Use of the Ki67 promoter to label cell cycle entry in living cells

Type I interferon induced during chronic viral infection favors B-cell development in the thymus

Chronic viral infections cause thymic involution yet the potential for broader, longer-term impact on thymic composition remains unexplored. Here we show that chronic, but not acute, lymphocytic choriomeningitis virus infection promotes a unique population of immature B cells in the thymus. We show that chronic viral infection promotes signals within the thymus, including the expression of B-cell activating factor (BAFF), that favor the maturation of this population as these cells acquire expression of CD19 and immunoglobulin M. Mechanistically, type I interferon (IFN-I), predominantly IFNβ, signals to thymic hematopoietic cells, strongly delaying T-cell development at the earliest precursor stage. Furthermore, IFN-I signaling to the nonhematopoietic compartment provides a second signal essential to favor B-cell differentiation and maturation within the thymus. Importantly, chronic infection yields changes in the B-cell population for at least 50 days following infection, long after thymic atrophy has subsided. Thus, the inflammatory milieu induced by chronic viral infection has a profound, and long-lasting, effect on thymic composition leading to the generation of a novel population of thymic B cells.

A highly sensitive strategy for monitoring real-time proliferation of targeted cell types in vivo

Cell proliferation processes play pivotal roles in timely adaptation to many biological situations. Herein, we establish a highly sensitive and simple strategy by which time-series showing the proliferation of a targeted cell type can be quantitatively monitored in vivo in the same individuals. We generate mice expressing a secreted type of luciferase only in cells producing Cre under the control of the Ki67 promoter. Crossing these with tissue-specific Cre-expressing mice allows us to monitor the proliferation time course of pancreatic β-cells, which are few in number and weakly proliferative, by measuring plasma luciferase activity. Physiological time courses, during obesity development, pregnancy and juvenile growth, as well as diurnal variation, of β-cell proliferation, are clearly detected. Moreover, this strategy can be utilized for highly sensitive ex vivo screening for proliferative factors for targeted cells. Thus, these technologies may contribute to advancements in broad areas of biological and medical research.

Flavonoid-Rich Extract of Oldenlandia diffusa (Willd.) Roxb. Inhibits Gastric Cancer by Activation of Caspase-Dependent Mitochondrial Apoptosis

OBJECTIVE

To evaluate the apoptosis and cycle arrest effects of Oldenlandia diffusa flavonoids on human gastric cancer cells, determine the action mechanisms in association with the mitochondrial dependent signal transduction pathway that controls production of reactive oxygen species (ROS), and evaluate the pharmacodynamics of a mouse xenotransplantation model to provide a reference for the use of flavonoids in prevention and treatment of gastric cancer.

METHODS

Flavonoids were extracted by an enzymatic-ultrasonic assisted method and purified with D-101 resin. Bioactive components were characterized by high-performance liquid chromatography. Cell lines MKN-45, AGS, and GES-1 were treated with different concentrations of flavonoids (64, 96, 128, 160 µg/mL). The effect of flavonoids on cell viability was evaluated by MTT method, and cell nuclear morphology was observed by Hoechst staining. The apoptosis rate and cell cycle phases were measured by flow cytometry, the production of ROS was detected by laser confocal microscope, the mitochondrial membrane potential (MMP) were observed by fluorescence microscope, and the expression of apoptotic proteins related to activation of mitochondrial pathway were measured by immunoblotting. MKN-45 cells were transplanted into BALB/c nude mice to establish a xenograft tumor model. Hematoxylin and eosin staining was used to reveal the subcutaneous tumor tissue. The tumor volume and tumor weight were measured, the expression levels of proliferation markers proliferating cell nuclear antigen (PCNA) and Ki-67 were detected by immunohistochemistry, and the expression levels of CA72-4 were measured by enzyme linked immunosorbent assay.

RESULTS

Oldenlandia diffusa flavonoids inhibited proliferation of MKN-45 and AGS human gastric cancer cells, arrested the cell cycle in G₁/S phase, induced accumulation of ROS in the process of apoptosis, and altered MMP. In addition, flavonoids increased Apaf-1, Cleaved-Caspase-3, and Bax, and decreased Cyclin A, Cdk2, Bcl-2, Pro-Caspase-9, and Mitochondrial Cytochrome C (P<0.05). The MKN-45 cell mouse xenotransplantation model further clarified the growth inhibitory effect of flavonoids towards tumors. The expression levels of PCNA and Ki-67 decreased in each flavonoid dose group, the expression level of CA72-4 decreased (P<0.05).

CONCLUSION

Flavonoids derived from Oldenlandia diffusa can inhibit proliferation and induce apoptosis of human gastric cancer cells by activating the mitochondrial controlled signal transduction pathway.

A SOX2-engineered epigenetic silencer factor represses the glioblastoma genetic program and restrains tumor development

Current therapies remain unsatisfactory in preventing the recurrence of glioblastoma multiforme (GBM), which leads to poor patient survival. By rational engineering of the transcription factor SOX2, a key promoter of GBM malignancy, together with the Kruppel-associated box and DNA methyltransferase3A/L catalytic domains, we generated a synthetic repressor named SOX2 epigenetic silencer (SES), which induces the transcriptional silencing of its original targets. By doing so, SES kills both glioma cell lines and patient-derived cancer stem cells in vitro and in vivo. SES expression, through local viral delivery in mouse xenografts, induces strong regression of human tumors and survival rescue. Conversely, SES is not harmful to neurons and glia, also thanks to a minimal promoter that restricts its expression in mitotically active cells, rarely present in the brain parenchyma. Collectively, SES produces a significant silencing of a large fraction of the SOX2 transcriptional network, achieving high levels of efficacy in repressing aggressive brain tumors.

In Vivo Methods to Monitor Cardiomyocyte Proliferation

Adult mammalian cardiomyocytes demonstrate scarce cycling and even lower proliferation rates in response to injury. Signals that enhance cardiomyocyte proliferation after injury will be groundbreaking, address unmet clinical needs, and represent new strategies to treat cardiovascular diseases. In vivo methods to monitor cardiomyocyte proliferation are critical to addressing this challenge. Fortunately, advances in transgenic approaches provide sophisticated techniques to quantify cardiomyocyte cycling and proliferation.

Visualization of endogenous p27 and Ki67 reveals the importance of a c-Myc-driven metabolic switch in promoting survival of quiescent cancer cells

Rationale: Recurrent and metastatic cancers often undergo a period of dormancy, which is closely associated with cellular quiescence, a state whereby cells exit the cell cycle and are reversibly arrested in G0 phase. Curative cancer treatment thus requires therapies that either sustain the dormant state of quiescent cancer cells, or preferentially, eliminate them. However, the mechanisms responsible for the survival of quiescent cancer cells remain obscure. Methods: Dual genome-editing was carried out using a CRISPR/Cas9-based system to label endogenous p27 and Ki67 with the green and red fluorescent proteins EGFP and mCherry, respectively, in melanoma cells. Analysis of transcriptomes of isolated EGFP-p27^highmCherry-Ki67^low quiescent cells was conducted at bulk and single cell levels using RNA-sequencing. The extracellular acidification rate and oxygen consumption rate were measured to define metabolic phenotypes. SiRNA and inducible shRNA knockdown, chromatin immunoprecipitation and luciferase reporter assays were employed to elucidate mechanisms of the metabolic switch in quiescent cells. Results: Dual labelling of endogenous p27 and Ki67 with differentiable fluorescent probes allowed for visualization, isolation, and analysis of viable p27^highKi67^low quiescent cells. Paradoxically, the proto-oncoprotein c-Myc, which commonly drives malignant cell cycle progression, was expressed at relatively high levels in p27^highKi67^low quiescent cells and supported their survival through promoting mitochondrial oxidative phosphorylation (OXPHOS). In this context, c-Myc selectively transactivated genes encoding OXPHOS enzymes, including subunits of isocitric dehydrogenase 3 (IDH3), whereas its binding to cell cycle progression gene promoters was decreased in quiescent cells. Silencing of c-Myc or the catalytic subunit of IDH3, IDH3α, preferentially killed quiescent cells, recapitulating the effect of treatment with OXPHOS inhibitors. Conclusion: These results establish a rigorous experimental system for investigating cellular quiescence, uncover the high selectivity of c-Myc in activating OXPHOS genes in quiescent cells, and propose OXPHOS targeting as a potential therapeutic avenue to counter cancer cells in quiescence.

Modeling the Dynamics of T-Cell Development in the Thymus

The thymus hosts the development of a specific type of adaptive immune cells called T cells. T cells orchestrate the adaptive immune response through recognition of antigen by the highly variable T-cell receptor (TCR). T-cell development is a tightly coordinated process comprising lineage commitment, somatic recombination of Tcr gene loci and selection for functional, but non-self-reactive TCRs, all interspersed with massive proliferation and cell death. Thus, the thymus produces a pool of T cells throughout life capable of responding to virtually any exogenous attack while preserving the body through self-tolerance. The thymus has been of considerable interest to both immunologists and theoretical biologists due to its multi-scale quantitative properties, bridging molecular binding, population dynamics and polyclonal repertoire specificity. Here, we review experimental strategies aimed at revealing quantitative and dynamic properties of T-cell development and how they have been implemented in mathematical modeling strategies that were reported to help understand the flexible dynamics of the highly dividing and dying thymic cell populations. Furthermore, we summarize the current challenges to estimating in vivo cellular dynamics and to reaching a next-generation multi-scale picture of T-cell development.

Loss of Endogenously Cycling Adult Cardiomyocytes Worsens Myocardial Function

RATIONALE

Endogenously cycling adult cardiomyocytes increase after myocardial infarction (MI) but remain scarce and are generally thought not to contribute to myocardial function. However, this broadly held assumption has not been tested, mainly because of the lack of transgenic reporters that restrict Cre expression to adult cardiomyocytes that reenter the cell cycle.

OBJECTIVE

We created and validated a new transgenic mouse, αMHC (alpha myosin heavy chain)-MerDreMer-Ki67p-RoxedCre (denoted αDKRC [cardiomyocyte-specific αMHC-MerDreMer-Ki67p-RoxedCre]) that restricts Cre expression to cycling adult cardiomyocytes and uniquely integrates spatial and temporal adult cardiomyocyte cycling events based on the DNA specificities of orthologous Dre and Cre recombinases. We then created αDKRC::DTA mice that expressed an inducible diphtheria toxin in adult cycling cardiomyocytes and examined the effects of ablating these endogenously cycling cardiomyocytes on myocardial function after ischemic-reperfusion (I/R) MI.

METHODS AND RESULTS

A tandem αDKRC transgene was designed, validated in cultured cells, and used to make transgenic mice. The αDKRC transgene integrated between MYH6 and MYH7 and did not disrupt expression of the surrounding genes. Compared with controls, αDKRC::RLTG (Rox-Lox-tdTomato-eGFP) mice treated with Tamoxifen expressed tdTomato+ in cardiomyocytes with rare Bromodeoxyuridine+, eGFP+ cardiomyocytes, consistent with reentry of the cell cycle. We then pretreated αDKRC::RLTG mice with Tamoxifen to activate the reporter before sham or reperfusion (I/R) MI surgeries. Compared with Sham surgery, the I/R MI group had increased single and paired eGFP+ (enhanced green fluorescent protein)+ cardiomyocytes predominantly in the border zones (5.8±0.5 versus 3.3±0.3 cardiomyocytes per 10-micron section, N=8-9 mice per group, n=16-24 sections per mouse), indicative of cycled cardiomyocytes. The single to paired eGFP+ cardiomyocyte ratio was ≈9 to 1 (5.2±0.4 single versus 0.6±0.2 paired cardiomyocytes) in the I/R MI group after MI, suggesting that cycling cardiomyocytes were more likely to undergo polyploidy than replication. The ablation of endogenously cycling adult cardiomyocytes in αDKRC::DTA (diphtheria) mice caused progressive worsening left ventricular chamber size and function after I/R MI, compared with controls.

CONCLUSIONS

Although scarce, endogenously cycling adult cardiomyocytes contribute to myocardial function after injury, suggesting that these cells may be physiologically relevant.

Methods and sensors for functional genomic studies of cell-cycle transitions in single cells

Much of our understanding of the regulatory mechanisms governing the cell cycle in mammals has relied heavily on methods that measure the aggregate state of a population of cells. While instrumental in shaping our current understanding of cell proliferation, these approaches mask the genetic signatures of rare subpopulations such as quiescent (G₀) and very slowly dividing (SD) cells. Results described in this study and those of others using single-cell analysis reveal that even in clonally derived immortalized cancer cells, ∼1-5% of cells can exhibit G₀ and SD phenotypes. Therefore to enable the study of these rare cell phenotypes we established an integrated molecular, computational, and imaging approach to track, isolate, and genetically perturb single cells as they proliferate. A genetically encoded cell-cycle reporter (K67_p-FUCCI) was used to track single cells as they traversed the cell cycle. A set of R-scripts were written to quantify K67_p-FUCCI over time. To enable the further study G₀ and SD phenotypes, we retrofitted a live cell imaging system with a micromanipulator to enable single-cell targeting for functional validation studies. Single-cell analysis revealed HT1080 and MCF7 cells had a doubling time of ∼24 and ∼48 h, respectively, with high duration variability in G₁ and G₂ phases. Direct single-cell microinjection of mRNA encoding (GFP) achieves detectable GFP fluorescence within ∼5 h in both cell types. These findings coupled with the possibility of targeting several hundreds of single cells improves throughput and sensitivity over conventional methods to study rare cell subpopulations.

Crescent-Like Lesions as an Early Signature of Nephropathy in a Rat Model of Prediabetes Induced by a Hypercaloric Diet

Diabetic nephropathy (DN) is a major microvascular complication of diabetes. Obesity and hyperlipidemia, fueled by unhealthy food habits, are risk factors to glomerular filtration rate (GFR) decline and DN progression. Several studies recommend that diabetic patients should be screened early (in prediabetes) for kidney disease, in order to prevent advanced stages, for whom the current interventions are clearly inefficient. This ambition greatly depends on the existence of accurate early biomarkers and novel molecular targets, which only may arise with a more thorough knowledge of disease pathophysiology. We used a rat model of prediabetes induced by 23 weeks of high-sugar/high-fat (HSuHF) diet to characterize the phenotype of early renal dysfunction and injury. When compared with the control animals, HSuHF-treated rats displayed a metabolic phenotype compatible with obese prediabetes, displaying impaired glucose tolerance and insulin sensitivity, along with hypertriglyceridemia, and lipid peroxidation. Despite unchanged creatinine levels, the prediabetic animals presented glomerular crescent-like lesions, accompanied by increased kidney Oil-Red-O staining, triglycerides content and mRNA expression of IL-6 and iNOS. This model of HSuHF-induced prediabetes can be a useful tool to study early features of DN, namely crescent-like lesions, an early signature that deserves in-depth elucidation.

A novel exopolysaccharide from marine bacterium Pantoea sp. YU16-S3 accelerates cutaneous wound healing through Wnt/β-catenin pathway

Natural polysaccharides with versatile properties are the potential candidates for wound healing applications. In this study, an exopolysaccharide, EPS-S3, isolated from a marine bacteria Pantoea sp. YU16-S3 was evaluated for its wound-healing abilities by studying the key molecular mechanisms in vitro and in vivo. Basic characterisation showed EPS-S3 as a heteropolysaccharide with glucose, galactose, N-acetyl galactosamine and glucosamine. The molecular weight of EPS-S3 was estimated to be 1.75 × 10⁵ Da. It showed thermal stability up to 200 °C and shear-thickening non-Newtonian behaviour. It was biocompatible with dermal fibroblasts and keratinocytes and showed cell adhesion and cell proliferation properties. EPS-S3 facilitated cell migration in fibroblasts, induced rapid transition of cell cycle phases and also activated macrophages. In vivo experiments in rats showed the re-epithelialization of injured tissue with increased expression of HB-EGF, FGF, E-cadherin and β-catenin in EPS-S3 treatment. The results indicate that EPS-S3 modulates healing process through Wnt/β-catenin pathway due to its unique characteristics. In conclusion, EPS-S3 biosynthesized by the marine bacterium is a potential biomolecule for cutaneous wound healing applications.

Transit amplifying cells coordinate mouse incisor mesenchymal stem cell activation

Stem cells (SCs) receive inductive cues from the surrounding microenvironment and cells. Limited molecular evidence has connected tissue-specific mesenchymal stem cells (MSCs) with mesenchymal transit amplifying cells (MTACs). Using mouse incisor as the model, we discover a population of MSCs neibouring to the MTACs and epithelial SCs. With Notch signaling as the key regulator, we disclose molecular proof and lineage tracing evidence showing the distinct MSCs contribute to incisor MTACs and the other mesenchymal cell lineages. MTACs can feedback and regulate the homeostasis and activation of CL-MSCs through Delta-like 1 homolog (Dlk1), which balances MSCs-MTACs number and the lineage differentiation. Dlk1's function on SCs priming and self-renewal depends on its biological forms and its gene expression is under dynamic epigenetic control. Our findings can be validated in clinical samples and applied to accelerate tooth wound healing, providing an intriguing insight of how to direct SCs towards tissue regeneration.

Aberrant expression of genes associated with stemness and cancer in endometria and endometrioma in a subset of women with endometriosis

STUDY QUESTION

Is there molecular evidence for a link between endometriosis and endometriosis-associated ovarian cancers (EAOC)?

STUDY ANSWER

We identified aberrant gene expression signatures associated with malignant transformation in a small subgroup of women with ovarian endometriosis.

WHAT IS KNOWN ALREADY

Epidemiological studies have shown an increased risk of EAOC in women with ovarian endometriosis. However, the cellular and molecular changes leading to EAOC are largely unexplored.

STUDY DESIGN, SIZE, DURATION

CD73+CD90+CD105+ multipotent stem cells/progenitors (SC cohort) were isolated from endometrium (n = 18) and endometrioma (n = 11) of endometriosis patients as well as from the endometrium of healthy women (n = 14). Extensive phenotypic and functional analyses were performed in vitro on expanded multipotent stem cells/progenitors to confirm their altered characteristics. Aberrant gene signatures were also validated in paired-endometrium and -endometrioma tissue samples from another cohort (Tissue cohort, n = 19) of endometriosis patients.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Paired-endometrial and -endometriotic biopsies were obtained from women with endometriosis (ASRM stage III-IV) undergoing laparoscopic surgery. Control endometria were obtained from healthy volunteers. Isolated CD73+CD90+CD105+ SC were evaluated for the presence of known endometrial surface markers, colony forming efficiency, multi-lineage differentiation, cell cycle distribution and 3D-spheroid formation capacity. Targeted RT-PCR arrays, along with hierarchical and multivariate clustering tools, were used to determine both intergroup and intragroup gene expression variability for stem cell and cancer-associated markers, in both SC+ and tissue cohorts.

MAIN RESULTS AND THE ROLE OF CHANCE

Isolated and expanded SC+ from both control and patient groups showed significantly higher surface expression of W5C5+, clonal expansion and 3D-spheroid formation capacity (P < 0.05) compared with SC-. The SC+ cells also undergo mesenchymal lineage differentiation, unlike SC-. Gene expression from paired-endometriosis samples showed significant downregulation of PTEN, ARID1A and TNFα (P < 0.05) in endometrioma compared with paired-endometrium SC+ samples. Hierarchical and multivariate clustering from both SC+ and tissue cohorts together identified 4 out of 30 endometrioma samples with aberrant expression of stem cell and cancer-associated genes, such as KIT, HIF2α and E-cadherin, altered expression ratio of ER-β/ER-α and downregulation of tumour suppressor genes (PTEN and ARID1A). Thus, we speculate that above changes may be potentially relevant to the development of EAOC.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASON FOR CAUTION

As the reported frequency of EAOC is very low, we did not have access to those samples in our study. Moreover, by adopting a targeted gene array approach, we might have missed several other potentially-relevant genes associated with EAOC pathogenesis. The above panel of markers should be further validated in archived tissue samples from women with endometriosis who later in life developed EAOC.

WIDER IMPLICATIONS OF THE FINDINGS

Knowledge gained from this study, with further confirmation on EAOC cases, may help in developing screening methods to identify women with increased risk of EAOC.

STUDY FUNDING/COMPETING INTEREST(S)

The study is funded by the Swedish Research Council (2012-2844), a joint grant from Stockholm County and Karolinska Institutet (ALF), RGD network at Karolinska Institutet, Karolinska Institutet for doctoral education (KID), Estonian Ministry of Education and Research (IUT34-16), Enterprise Estonia (EU48695), Horizon 2020 innovation program (WIDENLIFE, 692065), European Union's FP7 Marie Curie Industry-Academia Partnerships and Pathways funding (IAPP, SARM, EU324509) and MSCA-RISE-2015 project MOMENDO (691058). All authors have no competing interest.

Proteomic analysis of the effects of cell culture density on the metastasis of breast cancer cells

Cancer cell progression and proliferation increase cell density, resulting in changes to the tumour site, including the microenvironment. What is not known is if increased cell density influences the aggressiveness of cancer cells, especially their proliferation, migration, and invasion capabilities. In this study, we found that dense cell culture enhances the aggressiveness of the metastatic cancer cell lines, 4T1 and ZR-75-30, by increasing their proliferation, migration, and invasion capabilities. However, a less metastatic cell line, MCF-7, did not show an increase in aggressiveness, following dense cell culture conditions. We conducted a differential proteomic analysis on 4T1 cells cultured under dense or sparse conditions and identified an increase in expression for proteins involved in migration, including focal adhesion, cytoskeletal reorganization, and transendothelial migration. In contrast, 4T1 cells grown under sparse conditions had higher expression levels for proteins involved in metabolism, including lipid and phospholipid binding, lipid and cholesterol transporter activity, and protein binding. These results suggest that the high-density tumour microenvironment can cause a change in cellular behaviour, leading towards more aggressive cancers. SIGNIFICANCE OF THE STUDY: Metastasis of cancer cells is an obstacle to the clinical treatment of cancer. We found that dense cultures made metastatic cancer cells more potent in terms of proliferation, migration, and invasion. The proteomic and bioinformatic analyses provided some valuable clues for further intensive studies about the effects of cell density on cancer cell aggressiveness, which were associated with events such as pre-mRNA splicing and RNA transport, focal adhesion and cytoskeleton reorganization, ribosome biogenesis, and transendothelial migration, or associated with proteins, such as JAM-1 and S100A11. This investigation gives us new perspectives to investigate the metastasis mechanisms related to the microenvironment of tumour sites.

Prominin-1 controls stem cell activation by orchestrating ciliary dynamics

Proper temporal and spatial activation of stem cells relies on highly coordinated cell signaling. The primary cilium is the sensory organelle that is responsible for transmitting extracellular signals into a cell. Primary cilium size, architecture, and assembly-disassembly dynamics are under rigid cell cycle-dependent control. Using mouse incisor tooth epithelia as a model, we show that ciliary dynamics in stem cells require the proper functions of a cholesterol-binding membrane glycoprotein, Prominin-1 (Prom1/CD133), which controls sequential recruitment of ciliary membrane components, histone deacetylase, and transcription factors. Nuclear translocation of Prom1 and these molecules is particularly evident in transit amplifying cells, the immediate derivatives of stem cells. The absence of Prom1 impairs ciliary dynamics and abolishes the growth stimulation effects of sonic hedgehog (SHH) treatment, resulting in the disruption of stem cell quiescence maintenance and activation. We propose that Prom1 is a key regulator ensuring appropriate response of stem cells to extracellular signals, with important implications for development, regeneration, and diseases.

Embryonic macrophages and microglia ablation alter the development of dorsal root ganglion sensory neurons in mouse embryos

Microglia are known to regulate several aspects of the development of the central nervous system. When microglia colonize the spinal cord, from E11.5 in the mouse embryo, they interact with growing central axons of dorsal root ganglion sensory neurons (SNs), which suggests that they may have some functions in SN development. To address this issue, we analyzed the effects of embryonic macrophage ablation on the early development of SNs using mouse embryo lacking embryonic macrophages (PU.1 knock-out mice) and immune cell ablation. We discovered that, in addition to microglia, embryonic macrophages contact tropomyosin receptor kinase (Trk) C⁺ SN, TrkB⁺ SN, and TrkA⁺ SN peripheral neurites from E11.5. Deprivation of immune cells resulted in an initial reduction of TrkC⁺ SN and TrkB⁺ SN populations at E11.5 that was unlikely to be related to an alteration in their developmental cell death (DCD), followed by a transitory increase in their number at E12.5. It also resulted in a reduction of TrkA⁺ SN number during the developmental period analyzed (E11.5-E15.5), although we did not observe any change in their DCD. Proliferation of cells negative for brain fatty acid-binding protein (BFABP^- ), which likely correspond to neuronal progenitors, was increased at E11.5, while their proliferation was decreased at E12.5, which could partly explain the alterations of SN subtype production observed from E11.5. In addition, we observed alterations in the proliferation of glial cell progenitors (BFABP⁺ cells) in the absence of embryonic macrophages. Our data indicate that embryonic macrophages and microglia ablation alter the development of SNs.

Ribavirin as a potential therapeutic for atypical teratoid/rhabdoid tumors

Atypical teratoid/rhabdoid tumors (AT/RT) are highly aggressive, malignant tumors and are the most common malignant brain tumor in children under 6 months of age. Currently, there is no standard treatment for AT/RT. Recent studies have reported potential anti-tumoral properties of ribavirin, a guanosine analog and anti-viral molecule approved by the Food and Drug Administration for treatment of hepatitis C. We previously demonstrated that ribavirin inhibited glioma cell growth in vitro and in vivo. Based on these results and the fact that no pre-clinical model of ribavirin in AT/RT exists, we decided to investigate the effect of ribavirin on several human AT/RT cell lines (BT12, BT16, and BT37) both in vitro and in vivo. We provide evidence that ribavirin has a significant impact on AT/RT cell growth and increases cell cycle arrest and cell death, potentially through modulation of the eIF4E and/or EZH2 pathways. Interestingly, using scratch wound and transwell Boyden chamber assays, we observed that ribavirin also impairs AT/RT cell migration, invasion, and adhesion. Finally, we demonstrate that ribavirin significantly improves the survival of mice orthotopically implanted with BT12 cells. Our work establishes that ribavirin is effective against AT/RT by decreasing tumoral cell growth and dissemination and could represent a new therapeutic option for children with this deadly disease.

Characterization and functional analysis of a slow-cycling subpopulation in colorectal cancer enriched by cell cycle inducer combined chemotherapy

The concept of cancer stem cells has been proposed in various malignancies including colorectal cancer. Recent studies show direct evidence for quiescence slow-cycling cells playing a role in cancer stem cells. There exists an urgent need to isolate and better characterize these slow-cycling cells. In this study, we developed a new model to enrich slow-cycling tumor cells using cell-cycle inducer combined with cell cycle-dependent chemotherapy in vitro and in vivo. Our results show that Short-term exposure of colorectal cancer cells to chemotherapy combined with cell-cycle inducer enriches for a cell-cycle quiescent tumor cell population. Specifically, these slow-cycling tumor cells exhibit increased chemotherapy resistance in vitro and tumorigenicity in vivo. Notably, these cells are stem-cell like and participate in metastatic dormancy. Further exploration indicates that slow-cycling colorectal cancer cells in our model are less sensitive to cytokine-induced-killer cell mediated cytotoxic killing in vivo and in vitro. Collectively, our cell cycle inducer combined chemotherapy exposure model enriches for a slow-cycling, dormant, chemo-resistant tumor cell sub-population that are resistant to cytokine induced killer cell based immunotherapy. Studying unique signaling pathways in dormant tumor cells enriched by cell cycle inducer combined chemotherapy treatment is expected to identify novel therapeutic targets for preventing tumor recurrence.

Elimination of proliferating cells from CNS grafts using a Ki67 promoter-driven thymidine kinase

Pluripotent stem cell (PSC)-based cell therapy is an attractive concept for neurodegenerative diseases, but can lead to tumor formation. This is particularly relevant as proliferating neural precursors rather than postmitotic mature neurons need to be transplanted. Thus, safety mechanisms to eliminate proliferating cells are needed. Here, we propose a suicide gene approach, based on cell cycle-dependent promoter Ki67-driven expression of herpes simplex virus thymidine kinase (HSV-TK). We generated a PSC line expressing this construct and induced neural differentiation. In vitro, proliferating PSC and early neural precursor cells (NPC) were killed by exposure to ganciclovir. In vivo, transplantation of PSC led to tumor formation, which was prevented by early ganciclovir treatment. Transplanted NPC did not lead to tumor formation and their survival and neural maturation were not affected by ganciclovir. In conclusion, the cell cycle promoter-driven suicide gene approach described in this study allows killing of proliferating undifferentiated precursor cells without expression of the suicide gene in mature neurons. This approach could also be of use for other stem cell-based therapies where the final target consists of postmitotic cells.

Assessment of lymphocyte proliferation for diagnostic purpose: Comparison of CFSE staining, Ki-67 expression and 3H-thymidine incorporation

The capability of lymphocytes to respond to antigenic or mitogenic stimulation is an important feature in the diagnosis of various immunodeficiencies and immune disorders. We used large cohorts of both immune compromised patients and healthy controls to measure lymphocyte proliferations by means of three methods: CFSE staining, Ki-67 expression and ³H-thymidine incorporation. The advantages and disadvantages of each method was then evaluated for use in routine clinical diagnostic. The statistical analysis was performed between the outcomes and the correlation between all three methods was computed. CFSE and Ki-67 assay correlated well with the r=0.767, correlation between Ki-67 expression and ³H-thymidine incorporation was 0.546 and correlation between CFSE staining and ³H-thymidine incorporation was 0.337. The differences between these three methods concerning complexity, sensitivity and reliability as well as the financial aspects are discussed hereafter. CFSE and its analogues provide the cheapest and reasonable choice for measuring lymphocyte proliferation, while Ki-67 represents a more expensive, but more sensitive and robust method. The original ³H-thymidine assay does not bring any advantages and cannot compare to the competition presented by modern flow cytometric methods available today.

Immunohistochemical expression of K6, K8, K16, K17, K19, maspin, syndecan-1 (CD138), α-SMA, and Ki-67 in ameloblastoma and ameloblastic carcinoma: diagnostic and prognostic correlations

OBJECTIVE

To identify cutoff values of markers that correlate with the histopathologic diagnosis of ameloblastic carcinoma (AC) and/or the increased recurrence potential of ameloblastoma (AB).

STUDY DESIGN

Immunohistochemical expression (IHCE) of 9 selected markers were investigated in 18 non-recurrent ameloblastomas (NRABs), 6 recurrent ameloblastomas (RABs), and 5 ACs.

RESULTS

No significant difference in IHCE of K6, K8, K16, K17, K18, K19, maspin, or syndecan-1 was observed among study groups. α Smooth muscle actin (α-SMA)-positive area in central epithelial cells significantly differentiated between AB and AC (P = .017; t -test). Ki-67 score significantly differentiated between AB and AC (P < .005; t -test) and between AC and RAB (P = .015; ANOVA/post hoc).

CONCLUSIONS

Ki-67 score of 75 cells/HPF (ROC curve) is a potential indicator of AC. Clinical recurrence of AB may be predicted by α-SMA expression pattern. Syndecan-1 and α-SMA may indicate a higher aggressive potential of AB when expressed in the stroma.

Cytometry in the brain: studying differentiation to diagnostic applications in brain disease and regeneration therapy

During brain development, a population of uniform embryonic cells migrates and differentiates into a large number of neural phenotypes - origin of the enormous complexity of the adult nervous system. Processes of cell proliferation, differentiation and programmed death of no longer required cells, do not occur only during embryogenesis, but are also maintained during adulthood and are affected in neurodegenerative and neuropsychiatric disease states. As neurogenesis is an endogenous response to brain injury, visible as proliferation (of to this moment silent stem or progenitor cells), its further stimulation can present a treatment strategy in addition to stem cell transfer for cell regeneration therapy. Concise techniques for studying such events in vitro and in vivo permit understanding of underlying mechanisms. Detection of subtle physiological alterations in brain cell proliferation and neurogenesis can be explored, that occur during environmental stimulation, exercise and ageing. Here, we have collected achievements in the field of basic research on applications of cytometry, including automated imaging for quantification of morphological or fluorescence-based parameters in cell cultures, towards imaging of three-dimensional brain architecture together with DNA content and proliferation data. Multi-parameter and more recently in vivo flow cytometry procedures, have been developed for quantification of phenotypic diversity and cell processes that occur during brain development as well as in adulthood, with importance for therapeutic approaches.

A novel cell-cycle-indicator, mVenus-p27K-, identifies quiescent cells and visualizes G0-G1 transition

The quiescent (G0) phase of the cell cycle is the reversible phase from which the cells exit from the cell cycle. Due to the difficulty of defining the G0 phase, quiescent cells have not been well characterized. In this study, a fusion protein consisting of mVenus and a defective mutant of CDK inhibitor, p27 (p27K⁻) was shown to be able to identify and isolate a population of quiescent cells and to effectively visualize the G0 to G1 transition. By comparing the expression profiles of the G0 and G1 cells defined by mVenus-p27K⁻, we have identified molecular features of quiescent cells. Quiescence is also an important feature of many types of stem cells, and mVenus-p27K⁻-transgenic mice enabled the detection of the quiescent cells with muscle stem cell markers in muscle in vivo. The mVenus-p27K⁻ probe could be useful in investigating stem cells as well as quiescent cells.

Single-cell and subcellular pharmacokinetic imaging allows insight into drug action in vivo

Pharmacokinetic analysis at the organ level provides insight into how drugs distribute throughout the body, but cannot explain how drugs work at the cellular level. Here we demonstrate in vivo single-cell pharmacokinetic imaging of PARP-1 inhibitors and model drug behaviour under varying conditions. We visualize intracellular kinetics of the PARP-1 inhibitor distribution in real time, showing that PARP-1 inhibitors reach their cellular target compartment, the nucleus, within minutes in vivo both in cancer and normal cells in various cancer models. We also use these data to validate predictive finite element modelling. Our theoretical and experimental data indicate that tumour cells are exposed to sufficiently high PARP-1 inhibitor concentrations in vivo and suggest that drug inefficiency is likely related to proteomic heterogeneity or insensitivity of cancer cells to DNA-repair inhibition. This suggests that single-cell pharmacokinetic imaging and derived modelling improve our understanding of drug action at single-cell resolution in vivo.

Classic "broken cell" techniques and newer live cell methods for cell cycle assessment

Many common, important diseases are either caused or exacerbated by hyperactivation (e.g., cancer) or inactivation (e.g., heart failure) of the cell division cycle. A better understanding of the cell cycle is critical for interpreting numerous types of physiological changes in cells. Moreover, new insights into how to control it will facilitate new therapeutics for a variety of diseases and new avenues in regenerative medicine. The progression of cells through the four main phases of their division cycle [G(0)/G(1), S (DNA synthesis), G(2), and M (mitosis)] is a highly conserved process orchestrated by several pathways (e.g., transcription, phosphorylation, nuclear import/export, and protein ubiquitination) that coordinate a core cell cycle pathway. This core pathway can also receive inputs that are cell type and cell niche dependent. "Broken cell" methods (e.g., use of labeled nucleotide analogs) to assess for cell cycle activity have revealed important insights regarding the cell cycle but lack the ability to assess living cells in real time (longitudinal studies) and with single-cell resolution. Moreover, such methods often require cell synchronization, which can perturb the pathway under study. Live cell cycle sensors can be used at single-cell resolution in living cells, intact tissue, and whole animals. Use of these more recently available sensors has the potential to reveal physiologically relevant insights regarding the normal and perturbed cell division cycle.

The protective role of natural phytoalexin resveratrol on inflammation, fibrosis and regeneration in cholestatic liver injury

Liver injuries can trigger a cascade of inflammatory responses and as a result, initiate the process of hepatic regeneration and fibrogenesis. Resveratrol (RSV) has multiple health-promoting benefits. This study evaluated the potential protective effects and mechanism of RSV as related to cholestatic liver injury. RSV was given (4 mg/kg/day, i.p.) for either 3 days or 7 days after bile duct ligation (BDL) injury. RSV significantly reduced serum ALT, AST but not T-bil on Day 3. At this early stage of injury, RSV significantly reduced TNF-α and IL-6 mRNA and decreased the number of Kupffer cells (CD68(+) ) recruited in the injured liver. RSV decreased hepatic fibrosis and reduced collagen Iα1 and TIMP-1 mRNA on Day 7. At the later stages of injury, RSV increased the number of Ki67(+) hepatocytes indicating that RSV promoted hepatocyte proliferation. Additionally, it resulted in decreased expression of 4-hydroxynonenal and increased expression of the hepatocyte growth factor protein and mRNA in the RSV-treated BDL group. Meanwhile, RSV reduced the mortality rate of BDL mice. In conclusion, RSV attenuated inflammation and reduced Kupffer cells activation. RSV decreased fibrosis and promoted hepatocyte regeneration, which increased the survival of BDL mice. RSV was beneficial for the treatment of cholestatic liver injury.