The CXCL12/CXCR4/CXCR7 ligand-receptor system regulates neuro-glio-vascular interactions and vessel growth during human brain development.

This study investigates glio-vascular interactions in human fetal brain at midgestation, specifically examining the expression and immunolocalization of the CXCL12/CXCR4/CXCR7 ligand-receptor axis and its possible role in the vascular patterning of the developing brain. At midgestation, the telencephalic vesicles are characterized by well developed radial glia cells (RGCs), the first differentiated astrocytes and a basic vascular network mainly built of radial vessels. RGCs have been recognized to contribute to cerebral cortex neuro-vascular architecture and have also been demonstrated to act as a significant source of neural cells (Rakic, Brain Res 33:471-476, 1971; Malatesta et al, Development 127:5253-5263, 2000). According to our hypothesis CXCL12, a potent migration and differentiation chemokine released by RGCs, may act as a linking factor coordinating neuroblast migration with vessel growth and patterning through the activation of different ligand/receptor axes. The obtained results support this hypothesis showing that together with CXCR4/CXCR7-reactive neuroblasts, which migrate in close association with CXCL12 RGCs, layer-specific subsets of CXCL12 RGCs and astrocytes specifically contact the microvessel wall. Moreover, the CXCL12/CXCR4/CXCR7 system appears to be directly involved in microvessel growth, its members being differentially expressed in angiogenically activated microvessels and vascular sprouts.

Plasma membrane-derived microvesicles released from tip endothelial cells during vascular sprouting.

During human foetal brain vascularization, activated CD31+/CD105+ endothelial cells are characterized by the emission of filopodial processes which also decorate the advancing tip of the vascular sprout. Together with filopodia, both the markers also reveal a number of plasma membrane-derived microvesicles (MVs) which are concentrated around the tip cell tuft of processes. At this site, MVs appear in tight contact with endothelial filopodia and follow these long processes, advancing into the surrounding neuropil to a possible cell target. These observations suggest that, like shedding vesicles of many other cell types that deliver signalling molecules and play a role in cell-to-cell communication, MVs sent out from endothelial tip cells could be involved in tip cell guidance and/or act on target cells, regulating cell-to-cell mutual recognition during vessel sprouting and final anastomosis. The results also suggest a new role for tip cell filopodia as conveyor processes for transporting MVs far from the cell of origin in a controlled microenvironment. Additional studies focused on the identification of MV content are needed to ultimately clarify the significance of tip cell MVs during human brain vascularization.

Oxytocin is an anabolic bone hormone.

We report that oxytocin (OT), a primitive neurohypophyseal hormone, hitherto thought solely to modulate lactation and social bonding, is a direct regulator of bone mass. Deletion of OT or the OT receptor (Oxtr) in male or female mice causes osteoporosis resulting from reduced bone formation. Consistent with low bone formation, OT stimulates the differentiation of osteoblasts to a mineralizing phenotype by causing the up-regulation of BMP-2, which in turn controls Schnurri-2 and 3, Osterix, and ATF-4 expression. In contrast, OT has dual effects on the osteoclast. It stimulates osteoclast formation both directly, by activating NF-kappaB and MAP kinase signaling, and indirectly through the up-regulation of RANK-L. On the other hand, OT inhibits bone resorption by mature osteoclasts by triggering cytosolic Ca(2+) release and NO synthesis. Together, the complementary genetic and pharmacologic approaches reveal OT as a novel anabolic regulator of bone mass, with potential implications for osteoporosis therapy.

Cerebral cortex demyelination and oligodendrocyte precursor response to experimental autoimmune encephalomyelitis.

Experimentally induced autoimmune encephalomyelitis (EAE) in mice provides an animal model that shares many features with human demyelinating diseases such as multiple sclerosis (MS). To what extent the cerebral cortex is affected by the process of demyelination and how the corollary response of the oligodendrocyte lineage is explicated are still not completely known aspects of EAE. By performing a detailed in situ analysis of expression of myelin and oligodendrocyte markers we have identified areas of subpial demyelination in the cerebral cortex of animals with conventionally induced EAE conditions. On EAE-affected cerebral cortices, the distribution and relative abundance of cells of the oligodendrocyte lineage were assessed and compared with control mouse brains. The analysis demonstrated that A2B5(+) glial restricted progenitors (GRPs) and NG2(+)/PDGFR-α(+) oligodendrocyte precursor cells (OPCs) were increased in number during "early" disease, 20 days post MOG immunization, whereas in the "late" disease, 39 days post-immunization, they were strongly diminished, and there was an accompanying reduction in NG2(+)/O4(+) pre-oligodendrocytes and GST-π mature oligodendrocytes. These results, together with the observed steady-state amount of NG2(-)/O4(+) pre-myelinating oligodendrocytes, suggested that oligodendroglial precursors attempted to compensate for the progressive loss of myelin, although these cells appeared to fail to complete the last step of their differentiation program. Our findings confirm that this chronic model of EAE reproduces the features of neocortex pathology in progressive MS and suggest that, despite the proliferative response of the oligodendroglial precursors, the failure to accomplish final differentiation may be a key contributing factor to the impaired remyelination that characterizes these demyelinating conditions.

Microgravity during spaceflight directly affects in vitro osteoclastogenesis and bone resorption.

During space flight, severe losses of bone mass are observed. Both bone formation and resorption are probably involved, but their relative importance remains unclear. The purpose of this research is to understand the role of osteoclasts and their precursors in microgravity-induced bone loss. Three experiments on isolated osteoclasts (OCs) and on their precursors, OSTEO, OCLAST, and PITS, were launched in the FOTON-M3 mission. The OSTEO experiment was conducted for 10 d in microgravity within bioreactors with a perfusion system, where the differentiation of precursors, cultured on a synthetic 3-dimensional bonelike biomaterial, skelite, toward mature OCs was assessed. In OCLAST and in PITS experiments, differentiated OCs were cultured on devitalized bovine bone slices for 4 d in microgravity. All of the experiments were replicated on ground in the same bioreactors, and OCLAST also had an inflight centrifuge as a control. Gene expression in microgravity, compared with ground controls, demonstrated a severalfold increase in genes involved in osteoclast maturation and activity. Increased bone resorption, proved by an increased amount of collagen telopeptides released VS ground and centrifuge control, was also found. These results indicate for the first time osteoclasts and their precursors as direct targets for microgravity and mechanical forces.

Osteoblasts cultured on three-dimensional synthetic hydroxyapatite implanted on a chick allantochorial membrane induce ectopic bone marrow differentiation.

Osteoblast (OB) activities have been studied on hydroxyapatite three-dimensional (3D) scaffolds in comparison with traditional planar substrata. OBs cultured on 3D displayed increased proliferation, differentiation, and matrix protein synthesis, when compared to 2D cultures on the same substrata. Confluent cultures, however, could not be maintained for long, due to insufficient fluid diffusion within 3D scaffolds that impaired cell viability. Thus, confluent OB 3D cultures were implanted on the allantochorial membrane of chick embryos. Vessels from the embryo colonized the bone-like network giving rise in the presence of OBs to an ectopic bone marrow formation in the intratrabecular spaces. In the absence of OBs, when the biomaterial alone was implanted, blood vessels were still present but hematopoietic marrow was absent. In both cases osteoclasts (OCs) derived from the host were found on the implant surface. These results indicated that scaffolds with cells can be easily vascularized and confirmed the role of OBs in the definition of the microenvironment that induce blood marrow differentiation in the intratrabecular spaces.

During yeast chronological aging resveratrol supplementation results in a short-lived phenotype Sir2-dependent.

Resveratrol (RSV) is a naturally occurring polyphenolic compound endowed with interesting biological properties/functions amongst which are its activity as an antioxidant and as Sirtuin activating compound towards SIRT1 in mammals. Sirtuins comprise a family of NAD+-dependent protein deacetylases that are involved in many physiological and pathological processes including aging and age-related diseases. These enzymes are conserved across species and SIRT1 is the closest mammalian orthologue of Sir2 of Saccharomyces cerevisiae. In the field of aging researches, it is well known that Sir2 is a positive regulator of replicative lifespan and, in this context, the RSV effects have been already examined. Here, we analyzed RSV effects during chronological aging, in which Sir2 acts as a negative regulator of chronological lifespan (CLS). Chronological aging refers to quiescent cells in stationary phase; these cells display a survival-based metabolism characterized by an increase in oxidative stress. We found that RSV supplementation at the onset of chronological aging, namely at the diauxic shift, increases oxidative stress and significantly reduces CLS. CLS reduction is dependent on Sir2 presence both in expired medium and in extreme Calorie Restriction. In addition, all data point to an enhancement of Sir2 activity, in particular Sir2-mediated deacetylation of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase (Pck1). This leads to a reduction in the amount of the acetylated active form of Pck1, whose enzymatic activity is essential for gluconeogenesis and CLS extension.

Nicotinamide supplementation phenocopies SIR2 inactivation by modulating carbon metabolism and respiration during yeast chronological aging.

Nicotinamide (NAM), a form of vitamin B3, is a byproduct and noncompetitive inhibitor of the deacetylation reaction catalyzed by Sirtuins. These represent a family of evolutionarily conserved NAD+-dependent deacetylases that are well-known critical regulators of metabolism and aging and whose founding member is Sir2 of Saccharomyces cerevisiae. Here, we investigated the effects of NAM supplementation in the context of yeast chronological aging, the established model for studying aging of postmitotic quiescent mammalian cells. Our data show that NAM supplementation at the diauxic shift results in a phenocopy of chronologically aging sir2Δ cells. In fact, NAM-supplemented cells display the same chronological lifespan extension both in expired medium and extreme Calorie Restriction. Furthermore, NAM allows the cells to push their metabolism toward the same outcomes of sir2Δ cells by elevating the level of the acetylated Pck1. Both these cells have the same metabolic changes that concern not only anabolic pathways such as an increased gluconeogenesis but also respiratory activity in terms both of respiratory rate and state of respiration. In particular, they have a higher respiratory reserve capacity and a lower non-phosphorylating respiration that in concert with a low burden of superoxide anions can affect positively chronological aging.

Blood-brain barrier alterations in the cerebral cortex in experimental autoimmune encephalomyelitis.

The pathophysiology of cerebral cortical lesions in multiple sclerosis (MS) is not understood. We investigated cerebral cortex microvessels during immune-mediated demyelination in the MS model chronic murine experimental autoimmune encephalomyelitis (EAE) by immunolocalization of the endothelial cell tight junction (TJ) integral proteins claudin-5 and occludin, a structural protein of caveolae, caveolin-1, and the blood-brain barrier-specific endothelial transporter, Glut 1. In EAE-affected mice, there were areas of extensive subpial demyelination and well-demarcated lesions that extended to deeper cortical layers. Activation of microglia and absence of perivascular inflammatory infiltrates were common in these areas. Microvascular endothelial cells showed increased expression of caveolin-1 and a coincident loss of both claudin-5 and occludin normal junctional staining patterns. At a very early disease stage, claudin-5 molecules tended to cluster and form vacuoles that were also Glut 1 positive; the initially preserved occludin pattern became diffusely cytoplasmic at more advanced stages. Possible internalization of claudin-5 on TJ dismantling was suggested by its coexpression with the autophagosomal marker MAP1LC3A. Loss of TJ integrity was confirmed by fluorescein isothiocyanate-dextran experiments that showed leakage of the tracer into the perivascular neuropil. These observations indicate that, in the cerebral cortex of EAE-affected mice, there is a microvascular disease that differentially targets claudin-5 and occludin during ongoing demyelination despite only minimal inflammation.

Characterization of oligodendrocyte lineage precursor cells in the mouse cerebral cortex: a confocal microscopy approach to demyelinating diseases.

The identification of stem cells resident in the adult central nervous system has redirected the focus of research into demyelinating diseases, such as multiple sclerosis, mainly affecting the brain white matter. This immunocytochemical and morphometrical study was carried out by confocal microscopy in the adult mouse cerebral cortex, with the aim of analysing, in the brain grey matter, the characteristics of the oligodendrocyte lineage cells, whose capability to remyelinate is still controversial. The observations demonstrated the presence in all the cortex layers of glial restricted progenitors, reactive to A2B5 marker, oligodendrocyte precursor cells, expressing the NG2 proteoglycan, and pre-oligodendrocytes and pre-myelinating oligodendrocytes, reactive to the specific marker O4. NG2 expressing cells constitute the major immature population of the cortex, since not only oligodendrocyte precursor cells and pre-oligodendrocytes but also a part of the glial restrict progenitors express the NG2 proteoglycan. Together with the population of these immature cells, a larger population of mature oligodendrocytes was revealed by the classical oligodendrocyte and myelin markers, 2',3'-cyclic nucleotide 3'-phosphodiesterase, myelin basic protein and myelin oligodendrocyte glycoprotein. The results indicate that oligodendrocyte precursors committed to differentiate into myelin forming oligodendrocytes are present through all layers of the adult cortex and that their phenotypic features exactly recall those of the oligodendroglial lineage cells during development.