Quantitative recording of vitality patterns in living multicellular spheroids by confocal microscopy

Equations describing semi-confluent cell growth (I) Analytical approximations

A set of differential equations with analytical solutions are presented that can quantitatively account for variable degrees of contact inhibition on cell growth in two- and three-dimensional cultures. The developed equations can be used for comparative purposes when assessing contribution of higher-order effects, such as culture geometry and nutrient depletion, on mean cell growth rate. These equations also offer experimentalists the opportunity to characterize cell culture experiments using a single reductive parameter.

The Influence of Antitumor Unsymmetrical Bisacridines on 3D Cancer Spheroids Growth and Viability

The culture of 3D spheroids is a promising tool in drug development and testing. Recently, we synthesized a new group of compounds, unsymmetrical bisacridines (UAs), which exhibit high cytotoxicity against various human cell lines and antitumor potency against several xenografts. Here, we describe the ability of four UAs—C-2028, C-2041, C-2045, and C-2053—to influence the growth of HCT116 and H460 spheres and the viability of HCT116 cells in 3D culture compared with that in 2D standard monolayer culture. Spheroids were generated using ultra-low-attachment plates. The morphology and diameters of the obtained spheroids and those treated with UAs were observed and measured under the microscope. The viability of cells exposed to UAs at different concentrations and for different incubation times in 2D and 3D cultures was assessed using 7-AAD staining. All UAs managed to significantly inhibit the growth of HCT116 and H460 spheroids. C-2045 and C-2053 caused the death of the largest population of HCT116 spheroid cells. Although C-2041 seemed to be the most effective in the 2D monolayer experiments, in 3D conditions, it turned out to be the weakest compound. The 3D spheroid culture seems to be a suitable method to examine the efficiency of new antitumor compounds, such as unsymmetrical bisacridines.

Long-term fluorescence hyperspectral imaging of on-chip treated co-culture tumour spheroids to follow clonal evolution

Multicellular tumour spheroids are an ideal in vitro tumour model to study clonal heterogeneity and drug resistance in cancer research because different cell types can be mixed at will. However, measuring the individual response of each cell population over time is challenging: current methods are either destructive, such as flow cytometry, or cannot image throughout a spheroid, such as confocal microscopy. Our group previously developed a wide-field fluorescence hyperspectral imaging system to study spheroids formed and cultured in microfluidic chips. In the present study, two subclones of a single parental ovarian cancer cell line transfected to express different fluorophores were produced and co-culture spheroids were formed on-chip using ratios forming highly asymmetric subpopulations. We performed a 3D proliferation assay on each cell population forming the spheroids that matched the 2D growth behaviour. Response assays to PARP inhibitors and platinum-based drugs were also performed to follow the clonal evolution of mixed populations. Our experiments show that hyperspectral imaging can detect spheroid response before observing a decrease in spheroid diameter. Hyperspectral imaging and microfluidic-based spheroid assays provide a versatile solution to study clonal heterogeneity, able to measure response in subpopulations presenting as little as 10% of the initial spheroid.

Long term morphological characterization of mesenchymal stromal cells 3D spheroids built with a rapid method based on entry-level equipment

Three-dimensional (3D) spheroids of mesenchymal stromal cells (MSC) have been demonstrated to improve a wide range of MSC features, such as multilineage potential, secretion of therapeutic factors, and resistance against hypoxic condition. Accordingly, they represent a promising tool in regenerative medicine for several biological and clinical applications. Many approaches have been proposed to generate MSC spheroids. They usually require specific generation systems, such as rotatory bioreactors or low-attachment plates, and each approach has its own disadvantages. Furthermore, an over-time analysis of morphological homogeneity and architectural stability of the spheroids generated is rarely provided. In this work we adapted the "pellet culture" method to obtain homogenous spheroids of MSC and maintain them in vitro for long term studies. We analysed their outer and inner structure over a 2-month period to provide morphological and architectural information regarding the spheroids generated. Quantitative and qualitative data were obtained using brightfield and confocal microscope imaging coupled to a computational analysis to estimate volume, sphericity, and jagging degree. In addition, histological evaluation was performed to more thoroughly assess the cellular composition and the internal architecture of the 3D spheroids. The results provided show that MSC spheroids generated with the proposed approach are homogeneous and stable, from both morphological and architectural points of view, for a period of at least 15 days, approximately between day 15 and day 30 after their generation. Accordingly, the approach proposed serves as a rapid, cost-effective, and efficient method to generate and maintain MSC spheroids using common entry-level laboratory equipment only.

Enhancing proliferation and osteogenic differentiation of HMSCs on casein/chitosan multilayer films

Creating a bioactive surface is important in tissue engineering. Inspired by the natural calcium binding property of casein (CA), multilayer films ((CA/CS)n) with chitosan (CS) as polycation were fabricated to enhance biomineralization, cell adhesion and differentiation. LBL self-assembly technique was used and the assembly process was intensively studied based on changes of UV absorbance, zeta potential and water contact angle. The increasing content of chitosan and casein with bilayers was further confirmed with XPS and TOF-SIMS analysis. To improve the biocompatibility, gelatin was surface grafted. In vitro mineralization test demonstrated that multilayer films had more hydroxyapatite crystal deposition. Human mesenchymal stem cells (HMSCs) were seeded onto these films. According to fluorescein diacetate (FDA) and cell cytoskeleton staining, MTT assay, expression of osteogenic marker genes, ALP activity, and calcium deposition quantification, it was found that these multilayer films significantly promoted HMSCs attachment, proliferation and osteogenic differentiation than TCPS control.

Digital microfluidics for automated hanging drop cell spheroid culture

Cell spheroids are multicellular aggregates, grown in vitro, that mimic the three-dimensional morphology of physiological tissues. Although there are numerous benefits to using spheroids in cell-based assays, the adoption of spheroids in routine biomedical research has been limited, in part, by the tedious workflow associated with spheroid formation and analysis. Here we describe a digital microfluidic platform that has been developed to automate liquid-handling protocols for the formation, maintenance, and analysis of multicellular spheroids in hanging drop culture. We show that droplets of liquid can be added to and extracted from through-holes, or "wells," and fabricated in the bottom plate of a digital microfluidic device, enabling the formation and assaying of hanging drops. Using this digital microfluidic platform, spheroids of mouse mesenchymal stem cells were formed and maintained in situ for 72 h, exhibiting good viability (>90%) and size uniformity (% coefficient of variation <10% intraexperiment, <20% interexperiment). A proof-of-principle drug screen was performed on human colorectal adenocarcinoma spheroids to demonstrate the ability to recapitulate physiologically relevant phenomena such as insulin-induced drug resistance. With automatable and flexible liquid handling, and a wide range of in situ sample preparation and analysis capabilities, the digital microfluidic platform provides a viable tool for automating cell spheroid culture and analysis.

A microfluidic system for investigation of extravascular transport and cellular uptake of drugs in tumors

Three-dimensional (3D) tumor models have been established in various microfluidic systems for drug delivery and resistance studies in vitro. However, one of the main drawbacks of these models is non-uniform distribution of cells, leaving regions with very low cell density within the 3D structures. As a result, molecular diffusion in the cell compartments is faster than that observed in solid tumors. To solve this problem, we developed a new technique for preparation of 3D tumor models in vitro. It was based on a microfluidic device containing three parallel channels separated by narrowly spaced posts. Tumor cells were loaded into the central channel at high density. To test the system, B16.F10 melanoma cells were perfusion-cultured overnight and the resulting 3D structure was characterized in terms of viability, density, and morphology of cells as well as transport properties of small fluorescent molecules. Immediately upon loading of tumor cells, the cell density was comparable to those observed in B16.F10 tumor tissues in vivo; and the viability of tumor cells was maintained through the overnight culture. The tumor model displayed low extracellular space and high resistance to diffusion of small molecules. For membrane-permeant molecules (e.g., Hoechst 33342), the rate of interstitial penetration was extremely slow, compared to membrane-impermeant molecules (e.g., sodium fluorescein). This versatile tumor model could be applied to in vitro studies of transport and cellular uptake of drugs and genes.

In Vivo Evaluation of Butylene Terephthalate-ethylene Oxide-DL, Lactide Polymer as Porous Scaffolds for Tissue Engineering

The copolymers of poly(1,4-butylene terephthalate-co-ethylene oxide-co-DL-lactide), obtained by the transesterification reactions of poly(butylenes terephthalate) with poly(ethylene glycol DL-oligo(lactic acid), were fabricated into porous scaffolds by the established solvent-casting and particulate-leaching technique with NaCl as the porogen. The morphology of the porous scaffolds were investigated by the scanning electron microscopy (SEM), and the pores within the scaffold were proven to be interconnective ranging in size from 200 to 400 μm. The human bone marrow mesenchymal stem cells (MSC) seeded on the scaffolds were confirmed to survive and proliferate within the pores of the scaffold with the observation by immunofluorescence microscope and SEM. In vivo implantation of MSC-seeded scaffolds into athymic nude mice showed significant tissue formation in the subcutaneous sites of the immunodeficient mice at 3, 4, 6, and 9 weeks. The results indicate that the scaffolds were biocompatible with MSC and the host tissue in vitro and in vivo.

Essential operating principles for tumor spheroid growth

BACKGROUND

Our objective was to discover in silico axioms that are plausible representations of the operating principles realized during characteristic growth of EMT6/Ro mouse mammary tumor spheroids in culture. To reach that objective we engineered and iteratively falsified an agent-based analogue of EMT6 spheroid growth. EMT6 spheroids display consistent and predictable growth characteristics, implying that individual cell behaviors are tightly controlled and regulated. An approach to understanding how individual cell behaviors contribute to system behaviors is to discover a set of principles that enable abstract agents to exhibit closely analogous behaviors using only information available in an agent's immediate environment. We listed key attributes of EMT6 spheroid growth, which became our behavioral targets. Included were the development of a necrotic core surrounded by quiescent and proliferating cells, and growth data at two distinct levels of nutrient.

RESULTS

We then created an analogue made up of quasi-autonomous software agents and an abstract environment in which they could operate. The system was designed so that upon execution it could mimic EMT6 cells forming spheroids in culture. Each agent used an identical set of axiomatic operating principles. In sequence, we used the list of targeted attributes to falsify and revise these axioms, until the analogue exhibited behaviors and attributes that were within prespecified ranges of those targeted, thereby achieving a level of validation.

CONCLUSION

The finalized analogue required nine axioms. We posit that the validated analogue's operating principles are reasonable representations of those utilized by EMT6/Ro cells during tumor spheroid development.

Poly(lactic acid) scaffold fabricated by gelatin particle leaching has good biocompatibility for chondrogenesis

Three-dimensional poly(L-lactic acid) (PLLA) scaffolds with high porosity and an average pore size of 280-450 microm were fabricated using gelatin particles as porogen. The particles were bonded together by incubation in saturated water vapor at 70 degrees C for 3.5 h. After casting the PLLA/1,4-dioxane solution, freeze-drying and porogen leaching with 70 degrees C water, a porous scaffold with well-interconnected pores and some nano-fibers was obtained. The biological performance of the scaffold was evaluated by in vitro chondrocyte culture and in vivo implantation. In comparison with the control scaffold fabricated with NaCl particles as porogen under the same conditions, the experimental scaffold had better biological performance because the gelatin molecules were stably entrapped onto the pore surfaces. A larger number of cells in the experimental scaffold were observed by confocal laser scanning microscopy after the viable cells had been stained with fluorescein diacetate. The chondrocytes showed more spreading morphology. Higher cytoviability and secretion of glycosaminoglycan (GAG) were also determined in the experimental scaffold. After implantation of the chondrocytes/PLLA scaffold construct to the subcutaneous dorsum of nude mice for 30-120 days, cartilage-like specimens were harvested. Histological examination showed that the regenerated cartilages had a large quantity of collagen and GAG.

Novel application of multicellular layers culture for in situ evaluation of cytotoxicity and penetration of paclitaxel

Limited drug penetration into tumor tissue is one of the major factors causing clinical drug resistance in human solid tumors. The multicellular layers (MCL) of human cancer cells have been successfully used to study tissue pharmacokinetics of anticancer drugs. The purpose of this study was to develop a direct and simple method to evaluate vitality changes in situ within MCL using calcein-AM. Human colorectal (DLD-1, HT-29) and bladder (HT-1376, J-82) cancer cells were grown in Transwell inserts to form MCL and subjected to paclitaxel exposure. The drug distribution was evaluated using paclitaxel-rhodamine. Photonic attenuation and limited penetration of calcein-AM prevented cellular vitality evaluation on optical sections under confocal microscopy in DLD-1 MCL. However, direct measurement of the fluorescence intensity on frozen sections of MCL allowed successful vitality assessment in more than 80% depth for HT-29 and J-82 MCL and in the upper 40% depth for DLD-1 and HT-1376 MCL. The penetration of paclitaxel-rhodamine was greater in HT-29 than DLD-1 and its distribution pattern was correlated to the spatial profile of vitality deterioration in both MCL, suggesting that tissue penetration may be an important determinant of drug effect in tumors. In conclusion, a novel method for vitality evaluation in situ within MCL was developed using calcein-AM. This method may provide clinically relevant data regarding the spatial pharmacodynamics of anticancer agents within avascular regions of solid tumors.

Layer-by-layer assembly of chondroitin sulfate and collagen on aminolyzed poly(L-lactic acid) porous scaffolds to enhance their chondrogenesis

Layer-by-layer (LBL) assembly of cytocompatible chondroitin sulfate (CS) and collagen type I (Col) onto PLLA scaffolds were implemented to enhance the cell-material interaction. To introduce charges onto the hydrophobic and neutral PLLA surface so that the electronic assembly can be processed, the PLLA was aminolyzed in hexane diamine solution to obtain free amino groups that are positively charged at neutral pH. Ultaviolet-visible spectroscopy and ninhydrin analysis verified the consecutive deposition of CS/Col multilayers on the aminolyzed PLLA membranes. Confocal laser scanning microscopy (CLSM) observation and hydroxyproline quantification revealed the process of LBL assembly of CS/Col multilayers in the interior of PLLA porous scaffolds. In vitro chondrocyte culture found that the presence of CS and Col greatly improved the cytocompatibility of the PLLA scaffolds in terms of cell attachment, proliferation, cytoviability and GAG secretion.

Hydrogel-filled polylactide porous scaffolds for cartilage tissue engineering

Polymer porous scaffolds and hydrogels have been separately employed as analogues of the native extra-cellular matrix (ECM). However, both of these two kinds of materials have their own advantages and shortcomings. In this work, an attempt to combine the advantages of these two kinds of materials is carried out. Poly-L-lactide (PLLA) scaffolds with good mechanical properties were prepared by thermally induced phase separation, which were then filled with hydrogel aiming at entrapment of cells within a support of predefined shape. Agar, which has a function to promote chondrogenesis, was selected to entrap chondrocytes, acting as analogues of native ECM. A straight forward merit of this construct is that both mechanical strength and macroscopic shape, and analogous ECM can be simultaneously achieved. The morphology and distribution of the chondrocytes were studied by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The cell growth behaviors were determined by MTT assay and collagen and glycosaminoglycan (GAG) secretion. After culture for 7 and 14 days, the cells in the construct were round and surrounded by the hydrogel. The MTT viability and the cell secretion in the chondrocytes/agar/scaffold construct were also higher than that of the chondrocytes/scaffold construct (control). Gelatin was further introduced into the construct, yielding improved GAG secretion and cytoviability. After implantation in the subcutaneous dorsum of nude mice for 4 weeks, cartilage-like specimens maintaining their original rectangular shapes were harvested. Histological examination showed that new cartilage was regenerated and a large quantity of collagen and GAG were secreted, while the cells in the control PLLA scaffold turned to be fibroblast-like with less secretion of extracellular matrices. The method provides a useful pathway of scaffold preparation and cell transplantation, which can achieve suitable mechanical properties and good cell performance simultaneously.

In vitro and in vivo degradability and cytocompatibility of poly(l-lactic acid) scaffold fabricated by a gelatin particle leaching method

Porous poly(l-lactic acid) (PLLA) scaffolds fabricated by a gelatin particle-leaching technique have good mechanical property and cytocompatibility, as demonstrated by a previous in vitro study. Here we investigate further the in vitro degradation of the scaffolds in terms of weight loss, water uptake, weight-average molecular weight, thermal behavior and morphology during a 39 week period in phosphate-buffered saline. The water uptake decreased dramatically during the initial stage due to release of the remaining gelatin, and then increased slightly with degradation time. The weight-average molecular weight decreased linearly as a function of time, while the crystallinity steadily increased with slightly decreased melting temperature. After degradation, many defects and big holes were seen in the scaffolds by scanning electron microscopy. Cartilage regeneration and scaffold disappearance in vivo were compared by implanting the construct into nude mice for 30-120 days. While the scaffolds maintained their intact pore structure after 23 weeks of degradation in vitro, they almost disappeared in vivo at the same time, implying a faster degradation rate in vivo. By 120 days after implantation, the scaffolds were hardly seen in the newly formed cartilage-like tissue. The regenerated cartilages could not maintain their predesigned shape after a long period of in vivo culture due to the weakening of the mechanical strength of the constructs as a result of PLLA degradation. The regions occupied initially by PLLA scaffold were filled later by collagen type II secreted by the chondrocytes, but with no evident basophilic proteoglycan.

Efficient formation of uniform-sized embryoid bodies using a compartmentalized microchannel device

The formation of spherical aggregates of cells called embryoid bodies (EBs) is an indispensable step in many protocols in which embryonic stem (ES) cells are differentiated to other cell types. Appropriate morphology and embryo size are critical for the sequential developmental stages of naturally conceived embryos. Likewise, regulating the size of EBs and the timing of their formation is crucial for controlling the differentiation of ES cells within the EB. Existing methods of formation of EBs, however, are tedious or provide heterogeneously-sized EBs. Here we describe a microfluidic system for straightforward synchronized formation of uniform-sized EBs, the size of which can be controlled by changing the cross-sectional size of microchannels in the microfluidic device. The device consists of two microchannels separated by a semi-porous polycarbonate membrane treated to be resistant to cell adhesion. ES cells introduced into the upper channel self-aggregate to form uniformly-sized EBs. The semi-porous membrane also allows subsequent treatment of the non-attached EBs with different reagents from the lower channel without the need for wash out because of the compartmentalization afforded by the membrane. This method provides a simple yet robust means to control the formation of EBs and the subsequent differentiation of ES cells in a format compatible for ES cell processing on a chip.

Bone Repair Analysis in a Novel Biodegradable Hydroxyapatite/Collagen Composite Implanted in Bone

The purpose of this study was to evaluate a biodegradable hydroxyapatite/collagen composite and to examine the use of the calcium ion contained for bone formation and growth. Surgical holes were prepared in the femora and tibiae of beagle dogs, and were filled with the hydroxyapatite/collagen composite labeled with alizarin red. After 4 weeks, calcein was administered to the experimental dogs. After 1 additional week, the femora and tibiae were removed surgically and fixed in formalin. Light microscopy and confocal laser scanning microscopy were used to examine the surgical holes with their implanted materials and the surrounding bone. There were only a few inflammatory cells adjacent to the hydroxyapatite/collagen composite. The newly formed bone in the cortical bone was stained with calcein, which binds to serum calcium, and new bone near the hydroxyapatite/collagen composite in the holes was stained positive for alizarin red, which binds to the calcium in the hydroxyapatite/collagen composite. In addition, osteoblasts near the hydroxyapatite/collagen composite as well as newly formed bone adjacent to the osteoblasts showed alizarin red staining, but the new bone at a distance from the hydroxyapatite/collagen implant reacted only to calcein staining. These results, using the tissue labeling method with calcein and alizarin red, suggested that the calcium bound to the alizarin red released from the hydroxyapatite/collagen composite materials might have been translocated to sites of new bone formation. The present experiment showed that the novel hydroxyapatite/collagen composite is a useful implant material for bone augmentation and that the calcium in the newly formed bone might have been released from the implant.

Triple-coated stents (Hirudin/Iloprost/Paclitaxel): an in vitro approach for characterizing the antiproliferative potential of each individual compound

BACKGROUND

Hirudin (H)/iloprost (I)/paclitaxel (P)-coated stents represent a multifactorial approach to reducing the proliferative response caused by ballooning and stenting. The study presented compares the net effect of each individual compound of HIP-coated stents with the summed effect of the compounds in the stent coating.

METHODS AND RESULTS

For proliferation prescreening studies, human coronary smooth muscle cells were incubated with H (0.005-500 microg/ml), I (0.00001-1 microg/ml), and P (0.0001-10 microg/ml). After 5 days, cell number was studied in a cell analyzer system. Secondly, 8-mm stents were coated with (1) HI, (2) HIP-10 microg/20 microg/40 microg (HIP5%/10%/20%), (3) P-40 microg (P), (4) IP-40 microg (IP), and (5) HP-40 microg (HP). After 5 days, the effect on cell proliferation and cytoskeletal structures was studied. No antiproliferative effect was found after incubation with H; significant inhibition was seen after incubation with I (p<0.05) or lipophilically dissolved P (p<0.001). After 5 days incubation with HIP5%-, HIP10%-, HIP20%-, P20%-, IP20%-, and HP20%-coated stents, cell proliferation was inhibited by 55.5% (p<0.05), 61% (p<0.05), 57.9% (p<0.05), 59.5% (p<0.001), 59.8% (p<0.001), and 63.3% (p<0.001), respectively. HI- and HIP-coated stents caused a severe destruction of the cytoskeletal structures smooth muscle alpha-actin and alpha-tubulin; despite the destruction, vital cells could be identified with positive FDA staining.

CONCLUSIONS

Although both lipophilically dissolved P and hydrophilically dissolved I contributed to the antiproliferative effect, no additive effect of the two compounds was detected. In vivo P can be released more easily from the coating material due to the permanent lipophilic contact of the stent struts with the vessel wall. The current study is the first report on a clear and uncomplicated technique to obtain information on the antiproliferative potential of coated stents before large experimental studies are initiated.

Quantification of viability in organotypic multicellular spheroids of human malignant glioma using lactate dehydrogenase activity: a rapid and reliable automated assay

Organotypic spheroids from malignant glioma resemble the biological complexity of the original tumor and are therefore appealing to study anticancer drug responses. Accurate and reproducible quantification of response effect has been lacking to determine drug responses in this three-dimensional tumor model. Lactate dehydrogenase (LDH) activity was demonstrated in cryostat sections of spheroids using the tetrazolium salt method. Calibrated digital image acquisition of the stained cryostat sections enables quantification of LDH activity. Fully automated image cytometry reliably demarcates LDH-active and LDH-inactive tissue areas by thresholding at specific absorbance values. The viability index (VI) was calculated as ratio of LDH-active areas and total spheroid tissue areas. Duplicate staining and processing on the same tissue showed good correlation and therefore reproducibility. Sodium azide incubation of spheroids induced reduction in VI to almost zero. We conclude that quantification of viability in cryostat sections of organotypic multicellular spheroids from malignant glioma can be performed reliably and reproducibly with this approach.

Evaluation of different types of alginate microcapsules as bioreactors for producing endostatin

The use of nonautologous cell lines producing a therapeutic substance encapsulated within alginate microcapsules could be an alternative way of treating different diseases in a cost-effective way. Malignant brain tumors have been proposed to be treated locally using engineered cells secreting proteins with therapeutic potential encapsulated within alginate microcapsules. Optimization of the alginate capsule bioreactors is needed before this treatment can be a reality. Recently, we have demonstrated that alginate-poly-L-lysine microcapsules made with high-G alginate and a gelled core disintegrated as cells proliferated. In this study we examined the growth and endostatin secretion of 293-EBNA (293 endo) cells encapsulated in six different alginate microcapsules made with native high-G alginate or enzymatically tailored alginate. Stability studies using an osmotic pressure test showed that alginate-poly-L-lysine-alginate microcapsules made with enzymatically tailored alginate was mechanically stronger than alginate capsules made with native high-G alginate. Growth studies showed that the proliferation of 293 endo cells was diminished in microcapsules made with enzymatically tailored alginate and gelled in a barium solution. Secretion of endostatin was detected in lower amounts from the enzymatically tailored alginate microcapsules compared with the native alginate microcapsules. The stability of the alginate microcapsules diminished as the 293 endo cells grew inside the capsules, while empty alginate microcapsules remained stable. By using microcapsules made of fluorescenamine-labeled alginate it was clearly visualized that cells perforated the alginate microcapsules as they grew, destroying the alginate network. Soluble fluorescence-labeled alginate was taken up by the 293 endo cells, while alginate was not detected in live spheroids within fluorescence-labeled alginate microcapsules. Despite that increased stability was achieved by using enzymatically tailored alginate, the cell proliferation destroyed the alginate microcapsules with time. It is therefore necessary to use cell lines that have properties more suited for alginate encapsulation before this technology can be used for therapy.

Comparison of necrosis in human ovarian tissue after conventional slow freezing or vitrification and transplantation in ovariectomized SCID mice

This paper examines and compares necrosis in human ovarian tissue after conventional slow freezing or vitrification and ensuing xenotranplantation. Slow cryoconserved or vitrified ovarian tissue samples and fresh controls from nine patients were subcutaneously transplanted into SCID mice. The tissue samples were explanted after 6 weeks and the necrotic areas were examined by staining with Lucifer yellow SV. The size of the necrotic areas in parallel cultivated ovarian tissue samples was compared, as was necrosis in cultivated prostate tumour spheroids where the emergence of necrosis and its pathophysiological correlation have been described. Examinations showed no significant rise in the proportion of necrotic areas after slow cryoconservation/transplantation and in the controls (transplanted fresh tissue, not transplanted fresh tissue, long-term culture). The proportion of necrotic areas in the tumour spheroids was significantly higher than in the ovarian tissue. Vitrification could, after these results, be presented as an alternative to conventional slow cryoconservation.

Visualization of alginate-poly-L-lysine-alginate microcapsules by confocal laser scanning microscopy

Confocal laser scanning microscopy (CLSM) was used to study the distribution of polymers and cross-linking ions in alginate-poly-L-lysine (PLL) -alginate microcapsules made by fluorescent-labeled polymers. CLSM studies of Ca-alginate gel beads made in the presence and absence of non-gelling sodium ions revealed a more inhomogeneous distribution of alginate in beads formed in the absence of non-gelling ions. In the formation of alginate-PLL capsules, the polymer gradients in the preformed gel core were destabilized by the presence of non-gelling ions in the washing step and in the PLL solution. Ca-alginate gels preserved the inhomogeneous structure by exposure to ion-free solution in contrast to exposure to non-gelling ions (Na(+)). By exchanging Ca(2+) with Ba(2+) (10 mM), extremely inhomogeneous gel beads were formed that preserved their structure during the washing and exposure to PLL in saline. PLL was shown to bind at the very surface of the alginate core, forming a shell-like membrane. The thickness of the PLL-layer increased about 100% after 2 weeks of storage, but no further increase was seen after 2 years of storage. The coating alginate was shown to overlap the PLL layer. No difference in binding could be observed among coating alginates of different composition. This paper shows an easy and novel method to study the distribution of alginate and PLL in intact microcapsules. As the labeling procedures are easy to perform, the method can also be used for a variety of other polymers in other microencapsulation systems.

Inhibition of tumor-induced angiogenesis and matrix-metalloproteinase expression in confrontation cultures of embryoid bodies and tumor spheroids by plant ingredients used in traditional chinese medicine

Tumor-induced angiogenesis is a prerequisite for excessive tumor growth. Blood vessels invade the tumor tissue after degradation of the extracellular matrix scaffold by matrix metalloproteinases (MMPs). Inhibition of MMPs has been therefore suggested to be a useful tool to abolish neoangiogenesis of solid tumors. In the present study, antioxidative plant ingredients used in traditional Chinese medicine were investigated for their capacity to down-regulate MMP expression and to inhibit angiogenesis in embryonic stem cell-derived embryoid bodies and tumor-induced angiogenesis in confrontation cultures consisting of embryoid bodies and multicellular DU-145 prostate tumor spheroids. Embryoid bodies transiently expressed MMP-1, MMP-2, and MMP-9 during the time of differentiation of capillary-like structures. In confrontation cultures, MMP expression was increased compared with control tumor spheroids and embryoid bodies cultivated separately. The increased expression of MMPs in confrontation cultures was a result of elevated levels of reactive oxygen species (ROS) upon confrontation culture and was totally abolished in the presence of the free radical scavenger vitamin E. Incubation of embryoid bodies with baicalein, epicatechin, berberine, and acteoside, which are herbal ingredients used in traditional Chinese medicine, significantly inhibited angiogenesis in embryoid bodies and decreased intracellular ROS levels. Tumor-induced angiogenesis in confrontation cultures was totally abolished in the presence of the free radical scavenger vitamin E. Because herbal ingredients down-regulated MMP expression, we conclude that ROS generated during confrontation culture induce the expression of MMPs that are necessary for endothelial cell invasion into the tumor tissue.

Tumor-induced angiogenesis studied in confrontation cultures of multicellular tumor spheroids and embryoid bodies grown from pluripotent embryonic stem cells

Tumor vascularization is the rate-limiting step for the progression of cancer. Differential steps of tumor-induced angiogenesis were studied by a novel in vitro confrontation culture of avascular multicellular prostate tumor spheroids and embryoid bodies grown from pluripotent embryonic stem (ES) cells. Vascularization in embryoid bodies started on day 5 of cell culture and was paralleled by down-regulation of hypoxia-inducible factor 1 alpha (HIF-1 alpha) and vascular endothelial growth factor (VEGF). In parallel, a dissipation of gradients in the pericellular oxygen pressure was observed as measured by O(2)-sensitive microelectrodes. After 24--48 h of confrontation culture, cells positive for platelet endothelial cell adhesion molecule (PECAM-1) became visible in the contact region between the embryoid body and the tumor spheroid and sprouted within the confrontation cultures during subsequent days. Tumor-induced angiogenesis resulted in growth stimulation of tumor spheroids, disappearance of central necrosis and a reduction of the pericellular oxygen pressure. Furthermore, tumor vascularization resulted in elevated levels of HIF-1 alpha, VEGF, heat shock protein 27 (HSP27), and P-glycoprotein. Tumor-induced angiogenesis may augment the oxygen consumption in tumors resulting in an increased expression of hypoxia-related, proangiogenic genes as well as of HSP27 and P-glycoprotein, which are involved in a multidrug resistance phenotype.

Thalidomide inhibits angiogenesis in embryoid bodies by the generation of hydroxyl radicals

Thalidomide is a teratogen with anti-angiogenic properties and causes stunted limb growth (dysmelia) during human embryogenesis. The molecular mechanisms of thalidomide action in embryopathy are currently unknown. Using the endothelial-specific antigen platelet endothelial cell adhesion molecule-1 and confocal laser scanning microscopy we have demonstrated that thalidomide exerts anti-angiogenic effects on the development of capillary structures in embryoid bodies differentiated from murine embryonic stem cells. Consequently, in thalidomide-treated embryoid bodies the diffusion properties of the tissue were deteriorated. Thalidomide raised reactive oxygen species (ROS), as revealed using 2'7'-dichlorodihydrofluorescein diacetate (H(2)DCF-DA) as an indicator. A comparable ROS generation was achieved with the thalidomide hydrolysis product phthaloyl glutamic acid (PGA), but not with phthalimide (PI), the major component of thalidomide. ROS formation by thalidomide was inhibited by the hydroxyl radical scavengers mannitol and 2-mercaptoethanol. After coadministration of either 2-mercaptoethanol or mannitol with thalidomide the anti-angiogenic effects of thalidomide were abolished and the diffusion properties of the tissue were restored to the control values. In summary, our data suggest that thalidomide exerts its anti-angiogenic properties via the generation of toxic hydroxyl radicals, which impair vasculogenesis and angiogenesis during embryoid body development.

Establishment of ionic channels and signalling cascades in the embryonic stem cell-derived primitive endoderm and cardiovascular system

The first organ system to be established in early embryogenesis is the cardiovascular system which develops upon interaction with hypoblastic cells of the primitive endoderm. Here we focus on recent work on embryoid bodies derived from pluripotent embryonic stem (ES) cells. Ca(2+) oscillations and Ca(2+) signalling pathways during the differentiation of primitive endodermal cell layers are reported. Furthermore, the development-dependent expression of ion channels and the buildup of signalling cascades involved in the modulation of voltage-dependent L-type Ca(2+) channels during early cardiomyogenesis and the formation of functional vascular structures in the process of vasculogenesis and angiogenesis are reviewed. We also report on the use of green fluorescent protein reporter gene expression under the control of cardiac-specific promoters, e.g. the human cardiac alpha-actin promoter, which enables the identification and in vivo characterization of cardiomyocytes at very early stages of cardiomyogenesis.

Redox-regulation of intrinsic prion expression in multicellular prostate tumor spheroids

The cellular function of the intrinsic prion protein (PrPc) remains largely unknown. In the present study PrPc expression was investigated in multicellular prostate tumor spheroids and was correlated to the intracellular redox state as evaluated using the fluorescent dye 2'7'-dichlorodihydrofluorescein diacetate (H2DCFDA). In small tumor spheroids (diameter 100 +/- 20 microm) reactive oxygen species (ROS) levels were increased as compared with large (diameter 250 +/- 50 microm) spheroids. ROS generation was mediated by the mitochondrial respiratory chain and a NADPH oxidaselike enzyme, because carbonylcyanide-m-chlorophenylhydrazone (CCCP), rotenone, and diphenylene iodonium chloride (DPI) significantly reduced ROS levels. The elevated ROS were correlated to an increased expression of PrPc, Cu/Zn superoxide dismutase (SOD-1), and catalase in small as compared with large spheroids. In large tumor spheroids, PrPc was predominantly expressed in the peripheral cell layers and colocalized with SOD-1 and catalase. Raising intracellular ROS in large tumor spheroids by hydrogen peroxide, menadione, buthionine sulfoximine (BSO), and incubation in glutamine-reduced medium increased PrPc expression. In small spheroids PrPc was downregulated after incubation with the radical scavengers dehydroascorbate (DHA) and vitamin E. Our data indicate that PrPc expression in tumor spheroids is related to the intracellular redox state and may participate in antioxidative defense.

A tissue-like culture system using microstructures: influence of extracellular matrix material on cell adhesion and aggregation

Special microenvironmental conditions are required to induce and/or maintain specific qualities of differentiated cells. An important parameter is the three-dimensional tissue architecture that cannot be reproduced in conventional monolayer systems. Advanced tissue culture systems will meet many of these demands, but may reach their limits, especially when gradients of specific substances over distinct tissue layers must be established for long-term culture. These limitations may be overcome by incorporating microstructures into tissue-like culture systems. The microstructured cell support presented consists of a flat array of 625 cubic microcontainers with porous bottoms, in which cells can be supplied with specific media from both sides of the tissue layer. Permanent cell lines and primary rat hepatocytes have been used to test the culture system. In order to define reproducible conditions for tissue formation and for cell adherence to the structure, several ECM (extracellular matrix) components were tested for coating of microstructured substrata. The described tissue culture system offers great flexibility in adapting the cell support to specific needs.

Hypotonic Ca2+ signaling and volume regulation in proliferating and quiescent cells from multicellular spheroids

Hypotonicity-induced Ca2+ signals and volume regulation were studied in proliferating and quiescent subpopulations of multicellular prostate cancer spheroids. Enzymatic dissociation of multicellular spheroids 100+/-19 microm in diameter, which are entirely proliferative, yielded a population of cells with a mean cell diameter of 17.5+/-1.4 microm. After dissociation of spheroids in a size class of 200+/-30, 300+/-60, and 400+/-65 microm in diameter, two subpopulations of cells with mean cell diameters corresponding to 12.9+/-1.9 microm and 16.7+/-2 microm were discriminated. The subpopulation of large cells was shown to be proliferative by positive Ki-67 antibody staining; the subpopulation of small cells was Ki-67 negative, indicating cell quiescence. In a spheroid size class of 100+/-19 microm, a distinct subpopulation of quiescent cells was absent. Superfusion by hypotonic solutions revealed that only the proliferating cell fraction showed a regulatory volume decrease (RVD) and a [Ca2+]i transient. Both effects were absent in the quiescent cell population. The [Ca2+]i transient persisted in low (10 nM) Ca2+ solution and in the presence of 4 mM extracellular Ni2+ but was abolished in the presence of the endoplasmic reticulum Ca2+-ATPase blocker 2,5-di-tert-butyl-hydrochinone (t-BHQ). The t-BHQ likewise inhibited RVD, indicating that Ca2+ release from intracellular stores was necessary for RVD. Moreover, [Ca2+]i and RVD were dependent on an intact microfilament cytoskeleton because after 30 min of preincubation with cytochalasin B the [Ca2+]i transient was significantly reduced and RVD was abolished. The absence of RVD and [Ca2+]i transient in quiescent cells may be due to differences in the amount and the cytosolic arrangement of F-actin observed in quiescent cells.

Cytotoxicity of alpha-particle-emitting astatine-211-labelled antibody in tumour spheroids: no effect of hyperthermia

The high linear energy transfer, alpha-particle-emitting radionuclide astatine-211 (211At) is of interest for certain therapeutic applications; however, because of the 55- to 70-microm path length of its alpha-particles, achieving homogeneous tracer distribution is critical. Hyperthermia may enhance the therapeutic efficacy of alpha-particle endoradiotherapy if it can improve tracer distribution. In this study, we have investigated whether hyperthermia increased the cytotoxicity of an 211At-labelled monoclonal antibody (MAb) in tumour spheroids with a radius (approximately 100 microm) greater than the range of 211At alpha-particles. Hyperthermia for 1 h at 42 degrees C was used because this treatment itself resulted in no regrowth delay. Radiolabelled chimeric MAb 81C6 reactive with the extracellular matrix antigen tenascin was added to spheroids grown from the D-247 MG human glioma cell line at activity concentrations ranging from 0.125 to 250 kBq ml(-1). A significant regrowth delay was observed at 125 and 250 kBq ml(-1) in both hyperthermia-treated and untreated spheroids. For groups receiving hyperthermia, no increase in cytotoxicity was seen compared with normothermic controls at any activity concentration. These results and those from autoradiographs indicate that hyperthermia at 42 degrees C for 1 h had no significant effect on the uptake or distribution of this antitenascin MAb in D-247 MG spheroids.

Calcium-dependence of hydrogen peroxide-induced c-fos expression and growth stimulation of multicellular prostate tumor spheroids

Hydrogen peroxide (H2O2) in nanomolar concentrations (20-100 nM) stimulated the growth of small (diameter 100 +/- 30 microm) multicellular prostate cancer spheroids and increased c-fos expression. H2O2 transiently raised [Ca2+]i by Ca2+ release from intracellular stores as the transient persisted in low (10 nM) Ca2+ solution but was abolished when intracellular Ca2+ stores were depleted by thapsigargin or chelation of [Ca2+]i with BAPTA. The H2O2-induced [Ca2+]i transient was furthermore inhibited by the P2-purinoreceptor antagonists suramin and basilen blue, indicating that H2O2 may act via purinergic receptor stimulation. Treatment of spheroids with either suramin, basilen blue or BAPTA inhibited the H2O2-induced growth stimulation and c-fos expression, indicating that the H2O2-mediated growth stimulation of multicellular spheroids is mediated via a Ca2+-dependent pathway.

Characteristics of multicellular spheroids formed by primary cultures of human thyroid tumor cells

Features of multicellular tumor spheroids (MCTS) differed depending on their types of cells. MCTS formed by 4000 human thyroid primary culture epithelial tumor cells displayed diameters between 0.31 and 0.33 mm within 2 days regardless of the stage of malignancy of the originating tumors. Their cellular composition reflected that of the originating tumor in regard to DNA content and the expression of cytokeratin, vimentin, as well as thyroglobulin. During the following 3 weeks, their sizes increased up to diameters of 0.42 mm when their cells had been derived from carcinomas, and MCTS originating from adenomas stopped growing within the next 2 days. After 8 days of incubation, proliferating cells were only found in carcinoma MCTS. The cells were randomly distributed over the total volume of the spheroids, which displayed irregular cell arrangements but not concentric cell layers and did not form necrotic centers.

DC electrical field-induced c-fos expression and growth stimulation in multicellular prostate cancer spheroids

The effects of electrical direct current (DC) field pulses on c-fos expression, growth kinetics and vitality patterns of multicellular tumour spheroids (MCSs) were studied. Monitoring the membrane potential of MCSs by di-8-ANNEPS staining and confocal microscopy during DC electrical field treatment revealed a hyperpolarization at the anode-facing side and a depolarization at the cathode-facing side. When a single 500 V m(-1) electrical field pulse with a duration of 60 s was applied to MCSs (150-350 microm in diameter) an enhancement of the growth kinetics within a period of 6 days post pulse was observed. Whereas the volume doubling time amounted to 4-5 days in control samples, it was reduced to 1-2 days in electropulsed MCSs. At day 6 post pulse the diameter of the necrotic core was significantly smaller than the control. The critical diameter for the first appearance of central necrosis amounted to 350 +/- 50 microm in the control and 450 +/- 50 microm in the electropulsed MCSs. Coincidentally, the proliferating rim was increased to 107 +/- 11 microm in electropulsed MCSs as compared with 60 +/- 6 microm in the control. The growth stimulation may be mediated by the proto-oncogene c-fos as its expression increased by a factor of 2.5 within 2 h post pulse. c-fos expression declined towards control values within 8 h post pulse.