Masahiro Kino-oka

Effect of neurosphere size on the growth rate of human neural stem/progenitor cells

Neural stem/progenitor cells (NSPCs) proliferate as aggregates in vitro, but the mechanism of aggregation is not fully understood. Here, we report that aggregation promotes the proliferation of NSPCs. We found that the proliferation rate was linear and depended on the size of the aggregate; that is, the population doubling time of the NSPCs gradually decreased as the diameter approached 250 μm and flattened to a nearly constant value beyond this diameter. Given this finding, and with the intent of enhancing the efficiency of human NSPC expansion, we induced the NSPCs to form aggregates close to 250 μm in diameter quickly by culturing them in plates with U‐bottomed wells. The NSPCs formed aggregates effectively in the U‐bottomed wells, with cell numbers approximately 1.5 times greater than those in the aggregates that formed spontaneously in flat‐bottomed wells. In addition, this effect of aggregation involved cell–cell signaling molecules of the Notch1 pathway. In the U‐bottomed wells, Hes1 and Hes5, which are target genes of the Notch signal, were expressed at higher levels than in the control, flat‐bottomed wells. The amount of cleaved Notch1 was also higher in the cells cultured in the U‐bottomed wells. The addition of γ‐secretase inhibitor, which blocks Notch signaling, suppressed cell proliferation in the U‐bottomed wells. These results suggest that the three‐dimensional architecture of NSPC aggregates would create a microenvironment that promotes the proliferation of human NSPCs.

Production and release of pigments by culture of transformed hairy root of red beet

Abstract Adventitious roots were induced from red beet ( Beta vulgaris L. cv. Detroit dark red) by infecting the plant with a soil bacterium, Agrobacterium rhizogenes . Based on analysis of opines which are uniquely produced in transformed hairy roots, the established clone was proved to be a transformed hairy root. In a shake culture of the beet hairy root clone with a liquid medium, it was found that significant amounts of pigments, mainly betanin and vulgaxanthin-I, were released into the medium by the cessation of culture shaking (temporary limitation of oxygen supply). The hairy root cells were capable of propagation even after the cells were subjected to shaking cessation. Repeated-batch culture of the beet hairy root was performed with the cell growth phases for 9 or 10 d and with pigment leakage phases during shaking cessation for 2 d, and more than 20% of the total intracellular pigments were recovered from the culture broth at a culture time of 35 d. The released pigments were confirmed to be substantially identical to those extracted from the hairy root and original plant cells of red beet.

Cardiomyogenic induction of human mesenchymal stem cells by altered Rho family GTPase expression on dendrimer-immobilized surface with d-glucose display

The commitment of stem cells to different lineages is regulated by many cues in the intercellular signals from the microenvironment system. In the present study, we found that alterations in Rho family GTPase activities derived from cytoskeletal formation can lead to guidance of cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs) during in vitro culture. To regulate the cytoskeletal formation of hMSCs, we employed a dendrimer-immobilized substrate that displayed D-glucose. With an increase in the dendrimer generation number, the cells exhibited active migration, accompanied by cell morphological changes of stretching and contracting. Fluorescence microscopy for F-actin, vinculin and glucose transporter1 (GLUT1) clarified the localization of integrin-mediated and GLUT-mediated anchoring, introducing the idea that the morphological changes of the cells were responsive to variations in the generation number of the dendrimer with d-glucose display. On the 5th-generation dendrimer surface, in particular, the cells exhibited RhoA down-regulation and Rac1 up-regulation during the culture, associated with alterations in the cellular morphology and migratory behaviors. It was found that cell aggregation was promoted on this surface, supporting the notion that an increase in N-cadherin-mediated cell-cell contacts and Wnt signaling regulate hMSC differentiation into cardiomyocyte-like cells.

Influence of medium constituents on enhancement of pigment production by batch culture of red beet hairy roots

Abstract For the enhancement of pigment production by red beet hairy roots, the effects of medium constituents (Murashige-Skoog (MS) medium) on hairy root cultures were investigated in flasks. In a series of cultures using media with diluted medium components, it was found that phosphate was a key nutrient involved in pigment accumulation in the hairy roots, and that higher pigment contents in the roots were obtained at lower phosphate concentrations (range of 0–2.5 mol/m3). In an 18 d batch culture using phosphate-free medium, the total amount of pigment production was 4.8 times that obtained in a control culture using normal MS medium with 1.25 mol/m3 phosphate.

Production and release of anthraquinone pigments by hairy roots of madder (Rubia tinctorum L.) under improved culture conditions

Abstract Carbon and nitrogen sources in the medium were selected for the culture of madder hairy roots producing anthraquinone pigments. The growth and pigment formation of the hairy roots were significantly enhanced by using modified Murashige-Skoog (MS) medium containing fructose and nitrate as the sole carbon and nitrogen sources, respectively, compared with those obtained in conventional MS medium with sucrose. Repeated-batch culture of the hairy roots was carried out, with pigment release into the medium obtained by means of O2 starvation treatment. In three pigment-release operations during 29-d culture, the total amount of released pigments was 21 mg/dm3, representing an average production rate of 0.72 mg/(dm3·d).

Valuation of growth parameters in monolayer keratinocyte cultures based on a two-dimensional cell placement model.

The influence of inoculum size on the growth of keratinocyte cells was investigated in a monolayer culture with serum-free medium. A growth model of cell placement was applied to the expression of the cell adhesion phase after the inoculation, lag phase, exponential growth phase, and stationary phase because of contact inhibition at high cell densities. Based on the model, the lag time until the onset of cell division was shortened in proportion to the logarithm of the inoculum cell size, resulting in the enhancement of overall cell propagation. It was verified that the proposed model is valid for the determination of the optimal inoculum size to realize the efficient growth of keratinocytes, indicating that the model is a useful tool to predict an optimal culture scheme for the production of skin grafts.

Switching between self-renewal and lineage commitment of human induced pluripotent stem cells via cell-substrate and cell-cell interactions on a dendrimer-immobilized surface.

Understanding mechanisms that govern cell fate determination of human induced pluripotent stem cells (hiPSCs) could assist in maintenance of the undifferentiated state during cell expansion. We used polyamidoamine dendrimer surfaces with first-generation (G1), third-generation (G3) and fifth-generation (G5) of dendron structure in cultures of hiPSCs with SNL feeder cells. Cells on the G1 surface formed tightly packed colony with close cell-cell contacts during division and migration; those on the G3 surface exhibited loose or dispersed colony pattern by enhanced migration. On the G5 surface, formation of aggregated colony with ring-like structures occurred spontaneously. We found that the substrate-adsorbed fibronectin and feeder cell-secreted fibronectin appeared elevated levels with the varied generation numbers of dendrimer surfaces. This subsequently resulted in cell migration and in activation of paxillin of hiPSCs. Location-dependent expression of Rac1 induced rearrangement of E-cadherin-mediated cell-cell interactions on dendrimer surfaces, and was associated with alterations in the cell and colony morphology, and migratory behavior. Furthermore, caspase-3 occurred in apoptotic cells on dendrimer surfaces, concomitant with the loss of E-cadherin-mediated cell-cell interactions. Cells on the G1 surface were maintained in an undifferentiated state, while those on the G5 surface exhibited the early commitment to differentiation toward endodermal fates. We conclude that morphological changes associated with altered migration on the dendrimer surfaces were responsible for the coordinated regulation of balance between cell-cell and cell-substrate interactions, thereby switching their transition from self-renewal state to early endoderm differentiation in hiPSCs.

Morphological evaluation of chondrogenic potency in passaged cell populations.

The present study describes the morphological assessment of chondrogenic potency during a cell expanding process through serial subculturing of rabbit chondrocytes at different levels of population doublings (PD) in a T-flask with a conventional polystyrene surface. The passaged populations were seeded on a high-density collagen surface (CL surface) and in a collagen gel (CL gel) scaffold to evaluate the planar and spatial morphologies of the chondrocytes, respectively, as well as the gene expressions of mRNA for collagen types I and II. The planar morphological estimation was based on roundness (R(c)) of chondrocyte cells at different PD values after 1 day incubation on the CL surface. The frequency of round-shaped cells with R(c)>0.9 (f(R)) decreased with increasing PD values, accompanied by an increase in collagen type I mRNA level. At PD=17.8, the frequency reached f(R)=0.12, which was less than one-sixth of that at PD=0. A similar trend was found with respect to the passaged chondrocytes embedded in the CL gels by estimating the spatial morphology in terms of sphericity (S(c)) determined 4 days after seeding. With an increase in PD value, the frequency in spherical-shaped cells with S(c)>0.9 (f(S)) decreased and the mRNA expression of collagen type I increased, giving f(S)=0.28 at PD=17.8 which was less than a quarter of that at PD=0. From these results, the cell morphologies on the CL surface and in the CL gel were proposed as indicators for understanding chondrogenic potentials concerning the phenotypes and differentiated states in the population during cell expansion, ultimately leading to quality control of tissue-engineered cartilage.

Seeding density modulates migration and morphology of rabbit chondrocytes cultured in collagen gels

The cultures of rabbit chondrocytes embedded in collagen gels were conducted to investigate the cell behaviors and consequent architectures of cell aggregation in an early culture phase. The chondrocyte cells seeded at 1.0 × 105 cells/cm3 underwent a transition to spindle‐shaped morphology, and formed the loose aggregates with a starburst shape by means of possible migration and gathering. These aggregates accompanied the poor production of collagen type II, while the cells seeded at 1.6 × 106 cells/cm3 exhibited active proliferation to form the dense aggregates rich in collagen type II. Stereoscopic observation was performed at 5 days to define the migrating cells in terms of a morphology‐relating parameter of sphericity determined for individual cells in the gels. The frequency of migrating cells decreased with increasing seeding density, while the frequency of dividing cells showed the counter trend. The culture seeded at 1.0 × 105 cells/cm3 gave the migrating cell frequency of 0.25, the value of which was 25 times higher than that at 1.6 × 106 cells/cm3. In addition, the analysis of mRNA expression revealed that the chondrocyte cells seeded at 1.0 × 105 cells/cm3 showed appreciable down‐regulation in collagen type II relating to differentiation and up‐regulation in matrix metalloproteinases relating to migration, as compared to the cells seeded at 1.6 × 106 cells/cm3. These data supports the morphological analyses concerning the cell migration and aggregate formation in the cultures with varied seeding densities. It is concluded that the seeding density is an important factor to affect the cell behaviors and architecture of aggregates and thereby to modulate the quality of cultured cartilage.

Enrichment of undifferentiated mouse embryonic stem cells on a culture surface with a glucose-displaying dendrimer

This article describes an in vitro culture system for embryonic stem (ES) cells, which are expected to serve as a cell source for transplantation because of their potential for indefinite expansion and pluripotency. We present a serial passaging protocol that permits the enrichment of undifferentiated ES cells by culturing them on a surface modified with a synthesized dendrimer having d-glucose as a functional ligand. The d-glucose-displaying dendrimer (GLU/D) surface caused mouse ES cells to form loosely attached spherical colonies, and the frequency of such colonies increased gradually with the number of passages. Analyses of alkaline phosphatase activity and the gene expression of pluripotency and early differentiation markers revealed that the spherical colony cells passaged four times (a total of 16days in culture) on the GLU/D surface acquired more of the characteristics of undifferentiated cells than the cells cultured on a conventional gelatin-coated surface. Moreover, the cells cultured on the GLU/D surface retained their germ-line transmission ability after four passages. These results indicate that this modified culture surface may be a useful tool for obtaining enriched preparations of undifferentiated ES cells.