Development of an ultrasensitive in vitro assay to monitor growth of primary cell cultures with reduced mitotic activity

PicoGreen assay for nucleic acid quantification - Applications, challenges, and solutions

Various analytical methods and reagents have been employed for nucleic acid analysis in cells, biological fluids, and formulations. Standard techniques like gel electrophoresis and qRT-PCR are widely used for qualitative and quantitative nucleic acid analysis. However, these methods can be time-consuming and labor-intensive, with limitations such as inapplicability to small RNA at low concentrations and high costs associated with qRT-PCR reagents and instruments. As an alternative, PicoGreen (PG) has emerged as a valuable method for the quantitative analysis of nucleic acids. PG, a fluorescent dye, enables the quantitation of double-stranded DNA (dsDNA) or double-stranded RNA, including miRNA mimic and siRNA, in solution. It is also applicable to DNA and RNA analysis within cells using techniques like FACS and fluorescence microscopy. Despite its advantages, PG's fluorescence intensity is affected by various experimental conditions, such as pH, salts, and chemical reagents. This review explores the recent applications of PG as a rapid, cost-effective, robust, and accurate assay tool for nucleic acid quantification. We also address the limitations of PG and discuss approaches to overcome these challenges, recognizing the expanding range of its applications.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Purpose

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from primary human fibroblasts that can be decellularized into acellular biomaterials. However, fibroblasts cultured on rigid culture plastic or biomaterial scaffolds can experience aberrant mechanical cues that perturb the biochemical, mechanical, and the efficiency of ECM production.

Methods

Here, we demonstrate a method for preparing decellularized ECM using primary human fibroblasts with tissue and disease-specific features with two case studies: (1) cardiac fibroblasts; (2) lung fibroblasts from healthy or diseased donors. Cells aggregate into engineered microtissues in low adhesion microwells that deposited ECM and can be decellularized. We systematically investigate microtissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis.

Results

Microtissues exhibited tissue-specific gene expression and proteomics profiling, with ECM complexity similar to native tissues. Healthy lung microtissues exhibited web-like fibrillar collagen compared to dense patches in healthy heart microtissues. Diseased lung exhibited more disrupted collagen architecture than healthy. Decellularized microtissues had tissue-specific mechanical stiffness that was physiologically relevant. Importantly, decellularized microtissues supported viability and proliferation of human cells.

Conclusions

We show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue and disease-specific ECM. This approach should be widely applicable for generating personalized matrix that recapitulate tissues and disease states, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00809-y.

Measuring cell proliferation in bioprinting research

Tissue-like constructs, intended for application in tissue engineering and regenerative medicine, can be produced by three-dimensional (3D) bioprinting of cells in hydrogels. It is essential that the viability and proliferation of the encapsulated cells can be reliably determined. Methods currently used to evaluate cell proliferation, such as quantification of DNA and measurement of metabolic activity, have been developed for application in 2D cultures and might not be suitable for bioinks. In this study, human fibroblasts were either cast or printed in gelatin methacryloyl (GelMA) or sodium alginate hydrogels and cell proliferation was assessed by AlamarBlue, PicoGreen and visual cell counts. Comparison of data extrapolated from standard curves generated from 2D cultures and 3D hydrogels showed potential inaccuracies. Moreover, there were pronounced discrepancies in cell numbers obtained from these assays; the different bioinks strongly influenced the outcomes. Overall, the results indicate that more than one method should be applied for better assessment of cell proliferation in bioinks.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from human fibroblasts, which can then be decellularized into an acellular biomaterial. However, fibroblasts initially seeded on rigid tissue culture plastic or biomaterial scaffolds experience aberrant mechanical cues that influence ECM deposition. Here, we show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue-specific ECM. We investigate: 1) cardiac fibroblasts, as well as 2) lung fibroblasts from healthy, idiopathic fibrosis and chronic obstructive pulmonary disease donors. We demonstrate optimized culture and decellularization conditions, then characterize gene expression and protein composition. We further characterize ECM microstructure and mechanical properties. We envision that this method could be utilized for biomanufacturing of patient and tissue-specific ECM for organoid drug screening as well as implantable scaffolds.

Impact

In this study, we demonstrate a method for preparing decellularized matrix using primary human fibroblasts with tissue and disease-specific features. We aggregate single cell dispersions into engineered tissues using low adhesion microwells and show culture conditions that promote ECM deposition. We demonstrate this approach for cardiac fibroblasts as well as lung fibroblasts (both normal and diseased). We systematically investigate tissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis. This approach should be widely applicable for generating personalized ECM with features of patient tissues and disease state, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

DNA Dyes-Highly Sensitive Reporters of Cell Quantification: Comparison with Other Cell Quantification Methods

Cell quantification is widely used both in basic and applied research. A typical example of its use is drug discovery research. Presently, plenty of methods for cell quantification are available. In this review, the basic techniques used for cell quantification, with a special emphasis on techniques based on fluorescent DNA dyes, are described. The main aim of this review is to guide readers through the possibilities of cell quantification with various methods and to show the strengths and weaknesses of these methods, especially with respect to their sensitivity, accuracy, and length. As these methods are frequently accompanied by an analysis of cell proliferation and cell viability, some of these approaches are also described.

Cannabidiol-Driven Alterations to Inflammatory Protein Landscape of Lipopolysaccharide-Activated Macrophages In Vitro May Be Mediated by Autophagy and Oxidative Stress

Background: The nonpsychotropic phytocannabinoid cannabidiol (CBD) presents itself as a potentially safe and effective anti-inflammatory treatment relative to clinical standards. In this present study, we compare the capacity of CBD to the corticosteroid dexamethasone (Dex) in altering the secreted protein landscape of activated macrophages and speculate upon the mechanism underpinning these alterations. Materials and Methods: Human THP-1 monocytes were differentiated into macrophages (THP-1 derived macrophages [tMACs]), activated with lipopolysaccharide (LPS), and then treated with 5, 10, 25, 50, or 100 μM CBD or 10 μM Dex for 24 h. Following treatment, cytotoxicity of CBD and protein expression levels from culture supernatants and from whole cell lysates were assessed for secreted and intracellular proteins, respectively. Results: High concentration (50 and 100 μM) CBD treatments exhibit a cytotoxic effect on LPS-activated tMACs following the 24-h treatment. Relative to the LPS-activated and untreated control (M[LPS]), both 25 μM CBD and 10 μM Dex reduced expression of pro-inflammatory markers-tumor necrosis factor alpha, interleukin 1 beta, and regulated on activation, normal T cell expressed and secreted (RANTES)-as well as the pleiotropic marker interleukin-6 (IL-6). A similar trend was observed for anti-inflammatory markers interleukin-10 and vascular endothelial growth factor (VEGF). Dex further reduced secreted levels of monocyte chemoattractant protein-1 in addition to suppressing IL-6 and VEGF beyond treatments with CBD. The anti-inflammatory capacity of 25 μM CBD was concurrent with reduction in levels of phosphorylated mammalian target of rapamycin Ser 2448, endothelial nitric oxide synthase, and induction of cyclooxygenase 2 relative to M(LPS). This could suggest that the observed effects on macrophage immune profile may be conferred through inhibition of mammalian target of rapamycin complex 1 and ensuing induction of autophagy. Conclusion: Cumulatively, these data demonstrate cytotoxicity of high concentration CBD treatment. The data reported herein largely agree with other literature demonstrating the anti-inflammatory effects of CBD. However, there is discrepancy within literature surrounding efficacious concentrations and effects of CBD on specific secreted proteins. These data expand upon previous work investigating the effects of CBD on inflammatory protein expression in macrophages, as well as provide insight into the mechanism by which these effects are conferred.

Counting Chromosomes in Individual Bacteria to Quantify Their Impacts on Persistence

Persisters are phenotypic variants within bacterial populations that tolerate antibiotic treatments considerably better than the majority of cells. A phenotypic quality that varies within bacterial populations is the chromosome number of individual cells. One, two, four, or more chromosomes per cell have been observed previously, and the impact of genome copy number can range from gene dosage effects to an inability to perform specific DNA repair functions, such as homologous recombination. We hypothesize that chromosome abundance is an underappreciated phenotypic variable that could impact persistence to antibiotics. Here, we describe methodologies to segregate bacterial populations based on chromosome number, assess the purity of those subpopulations, and suggest assays that could be used to quantify the impacts of genome abundance on persistence.

Quantification of fixed adherent cells using a strong enhancer of the fluorescence of DNA dyes

Cell quantification is widely used in basic or applied research. The current sensitive methods of cell quantification are exclusively based on the analysis of non-fixed cells and do not allow the simultaneous detection of various cellular components. A fast, sensitive and cheap method of the quantification of fixed adherent cells is described here. It is based on the incubation of DAPI- or Hoechst 33342-stained cells in a solution containing SDS. The presence of SDS results in the quick de-staining of DNA and simultaneously, in an up-to-1,000-fold increase of the fluorescence intensity of the used dyes. This increase can be attributed to the micelle formation of SDS. The method is sufficiently sensitive to reveal around 50–70 human diploid cells. It is compatible with immunocytochemical detections, the detection of DNA replication and cell cycle analysis by image cytometry. The procedure was successfully tested for the analysis of cytotoxicity. The method is suitable for the quantification of cells exhibiting low metabolic activity including senescent cells. The developed procedure provides high linearity and the signal is high for at least 20 days at room temperature. Only around 90 to 120 minutes is required for the procedure’s completion.

Nano-scale clustering of integrin-binding ligands regulates endothelial cell adhesion, migration, and endothelialization rate: novel materials for small diameter vascular graft applications

Blood contacting devices are commonly used in today's medical landscape.

Chemosensitivity and resistance testing in malignant effusions with focus on primary malignant mesothelioma and metastatic adenocarcinoma

Cell based chemosensitivity and resistance testing is an attractive approach that offers functional measurement of drug response ex vivo with the ultimate goal to guide the choice of chemotherapy for various cancers. Thus, it has a great potential to select patients for the optimal treatment option, thereby offering a tool for personalized cancer therapy. Despite several decades of intensive scientific efforts ex-vivo tests are still not incorporated in the standard of care. Limited access to fresh tumor tissue, unsatisfactory models and single readout as endpoint constitute major hindrance. Thus, establishing and validating clinically useful and reliable model systems still remains a major challenge. Here we present malignant effusions as valuable sources for ex-vivo chemosensitivity and resistance testing. Accumulation of a malignant effusion in the pleura, peritoneum or pericardium is often the first diagnostic material for both primary malignant mesothelioma and a broad spectrum of metastatic adenocarcinoma originating from lung-, breast-, ovary- and gastro-intestinal organs as well as lymphoma. In contrast to biopsies, in these effusions malignant cells are easily accessible and often abundant. Effusion derived cells can occur dissociated or forming three-dimensional papillary structures that authentically recapitulate the biology of the corresponding tumor tissue and offer models for ex vivo testing. In addition, effusions have the advantage of being available prior to or concurrent with the pathological review, thus constituting an excellent source of viable cells for simultaneous molecular profiling, biomarker analysis and for establishing primary cells for studying tumor biology and resistance mechanisms. For a reliable test, however, a careful validation is needed, taking into account the inherited heterogeneity of malignant tumors, but also the complex interplay between malignant and benign cells, which are always present in this setting.

Low dosed interferon alpha augments the anti-tumor potential of histone deacetylase inhibition on prostate cancer cell growth and invasion

We evaluated whether low-dosed interferon alpha (IFNa) may augment the anti-tumor potential of the histone deacetylase (HDAC)-inhibitor valproic acid (VPA) on prostate cancer cells in vitro and in vivo. PC-3, DU-145, or LNCaP prostate cancer cells were treated with VPA (1 mM), IFNa (200 U/ml), or with the VPA-IFNa combination. Tumor cell growth, cell cycle progression, and cell cycle regulating proteins were then investigated by the MTT assay, flow cytometry, and western blotting. Tumor cell adhesion to endothelium or to immobilized extracellular matrix proteins, as well as migratory properties of the cells, were evaluated. Integrin α and β adhesion molecules and alterations of cell signaling pathways were analyzed. Finally, effects of the drug treatment on prostate cancer growth in vivo were determined in the NOD/SCID mouse model. VPA reduced tumor cell adhesion, migration, and growth in vitro. A much stronger anti-cancer potential was evoked by the VPA-IFNa combination, although IFNa in itself did not block growth or adhesion. The same effect was seen when tumor growth was evaluated in vivo. Molecular analysis revealed distinct elevation of histone H3 acetylation caused by VPA which was further up-regulated by VPA-IFNa, whereas IFNa alone did not alter H3 acetylation. The combinatorial benefit became obvious in Akt phosphorylation, p21 and p27 and integrin α1, α3, and β1 expression. Application of low-dosed IFNa to a VPA based regimen profoundly boosts the anti-tumor properties of VPA. The combined use of VPA and low-dosed IFNa may therefore be an innovative option in treating advanced prostate cancer.

The XTT cell proliferation assay applied to cell layers embedded in three-dimensional matrix

Cell proliferation, a main target in cancer therapy, is influenced by the surrounding three-dimensional (3D) extracellular matrix (ECM). In vitro drug screening is, thus, optimally performed under conditions in which cells are grown (embedded or trapped) in dense 3D matrices, as these most closely mimic the adhesive and mechanical properties of natural ECM. Measuring cell proliferation under these conditions is, however, technically more challenging compared with two-dimensional (2D) culture and other "3D culture conditions," such as growth on top of a matrix (pseudo-3D) or in spongy scaffolds with large pore sizes. Consequently, such measurements are only slowly applied on a wider scale. To advance this, we report on the equal quality (dynamic range, background, linearity) of measuring the proliferation of cell layers embedded in dense 3D matrices (collagen, Matrigel) compared with cells in 2D culture using the easy (one-step) and in 2D well-validated, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT)-assay. The comparison stresses the differences in proliferation kinetics and drug sensitivity of matrix-embedded cells versus 2D culture. Using the specific cell-layer-embedded 3D matrix setup, quantitative measurements of cell proliferation and cell invasion are shown to be possible in similar assay conditions, and cytostatic, cytotoxic, and anti-invasive drug effects can thus be reliably determined and compared in physiologically relevant settings. This approach in the 3D matrix holds promise for improving early-stage, high-throughput drug screening, targeting either highly invasive or highly proliferative subpopulations of cancers or both.

SYBR Green I: fluorescence properties and interaction with DNA

In this study, we have investigated the fluorescence properties of SYBR Green I (SG) dye and its interaction with double-stranded DNA (dsDNA). SG/dsDNA complexes were studied using various spectroscopic techniques, including fluorescence resonance energy transfer and time-resolved fluorescence techniques. It is shown that SG quenching in the free state has an intrinsic intramolecular origin; thus, the observed >1,000-fold SG fluorescence enhancement in complex with DNA can be explained by a dampening of its intra-molecular motions. Analysis of the obtained SG/DNA binding isotherms in solutions of different ionic strength and of SG/DNA association in the presence of a DNA minor groove binder, Hoechst 33258, revealed multiple modes of interaction of SG inner groups with DNA. In addition to interaction within the DNA minor groove, both intercalation between base pairs and stabilization of the electrostatic SG/DNA complex contributed to increased SG affinity to double-stranded DNA. We show that both fluorescence and the excited state lifetime of SG dramatically increase in viscous solvents, demonstrating an approximate 200-fold enhancement in 100 % glycerol, compared to water, which also makes SG a prospective fluorescent viscosity probe. A proposed structural model of the SG/DNA complex is compared and discussed with results recently reported for the closely related PicoGreen chromophore.

Characterization of PicoGreen interaction with dsDNA and the origin of its fluorescence enhancement upon binding

PicoGreen is a fluorescent probe that binds dsDNA and forms a highly luminescent complex when compared to the free dye in solution. This unique probe is widely used in DNA quantitation assays but has limited application in biophysical analysis of DNA and DNA-protein systems due to limited knowledge pertaining to its physical properties and characteristics of DNA binding. Here we have investigated PicoGreen binding to DNA to reveal the origin and mode of PicoGreen/DNA interactions, in particular the role of electrostatic and nonelectrostatic interactions in formation of the complex, as well as demonstrating minor groove binding specificity. Analysis of the fluorescence properties of free PicoGreen, the diffusion properties of PG/DNA complexes, and the excited-state lifetime changes upon DNA binding and change in solvent polarity, as well as the viscosity, reveal that quenching of PicoGreen in the free state results from its intramolecular dynamic fluctuations. On binding to DNA, intercalation and electrostatic interactions immobilize the dye molecule, resulting in a >1000-fold enhancement in its fluorescence. Based on the results of this study, a model of PicoGreen/DNA complex formation is proposed.

Discrepancies between metabolic activity and DNA content as tool to assess cell proliferation in cancer research

Cell proliferation is a critical and frequently studied feature of molecular biology in cancer research. Therefore, various assays are available using different strategies to measure cell proliferation. Metabolic assays such as AlamarBlue, water-soluble tetrazolium salt and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, which were originally developed to determine cell toxicity, are used to assess cell numbers. Additionally, proliferative activity can be determined by quantification of DNA content using fluorophores such as CyQuant and PicoGreen. Referring to data published in high ranking cancer journals, these assays were applied in 945 publications over the past 14 years to examine the proliferative behaviour of diverse cell types. In these studies, however, mainly metabolic assays were used to quantify changes in cell growth yet these assays may not accurately reflect cellular proliferation rates due to a miscorrelation of metabolic activity and cell number. Testing this hypothesis, we compared the metabolic activity of different cell types, human cancer cells and primary cells, over a time period of 4 days using AlamarBlue and the fluorometric assays CyQuant and PicoGreen to determine their DNA content. Our results show certain discrepancies in terms of over-estimation of cell proliferation with respect to the metabolic assay in comparison to DNA binding fluorophores.

Structure-fluorescence contrast relationship in cyanine DNA intercalators: toward rational dye design

The fluorescence enhancement mechanisms of a series of DNA stains of the oxazole yellow (YO) family have been investigated in detail using steady-state and ultrafast time-resolved fluorescence spectroscopy. The strong increase in the fluorescence quantum yield of these dyes upon DNA binding is shown to originate from the inhibition of two distinct processes: 1) isomerisation through large-amplitude motion that non-radiatively deactivates the excited state within a few picoseconds and 2) formation of weakly emitting H-dimers. As the H-dimers are not totally non-fluorescent, their formation is less efficient than isomerisation as a fluorescent contrast mechanism. The propensity of the dyes to form H-dimers and thus to reduce their fluorescence contrast upon DNA binding is shown to depend on several of their structural parameters, such as their monomeric (YO) or homodimeric (YOYO) nature, their substitution and their electric charge. Moreover, these parameters also have a substantial influence on the affinity of the dyes for DNA and on the ensuing sensitivity for DNA detection. The results give new insight into the development and optimisation of fluorescent DNA probes with the highest contrast.

Valproic acid inhibits adhesion of vincristine- and cisplatin-resistant neuroblastoma tumour cells to endothelium

Drug resistance to chemotherapy is often associated with increased malignancy in neuroblastoma (NB). In pursuit of alternative treatments for chemoresistant tumour cells, we tested the response of multidrug-resistant SKNSH and of vincristine (VCR)-, doxorubicin (DOX)-, or cisplatin (CDDP)-resistant UKF-NB-2, UKF-NB-3 or UKF-NB-6 NB tumour cell lines to valproic acid (VPA), a differentiation inducer currently in clinical trials. Drug resistance caused elevated NB adhesion (UKF-NB-2(VCR), UKF-NB-2(DOX), UKF-NB-2(CDDP), UKF-NB-3(VCR), UKF-NB-3(CDDP), UKF-NB-6(VCR), UKF-NB-6(CDDP)) to an endothelial cell monolayer, accompanied by downregulation of the adhesion receptor neural cell adhesion molecule (NCAM). Based on the UKF-NB-3 model, N-myc proteins were enhanced in UKF-NB-3(VCR) and UKF-NB-3(CDDP), compared to the drug naïve controls. p73 was diminished, whereas the p73 isoform deltaNp73 was upregulated in UKF-NB-3(VCR) and UKF-NB-3(CDDP). Valproic acid blocked adhesion of UKF-NB-3(VCR) and UKF-NB-3(CDDP), but not of UKF-NB-3(DOX), and induced the upregulation of NCAM surface expression, NCAM protein content and NCAM coding mRNA. Valproic acid diminished N-myc and enhanced p73 protein level, coupled with downregulation of deltaNp73 in UKF-NB-3(VCR) and UKF-NB-3(CDDP). Valproic acid also reverted enhanced adhesion properties of drug-resistant UKF-NB-2, UKF-NB-6 and SKNSH cells, and therefore may provide an alternative approach to the treatment of drug-resistant NB by blocking invasive processes.

Chemoresistance induces enhanced adhesion and transendothelial penetration of neuroblastoma cells by down-regulating NCAM surface expression

Background

Drug resistance to chemotherapy is often associated with increased malignancy in neuroblastoma (NB). One explanation for the link between resistance and malignancy might be that resistance facilitates cancer progression and invasion. To investigate this hypothesis, adhesion, transendothelial penetration and NCAM (CD56) adhesion receptor expression of drug-resistant versus drug-sensitive NB tumor cells were evaluated.

Methods

Acquired drug resistance was mimicked by exposing parental UKF-NB-2, UKF-NB-3 or IMR-32 tumor cells to increasing concentrations of vincristine- (VCR) or doxorubicin (DOX) to establish the resistant tumor cell sublines UKF-NB-2^VCR, UKF-NB-2^DOX, UKF-NB-3^VCR, UKF-NB-3^DOX, IMR-32^VCR and IMR-32^DOX. Additionally, the malignant behaviour of UKF-NB-4, which already possessed the intrinsic multidrug resistance (MDR) phenotype, was analyzed. UKF-NB-4 exposed to VCR or DOX were designated UKF-NB-4^VCR or UKF-NB-4^DOX. Combined phase contrast – reflection interference contrast microscopy was used to separately evaluate NB cell adhesion and penetration. NCAM was analyzed by flow cytometry, western blot and RT-PCR.

Results

VCR and DOX resistant tumor sublines showed enhanced adhesion and penetration capacity, compared to their drug naïve controls. Strongest effects were seen with UKF-NB-2^VCR, UKF-NB-3^VCR and IMR-32^DOX. DOX or VCR treatment also evoked increased invasive behaviour of UKF-NB-4. The process of accelerated tumor invasion was accompanied by decreased NCAM surface and protein expression, and down-regulation of NCAM coding mRNA. Transfection of UKF-NB-4^VCR cells with NCAM cDNA led to a significant receptor up-regulation, paralleled by diminished adhesion to an endothelial cell monolayer.

Conclusion

It is concluded that NB cells resistant to anticancer drugs acquire increased invasive capacity relative to non-resistant parental cells, and that enhanced invasion is caused by strong down-regulation of NCAM adhesion receptors.

Proliferation and osteogenic differentiation of mesenchymal stem cells cultured onto three different polymers in vitro

In this study, the osteoinductive and cell-binding properties of three different resorbable polymers were evaluated by human mesenchymal stem cells (MSCs). MSCs were isolated, expanded, and cultivated onto resorbable D,D,L,L-polylactide (PLLA), collagen I/III, and polygalactin-910/polydioxanone (PGPD) scaffolds in vitro. To evaluate the influence of dexamethasone, ascorbic acid, and beta-glycerolphosphate (DAG) on osteoblast differentiation, MSCs were incubated in a DAG-enriched medium. After a 28-day period in vitro, the cellular loaded polymers were digested enzymatically by papain and HCl. The Ca(2+) content of the biomembranes was evaluated by an o-kresolphthalein-complexon reaction via photometer. A PicoGreen assay was performed for dsDNA quantification. Significant differences between the number of adherent MSCs were documented (collagen > PLLA > PGPD). Compared to the initial number of adherent cells, all biomaterials induced a significant decrease in cellular adherence after 28 days in vitro. The presence of DAG-enriched culture medium stimulated the cellular proliferation for PLLA and slightly for PGPD, whereas cell proliferation was inhibited when MSCs were cultivated onto collagen I/III. In comparison with the control groups, all biomaterials (PLLA, PGPD, and collagen I/III) showed a significant increase in local Ca(2+) accumulation under DAG stimulation after 28 days in vitro. Furthermore, collagen I/III and PLLA scaffolds showed osteoinductive properties without DAG stimulation. These results were verified by immunocytochemical stainings against osteoblast-typical markers (osteopontin and alkaline phosphatase) and completed by calcified matrix detection (von Kossa staining). MSCs were identified by CD105 and CD13 antigen expression. Corresponding to an absence of CD34, CD45, and collagen II expression, we found no chondrogenic or hematopoietic cell differentiation. The results indicate significant differences for the proliferation, differentiation, adherence, and Ca(2+) accumulation between the tested polymers in a MSC culture.

Clinical relevance of serum angiogenic activity in patients with transitional cell carcinoma of the bladder

Angiogenesis is essential for tumor growth and progression and is mediated by positive and negative regulators of vessel growth. Since angiogenic mediators found in patient serum have been postulated to reflect the angiogenic potential of a malignant tumor, we investigated the angiogenic activity in the serum of patients with transitional cell carcinoma (TCC). The data were correlated to tumor characteristics and the clinical course of the patients. Eighty-one patients with transitional cell carcinoma and 53 control persons were included in the study. Preoperative serum samples were collected and both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were quantified by ELISA. Additionally, the serum evoked proliferative activity on human umbilical vein endothelial cells (HUVEC) was evaluated. Data were compared to the clinical course of the patients. Serum of tumor patients significantly enhanced the proliferative capacity of HUVEC, compared to cells grown in standard culture medium (p = 0.0032), but not when compared to serum from control persons. Serum from patients with superficial TCC and well differentiated tumors induced a significantly higher angiogenic response (ANG(hi)) than serum from patients with poorly differentiated and invasive carcinomas (ANG(lo); p = 0.037). VEGF level of ANG(hi) serum was 384.22 +/- 247.76 pg/ml (n = 37) which significantly differed from mean VEGF level detected in ANG(lo) serum (247.72 +/- 211.93 pg/ml, n = 42; p = 0.019). Similarly, mean bFGF levels were 9.58 +/- 5.91 pg/ml in ANG(hi) serum versus 5.74 +/- 3.52 pg/ml) in ANG(lo) serum (p = 0.0043). A negative correlation was established between VEGF/bFGF serum concentration and patient prognosis. The experiments demonstrate a positive correlation between VEGF and bFGF serum level and endothelial proliferation in vitro. The inverse relationship between angiogenic activity and tumor stage might disclose information about angiogenesis and tumor progression in TCC.

Endothelial adhesion of synchronized gastric tumor cells changes during cell cycle transit and correlates with the expression level of CD44 splice variants

AIM: To study adhesion capacity and CD44 expression of human gastric adenocarcinoma MKN45 cells at different stages of a first cell cycle.

METHODS: MKN45 cells were synchronized by aphidicolin and assayed for adhesion to an endothelial cell (HUVEC) monolayer. Surface expression of CD44 and CD44 splice variants on MKN45 cells was evaluated by flow cytometry. Functional relevance of CD44 adhesion receptors was investigated by blocking studies using anti CD44 monoclonal antibodies or by hyaluronan digestion.

RESULTS: Adhesion of MKN45 to HUVEC was increased during G2/M transit, after which adhesion returned to baseline levels with cell cycle completion. In parallel, CD44 splice variants CD44v4, CD44v5, and CD44v7 were all up-regulated on MKN45 during cell cycle progression with a maximum effect in G2/M. The function of CD44 surface receptors was assessed with specific receptor blocking monoclonal antibodies or removal of hyaluronan by digestion with hyaluronidase. Both strategies inhibited tumor cell adhesion to HUVEC by nearly 50%, which indicates that MKN45-HUVEC-interaction is CD44 dependent.

CONCLUSION: CD44 expression level is linked to the cell cycle in gastrointestinal tumor cells, which in turn leads to cell cycle dependent alterations of their adhesion behaviour to endothelium.

Human cytomegalovirus infection of tumor cells downregulates NCAM (CD56): a novel mechanism for virus-induced tumor invasiveness

Pathologic data indicate that human cytomegalovirus (HCMV) infection might be associated with the pathogenesis of several human malignancies. However, no definitive evidence of a causal link between HCMV infection and cancer dissemination has been established to date. This study describes the modulation of the invasive behavior of NCAM-expressing tumor cell lines by HCMV. Neuroblastoma (NB) cells, persistently infected with the HCMV strain AD169 (UKF-NB-4AD169 and MHH-NB-11AD169), were added to endothelial cell monolayers and adhesion and penetration kinetics were measured. The 140- and 180-kDa isoforms of the adhesion receptor NCAM were evaluated by flow cytometry, Western blot, and reverse transcription-polymerase chain reaction (RT-PCR). The relevance of NCAM for tumor cell binding was proven by treating NB with NCAM antisense oligonucleotides or NCAM transfection. HCMV infection profoundly increased the number of adherent and penetrated NB, compared to controls. Surface expression of NCAM was significantly lower on UKF-NB-4AD169 and MHH-NB-11AD169, compared to mock-infected cells. Western-blot and RT-PCR demonstrated reduced protein and RNA levels of the 140- and 180-kDa isoform. An inverse correlation between NCAM expression and adhesion capacity of NB has been shown by antisense and transfection experiments. We conclude that HCMV infection leads to downregulation of NCAM receptors, which is associated with enhanced tumor cell invasiveness.

Preservation of the synthetic and metabolic capacity of isolated human hepatocytes by coculture with human biliary epithelial cells

Bioartificial liver support systems have demonstrated limited efficacy in compensation of liver detoxification and substitution of liver-derived factors. However, in these devices, the biological substitution of the complex liver function has been restricted to xenogeneic or transformed hepatocytes. Therefore, we have examined the long-term effect of coculturing normal human hepatocytes (HCs) with allogeneic biliary epithelial cells (BECs). We applied functional in vitro assays to examine their metabolic potential by ammonia detoxification to urea, cytochrome P450-dependent lignocaine conversion to mono-ethyl-glycine-xylidide (MEGX), and protein expression and secretion. As the liver has a pivotal role in the synthesis of coagulation factors, we measured antithrombin III (AT III), factor VII, and albumin, comparing HCs plated on collagen or inside 3-dimensional collagen gels. Over 30 days, expression and secretion of albumin and clotting factors by human HCs were augmented by culture inside collagen gel, but were also enhanced and better maintained by coculture with BECs. Higher proportions of BECs cocultured with HCs substantially increased the protein synthesis and urea production. Remarkably, the almost absent cytochrome P450 activity of HC alone after 1 week could be reversed and maintained over 3 weeks by coculture with BECs. The pattern of these effects differed from the extent of interleukin-6 (IL-6) production and HC viability under the compared conditions. In conclusion, coculture of human HCs with BECs impressively restores the synthetic and metabolic liver function in vitro. These results suggest mechanisms of improved liver epithelial differentiation supported by coculture conditions. This technique offers new perspectives in bioartificial liver support, hepatocyte transplantation, and stem cell differentiation.

The immunosuppressive drug mycophenolate mofetil impairs the adhesion capacity of gastrointestinal tumour cells

Immunosuppression correlates with the development and recurrence of cancer. Mycophenolate mofetil (MMF) has been shown to reduce adhesion molecule expression and leucocyte recruitment into the donor organ. We have hypothesized that MMF might also prevent receptor-dependent tumour dissemination. Therefore, we have investigated the effects of MMF on tumour cell adhesion to human umbilical vein endothelial cells (HUVEC) and compared them with the effects on T cell-endothelial cell interactions. Influence of MMF on cellular adhesion to HUVEC was analysed using isolated CD4+ and CD8+ T cells, or WiDr colon adenocarcinoma cells as the model tumour. HUVEC receptors ICAM-1, VCAM-1, E-selectin and P-selectin were detected by flow cytometry, Western blot or Northern blot analysis. Binding activity of T cells or WiDr cells in the presence of MMF were measured using immobilized receptor globulin chimeras. MMF potently blocked both T cell and WiDr cell binding to endothelium by 80%. Surface expression of the endothelial cell receptors was reduced by MMF in a dose-dependent manner. E-selectin mRNA was concurrently reduced with a maximum effect at 1 microm. Interestingly, MMF acted differently on T cells and WiDr cells. Maximum efficacy of MMF was reached at 10 and 1 microm, respectively. Furthermore, MMF specifically suppressed T cell attachment to ICAM-1, VCAM-1 and P-selectin. In contrast, MMF prevented WiDr cell attachment to E-selectin. In conclusion, our data reveal distinct effects of MMF on both T cell adhesion and tumour cell adhesion to endothelial cells. This suggests that MMF not only interferes with the invasion of alloactivated T cells, but might also be of value in managing post-transplantation malignancy.

Binding of gastrointestinal tumor cells to endothelial E- and P-selectin adhesion receptors leads to transient down-regulation of sLeX ligands in vitro

BACKGROUND AND AIMS

The prognostic relevance of sialyl Lewis X (sLeX) expression in colorectal and gastric cancer and its relevance to the hematogenous phase of tumor invasion is controversial. This study was designed to evaluate sLeX expression during tumor cell-endothelial cell interaction in vitro.

METHODS

Adhesion and transendothelial penetration of MKN45, PaCa-2, WiDr, or Dan-G cells was analyzed by combined phase contrast-reflection interference contrast microscopy. In parallel, kinetics of membranous sLeX expression were examined fluorimetrically. To identify factor(s) which may be responsible for sLeX expression during tumor invasion tumor cells were treated with soluble immunomodulators, isolated endothelial plasma membranes, or E-selectin or P-selectin IgG fusion proteins. sLeX was then analyzed by flow cytometry.

RESULTS

Fluorometric quantification of sLeX demonstrated an inverse correlation between basal sLeX expression level and adhesion capacity of the tumor cells. Unexpectedly, sLeX was strongly down-regulated on tumor cell membranes in the course of heterophilic cell-cell contacts. The process occurred transiently, with a maximum effect 30-60 min after introducing tumor cells to the endothelial monolayer. Binding of tumor cells to immobilized E- and P-selectin IgG globulin chimeras was shown to be responsible for this phenomenon.

CONCLUSION

A transient loss of sLeX is necessary for gastrointestinal tumor cells to invade endothelial cells. Due to the transient nature of the decrease in sLeX the controversy about the prognostic relevance of sLeX expression in colorectal and gastric cancer may be rooted in the stage of tumor invasion at the time of sLeX measurement.

Comparison of antiproliferative effects of experimental and established antipsoriatic drugs on human keratinocytes, using a simple 96-well-plate assay

Pharmacological treatments for psoriasis are generally based on antiproliferative, anti-inflammatory, or differentiation-modifying activity, or a combination of two or more of these actions. Potentially new drugs for treatment of psoriasis, which act on proliferation, can be identified by screening large compound libraries in a cell proliferation model that allows for characterization of drug effects on in vitro growth of normal human keratinocytes. High-throughput programs based on biological testing of diverse collections of compounds can rapidly identify leads for potential drug candidates in the treatment of psoriasis. In this study, we describe nonradioactive measurement of keratinocyte proliferation in the exponential growth phase in a 96-well format, using a sensitive deoxyribonucleic acid-binding dye to analyze drugs that are pharmacologically active in growth inhibition. Release of lactate dehydrogenase was used to exclude cytotoxic effects. We examined a number of compounds in a test range of 10(-7) to 10(-5) M, including known antipsoriatic drugs, and experimental drugs that are potentially useful in the treatment of psoriasis. We found strong concentration-dependent growth inhibition by dithranol, an antipsoriatic compound that is presumed to target the epidermal compartment. Methotrexate, cyclosporin A, and all-trans retinoic acid did not significantly affect proliferation at therapeutically relevant concentrations. The p38 mitogen-activated protein kinase inhibitor, SB220025, and curcumin, a natural phytochemical, inhibited keratinocyte proliferation at 10(-5) M. We conclude that this assay, in combination with the previously developed assays for psoriatic differentiation, provides a useful tool for identification of antipsoriatic drugs.

Structurally normal corneas in aldehyde dehydrogenase 3a1-deficient mice

We have constructed an ALDH3a1 null mouse to investigate the role of this enzyme that comprises nearly one-half of the total water-soluble protein in the mouse corneal epithelium. ALDH3a1-deficient mice are viable and fertile, have a corneal epithelium with a water-soluble protein content approximately half that of wild-type mice, and contain no ALDH3a1 as determined by zymograms and immunoblots. Despite the loss of protein content and ALDH3a1 activity, the ALDH3a1(-/-) mouse corneas appear indistinguishable from wild-type corneas when examined by histological analysis and electron microscopy and are transparent as determined by light and slit lamp microscopy. There is no evidence for a compensating protein or enzyme. Even though the function of ALDH3a1 in the mouse cornea remains unknown, our data indicate that its enzymatic activity is unnecessary for corneal clarity and maintenance, at least under laboratory conditions.

Sensitive determination of cell number using the CyQUANT cell proliferation assay

We describe here the development and characterization of the CyQUANT cell proliferation assay, a highly sensitive, fluorescence-based microplate assay for determining numbers of cultured cells. The assay employs CyQUANT GR dye, which produces a large fluorescence enhancement upon binding to cellular nucleic acids that can be measured using standard fluorescein excitation and emission wavelengths. The fluorescence emission of the dye-nucleic acid complexes correlated linearly with cell number over a large range using a wide variety of cell types. Under the recommended assay conditions, standard curves were linear (r(2)>0.995), detecting as few as 10-50 cells and as many as 25,000-50,000 cells with a single dye concentration, depending on cell type. Increasing the dye concentration extended the linear range of the assay to 100,000-250,000 cells. Results of cell proliferation and growth inhibition studies with the assay were similar to those obtained in published studies using other standard assays. CyQUANT assay measurements of serum-stimulated cell proliferation correlated well with measurements made using [3H]-thymidine. Also, the assay was used to analyze cellular DNA or RNA content, with the addition of a nuclease digestion step to the protocol. The assay procedure is simple and convenient, with no wash steps, and is readily amenable to automation.

RT-PCR from eosinophil-depleted leukocytes without RNA extraction: cell selection using streptavidin PCR tubes

OBJECTIVES

The major RNase activity of leukocytes has been attributed to eosinophil-derived neurotoxin EDN. Depletion of eosinophils enables RT-PCR from 10(5) leukocytes without RNA extraction. In this study we introduced streptavidin-coated PCR tube strips for the selection of eosinophil-free leukocytes for RT-PCR analysis.

DESIGN AND METHODS

Polypropylene 0.2 ml PCR tube strips were coated with streptavidin and biotinylated antibodies against cell surface antigens were attached to the tubes. CD7-positive T-lymphocytes, CD19-positive B-lymphocytes and CD16-positive cells (mainly neutrophils and monocytes) were positively selected by incubating of 1-2 x 10(5) leukocytes in the antibody-coated PCR tubes for 30 min at 23 degrees C.

RESULTS

The mean amount of cells bound into a tube was 31,500 (CV25%) T-cells and 8,600 (CV61%) B-cells from 12 blood samples, and 23,600 (CV22%) CD16+ cells from 17 samples. The influence of selected cell lysate on the RT-PCR analysis of Philadelphia chromosome (bcr/abl translocation) from 100 K562 cells was small: 78% (CV28%) of the leukocyte-free signal was obtained in the presence of CD16+ cells or 89% (CV15%) and 99% (CV11%) and in the presence of T-cells and B-cells, respectively.

CONCLUSIONS

These results suggest that through the introduction of eosinophil-free cell population into RT-PCR a reproducible method with reasonable leukocyte yield and avoiding RNA extraction was developed.

Dedifferentiation of human hepatocytes by extracellular matrix proteins in vitro: quantitative and qualitative investigation of cytokeratin 7, 8, 18, 19 and vimentin filaments

BACKGROUND/AIMS

Liver cirrhosis and carcinogenesis are accompanied by an alteration in extracellular matrix material. Histological studies reveal upregulation of the intermediate filaments cytokeratins 8 and 18 and de novo synthesis of vimentin, and cytokeratin 7 or 19 in hepatocytes. The aim of this study was to investigate how these two processes are linked.

METHODS

Human hepatocytes were seeded: (i) on the matrix components collagen I, IV, laminin, or fibronectin; (ii) on stoichiometrically different complete matrices, derived from human placenta (matrix I) or the Englebreth-Holm-Swarm tumor (matrix II), and (iii) inside a three-dimensional collagen I sandwich. Filament expression and assembly were measured by cytofluor analysis or confocal laserscan microscopy.

RESULTS

The matrix components or complete matrices triggered enhancement of cytokeratins 8 and 18 and de novo synthesis of cytokeratins 7, 19 and vimentin in a characteristic way. Confocal images demonstrated a dense and uniform network of cytokeratin 18 in freshly isolated cells, which was "replaced" by a few, thick protein bundles within 20 days. Interestingly, newly synthesized cytokeratin 19 structurally resembled the cytokeratin 19 organization in biliary epithelial cells. Marked cytokeratin alterations could be partially prevented when hepatocytes were grown in a three-dimensional collagen sandwich.

CONCLUSIONS

Pathological alterations to the chemical composition, molecular structure, or spatial arrangement of the liver matrix lead to specific changes in the intermediate filament pattern in human hepatocytes. We assume that degradation of the matrix results in pathological alterations to the hepatocyte-receptor matrix-ligand ratio, followed by a switch from physiological to pathological cell-activation.