3D Cell Constructs Research Articles

Three-Dimensional In Vitro Hepatic Constructs Formed Using Combinatorial Tapered Stencil for Cluster Culture (TASCL) Device.

Attempts to create artificial liver tissue from various cells have been reported as an alternative method for liver transplantation and pharmaceutical testing. In the construction of artificial liver tissue, the selection of the cell source is the most important factor. However, if an appropriate environment (in vitro/in vivo) cannot be provided for various cells, it is not possible to obtain artificial liver tissue with the desired function. Therefore, we focused on the in vitro environment and produced liver tissues using MEMS technology. In the present study, we report a combinatorial TASCL device to prepare 3D cell constructs in vitro. The TASCL device was fabricated with an overall size of 10 mm × 10 mm with microwells and a top aperture (400 µm × 400 µm, 600 µm × 600 µm, 800 µm × 800 µm) and bottom aperture (40 µm × 40 µm, 80 µm × 80 µm, 160 µm × 160 µm) per microwell. The TASCL device can be easily installed on various culture dishes with tweezers. Using plastic dishes as the bottom surface of the combinatorial TASCL device, 3D hepatocyte constructs of uniform sizes (about ɸ 100 μm-ɸ 200 μm) were produced by increasing the seeding cell density of primary mouse hepatocytes. The 3D hepatocyte constructs obtained using the TASCL device were alive and secreted albumin. On the other hand, partially adhered primary mouse hepatocytes exhibited a cobblestone morphology on the collagen-coated bottom of the individual microwells using the combinatorial TASCL device. By changing the bottom substrate of the TASCL device, the culture environment of the cell constructs was easily changed to a 3D environment. The combinatorial TASCL device described in this report can be used quickly and simply. This device will be useful for preparing hepatocyte constructs for application in drug screening and cell medicine.

An impedance method for spatial sensing of 3D cell constructs--towards applications in tissue engineering.

We present the characterisation and validation of multiplexed 4-terminal (4T) impedance measurements as a method for sensing the spatial location of cell aggregates within large three-dimensional (3D) gelatin scaffolds. The measurements were performed using an array of four rectangular chambers, each having eight platinum needle electrodes for parallel analysis. The electrode positions for current injection and voltage measurements were optimised by means of finite element simulations to maximise the sensitivity field distribution and spatial resolution. Eight different 4T combinations were experimentally tested in terms of the spatial sensitivity. The simulated sensitivity fields were validated using objects (phantoms) with different conductivity and size placed in different positions inside the chamber. This provided the detection limit (volume sensitivity) of 16.5%, i.e. the smallest detectable volume with respect to the size of the measurement chamber. Furthermore, the possibility for quick single frequency analysis was demonstrated by finding a common frequency of 250 kHz for all the presented electrode combinations. As final proof of concept, a high density of human hepatoblastoma (HepG2) cells were encapsulated in gelatin to form artificial 3D cell constructs and detected when placed in different positions inside large gelatin scaffolds. Taken together, these results open new perspectives for impedance-based sensing technologies for non-invasive monitoring in tissue engineering applications providing spatial information of constructs within biologically relevant 3D environments.

Prefabrication of 3D Cartilage Contructs: Towards a Tissue Engineered Auricle – A Model Tested in Rabbits

The reconstruction of an auricle for congenital deformity or following trauma remains one of the greatest challenges in reconstructive surgery. Tissue-engineered (TE) three-dimensional (3D) cartilage constructs have proven to be a promising option, but problems remain with regard to cell vitality in large cell constructs. The supply of nutrients and oxygen is limited because cultured cartilage is not vascular integrated due to missing perichondrium. The consequence is necrosis and thus a loss of form stability. The micro-surgical implantation of an arteriovenous loop represents a reliable technology for neovascularization, and thus vascular integration, of three-dimensional (3D) cultivated cell constructs. Auricular cartilage biopsies were obtained from 15 rabbits and seeded in 3D scaffolds made from polycaprolactone-based polyurethane in the shape and size of a human auricle. These cartilage cell constructs were implanted subcutaneously into a skin flap (15×8 cm) and neovascularized by means of vascular loops implanted micro-surgically. They were then totally enhanced as 3D tissue and freely re-implanted in-situ through microsurgery. Neovascularization in the prefabricated flap and cultured cartilage construct was analyzed by microangiography. After explantation, the specimens were examined by histological and immunohistochemical methods. Cultivated 3D cartilage cell constructs with implanted vascular pedicle promoted the formation of engineered cartilaginous tissue within the scaffold in vivo. The auricles contained cartilage-specific extracellular matrix (ECM) components, such as GAGs and collagen even in the center oft the constructs. In contrast, in cultivated 3D cartilage cell constructs without vascular pedicle, ECM distribution was only detectable on the surface compared to constructs with vascular pedicle. We demonstrated, that the 3D flaps could be freely transplanted. On a microangiographic level it was evident that all the skin flaps and the implanted cultivated constructs were well neovascularized. The presented method is suggested as a promising alternative towards clinical application of engineered cartilaginous tissue for plastic and reconstructive surgery.

A Novel Three-Dimensional Direct Controlled Cell Assembling System

Solid freeform fabrication (SFF) technology has been widely used to fabricate three-dimensional (3D) cell constructs. As multi-cell construct is a heterogeneous object (He-Object), it is a trend of biomanufacturing to use SFF technology to fabricate multi-cell constructs. In this paper, a novel multi-nozzle deposition system, called as 3D direct controlled cell assembling (CA) system, was developed to fabricate 3D multi-cell constructs. The developed system design was demand-oriented and applied functional modular design method. As the key part of this system, the multi-nozzle system was designed and described in details. Experimental study was conducted and results showed that the system could meet the requirements of the process and be used to fabricate complex 3D cell constructs. By comparison, the developed system could precisely deposite biomaterials with high viscocity and form constructs with big size in continuous deposition mode.

3D CELL BIOPRINTING FOR REGENERATIVE MEDICINE RESEARCH AND THERAPIES

Tissue engineering tools and technologies are critical for regenerative medicine and the translational research supporting development of cell-based therapies. 3D cell bioprinting is a relatively new engineering tool being used to design 3D cell constructs (rather than cell suspensions) for transplantation therapies. In this review, we describe a broad range of printing technologies now being used to deliver cells and biomaterials in preclinical studies. We focus on 3D cell bioprinting, in which the building blocks (or 'bioink') used in printing process are three-dimensional cell structures, that are placed by the bioprinter into precise architectures to generate small tissues or organs. 3D cell bioprinting is a flexible research tool for basic and translational stem cell biology.

A contactless electrical stimulator: application to fabricate functional skeletal muscle tissue

Engineered skeletal muscle tissues are ideal candidates for applications in drug screening systems, bio-actuators, and as implantable constructs in tissue engineering. Electrical field stimulation considerably improves the differentiation of muscle cells to muscle myofibers. Currently used electrical stimulators often use direct contact of electrodes with tissue constructs or their culture medium, which may cause hydrolysis of the culture medium, joule heating of the medium, contamination of the culture medium due to products of electrodes corrosion, and surface fouling of electrodes. Here, we used an interdigitated array of electrodes combined with an isolator coverslip as a contactless platform to electrically stimulate engineered muscle tissue, which eliminates the aforementioned problems. The effective stimulation of muscle myofibers using this device was demonstrated in terms of contractile activity and higher maturation as compared to muscle tissues without applying the electrical field. Due to the wide array of potential applications of electrical stimulation to two- and three-dimensional (2D and 3D) cell and tissue constructs, this device could be of great interest for a variety of biological applications as a tool to create noninvasive, safe, and highly reproducible electric fields.

Regulation of autocrine fibroblast growth factor‐2 signaling by perfusion flow in 3D human mesenchymal stem cell constructs

Perfusion bioreactor systems play a crucial role in mitigating nutrient limitation as well as providing biomechanical stimuli and redistributing regulatory macromolecules that influence human mesenchymal stem cells (hMSC) fate in three-dimensional (3D) scaffolds. As fibroblast growth factor-2 (FGF-2) is known to regulate hMSC phenotype, understanding the role of autocrine FGF-2 signaling in the 3D construct under the different perfusion flow provides important insight into an optimal bioreactor design. To investigate FGF-2 signaling inhibition in hMSC cultured in the porous poly(ethylene terephthalate) (PET) scaffolds perfused under two flow configurations, PD173074, an FGFR1 inhibitor, was added in growth media after 7 day of pre-culture and its impact on hMSC proliferation and clonogenicity during the subsequent 7 days of cultivation was analyzed. Compared with control constructs in growth media, the addition of PD173074 resulted in significant reduction in hMSC proliferation and colony formation in both constructs with a more dramatic reduction in the parallel flow constructs. The results demonstrate that autocrine FGF-2 plays a significant role in 3D scaffold and suggest modulation of the perfusion flow in the bioreactor as a strategy to influence autocrine actions and cell fate in the 3D scaffold.

Positron emission tomography detection of human endothelial cell and fibroblast monolayers: effect of pretreament and cell density on 18FDG uptake

BackgroundThe non-destructive assessment and characterization of tridimensional (3D) cell and tissue constructs in bioreactors represents a challenge in tissue engineering. Medical imaging modalities, which can provide information on the structure and function of internal organs and tissues in living organisms, have the potential of allowing repetitive monitoring of these 3D cultures in vitro. Positron emission tomography (PET) is the most sensitive non-invasive imaging modality, capable of measuring picomolar amounts of radiolabeled molecules. However, since PET imaging protocols have been designed almost exclusively for in vivo investigations, suitable methods must be devised to enable imaging of cells or tissue substitutes. As a prior step to imaging 3D cultures, cell radiotracer uptake conditions must first be optimized.MethodsIn this study, human umbilical vein endothelial cells (HUVEC) and human fibroblasts were cultured at different densities and PET was used to non-destructively monitor their glycolytic activity by measuring 18F-fluorodeoxyglucose (18FDG) uptake. Various cell preconditioning protocols were investigated by adjusting the following parameters to optimize 18FDG uptake: glucose starvation, insulin stimulation, glucose concentration, 18FDG incubation time, cell density and radiotracer efflux prevention.ResultsThe conditions yielding optimal 18FDG uptake, and hence best detection sensitivity by PET, were as follows: 2-hour cell preconditioning by glucose deprivation with 1-hour insulin stimulation, followed by 1-hour 18FDG incubation and 15-minute stabilization in standard culture medium, prior to rinsing and PET scanning.ConclusionsA step-wise dependence of 18FDG uptake on glucose concentration was found, but a linear correlation between PET signal and cell density was observed. Detection thresholds of 36 ± 7 and 21 ± 4 cells were estimated for endothelial cells and fibroblasts, respectively.

In vitro reproduction of endochondral ossification using a 3D mesenchymal stem cell construct

Endochondral ossification is one of the essential bone development processes in vertebrates. Although researchers from a variety of fields, including cellular/molecular biology, chemistry, and materials science, have worked to gain a better understanding of the tissue development, integration of findings from these different fields remains a major challenge. An in vitro model system that reproduces endochondral ossification would be a valuable tool for overcoming this problem, because an in vitro standardized model system can be easily accessed by researchers from different fields. Here, we fabricated a large 3D mesenchymal stem cell (MSC) construct with a ball-like morphology, which is termed a cell ball, and cultured it under a hypoxia condition, since hypoxia causes chondrogenic differentiation of MSCs in primordial cartilage, which is crucial for endochondral ossification. Region-specific chondrogenic differentiation of MSCs and mineralization within the cartilage tissue were observed in the cell ball. The precipitated minerals were detected as hydroxyapatite. Consequently, a 3D construct consisting of mineralized tissue surrounded by cartilage tissue was obtained. Moreover, the angiogenic activity of this synthesized tissue changed depending on the chondrogenic phenotype remains in the tissue, which is similar to what happens in the ossification process. Thus, this MSC cell ball system clearly reproduced the initial stage of endochondral ossification in vitro. This system is a promising tool for use as an in vitro model for investigating bone tissue development.

Micro-ring structures stabilize microdroplets to enable long term spheroid culture in 384 hanging drop array plates

Using stereolithography, 20 different structural variations comprised of millimeter diameter holes surrounded by trenches, plateaus, or micro-ring structures were prepared and tested for their ability to stably hold arrays of microliter sized droplets within the structures over an extended period of time. The micro-ring structures were the most effective in stabilizing droplets against mechanical and chemical perturbations. After confirming the importance of micro-ring structures using rapid prototyping, we developed an injection molding tool for mass production of polystyrene 3D cell culture plates with an array of 384 such micro-ring surrounded through-hole structures. These newly designed and injection molded polystyrene 384 hanging drop array plates with micro-rings were stable and robust against mechanical perturbations as well as surface fouling-facilitated droplet spreading making them capable of long term cell spheroid culture of up to 22days within the droplet array. This is a significant improvement over previously reported 384 hanging drop array plates which are susceptible to small mechanical shocks and could not reliably maintain hanging drops for longer than a few days. With enhanced droplet stability, the hanging drop array plates with micro-ring structures provide better platforms and open up new opportunities for high-throughput preparation of microscale 3D cell constructs for drug screening and cell analysis.

Chitosan-poly(butylene succinate) scaffolds and human bone marrow stromal cells induce bone repair in a mouse calvaria model

Tissue engineering sustains the need of a three-dimensional (3D) scaffold to promote the regeneration of tissues in volume. Usually, scaffolds are seeded with an adequate cell population, allowing their growth and maturation upon implantation in vivo. Previous studies obtained by our group evidenced significant growth patterns and osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) when seeded and cultured on melt-based porous chitosan fibre mesh scaffolds (cell constructs). Therefore, it is crucial to test the in vivo performance of these in vitro 3D cell constructs. In this study, chitosan-based scaffolds were seeded and cultured in vitro with hBMSCs for 3 weeks under osteogenic stimulation conditions and analysed for cell adhesion, proliferation and differentiation. Implantation of 2 weeks precultured cell constructs in osteogenic culture conditions was performed into critical cranial size defects in nude mice. The objective of this study was to verify the scaffold integration and new bone formation. At 8 weeks of implantation, scaffolds were harvested and prepared for micro-computed tomography (µCT) analysis. Retrieved implants showed good integration with the surrounding tissue and significant bone formation, more evident for the scaffolds cultured and implanted with human cells. The results of this work demonstrated that chitosan-based scaffolds, besides supporting in vitro proliferation and osteogenic differentiation of hBMSCs, induced bone formation in vivo. Thus, their osteogenic potential in orthotopic location in immunodeficient mice was validated, evidencing good prospects for their use in bone tissue-engineering therapies.

Fabrication of Three-Dimensional Cell Constructs Using Temperature-Responsive Hydrogel

A morphologically controlled three-dimensional (3D) cell construct composed of only cells and having no scaffold material might be a valuable biologic material for tissue engineering applications, as the scaffold materials can cause delay of tissue regeneration in some conditions. To obtain such a 3D cell construct, a 3D thermoresponsive hydrogel (poly-N-isopropylacrylamide) was prepared as a mold material that changes its volume depending on the temperature. Three-dimensional osteoblast cell constructs with a variety of morphologies as well as a monolayered cell sheet were obtained by decreasing the surrounding temperature of the hydrogel designed with a predefined shape and formed by curing in a polymer mold manufactured via 3D printing. The cell sheet or 3D cell constructs detachment resulted from a simple change in the gel volume, not by the surface chemistry of the gel, because the surface hydrophilicity of the gel was maintained over a wide temperature range. These 2D/3D cell constructs have numbers of exciting applications such as cell carriers for tissue regeneration or as model tissues for the biological study.

Three-dimensional early retinal progenitor 3D tissue constructs derived from human embryonic stem cells

PurposeTo develop three-dimensional (3D) constructs of retinal pigment epithelium (RPE) and early retina progenitor cells from human embryonic stem cells (hESCs). Methods3D tissue constructs were developed by culturing hESC-derived neural retinal progenitors in a matrix on top of hESC-derived RPE cells in a cell culture insert. An osmolarity gradient maintained the nutrition of the 3D cell constructs. Cross-sections through hESC-derived tissue constructs were characterized by immunohistochemistry for various transcription factors and cell markers. ResultshESC-derived tissue constructs expressed transcription factors characteristic of retinal development, such as pax6, Otx2, Chx10, retinal RAX; Brn3b (necessary for differentiation of retinal ganglion cells); and crx and nrl (role in photoreceptor development). Many cells expressed neuronal markers including nestin, beta-tubulin and microtubule-associated proteins. ConclusionsThis study shows for the first time that 3D early retinal progenitor tissue constructs can be derived from hESCs.

Editorial: Tissue Engineering: Perspectives, Challenges, and Future Directions

Editorial: Tissue Engineering: Perspectives, Challenges, and Future Directions

Y chromosome detection of three-dimensional tissue-engineered skeletal muscle constructs in a syngeneic rat animal model.

Surgical reconstruction of muscle tissue lost by trauma or tumor ablation is limited by the lack of availability of functional native tissue substitution. Moreover, so far most inherited or acquired muscle diseases are lacking sufficient treatment, because only few alternatives exist to provide functional restoration of lost muscle tissues. Engineering those tissues and transplantation into sites of dysfunction may be an alternative approach and may allow replacement of such damaged or failing skeletal muscle tissues. Techniques attempting reconstruction of some human tissues and organs (tissue engineering) have been introduced into clinical practice recently. One major problem that previous transplantation studies were facing is the ability of detection of transplanted cells after integration. Using the Y chromosome in situ hybridization technique in a syngeneic rat model allows transplantation of cell constructs orthotopically, without manipulation of the cells, with no rejection or immunosuppression being implied, but providing a nondilutable genetic marker to identify transplanted cells. The purpose of our study was to create functional skeletal muscle tissue in vivo using the transplantation of primary myoblasts precultivated within a three-dimensional (3D) fibrin matrix and to determine the fate of the transplanted cells using the Y chromosome detection technique. 3D myoblast cultures were established derived from male donor rats and after 7 days of cultivation we performed an orthotopic transplantation of 3D cell constructs into a created muscle defect within the gracilis muscle of syngeneic female rats. Anti-desmin immunostaining and Y chromosome in situ hybridization indicated the survival and integration of transplanted male myoblasts into the female recipient animal, thus demonstrating the feasibility of this approach in tissue engineering and the research of cell transplantation in general.