HEK 293 cell suspension culture using fibronectin-adsorbed polymer nanospheres in serum-free medium

Maintenance of viability and proliferation of 3T3 cell aggregates incorporating fibroin microspheres into cultures

This study investigated whether micron-sized microspheres can be used as dispersed scaffolds where anchorage-dependent cells can proliferate and survive in suspension culture. Aggregates of murine 3T3 cells in a non-adherent plate cultured remained viable for more than 2 weeks by the presence of 0.5 mg/ml fibroin microspheres. A nucleoside incorporation assay confirmed the proliferation of 3T3 cells in the aggregates only when cultured with microspheres. Under these conditions, the glucose consumption rate of 3T3 cells increased to 66.5 nmol day^-1 cell^-1. Histological analysis demonstrated that the intercellular space of cell aggregates was larger in cultures supplemented with 0.5 mg/ml microspheres than in non-supplemented cultures. The cell aggregates with microspheres also exhibited a reduced arrest in G1 phase. Transmission electron microscopy verified the presence of microspheres in the space between cells in aggregates. Fibroin microspheres maintained the viability and proliferability of 3T3 cells cultured under non-adherent conditions and thus can be used to develop viable suspensions of anchorage-dependent cells.

Different morphologies of human embryonic kidney 293T cells in various types of culture dishes

Human embryonic kidney 293T (HEK293T) cells are used in various biological experiments and researches. In this study, we investigated the effect of cell culture environments on morphological and functional properties of HEK293T cells. We used several kinds of dishes made of polystyrene or glass for cell culture, including three types of polystyrene dishes provided from different manufacturers for suspension and adherent cell culture. In addition, we also investigated the effect of culturing on gelatin-coated surfaces on the cell morphology. We found that HEK293T cells aggregated and formed into three-dimensional (3-D) multicellular spheroids (MCS) when non-coated polystyrene dishes were used for suspension culture. In particular, the non-coated polystyrene dish from Sumitomo bakelite is the most remarkable characteristic for 3-D MCS among the polystyrene dishes. On the other hand, HEK293T cells hardly aggregated and formed 3-D MCS on gelatin-coated polystyrene dishes for suspension culture. HEK293T cells adhered on the non- or gelatin-coated polystyrene dish for adherent culture, but they did not form 3-D MCS. HEK293T cells also adhered to non- or gelatin-coated glass dishes and did not form 3-D MCS in serum-free medium. These results suggest that HEK293T cells cultured on non-coated polystyrene dish may be useful for the tool to analyze the characteristics of 3D-MCS.

Angiogenesis in ischemic tissue produced by spheroid grafting of human adipose-derived stromal cells

Stem cells offer significant therapeutic promise for the treatment of ischemic disease. However, stem cells transplanted into ischemic tissue exhibit limited therapeutic efficacy due to poor engraftment in vivo. Several strategies for improving the survival and engraftment of stem cells in ischemic tissue have been developed including transplantation in combination with growth factor delivery, genetic modification of stem cells, and the use of cell-transplantation scaffolds. Here, we demonstrate that human adipose-derived stromal cells (hADSCs) cultured and grafted as spheroids exhibit improved therapeutic efficacy for ischemia treatment. hADSCs were cultured in monolayer or spheroids. Spheroid cultures were more effective in preconditioning hADSCs to a hypoxic environment, upregulating hypoxia-adaptive signals (i.e., stromal cell-derived factor-1α and hypoxia-inducible factor-1α), inhibiting apoptosis, and enhancing secretion of both angiogenic and anti-apoptotic factors (i.e., hepatocyte growth factor, vascular endothelial growth factor, and fibroblast growth factor 2) compared to monolayer cultures. Moreover, cell harvesting following spheroid cultures avoided damage to extracellular matrices due to harsh proteolytic enzyme treatment, thereby preventing anoikis (apoptosis induced by a lack of cell-matrix interaction). Following intramuscular transplantation to ischemic hindlimbs of athymic mice, hADSC spheroids showed improved cell survival, angiogenic factor secretion, neovascularization, and limb survival as compared to hADSCs grafted as dissociated cells. Taken together, spheroid cultures precondition hADSCs to a hypoxic environment, and grafting hADSCs as spheroids to ischemic limbs improves therapeutic efficacy for ischemia treatment due to enhanced cell survival and paracrine effects. Spheroid-based cell delivery could be a simple and effective strategy for improving stem cell therapy for ischemic diseases, eliminating the need for growth factor delivery, biomaterial scaffolds or genetic modification.

Cryopreservable and tumorigenic three-dimensional tumor culture in porous poly(lactic-co-glycolic acid) microsphere

In vitro tumor models that mimic in vivo conditions may be ideal for screening anticancer drugs and their formulations and developing tumors in animal models. Three-dimensional (3-D) culture of cancer cells on polymeric scaffolds can be an option for such models. In the present study, porous poly(lactic acid-co-glycolic acid) (PLGA) microsphere was used both as a cancer cell culture substrate to expand cells and as a cancer cell transplantation vehicle for tumor construction in mice. MCF-7 cells cultured on porous PLGA microspheres in stirred suspension bioreactors expanded by 2.8-fold over seven days and maintained viability. At three months after inoculation with 2x10(6) cells/site, the tumor formation by MCF-7 cells cultured on microspheres was much more effective (4 tumors/5 mice) than its counterpart cultured on plates (1/5). More importantly, cell viability and metabolic activity were not significantly changed even after one freeze-thaw cycle of the 3-D culture. MCF-7 cells cultured on the microspheres and the cells in 3-D after cryopreservation were more resistant to doxorubicin than MCF-7 cells cultured on plates.

Porous poly(lactic-co-glycolic acid) microsphere as cell culture substrate and cell transplantation vehicle for adipose tissue engineering

Tissue engineering often requires ex vivo cell expansion to obtain a large number of transplantable cells. However, the trypsinization process used to harvest ex vivo expanded cells for transplantation interrupts interactions between cultured cells and their extracellular matrices, facilitating apoptosis and consequently limiting the therapeutic efficacy of the transplanted cells. In the present study, open macroporous poly(lactic-co-glycolic acid) (PLGA) microspheres were used as a cell culture substrate to expand human adipose-derived stromal cells (ASCs) ex vivo and as a cell transplantation vehicle for adipose tissue engineering, thus avoiding the trypsinization necessary for transplantation of ex vivo expanded cells. Human ASCs cultured on macroporous PLGA microspheres in stirred suspension bioreactors expanded 3.8-fold over 7 days and differentiated into an adipogenic lineage. The apoptotic activity of ASCs cultured on microspheres was significantly lower than that of trypsinized ASCs. ASCs cultured on microspheres survived much better than trypsinized ASCs upon transplantation. The implantation of ASCs cultured on microspheres resulted in much more extensive adipose tissue formation than the implantation of ASCs cultured on plates, trypsinized, and subsequently mixed with microspheres. Ex vivo cell expansion and transplantation using this system would improve the therapeutic efficacy of cells over the current methods used for tissue engineering.

A method for the effective formation of hepatocyte spheroids using a biodegradable polymer nanosphere

Cultures of hepatocytes in spheroid form are known to maintain higher cell viability and exhibit better hepatocyte functions than those in monolayer cultures. In this study, a method for the formation of hepatocyte spheroids was developed using biodegradable polymer nanospheres. The addition of poly(lactic-co-glycolic acid) nanospheres to hepatocyte cultures in spinner flasks increased the efficiency of hepatocyte spheroid formation (the number of cells in spheroids divided by the total cell number) as compared with hepatocyte cultures without nanospheres (control). The viability and mitochondrial activity of the hepatocyte spheroids in the nanosphere-added cultures were significantly higher than those in the control. In addition, the mRNA expression levels of albumin and phenylalanine hydroxylase, both of which are hepatocyte-specific proteins, were significantly higher in the nanosphere-added cultures than in the control. This new culture method improves upon the conventional method of forming hepatocyte spheroids in terms of spheroid formation efficiency, cell viability, and hepatocyte function.