Temperature-sensitive migration dynamics in neutrophil-differentiated HL-60 cells

Cell migration plays an essential role in wound healing and inflammatory processes inside the human body. Peripheral blood neutrophils, a type of polymorphonuclear leukocyte (PMN), are the first cells to be activated during inflammation and subsequently migrate toward an injured tissue or infection site. This response is dependent on both biochemical signaling and the extracellular environment, one aspect of which includes increased temperature in the tissues surrounding the inflammation site. In our study, we analyzed temperature-dependent neutrophil migration using differentiated HL-60 cells. The migration speed of differentiated HL-60 cells was found to correlate positively with temperature from 30 to 42 °C, with higher temperatures inducing a concomitant increase in cell detachment. The migration persistence time of differentiated HL-60 cells was higher at lower temperatures (30-33 °C), while the migration persistence length stayed constant throughout the temperature range. Coupled with the increased speed observed at high temperatures, this suggests that neutrophils are primed to migrate more effectively at the elevated temperatures characteristic of inflammation. Temperature gradients exist on both cell and tissue scales. Taking this into consideration, we also investigated the ability of differentiated HL-60 cells to sense and react to the presence of temperature gradients, a process known as thermotaxis. Using a two-dimensional temperature gradient chamber with a range of 27-43 °C, we observed a migration bias parallel to the gradient, resulting in both positive and negative thermotaxis. To better mimic the extracellular matrix (ECM) environment in vivo, a three-dimensional collagen temperature gradient chamber was constructed, allowing observation of biased neutrophil-like differentiated HL-60 migration toward the heat source.

Small Extracellular Vesicles Propagate the Inflammatory Response After Trauma

Trauma is the leading cause of death in individuals under 44 years of age. Thorax trauma (TxT) is strongly associated with trauma-related death, an unbalanced innate immune response, sepsis, acute respiratory distress syndrome, and multiple organ dysfunction. It is shown that different in vivo traumata, such as TxT or an in vitro polytrauma cytokine cocktail trigger secretion of small extracellular nanovesicles (sEVs) from endothelial cells with pro-inflammatory cargo. These sEVs transfer transcripts for ICAM-1, VCAM-1, E-selectin, and cytokines to systemically activate the endothelium, facilitate neutrophil-endothelium interactions, and destabilize barrier integrity. Inhibition of sEV-release after TxT in mice ameliorates local as well as systemic inflammation, neutrophil infiltration, and distant organ damage in kidneys (acute kidney injury, AKI). Vice versa, injection of TxT-plasma-sEVs into healthy animals is sufficient to trigger pulmonary and systemic inflammation as well as AKI. Accordingly, increased sEV concentrations and transfer of similar cargos are observed in polytrauma patients, suggesting a fundamental pathophysiological mechanism.

Scanning electron microscopy preparation of the cellular actin cortex: A quantitative comparison between critical point drying and hexamethyldisilazane drying

The cellular cortex is an approximately 200-nm-thick actin network that lies just beneath the cell membrane. It is responsible for the mechanical properties of cells, and as such, it is involved in many cellular processes, including cell migration and cellular interactions with the environment. To develop a clear view of this dense structure, high-resolution imaging is essential. As one such technique, electron microscopy, involves complex sample preparation procedures. The final drying of these samples has significant influence on potential artifacts, like cell shrinkage and the formation of artifactual holes in the actin cortex. In this study, we compared the three most used final sample drying procedures: critical-point drying (CPD), CPD with lens tissue (CPD-LT), and hexamethyldisilazane drying. We show that both hexamethyldisilazane and CPD-LT lead to fewer artifactual mesh holes within the actin cortex than CPD. Moreover, CPD-LT leads to significant reduction in cell height compared to hexamethyldisilazane and CPD. We conclude that the final drying procedure should be chosen according to the reduction in cell height, and so CPD-LT, or according to the spatial separation of the single layers of the actin cortex, and so hexamethyldisilazane.

Influence of obesity on remodeling of lung tissue and organization of extracellular matrix after blunt thorax trauma

Background

Previously, it has been shown that obesity is a risk factor for recovery, regeneration, and tissue repair after blunt trauma and can affect the rate of muscle recovery and collagen deposition after trauma. To date, lung tissue regeneration and extracellular matrix regulation in obese mice after injury has not been investigated in detail yet.

Methods

This study uses an established blunt thorax trauma model to analyze morphological changes and alterations on gene and protein level in lean or obese (diet-induced obesity for 16 ± 1 week) male C57BL/6 J mice at various time-points after trauma induction (1 h, 6 h, 24 h, 72 h and 192 h).

Results

Morphological analysis after injury showed lung parenchyma damage at early time-points in both lean and obese mice. At later time-points a better regenerative capacity of lean mice was observed, since obese animals still exhibited alveoli collapse, wall thickness as well as remaining filled alveoli structures. Although lean mice showed significantly increased collagen and fibronectin gene levels, analysis of collagen deposition showed no difference based on colorimetric quantification of collagen and visual assessment of Sirius red staining. When investigating the organization of the ECM on gene level, a decreased response of obese mice after trauma regarding extracellular matrix composition and organization was detectable. Differences in the lung tissue between the diets regarding early responding MMPs (MMP8/9) and late responding MMPs (MMP2) could be observed on gene and protein level. Obese mice show differences in regulation of extracellular matrix components compared to normal weight mice, which results in a decreased total MMP activity in obese animals during the whole regeneration phase. Starting at 6 h post traumatic injury, lean mice show a 50% increase in total MMP activity compared to control animals, while MMP activity in obese mice drops to 50%.

Conclusions

In conclusion, abnormal regulation of the levels of extracellular matrix genes in the lung may contribute to an aberrant regeneration after trauma induction with a delay of repair and pathological changes of the lung tissue in obese mice.

Postoperative treatment of metacarpal fractures-Classical physical therapy compared with a home exercise program

STUDY DESIGN

Prospective cohort randomized controlled trial.

PURPOSE OF THE STUDY

Is either a home exercise (HE) program or traditional physical therapy (PT) more effective in the postoperative management of metacarpal fractures?

METHODS

Sixty patients suffering from nonthumb metacarpal fractures who received mobilization-stable open reduction and internal fixation were included. All patients were prospectively randomized into either the PT group or the HE group. Follow-up examinations at 2, 6 and 12 weeks postoperatively.

RESULTS

After 2 weeks, the range of motion (ROM) in both groups was still severely reduced. Twelve weeks after surgery the ROM improved to 245° (PT) and 256° (HE). Grip strength after 6 weeks was 68% (PT) and 71% (HE) when compared to the non-injured hand, improving to 91% (PT) and 93% (HE) after 12 weeks.

CONCLUSION

Study results show that both HE program and traditional PT are effective in the postoperative management of metacarpal fractures.

LEVEL OF EVIDENCE

II.

Cytokine patterns in critically ill patients undergoing percutaneous tracheostomy

The inflammatory response to acute injury among humans has proved difficult to study due to the significant heterogeneity encountered in actual patients. We set out to characterize the immune response to a model injury with reduced heterogeneity, a tracheostomy, among stable critical care patients, using a broad cytokine panel and clinical data. Twenty-three critical care patients undergoing percutaneous bedside tracheostomies were recruited in a medical intensive care unit. Blood samples were collected at five intervals during 24-h peri-procedure. Patients were followed-up for 28 days for clinical outcomes. There were no statistically significant changes in any of the cytokines between the five time-points when studied as a whole cohort. Longitudinal analysis of the cytokine patterns at the individual patient level with a clustering algorithm showed that, notwithstanding the significant heterogeneity observed, the patients' cytokine responses can be classified into three broad patterns that show increasing, decreasing or no major changes from the baseline. This analytical approach also showed statistically significant associations between cytokines, with those most likely to be associated being interleukin (IL)-6, granulocyte colony-stimulating factor (GCSF) and ferritin, as well as a strong tri-way correlation between GCSF, monocyte chemoattractant protein 1 (MCP1) and macrophage inflammatory protein-1β (MIP1β). In conclusion, in this standard human model of soft tissue injury, by applying longitudinal analysis at the individual level, we have been able to identify the cytokine patterns underlying the seemingly random, heterogeneous patient responses. We have also identified consistent cytokine interactions suggesting that IL-6, GCSF, MCP1 and MIP1β are the cytokines most probably driving the immune response to this injury.

Adjuvant Chemotherapy of Locally Advanced Colon Cancer: Final Results of a Randomized Trial Comparing 5-Fluorouracil and Folinic Acid with Folfiri

BACKGROUND

There is still the need to optimize adjuvant treatment of colon cancer (CC). Standard adjuvant chemotherapy using 5-fluorouracil (FU) and folinic acid (FA) was compared with a combination including irinotecan (Folfiri). The aim of the present report was to analyze overall survival (OS) after long-term follow-up, to summarize final recurrence rates and toxicity data, and to identify possible clinical and pathological factors associated with prognosis.

METHODS

Patients (CC stage IIb and III) were randomized to a 6-month treatment with FUFA or Folfiri. The trial was closed after 275 of 588 planned patients, 269 of which were included in the intention-to-treat analysis.

RESULTS

133 and 136 patients received FUFA and Folfiri, respectively. Adjuvant therapy was not completed for 16 FUFA (12.0%) and 44 Folfiri (32.4%) patients. Toxicities grade III and IV were observed in 17 (12.8%) patients treated with FUFA and in 50 (36.8%) patients treated with Folfiri. Recurrences occurred in 46 of 133 (34.6%) and in 47 of 136 (34.6%) patients who received FUFA and Folfiri, respectively. 5-year OS rates were 69.9% (95% confidence interval (CI): 61.2-77.1) for FUFA and 72.7% (95% CI: 63.9-79.8) for Folfiri. OS was associated with tumor grading (1 & 2 vs. 3), tumor sub-stage (II vs. IIIa vs. IIIb vs. IIIc), and tumor location (left vs. right colon).

CONCLUSION

Folfiri cannot be generally recommended for adjuvant chemotherapy of CC. Besides tumor grading and sub-staging, prognosis of CC may depend on tumor location. Left-sided tumors had a significantly better prognosis irrespective of treatment.

PKD regulates actin polymerization, neutrophil deformability, and transendothelial migration in response to fMLP and trauma

Neutrophils are important mediators of the innate immune defense and of the host response to a physical trauma. Because aberrant infiltration of injured sites by neutrophils was shown to cause adverse effects after trauma, we investigated how neutrophil infiltration could be modulated at the cellular level. Our data indicate that protein kinase D (PKD) is a vital regulator of neutrophil transmigration. PKD phosphorylates the Cofilin-phosphatase Slingshot-2L (SSH-2L). SSH-2L in turn dynamically regulates Cofilin activity and actin polymerization in response to a chemotactic stimulus for neutrophils, for example, fMLP. Here, we show that inhibition of PKD by two specific small molecule inhibitors results in broad, unrestricted activation of Cofilin and strongly increases the F-actin content of neutrophils even under basal conditions. This phenotype correlates with a significantly impaired neutrophil deformability as determined by optical stretcher analysis. Consequently, inhibition of PKD impaired chemotaxis as shown by reduced extravasation of neutrophils. Consequently, we demonstrate that transendothelial passage of both, neutrophil-like NB4 cells and primary PMNs recovered from a hemorrhagic shock trauma model was significantly reduced. Thus, inhibition of PKD may represent a promising modulator of the neutrophil response to trauma.

CK1α overexpression correlates with poor survival in colorectal cancer

Background

Colorectal cancer (CRC) is the fourth leading cause of cancer related deaths worldwide and prognosis in advanced tumor stage still remains poor. Since CK1 isoforms have been reported to be deregulated in several tumor entities CK1 has emerged as a novel drug target in cancer therapy. In this study we set out to investigate whether CK1α might have the potential to serve as prognostic marker.

Methods

CK1α RNA and protein expression levels in healthy and tumor tissue of CRC patients were analyzed using quantitative real-time PCR and Western Blot analysis, respectively. Prognostic relevance was investigated by correlating obtained CK1α expression levels with patients’ survival rate generating Kaplan-Meier survival plots.

Results

It could be shown that CK1α is overexpressed in colorectal tumor tissue compared to normal tissue and CK1α overexpression in tumor tissue correlates with poor survival in CRC patients. Results become more significant when only considering patients with high-grade tumors, as well as patients assigned to UICC II and UICC III stage. Furthermore, Cox regression analysis revealed that CK1α is an independent prognostic factor. In addition, tumors expressing decreased levels of the kinase reveal positive effects on overall survival when localized in the right colon compared to those in the left side.

Conclusion

In summary, this study provides evidence for the first time that CK1α RNA levels might serve as prognostic marker for CRC.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4019-0) contains supplementary material, which is available to authorized users.

Complement C5a-Induced Changes in Neutrophil Morphology During Inflammation

The complement and neutrophil defence systems, as major components of innate immunity, are activated during inflammation and infection. For neutrophil migration to the inflamed region, we hypothesized that the complement activation product C5a induces significant changes in cellular morphology before chemotaxis. Exposure of human neutrophils to C5a dose- and time-dependently resulted in a rapid C5a receptor-1 (C5aR1)-dependent shape change, indicated by enhanced flow cytometric forward-scatter area values. Similar changes were observed after incubation with zymosan-activated serum and in blood neutrophils during murine sepsis, but not in mice lacking the C5aR1. In human neutrophils, Amnis high-resolution digital imaging revealed a C5a-induced decrease in circularity and increase in the cellular length/width ratio. Biomechanically, microfluidic optical stretching experiments indicated significantly increased neutrophil deformability early after C5a stimulation. The C5a-induced shape changes were inhibited by pharmacological blockade of either the Cl-/HCO3--exchanger or the Cl^- -channel. Furthermore, actin polymerization assays revealed that C5a exposure resulted in a significant polarization of the neutrophils. The functional polarization process triggered by ATP-P2X/Y-purinoceptor interaction was also involved in the C5a-induced shape changes, because pretreatment with suramin blocked not only the shape changes but also the subsequent C5a-dependent chemotactic activity. In conclusion, the data suggest that the anaphylatoxin C5a regulates basic neutrophil cell processes by increasing the membrane elasticity and cell size as a consequence of actin-cytoskeleton polymerization and reorganization, transforming the neutrophil into a migratory cell able to invade the inflammatory site and subsequently clear pathogens and molecular debris.

Neuropeptide FF increases M2 activation and self-renewal of adipose tissue macrophages

The quantity and activation state of adipose tissue macrophages (ATMs) impact the development of obesity-induced metabolic diseases. Appetite-controlling hormones play key roles in obesity; however, our understanding of their effects on ATMs is limited. Here, we have shown that human and mouse ATMs express NPFFR2, a receptor for the appetite-reducing neuropeptide FF (NPFF), and that NPFFR2 expression is upregulated by IL-4, an M2-polarizing cytokine. Plasma levels of NPFF decreased in obese patients and high-fat diet-fed mice and increased following caloric restriction. NPFF promoted M2 activation and increased the proliferation of murine and human ATMs. Both M2 activation and increased ATM proliferation were abolished in NPFFR2-deficient ATMs. Mechanistically, the effects of NPFF involved the suppression of E3 ubiquitin ligase RNF128 expression, resulting in enhanced stability of phosphorylated STAT6 and increased transcription of the M2 macrophage-associated genes IL-4 receptor α (Il4ra), arginase 1 (Arg1), IL-10 (Il10), and alkylglycerol monooxygenase (Agmo). NPFF induced ATM proliferation concomitantly with the increase in N-Myc downstream-regulated gene 2 (Ndrg2) expression and suppressed the transcription of Ifi200 cell-cycle inhibitor family members and MAF bZIP transcription factor B (Mafb), a negative regulator of macrophage proliferation. NPFF thus plays an important role in supporting healthy adipose tissue via the maintenance of metabolically beneficial ATMs.

Both monovalent cations and plectin are potent modulators of mechanical properties of keratin K8/K18 networks

Intermediate filament (IF) networks are a major contributor to cell rigidity and thus serve as vital elements to preserve the integrity of entire cell layers. Keratin K8 and K18 IFs are the basic constituents of the cytoskeleton of epithelial cells. The mechanical properties of K8/K18 networks depend on the structural arrangements of individual filaments within the network. This paper investigates the architecture of these networks in vitro under the influence of the monovalent cation potassium and that of the cytolinker protein plectin. Whereas increasing amounts of potassium ions lead to filament bundling, plectin interlinks filaments at filament intersection points but does not lead to bundle formation. The mechanics of the resulting networks are investigated by microrheology with assembled K8/K18 networks. It is shown that bundling induced by potassium ions significantly stiffens the network. Furthermore, our measurements reveal an increase in plectin-mediated keratin network rigidity as soon as an amount corresponding to more than 20% of the plectin present in cells is added to the keratin IF networks. In parallel, we investigated the influence of plectin on cell rigidity in detergent-extracted epithelial vulva carcinoma derived A431 cells in situ. These cytoskeletons, containing mostly IFs, actin filaments and associated proteins, exhibit a significantly decreased stiffness, when plectin is downregulated to ≈10% of the normal value. Therefore, we assume that plectin, via the formation of IF-IF connections and crosslinking of IFs to actin filaments, is an important contributor to cell stiffness.

Cortactin is a scaffolding platform for the E-cadherin adhesion complex and is regulated by protein kinase D1 phosphorylation

Dynamic regulation of cell-cell adhesion by the coordinated formation and dissolution of E-cadherin-based adherens junctions is crucial for tissue homeostasis. The actin-binding protein cortactin interacts with E-cadherin and enables F-actin accumulation at adherens junctions. Here, we were interested to study the broader functional interactions of cortactin in adhesion complexes. In line with literature, we demonstrate that cortactin binds to E-cadherin, and that a posttranslational modification of cortactin, RhoA-induced phosphorylation by protein kinase D1 (PKD1; also known as PRKD1) at S298, impairs adherens junction assembly and supports their dissolution. Two new S298-phosphorylation-dependent interactions were also identified, namely, that phosphorylation of cortactin decreases its interaction with β-catenin and the actin-binding protein vinculin. In addition, binding of vinculin to β-catenin, as well as linkage of vinculin to F-actin, are also significantly compromised upon phosphorylation of cortactin. Accordingly, we found that regulation of cell-cell adhesion by phosphorylation of cortactin downstream of RhoA and PKD1 is vitally dependent on vinculin-mediated protein interactions. Thus, cortactin, unexpectedly, is an important integration node for the dynamic regulation of protein complexes during breakdown and formation of adherens junctions.

Stratified Survival Analysis After Adjuvant Chemotherapy of Colon Cancer Reveals a Benefit for Older Patients

AIM

Adjuvant treatment is still controversially discussed for elderly colon cancer (CC) patients. Our aim was to investigate the benefit of adjuvant treatment for younger (<70 years) and elderly (≥70 years) patients.

PATIENTS AND METHODS

The long-term outcome of patients (n=855) enrolled in a randomized controlled trial comparing adjuvant chemotherapy with 5-FU alone, 5-FU plus folinic acid (FA), and 5-FU plus interferon-alpha (IFNa) was compared in younger (<70 years) and elderly (≥70 years) patients using a quotient of each patient's survival time and his expected residual life expectancy (QSL) and a multivariate Cox proportional hazards model.

RESULTS

Eight-year overall survival (OS) rates were 58.3% and 57.4% for younger (n=653) and elderly (n=202) patients, respectively. In elderly patients, 8-year OS rates were 51.4%, 61.8%, and 56.3, and median QSL scores were 0.338, 0.371, and 0.343 for 5-FU (n=59), 5-FU plus FA (n=76), and 5-FU plus IFNa (n=67), respectively. In elderly patients treatment with 5-FU plus FA decreased the risk for an event by 1.5-fold compared to 5-FU (HR=0.657, 95%CI=0.495-0.870, p=0.004) and 5-FU plus INFa (HR=0.685, 95%CI=0.515-0.912, p=0.009).

CONCLUSION

Our analysis clearly demonstrates for the first time an additional benefit of FA for adjuvant treatment of elderly CC patients. We conclude that this regimen is very safe and effective for adjuvant treatment of elderly patients.

Microrheology of keratin networks in cancer cells

Microrheology is a valuable tool to determine viscoelastic properties of polymer networks. For this purpose measurements with embedded tracer beads inside the extracted network of pancreatic cancer cells were performed. Observing the beads motion with a CCD-high-speed-camera leads to the dynamic shear modulus. The complex shear modulus is divided into real and imaginary parts which give insight into the mechanical properties of the cell. The dependency on the distance of the embedded beads to the rim of the nucleus shows a tendency for a decreasing storage modulus. We draw conclusions on the network topology of the keratin network types based on the mechanical behavior.

Laparoscopic intraperitoneal mesh fixation with fibrin sealant of a Spigelian hernia

Spigelian hernia is a rare clinical entity and has a subtle clinical presentation with vague abdominal pain, which can cause an important delay in diagnosis. Given the relatively high risk of incarceration the diagnosis of Spigelian hernia is an indication for surgical repair. Laparoscopic Spigelian mesh herniorraphy has gained recognition as an effective tension-free method and is associated with lower recurrence. Appropriate fixation techniques are however required to reduce complications such as nerve irritation, hematoma, and postoperative chronic pain. In this case report we describe a novel approach in laparoscopic mesh repair of Spigelian hernia, securing a lightweight composite mesh with fibrin sealant. This fixation seems to be a reasonable, feasible alternative to the standard tissue-penetrating mesh fixation.

Late manifestation of subclinical hyperthyroidism after goitrogenesis in an index patient with a N670S TSH receptor germline mutation masquerading as TSH receptor antibody negative Graves' disease

In 27 families with familial non-autoimmune hyperthyroidism (FNAH) reported up to date, the onset of hyperthyroidism varies from 18 months to 60 years. Also the manifestation of goitres is variable in these families. A 74-year-old woman first presented at the age of 69 years with tachyarrhythmia and hypertension. After initial treatment of her hypertension and oral anticoagulation for her intermittent atrial fibrillation, a thyroid workup revealed a suppressed TSH and normal fT3 and fT4. TPO, TSH receptor (TSHR), and thyroglobulin antibodies were negative. Thyroid ultrasound revealed a thyroid volume of 102 ml with several nodules with diameters of up to 2.6 cm right and up to 1.8 cm left. Scintigraphy showed a homogeneous Technetium-99 m ((99 m)Tc) uptake of 1.27%. She was subsequently treated with 1 GBq radioiodine ((131)I). At the age of 74, her thyroid function was normal and her thyroid volume decreased to 90 ml. Because of the diffuse (99 m)Tc uptake and the negative TPO, TSHR, and thyroglobulin antibodies, genetic analysis of her TSHR gene was performed, in spite of her negative family history for hyperthyroidism. Sequencing revealed a N670S TSHR germline mutation. Previous in vitro characterisation of this TSHR mutation suggests a weak constitutive activity, yet the experimental data are ambiguous. This case illustrates the necessity to analyse patients with hyperthyroidism accompanied by diffuse (99 m)Tc uptake and negative TPO, TSHR, and thyroglobulin antibodies for TSHR germline mutations. Moreover, it demonstrates that TSHR germline mutations may first lead to longstanding nodular goitrogenesis before the late manifestation of subclinical hyperthyroidism.

Critical review: cellular mechanobiology and amoeboid migration

Cell motility is important for tissue homeostasis and plays a central role in various pathologies, notably inflammation and cancer. Research into the critical processes involved in cell migration has so far mostly focused on cell adhesion and proteolytic degradation of the extracellular matrix. However, pharmacological interference with these processes only partially blocks cell motility in vivo. In this review we summarize the arising evidence that the mechanical properties of the cell body have a major role to play in cell motility--especially in a low-adhesion, amoeboid-like migration mode in three-dimensional tissue structures. We summarize the processes determining cell mechanics and discuss relevant measurement technologies including their applications in medical cell biology.

The bioactive lipid sphingosylphosphorylcholine induces differentiation of mouse embryonic stem cells and human promyelocytic leukaemia cells

Sphingosylphosphorylcholine (SPC) is the major component of high-density lipoproteins (HDL) in blood plasma. The bioactive lipid acts mainly via G protein coupled receptors (GPCRs). Similar to ligands of other GPCRs, SPC has multiple biological roles including the regulation of proliferation, migration, angiogenesis, wound healing and heart rate. Lysophospholipids and their receptors have also been implicated in cell differentiation. A potential role of SPC in stem cell or tumour cell differentiation has been elusive so far. Here we examined the effect of SPC on the differentiation of mouse embryonic stem (ES) cells and of human NB4 promyelocytic leukemia cells, a well established tumour differentiation model. Our data show that mouse embryonic stem cells and NB4 cells express the relevant GPCRs for SPC. We demonstrate both at the level of morphology and of gene expression that SPC induces neuronal and cardiac differentiation of mouse ES cells. Furthermore, SPC induces differentiation of NB4 cells by a mechanism which is critically dependent on the activity of the MEK-ERK cascade. Thus, the bioactive lipid SPC is a novel differentiation inducing agent both for mouse ES cells, but also of certain human tumour cells.

Statistical analysis of the three-dimensional structure of centromeric heterochromatin in interphase nuclei

Translocation of genes into the pericentromeric heterochromatin occurs during cellular differentiation and leads to a long-term silencing of these genes. Consequently, a structural remodelling of this heterochromatin compartment is observed during differentiation but this remains to be defined from a topological point of view. In a previous study, we analysed the three-dimensional (3D) distribution patterns of centromere clusters (chromocentres) by confocal scanning laser microscopy and found that differentiation of the promyelocytic leukaemia cell line NB4 along the neutrophil lineage is associated with a progressive clustering of centromeres. This clustering was reflected by a decreased number of detectable chromocentres, i.e. groups of centromeres with a distance below the diffraction-limited resolution of optical microscopy. The purpose of this study was to perform a statistical analysis of the 3D distribution of chromocentres in NB4 cells. Several point field characteristics (Ripley's K-function, L-function, pair correlation function, nearest-neighbour distribution function) were investigated to describe the topology of chromocentres during differentiation of NB4 cells. The pair correlation function revealed a higher frequency of chromocentre distances between 350 nm and 800 nm in undifferentiated NB4 cells as compared with differentiated cells. The L-function and the nearest-neighbour distribution function confirmed these results. These data imply the existence of intranuclear heterochromatin zones formed by functionally related centromeric regions. In view of the observed decrease in the number of detectable chromocentres during differentiation, we hypothesize that these zones with a diameter of 350-800 nm in undifferentiated NB4 cells contract into zones with a diameter below 350 nm in differentiated cells.

Sphingosylphosphorylcholine regulates keratin network architecture and visco-elastic properties of human cancer cells

Sphingosylphosphorylcholine (SPC) is a naturally occurring bioactive lipid that is present in high density lipoproteins (HDL) particles and found at increased levels in blood and malignant ascites of patients with ovarian cancer. Here, we show that incubation of human epithelial tumour cells with SPC induces a perinuclear reorganization of intact keratin 8-18 filaments. This effect is specific for SPC, largely independent of F-actin and microtubules, and is accompanied by keratin phosphorylation. In vivo visco-elastic probing of single cancer cells demonstrates that SPC increases cellular elasticity. Accordingly, SPC stimulates migration of cells through size-limited pores in a more potent manner than lysophosphatidic acid (LPA). LPA induces actin stress fibre formation, but does not reorganize keratins in cancer cells and hence increases cellular stiffness. We propose that reorganization of keratin by SPC may facilitate biological phenomena that require a high degree of elasticity, such as squeezing of cells through membranous pores during metastasis.

Spatial distribution patterns of interphase centromeres during retinoic acid-induced differentiation of promyelocytic leukemia cells

BACKGROUND

The pericentromeric heterochromatin is an important element for the regulation of gene silencing. Its spatial distribution during interphase appears to be cell-type specific. This study analyzes three-dimensional (3D) centromere distribution patterns during cellular differentiation along the neutrophil pathway.

METHODS

Differentiation of the promyelocytic leukemia cell line NB4 was induced by retinoic acid. Centromeres in interphase nuclei were visualized by immunofluorescence staining of centromere-associated proteins with CREST serum. 3D images of nuclei were obtained by confocal microscopy. Automated methods for the segmentation of point-like objects in 3D images were implemented to detect the position of centromeres. Features of centromere localization patterns were determined by constructing the minimal spanning tree of the centromere distribution.

RESULTS

In differentiated NB4 cells, the number of centromere conglomerates (chromocenters) was decreased and the distance between chromocenters was increased as compared with untreated controls. The nuclear volume did not differ between the two groups.

CONCLUSIONS

The measured rearrangement of centromeres indicates a progressive clustering of heterochromatin and a global remodeling of interphase chromosome territories during differentiation of NB4 cells. The developed methods for the analysis of 3D centromere distribution patterns provide the opportunity for a fast and objective analysis of heterochromatin remodeling.

Contractile hyporesponsiveness of hepatic arteries in humans with cirrhosis: evidence for a receptor-specific mechanism

Splanchnic vasodilatation and vascular hyporesponsiveness to vasopressors are characteristic features of patients with cirrhosis. Although the vascular response to different vasopressors has been shown to be attenuated in cirrhosis, alterations on the receptor level are discussed controversially. Thus, impaired postreceptor signaling has been postulated. However, so far this has not been studied in human splanchnic vessels. Therefore, we assessed the vascular response of human hepatic arteries after activating the G-protein-dependent signal transduction pathway by stimulation with angiotensin II, the thromboxane A(2) analog U46619, or by G-protein activation with NaF/AlCl(3). After endothelium denudation, cumulative isometric concentration contraction curves were obtained for hepatic arteries from 32 cirrhotic patients undergoing liver transplantation and from 40 organ donors after stimulation with either angiotensin II (10(-11)-10(-5) mol/L), U46619 (10(-10)-10(-6) mol/L) or AlCl(3) (30 micromol/L)/NaF (10(-4)-3 x 10(-2) mol/L). Hepatic arteries from cirrhotic patients were markedly less responsive to angiotensin II (P <.0001) than those from organ donors. Both stimulation of the G-protein phospholipase C pathway via the thromboxane A(2) receptor and receptor-independent G-protein stimulation with AlCl(3)/NaF, induced an intact contractile response. In conclusion, the G-protein-dependent signal transduction system itself is unaltered in cirrhosis. Hence, the cause of the hyporesponsiveness to some vasoconstrictors in cirrhosis appears to be a receptor-specific phenomenon localized upstream from the G-protein level.

Remodeling of vimentin cytoskeleton correlates with enhanced motility of promyelocytic leukemia cells during differentiation induced by retinoic acid

The intermediate filament (IFs) cytoskeleton is one of the major determinants for the mechanical properties of cytoplasm. Vimentin is the major IFs protein in peripheral blood neutrophils. We investigated its expression and function during neutrophil differentiation using the promyelocytic leukemia cell line NB4. The differentiation of NB4 cells along the neutrophil lineage and the monocytic pathway was induced by all-trans retinoic acid (ATRA) and phorbol esters (PMA), respectively. We demonstrated a down-regulation of vimentin after ATRA treatment of NB4 cells by immunoblotting and immunofluorescence. The architecture of the vimentin cytoskeleton in differentiated NB4 cells resembled that observed in mature neutrophils. In contrast, we showed a slight increase of vimentin content in phorbol ester (PMA)-treated NB4 cells. The structural features of the vimentin cytoskeleton obtained by image analysis showed significant differences in network density and directionality between ATRA-treated NB4 cells and controls. The functional consequence of the cytoskeletal remodeling for the mechanical properties of NB4 cells was assessed in migration assays. After ATRA treatment, we found a 4-fold increased migration of NB4 cells across transwell membranes with a 8 microm pore size without any cell size modification. No significant differences between PMA-treated NB4 cells and control cells could be observed using similar tests. These results indicate that both vimentin expression and network architecture are tightly controlled during neutrophil differentiation to regulate the mechanical properties of these cells.

An electromyographic analysis of the hip abductor muscles during a standing work task

Research data strongly suggest that osteoarthritis of the hip occurs statistically more often on the right side. A possible contributing factor to this right-sided bias in frequency may be that the articular cartilage on the right hip is subjected to relatively higher muscular-based forces throughout a lifetime. As an initial attempt to study this possibility, this research examined healthy persons to determine the existence of a "dominant" hip similar to that expressed for handedness. Electromyographic (EMG) analysis was used to compare the electrical activity between the right and left hip abductor muscles during a standardized standing work task using 40 right-handed and 40 left-handed healthy subjects. Analysis of the data showed that the hip muscle on the side of the subject's handedness produced higher normalized EMG activity than did the opposite hip; however, the differences were not all statistically significant. The trend of this data set, however, warrants further research into a possible association between hip dominance, asymmetrical muscle use, and the development of hip osteoarthritis.