Expression of the repressor element-1 silencing transcription factor (REST) is regulated by IGF-I and PKC in human neuroblastoma cells

The repressor element 1-silencing transcription factor (REST) was first identified as a protein that binds to a 21-bp DNA sequence element (known as repressor element 1 (RE1)) resulting in transcriptional repression of the neural-specific genes [Chong et al., 1995; Schoenherr and Anderson, 1995]. The original proposed role for REST was that of a factor responsible for restricting neuronal gene expression to the nervous system by silencing expression of these genes in non-neuronal cells. Although it was initially thought to repress neuronal genes in non-neuronal cells, the role of REST is complex and tissue dependent. In this study I investigated any role played by REST in the induction and patterning of differentiation of SH-SY5Y human neuroblastoma cells exposed to IGF-I. and phorbol 12- myristate 13-acetate (PMA) To down-regulate REST expression we developed an antisense (AS) strategy based on the use of phosphorothioate oligonucleotides (ODNs). In order to evaluate REST mRNA levels, we developed a real-time PCR technique and REST protein levels were evaluated by western blotting. Results showed that nuclear REST is increased in SH-SY5Y neuroblastoma cells cultured in SFM and exposed to IGF-I for 2-days and it then declines in 5-day-treated cells concomitant with a progressive neurite extension. Also the phorbol ester PMA was able to increase nuclear REST levels after 3-days treatment concomitant to neuronal differentiation of neuroblastoma cells, whereas, at later stages, it is down-regulated. Supporting these data, the exposure to PKC inhibitors (GF10923X and Gö6976) and PMA (16nM) reverted the effects observed with PMA alone. REST levels were related to morphological differentiation, expression of growth coneassociated protein 43 (GAP-43; a gene not regulated by REST) and of synapsin I and βIII tubulin (genes regulated by REST), proteins involved in the early stage of neuronal development. We observed that differentiation of SH-SY5Y cells by IGF-I and PMA was accompanied by a significant increase of these neuronal markers, an effect that was concomitant with REST decrease. In order to relate the decreased REST expression with a progressive neurite extension, I investigated any possible involvement of the ubiquitin–proteasome system (UPS), a multienzymatic pathway which degrades polyubiquinated soluble cytoplasmic proteins [Pickart and Cohen, 2004]. For this purpose, SH-SY5Y cells are concomitantly exposed to PMA and the proteasome inhibitor MG132. In SH-SY5Y exposed to PMA and MG 132, we observed an inverse pattern of expression of synapsin I and β- tubulin III, two neuronal differentiation markers regulated by REST. Their cytoplasmic levels are reduced when compared to cells exposed to PMA alone, as a consequence of the increase of REST expression by proteasome inhibitor. The majority of proteasome substrates identified to date are marked for degradation by polyubiquitinylation; however, exceptions to this principle, are well documented [Hoyt and Coffino, 2004]. Interestingly, REST degradation seems to be completely ubiquitin-independent. The expression pattern of REST could be consistent with the theory that, during early neuronal differentiation induced by IGF-I and PKC, it may help to repress the expression of several genes not yet required by the differentiation program and then it declines later. Interestingly, the observation that REST expression is progressively reduced in parallel with cell proliferation seems to indicate that the role of this transcription factor could also be related to cell survival or to counteract apotosis events [Lawinger et al., 2000] although, as shown by AS-ODN experiments, it does not seem to be directly involved in cell proliferation. Therefore, the decline of REST expression is a comparatively later event during maturation of neuroroblasts in vitro. Thus, we propose that REST is regulated by growth factors, like IGF-I, and PKC activators in a time-dependent manner: it is elevated during early steps of neural induction and could contribute to down-regulate genes not yet required by the differentiation program while it declines later for the acquisition of neural phenotypes, concomitantly with a progressive neurite extension. This later decline is regulated by the proteasome system activation in an ubiquitin-indipendent way and adds more evidences to the hypothesis that REST down-regulation contributes to differentiation and arrest of proliferation of neuroblastoma cells. Finally, the glycosylation pattern of the REST protein was analysed, moving from the observation that the molecular weight calculated on REST sequence is about 116 kDa but using western blotting this transcription factor appears to have distinct apparent molecular weight (see Table 1.1): this difference could be explained by post-translational modifications of the proteins, like glycosylation. In fact recently, several studies underlined the importance of O-glycosylation in modulating transcriptional silencing, protein phosphorylation, protein degradation by proteasome and protein–protein interactions [Julenius et al., 2005; Zachara and Hart, 2006]. Deglycosilating analysis showed that REST protein in SH-SY5Y and HEK293 cells is Oglycosylated and not N-glycosylated. Moreover, using several combination of deglycosilating enzymes it is possible to hypothesize the presence of Gal-β(1-3)-GalNAc residues on the endogenous REST, while β(1-4)-linked galactose residues may be present on recombinant REST protein expressed in HEK293 cells. However, the O-glycosylation process produces an immense multiplicity of chemical structures and monosaccharides must be sequentially hydrolyzed by a series of exoglycosidase. Further experiments are needed to characterize all the post-translational modification of the transcription factor REST.

Genomic and non genomic effects of elevated concentration of anabolic steroids in human neuronal cells

Nandrolone and other anabolic androgenic steroids (AAS) at elevated concentration can alter the expression and function of neurotransmitter systems and contribute to neuronal cell death. This effect can explain the behavioural changes, drug dependence and neuro degeneration observed in steroid abuser. Nandrolone treatment (10-8M–10-5M) caused a time- and concentration-dependent downregulation of mu opioid receptor (MOPr) transcripts in SH-SY5Y human neuroblastoma cells. This effect was prevented by the androgen receptor (AR) antagonist hydroxyflutamide. Receptor binding assays confirmed a decrease in MOPr of approximately 40% in nandrolonetreated cells. Treatment with actinomycin D (10-5M), a transcription inhibitor, revealed that nandrolone may regulate MOPr mRNA stability. In SH-SY5Y cells transfected with a human MOPr luciferase promoter/reporter construct, nandrolone did not alter the rate of gene transcription. These results suggest that nandrolone may regulate MOPr expression through post-transcriptional mechanisms requiring the AR. Cito-toxicity assays demonstrated a time- and concentration dependent decrease of cells viability in SH-SY5Y cells exposed to steroids (10-6M–10-4M). This toxic effects is independent of activation of AR and sigma-2 receptor. An increased of caspase-3 activity was observed in cells treated with Nandrolone 10-6M for 48h. Collectively, these data support the existence of two cellular mechanisms that might explain the neurological syndromes observed in steroids abuser.

Airway Basal Cell Vascular Endothelial Growth Factor-mediated Cross-Talk Regulates Endothelial Cell Dependent Growth Support of Human Airway Basal Cells

The human airway epithelium is a pseudostratified heterogenous layer comprised of cili-ated, secretory, intermediate and basal cells. As the stem/progenitor population of the airway epi-thelium, airway basal cells differentiate into ciliated and secretory cells to replenish the airway epithelium during physiological turnover and repair. Transcriptome analysis of airway basal cells revealed high expression of vascular endothelial growth factor A (VEGFA), a gene not typically associated with the function of this cell type. Using cultures of primary human airway basal cells, we demonstrate that basal cells express all of the 3 major isoforms of VEGFA (121, 165 and 189) but lack functional expression of the classical VEGFA receptors VEGFR1 and VEGFR2. The VEGFA is actively secreted by basal cells and while it appears to have no direct autocrine function on basal cell growth and proliferation, it functions in a paracrine manner to activate MAPK signaling cascades in endothelium via VEGFR2 dependent signaling pathways. Using a cytokine- and serum-free co-culture system of primary human airway basal cells and human endothelial cells revealed that basal cell secreted VEGFA activated endothelium to ex-press mediators that, in turn, stimulate and support basal cell proliferation and growth. These data demonstrate novel VEGFA mediated cross-talk between airway basal cells and endothe-lium, the purpose of which is to modulate endothelial activation and in turn stimulate and sustain basal cell growth.

Computational modelling of human stem cell-derived cardiomyocytes - Texture descriptors for biological image processing

This thesis investigates two distinct research topics. The main topic (Part I) is the computational modelling of cardiomyocytes derived from human stem cells, both embryonic (hESC-CM) and induced-pluripotent (hiPSC-CM). The aim of this research line lies in developing models of the electrophysiology of hESC-CM and hiPSC-CM in order to integrate the available experimental data and getting in-silico models to be used for studying/making new hypotheses/planning experiments on aspects not fully understood yet, such as the maturation process, the functionality of the Ca2+ hangling or why the hESC-CM/hiPSC-CM action potentials (APs) show some differences with respect to APs from adult cardiomyocytes. Chapter I.1 introduces the main concepts about hESC-CMs/hiPSC-CMs, the cardiac AP, and computational modelling. Chapter I.2 presents the hESC-CM AP model, able to simulate the maturation process through two developmental stages, Early and Late, based on experimental and literature data. Chapter I.3 describes the hiPSC-CM AP model, able to simulate the ventricular-like and atrial-like phenotypes. This model was used to assess which currents are responsible for the differences between the ventricular-like AP and the adult ventricular AP. The secondary topic (Part II) consists in the study of texture descriptors for biological image processing. Chapter II.1 provides an overview on important texture descriptors such as Local Binary Pattern or Local Phase Quantization. Moreover the non-binary coding and the multi-threshold approach are here introduced. Chapter II.2 shows that the non-binary coding and the multi-threshold approach improve the classification performance of cellular/sub-cellular part images, taken from six datasets. Chapter II.3 describes the case study of the classification of indirect immunofluorescence images of HEp2 cells, used for the antinuclear antibody clinical test. Finally the general conclusions are reported.

Complexity of N-Myc transcriptional function in childhood neuroblastoma

Myc is a transcription factor that can activate transcription of several hundreds genes by direct binding to their promoters at specific DNA sequences (E-box). However, recent studies have also shown that it can exert its biological role by repressing transcription. Such studies collectively support a model in which c-Myc-mediated repression occurs through interactions with transcription factors bound to promoter DNA regions but not through direct recognition of typical E-box sequences. Here, we investigated whether N-Myc can also repress gene transcription, and how this is mechanistically achieved. We used human neuroblastoma cells as a model system in that N-MYC amplification/over-expression represents a key prognostic marker of this tumour. By means of transcription profile analyses we could identify at least 5 genes (TRKA, p75NTR, ABCC3, TG2, p21) that are specifically repressed by N-Myc. Through a dual-step-ChIP assay and genetic dissection of gene promoters, we found that N-Myc is physically associated with gene promoters in vivo, in proximity of the transcription start site. N-Myc association with promoters requires interaction with other proteins, such as Sp1 and Miz1 transcription factors. Furthermore, we found that N-Myc may repress gene expression by interfering directly with Sp1 and/or with Miz1 activity (i.e. TRKA, p75NTR, ABCC3, p21) or by recruiting Histone Deacetylase 1 (Hdac1) (i.e. TG2). In vitro analyses show that distinct N-Myc domains can interact with Sp1, Miz1 and Hdac1, supporting the idea that Myc may participate in distinct repression complexes by interacting specifically with diverse proteins. Finally, results show that N-Myc, through repressed genes, affects important cellular functions, such as apoptosis, growth, differentiation and motility. Overall, our results support a model in which N-Myc, like c-Myc, can repress gene transcription by direct interaction with Sp1 and/or Miz1, and provide further lines of evidence on the importance of transcriptional repression by Myc factors in tumour biology.

Rag2-/-;gammac-/- immunodeficient mice, a new preclinical model to study antitumor approaches

Animal models have been relevant to study the molecular mechanisms of cancer and to develop new antitumor agents. Anyway, the huge divergence in mouse and human evolution made difficult the translation of the gained achievements in preclinical mouse based studies. The generation of clinically relevant murine models requires their humanization both concerning the creation of transgenic models and the generation of humanized mice in which to engraft a functional human immune system, and reproduce the physiological effects and molecular mechanisms of growth and metastasization of human tumors. In particular, the availability of genotypically stable immunodepressed mice able to accept tumor injection and allow human tumor growth and metastasization would be important to develop anti-tumor and anti-metastatic strategies. Recently, Rag2-/-;gammac-/- mice, double knockout for genes involved in lymphocyte differentiation, had been developed (CIEA, Central Institute for Experimental Animals, Kawasaki, Japan). Studies of human sarcoma metastasization in Rag2-/-; gammac-/- mice (lacking B, T and NK functionality) revealed their high metastatic efficiency and allowed the expression of human metastatic phenotypes not detectable in the conventionally used nude murine model. In vitro analysis to investigate the molecular mechanisms involved in the specific pattern of human sarcomas metastasization revealed the importance of liver-produced growth and motility factors, in particular the insulin-like growth factors (IGFs). The involvement of this growth factor was then demonstrated in vivo through inhibition of IGF signalling pathway. Due to the high growth and metastatic propensity of tumor cells, Rag2-/-;gammac-/- mice were used as model to investigate the metastatic behavior of rhabdomyosarcoma cells engineered to improve the differentiation. It has been recently shown that this immunodeficient model can be reconstituted with a human immune system through the injection of human cord blood progenitor cells. The work illustrated in this thesis revealed that the injection of different human progenitor cells (CD34+ or CD133+) showed peculiar engraftment and differentiation abilities. Experiments of cell vaccination were performed to investigate the functionality of the engrafted human immune system and the induction of specific human immune responses. Results from such experiments will allow to collect informations about human immune responses activated during cell vaccination and to define the best reconstitution and experimental conditions to create a humanized model in which to study, in a preclinical setting, immunological antitumor strategies.

Functional characterization of Streptococcus pyogenes pili

Group A Streptococcus is a Gram-positive human pathogen able to colonize both upper respiratory tract and skin. GAS is responsible for several acute diseases and autoimmune sequelae that account for half a million deaths worldwide every year (Cunningham et al., 2000). As other bacteria, GAS infections requires the capacity of the pathogen to adhere to host tissues and to form cell aggregates. The ability to persist in distinct host niches like the throat and the skin and to trigger infections is associated with the expression of different GAS virulence factors. GAS pili has been described as important virulence factors encoded by different FCT-operon regions. Based on this information, we decided to study the possible effect of environmental conditions that could regulate the pili expression. In this study we reported the influence of pH environment variations in biofilm formation for strains pertaining to a panel of different GAS FCT-types. The biofilm formation was promoted, excepted in the FCT-1 strains, by a changing in pH from physiological to acidic condition of growth in in vitro biofilm assay. By analyzing the possible association between biofilm formation and pH dependence, we have found that in FCT-2 and FCT-3 strains, the biofilm is promoted by pH reduction leading to an increase of pili expression. These data confirmed a direct link between pH dependent pilus expression and biofilm formation in GAS. As pili are a multi component structure we decided to investigate the functional role of one of its subunits, the AP-1 protein. AP-1 is highly conserved through the different FCT-types and suggests a possible essential role for the pili function. We focused our attention on the AP-1 protein encoded by the FCT-1 strains (M6). In particular this AP-1 protein contains the von Willebrand Factor A (VWFA) domain, which share an homology with the human VWFA domain that has been reported to be involved in adhesion process. We have demonstrated that the AP-1 protein binds to human epithelial cells by its VWFA domain, whereas the biofilm formation is mediated by the N-terminal region of AP-1 protein. Moreover, analyzing the importance of AP-1 in in vivo experiments we found a major capacity of tissue dissemination for the wild-type strain compared to the isogenic AP-1 deletion mutant. Pili have been also reported as potential vaccine candidates against Gram positive bacteria. For these reason we decided to investigate the relationship between cross reaction of sera raised against different GAS and GBS pilin subunits and the presence of a conserved Cna_B domain, in different pilin components. Our idea was to investigate if, using pilus conserved domains, a broad coverage vaccine against streptococcal infection could be possible.

Ruolo delle specie reattive dell'ossigeno e di caveole/raft lipidici nella biosegnalazione in linee cellulari umane

Membrane lipid rafts are detergent-resistant microdomains containing glycosphingolipids, cholesterol and glycosylphosphatidylinositol-linked proteins; they seem to be actively involved in many cellular processes including signal transduction, apoptosis, cell adhesion and migration. Lipid rafts may represent important functional platforms where redox signals are produced and transmitted in response to various agonists or stimuli. In addition, a new concept is emerging that could be used to define the interactions or amplification of both redox signalling and lipid raft-associated signalling. This concept is characterized by redox-mediated feed forward amplification in lipid platforms. It is proposed that lipid rafts are formed in response to various stimuli; for instance, NAD(P)H oxidase (Nox) subunits are aggregated or recruited in these platforms, increasing Nox activity. Superoxide and hydrogen peroxide generation could induce various regulatory activities, such as the induction of glucose transport activity and proliferation in leukaemia cells. The aim of our study is to probe: i) the involvement of lipid rafts in the modulation of the glucose transporter Glut1 in human acute leukemia cells; ii) the involvement of plasma membrane caveolae/lipid rafts in VEGF-mediated redox signaling via Nox activation in human leukemic cells; iii) the role of p66shc, an adaptor protein, in VEGF signaling and ROS production in endothelial cells (ECs); iv) the role of Sindecan-2, a transmembrane heparan sulphate proteoglycan, in VEGF signaling and physiological response in ECs and v) the antioxidant and pro-apoptotic activities of simple dietary phenolic acids, i. e. caffeic, syringic and protocatechuic acids in leukemia cells, characterized by a very high ROS content. Our results suggest that the role played by NAD(P)H oxidase-derived ROS in the regulation of glucose uptake, proliferation and migration of leukaemia and endothelial cells could likely occur through the control of lipid raft-associated signalling.

Pathogenesis of cell toxicity by plant toxins

Ribosome inactivating proteins (RIPs) are a family of plant proteins that depurinate the major rRNA, inhibiting the protein synthesis. RIPs are divided into type 1, single chain proteins with enzymatic activity, and type 2 RIPs (toxic and non-toxic), with the enzymatic chain linked to a binding chain. RIPs have been used alone or as toxic component of immunotoxins for experimental therapy of many diseases. The knowledge of cell death pathway(s) induced by RIPs could be useful for clarifying the mechanisms induced by RIPs and for designing specific immunotherapy. The topic of the current study was (i) the determination of the amino acid sequence of the type 2 RIP stenodactylin. The comparison with other RIPs showed that the A chain is related to other toxic type 2 RIPs. whereas the B chain is more related to the non-toxic type 2 RIPs. This latter result is surprising because stenodactylin is actually the most toxic type 2 RIP known; (ii) the study of the cell death mechanisms induced by stenodactylin in human neuroblastoma cells (NB100). High doses of stenodactylin can activate the effector caspases (perhaps through the DNA damage and/or intrinsic/extrinsic pathways) and also cause ROS generation. Low doses cause a caspase-dependent apoptosis, mainly via extrinsic pathway. Moreover, the activation of caspases precedes the inhibition of protein synthesis; (iii) the investigation of the cell death pathway induced by the non-toxic type 2 RIPs ebulin l and nigrin b. These RIPs demonstrated high enzymatic activity in a cell-free system, but they lack high cytotoxicity. These preliminary studies demonstrate that the cell death mechanism induced by the two non-toxic RIPs is partially caspase-dependent apoptosis, but other mechanisms seem to be involved

Biomolecular studies in Alzheimer’s Disease models: investigations in vitro and in vivo

The Alzheimer’s disease (AD), the most prevalent form of age-related dementia, is a multifactorial and heterogeneous neurodegenerative disease. The molecular mechanisms underlying the pathogenesis of AD are yet largely unknown. However, the etiopathogenesis of AD likely resides in the interaction between genetic and environmental risk factors. Among the different factors that contribute to the pathogenesis of AD, amyloid-beta peptides and the genetic risk factor apoE4 are prominent on the basis of genetic evidence and experimental data. ApoE4 transgenic mice have deficits in spatial learning and memory associated with inflammation and brain atrophy. Evidences suggest that apoE4 is implicated in amyloid-beta accumulation, imbalance of cellular antioxidant system and in apoptotic phenomena. The mechanisms by which apoE4 interacts with other AD risk factors leading to an increased susceptibility to the dementia are still unknown. The aim of this research was to provide new insights into molecular mechanisms of AD neurodegeneration, investigating the effect of amyloid-beta peptides and apoE4 genotype on the modulation of genes and proteins differently involved in cellular processes related to aging and oxidative balance such as PIN1, SIRT1, PSEN1, BDNF, TRX1 and GRX1. In particular, we used human neuroblastoma cells exposed to amyloid-beta or apoE3 and apoE4 proteins at different time-points, and selected brain regions of human apoE3 and apoE4 targeted replacement mice, as in vitro and in vivo models, respectively. All genes and proteins studied in the present investigation are modulated by amyloid-beta and apoE4 in different ways, suggesting their involvement in the neurodegenerative mechanisms underlying the AD. Finally, these proteins might represent novel potential diagnostic and therapeutic targets in AD.

Analisi preclinica di nuove strategie terapeutiche basate sull'inibizione di protein-chinasi nell'osteosarcoma.

Scopo: L’obiettivo del presente programma di studio è stato quello di identificare e validare nuovi possibili bersagli terapeutici per l’osteosarcoma (OS) partendo dall’analisi del chinoma umano. Risultati: L’analisi del profilo di espressione genica ottenuta su 21 campioni clinici di OS ad alto grado di malignità ha permesso di selezionare le seguenti chinasi di possibile rilevanza biologica per l’OS: AURK-A, AURK-B, CDK2, PIK3CA, PLK-1. Le chinasi selezionate sono state validate tramite RNA interference. Successivamente è stata valutata l’efficacia dei relativi inibitori specifici: VX-680 e ZM-447439 inibitori delle Aurora-chinasi, Roscovitina di CDK2 e NMS1 di PLK-1, già inclusi in studi clinici. In termini d’inibizione della crescita cellulare le linee sono risultate maggiomente sensibili ai farmaci VX-680 e NMS1. E’ stata osservata una minor sensibilità ai farmaci VX-680, ZM447439 e NMS1 nelle linee doxorubicina(DX)-resistenti (caratterizzate da elevati livelli di espressione di ABCB1), indicando questi farmaci come potenziali substrati di ABCB1. La Roscovitina, nonostante i valori di IC50 elevati, non sembrerebbe substrato di ABCB1. La validazione preclinica di VX-680 e ZM447439 è stata completata. La forte inibizione della crescita è causata da endoreduplicazione per mancata citodieresi con conseguente formazione di una popolazione iperploide e apoptosi. Inoltre, VX-680 inibisce la motilità e la capacità di formare colonie. Esperimenti di associazione farmacologica mostrano che VX-680 interagisce positivamente con tutti i chemioterapici convenzionali impiegati nel trattamento dell’OS. NMS-1 produce interazioni positive con la DX in linee cellulari DX-resistenti, probabilmente grazie all’effetto revertante esercitato su ABCB1. La Roscovitina produce interazioni positive con CDDP e DX nelle varianti resistenti, effetto probbilmente dovuto al ruolo di CDK2 nei meccanismi di riparo del DNA. Conclusioni: L’analisi in vitro dell’attività degli inibitori ha permesso di identificare VX-680 come nuovo farmaco di potenziale interesse clinico, soprattutto in virtù delle sue interazioni sinergiche con i chemioterapici di uso convenzionale nel trattamento dell’osteosarcoma.

Caratteristiche biologiche e potenziale applicativo delle cellule staminali derivate da membrane fetali

La ricerca sulle cellule staminali apre nuove prospettive per approcci di terapia cellulare. Molta attenzione è concentrata sulle cellule staminali isolate da membrane fetali, per la facilità di recupero del materiale di partenza, le limitate implicazioni etiche e le caratteristiche delle popolazioni di cellule staminali residenti. In particolare a livello dell’epitelio amniotico si concentra una popolazione di cellule (hAECs) con interessanti caratteristiche di staminalità, pluripotenza e immunomodulazione. Restano però una serie di limiti prima di arrivare ad un’applicazione clinica: l’uso di siero di origine animale nei terreni di coltura e le limitate conoscenze legate alla reazione immunitaria in vivo. La prima parte di questo lavoro è focalizzata sulle caratteristiche delle hAECs coltivate in un terreno privo di siero, in confronto a un terreno di coltura classico. Lo studio è concentrato sull’analisi delle caratteristiche biologiche, immunomodulatorie e differenziative delle hAECs. L’interesse verso le caratteristiche immunomodulatorie è legato alla possibilità che l’uso di un terreno serum free riduca il rischio di rigetto dopo trapianto in vivo. La maggior parte degli studi in vivo con cellule isolate da membrane fetali sono stati realizzati con cellule di derivazione umana in trapianti xenogenici, ma poco si sa circa la sopravvivenza di queste cellule in trapianti allogenici, come nel caso di trapianti di cellule di derivazione murina in modelli di topo. La seconda parte dello studio è focalizzata sulla caratterizzazione delle cellule derivate da membrane fetali di topo (mFMSC). Le caratteristiche biologiche, differenziative e immunomodulatorie in vitro e in vivo delle mFMSC sono state confrontate con i fibroblasti embrionali di topo. In particolare è stata analizzata la risposta immunitaria a trapianti di mFMSC nel sistema nervoso centrale (CNS) in modelli murini immunocompetenti.

New DAG-dependent mechanisms modulate cell cycle progression

Through the years, several studies reported the involvement of nuclear lipid signalling as highly connected with cell cycle progression. Indeed, nuclear Phosphatidylinositol-4,5-Biphosphate (PIP2) hydrolisis mediated by Phospholipases C (PLC), which leads to production of the second messengers Diacylglycerol (DAG) and Inositol-1,4,5-Triphosphate (IP3), is a fundamental event for both G1/S and G2/M checkpoints. In particular, we found that nuclear DAG production was mediated by PLCbeta1, enzyme mainly localized in the nucleus of K562 human erythroleukemia cells. This event triggered the activation and nuclear translocation of PKCalpha, which, in turn, resulted able to affect cell cycle via modulation of Cyclin D3 and Cyclin B1, two important enzymes for G1/S transition and G2/M progression respectively.