Periendothelial Cells Research Articles

The role of blood flow in vessel remodeling and its regulatory mechanism during developmental angiogenesis.

Vessel remodeling is essential for a functional and mature vascular network. According to the difference in endothelial cell (EC) behavior, we classified vessel remodeling into vessel pruning, vessel regression and vessel fusion. Vessel remodeling has been proven in various organs and species, such as the brain vasculature, subintestinal veins (SIVs), and caudal vein (CV) in zebrafish and yolk sac vessels, retina, and hyaloid vessels in mice. ECs and periendothelial cells (such as pericytes and astrocytes) contribute to vessel remodeling. EC junction remodeling and actin cytoskeleton dynamic rearrangement are indispensable for vessel pruning. More importantly, blood flow has a vital role in vessel remodeling. In recent studies, several mechanosensors, such as integrins, platelet endothelial cell adhesion molecule-1 (PECAM-1)/vascular endothelial cell (VE-cadherin)/vascular endothelial growth factor receptor 2 (VEGFR2) complex, and notch1, have been shown to contribute to mechanotransduction and vessel remodeling. In this review, we highlight the current knowledge of vessel remodeling in mouse and zebrafish models. We further underline the contribution of cellular behavior and periendothelial cells to vessel remodeling. Finally, we discuss the mechanosensory complex in ECs and the molecular mechanisms responsible for vessel remodeling.

Modeling human telencephalic development and autism-associated SHANK3 deficiency using organoids generated from single neural rosettes

Human telencephalon is an evolutionarily advanced brain structure associated with many uniquely human behaviors and disorders. However, cell lineages and molecular pathways implicated in human telencephalic development remain largely unknown. We produce human telencephalic organoids from stem cell-derived single neural rosettes and investigate telencephalic development under normal and pathological conditions. We show that single neural rosette-derived organoids contain pallial and subpallial neural progenitors, excitatory and inhibitory neurons, as well as macroglial and periendothelial cells, and exhibit predictable organization and cytoarchitecture. We comprehensively characterize the properties of neurons in SNR-derived organoids and identify transcriptional programs associated with the specification of excitatory and inhibitory neural lineages from a common pool of NPs early in telencephalic development. We also demonstrate that neurons in organoids with a hemizygous deletion of an autism- and intellectual disability-associated gene SHANK3 exhibit intrinsic and excitatory synaptic deficits and impaired expression of several clustered protocadherins. Collectively, this study validates SNR-derived organoids as a reliable model for studying human telencephalic cortico-striatal development and identifies intrinsic, synaptic, and clustered protocadherin expression deficits in human telencephalic tissue with SHANK3 hemizygosity.

Neutrophil Extracellular Traps, Angiogenesis and Cancer.

Human neutrophils, the most abundant circulating leukocytes, are fundamental components of the host response against different pathogens. Until a few years ago, neutrophils received limited attention in cancer immunology. Recently, it was discovered that both circulating, and tumor-associated, neutrophils possess functional plasticity when exposed to various inflammatory stimuli and in the tumor microenvironment. Neutrophils and their mediators can exert several pro-tumor activities in cancer and promote metastasis through different mechanisms. Angiogenesis plays a pivotal role in inflammation and tumor growth. Activated human neutrophils release several angiogenic factors [vascular endothelial growth factor-A (VEGF-A), angiopoietin-1 (ANGPT1), CXCL8, hepatocyte growth factor (HGF), and metalloproteinase 9 (MMP-9)] and form neutrophil extracellular traps (NETs). NETs promote tumor growth and metastasis formation through several mechanisms: they can awake dormant cancer cells, capture circulating tumor cells, coat and shield cancer cells, thus preventing CD8+- and natural killer (NK) cell-mediated cytotoxicity. ANGPTs released by endothelial and periendothelial mural cells induce platelet-activating factor (PAF) synthesis and neutrophil adhesion to endothelial cells. NETs can directly exert several proangiogenic activities in human endothelial cells and NETs induced by ANGPTs and PAF increase several aspects of angiogenesis in vitro and in vivo. A better understanding of the pathophysiological functions of NETs in cancer and angiogenesis could be of importance in the early diagnosis, prevention and treatment of tumors.

Validation of Specific and Reliable Genetic Tools to Identify, Label, and Target Cardiac Pericytes in Mice.

BackgroundIn the myocardium, pericytes are often confused with other interstitial cell types, such as fibroblasts. The lack of well‐characterized and specific tools for identification, lineage tracing, and conditional targeting of myocardial pericytes has hampered studies on their role in heart disease. In the current study, we characterize and validate specific and reliable strategies for labeling and targeting of cardiac pericytes.Methods and ResultsUsing the neuron‐glial antigen 2 (NG2)DsRed reporter line, we identified a large population of NG2+ periendothelial cells in mouse atria, ventricles, and valves. To examine possible overlap of NG2+ mural cells with fibroblasts, we generated NG2DsRed; platelet‐derived growth factor receptor (PDGFR) αEGFP pericyte/fibroblast dual reporter mice. Myocardial NG2+ pericytes and PDGFRα+ fibroblasts were identified as nonoverlapping cellular populations with distinct transcriptional signatures. PDGFRα+ fibroblasts expressed high levels of fibrillar collagens, matrix metalloproteinases, tissue inhibitor of metalloproteinases, and genes encoding matricellular proteins, whereas NG2+ pericytes expressed high levels of Pdgfrb, Adamts1, and Vtn. To validate the specificity of pericyte Cre drivers, we crossed these lines with PDGFRαEGFP fibroblast reporter mice. The constitutive NG2Cre driver did not specifically track mural cells, labeling many cardiomyocytes. However, the inducible NG2CreER driver specifically traced vascular mural cells in the ventricle and in the aorta, without significant labeling of PDGFRα+ fibroblasts. In contrast, the inducible PDGFRβCreER line labeled not only mural cells but also the majority of cardiac and aortic fibroblasts.ConclusionsFibroblasts and pericytes are topographically and transcriptomically distinct populations of cardiac interstitial cells. The inducible NG2CreER driver optimally targets cardiac pericytes; in contrast, the inducible PDGFRβCreER line lacks specificity.

Human iPSC-derived mesodermal progenitor cells preserve their vasculogenesis potential after extrusion and form hierarchically organized blood vessels

Post-fabrication formation of a proper vasculature remains an unresolved challenge in bioprinting. Established strategies focus on the supply of the fabricated structure with nutrients and oxygen and either rely on the mere formation of a channel system using fugitive inks or additionally use mature endothelial cells and/or peri-endothelial cells such as smooth muscle cells for the formation of blood vessels in vitro. Functional vessels, however, exhibit a hierarchical organization and multilayered wall structure that is important for their function. Human induced pluripotent stem cell-derived mesodermal progenitor cells (hiMPCs) have been shown to possess the capacity to form blood vessels in vitro, but have so far not been assessed for their applicability in bioprinting processes. Here, we demonstrate that hiMPCs, after formulation into an alginate/collagen type I bioink and subsequent extrusion, retain their ability to give rise to the formation of complex vessels that display a hierarchical network in a process that mimics the embryonic steps of vessel formation during vasculogenesis. Histological evaluations at different time points of extrusion revealed the initial formation of spheres, followed by lumen formation and further structural maturation as evidenced by building a multilayered vessel wall and a vascular network. These findings are supported by immunostainings for endothelial and peri-endothelial cell markers as well as electron microscopic analyses at the ultrastructural level. Moreover, endothelial cells in capillary-like vessel structures deposited a basement membrane-like matrix at the basal side between the vessel wall and the alginate-collagen matrix. After transplantation of the printed constructs into the chicken chorioallantoic membrane (CAM) the printed vessels connected to the CAM blood vessels and get perfused in vivo. These results evidence the applicability and great potential of hiMPCs for the bioprinting of vascular structures mimicking the basic morphogenetic steps of de novo vessel formation during embryogenesis.

Peri-endothelial cells, the versatile players in the alternating circular events of vascular growth and differentiation, a switch guided by lycat and cloche, fine tuning angiogenic responsiveness beyond linear hypoxia stimulation

Peri-endothelial cells, the versatile players in the alternating circular events of vascular growth and differentiation, a switch guided by lycat and cloche, fine tuning angiogenic responsiveness beyond linear hypoxia stimulation

EBF1 is expressed in pericytes and contributes to pericyte cell commitment

Early B-cell factor-1 (EBF1) is a transcription factor with an important role in cell lineage specification and commitment during the early stage of cell maturation. Originally described during B-cell maturation, EBF1 was subsequently identified as a crucial molecule for proper cell fate commitment of mesenchymal stem cells into adipocytes, osteoblasts and muscle cells. In vessels, EBF1 expression and function have never been documented. Our data indicate that EBF1 is highly expressed in peri-endothelial cells in both tumor vessels and in physiological conditions. Immunohistochemistry, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and fluorescence-activated cell sorting (FACS) analysis suggest that EBF1-expressing peri-endothelial cells represent bona fide pericytes and selectively express well-recognized markers employed in the identification of the pericyte phenotype (SMA, PDGFRβ, CD146, NG2). This observation was also confirmed in vitro in human placenta-derived pericytes and in human brain vascular pericytes (HBVP). Of note, in accord with the key role of EBF1 in the cell lineage commitment of mesenchymal stem cells, EBF1-silenced HBVP cells showed a significant reduction in PDGFRβ and CD146, but not CD90, a marker mostly associated with a prominent mesenchymal phenotype. Moreover, the expression levels of VEGF, angiopoietin-1, NG2 and TGF-β, cytokines produced by pericytes during angiogenesis and linked to their differentiation and activation, were also significantly reduced. Overall, the data suggest a functional role of EBF1 in the cell fate commitment toward the pericyte phenotype.

Cd34+ Stromal Cells/Telocytes in Normal and Pathological Skin.

We studied CD34+ stromal cells/telocytes (CD34+SCs/TCs) in pathologic skin, after briefly examining them in normal conditions. We confirm previous studies by other authors in the normal dermis regarding CD34+SC/TC characteristics and distribution around vessels, nerves and cutaneous annexes, highlighting their practical absence in the papillary dermis and presence in the bulge region of perifollicular groups of very small CD34+ stromal cells. In non-tumoral skin pathology, we studied examples of the principal histologic patterns in which CD34+SCs/TCs have (1) a fundamental pathophysiological role, including (a) fibrosing/sclerosing diseases, such as systemic sclerosis, with loss of CD34+SCs/TCs and presence of stromal cells co-expressing CD34 and αSMA, and (b) metabolic degenerative processes, including basophilic degeneration of collagen, with stromal cells/telocytes in close association with degenerative fibrils, and cutaneous myxoid cysts with spindle-shaped, stellate and bulky vacuolated CD34+ stromal cells, and (2) a secondary reactive role, encompassing dermatitis—e.g., interface (erythema multiforme), acantholytic (pemphigus, Hailey–Hailey disease), lichenoid (lichen planus), subepidermal vesicular (bullous pemphigoid), psoriasiform (psoriasis), granulomatous (granuloma annulare)—vasculitis (leukocytoclastic and lymphocytic vasculitis), folliculitis, perifolliculitis and inflammation of the sweat and sebaceous glands (perifolliculitis and rosacea) and infectious dermatitis (verruca vulgaris). In skin tumor and tumor-like conditions, we studied examples of those in which CD34+ stromal cells are (1) the neoplastic component (dermatofibrosarcoma protuberans, sclerotic fibroma and solitary fibrous tumor), (2) a neoplastic component with varying presentation (fibroepithelial polyp and superficial myxofibrosarcoma) and (3) a reactive component in other tumor/tumor-like cell lines, such as those deriving from vessel periendothelial cells (myopericytoma), epithelial cells (trichoepithelioma, nevus sebaceous of Jadassohn and seborrheic keratosis), Merkel cells (Merkel cell carcinoma), melanocytes (dermal melanocytic nevi) and Schwann cells (neurofibroma and granular cell tumor).

The BMP Pathway in Blood Vessel and Lymphatic Vessel Biology.

Bone morphogenetic proteins (BMPs) were originally identified as the active components in bone extracts that can induce ectopic bone formation. In recent decades, their key role has broadly expanded beyond bone physiology and pathology. Nowadays, the BMP pathway is considered an important player in vascular signaling. Indeed, mutations in genes encoding different components of the BMP pathway cause various severe vascular diseases. Their signaling contributes to the morphological, functional and molecular heterogeneity among endothelial cells in different vessel types such as arteries, veins, lymphatic vessels and capillaries within different organs. The BMP pathway is a remarkably fine-tuned pathway. As a result, its signaling output in the vessel wall critically depends on the cellular context, which includes flow hemodynamics, interplay with other vascular signaling cascades and the interaction of endothelial cells with peri-endothelial cells and the surrounding matrix. In this review, the emerging role of BMP signaling in lymphatic vessel biology will be highlighted within the framework of BMP signaling in the circulatory vasculature.

Resident CD34-positive cells contribute to peri-endothelial cells and vascular morphogenesis in salivary gland after irradiation

Salivary gland (SG) hypofunction is a common post-radiotherapy complication. Besides the parenchymal damage after irradiation (IR), there are also effects on mesenchymal stem cells (MSCs) which were shown to contribute to regeneration and repair of damaged tissues by differentiating into stromal cell types or releasing vesicles and soluble factors supporting the healing processes. However, there are no adequate reports about their roles during SG damage and regeneration so far. Using an irradiated SG mouse model, we performed certain immunostainings on tissue sections of submandibular glands at different time points after IR. Immunostaining for CD31 revealed that already one day after IR, vascular impairment was induced at the level of capillaries. In addition, the expression of CD44—a marker of acinar cells—diminished gradually after IR and, by 20 weeks, almost disappeared. In contrast, the number of CD34-positive cells significantly increased 4 weeks after IR and some of the CD34-positive cells were found to reside within the adventitia of arteries and veins. Laser confocal microscopic analyses revealed an accumulation of CD34-positive cells within the area of damaged capillaries where they were in close contact to the CD31-positive endothelial cells. At 4 weeks after IR, a fraction of the CD34-positive cells underwent differentiation into α-SMA-positive cells, which suggests that they may contribute to regeneration of smooth muscle cells and/or pericytes covering the small vessels from the outside. In conclusion, SG-resident CD34-positive cells represent a population of progenitors that could contribute to new vessel formation and/or remodeling of the pre-existing vessels after IR and thus, might be an important player during SG tissue healing.

Abstract MP123: The Fate and Role of Pericytes in Repair and Remodeling of the Infarcted Heart

Repair of the infarcted heart is dependent on inflammation-driven activation of myofibroblasts (MFs) and subsequent formation of a scar. Though pericytes have been implicated in injury-associated fibroblast activation in several organs, their potential role in cardiac repair and fibrosis has not been studied. We hypothesized that myocardial infarction (MI) may induce pericyte activation, contributing to repair through pericyte to MF conversion, secretion of fibrogenic mediators, or regulation of angiogenesis. In order to test the hypothesis, we generated pericyte/fibroblast reporter mice (NG2 DsRed ;PDGFRα GFP ). In normal myocardium, NG2 labeled peri-endothelial mural cells that coexpressed PDGFRβ, whereas PDGFRα identified interstitial cells with fibroblast characteristics. Pericytes and fibroblasts had distinct transcriptomic profiles: NG2+/PDGFRα- pericytes expressed αSMA and low amounts of extracellular matrix (ECM) genes, whereas PDGFRα+/NG2- fibroblasts synthesized collagens. Pericyte rarefaction was noted in the necrotic core 3 days after non-reperfused MI. 3-7 days post MI, expansion of the NG2+ population in the infarct zone was associated with emergence of non-mural NG2+/αSMA+ cells with MF characteristics. FACS-sorted NG2+/PDGFRα- cells from 7-day infarcts expressed higher levels of ColIα2 (7.2±1.0-fold) and ColIIIα1 (8.9±1.14-fold), when compared to NG2+/PDGFRα- cells from normal hearts. NG2+ cells had high mRNA levels of integrins α1, αV, β1, and β5, and of MMP14, reflecting an activated migratory phenotype. To examine whether expression of ECM genes by infarct pericytes is due to fibroblast conversion, we did lineage tracing studies using NG2CreER TM ;Rosa tdTomato mice bred with the PDGFRα GFP line for reliable fibroblast identification. 7 days post MI, 5.7%±1.04 of PDGFRα+ fibroblasts were derived from NG2+ cells. Also, αSMA staining showed that 10.49%±2.73 of infarct MFs were derived from NG2+ lineage. The majority of mural cells wrapping neovessels were derived from NG2+ cells, suggesting a role for resident pericytes in infarct angiogenesis. In conclusion, upon MI, pericytes become activated and contribute to repair by undergoing conversion to a subset of myofibroblasts and by coating infarct neovessels.

Platelet-derived growth factor B restores vascular barrier integrity and diminishes permeability in ovarian hyperstimulation syndrome.

Although advances in the prediction and management of ovarian hyperstimulation syndrome (OHSS) have been introduced, complete prevention is not yet possible. Previously, we and other authors have shown that vascular endothelial growth factor, angiopoietins (ANGPTs) and sphingosine-1-phosphate are involved in OHSS etiology. In addition, we have demonstrated that ovarian protein levels of platelet-derived growth factor (PDGF) ligands -B and -D decrease in an OHSS rat model, whilst PDGFR-β and ANGPT2 remain unchanged. In the present work, we investigated the role of PDGF-B in OHSS by evaluating ligand protein levels in follicular fluid (FF) from women at risk of developing OHSS and by using an immature rat model of OHSS. We demonstrated that PDGF-B and PDGF-D are lower in FF from women at risk of developing OHSS compared to control patients (P < 0.05). In the OHSS rat model, PDGF-B (0.5 µg/ovary) administration decreased ovarian weight (P < 0.05), reduced serum progesterone (P < 0.05) and lowered the percentage of cysts (P < 0.05), compared to untreated OHSS rats, but had no effect on the proportion of follicles or corpora lutea (CL). PDGF-B treatment also restored the expression of steroidogenic acute regulatory protein (P < 0.05) and P450 cholesterol side-chain cleavage enzyme (P < 0.01) to control levels. In addition, PDGF-B increased the peri-endothelial cell area in CL and cystic structures, and reduced vascular permeability compared to untreated OHSS ovaries. Lastly, PDGF-B increased the levels of junction proteins claudin-5 (P < 0.05), occludin (P < 0.05) and β-catenin (P < 0.05), while boosting the extracellular deposition of collagen IV surrounding the ovarian vasculature (PP < 0.01), compared to OHSS alone. In conclusion, our findings indicate that PDGF-B could be another crucial mediator in the onset and development of OHSS, which may lead to the development of novel prediction markers and therapeutic strategies.

Low level laser therapy (LLLT) modulates ovarian function in mature female mice

It is known that LLLT has beneficial effects on several pathological conditions including wound healing, pain and inflammation. LLLT modulates biological processes, including cell proliferation, apoptosis and angiogenesis. In the present study, we examined the effect of local application of LLLT on follicular dynamics, ovarian reserve, AMH expression, progesterone levels, apoptosis, angiogenesis, and reproductive outcome in adult mice. LLLT (200 J/cm2) increased the percentage of primary and preantral follicles, whilst decreasing the percentage of corpora lutea compared to control ovaries. LLLT-treated ovaries did not exhibit any changes regarding the number of primordial follicles. We observed a higher percentage of AMH-positive follicles (in early stages of development) in LLLT-treated ovaries compared to control ovaries. LLLT reduced the P4 concentration and the apoptosis in early antral follicles compared to control ones. LLLT caused a reduction in the endothelial cell area and an increase in the periendothelial cell area in the ovary. Additionally, LLLT was able to improve oocyte quality. Our findings suggest that local application of LLLT modulates follicular dynamics by regulating apoptosis and the vascular stability in mouse ovary. In conclusion, these data indicate that LLLT might become a novel and useful tool in the treatment of several pathologies, including female reproductive disorders.

The Leydig Cells of the Testis Originate from the Microvascular Pericytes

This review offers some clarifying thoughts about the nature and origin of the fetal and adult Leydig cells, supporting the conception that the pericytes (the periendothelial cells) and the smooth muscle cells of the microvasculature, that represent the main omnipresent adult stem cell population of the mammalian organism, are the Leydig cell ancestors. Our attention is specifically dedicated to the numerous contradictions as well as ambiguities concerning the hypotheses that the mesenchymal stromal cells (MSCs), the neural crest stem cells (NCSCs) and the peritubular myoid stem cells (PMCs) represent the stem ancestors of the Leydig cells. In effect, it becomes evident that the only pluripotent stem cell-like cells in the vertebrate body, including the testis, are the pericytes. The pericytes are derivate of the embryonal epiblast and retain its pluripotency within the microvascular niches where they are disseminated during the embryo- and fetogenesis and are stored as a resting adult stem cell population for tissue generation, maintenance, repair and regeneration. The pluripotency of the epiblast and the pericytes themselves are responsible and explain the neural features of the Leydig cells. Thus, both NCSCs and PMCs are not the ancestors of the pericytes, respectively of the Leydig cells. Biomed Rev 2017; 28: 1-21. Keywords: Leydig cells, origin, microvascular pericytes, smooth muscle cells, Leydig stem cells

In vivo intrabursal administration of bioactive lipid sphingosine-1-phosphate enhances vascular integrity in a rat model of ovarian hyperstimulation syndrome.

Can the bioactive lipid sphingosine-1 phosphate (S1P) act as an endothelial barrier-enhancing molecule and, in turn, restore the vascular integrity and homoeostasis in a rat model of ovarian hyperstimulation syndrome (OHSS). In vivo administration of S1P may prevent the early onset of OHSS and decrease its severity. Although advances in the prediction and treatment of OHSS have been made, complete prevention has not been possible yet. S1P in follicular fluid from women at risk of developing OHSS are lower in comparison from women who are not at such risk and administration of S1P in an OHSS rat model decreases ovarian capillary permeability. We used an animal model that develops OHSS in immature Sprague-Dawley rats. The rats were randomly divided into three groups: the control group, which was injected with 10 IU of pregnant mare's serum gonadotropin (PMSG), and 10 IU ofhCG 48 h later; the OHSS group, which was injected with excessive doses of PMSG (50 IU/day) for four consecutive days, followed by hCG; and the OHSS + S1P group, which was injected with the same doses of PMSG and hCG as the OHSS group and then treated with 5 μl S1P (1 mM) under the bursa of both ovaries, whereas the other groups of animals received the S1P vehicle. Rats were killed by decapitation 48 h after the hCG injection for ovary, endometrium and blood collection. The ovaries were weighed and then used for subsequent assays, while the serum was used for hormone assays. One of the ovaries from each rat (n = 6) was used for Western immunoblot and the other for immunohistochemical analysis. Statistical comparisons between groups were carried out. S1P administration reduced the ovarian weight (P < 0.05), and decreased the concentration of serum progesterone in the OHSS group compared to the OHSS group without treatment (P < 0.001). The percentage of antral follicles in the OHSS group was lower than that in the control group. S1P increased the percentage of antral follicles (P < 0.05) and decreased the percentage of corpora lutea (P < 0.01) and cystic structures in the OHSS group (P < 0.05). S1P had no effect on the expression levels of the enzymes 3β-hydroxysteroid dehydrogenase (3βHSD) or cholesterol side-chain cleavage enzyme (P450scc), but reduced the levels of steroidogenic acute regulatory protein (StAR) in OHSS rat ovaries (P < 0.05). S1P decreased the endothelial (P < 0.05) and periendothelial (P < 0.01) cell area in OHSS rat ovaries. S1P restored the levels of N-cadherin and VE-cadherin proteins to control values. Furthermore, S1P enhanced the levels of claudin-5, occludin (P < 0.05) and sphingosine-1-phosphate receptor 1 (S1PR1) in OHSS (P < 0.01). In addition, no histological differences were found in endometrium between OHSS and S1P-treated OHSS animals. The results of this study were generated from an in vivo OHSS experimental model, which has been used by several authors and our group due to the similarity between the rat and human angiogenic systems. Further studies in patients will be needed to evaluate the effects of S1P in the pathogenesis of OHSS. These findings concern the pathophysiological importance of S1P in OHSS. More studies on the regulation of endothelial cell barrier function by S1P in reproductive pathological processes and its therapeutic application are required. N/A. This work was supported by grants from ANPCyT (PICT 2012-897), CONICET (PIP 5471), Roemmers and Baron Foundations, Argentina. The authors declare no conflicts of interest.

Sphingosine-1-phosphate restores endothelial barrier integrity in ovarian hyperstimulation syndrome.

Are follicular fluid (FF) sphingosine-1-phosphate (S1P) levels in patients at risk of developing ovarian hyperstimulation syndrome (OHSS) altered and in part responsible for the high vascular permeability observed in these patients. FF S1P levels are lower in FF from patients at risk of OHSS and treatment with S1P may reduce vascular permeability in these patients. Although advances have been made in the diagnosis, and management of OHSS and in basic knowledge of its development, complete prevention has proven difficult. A total of 40 FF aspirates were collected from patients undergoing ART. The women (aged 25-39 years old) were classified into a control group (n=20) or a group at risk of OHSS (n=20). The EA.hy926 endothelial cell line was used to assess the efffects of FF from patients at risk of OHSS with or without the addition of S1P. An animal model that develops OHSS in immature Sprague-Dawley rats were also used. Migration assays, confocal microscopy analysis of actin filaments, immunoblotting and quail chorioallantoic membrane (CAM) assays of in-vivo angiogenesis were performed and statistical comparisons between groups were made. The S1P concentration was significantly lower in FF from patients at risk of OHSS (P = 0.03). The addition of S1P to this FF decreased cell migration (P < 0.05) and prevented VE-cadherin phosphorylation in endothelial cells (P < 0.05). S1P in the FF from patients at risk of OHSS increased the levels of VE-cadherin (P < 0.05), N-cadherin (P < 0.05) and β-catenin (P < 0.05), and partially reversed actin redistribution in endothelial cells. The addition of S1P in FF from patients at risk of OHSS also decreased the levels of vascular endothelial growth factor (VEGF121; P < 0.01) and S1P lyase (SPL; P < 0.05) and increased the levels of S1PR1 (P < 0.05) in endothelial cells. In CAMs incubated with FF from patients at risk of OHSS with S1P, the number of vessel branch points decreased while the periendothelial cell coverage increased. Additionally, in a rat OHSS model, we demonstrated that vascular permeability and VEGF121 and its receptor KDR expression were increased in the OHSS group compared to the control group and that S1P administration decreased these parameters. N/A. The results of this study were generated from an in-vitro system. This model reflects the microvasculature in vivo. Even though the ideal model would be the use of human endothelial cells from the ovary, it is obviously not possible to carry out this kind of approach in ovaries of patients from ART. More studies will be necessary to delineate the effects of S1P in the pathogenesis of OHSS. Hence, clinical studies are needed in order to choose the most appropriate method of prevention and management. The use of bioactive sphingolipid metabolites may contribute to finding better and safer therapeutic strategies for the treatment of OHSS and other human diseases that display aberrant vascular leakage. This work was supported by grants ANPCyT (PICT 2012-897), CONICET (PIP 5471), Roemmers and Baron Foundation, Argentina. The authors declare no conflict of interest.

Skeletal and cardiac muscle pericytes: Functions and therapeutic potential.

Pericytes are periendothelial mesenchymal cells residing within the microvasculature. Skeletal muscle and cardiac pericytes are now recognized to fulfill an increasing number of functions in normal tissue homeostasis, including contributing to microvascular function by maintaining vessel stability and regulating capillary flow. In the setting of muscle injury, pericytes contribute to a regenerative microenvironment through release of trophic factors and by modulating local immune responses. In skeletal muscle, pericytes also directly enhance tissue healing by differentiating into myofibers. Conversely, pericytes have also been implicated in the development of disease states, including fibrosis, heterotopic ossication and calcification, atherosclerosis, and tumor angiogenesis. Despite increased recognition of pericyte heterogeneity, it is not yet clear whether specific subsets of pericytes are responsible for individual functions in skeletal and cardiac muscle homeostasis and disease.

Ovule Structure of Scotch thistle Onopordum acanthium L. (Cynareae, Asteraceae)

AbstractStudies concerning the ultrastructure of the periendothelial zone integumentary cells of Asteraceae species are scarce. The aim was to check whether and/or what kinds of integument modifications occur inOnopordum acanthium. Ovule structure was investigated using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. For visualization of calcium oxalate crystals, the polarizing microscopy was used. The periendothelial zone of integument inO. acanthiumis well developed and composed of mucilage cells near the integumentary tapetum and large, highly vacuolated cells at the chalaza and therefore they differ from other integumentary cells. The cells of this zone lack starch and protein bodies. Periendothelial zone cells do not have calcium oxalate crystals, in contrast to other integument cells. The disintegration of periendothelial zone cells was observed in a mature ovule. The general ovule structure ofO. acanthiumis similar to other members of the subfamily Carduoideae, although it is different to “Taraxacum”, “Galinsoga” and “Ratibida” ovule types.

Local administration of platelet-derived growth factor B (PDGFB) improves follicular development and ovarian angiogenesis in a rat model of Polycystic Ovary Syndrome

Alterations in ovarian angiogenesis are common features in Polycystic Ovary Syndrome (PCOS) patients; the most studied of these alterations is the increase in vascular endothelial growth factor (VEGF) production by ovarian cells. Platelet-derived growth factor B (PDGFB) and D (PDGFD) are decreased in follicular fluid of PCOS patients and in the ovaries of a rat model of PCOS. In the present study, we aimed to analyze the effects of local administration of PDGFB on ovarian angiogenesis, follicular development and ovulation in a DHEA-induced PCOS rat model. Ovarian PDGFB administration to PCOS rats partially restored follicular development, decreased the percentage of cysts, increased the percentage of corpora lutea, and decreased the production of anti-Müllerian hormone. In addition, PDGFB administration improved ovarian angiogenesis by reversing the increase in periendothelial cell area and restoring VEGF levels. Our results shed light into the mechanisms that lead to altered ovarian function in PCOS and provide new data for potential therapeutic strategies.

Physiology in Perspective: Why Do We Continue to Ignore Sex Differences?

In 2001, the Institute of Medicine (IOM) of the National Academy of Sciences issued a report in which they highlighted the importance of exploring sex differences in biomedical research and medical practice. The IOM report recognized the obvious biological fact that sex, as defined by the presence