Sensitive determination of cell number using the CyQUANT cell proliferation assay

Structure-activity relationships among DNA ligase inhibitors: Characterization of a selective uncompetitive DNA ligase I inhibitor

In human cells, there are three genes that encode DNA ligase polypeptides with distinct but overlapping functions. Previously small molecule inhibitors of human DNA ligases were identified using a structure-based approach. Three of these inhibitors, L82, a DNA ligase I (LigI)-selective inhibitor, and L67, an inhibitor of LigI and DNA ligases III (LigIII), and L189, an inhibitor of all three human DNA ligases, have related structures that are composed of two 6-member aromatic rings separated by different linkers. Here we have performed a structure-activity analysis to identify determinants of activity and selectivity. The majority of the LigI-selective inhibitors had a pyridazine ring whereas the LigI/III- and LigIII-selective inhibitors did not. In addition, the aromatic rings in LigI-selective inhibitors had either arylhydrazone or acylhydrazone, but not vinyl linkers. Among the LigI-selective inhibitors, L82-G17 exhibited increased activity against and selectivity for LigI compared with L82. Notably. L82-G17 is an uncompetitive inhibitor of the third step of the ligation reaction, phosphodiester bond formation. Cells expressing LigI were more sensitive to L82-G17 than isogenic LIG1 null cells. Furthermore, cells lacking nuclear LigIIIα, which can substitute for LigI in DNA replication, were also more sensitive to L82-G17 than isogenic parental cells. Together, our results demonstrate that L82-G17 is a LigI-selective inhibitor with utility as a probe of the catalytic activity and cellular functions of LigI and provide a framework for the future design of DNA ligase inhibitors.

Dysregulation of autism-associated synaptic proteins by psychoactive pharmaceuticals at environmental concentrations

Autism Spectrum Disorders (ASD) are complex neurological disorders for which the prevalence in the U.S. is currently estimated to be 1 in 50 children. A majority of cases of idiopathic autism in children likely result from unknown environmental triggers in genetically susceptible individuals. These triggers may include maternal exposure of a developing embryo to environmentally relevant minute concentrations of psychoactive pharmaceuticals through ineffectively purified drinking water. Previous studies in our lab examined the extent to which gene sets associated with neuronal development were up- and down-regulated (enriched) in the brains of fathead minnows treated with psychoactive pharmaceuticals at environmental concentrations. The aim of this study was to determine whether similar treatments would alter in vitro expression of ASD-associated synaptic proteins on differentiated human neuronal cells. Human SK-N-SH neuroblastoma cells were differentiated for two weeks with 10μM retinoic acid (RA) and treated with environmentally relevant concentrations of fluoxetine, carbamazepine or venlafaxine, and flow cytometry technique was used to analyze expression of ASD-associated synaptic proteins. Data showed that carbamazepine individually, venlafaxine individually and mixture treatment at environmental concentrations significantly altered the expression of key synaptic proteins (NMDAR1, PSD95, SV2A, HTR1B, HTR2C and OXTR). Data indicated that psychoactive pharmaceuticals at extremely low concentrations altered the in vitro expression of key synaptic proteins that may potentially contribute to neurological disorders like ASD by disrupting neuronal development.

Mechanotransduction Effects on Endothelial Cell Proliferation via CD31 and VEGFR2: Implications for Immunomagnetic Separation

Immunomagnetic separation is used to isolate circulating endothelial cells (ECs) and endothelial progenitor cells (EPCs) for diagnostics and tissue engineering. However, potentially detrimental changes in cell properties have been observed post-separation. Here, the effect of mechanical force, which is naturally applied during immunomagnetic separation, on proliferation of human umbilical vein endothelial cells (HUVEC), kinase insert domain-positive receptor (KDR) cells, and peripheral blood mononuclear cells (PBMCs). Cells are exposed to CD31 or Vascular Endothelial Growth Factor Receptor-2 (VEGFR2) targeted MACSi beads at varying bead to cell ratios and compared to free antibody and unconjugated beads. A vertical magnetic gradient is applied to static 2D cultures, and a magnetic cell sorter is used to analyze cells in dynamic flow. No significant difference in EC proliferation is observed for controls or VEGFR2-targeting beads, whereas CD31-conjugated beads increase proliferation in a dose dependent manner in static 2-D cultures. This effect occurs in the absence of magnetic field, but is more pronounced with magnetic force. After flow sorting, similar increases in proliferation are seen for CD31 targeting beads. Thus, the effects of targeting antibody and magnetic force applied should be considered when designing immunomagnetic separation protocols for ECs.

Logistic Proliferation of Cells in Scratch Assays is Delayed

Scratch assays are used to study how a population of cells re-colonises a vacant region on a two-dimensional substrate after a cell monolayer is scratched. These experiments are used in many applications including drug design for the treatment of cancer and chronic wounds. To provide insights into the mechanisms that drive scratch assays, solutions of continuum reaction-diffusion models have been calibrated to data from scratch assays. These models typically include a logistic source term to describe carrying capacity-limited proliferation; however, the choice of using a logistic source term is often made without examining whether it is valid. Here we study the proliferation of PC-3 prostate cancer cells in a scratch assay. All experimental results for the scratch assay are compared with equivalent results from a proliferation assay where the cell monolayer is not scratched. Visual inspection of the time evolution of the cell density away from the location of the scratch reveals a series of sigmoid curves that could be naively calibrated to the solution of the logistic growth model. However, careful analysis of the per capita growth rate as a function of density reveals several key differences between the proliferation of cells in scratch and proliferation assays. Our findings suggest that the logistic growth model is valid for the entire duration of the proliferation assay. On the other hand, guided by data, we suggest that there are two phases of proliferation in a scratch assay; at short time, we have a disturbance phase where proliferation is not logistic, and this is followed by a growth phase where proliferation appears to be logistic. These two phases are observed across a large number of experiments performed at different initial cell densities. Overall our study shows that simply calibrating the solution of a continuum model to a scratch assay might produce misleading parameter estimates, and this issue can be resolved by making a distinction between the disturbance and growth phases. Repeating our procedure for other scratch assays will provide insight into the roles of the disturbance and growth phases for different cell lines and scratch assays performed on different substrates.

In situ morphological assessment of apoptosis induced by Phaleria macrocarpa (Boerl.) fruit ethyl acetate fraction (PMEAF) in MDA-MB-231 cells by microscopy observation

Phaleria macrocarpa (Boerl.) is a well-known medicinal plant and have been extensively used as traditional medicine for ages in treatment of various diseases. The purpose of this study was to determine the in situ cytotoxicity effect P. macrocarpa fruit ethyl acetate fraction (PMEAF) by using various conventional and modern microscopy techniques. The cytotoxicity of PMEAF treated MDA-MB-231 cells was determined through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay and CyQuant Cell Proliferation Assay after 24h of treatment. Both results were indicated that the PMEAF is a potential anticancer agent with the average IC₅₀ values of 18.10μg/mL by inhibiting the MDA-MB-231 cell proliferation. Various conventional and modern microscopy techniques such as light microscopy, holographic microscopy, transmission (TEM) and scanning (SEM) electron microscope were used for the observation of morphological changes in PMEAF treated MDA-MB-231cells for 24h. The characteristic of apoptotic cell death includes cell shrinkage, membrane blebs, chromatin condensation and the formation of apoptotic bodies were observed. PMEAF might be the best candidate for developing more potent anticancer drugs or chemo-preventive supplements.

Human Papillomavirus Downregulates the Expression of IFITM1 and RIPK3 to Escape from IFNγ- and TNFα-Mediated Antiproliferative Effects and Necroptosis

The clearance of a high-risk human papillomavirus (hrHPV) infection takes time and requires the local presence of a strong type 1 cytokine T cell response, suggesting that hrHPV has evolved mechanisms to resist this immune attack. Using an unique system for non, newly, and persistent hrHPV infection, we show that hrHPV infection renders keratinocytes (KCs) resistant to the antiproliferative- and necroptosis-inducing effects of IFNγ and TNFα. HrHPV-impaired necroptosis was associated with the upregulation of several methyltransferases, including EZH2, and the downregulation of RIPK3 expression. Restoration of RIPK3 expression using the global histone methyltransferase inhibitor 3-deazaneplanocin increased necroptosis in hrHPV-positive KCs. Simultaneously, hrHPV effectively inhibited IFNγ/TNFα-mediated arrest of cell growth at the S-phase by downregulating IFITM1 already at 48 h after hrHPV infection, followed by an impaired increase in the expression of the antiproliferative gene RARRES1 and a decrease of the proliferative gene PCNA. Knockdown of IFITM1 in uninfected KCs confirmed its role on RARRES1 and its antiproliferative effects. Thus, our study reveals how hrHPV deregulates two pathways involved in cell death and growth regulation to withstand immune-mediated control of hrHPV-infected cells.

Argon Induces Protective Effects in Cardiomyocytes during the Second Window of Preconditioning

Increasing evidence indicates that argon has organoprotective properties. So far, the underlying mechanisms remain poorly understood. Therefore, we investigated the effect of argon preconditioning in cardiomyocytes within the first and second window of preconditioning. Primary isolated cardiomyocytes from neonatal rats were subjected to 50% argon for 1 h, and subsequently exposed to a sublethal dosage of hypoxia (<1% O₂) for 5 h either within the first (0–3 h) or second window (24–48 h) of preconditioning. Subsequently, the cell viability and proliferation was measured. The argon-induced effects were assessed by evaluation of mRNA and protein expression after preconditioning. Argon preconditioning did not show any cardioprotective effects in the early window of preconditioning, whereas it leads to a significant increase of cell viability 24 h after preconditioning compared to untreated cells (p = 0.015) independent of proliferation. Argon-preconditioning significantly increased the mRNA expression of heat shock protein (HSP) B1 (HSP27) (p = 0.048), superoxide dismutase 2 (SOD2) (p = 0.001), vascular endothelial growth factor (VEGF) (p < 0.001) and inducible nitric oxide synthase (iNOS) (p = 0.001). No difference was found with respect to activation of pro-survival kinases in the early and late window of preconditioning. The findings provide the first evidence of argon-induced effects on the survival of cardiomyocytes during the second window of preconditioning, which may be mediated through the induction of HSP27, SOD2, VEGF and iNOS.

Psychoactive pharmaceuticals at environmental concentrations induce in vitro gene expression associated with neurological disorders

Background

A number of researchers have speculated that neurological disorders are mostly due to the interaction of common susceptibility genes with environmental, epigenetic and stochastic factors. Genetic factors such as mutations, insertions, deletions and copy number variations (CNVs) are responsible for only a small subset of cases, suggesting unknown environmental contaminants play a role in triggering neurological disorders like idiopathic autism. Psychoactive pharmaceuticals have been considered as potential environmental contaminants as they are detected in the drinking water at very low concentrations. Preliminary studies in our laboratory identified gene sets associated with neuronal systems and human neurological disorders that were significantly enriched after treating fish brains with psychoactive pharmaceuticals at environmental concentrations. These gene expression inductions were associated with changes in fish behavior. Here, we tested the hypothesis that similar treatments would alter in vitro gene expression associated with neurological disorders (including autism) in human neuronal cells. We differentiated and treated human SK-N-SH neuroblastoma cells with a mixture (fluoxetine, carbamazepine and venlafaxine) and valproate (used as a positive control to induce autism-associated profiles), followed by transcriptome analysis with RNA-Seq approach.

Results

We found that psychoactive pharmaceuticals and valproate significantly altered neuronal gene sets associated with human neurological disorders (including autism-associated sets). Moreover, we observed that altered expression profiles in human cells were similar to gene expression profiles previously identified in fish brains.

Conclusions

Psychoactive pharmaceuticals at environmental concentrations altered in vitro gene expression profiles of neuronal growth, development and regulation. These expression patterns were associated with potential neurological disorders including autism, suggested psychoactive pharmaceuticals at environmental concentrations might mimic, aggravate, or induce neurological disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2784-1) contains supplementary material, which is available to authorized users.

Influence of Clinically Relevant Mechanical Forces on Vascular Smooth Muscle Cells Under Chronic High Glucose: An In Vitro Dynamic Disease Model

BACKGROUND

In this study, we subjected vascular smooth muscle cells (VSMC) to acute and chronic high glucose conditions under physiologically relevant levels of cyclic strain and low wall shear forces to compare phenotypic modulation and thus conceptualize a dynamic-disease test model which captures cellular response more accurately in comparison with static cultures.

METHODS

P2-P6 rat aortic smooth muscle cells were seeded on type I collagen-coated silicone membranes and subjected to 0-7% cyclic strain at 1 Hz and 0.3 dynes/cm(2) shear stress from flow for 24 hr under acute (25 mM d-glucose, 84 hr) and chronic high glucose conditions (25 mM d-glucose, 3-4 weeks). Samples were analyzed for cell proliferation, percent apoptosis, cellular hypertrophy, and expression levels of smooth muscle contractile state-associated markers with 0.05 level of significance.

RESULTS

Concomitant application of cyclic strain and flow shear resulted in an overall increase in proliferation of VSMCs under both acute and chronic high glucose conditions as compared with normal glucose control (P < 0.0001). Application of both cyclic strain and cyclic strain shear resulted in a significant increase in percent apoptosis with chronic high glucose treatment in comparison with both normal glucose controls (P < 0.0001) and acute high glucose (P < 0.0001). Cellular hypertrophy as estimated by measuring cell area and aspect ratio revealed a significantly altered morphology due to concomitant loading under chronic high glucose conditions with significantly higher cell area (P < 0.0001) and lower aspect ratio (P < 0.0001) indicative of a relatively rounded morphology as compared with normal glucose controls. Western blot analysis demonstrated reduced expression of SM α-actin (P < 0.0001), calponin (P < 0.0001), and SM22α (P = 0.0008) for concomitant loading under chronic high glucose treatment as compared with normal glucose controls.

CONCLUSIONS

Concomitant application of cyclic strain and low wall shear stress resulted in greater phenotypic modulation of VSMCs due to chronic high glucose treatment as compared with normal glucose controls, thus implicating cellular-response differences which may impact progression of in-stent restenosis in diabetic patients with poorly controlled hyperglycemia. Similarity of VSMC response from our study to existing preclinical models of diabetes and reports of altered phenotype of VSMCs isolated from diabetic patients substantiate the relevance of our dynamic disease test model.

Theobroma cacao: Review of the Extraction, Isolation, and Bioassay of Its Potential Anti-cancer Compounds

Plants have been a good source of therapeutic agents for thousands of years; an impressive number of modern drugs used for treating human diseases are derived from natural sources. The Theobroma cacao tree, or cocoa, has recently garnered increasing attention and become the subject of research due to its antioxidant properties, which are related to potential anti-cancer effects. In the past few years, identifying and developing active compounds or extracts from the cocoa bean that might exert anti-cancer effects have become an important area of health- and biomedicine-related research. This review provides an updated overview of T. cacao in terms of its potential anti-cancer compounds and their extraction, in vitro bioassay, purification, and identification. This article also discusses the advantages and disadvantages of the techniques described and reviews the processes for future perspectives of analytical methods from the viewpoint of anti-cancer compound discovery.

Effects of a discoloration-resistant calcium aluminosilicate cement on the viability and proliferation of undifferentiated human dental pulp stem cells

Discoloration-resistant calcium aluminosilicate cement has been formulated to overcome the timely problem of tooth discoloration reported in the clinical application of bismuth oxide-containing hydraulic cements. The present study examined the effects of this experimental cement (Quick-Set2) on the viability and proliferation of human dental pulp stem cells (hDPSCs) by comparing the cellular responses with commercially available calcium silicate cement (white mineral trioxide aggregate; WMTA) after different aging periods. Cell viability and proliferation were examined using assays that examined plasma membrane integrity, leakage of cytosolic enzyme, caspase-3 activity for early apoptosis, oxidative stress, mitochondrial metabolic activity and intracellular DNA content. Results of the six assays indicated that both Quick-Set2 and WMTA were initially cytotoxic to hDPSCs after setting for 24 h, with Quick-Set2 being comparatively less cytotoxic than WMTA at this stage. After two aging cycles, the cytotoxicity profiles of the two hydraulic cements were not significantly different and were much less cytotoxic than the positive control (zinc oxide-eugenol cement). Based on these results, it is envisaged that any potential beneficial effect of the discoloration-resistant calcium aluminosilicate cement on osteogenesis by differentiated hDPSCs is more likely to be revealed after outward diffusion and removal of its cytotoxic components.

Interleukin-1β Affects MDAMB231 Breast Cancer Cell Migration under Hypoxia: Role of HIF-1α and NFκB Transcription Factors

Inflammation and tumor hypoxia are intimately linked and breast cancer provides a typical example of an inflammation-linked malignant disease. Indeed, breast cancer progression is actively supported by inflammatory components, including IL-1β, and by the hypoxia-inducible factor- (HIF-) 1α. In spite of many attempts where the role of either IL-1β or HIF-1α was evaluated, detailed mechanisms for their effects on breast cancer cell migration under hypoxia are still unclear. We here report that IL-1β increased MDAMB231 cell migration under hypoxic conditions along with HIF-1α accumulation and upregulation of CXCR1, which is transcriptionally regulated by HIF-1α, as well as an increased expression of CXCL8 and NFκB. In addition, IL-1β-induced cell migration in hypoxia was not affected when HIF-1α was inhibited by either siRNA or Topotecan, well known for its inhibitory effect on HIF-1α. Of interest, HIF-1α inhibition did not reduce NFκB and CXCL8 expression and the reduction of IL-1β-induced cell migration under hypoxia was achieved only by pharmacological inhibition of NFκB. Our findings indicate that inhibition of HIF-1α does not prevent the migratory program activated by IL-1β in hypoxic MDAMB231 cells. They also suggest a potential compensatory role of NFκB/CXCL8 pathway in IL-1β-induced MDAMB231 cell migration in a hypoxic microenvironment.

Different patterns of nuclear and mitochondrial penetration by the G3 PAMAM dendrimer and its biotin-pyridoxal bioconjugate BC-PAMAM in normal and cancer cells in vitro

The intracellular localization and colocalization of a fluorescently labeled G3 amine-terminated cationic polyamidoamine (PAMAM) dendrimer and its biotin-pyridoxal (BC-PAMAM) bioconjugate were investigated in a concentration-dependent manner in normal human fibroblast (BJ) and squamous epithelial carcinoma (SCC-15) cell lines. After 24 hours treatment, both cell lines revealed different patterns of intracellular dendrimer accumulation depending on their cytotoxic effects. Cancer cells exhibited much higher (20-fold) tolerance for native PAMAM treatment than fibroblasts, whereas BC-PAMAM was significantly toxic only for fibroblasts at 50 µM concentration. Fibroblasts accumulated the native and bioconjugated dendrimers in a concentration-dependent manner at nontoxic range of concentration, with significantly lower bioconjugate loading. After reaching the cytotoxicity level, fluorescein isothiocyanate-PAMAM accumulation remains at high, comparable level. In cancer cells, native PAMAM loading at higher, but not cytotoxic concentrations, was kept at constant level with a sharp increase at toxic concentration. Mander's coefficient calculated for fibroblasts and cancer cells confirmed more efficient native PAMAM penetration as compared to BC-PAMAM. Significant differences in nuclear dendrimer penetration were observed for both cell lines. In cancer cells, PAMAM signals amounted to ~25%-35% of the total nuclei area at all investigated concentrations, with lower level (15%-25%) observed for BC-PAMAM. In fibroblasts, the dendrimer nuclear signal amounted to 15% at nontoxic and up to 70% at toxic concentrations, whereas BC-PAMAM remained at a lower concentration-dependent level (0.3%-20%). Mitochondrial localization of PAMAM and BC-PAMAM revealed similar patterns in both cell lines, depending on the extracellular dendrimer concentration, and presented significantly lower signals from BC-PAMAM, which correlated well with the cytotoxicity.

Shikonin reduces TGF-β1-induced collagen production and contraction in hypertrophic scar-derived human skin fibroblasts

Hypertrophic scarring/hypertrophic scars (HS) is a highly prevalent condition following burns and trauma wounds. Numerous studies have demonstrated that transforming growth factor-β1 (TGF-β1) plays an essential role in the wound healing process by regulating cell differentiation, collagen production and extracellular matrix degradation. The increased expression of TGF-β1 is believed to result in the formation of HS. Shikonin (SHI), an active component extracted from the Chinese herb, Radix Arnebiae, has previously been found to downregulate the expression of TGF-β1 in keratinocyte/fibroblast co-culture conditioned medium. In view of this, in this study, we aimed to further investigate the effects of SHI on TGF-β1-stimulated hypertrophic scar-derived human skin fibroblasts (HSFs) and examined the underlying mechanisms. Cell viability and proliferation were measured using alamarBlue and CyQUANT assays. The total amount of collagen and cell contraction were examined using Sirius red staining and the cell contraction assay kit. Gene expression and signalling pathway activation were detected using reverse transcription-quantitative polymerase chain reaction and western blot analysis. Our results revealed that SHI reduced TGF-β1-induced collagen production through the ERK/Smad signalling pathway and attenuated TGF-β1-induced cell contraction by downregulating α-smooth muscle actin (αSMA) expression in the HSFs. The data from this study provide evidence supporting the potential use of SHI as a novel treatment for HS.

Evaluating the Toxicity of the Analgesic Glutaminase Inhibitor 6-Diazo-5-Oxo-L-Norleucine in vitro and on Rat Dermal Skin Fibroblasts

6-diazo-5-oxo-l-norleucine (DON) is a glutamine antagonist produced naturally by Streptomyces. It inhibits several glutamine-dependent enzyme pathways. Of particular note is its inhibitory effect on the mitochondrial enzyme, glutaminase (GLS), the primary producer of neuronal glutamate. Glutamate is an excitatory neurotransmitter released by primary sensory peripheral nerve terminals and spinal synaptic terminals during pain signaling. Previous work using the tail incision and inflammatory models of pain has demonstrated that a single application of the glutaminase inhibitor, DON, into a surgical incision or the paw of arthritic animals results in pain relief. Even though this compound shows promise as a therapeutic agent, limited data exist regarding its dermal toxicity. As a first approach, we evaluated the effect of several concentrations of DON, on the viability, mitochondrial oxidative capacity and proliferation of rat skin fibroblasts, and then examined the effect of DON after incubation with human liver microsomes on proliferation. Finally, we evaluated DON treated rat skin (tail and hind paw) for cellular necrosis, inflammation and mitotic bodies. No significant effects (p > 0.05) of DON were noted on apoptosis, necrosis, and mitochondrial activity in experiments with cultured rat skin fibroblasts. Flow cytometry revealed the absence of apoptosis in cells treated at the IC₅₀ of 232.5 μM. Enhanced toxicity post-exposure to human microsomes was not observed when compared to DON alone. The H&E staining of the rat skin revealed no obvious pathology in the DON treatment group (10 mM). DON has no/minimal cellular toxicity in vitro on dermal fibroblasts at concentrations that effectively provide analgesia. The local application of concentrations greater than the in vitro IC₅₀ for DON revealed no in vivo skin toxicity. These data provide results indicating zero-to-minimal cellular toxicity with DON and support the further investigation of DON as an analgesic.

Detection of Listeria monocytogenes with short peptide fragments from class IIa bacteriocins as recognition elements

We employed a direct peptide-bacteria binding assay to screen peptide fragments for high and specific binding to Listeria monocytogenes. Peptides were screened from a peptide array library synthesized on cellulose membrane. Twenty four peptide fragments (each a 14-mer) were derived from three potent anti-listerial peptides, Leucocin A, Pediocin PA1, and Curvacin A, that belong to class IIa bacteriocins. Fragment Leu10 (GEAFSAGVHRLANG), derived from the C-terminal region of Leucocin A, displayed the highest binding among all of the library fragments toward several pathogenic Gram-positive bacteria, including L. monocytogenes, Enterococcus faecalis, and Staphylococcus aureus. The specific binding of Leu10 to L. monocytogenes was further validated using microcantilever (MCL) experiments. Microcantilevers coated with gold were functionalized with peptides by chemical conjugation using a cysteamine linker to yield a peptide density of ∼4.8×10(-3) μmol/cm2 for different peptide fragments. Leu10 (14-mer) functionalized MCL was able to detect Listeria with same sensitivity as that of Leucocin A (37-mer) functionalized MCL, validating the use of short peptide fragments in bacterial detection platforms. Fragment Leu10 folded into a helical conformation in solution, like that of native Leucocin A, suggesting that both Leu10 and Leucocin A may employ a similar mechanism for binding target bacteria. The results show that peptide-conjugated microcantilevers can function as highly sensitive platforms for Listeria detection and hold potential to be developed as biosensors for pathogenic bacteria.

N-succinyl chitosan-dialdehyde starch hybrid hydrogels for biomedical applications

A new class of injectable, biocompatible and biodegradable hydrogel is reported. This hydrogel is derived from N-succinyl chitosan (SCS) mixed with water-soluble dialdehyde starch (DAS) without using a conventional chemical crosslinker. The hybrid hydrogel is formed owing to the Schiff's base reaction between amine groups of SCS and dialdehyde groups of DAS to form -CH 000000000000 000000000000 000000000000 111111111111 000000000000 111111111111 000000000000 000000000000 000000000000 N- group. SCS, DAS, and SCS-DAS hybrid hydrogels were synthesized and then characterized by FTIR analysis spectroscopy. The influence of SCS:DAS ratio in hybrid polymers solution on physicochemical properties of resultant hydrogels (e.g. gelation time, gel fraction (%) and equilibrium swelling ratio), surface morphology, in vitro weight loss (%), and mechanical stability was examined. The results demonstrated that SCS content has a profound role for forming tighter crosslinked hybrid hydrogels, where the increase of SCS content reduces the time for hydrogel forming. Also, the water uptake and hydrolytic weight loss decrease. Meanwhile, the DAS content increases, and mechanical properties of SCS-DAS hybrid hydrogels decrease. Curcumin release profile and adhered HGF cells on hydrogel surface sharply influenced the SCS portion in hybrid hydrogel composition. The SCS-DAS hybrid hydrogel properties afforded a possible opportunity to be used as a covalent in situ forming hybrid hydrogels in biomedical applications such as, tissue engineering and cartilage repair.

Paired image- and FACS-based toxicity assays for high content screening of spheroid-type tumor cell cultures

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Design of a high throughput toxicity assay for spheroid-type tumor cell cultures.

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Cell viability, rather than a proxy thereof, is measured.

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Cell viability is measured on a per-cell, rather than per-well, basis.

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The method can be implemented on standard automated microscopes.

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It provides a low-cost approach for accurate and reproducible toxicity screens.

Novel spheroid-type tumor cell cultures directly isolated from patients’ tumors preserve tumor characteristics better than traditionally grown cell lines. However, such cultures are not generally used for high-throughput toxicity drug screens. In addition, the assays that are commonly used to assess drug-induced toxicity in such screens usually measure a proxy for cell viability such as mitochondrial activity or ATP-content per culture well, rather than actual cell death. This generates considerable assay-dependent differences in the measured toxicity values. To address this problem we developed a robust method that documents drug-induced toxicity on a per-cell, rather than on a per-well basis. The method involves automated drug dispensing followed by paired image- and FACS-based analysis of cell death and cell cycle changes. We show that the two methods generate toxicity data in 96-well format which are highly concordant. By contrast, the concordance of these methods with frequently used well-based assays was generally poor. The reported method can be implemented on standard automated microscopes and provides a low-cost approach for accurate and reproducible high-throughput toxicity screens in spheroid type cell cultures. Furthermore, the high versatility of both the imaging and FACS platforms allows straightforward adaptation of the high-throughput experimental setup to include fluorescence-based measurement of additional cell biological parameters.

Porous and strong three-dimensional carbon nanotube coated ceramic scaffolds for tissue engineering

A method to coat high-quality uniform coatings of carbon nanotubes throughout 3D porous structures is developed. Testing of their physical and biological properties demonstrate their potential for application in tissue engineering.

Simultaneous application of BrdU and WST-1 measurements for detection of the proliferation and viability of airway smooth muscle cells

Background

BrdU is a commonly used reagent in cell proliferation assays, and WST-1 measurement is widely used to detect cell viability. However, no previous study has formally reported the combination of the two assays, which may be used to detect the proliferation and viability simultaneously. In this study, we examined the effect of adding BrdU 2 h prior to the WST-1 assay and tried to test the possibility of the combined detection using rat airway smooth muscle cells.

Results

The WST-1 measurements obtained from the combined detection were consistent with those obtained from the separate detection, which suggested that the addition of BrdU 2 h prior to the WST-1 analysis did not affect the WST-1 results. The BrdU measurements obtained from the combined detection also demonstrated the same trend as that obtained from the separate detection, and dosages of 200, 400 and 800 ng/ml testing reagent significantly inhibited the proliferation of rat airway smooth muscle cells.

Conclusions

Our study suggests that the BrdU and WST-1 measurements can be applied simultaneously without mutual interference, which may increase the efficacy and consistency of these measurements to a certain extent.

Celecoxib Inhibits Prion Protein 90-231-Mediated Pro-inflammatory Responses in Microglial Cells

Activation of microglia is a central event in the atypical inflammatory response occurring during prion encephalopathies. We report that the prion protein fragment encompassing amino acids 90-231 (PrP90-231), a model of the neurotoxic activity of the pathogenic prion protein (PrP(Sc)), causes activation of both primary microglia cultures and N9 microglial cells in vitro. This effect was characterized by cell proliferation arrest and induction of a secretory phenotype, releasing prostaglandin E2 (PGE2) and nitric oxide (NO). Conditioned medium from PrP90-231-treated microglia induced in vitro cytotoxicity of A1 mesencephalic neurons, supporting the notion that soluble mediators released by activated microglia contributes to the neurodegeneration during prion diseases. The neuroinflammatory role of COX activity, and its potential targeting for anti-prion therapies, was tested measuring the effects of ketoprofen and celecoxib (preferential inhibitors of COX1 and COX2, respectively) on PrP90-231-induced microglial activation. Celecoxib, but not ketoprofen significantly reverted the growth arrest as well as NO and PGE2 secretion induced by PrP90-231, indicating that PrP90-231 pro-inflammatory response in microglia is mainly dependent on COX2 activation. Taken together, these data outline the importance of microglia in the neurotoxicity occurring during prion diseases and highlight the potentiality of COX2-selective inhibitors to revert microglia as adjunctive pharmacological approach to contrast the neuroinflammation-dependent neurotoxicity.

Comparison of expression and proliferative effect of pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors on human astrocytoma cell lines

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide considered to be a potent regulator of astrocytes. It has been reported that PACAP also affects astrocytoma cell properties, but the proliferative effects of this peptide in previous reports were inconsistent. The purpose of this study was to search for correlations between malignant potential, PACAP/PACAP receptor expression, and the proliferative potential of four astrocytoma cell lines (KNS-81, KINGS-1, SF-126, and YH-13). Immunohistochemical observations were performed using astrocyte lineage markers with a view to establishing malignant potential, which is inversely correlated to differentiation status in astrocytoma cells. YH-13 showed the most undifferentiated astrocyte-like status, and was immunopositive to a cancer stem cell marker, CD44. These observations suggest that YH-13 is the most malignant of the astrocytoma cell lines tested. Moreover, the strongest PAC1-R immunoreactivity was observed in YH-13 cells. Using real-time PCR analysis, no significant differences among cell lines were detected with respect to PACAP mRNA, but PAC1-R and VPAC1-R mRNA levels were significantly increased in YH-13 cells compared with the other cell lines. Furthermore, when cell lines were treated with PACAP (10(-11) M) for 3 days, the YH-13 cell line, but not of the other cell lines, exhibited a significantly increased cell number. These results suggest that PACAP receptor expression is correlated with the malignant and proliferative potential of astrocytoma cell lines.

Cell-based assays for IGF-I bioactivity measurement: overview, limitations and current trends

Insulin-like growth factor-I (IGF-I) is an important growth promoting protein that is involved in numerous cellular responses and multiple biological systems. Although the molecular structure, function and recombinant production of IGF-I in various hosts have been the subject of much researches over the recent past, methods to determine the bioactivity of this protein have not been fully explored. Several assays have traditionally been used to measure IGF-I bioactivity, but have not become a routine laboratory practice due to the high cost involved and technical problems. Thus, there is still a need for a rapid, technically simple and accurate assay to determine IGF-I bioactivity. This review highlights the various cell-based assays currently commercially available for measuring the bioactivity of IGF-I along with their limitations. This is aimed at presenting the modern-day IGF researcher with a holistic overview of the current trends and future prospects regarding IGF-I bioactivity determinations.

A review of reagents for fluorescence microscopy of cellular compartments and structures, Part II: reagents for non-vesicular organelles

A wide range of fluorescent dyes and reagents exist for labeling organelles in live and fixed cells. Choosing between them can sometimes be confusing, and optimization for many of them can be challenging. Presented here is a discussion on the commercially-available reagents that have shown the most promise for each organelle of interest, including endoplasmic reticulum/nuclear membrane, Golgi apparatus, mitochondria, nucleoli, and nuclei, with an emphasis on localization of these structures for microscopy. Included is a featured reagent for each structure with a recommended protocol, troubleshooting guide, and example image.

Pulmonary artery endothelial cell phenotypic alterations in a large animal model of pulmonary arteriovenous malformations after the Glenn shunt

BACKGROUND

Longevity of the superior cavopulmonary connection (SCPC) is limited by the development of pulmonary arteriovenous malformations (PAVM). The goal of this study was to determine whether phenotypic changes in pulmonary artery endothelial cells (PAEC) that favor angiogenesis occur with PAVM formation.

METHODS

A superior vena cava to right pulmonary artery connection was constructed in 5 pigs. Pulmonary arteries were harvested at 6 to 8 weeks after surgery to establish cultures of PAEC and smooth muscle cells, to determine cell proliferation, gene expression, and tubule formation. Abundance of proteins related to angiogenesis was measured in lung tissue.

RESULTS

Contrast echocardiography revealed right-to-left shunting, consistent with PAVM formation. While the proliferation of smooth muscle cells from the right pulmonary artery (shunted side) and left pulmonary artery (nonshunted side) were similar, right PAEC proliferation was significantly higher. Expression profiles of genes encoding cellular signaling proteins were higher in PAECs from the right pulmonary artery versus left pulmonary artery. Protein abundance of angiopoietin-1, and Tie-2 (angiopoietin receptor) were increased in the right lung (both p < 0.05). Tubule formation was increased in endothelial cells from the right pulmonary artery compared with the left pulmonary artery (404 ± 16 versus 199 ± 71 tubules/mm(2), respectively; p < 0.05).

CONCLUSIONS

These findings demonstrate that PAVMs developed in a clinically relevant animal model of SCPC concomitantly with differential changes in PAEC proliferative ability and phenotype. Moreover, there was a significant increase in the angiopoietin/Tie-2 complex in the right lung, which may provide novel therapeutic targets to attenuate PAVM formation after a SCPC.

A simple high-content cell cycle assay reveals frequent discrepancies between cell number and ATP and MTS proliferation assays

In order to efficiently characterize both antiproliferative potency and mechanism of action of small molecules targeting the cell cycle, we developed a high-throughput image-based assay to determine cell number and cell cycle phase distribution. Using this we profiled the effects of experimental and approved anti-cancer agents with a range mechanisms of action on a set of cell lines, comparing direct cell counting versus two metabolism-based cell viability/proliferation assay formats, ATP-dependent bioluminescence, MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) reduction, and a whole-well DNA-binding dye fluorescence assay. We show that, depending on compound mechanisms of action, the metabolism-based proxy assays are frequently prone to 1) significant underestimation of compound potency and efficacy, and 2) non-monotonic dose-response curves due to concentration-dependent phenotypic ‘switching’. In particular, potency and efficacy of DNA synthesis-targeting agents such as gemcitabine and etoposide could be profoundly underestimated by ATP and MTS-reduction assays. In the same image-based assay we showed that drug-induced increases in ATP content were associated with increased cell size and proportionate increases in mitochondrial content and respiratory flux concomitant with cell cycle arrest. Therefore, differences in compound mechanism of action and cell line-specific responses can yield significantly misleading results when using ATP or tetrazolium-reduction assays as a proxy for cell number when screening compounds for antiproliferative activity or profiling panels of cell lines for drug sensitivity.

Group VIB Phospholipase A(2) promotes proliferation of INS-1 insulinoma cells and attenuates lipid peroxidation and apoptosis induced by inflammatory cytokines and oxidant agents

Group VIB Phospholipase A(2) (iPLA(2)γ) is distributed in membranous organelles in which β-oxidation occurs, that is, mitochondria and peroxisomes, and is expressed by insulin-secreting pancreatic islet β-cells and INS-1 insulinoma cells, which can be injured by inflammatory cytokines, for example, IL-1β and IFN-γ, and by oxidants, for example, streptozotocin (STZ) or t-butyl-hydroperoxide (TBHP), via processes pertinent to mechanisms of β-cell loss in types 1 and 2 diabetes mellitus. We find that incubating INS-1 cells with IL-1β and IFN-γ, with STZ, or with TBHP causes increased expression of iPLA(2)γ mRNA and protein. We prepared INS-1 knockdown (KD) cell lines with reduced iPLA(2)γ expression, and they proliferate more slowly than control INS-1 cells and undergo increased membrane peroxidation in response to cytokines or oxidants. Accumulation of oxidized phospholipid molecular species in STZ-treated INS-1 cells was demonstrated by LC/MS/MS scanning, and the levels in iPLA(2)γ-KD cells exceeded those in control cells. iPLA(2)γ-KD INS-1 cells also exhibited higher levels of apoptosis than control cells when incubated with STZ or with IL-1β and IFN-γ. These findings suggest that iPLA(2)γ promotes β-cell proliferation and that its expression is increased during inflammation or oxidative stress as a mechanism to mitigate membrane injury that may enhance β-cell survival.

In vitro osteoblast response to ferritic stainless steel fiber networks for magneto-active layers on implants

The use of a porous coating on prosthetic components to encourage bone ingrowth is an important way of improving uncemented implant fixation. Enhanced fixation may be achieved by the use of porous magneto-active layers on the surface of prosthetic implants, which would deform elastically on application of a magnetic field, generating internal stresses within the in-growing bone. This approach requires a ferromagnetic material able to support osteoblast attachment, proliferation, differentiation, and mineralization. In this study, the human osteoblast responses to ferromagnetic 444 stainless steel networks were considered alongside those to nonmagnetic 316L (medical grade) stainless steel networks. While both networks had similar porosities, 444 networks were made from coarser fibers, resulting in larger inter-fiber spaces. The networks were analyzed for cell morphology, distribution, proliferation, and differentiation, extracellular matrix production and the formation of mineralized nodules. Cell culture was performed in both the presence of osteogenic supplements, to encourage cell differentiation, and in their absence. It was found that fiber size affected osteoblast morphology, cytoskeleton organization and proliferation at the early stages of culture. The larger inter-fiber spaces in the 444 networks resulted in better spatial distribution of the extracellular matrix. The addition of osteogenic supplements enhanced cell differentiation and reduced cell proliferation thereby preventing the differences in proliferation observed in the absence of osteogenic supplements. The results demonstrated that 444 networks elicited favorable responses from human osteoblasts, and thus show potential for use as magnetically active porous coatings for advanced bone implant applications.

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.

An alternative method for cultivation of Lawsonia intracellularis

An alternative method for the cultivation of Lawsonia intracellularis, an obligate intracellular bacterium and the causative agent of proliferative enteropathy, was developed using an Original Space Bag inflated with a mixture of gas containing 10% hydrogen, 10% carbon dioxide, and 80% nitrogen. The flexibility of this protocol allows the testing of various environmental conditions for static cultivation of this bacterium and the development of diagnostic techniques.

Loss-of-function thrombospondin-1 mutations in familial pulmonary hypertension

Most patients with familial pulmonary arterial hypertension (FPAH) carry mutations in the bone morphogenic protein receptor 2 gene (BMPR2). Yet carriers have only a 20% risk of disease, suggesting that other factors influence penetrance. Thrombospondin-1 (TSP1) regulates activation of TGF-β and inhibits endothelial and smooth muscle cell proliferation, pathways coincidentally altered in pulmonary arterial hypertension (PAH). To determine whether a subset of FPAH patients also have mutations in the TSP1 gene (THBS1) we resequenced the type I repeats of THBS1 encoding the TGF-β regulation and cell growth inhibition domains in 60 FPAH probands, 70 nonfamilial PAH subjects, and in large control groups. We identified THBS1 mutations in three families: a novel missense mutation in two (Asp362Asn), and an intronic mutation in a third (IVS8+255 G/A). Neither mutation was detected in population controls. Mutant 362Asn TSP1 had less than half of the ability of wild-type TSP1 to activate TGF-β. Mutant 362Asn TSP1 also lost the ability to inhibit growth of pulmonary arterial smooth muscle cells and was over threefold less effective at inhibiting endothelial cell growth. The IVS8+255 G/A mutation decreased and/or eliminated local binding of the transcription factors SP1 and MAZ but did not affect RNA splicing. These novel mutations implicate THBS1 as a modifier gene in FPAH. These THBS1 mutations have implications in the genetic evaluation of FPAH patients. However, since FPAH is rare, these data are most relevant as evidence for the importance of TSP1 in pulmonary vascular homeostasis. Further examination of THBS1 in the pathogenesis of PAH is warranted.

Spatial arrangement of polycaprolactone/collagen nanofiber scaffolds regulates the wound healing related behaviors of human adipose stromal cells

A sufficient cell source and minimal invasiveness in obtaining human adipose stromal cells (hASCs) hold great promise for their utilization in wound repair. However, little is known about how cell-residing microenvironments regulate the cellular response. In this study we explored the effects of polycaprolactone (PCL)/collagen nanofibers with distinct spatial arrangements (aligned and random) on phenotypic expression of hASCs in vitro. Elongated cell morphology, higher proliferation, and faster migration rate were observed for hASCs cultured on the aligned nanofibers, showing that hASCs could detect the nanofiber spatial arrangement and then distinctively respond. This study on the expression of extracellular matrix (ECM) related genes in hASCs revealed higher synthesis capacity for critical ECM molecules including tropoelastin, collagen I, and matrix metalloproteinase (MMP)-1 on the aligned nanofibers. Integrins α(5), β(1), β(3), β(6,) and transforming growth factor (TGF)-β(1) were differentially regulated by PCL/collagen nanofiber arrangements. Our results indicate that fiber orientation-induced phenotypic change of hASCs may be regulated by integrins and TGF-β signaling synergistically. These findings demonstrate the potential application of hASCs and aligned PCL/collagen nanofibers for accelerated wound repair.

Dimethyloxalyglycine stimulates the early stages of gastrointestinal repair processes through VEGF-dependent mechanisms

Dimethyloxalylglycine (DMOG) is an inhibitor of prolyl-4-hydroxylase domain enzymes. Its potential value and mechanism of actions in preventing/treating gastrointestinal injury are, however, poorly understood. We, therefore, examined the effect of DMOG on influencing gut injury and repair using a variety of in vitro and in vivo models. We performed in vitro studies utilising pro-migratory (wounded monolayer) and proliferation (using DNA quantitation) assays of human stomach (AGS) and colonic (HT29) carcinoma cells. Time course studies examined changes in hypoxia-inducible factor (HIF) and vascular endothelial growth factor (VEGF) levels, a growth factor known to be regulated via HIF. In vivo studies utilised a rat gastric (indomethacin, 20 mg/kg and 3 h restraint) damage model. DMOG stimulated migration in a dose-dependent manner, increasing migration twofold when added at 25μM (P<0.01). Additive effects were seen when DMOG was added to cells in hypoxic conditions. DMOG stimulated proliferation dose dependently, increasing proliferation threefold when added at 70 μM (P<0.01). DMOG caused upregulation of both HIF and VEGF within 4 h of administration. Addition of VEGF neutralising antibody truncated migratory and proliferative activity of DMOG by about 70%. Both oral and subcutaneous administration of DMOG decreased gastric injury without influencing intragastric pH (50% reduction in injury when 1 ml gavaged at 0.57 mM, P < 0.01). Indomethacin reduced tissue HIF and VEGF levels but this was prevented if DMOG was present. In conclusion, DMOG stimulates the early phases of gut repair and VEGF-dependent processes appear relevant. Non-peptide factors such as this may be useful to stabilise or repair gut mucosa.

Extracellular matrix-derived tripeptide proline-glycine-proline inhibits keratinocyte proliferation and migration

Keratinocytes are the predominant cell type in epidermis, and are primarily responsible for the epithelialization phase of wound healing. Previous studies by our group showed a positive correlation between IL-8 concentration and delayed healing of porcine cutaneous partial-thickness wounds. Interleukin-8 and collagen-breakdown product N-acetyl-Pro-Gly-Pro (PGP) are known as chemoattractant molecules for neutrophils during inflammation. The activity of both molecules is dependent on chemokine receptors CXCR1 and CXCR2. In addition to neutrophils, keratinocytes also express CXCR1 and CXCR2. Here we investigated the effects of IL-8 and PGP on keratinocyte proliferation and migration. Our results showed that IL-8 up to 100 ng/mL does not have any significant impact on keratinocyte proliferation or migration. ECM-derived tripeptide PGP chemotactically attracts neutrophils but not keratinocytes. PGP strongly inhibits keratinocyte proliferation and migration in a cell-type specific manner. Thus, collagen breakdown product PGP plays a key role in modulating both the inflammatory and epithelialization phases of wound healing.

Thermostable direct hemolysin downregulates human colon carcinoma cell proliferation with the involvement of E-cadherin, and β-catenin/Tcf-4 signaling

BACKGROUND

Colon cancers are the frequent causes of cancer mortality worldwide. Recently bacterial toxins have received marked attention as promising approaches in the treatment of colon cancer. Thermostable direct hemolysin (TDH) secreted by Vibrio parahaemolyticus causes influx of extracellular calcium with the subsequent rise in intracellular calcium level in intestinal epithelial cells and it is known that calcium has antiproliferative activity against colon cancer.

KEY RESULTS

In the present study it has been shown that TDH, a well-known traditional virulent factor inhibits proliferation of human colon carcinoma cells through the involvement of CaSR in its mechanism. TDH treatment does not induce DNA fragmentation, nor causes the release of lactate dehydrogenase. Therefore, apoptosis and cytotoxicity are not contributing to the TDH-mediated reduction of proliferation rate, and hence the reduction appears to be caused by decrease in cell proliferation. The elevation of E-cadherin, a cell adhesion molecule and suppression of β-catenin, a proto-oncogene have been observed in presence of CaSR agonists whereas reverse effect has been seen in presence of CaSR antagonist as well as si-RNA in TDH treated cells. TDH also triggers a significant reduction of Cyclin-D and cdk2, two important cell cycle regulatory proteins along with an up regulation of cell cycle inhibitory protein p27(Kip1) in presence of CaSR agonists.

CONCLUSION

Therefore TDH can downregulate colonic carcinoma cell proliferation and involves CaSR in its mechanism of action. The downregulation occurs mainly through the involvement of E-cadherin-β-catenin mediated pathway and the inhibition of cell cycle regulators as well as upregulation of cell cycle inhibitors.

Measurement of macrophage growth and differentiation

This unit provides protocols for measuring the abundance and growth of macrophage precursors in agar cultures and the proliferation of isolated mature macrophages in vitro, by either direct cell counting or by DNA measurement. Methods for the immunohistochemical identification of macrophages and the determination of their proliferative status in vivo by immunofluorescence are also included. It also describes methods for characterization of macrophage differentiation through the immunofluorescence analysis of cell-surface expression of CSF-1 receptor.

Peptide arrays for screening cancer specific peptides

In this paper, we describe a novel method to screen peptides for specific recognition by cancer cells. Seventy peptides were synthesized on a cellulose membrane in an array format, and a direct method to study the peptide-whole cell interaction was developed. The relative binding affinity of the cells for different peptides with respect to a lead 12-mer p160 peptide, identified by phage display, was evaluated using the CyQUANT fluorescence of the bound cells. Screening allowed identification of at least five new peptides that displayed higher affinity (up to 3-fold) for MDA-MB-435 and MCF-7 human cancer cells compared to the p160 peptide. These peptides showed very little binding to the control (noncancerous) human umbilical vein endothelial cells (HUVECs). Three of these peptides were synthesized separately and labeled with fluorescein isothiocyanate (FITC) to study their uptake and interaction with the cancer and control cells using confocal laser scanning microscopy and flow cytometry. The results confirmed the high and specific affinity of an 11-mer peptide 11 (RGDPAYQGRFL) and a 10-mer peptide 18 (WXEAAYQRFL) for the cancer cells versus HUVECs. Peptide 11 binds different receptors on target cancer cells as its sequence contains multiple recognition motifs, whereas peptide 18 binds mainly to the putative p160 receptor. The peptide array-whole cell binding assay reported here is a complementary method to phage display for further screening and optimization of cancer targeting peptides for cancer therapy and diagnosis.