Three-dimensional perfused cell culture

Recent Advances in Graphene Oxide-Based on Organoid Culture as Disease Model and Cell Behavior - A Systematic Literature Review

Due to their ability to replicate the in vivo microenvironment through cell interaction and induce cells to stimulate cell function, three-dimensional cell culture models can overcome the limitations of two-dimensional models. Organoids are 3D models that demonstrate the ability to replicate the natural structure of an organ. In most organoid tissue cultures, matrigel made of a mouse tumor extracellular matrix protein mixture is an essential ingredient. However, its tumor-derived origin, batch-to-batch variation, high cost, and safety concerns have limited the usefulness of organoid drug development and regenerative medicine. Its clinical application has also been hindered by the fact that organoid generation is dependent on the use of poorly defined matrices. Therefore, matrix optimization is a crucial step in developing organoid culture that introduces alternatives as different materials. Recently, a variety of substitute materials has reportedly replaced matrigel. The purpose of this study is to review the significance of the latest advances in materials for cell culture applications and how they enhance build network systems by generating proper cell behavior. Excellence in cell behavior is evaluated from their cell characteristics, cell proliferation, cell differentiation, and even gene expression. As a result, graphene oxide as a matrix optimization demonstrated high potency in developing organoid models. Graphene oxide can promote good cell behavior and is well known for having good biocompatibility. Hence, advances in matrix optimization of graphene oxide provide opportunities for the future development of advanced organoid models.

Evaluating the pro-survival potential of apoptotic bodies derived from 2D- and 3D- cultured adipose stem cells in ischaemic flaps

In the realm of large-area trauma flap transplantation, averting ischaemic necrosis emerges as a pivotal concern. Several key mechanisms, including the promotion of angiogenesis, the inhibition of oxidative stress, the suppression of cell death, and the mitigation of inflammation, are crucial for enhancing skin flap survival. Apoptotic bodies (ABs), arising from cell apoptosis, have recently emerged as significant contributors to these functions. This study engineered three-dimensional (3D)-ABs using tissue-like mouse adipose-derived stem cells (mADSCs) cultured in a 3D environment to compare their superior biological effects against 2D-ABs in bolstering skin flap survival. The findings reveal that 3D-ABs (85.74 ± 4.51) % outperform 2D-ABs (76.48 ± 5.04) % in enhancing the survival rate of ischaemic skin flaps (60.45 ± 8.95) % (all p < 0.05). Mechanistically, they stimulated angiogenesis, mitigated oxidative stress, suppressed apoptosis, and facilitated the transition of macrophages from M1 to M2 polarization (all p < 0.05). A comparative analysis of microRNA (miRNA) profiles in 3D- and 2D-ABs identified several specific miRNAs (miR-423-5p-up, miR30b-5p-down, etc.) with pertinent roles. In summary, ABs derived from mADSCs cultured in a 3D spheroid-like arrangement exhibit heightened biological activity compared to those from 2D-cultured mADSCs and are more effective in promoting ischaemic skin flap survival. These effects are attributed to their influence on specific miRNAs.

In vitro formation and extended culture of highly metabolically active and contractile tissues

3D cell culture models have gained popularity in recent years as an alternative to animal and 2D cell culture models for pharmaceutical testing and disease modeling. Polydimethylsiloxane (PDMS) is a cost-effective and accessible molding material for 3D cultures; however, routine PDMS molding may not be appropriate for extended culture of contractile and metabolically active tissues. Failures can include loss of culture adhesion to the PDMS mold and limited culture surfaces for nutrient and waste diffusion. In this study, we evaluated PDMS molding materials and surface treatments for highly contractile and metabolically active 3D cell cultures. PDMS functionalized with polydopamine allowed for extended culture duration (14.8 ± 3.97 days) when compared to polyethylamine/glutaraldehyde functionalization (6.94 ± 2.74 days); Additionally, porous PDMS extended culture duration (16.7 ± 3.51 days) compared to smooth PDMS (6.33 ± 2.05 days) after treatment with TGF-β2 to increase culture contraction. Porous PDMS additionally allowed for large (13 mm tall × 8 mm diameter) constructs to be fed by diffusion through the mold, resulting in increased cell density (0.0210 ± 0.0049 mean nuclear fraction) compared to controls (0.0045 ± 0.0016 mean nuclear fraction). As a practical demonstration of the flexibility of porous PDMS, we engineered a vascular bioartificial muscle model (VBAM) and demonstrated extended culture of VBAMs anchored with porous PDMS posts. Using this model, we assessed the effect of feeding frequency on VBAM cellularity. Feeding 3×/week significantly increased nuclear fraction at multiple tissue depths relative to 2×/day. VBAM maturation was similarly improved in 3×/week feeding as measured by nuclear alignment (23.49° ± 3.644) and nuclear aspect ratio (2.274 ± 0.0643) relative to 2x/day (35.93° ± 2.942) and (1.371 ± 0.1127), respectively. The described techniques are designed to be simple and easy to implement with minimal training or expense, improving access to dense and/or metabolically active 3D cell culture models.

Biomaterials based on hyaluronic acid, collagen and peptides for three-dimensional cell culture and their application in stem cell differentiation

In recent decades, three-dimensional (3D) cell culture technologies have been developed rapidly in the field of tissue engineering and regeneration, and have shown unique advantages and great prospects in the differentiation of stem cells. Herein, the article reviews the progress and advantages of 3D cell culture technologies in the field of stem cell differentiation. Firstly, 3D cell culture technologies are divided into two main categories: scaffoldless and scaffolds. Secondly, the effects of hydrogels scaffolds and porous scaffolds on stem cell differentiation in the scaffold category were mainly reviewed. Among them, hydrogels scaffolds are divided into natural hydrogels and synthetic hydrogels. Natural materials include polysaccharides, proteins, and their derivatives, focusing on hyaluronic acid, collagen and polypeptides. Synthetic materials mainly include polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinyl alcohol (PVA), etc. In addition, since the preparation techniques have a large impact on the properties of porous scaffolds, several techniques for preparing porous scaffolds based on different macromolecular materials are reviewed. Finally, the future prospects and challenges of 3D cell culture in the field of stem cell differentiation are reviewed. This review will provide a useful guideline for the selection of materials and techniques for 3D cell culture in stem cell differentiation.

Solvent system effects on the physical and mechanical properties of electrospun Poly(ε-caprolactone) scaffolds for in vitro lung models

Mechanical properties are among the key considerations for the design and fabrication of complex tissue models and implants. In addition to the choice of material and the processing technique, the solvent system can significantly influence the mechanical properties of scaffolds. Poly(ε-caprolactone) (PCL) has been abundantly used to develop constructs, fibrous in particular, for pharmaceutical and biomedical research due to the flexibility offered by PCL-based fibrous matrices. The effect of solvent type on the morphological features of electrospun fibres has been extensively studied. Nevertheless, comprehensive studies on the impact of the solvent system on the mechanical properties of electrospun PCL fibres are lacking. This study elucidates the relationship between topographical, physical and mechanical properties of electrospun PCL fibrous meshes upon using various solvent systems. The results of the mechanical investigation highlight the significance of inter-fibre bonds on the mechanical properties of the bulk membranes and that the option of altering the solvent system composition could be considered for tuning the mechanical properties of the PCL scaffolds to serve specific biomedical application requirements. The applicability of the developed membranes as artificial ECM (Extracellular matrix) in the lung will then be investigated and compared to the commercial Polycarbonate (PC) membranes that are often used for in vitro lung models.

Construction of polysaccharide scaffold-based perfusion bioreactor supporting liver cell aggregates for drug screening

Rebuilding a suitable microenvironment of liver cells is the key challenge to enhancing the expression of hepatic functions for drug screening in vitro. To improve the microenvironment by providing the specific adhesive ligands for hepatocytes in the three-dimensional dynamic culture, a perfusion bioreactor with a pectin/alginate blend porous scaffold was constructed in this study. The galactosyl component in the main chain of pectin was able to be specifically recognized by the asialoglycoprotein receptor on the surface of hepatocytes, and subsequently promoted the adhesion and aggregation of hepatocytes co-cultured with hepatic non-parenchymal cells. The bioreactor was optimized for 4 h of dynamic inoculation followed by perfusion at a flow rate of 2 mL/min, which provided adequate oxygen supply and good mass transfer to the liver cells. During dynamic cultured in the bioreactor for 14 days, more multicellular aggregates were formed and were evenly distributed in the pectin/alginate blend scaffolds. The expressions of intercellular interaction and hepatic functions of the hepatocytes in aggregates were significantly enhanced in the three-dimensional dynamic group. Furthermore, the bioreactor not only markedly upregulated the cell polarity markers expression of hepatocytes but also enhanced their metabolic capacity to acetaminophen, isoniazid, and tolbutamide, which exhibited a significant concentration-dependent manner. Therefore, the pectin/alginate blend scaffold-based perfusion bioreactor appeared to be a promising candidate in the field of drug development and liver regeneration research.

Monolayer (2D) or spheroids (3D) cell cultures for nanotoxicological studies? Comparison of cytotoxicity and cell internalization of nanoparticles

Two-dimensional (2D) cell culture monolayers are commonly used for toxicological assessments of nanomaterials. Despite their facile handling, they exhibit several constraints due to their structural and complexity differences with three-dimensional (3D) in vitro cell models, such as spheroids. Here, we conducted a comparative nanotoxicological study of fibroblasts (L929) and melanoma (B16-F10) cells, grown in 2D and 3D arrangements. The cytotoxicity, reactive oxygen species (ROS) production, genotoxicity, cell morphology complexity, and uptake of silver nanoparticles (AgNPs) and folic acid-functionalized upconversion nanoparticles (FA-UCNPs) were compared in the two culture arrangements. AgNPs cytotoxicity was higher in spheroids than in monolayer cultures. Furthermore, apoptotic cell percentages and ROS production were higher in 3D than in 2D cell cultures. More importantly, 2D cultures required twice the concentration of AgNPs than the 3D cell models to reach a considerable DNA damage index (c.a. 200). Therefore, spheroids are more sensitive to the genotoxic effects of AgNPs. FA-UCNPs exerted negligible cell toxicity in 2D and 3D cell models. Moreover, AgNPs induced disaggregation and downsizing of spheroids in a facile and concentration-dependent manner. Internalization of FA-UCNPs in spheroids was 20% higher than in the 2D cell arrangements. Collectively, our findings, demonstrated that spheroids are a more sensitive model than monolayers for the assessment of nanoparticle biocompatibility and internalization.

Fingerprinting Metabolic Activity and Tissue Integrity of 3D Lung Cancer Spheroids under Gold Nanowire Treatment

Inadequacy of most animal models for drug efficacy assessments has led to the development of improved in vitro models capable of mimicking in vivo exposure scenarios. Among others, 3D multicellular spheroid technology is considered to be one of the promising alternatives in the pharmaceutical drug discovery process. In addition to its physiological relevance, this method fulfills high-throughput and low-cost requirements for preclinical cell-based assays. Despite the increasing applications of spheroid technology in pharmaceutical screening, its application, in nanotoxicity testing is still in its infancy due to the limited penetration and uptake rates into 3D-cell assemblies. To gain a better understanding of gold nanowires (AuNWs) interactions with 3D spheroids, a comparative study of 2D monolayer cultures and 3D multicellular spheroids was conducted using two lung cancer cell lines (A549 and PC9). Cell apoptosis (live/dead assay), metabolic activity, and spheroid integrity were evaluated following exposure to AuNWs at different dose-time manners. Results revealed a distinct different cellular response between 2D and 3D cell cultures during AuNWs treatment including metabolic rates, cell viability, dose-response curves and, uptake rates. Our data also highlighted further need for more physiologically relevant tissue models to investigate in depth nanomaterial-biology interactions. It is important to note that higher concentrations of AuNWs with lower exposure times and lower concentrations of AuNWs with higher exposure times of 3 days resulted in the loss of spheroid integrity by disrupting cell-cell contacts. These findings could help to increase the understanding of AuNWs-induced toxicity on tissue levels and also contribute to the establishment of new analytical approaches for toxicological and drug screening studies.

Altered expression of genes identified in rats with prostatic chronic inflammation in a prostate spheroid model treated by estradiol/testosterone

Rats are the standard model for male reproductive toxicity testing. Rat prostates are physiologically and anatomically different from those of humans. Drug and chemical toxicity testing would benefit from an in vitro model of human prostate cells. Recently, spheroids derived by three-dimensional culture of human cell lines have been used for assessing drug and chemical toxicity in vitro as they mimic in vivo environments more closely than two-dimensional culture. However, forming consistently sized, uniform spheroids is technically challenging for toxicity testing. The purpose of this study was to identify potential genetic markers for assessing prostatic toxicity in spheroids. We formed prostate spheroids using agarose-coated plates seeded with human primary prostate epithelial cells. Prostate spheroids were treated with either 17β-estradiol (E2) or testosterone (T) on days 2-7 of culture. Samples were harvested on culture day 7. qPCR was used to examine gene expression levels previously identified in rats with chronic inflammation exposed to estradiol benzoate, E2 and/or T. Changes in some gene expression levels were observed in the spheroids treated with E2 or T. We found that treatment with 1 nM E2 and/or 10 μM T significantly altered spheroid proliferation and viability, as well as the expression levels of genes including Nanog homeobox (NANOG), C-C motif chemokine ligand 2 (CCL2) and bone morphogenetic protein receptor type 2 (BMPR2). Further studies using biologically active molecules with prostatic toxicity are needed to verify the results and to determine whether gene expression changes in the spheroid are specific to E2 or T treatment.

PlateFlo - A software-controllable plate-scale perfusion system for culture of adherent cells

Here we present a versatile system for milliliter-scale perfusion culture of adherent cells that can be built using basic tools, based on a readily available one-well culture plate (84 cm² culture area). Media composition and flow paths can be programmatically controlled via USB serial interface using the FETbox hardware controller and associated PlateFlo Python package. The FETbox can control up to five high current 12 V devices such as common pinch valves, solenoids, and DC motor peristaltic pumps. It was designed to be easily customized with built-in accommodation for additional electronic components (e.g. analog sensors and input), use of the ubiquitous Arduino Nano platform, and easily expanded serial communication protocol. Multiple FETboxes can be used in parallel for additional devices. Applications of the PlateFlo system include perfusion culture of laboratory experiments requiring large cell numbers including genome-scale genetic screens and proteomics, as well as novel perfusion schemes including dynamic media conditions and sequential cell culture.

Transitioning into GMP-Compliance: Alternative Methods for Producing Retinal Organoids for Transplantation

Three-dimensional retinal organoids derived from human induced pluripotent stem cells (hiPSCs) are gaining much attention as a possible source for cell transplantation to treat retinal degenerative conditions. However, the protocol for producing retinal organoids is time and labor intensive, involving a sequence of precise steps, and thus has yet to be successfully translated into a Good Manufacturing Practice (GMP)-compliant procedure. This review seeks to define the progress that has already been made in the pursuit of designing a GMP-compliant, streamlined, and automated protocol for retinal organoid production for optimal clinical success. The reviewed literature compares various approaches for cell culture automation, appropriate xeno-free conditions, and cell sources for iPSC line generation; yet, there are still important gaps for these three key considerations that remain to be addressed. Thus, the authors also discuss further potential strategies to successfully achieve GMP-compliant production of retinal organoids for eventual safe and efficient use in clinical trials.

Influence of Culture Substrates on Morphology and Function of Pulmonary Alveolar Cells In Vitro

Cell's microenvironment has been shown to exert influence on cell behavior. In particular, matrix-cell interactions strongly impact cell morphology and function. The purpose of this study was to analyze the influence of different culture substrate materials on phenotype and functional properties of lung epithelial adenocarcinoma (A549) cells. A549 cells were seeded onto two different biocompatible, commercially available substrates: a polyester coverslip (Thermanox™ Coverslips), that was used as cell culture plate control, and a polydimethylsiloxane membrane (PDMS, Elastosil^® Film) investigated in this study as alternative material for A549 cells culture. The two substrates influenced cell morphology and the actin cytoskeleton organization. Further, the Yes-associated protein (YAP) and its transcriptional coactivator PDZ-binding motif (TAZ) were translocated to the nucleus in A549 cells cultured on polyester substrate, yet it remained mostly cytosolic in cells on PDMS substrate. By SEM analysis, we observed that cells grown on Elastosil^® Film maintained an alveolar Type II cell morphology. Immunofluorescence staining for surfactant-C revealing a high expression of surfactant-C in cells cultured on Elastosil^® Film, but not in cells cultured on Thermanox™ Coverslips. A549 cells grown onto Elastosil^® Film exhibited morphology and functionality that suggest retainment of alveolar epithelial Type II phenotype, while A549 cells grown onto conventional plastic substrates acquired an alveolar Type I phenotype.

Comparative Analysis of Mesenchymal Stem Cell Cultivation in Fetal Calf Serum, Human Serum, and Platelet Lysate in 2D and 3D Systems

In vitro two-dimensional (2D) and three-dimensional (3D) cultivation of mammalian cells requires supplementation with serum. Mesenchymal stem cells (MSCs) are widely used in clinical trials for bioregenerative medicine and in most cases, in vitro expansion and differentiation of these cells are required before application. Optimized expansion and differentiation protocols play a key role in the treatment outcome. 3D cell cultivation systems are more comparable to in vivo conditions and can provide both, more physiological MSC expansion and a better understanding of intercellular and cell-matrix interactions. Xeno-free cultivation conditions minimize risks of immune response after implantation. Human platelet lysate (hPL) appears to be a valuable alternative to widely used fetal calf serum (FCS) since no ethical issues are associated with its harvest, it contains a high concentration of growth factors and cytokines and it can be produced from expired platelet concentrate. In this study, we analyzed and compared proliferation, as well as osteogenic and chondrogenic differentiation of human adipose tissue-derived MSCs (hAD-MSC) using three different supplements: FCS, human serum (HS), and hPL in 2D. Furthermore, online monitoring of osteogenic differentiation under the influence of different supplements was performed in 2D. hPL-cultivated MSCs exhibited a higher proliferation and differentiation rate compared to HS- or FCS-cultivated cells. We demonstrated a fast and successful chondrogenic differentiation in the 2D system with the addition of hPL. Additionally, FCS, HS, and hPL were used to formulate Gelatin-methacryloyl (GelMA) hydrogels in order to evaluate the influence of the different supplements on the cell spreading and proliferation of cells growing in 3D culture. In addition, the hydrogel constructs were cultivated in media supplemented with three different supplements. In comparison to FCS and HS, the addition of hPL to GelMA hydrogels during the encapsulation of hAD-MSCs resulted in enhanced cell spreading and proliferation. This effect was promoted even further by cultivating the hydrogel constructs in hPL-supplemented media.

Small-Scale Fluidized Bed Bioreactor for Long-Term Dynamic Culture of 3D Cell Constructs and in vitro Testing

With the increasing interest in three-dimensional (3D) cell constructs that better represent native tissues, comes the need to also invest in devices, i.e., bioreactors, that provide a controlled dynamic environment similar to the perfusion mechanism observed in vivo. Here a laboratory-scale fluidized bed bioreactor (sFBB) was designed for hydrogel (i.e., alginate) encapsulated cells to generate a dynamic culture system that produced a homogenous milieu and host substantial biomass for long-term evolution of tissue-like structures and “per cell” performance analysis. The bioreactor design, conceptualized through scale-down empirical similarity rules, was initially validated through computational fluid dynamics analysis for the distributor capacity of homogenously dispersing the flow with an average fluid velocity of 4.596 × 10^–4 m/s. Experimental tests then demonstrated a consistent fluidization of hydrogel spheres, while maintaining shape and integrity (606.9 ± 99.3 μm diameter and 0.96 shape factor). It also induced mass transfer in and out of the hydrogel at a faster rate than static conditions. Finally, the sFBB sustained culture of alginate encapsulated hepatoblastoma cells for 12 days promoting proliferation into highly viable (>97%) cell spheroids at a high final density of 27.3 ± 0.78 million cells/mL beads. This was reproducible across multiple units set up in parallel and operating simultaneously. The sFBB prototype constitutes a simple and robust tool to generate 3D cell constructs, expandable into a multi-unit setup for simultaneous observations and for future development and biological evaluation of in vitro tissue models and their responses to different agents, increasing the complexity and speed of R&D processes.

Comparative study of FosPeg® photodynamic effect on nasopharyngeal carcinoma cells in 2D and 3D models

Photodynamic Therapy (PDT) offers an alternative option for the treatment of nasopharyngeal carcinoma (NPC). The utilization of 3-dimensional (3D) culture model might provide better understanding of PDT effects on NPC cells. The aim of this in vitro study was to compare PDT effect on NPC cells using 2D and 3D models. Two 3D culture models were established using liquid overlay method with agarose base (MCL) and hanging drop method (MCS). PDT was carried out using the combination of FosPeg® and 652 nm laser in 3D and conventional 2D models. The effects of 3D culture size and morphology on the uptake and distribution of sensitizer and gene expression were examined. Photocytotoxity, mode of cell death, and protein expression were compared for 2D and 3D models. Regular and irregular NPC spheroids were obtained from MCL and MCS methods, respectively. A significantly down-regulation of LMP1 mRNA were observed in MCL spheroid. The sensitizer uptake in 3D spheroids was half of 2D culture. More sensitizers were required to obtain IC₅₀ in 3D spheroids. Apoptosis, necrosis and autophagosomes were detected in PDT treated 2D and 3D cells. Different protein expression patterns were observed in 2D and 3D models. FosPeg® PDT is effective in killing NPC cells. MCL-derived 3D spheroid model is more suitable for the evaluation of PDT killing mechanisms.

Engineering functional microvessels in synthetic polyurethane random-pore scaffolds by harnessing perfusion flow

Recently reported biomaterial-based approaches toward prevascularizing tissue constructs rely on biologically or structurally complex scaffolds that are complicated to manufacture and sterilize, and challenging to customize for clinical applications. In the current work, a prevascularization method for soft tissue engineering that uses a non-patterned and non-biological scaffold is proposed. Human fibroblasts and HUVECs were seeded on an ionomeric polyurethane-based hydrogel and cultured for 14 days under medium perfusion. A flow rate of 0.05 mL/min resulted in a greater lumen density in the constructs relative to 0.005 and 0.5 mL/min, indicating the critical importance of flow magnitude in establishing microvessels. Constructs generated at 0.05 mL/min perfusion flow were implanted in a mouse subcutaneous model and intravital imaging was used to characterize host blood perfusion through the construct after 2 weeks. Engineered microvessels were functional (i.e. perfused with host blood and non-leaky) and neovascularization of the construct by host vessels was enhanced relative to non-prevascularized constructs. We report on the first strategy toward engineering functional microvessels in a tissue construct using non-bioactive, non-patterned synthetic polyurethane materials.

Rapid Prototyping of Multilayer Microphysiological Systems

Microfluidic organs-on-chips aim to realize more biorelevant in vitro experiments compared to traditional two-dimensional (2D) static cell culture. Often such devices are fabricated via poly(dimethylsiloxane) (PDMS) soft lithography, which offers benefits (e.g., high feature resolution) along with drawbacks (e.g., prototyping time/costs). Here, we report benchtop fabrication of multilayer, PDMS-free, thermoplastic organs-on-chips via laser cut and assembly with double-sided adhesives that overcome some limitations of traditional PDMS lithography. Cut and assembled chips are economical to prototype ($2 per chip), can be fabricated in parallel within hours, and are Luer compatible. Biocompatibility was demonstrated with epithelial line Caco-2 cells and primary human small intestinal organoids. Comparable to control static Transwell cultures, Caco-2 and organoids cultured on chips formed confluent monolayers expressing tight junctions with low permeability. Caco-2 cells-on-chip differentiated ∼4 times faster, including increased mucus, compared to controls. To demonstrate the robustness of cut and assemble, we fabricated a dual membrane, trilayer chip integrating 2D and 3D compartments with accessible apical and basolateral flow chambers. As proof of concept, we cocultured a human, differentiated monolayer and intact 3D organoids within multilayered contacting compartments. The epithelium exhibited 3D tissue structure and organoids expanded close to the adjacent monolayer, retaining proliferative stem cells over 10 days. Taken together, cut and assemble offers the capability to rapidly and economically manufacture microfluidic devices, thereby presenting a compelling fabrication technique for developing organs-on-chips of various geometries to study multicellular tissues.

Epidermal growth factor and three-dimensional scaffolds provide conducive environment for differentiation of mouse embryonic stem cells into oocyte-like cells

Three-dimensional (3D) culture provides a biomimicry of the naive microenvironment that can support cell proliferation, differentiation, and regeneration. Some growth factors, such as epidermal growth factor (EGF), facilitate normal meiosis during oocyte maturation in vivo. In this study, a scaffold-based 3D coculture system using purified alginate was applied to induce oocyte differentiation from mouse embryonic stem cells (mESCs). mESCs were induced to differentiate into oocyte-like cells using embryoid body protocol in the two-dimensional or 3D microenvironment in vitro. To increase the efficiency of the oocyte-like cell differentiation from mESCs, we employed a coculture system using ovarian granulosa cells in the presence or absence of epidermal growth factor (+EGF or -EGF) for 14 days and then the cells were assessed for germ cell differentiation, meiotic progression, and oocyte maturation markers. The cultures exposed to EGF in the alginate-based 3D microenvironment showed the highest level of premeiotic (Oct4 and Mvh), meiotic (Scp1, Scp3, Stra8, and Rec8), and oocyte maturation (Gdf9, Cx37, and Zp2) marker genes (p < .05) in comparison to other groups. According to the gene-expression patterns, we can conclude that alginate-based 3D coculture system provided a highly efficient protocol for oocyte-like cell differentiation from mESCs. The data showed that this culture system along with EGF improved the rate of in vitro oocyte-like cell differentiation.

Decellularization of Extracellular Matrix from Equine Skeletal Muscle

Equine represents an attractive animal model for musculoskeletal tissue diseases, exhibiting much similarity to the injuries that occur in humans. Cell therapy and tissue bioengineering have been widely used as a therapeutic alternative by regenerative medicine in musculoskeletal diseases. Thus, the aim of this study was to produce an acellular biomaterial of equine skeletal muscle and to evaluate its effectiveness in supporting the in vitro culture of equine induced pluripotency stem cells (iPSCs). Biceps femoris samples were frozen at -20°C for 4 days and incubated in 1% sodium dodecyl sulfate (SDS), 5 mM EDTA + 50 mM Tris and 1% Triton X-100; the effectiveness of the decellularization was evaluated by the absence of remnant nuclei (histological and 4',6-diamidino-2-phenylindole [DAPI] analysis), preservation of extracellular matrix (ECM) proteins (immunofluorescence and immunohistochemistry) and organization of ECM ultrastructure (scanning electron microscopy). Decellularized samples were recellularized with iPSCs at the concentration of 50,000 cells/cm² and cultured in vitro for 9 days, and the presence of the cells in the biomaterial was evaluated by histological analysis and presence of nuclei. Decellularized biomaterial showed absence of remnant nuclei and muscle fibers, as well as the preservation of ECM architecture, vascular network and proteins, laminin, fibronectin, elastin, collagen III and IV. After cellularization, iPSC nuclei were present at 9 days after incubation, indicating the decellularized biomaterial-supported iPSC survival. It is concluded that the ECM biomaterial produced from the decellularized equine skeletal muscle has potential for iPSC adhesion, representing a promising biomaterial for regenerative medicine in the therapy of musculoskeletal diseases.

Analysis of calcium signaling in live human Tongue cell 3D-Cultures upon tastant perfusion

Bridging the gap between two-dimensional cell cultures and complex in vivo tissues, three-dimensional cell culture models are of increasing interest in the fields of cell biology and pharmacology. However, present challenges hamper live cell imaging of three-dimensional cell cultures. These include (i) the stabilization of these structures under perfusion conditions, (ii) the recording of many z-planes at high spatio-temporal resolution, (iii) and the data analysis that ranges in complexity from whole specimens to single cells. Here, we addressed these issues for the time-lapse analysis of Ca²⁺ signaling in spheroids composed of human tongue-derived HTC-8 cells upon perfusion of gustatory substances. Live cell imaging setups for confocal and light sheet microscopy were developed that allow simple and robust spheroid stabilization and high-resolution microscopy with perfusion. Visualization of spheroids made of HTC-8 cells expressing the G-GECO fluorescent Ca²⁺ sensor revealed Ca²⁺ transients that showed similar kinetics but different amplitudes upon perfusion of bitter compounds Salicine and Saccharin. Dose-dependent responses to Saccharin required extracellular Ca²⁺. From the border towards the center of spheroids, compound-induced Ca²⁺ signals were progressively delayed and decreased in amplitude. Stimulation with ATP led to strong Ca²⁺ transients that were faster than those evoked by the bitter compounds and blockade of purinergic receptors with Suramin abutted the response to Saccharin, suggesting that ATP mediates a positive autocrine and paracrine feedback. Imaging of ATP-induced Ca²⁺ transients with light sheet microscopy allowed acquisition over a z-depth of 100 μm without losing spatial and temporal resolution. In summary, the presented approaches permit the study of fast cellular signaling in three-dimensional cultures upon compound perfusion.

Gelatin-Methacryloyl (GelMA) Formulated with Human Platelet Lysate Supports Mesenchymal Stem Cell Proliferation and Differentiation and Enhances the Hydrogel's Mechanical Properties

Three-dimensional (3D) cell culture is a major focus of current research, since cultivation under physiological conditions provides more reliable information about in vivo cell behavior. 3D cell cultures are used in basic research to better understand intercellular and cell-matrix interactions. However, 3D cell culture plays an increasingly important role in the in vitro testing of bioactive substances and tissue engineering. Gelatin-methacryloyl (GelMA) hydrogels of different degrees of functionalization (DoFs) are a versatile tool for 3D cell culture and related applications such as bioprinting. Human platelet lysate (hPL) has already demonstrated positive effects on 2D cell cultures of different cell types and has proven a valuable alternative to fetal calf serum (FCS). Traditionally, all hydrogels are formulated using buffers. In this study, we supplemented GelMA hydrogels of different DoF with hPL during adipose tissue-derived mesenchymal stem cell (AD-MSCs) encapsulation. We studied the effect of hPL supplementation on the spreading, proliferation, and osteogenic differentiation of AD-MSCs. In addition, the influence of hPL on hydrogel properties was also investigated. We demonstrate that the addition of hPL enhanced AD-MSC spreading, proliferation, and osteogenic differentiation in a concentration-dependent manner. Moreover, the addition of hPL also increased GelMA viscosity and stiffness.

A three-dimensional (3D) printed biomimetic hierarchical scaffold with a covalent modular release system for osteogenesis

Hydroxyapatite (HA) ceramics are well known for their biocompatibility, bioactivity, and osteoconductive nature. However, limited hierarchical structure and lack of ease in modularity hinder the widespread application of conventional HA ceramics. By using three-dimensional printing (3DP) techniques with multiple materials, including HA, complex biological and mechanical architecture of natural organisms can be achieved through biomimetics. In this study, we designed an osteoid, biomimetic, hierarchical, porous HA ceramic 3D printed scaffold (3DPs). Further incorporation of a covalent, modular, controlled release system (CMR), based on Watson-Crick's complementary oligonucleotides, and was added to carry a bone morphogenetic protein-2 (BMP2) peptide. The choice of a HA biomimetic scaffold housing BMP2 protein fragments was selected to successfully promote osteogenesis both in vitro and in vivo. Scanning electron microscopy, micro-computed tomography analysis and computer fluid dynamics simulations of the 3DPs showed a uniform biomimetic hierarchical structure and an effective interior permeability. Active molecules were found bound with high stability and modular to the scaffold surface via the CMR system. After 7 days of incubation under physiological conditions, approximately 90% of active factors remained bound. Compared to control groups, the 3DPs-CMR-BMP2 group significantly enhanced cell proliferation and adhesion. Moreover, the 3DPs-CMR-BMP2 group exhibited more extensive and sustained osteogenic effects through upregulated expression of osteogenic factors and enhanced calcium deposition, as compared to study and control groups. Furthermore, ectopic osteogenesis and a critical calvarial defect model confirmed that the 3DPs-CMR-BMP2 group significantly promoted in vivo bone healing versus control. Thus, our results showed that biomimetic hierarchical 3DPs with a CMR system successfully promote cell proliferation, adhesion, differentiation and osteogenesis, on a continuous cycle. The biomimetic hierarchical 3DPs with a CMR system offers a promising multi-functional, bone substitute material for treatment of patients with bone defects.

Tacrolimus inhibits angiogenesis and induces disaggregation of endothelial cells in spheroids - Toxicity testing in a 3D cell culture approach

The administration of immunosuppressive drugs is a necessary therapeutic measure in organ transplantation to prevent rejections. However, the use of temporarily high dosed immunosuppressive drugs is associated with cytotoxicity and adverse side effects that could induce endothelial dysfunction. The aim of this work is to evaluate the effect of the administrated drugs tacrolimus and mycophenolic acid (MPA) on human umbilical vein endothelial cells (HUVECs). Whereas MPA showed no significant toxicity in a dose-dependent manner, a dose-response curve of tacrolimus treatment could be obtained in 2D monolayer. Due to limited cell-cell and cell-extracellular matrix (ECM) interactions in 2D monolayers, 3D spheroids have been established. The comparison of IC₅₀ values demonstrated that tacrolimus is more toxic towards endothelial cells in 3D spheroids (IC₅₀ value = 27.19 μg/ml) than in 2D monolayers (IC₅₀ value = 40.23 μg/ml). Moreover, the maximal trough level of tacrolimus achieved in immunosuppressive therapy (18 ng/ml) resulted in low disaggregation of the spheroids and decreased vessel areas with increased number of end points of tubular-like structures in the angiogenesis assay even if no toxic effect could be detected. Thus, our approach unseals very sensitive cytotoxic effects of tacrolimus on the vasculature in organ recipients after immunosuppressive therapy.

High-glucose 3D INS-1 cell model combined with a microfluidic circular concentration gradient generator for high throughput screening of drugs against type 2 diabetes

In vitro models for screening of drugs against type 2 diabetes are crucial for the pharmaceutical industry. This paper presents a new approach for integration of a three-dimensionally-cultured insulinoma cell line (INS-1 cell) incubated in a high concentration of glucose as a new model. In this model, INS-1 cells tended to aggregate in the 3D gel (basement membrane extractant, BME), in a similar way to 3D in vivo cell culture models. The proliferation of INS-1 cells in BME was initially promoted and then suppressed by the high concentration of glucose, and the function of insulin secretion also was initially enhanced and then inhibited by the high concentration of glucose. These phenomena were similar to hyperglycemia symptoms, proving the validity of the proposed model. This model can help find the drugs that stimulate insulin secretion. Then, we identified the difference between the new model and the traditional two-dimensional model in terms of cell morphology, inhibition rate of cell proliferation, and insulin secretion. Simultaneously, we developed a circular drug concentration gradient generator based on microfluidic technology. We integrated the high-glucose 3D INS-1 cell model and the circular concentration gradient generator in the same microdevice, tested the utility of this microdevice in the field of drug screening with glipizide as a model drug, and found that the microdevice was more sensitive than the traditional device to screen the anti-diabetic drugs.

Simultaneous delivery of olaparib and carboplatin in PEGylated liposomes imparts this drug combination hypersensitivity and selectivity for breast tumor cells

Combination regiments involving platinum anticancer drugs and agents with unrelated mechanisms of action are a subject of widespread interest. Here, we show that synergistic toxic action in cancer cells of combinations of antitumor platinum drug carboplatin and effective PARP inhibitor olaparib is considerably improved if these combined drugs are encapsulated into liposomes. Notably, the formation of such nano-formulations, called OLICARB, leads to a marked enhancement of activity in human cancer cell lines (including those resistant to conventional platinum antitumor drugs) and selectivity towards tumor cells. We used immunofluorescence analysis of γH2AX expression and examined DNA damage in cancerous cells treated with the investigated compounds. We find that the synergistic toxic effects in cancer cells of both drugs used in combination, nonencapsulated or embedded in the OLICARB nanoparticles, positively correlates with DNA damage. These results also suggest that the enhancement of the toxic effects of carboplatin by olaparib in cancer cells is a consequence of an accumulation of cytotoxic lesions in DNA due to the inhibition of repair of platinated DNA augmented by the synergistic action of olaparib as an effective PARP inhibitor. Our findings also reveal that the combination of olaparib with carboplatin encapsulated in the OLICARB nanoparticles is particularly effective to inhibit the growth of 3D mammospheres. Collectively, the data provide convincing evidence that the encapsulation of carboplatin and olaparib into liposomal constructs to form the OLICARB nanoparticles may represent the viable approach for the treatment of tumors with the aim to eliminate the possible effects of acquired resistance.

Comparative effectiveness of three-dimensional scaffold, differentiation media and co-culture with native cardiomyocytes to trigger in vitro cardiogenic differentiation of menstrual blood and bone marrow stem cells

The main purpose of this study was to find effectiveness of 3D silk fibroin scaffold in comparison with co-culturing in presence of native cardiomyocytes on cardiac differentiation propensity of menstural blood(MenSCs)-versus bone marrow-derived stem-cells (BMSCs). We showed that both 3D fibroin scaffold and co-culture system supported efficient cardiomyogenic differentiation of MenSCs and BMSCs, as judged by the expression of cardiac-specific genes and proteins, Connexin-43, Connexin-40, alpha Actinin (ACTN-2), Tropomyosin1 (TPM1) and Cardiac Troponin T (TNNT2). No significant difference (except for higher expression of ACTN-2 in co-cultured MenSCs) was found between differentiation potential of the cells cultured in 3D fibroin scaffold and co-culture system. Collectively, our results imply that inductive signals served by biological factors of native cardiomyocytes to trigger cardiogenic differentiation of stem-cells may be efficiently provided by natural and biocompatible 3D fibroin scaffold suggesting the usefulness of this construct for cardiac tissue engineering.

A Refined Culture System for Human Induced Pluripotent Stem Cell-Derived Intestinal Epithelial Organoids

Gut epithelial organoids are routinely used to investigate intestinal biology; however, current culture methods are not amenable to genetic manipulation, and it is difficult to generate sufficient numbers for high-throughput studies. Here, we present an improved culture system of human induced pluripotent stem cell (iPSC)-derived intestinal organoids involving four methodological advances. (1) We adopted a lentiviral vector to readily establish and optimize conditioned medium for human intestinal organoid culture. (2) We obtained intestinal organoids from human iPSCs more efficiently by supplementing WNT3A and fibroblast growth factor 2 to induce differentiation into definitive endoderm. (3) Using 2D culture, followed by re-establishment of organoids, we achieved an efficient transduction of exogenous genes in organoids. (4) We investigated suspension organoid culture without scaffolds for easier harvesting and assays. These techniques enable us to develop, maintain, and expand intestinal organoids readily and quickly at low cost, facilitating high-throughput screening of pathogenic factors and candidate treatments for gastrointestinal diseases.

Emerging tumor spheroids technologies for 3D in vitro cancer modeling

Cancer is a leading cause of mortality and morbidity worldwide. Around 90% of deaths are caused by metastasis and just 10% by primary tumor. The advancement of treatment approaches is not at the same rhythm of the disease; making cancer a focal target of biomedical research. To enhance the understanding and prompts the therapeutic delivery; concepts of tissue engineering are applied in the development of in vitro models that can bridge between 2D cell culture and animal models, mimicking tissue microenvironment. Tumor spheroid represents highly suitable 3D organoid-like framework elucidating the intra and inter cellular signaling of cancer, like that formed in physiological niche. However, spheroids are of limited value in studying critical biological phenomenon such as tumor-stroma interactions involving extra cellular matrix or immune system. Therefore, a compelling need of tailoring spheroid technologies with physiologically relevant biomaterials or in silico models, is ever emerging. The diagnostic and prognostic role of spheroids rearrangements within biomaterials or microfluidic channel is indicative of patient management; particularly for the decision of targeted therapy. Fragmented information on available in vitro spheroid models and lack of critical analysis on transformation aspects of these strategies; pushes the urge to comprehensively overview the recent technological advancements (e.g. bioprinting, micro-fluidic technologies or use of biomaterials to attain the third dimension) in the shed of translationable cancer research. In present article, relationships between current models and their possible exploitation in clinical success is explored with the highlight of existing challenges in defining therapeutic targets and screening of drug efficacy.

Aptamer and its applications in neurodegenerative diseases

Aptamers are small single-stranded DNA or RNA oligonucleotide fragments or small peptides, which can bind to targets by high affinity and specificity. Because aptamers are specific, non-immunogenic and non-toxic, they are ideal materials for clinical applications. Neurodegenerative disorders are ravaging the lives of patients. Even though the mechanism of these diseases is still elusive, they are mainly characterized by the accumulation of misfolded proteins in the central nervous system. So it is essential to develop potential measures to slow down or prevent the onset of these diseases. With the advancements of the technologies, aptamers have opened up new areas in this research field. Aptamers could bind with these related target proteins to interrupt their accumulation, subsequently blocking or preventing the process of neurodegenerative diseases. This review presents recent advances in the aptamer generation and its merits and limitations, with emphasis on its applications in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, transmissible spongiform encephalopathy, Huntington's disease and multiple sclerosis.

Responses of MSCs to 3D Scaffold Matrix Mechanical Properties under Oscillatory Perfusion Culture

Both fluid shear stress and matrix stiffness are implicated in bone metabolism and functional adaptation, but the synergistic action of these mechanical cues on the biological behaviors of mesenchymal stem cells (MSCs) is still not well-known. In the present work, a homemade oscillatory flow device was applied to investigate the effects of matrix stiffness on MSCs survival, distribution, and osteogenic differentiation in three-dimensional (3D) conditions. Furthermore, the flow field and cell growth in this bioreactor were theoretically simulated. The results demonstrated that oscillatory shear stress significantly increased the viability and distribution uniformity of MSCs throughout the scaffold after culture for 3 weeks. Compared to static culture, oscillatory shear stress could promote the collagen secretion, mineral deposits, and osteogenic differentiation of MSCs. The findings obtained from this work indicate that the oscillatory perfusion not only provides a higher survival rate and a more uniform distribution of cells but also facilitates osteogenic differentiation of MSCs. Oscillating perfusion bioreactor culture of MSCs in 3D scaffold with optimal matrix stiffness could offer an easy-to-use but efficient bioreactor for bone tissue engineering.

Microfluidic engineering of neural stem cell niches for fate determination

Neural stem cell (NSC) transplantation has great therapeutic potential for neurodegenerative diseases and central nervous system injuries. Successful NSC replacement therapy requires precise control over the cellular behaviors. However, the regulation of NSC fate is largely unclear, which severely restricts the potential clinical applications. To develop an effective model, we designed an assembled microfluidic system to engineer NSC niches and assessed the effects of various culture conditions on NSC fate determination. Five types of NSC microenvironments, including two-dimensional (2D) cellular monolayer culture, 2D cellular monolayer culture on the extracellular matrix (ECM), dispersed cells in the ECM, three-dimensional (3D) spheroid aggregates, and 3D spheroids cultured in the ECM, were constructed within an integrated microfluidic chip simultaneously. In addition, we evaluated the influence of static and perfusion culture on NSCs. The efficiency of this approach was evaluated comprehensively by characterization of NSC viability, self-renewal, proliferation, and differentiation into neurons, astrocytes, or oligodendrocytes. Differences in the status and fate of NSCs governed by the culture modes and micro-niches were analyzed. NSCs in the microfluidic device demonstrated good viability, the 3D culture in the ECM facilitated NSC self-renewal and proliferation, and 2D culture in the static state and spheroid culture under perfusion conditions benefited NSC differentiation. Regulation of NSC self-renewal and differentiation on this microfluidic device could provide NSC-based medicinal products and references for distinct nerve disease therapy.

Three-dimensional cell culture models for investigating human viruses

Three-dimensional (3D) culture models are physiologically relevant, as they provide reproducible results, experimental flexibility and can be adapted for high-throughput experiments. Moreover, these models bridge the gap between traditional two-dimensional (2D) monolayer cultures and animal models. 3D culture systems have significantly advanced basic cell science and tissue engineering, especially in the fields of cell biology and physiology, stem cell research, regenerative medicine, cancer research, drug discovery, and gene and protein expression studies. In addition, 3D models can provide unique insight into bacteriology, virology, parasitology and host-pathogen interactions. This review summarizes and analyzes recent progress in human virological research with 3D cell culture models. We discuss viral growth, replication, proliferation, infection, virus-host interactions and antiviral drugs in 3D culture models.

3D Cell Culturing and Possibilities for Myometrial Tissue Engineering

Research insights into uterine function and the mechanisms of labour have been hindered by the lack of suitable animal and cellular models. The use of traditional culturing methods limits the exploration of complex uterine functions, such as cell interactions, connectivity and contractile behaviour, as it fails to mimic the three-dimensional (3D) nature of uterine cell interactions in vivo. Animal models are an option, however, use of these models is constrained by ethical considerations as well as translational limitations to humans. Evidence indicates that these limitations can be overcome by using 3D culture systems, or 3D Bioprinters, to model the in vivo cytological architecture of the tissue in an in vitro environment. 3D cultured or 3D printed cells can be used to form an artificial tissue. This artificial tissue can not only be used as an appropriate model in which to study cellular function and organisation, but could also be used for regenerative medicine purposes including organ or tissue transplantation, organ donation and obstetric care. The current review describes recent developments in cell culture that can facilitate the development of myometrial 3D structures and tissue engineering applications.

Upscaling of a living membrane for bioartificial kidney device

The limited removal of metabolic waste products in dialyzed kidney patients leads to high morbidity and mortality. One powerful solution for a more complete removal of those metabolites might be offered by a bioartificial kidney device (BAK), which contains a hybrid "living membrane" with functional proximal tubule epithelial cells (PTEC). These cells are supported by an artificial functionalized hollow fiber membrane (HFM) and are able to actively remove the waste products. In our earlier studies, conditionally immortalized human PTEC (ciPTEC) showed to express functional organic cationic transporter 2 (OCT2) when seeded on small size flat or hollow fiber polyethersulfone (PES) membranes. Here, an upscaled "living membrane" is presented. We developed and assessed the functionality of modules containing three commercially available MicroPES HFM supporting ciPTEC. The HFM were optimally coated with L-Dopa and collagen IV to support a uniform and tight monolayer formation of matured ciPTEC under static culturing conditions. Both abundant expression of zonula occludens-1 (ZO-1) protein and limited diffusion of FITC-inulin confirm a clear barrier function of the monolayer. Furthermore, the uptake of 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP⁺), a fluorescent OCT2 substrate, was studied in absence and presence of known OCT inhibitors, such as cimetidine and a cationic uremic solutes mixture. The ASP⁺ uptake by the living upscaled membrane was decreased by 60% in the presence of either inhibitor, proving the active function of OCT2. In conclusion, this study presents a successful upscaling of a living membrane with active organic cation transport as a support for BAK device.

Study of neuroprotective function of Ginkgo biloba extract (EGb761) derived-flavonoid monomers using a three-dimensional stem cell-derived neural model

An in vitro three-dimensional (3D) cell culture system that can mimic organ and tissue structure and function in vivo will be of great benefit for drug discovery and toxicity testing. In this study, the neuroprotective properties of the three most prevalent flavonoid monomers extracted from EGb 761 (isorharmnetin, kaempferol, and quercetin) were investigated using the developed 3D stem cell-derived neural co-culture model. Rat neural stem cells were differentiated into co-culture of both neurons and astrocytes at an equal ratio in the developed 3D model and standard two-dimensional (2D) model using a two-step differentiation protocol for 14 days. The level of neuroprotective effect offered by each flavonoid was found to be aligned with its effect as an antioxidant and its ability to inhibit Caspase-3 activity in a dose-dependent manner. Cell exposure to quercetin (100 µM) following oxidative insult provided the highest levels of neuroprotection in both 2D and 3D models, comparable with exposure to 100 µM of Vitamin E, whilst exposure to isorhamnetin and kaempferol provided a reduced level of neuroprotection in both 2D and 3D models. At lower dosages (10 µM flavonoid concentration), the 3D model was more representative of results previously reported in vivo. The co-cultures of stem cell derived neurons and astrocytes in 3D hydrogel scaffolds as an in vitro neural model closely replicates in vivo results for routine neural drug toxicity and efficacy testing. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:735-744, 2016.

3D Cell-SELEX: Development of RNA aptamers as molecular probes for PC-3 tumor cell line

Human prostate cancer (PCa) is a highly heterogeneous and multifactorial disease. Current clinical biomarkers are not sufficiently accurate, thus being unable to predict the clinical outcome. Therefore, searching for new biomarkers aiming to improve diagnosis, prognosis and therapy is still required. In this study, we performed 3D Cell-SELEX against PC-3 prostate cancer cell line, a novel strategy to select specific nucleic acid ligands against spheroid cells in 3D cell culture. This original system combines Cell-SELEX, a process that exploits the cellular structure to generate specific ligands, and 3D cell culture, an approach that mimics the tissue microenvironment in vitro. In the first round of 3D Cell-SELEX, a negative selection against RWPE-1, non-tumor cell line, was performed to subtract non-tumor specific aptamers. The supernatant was used in eight additional rounds of selection, which were performed against PC-3 cell line. After nine selection cycles, eight PC-3 specific RNA aptamers were selected and sequenced. The aptamers presented sizes between 20 and 50 nucleotides-long, with low free energy (∆G<-13.6), which contributed for their spontaneous folding and high stability. Furthermore, our results showed the aptamer A4 as a specific ligand to prostate tumor cells, with dissociation constant in the nanomolar scale. Therefore, the novel 3D Cell-SELEX procedure improved the selection of PCa cell-surface ligands and the aptamer A4 has shown potential for the identification of prostate tumor cells, suggesting the application of this molecule in further screening assays for PCa.

Perfusion Stirred-Tank Bioreactors for 3D Differentiation of Human Neural Stem Cells

Therapeutic breakthroughs in neurological disorders have been hampered by the lack of accurate central nervous system (CNS) models. The development of these models allows the study of the disease onset/progression mechanisms and the preclinical evaluation of new therapeutics. This has traditionally relied on genetically engineered animal models that often diverge considerably from the human phenotype (developmental, anatomic, and physiological) and 2D in vitro cell models, which fail to recapitulate the characteristics of the target tissue (cell-cell and cell-matrix interactions, cell polarity, etc.). Recapitulation of CNS phenotypic and functional features in vitro requires the implementation of advanced culture strategies, such as 3D culture systems, which enable to mimic the in vivo structural and molecular complexity. Models based on differentiation of human neural stem cells (hNSC) in 3D cultures have great potential as complementary tools in preclinical research, bridging the gap between human clinical studies and animal models. The development of robust and scalable processes for the 3D differentiation of hNSC can improve the accuracy of early stage development in preclinical research. In this context, the use of software-controlled stirred-tank bioreactors (STB) provides an efficient technological platform for hNSC aggregation and differentiation. This system enables to monitor and control important physicochemical parameters for hNSC culture, such as dissolved oxygen. Importantly, the adoption of a perfusion operation mode allows a stable flow of nutrients and differentiation/neurotrophic factors, while clearing the toxic by-products. This contributes to a setting closer to the physiological, by mimicking the in vivo microenvironment. In this chapter, we address the technical requirements and procedures for the implementation of 3D differentiation strategies of hNSC, by operating STB under perfusion mode for long-term cultures. This strategy is suitable for the generation of human 3D neural in vitro models, which can be used to feed high-throughput screening platforms, contributing to expand the available in vitro tools for drug screening and toxicological studies.

Evaluation of CdTe/CdS/ZnS core/shell/shell quantum dot toxicity on three-dimensional spheroid cultures

In this work, three-dimensional (3D) spheroid cultures of human adipose-derived mesenchymal stem cells (hAD-MSCs), with tissue-mimetic morphology through well developed cell-cell and cell-matrix interactions and distinct diffusion/transport characteristics, were assessed for dose-dependent toxic effects of red-emitting CdTe/CdS/ZnS quantum dots (Qdots). Morphological investigations and time-resolved microscopy analysis in addition to cell metabolic activity studies revealed that 3D spheroid cultures are more resistant to Qdot-induced cytotoxicity in comparison to conventional 2D cultures. The obtained results suggest the presence of two distinct cell populations in 2D cultures with different sensitivity to Qdots, however that effect wasn't observed in 3D spheroids. Our investigations were aimed to improve the prediction of nanotoxicity of Qdot on tissue-level and provide the essential screening steps prior to any in vivo application. Moreover, penetration ability of highly fluorescent Qdots to densely-packed spheroids will fortify the biological application of developed Qdots in tissue-like structures.

Zirconium oxide ceramic foam: a promising supporting biomaterial for massive production of glial cell line-derived neurotrophic factor

This study investigated the potential application of a zirconium oxide (ZrO2) ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor (GDNF). Three sets of ZrO2 ceramic foams with different pore densities of 10, 20, and 30 pores per linear inch (PPI) were prepared to support a 3D culturing system. After primary astrocytes were cultured in these systems, production yields of GDNF were evaluated. The biomaterial biocompatibility, cell proliferation and activation of cellular signaling pathways in GDNF synthesis and secretion in the culturing systems were also assessed and compared with a conventional culturing system. In this study, we found that the ZrO2 ceramic foam culturing system was biocompatible, using which the GDNF yields were elevated and sustained by stimulated cell proliferation and activation of signaling pathways in astrocytes cultured in the system. In conclusion, the ZrO2 ceramic foam is promising for the development of a GDNF mass production device for Parkinson's disease treatment.

Three dimensional spheroid cell culture for nanoparticle safety testing

Nanoparticles are widely employed for many applications and the number of consumer products, incorporating nanotechnology, is constantly increasing. A novel area of nanotechnology is the application in medical implants. The widespread use of nanoparticles leads to their higher prevalence in our environment. This, in turn, raises concerns regarding potential risks to humans. Previous studies have shown possible hazardous effects of some nanoparticles on mammalian cells grown in two-dimensional (2D) cultures. However, 2D in vitro cell cultures display several disadvantages such as changes in cell shape, cell function, cell responses and lack of cell-cell contacts. For this reason, the development of better models for mimicking in vivo conditions is essential. In the present work, we cultivated A549 cells and NIH-3T3 cells in three-dimensional (3D) spheroids and investigated the effects of zinc oxide (ZnO-NP) and titanium dioxide nanoparticles (TiO2-NP). The results were compared to cultivation in 2D monolayer culture. A549 cells in 3D cell culture formed loose aggregates which were more sensitive to the toxicity of ZnO-NP in comparison to cells grown in 2D monolayers. In contrast, NIH-3T3 cells showed a compact 3D spheroid structure and no differences in the sensitivity of the NIH-3T3 cells to ZnO-NP were observed between 2D and 3D cultures. TiO2-NP were non-toxic in 2D cultures but affected cell-cell interaction during 3D spheroid formation of A549 and NIH-3T3 cells. When TiO2-NP were directly added during spheroid formation in the cultures of the two cell lines tested, several smaller spheroids were formed instead of a single spheroid. This effect was not observed if the nanoparticles were added after spheroid formation. In this case, a slight decrease in cell viability was determined only for A549 3D spheroids. The obtained results demonstrate the importance of 3D cell culture studies for nanoparticle safety testing, since some effects cannot be revealed in 2D cell culture.

A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nanohydroxyapatite as scaffold for osteochondral regeneration

Fabrication of an injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), nanocrystalline hydroxyapatite (nHAp), and chromium acetate (Cr(iii)) as a novel scaffold for osteochondral repair has been attempted.

Extracellular-matrix-based and Arg-Gly-Asp-modified photopolymerizing hydrogels for cartilage tissue engineering

Articular cartilage damage is a persistent and increasing problem with the aging population. Strategies to achieve complete repair or functional restoration remain a challenge. Photopolymerizing-based hydrogels have long received an attention in the cartilage tissue engineering, due to their unique bioactivities, flexible method of synthesis, range of constituents, and desirable physical characteristics. In the present study, we have introduced unique bioactivity within the photopolymerizing-based hydrogels by copolymerizing polyethylene glycol (PEG) macromers with methacrylated extracellular matrix (ECM) molecules (hyaluronic acid and chondroitin sulfate [CS]) and integrin binding peptides (RGD peptide). Results indicate that cellular morphology, as observed by the actin cytoskeleton structures, was strongly dependent on the type of ECM component as well as the presence of integrin binding moieties. Further, CS-based hydrogel with integrin binding RGD moieties increased the lubricin (or known as superficial zone protein [SZP]) gene expression of the encapsulated chondrocytes. Additionally, CS-based hydrogel displayed cell-responsive degradation and resulted in increased DNA, GAG, and collagen accumulation compared with other hydrogels. This study demonstrates that integrin-mediated interactions within CS microenvironment provide an optimal hydrogel scaffold for cartilage tissue engineering application.

Stromal-cell-derived extracellular matrix promotes the proliferation and retains the osteogenic differentiation capacity of mesenchymal stem cells on three-dimensional scaffolds

To date, expansion of bone-marrow-derived mesenchymal stem cells (MSCs) is typically carried out on two-dimensional (2D) tissue culture plastic. Since this 2D substratum is very different from the physiological situation, MSCs gradually lose their unique multipotent properties during expansion. Recently, the role of the extracellular matrix (ECM) microenvironment ("niche") in facilitating and regulating stem cell behavior in vivo has been elucidated. As a result, investigators have shifted their efforts toward developing three-dimensional (3D) scaffolds capable of functioning like the native tissue ECM. In this study, we demonstrated that stromal-cell-derived ECM, formed within a collagen/hydroxyapatite (Col/HA) scaffold to mimic the bone marrow "niche," promoted MSC proliferation and preserved their differentiation capacity. The ECM was synthesized by MSCs to reconstitute the tissue-specific 3D microenvironment in vitro. Following deposition of the ECM inside Col/HA scaffold, the construct was decellularized and reseeded with MSCs to study their behavior. The data showed that MSCs cultured on the ECM-Col/HA scaffolds grew significantly faster than the cells from the same batch cultured on the regular Col/HA scaffolds. In addition, MSCs cultured on the ECM-Col/HA scaffolds retained their "stemness" and osteogenic differentiation capacity better than MSCs cultured on regular Col/HA scaffolds. When ECM-Col/HA scaffolds were implanted into immunocompromised mice, with or without loading MSCs, it was found that those scaffolds formed less bone as compared with regular Col/HA scaffolds (i.e., without ECM), in both cases of with or without loading MSCs. The in vivo study further confirmed that the ECM-Col/HA scaffold was a suitable mimic of the bone marrow "niche." This novel 3D stromal-cell-derived ECM system has the potential to be developed into a biomedical platform for regenerative medicine applications.