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Biomedical subjects

Luciano Conti

Publications and source records attributed to Luciano Conti.

13 recordsLinked to original sources
PubMed2006

Adherent neural stem (NS) cells from fetal and adult forebrain.

Stable in vitro propagation of central nervous system (CNS) stem cells would offer expanded opportunities to dissect basic molecular, cellular, and developmental processes and to model neurodegenerative disease. CNS stem cells could also provide a source of material for drug discovery assays and cell replacement therapies. We have recently reported the generation of adherent, symmetrically expandable, neural stem (NS) cell lines derived both from mouse and human embryonic stem cells and from fetal forebrain (Conti L, Pollard SM, Gorba T, Reitano E, Toselli M, Biella G, Sun Y, Sanzone S, Ying QL, Cattaneo E, Smith A. 2005. Niche-independent symmetrical self-renewal of a mammalian tissue stem cell. PLoS Biol 3(9):e283). These NS cells retain neuronal and glial differentiation potential after prolonged passaging and are transplantable. NS cells are likely to comprise the resident stem cell population within heterogeneous neurosphere cultures. Here we demonstrate that similar NS cell cultures can be established from the adult mouse brain. We also characterize the growth factor requirements for NS cell derivation and self-renewal. We discuss our current understanding of the relationship of NS cell lines to physiological progenitor cells of fetal and adult CNS.

Aging↗
PubMed2006

Neural stem cell systems: diversities and properties after transplantation in animal models of diseases.

Currently available effective treatments of the diseased or damaged central nervous system (CNS) are restricted to a limited pharmacological relief of symptoms or those given to avoid further damage. Therefore the search is on for treatments that can restore function in the CNS. During recent years replacement of damaged neurons by cell transplantation is being enthusiastically explored as a potential treatment for many neurodegenerative diseases, stroke and traumatic brain injury. Several references in both scientific journals and popular newspapers concerning different types of cultured stem cells, potentially exploitable to treat pathological conditions of the brain, raise important questions pertinent to the fundamental and realistic differences between grafts of primary neural cells and the transplantation of in vitro expanded neural stem cells (NSCs). Our aim is to review the available information on the grafting of different NSC types into the adult rodent brain, focusing on critical aspects for the development of clinical therapies to replace damaged neurons.

Amyotrophic Lateral Sclerosis↗
PubMed2005

Niche-independent symmetrical self-renewal of a mammalian tissue stem cell.

Pluripotent mouse embryonic stem (ES) cells multiply in simple monoculture by symmetrical divisions. In vivo, however, stem cells are generally thought to depend on specialised cellular microenvironments and to undergo predominantly asymmetric divisions. Ex vivo expansion of pure populations of tissue stem cells has proven elusive. Neural progenitor cells are propagated in combination with differentiating progeny in floating clusters called neurospheres. The proportion of stem cells in neurospheres is low, however, and they cannot be directly observed or interrogated. Here we demonstrate that the complex neurosphere environment is dispensable for stem cell maintenance, and that the combination of fibroblast growth factor 2 (FGF-2) and epidermal growth factor (EGF) is sufficient for derivation and continuous expansion by symmetrical division of pure cultures of neural stem (NS) cells. NS cells were derived first from mouse ES cells. Neural lineage induction was followed by growth factor addition in basal culture media. In the presence of only EGF and FGF-2, resulting NS cells proliferate continuously, are diploid, and clonogenic. After prolonged expansion, they remain able to differentiate efficiently into neurons and astrocytes in vitro and upon transplantation into the adult brain. Colonies generated from single NS cells all produce neurons upon growth factor withdrawal. NS cells uniformly express morphological, cell biological, and molecular features of radial glia, developmental precursors of neurons and glia. Consistent with this profile, adherent NS cell lines can readily be established from foetal mouse brain. Similar NS cells can be generated from human ES cells and human foetal brain. The extrinsic factors EGF plus FGF-2 are sufficient to sustain pure symmetrical self-renewing divisions of NS cells. The resultant cultures constitute the first known example of tissue-specific stem cells that can be propagated without accompanying differentiation. These homogenous cultures will enable delineation of molecular mechanisms that define a tissue-specific stem cell and allow direct comparison with pluripotent ES cells.

Animals↗
PubMed2005

Shc3 affects human high-grade astrocytomas survival.

A selective switch from expression of Shc1 gene to Shc3 occurs with maturation of neuronal precursors into postmitotic neurons. Previous studies showed that in the embryo, Shc1 is maximally expressed in dividing CNS stem cells while it is silenced in mature neurons, where it is replaced by Shc3. Under normal conditions Shc3 is never expressed by glial cells. We now show that in human astrocytomas and glioblastomas, the normal pattern of expression of Shc1/Shc3 is totally subverted, both proteins being present at the same time and in the same cells. Our data indicate that Shc3 is maximally expressed, together with Shc1, in glioblastoma, a highly proliferative tumor with little, if any, indication of neuronal differentiation. In primary cultures of glioblastoma, tumor cells maintain Shc1 expression but downregulate Shc3. Analysis of the phosphorylation status of Shc3 in human glioblastoma tumor samples in vivo indicates that it is tyrosine phosphorylated. Finally, we found that the expression of truncated variants of Shc3 with dominant-negative effects in human high-grade glioma cells that maintain Shc3 expression in vitro leads to a decreased Akt posphorylation and increased apoptosis, thus resulting in impaired survival of the transfected cells. These data suggest that Shc molecules play an important role in glioblastoma cell growth and survival.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Decreased density of peripheral benzodiazepine receptors in psychiatric patients after a suicide attempt.

To date, two main types of benzodiazepine (BDZ) receptors have been identified: one of these is the so-called central receptor which is found mainly in the cortex, limbic areas and cerebellum, and the other is known as the peripheral receptor, which is found in the kidneys, lungs, ovaries, testes, adrenal glands and blood cells, but is present also in the central nervous system (CNS), in particular in glial cells. Although for some time the peripheral BDZ receptor has been considered an acceptor site with no pharmacological activity, recent data have suggested that it may be involved in a variety of actions, such as the response to stress. The presence of these receptors in blood platelets, which are considered a reliable, peripheral mirror of the same structures located in the SNC, prompted us to evaluate them in a group of psychiatric patients after a suicide attempt, as compared with healthy control subjects, by means of the specific binding of 3H-PK 11195. Suicide, with no doubt, may be considered one of the most stressful situations occurring to humans. The results showed the presence of a significant decrease in the density of 3H-PK 11195 binding sites in the patients, as compared with healthy control subjects. This finding may represent a non-specific indicator of a condition of stress, since peripheral BDZ receptors are modulated by stress and hormones, or it may result more from an abnormal metabolism of steroid substances which could play a pivotal role in the development of vulnerability towards suicide.

Adolescent↗
PubMed2005

Controlling neural stem cell division within the adult subventricular zone: an APPealing job.

For years, scientists investigating amyloid precursor protein (APP) have focused on its pathogenetic role in the brains of Alzheimer's disease patients. Now, a study by Caille et al. adds new sites of action and new physiological functions for APP. They show that there are binding sites for secreted N-terminal nonamyloidogenic APP (sAPP) on epidermal growth factor (EGF)-responsive neural stem cells in the subventricular zone of the adult brain, where sAPP acts as an EGF cofactor to stimulate proliferation of these cells. This result opens the hypothesis that changes in the levels of sAPP could influence activity of the neurogenic regions of the adult brain in normal and pathological conditions.

Amyloid Precursor Protein Secretases↗
PubMed2005

The function of the neuronal proteins Shc and huntingtin in stem cells and neurons: pharmacologic exploitation for human brain diseases.

The identification of intracellular molecules and soluble factors that are important for neuronal differentiation and survival are of critical importance for development of therapeutic strategies for brain diseases. First, the activity of these factors/molecules may be enhanced in vivo in the attempt to induce proper neuronal differentiation and integration of the resident stem cells. Second, these factors may be applied ex vivo to increase the recovery of neurons from stem cells. Third, for those intracellular molecules that play crucial roles in neuronal survival, identification of their downstream targets may give us the chance to develop drug screening assays that use these targets for therapeutic purposes. In recent years, it has become evident that intracellular signaling processes are critical mediators of the responses of neural stem cells and neurons to growth factors. Analysis of the mechanisms of signal transduction has led to the striking finding that a handful of conserved signaling pathways appear to be used in different combinations to specify a wide variety of tissues or cells. This review will focus on the mechanisms by which specific molecules control the transition from proliferation to differentiation of neural progenitor cells and the subsequent survival of postmitotic neurons; it also discusses how this knowledge may be exploited to increase the potential efficacy of stem cell replacement in the damaged brain.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Neural stem and progenitor cells: choosing the right Shc.

Neural stem cell (NSCs) are self-renewing, multipotent cells able to generate neurons, astrocytes and oligodendrocytes. Since their identification, these properties have made NSCs an attractive subject for therapeutic applications to the damaged brain. In this context, understanding the mechanisms and the molecules regulating their biological properties is important and it is focused to gain control over their proliferative and differentiative potential. Here we will discuss values and unsolved aspects of the system and the employment of potentially key molecular targets for proper control of NSCs fate.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Huntingtin interacts with REST/NRSF to modulate the transcription of NRSE-controlled neuronal genes.

Huntingtin protein is mutated in Huntington disease. We previously reported that wild-type but not mutant huntingtin stimulates transcription of the gene encoding brain-derived neurotrophic factor (BDNF; ref. 2). Here we show that the neuron restrictive silencer element (NRSE) is the target of wild-type huntingtin activity on BDNF promoter II. Wild-type huntingtin inhibits the silencing activity of NRSE, increasing transcription of BDNF. We show that this effect occurs through cytoplasmic sequestering of repressor element-1 transcription factor/neuron restrictive silencer factor (REST/NRSF), the transcription factor that binds to NRSE. In contrast, aberrant accumulation of REST/NRSF in the nucleus is present in Huntington disease. We show that wild-type huntingtin coimmunoprecipitates with REST/NRSF and that less immunoprecipitated material is found in brain tissue with Huntington disease. We also report that wild-type huntingtin acts as a positive transcriptional regulator for other NRSE-containing genes involved in the maintenance of the neuronal phenotype. Consistently, loss of expression of NRSE-controlled neuronal genes is shown in cells, mice and human brain with Huntington disease. We conclude that wild-type huntingtin acts in the cytoplasm of neurons to regulate the availability of REST/NRSF to its nuclear NRSE-binding site and that this control is lost in the pathology of Huntington disease. These data identify a new mechanism by which mutation of huntingtin causes loss of transcription of neuronal genes.

Animals↗
PubMed2003

Neural stem cells: a pharmacological tool for brain diseases?

Stem cells are believed to provide a tool by which new cells and tissues can be made and by which damaged ones can be replaced or repaired. Over the past few years, the existence of a subset of stem cells has been documented in the fetal brain, therefore named neural stem cells (NSCs). To this regard, the more recent demonstration that similar cells are present in the adult mammalian brain and retain the capability to produce new neurons, has undermined the dogma that neurons are only generated during the fetal life and has stimulated investigations into the regulation and role of adult neurogenesis. Here, we will review the recent advancements on the biology of brain stem cells and discuss the mechanisms and drugs regulating adult neurogenesis, aiming at better estimating the possible future applications of NSCs for brain repair.

Animals↗
PubMed2003

Freshly dissociated fetal neural stem/progenitor cells do not turn into blood.

Earlier studies suggested that stem cells from one somatic tissue may generate differentiated elements of another, embryologically unrelated, tissue after an exchange in their positions through transplantation. Two reports indicated that murine and human neural stem cells of clonogenic origin after in vitro expansion in growth factor-supplemented media, may sustain hematopoiesis when injected into sublethally irradiated mice. Here we investigated if freshly dissociated fetal neural cells (fNC) share the reported hemopoietic potential of in vitro expanded neural cells. In order to minimize the risk of hemopoietic contamination, donor cells were taken from mouse E10.5 developing brains, before completion of blood vessel ingrowth into the brain; 10(6) fNC derived directly from fetal brains of transgenic mouse expressing an enhanced version of the green fluorescent protein were injected into the tail vein or directly into the bone marrow of sublethally irradiated (6 Gy) C57B16 mice. After transplantation, the presence of donor-derived cells was assessed at different survival times by FACS analysis, PCR, and clonogenic stem cell assays on peripheral blood and bone marrow. While bone marrow-derived cells were detected from 2 weeks onward after grafting, none of the mice grafted with neural embryonic cells demonstrated any sign of transdifferentiation into hemopoietic cells up to 16 months after transplantation. Our data indicate that ability to transdifferentiate from neural into the hematopoietic phenotype, if present, is acquired only after in vitro expansion of neural stem/progenitor cells and it is not present in vivo.

Animals↗
PubMed2002

Early transcriptional profiles in huntingtin-inducible striatal cells by microarray analyses.

Gene expression studies conducted with mouse models of Huntington's disease (HD) have revealed profound modifications in gene transcription. However, the complexity of in vivo tissue hampers definition of very early transcriptional modifications and does not allow discrimination between cell-autonomous changes and those resulting from intercellular activity processes. To identify early, cell-autonomous transcriptional changes, we compared gene expression profiles of clonal striata-derived cells expressing different N-terminal 548-amino-acid huntingtin fragments (with 26, 67, 105 or 118 glutamines) under the control of a doxycycline-regulated promoter. In these cells, mutant huntingtin did not form aggregates or cause cell death; therefore, the gene expression profiles report transcriptional changes reflecting early pathogenic events. We found that genes involved in cell signaling, transcription, lipid metabolism and vesicle trafficking were affected, in some cases, within 12 hours of mutant protein induction. Interestingly, this study revealed differential expression of a number of genes involved in cholesterol and fatty acid metabolism, suggesting that these metabolic pathways may play a role in HD pathogenesis.

Animals↗