytes was investigated. The presence of apoptosis was evaluated by morphologic criteria, electrophoresis of DNA fragments, 4″,6″-diamidine-2″-phenylindole (DAPI) staining, and TUNEL assay. Protein synthesis was measured by 3H-leucine incorporation into the cells. Fluvastatin, but not pravastatin, induced apoptosis in cardiac myocytes in a time- and dose-dependent manner. The pro-apoptotic effect of fluvastatin was reversed in the presence of mevalonate or geranylgeranyl-pyrophosphate (GGPP), but not in the presence of squalene. The addition of protein prenylation inhibitor perillic acid and Rho-kinase inhibitor Y27632 significantly increased apoptosis. Fluvastatin decreased RhoA protein in the membrane fraction, whereas there were no significant changes of the RhoA protein in the cytosol fraction. Interleukin-1&bgr;-stimulated 3H-leucine incorporation was completely inhibited by fluvastatin, but not by pravastatin. The findings suggest that fluvastatin induces apoptosis in cardiac myocytes via protein prenylation and the subsequent inhibition of Rho, and may play a role in the pathogenesis of cardiac hypertrophy and remodeling.

Rho-kinase dependent organization of stress fibers and focal adhesions in cultured fibroblasts.

The activation of Rho‐kinase is known to modulate the organization of the actin‐based cytoskeletal systems, including the formation of stress fibers and focal adhesions. Rho‐kinase likely plays a more crucial and complex role in the organization of actin‐based cytoskeletal systems than in that of myosin light chain kinase (MLCK). In order to understand the role of Rho‐kinase in the organization of stress fibers and focal adhesions, we treated cultured fibroblasts with a Rho‐kinase inhibitor and analyzed the stress fiber and focal adhesion organization under conventional fluorescence microscopy and replica electron microscopy. Some of the cells were transfected with GFP‐labeled paxillin, actin or α‐actinin, and the effects of the inhibitor were monitored in the living cells. The Rho‐kinase inhibitor caused disassembly of the stress fibers and focal adhesions in the central portion of the cell within 1 h. However, the stress fibers and focal adhesions located in the cell periphery were not as severely affected by the Rho‐kinase inhibitor. The time‐lapse video recording revealed that when these cells were washed with a fresh medium in order to remove the Rho‐kinase inhibitor, the stress fibers and focal adhesions located in the center of the cell gradually reorganized and, within 1.5–2 h, the cells completely recovered. This observation strongly suggests that the activation of Rho‐kinase plays an important role in the organization of the central stress fibers and focal adhesions.

Engraftment and tumor formation after allogeneic in utero transplantation of primate embryonic stem cells

Background. To achieve human embryonic stem (ES) cell-based transplantation therapies, allogeneic transplantation models of nonhuman primates would be useful. We have prepared cynomolgus ES cells genetically marked with the green fluorescent protein (GFP). The cells were transplanted into the allogeneic fetus, taking advantage of the fact that the fetus is so immunologically immature as not to induce immune responses to transplanted cells and that fetal tissue compartments are rapidly expanding and thus providing space for the engraftment. Methods. Cynomolgus ES cells were genetically modified to express the GFP gene using a simian immunodeficiency viral vector or electroporation. These cells were transplanted in utero with ultrasound guidance into the cynomolgus fetus in the abdominal cavity (n=2) or liver (n=2) at the end of the first trimester. Three fetuses were delivered 1 month after transplantation, and the other, 3 months after transplantation. Fetal tissues were examined for transplanted cell progeny by quantitative polymerase chain reaction and in situ polymerase chain reaction of the GFP sequence. Results. A fluorescent tumor, obviously derived from transplanted ES cells, was found in the thoracic cavity at 3 months after transplantation in one fetus. However, transplanted cell progeny were also detected (∼1%) without teratomas in multiple fetal tissues. The cells were solitary and indistinguishable from surrounding host cells. Conclusions. Transplanted cynomolgus ES cells can be engrafted in allogeneic fetuses. The cells will, however, form a tumor if they “leak” into an improper space such as the thoracic cavity.

Antiapoptotic Effect of Endothelin-1 in Rat Cardiomyocytes In Vitro

Abstract—Apoptosis of cardiac myocytes is thought to be a feature of many pathological disorders, including congestive heart failure (CHF) and ischemic heart disease (IHD). Because recent investigations indicate that endothelin-1 (ET-1) plays an important role in CHF and IHD, we investigated the effect of ET-1 on cardiomyocyte apoptosis. The presence of apoptosis in rat cardiomyocytes (H9c2 and neonatal) was evaluated by morphological criteria, electrophoresis of DNA fragments, 4′,6′-diamidine-2′-phenylindole staining, and TUNEL analysis. ET-1, but not angiotensin II, prevented apoptosis induced by serum deprivation via ETA receptors in a dose-dependent manner (1 to 100 nmol/L). ET-1 also prevented cytochrome c release from mitochondria to the cytosol. The use of specific pharmacological inhibitors demonstrated that the antiapoptotic effect of ET-1 was mediated through a tyrosine kinase pathway (genistein and AG490) but not through protein kinase C (PKC; calphostin C), mitogen-activated protein kinases (PD98059 and SB203580), or PKA (KT5270) pathways. Adenovirus-mediated gene transfer of kinase-inactive (KI) c-Src reversed the antiapoptotic effect of ET-1. We further investigated whether Bcl-xL, an antiapoptotic molecule, would be upregulated by using a luciferase-based reporter system. ET-1 upregulated Bcl-xL, and this upregulation was inhibited by genistein or AG490 but not by calphostin C. The experiments with KI mutants for various tyrosine kinases revealed that c-Src and Pyk2 (but not JAK1, Jak2, Syk, and Tec) are involved in ET-1–induced upregulation of Bcl-xL expression. These findings suggest that ET-1 prevents apoptosis in cardiac myocytes through the ETA receptor and the subsequent c-Src/Bcl-xL–dependent pathway.

Role of stress fibers and focal adhesions as a mediator for mechano-signal transduction in endothelial cells in situ

Fluid shear stress is the mechanical force generated by the blood flow which is applied over the apical surface of endothelial cells in situ. The findings of a recent study suggest that stress fibers and its associated focal adhesions play roles in mechano-signal transduction mechanism. Stress fibers are present along the apical and the basal portion of the endothelial cells. Endothelial cells respond to fluid shear stress and change their morphological characteristics in both their cell shape and cytoskeletal organization. Atherosclerosis is a common disease of the arteries and it occurs in areas around the branching site of blood vessels where the cells are exposed to low fluid shear stress. The organization of stress fibers and focal adhesions are strongly influenced by shear stress, and therefore the generation of atherosclerotic lesions seem to be associated with the cytoskeletal components of endothelial cells. This review describes the possible role of the cytoskeleton as a mechano-transducer in endothelial cells in situ.

Profile of new green fluorescent protein transgenic Jinhua pigs as an imaging source

Animal imaging sources have become an indispensable material for biological sciences. Specifically, gene-encoded biological probes serve as stable and high-performance tools to visualize cellular fate in living animals. We use a somatic cell cloning technique to create new green fluorescent protein (GFP)-expressing Jinhua pigs with a miniature body size, and characterized the expression profile in various tissues/organs and ex vivo culture conditions. The born GFP-transgenic pig demonstrate an organ/tissue-dependent expression pattern. Strong GFP expression is observed in the skeletal muscle, pancreas, heart, and kidney. Regarding cellular levels, bone-marrow-derived mesenchymal stromal cells, hepatocytes, and islet cells of the pancreas also show sufficient expression with the unique pattern. Moreover, the cloned pigs demonstrate normal growth and fertility, and the introduced GFP gene is stably transmitted to pigs in subsequent generations. The new GFP-expressing Jinhua pigs may be used as new cellular/tissue light resources for biological imaging in preclinical research fields such as tissue engineering, experimental regenerative medicine, and transplantation.

Study on distribution of pericyte and fluorescent granular perithelial (FGP) cell in the transitional region between arteriole and capillary in rat cerebral cortex.

The FGP (fluorescent granular perithelial) cell nominated by M. Mato were distributed around small cerebral vessels and potent in the uptake capacity. They are provided with surface antigens related to macrophage lineage. The aim of this report is to show the regional distribution of pericytes and novel perivascular cells (FGP cell) in relation to the glia limitans and basal lamina.