Shuhei Konagaya

Design of culture substrates for large-scale expansion of neural stem cells.

Neural stem cells (NSCs) have been frequently used to investigate in vitro the molecular and cellular mechanisms underlying the development of the central nervous system (CNS). In addition, NSCs are regarded as one of the potential sources for the cell replacement therapy of CNS disorders. Most of these studies have utilized NSCs prepared by neurosphere culture. However, this method normally yields a heterogeneous population containing differentiated neural cells as well as NSCs. In addition, the rate of cell expansion is not high enough for obtaining a large quantity of NSCs in a short period. Here we report the design of culture substrates that allow highly selective and rapid expansion of NSCs. We synthesize epidermal growth factor fused with a hexahistidine sequence (EGF-His) and a polystyrene-binding peptide (EGF-PSt), and these engineered growth factors were surface-anchored to a nickel-chelated glass plate and a polystyrene dish, respectively. The EGF-His-chelated glass substrate was further used to assemble a culture module. Neurosphere-forming cells prepared from the fetal rat striatum were used to examine the selective expansion of NSCs using the EGF-His-chelated module and the EGF-PSt-bound polystyrene dish. Our results show that the culture module enables to selectively expand NSCs in a closed system more efficiently than the standard neurosphere culture. The EGF-PSt-bound polystyrene dish also permits efficient expansion of NSCs, providing a straightforward means to acquire a large quantity of pure NSCs in standard laboratories.

Long-term maintenance of human induced pluripotent stem cells by automated cell culture system.

Pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem (iPS) cells, are regarded as new sources for cell replacement therapy. These cells can unlimitedly expand under undifferentiated conditions and be differentiated into multiple cell types. Automated culture systems enable the large-scale production of cells. In addition to reducing the time and effort of researchers, an automated culture system improves the reproducibility of cell cultures. In the present study, we newly designed a fully automated cell culture system for human iPS maintenance. Using an automated culture system, hiPS cells maintained their undifferentiated state for 60 days. Automatically prepared hiPS cells had a potency of differentiation into three germ layer cells including dopaminergic neurons and pancreatic cells.

Array-based functional screening of growth factors toward optimizing neural stem cell microenvironments

To gain insights into the effect of various growth factors on the behaviors of neural stem cells, cell culture assays were performed on the array that displayed five different growth factors including basic fibroblast growth factor, epidermal growth factor, insulin-like growth factor-1, brain-derived neurotrophic factor, and ciliary neurotrophic factor. These factors were expressed in Escherichia coli as fusion proteins with a hexahistidine sequence and arrayed on a nickel ion-functionalized chip as single factors or the combination of two factors. Neural stem cells obtained from the fetal rat brain were cultured on the array to investigate their proliferation and differentiation. It was shown that the five growth factors displayed as a single component had significant impacts on cell behaviors. These effects are overall in accordance with those reported previously. On the other hand, in the case that two different growth factors were co-displayed on a single spot, the behaviors of neural stem cells could not be simply predicted from their individual effects. We performed a multivariate cluster analysis for the quantitative data on cell proliferation and differentiation. It was shown that the effect of two growth factors co-displayed was competitive, synergistic, or destructive depending on the combinations. In other peculiar cases, the effect of growth factors was totally different from those of individual factors.

Coaggregates of Regulatory T Cells and Islet Cells Allow Long-term Graft Survival in Liver Without Immunosuppression.

Background Transplantation of islets of Langerhans (islets) has been investigated in the clinic to treat patients with insulin-dependent diabetes mellitus. Islet grafts have been maintained by administering immunosuppressive drugs, which can lead to complications in the long term. Alternatives to immunosuppressive therapy are eagerly desired. In this study, we examined the transplantation of coaggregates of CD4+CD25+ regulatory T (Treg) cells. Methods Coaggregates of Treg cells from C57BL/6 mice and islet cells from BALB/c mice were prepared on agarose hydrogel with small round-bottomed wells. Four hundred coaggregates were transplanted into the livers of streptozotocin-induced diabetic C57BL/6 mice without systemic immunosuppression. Results The Treg cells and islet cells were distributed randomly in the coaggregates. When 400 coaggregates were transplanted into 9 C57BL/6 mice via the portal vein, 6 of the 9 recipients demonstrated blood glucose less than 250 mg/dL for more than 100 days. A number of insulin-positive cells were observed in the livers at 120 days after transplantation. Conclusions The Treg cells and islet cells were distributed randomly in the coaggregates. After intraportal transplantation of the coaggregates, Treg cells in the aggregates enabled the long-term survival of allogeneic islet cell grafts in the liver without the use of immunosuppressive drugs.

Reproducible preparation of spheroids of pancreatic hormone positive cells from human iPS cells: An in vitro study

BACKGROUND Transplantation of islets of Langerhans is regarded as a promising therapy for type 1 diabetes. A large number of β-cells are required for the treatment of human type 1 diabetes. Pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, have been considered as new sources for cell replacement therapy. METHODS Cell aggregates were prepared from human iPS cells using agarose microwell plates and differentiated into pancreatic endocrine cells by changing the culture media with different additives. RESULTS After 20days of culture, approximately 30% of cells in aggregates were positive for C-peptide. After another 14days in culture, the cells gained an ability to alter C-peptide release in response to changes in the glucose concentration. CONCLUSIONS Uniform aggregates of human iPSCs were easily prepared on agarose microwell plates and efficiently differentiated into the pancreatic endocrine lineage. Thus, aggregate culture is a suitable method for preparing islet-like aggregates from human iPSCs. GENERAL SIGNIFICANCE Our results indicate that the microwell plate is suitable for scaling up the preparation of pancreatic endocrine cells from human iPS cells in a robotic system.

Microencapsulation of dopamine neurons derived from human induced pluripotent stem cells

BACKGROUND Dopamine neurons derived from induced pluripotent stem cells have been widely studied for the treatment of Parkinsons disease. However, various difficulties remain to be overcome, such as tumor formation, fragility of dopamine neurons, difficulty in handling large numbers of dopamine neurons, and immune reactions. In this study, human induced pluripotent stem cell-derived precursors of dopamine neurons were encapsulated in agarose microbeads. Dopamine neurons in microbeads could be handled without specific protocols, because the microbeads protected the fragile dopamine neurons from mechanical stress. METHODS hiPS cells were seeded on a Matrigel-coated dish and cultured to induce differentiation into a dopamine neuronal linage. On day 18 of culture, cells were collected from the culture dishes and seeded into U-bottom 96-well plates to induce cell aggregate formation. After 5 days, cell aggregates were collected from the plates and microencapsulated in agarose microbeads. The microencapsulated aggregates were cultured for an additional 45 days to induce maturation of dopamine neurons. RESULTS Approximately 60% of all cells differentiated into tyrosine hydroxylase-positive neurons in agarose microbeads. The cells released dopamine for more than 40 days. In addition, microbeads containing cells could be cryopreserved. CONCLUSION hiPS cells were successfully differentiated into dopamine neurons in agarose microbeads. GENERAL SIGNIFICANCE Agarose microencapsulation provides a good supporting environment for the preparation and storage of dopamine neurons.

Selective and rapid expansion of human neural progenitor cells on substrates with terminally anchored growth factors

Human neural progenitor cells (hNPCs) are a potential source for cell transplantation therapy in central nervous disorders. Neurosphere culture, the standard method for obtaining hNPCs, suffers from several limitations including the heterogeneity of cells in a neurosphere and the limitation of growth rate due to the presence of differentiated cells in the neurospheres. To overcome these limitations, we developed culture substrates that enable the selective expansion of hNPCs in adherent culture. Epidermal growth factor and basic fibroblast growth factor were fused with hexahistidine (EGF-His and bFGF-His, respectively) and were immobilized alone or in combination onto Ni ion-bound glass through coordination. When hNPCs derived from human fetal brain were cultured on these substrates, adhesion and proliferation of hNPCs took place most efficiently on the substrate with both EGF-His and bFGF-His compared to substrates with either factor alone and to a control substrate without growth factors. The rate of cell proliferation was two-fold higher in the adherent culture on the substrate immobilized with both EGF-His and bFGF-His than in the standard neurosphere culture. A cell population obtained after 5 days of culture on the substrate contained nestin-expressing progenitors (>90%). We conclude that the culture substrate with co-immobilized EGF and bFGF is effective for the selective expansion of hNPCs.

Closed-channel culture system for efficient and reproducible differentiation of human pluripotent stem cells into islet cells

Human pluripotent stem cells (hPSCs) are thought to be a promising cell-source solution for regenerative medicine due to their indefinite proliferative potential and ability to differentiate to functional somatic cells. However, issues remain with regard to achieving reproducible differentiation of cells with the required functionality for realizing human transplantation therapies and with regard to reducing the potential for bacterial or fungal contamination. To meet these needs, we have developed a closed-channel culture device and corresponding control system. Uniformly-sized spheroidal hPSCs aggregates were formed inside wells within a closed-channel and maintained continuously throughout the culture process. Functional islet-like endocrine cell aggregates were reproducibly induced following a 30-day differentiation protocol. Our system shows an easily scalable, novel method for inducing PSC differentiation with both purity and functionality.

Optimization of surface‐immobilized extracellular matrices for the proliferation of neural progenitor cells derived from induced pluripotent stem cells

Neural progenitor cells derived from induced pluripotent stem cells have been considered as a potential source for cell‐transplantation therapy of central nervous disorders. However, efficient methods to expand neural progenitor cells are further required for their clinical applications. In this study, a protein array was fabricated with nine extracellular matrices and used to screen substrates suitable for the expansion of neural progenitor cells derived from mouse induced pluripotent stem cells. The results showed that neural progenitor cells efficiently proliferated on substrates with immobilized laminin‐1, laminin‐5, or Matrigel. Based on this result, further attempts were made to develop clinically compliant substrates with immobilized polypeptides that mimic laminin‐1, one of the most effective extracellular matrices as identified in the array‐based screening. We used here recombinant DNA technology to prepare polypeptide containing the globular domain 3 of laminin‐1 and immobilized it onto glass‐based substrates. Our results showed that neural progenitor cells selectively proliferated on substrate with the immobilized polypeptide while maintaining their differentiated state. Biotechnol. Bioeng. 2015;112: 2388–2396.

Maturation of human iPS cell-derived dopamine neuron precursors in alginate-Ca(2+) hydrogel.

BACKGROUND Pluripotent stem cells (embryonic stem/induced pluripotent stem cells) have been widely studied as a potential cell source for cell transplantation therapy of Parkinsons disease. However, some difficulties remain to be overcome. These include the need to prepare a large number of dopamine (DA) neurons for clinical use and to culture the cells for a long period to allow their functional maturation and the removal of undifferentiated cells. METHODS In this study, aggregates of DA neuron precursors were enclosed in alginate-Ca(2+) microbeads, and the encapsulated aggregates were cultured for 25days to induce cell maturation. RESULTS More than 60% of cells in the aggregates differentiated into tyrosine hydroxylase-positive DA neurons. The aggregates could release DA at the same level as aggregates maintained on culture dishes without encapsulation. In addition, by exposure to a citrate solution, the alginate-Ca(2+) gel layer could be easily removed from aggregates without damaging the DA neurons. When the aggregates were transplanted into rat brain, viable cells were found in the graft at one week post-transplantation, with cells extending neurites into the host tissue. CONCLUSIONS Cell aggregates encapsulated in alginate-Ca(2+) beads successfully differentiated into mature DA neurons. GENERAL SIGNIFICANCE The alginate-Ca(2+) microbead is suitable for maintaining DA precursor aggregates for a long period to allow their functional maturation.