骨髓源性血管内皮前体细胞与出生后生理性和病理性血管形成

Endothelial progenitor cells （EPCs） exist in bone marrow, umbilical cord blood and peripheral blood of adult mammals, including humans. Furthermore, the discovery of EPCs has led to the notion of adult vasculogenesis, in which bone marrow (BM)-derived EPCs home to and incorporate into sites of new blood vessel formation, where they differentiate into endothelial cells, which is consistent with postnatal vasculogenesis. It has become apparent that circulating BM-derived EPCs are involved in promoting physiologic andpathologic neovascularization, such as wound healing and tumor growth. They are of great clinical importance in pro-or anti-angiogenic therapies.     

Glycosaminoglycans produced in tissue culture by rat lung cells. Isolation from a mixed cell line and a derived endothelial clone.

The glycosaminoglycans produced by a mixed cell line of normal adult rat lung and an endothelial clone derived from this line were isolated and examined. Cellulose acetate electrophoresis of media and cells before and after digestion with specific enzymes indicated that all the major glycosaminoglycans except keratan sulfate were synthesized by both cultures. Heparan sulfate and dermatan sulfate were found only in the cell fraction while hyaluronic acid was found in both the medium and the cell fractions. The chondroitin sulfates were isolated from the medium. The endothelial clone produced a 4:1 ratio of glucosamine to galactosamine in the medium from the fifth through thirteenth months of culture. The medium of the mixed cell line initially contained glycosaminoglycans with a glucosamine to galactosamine ratio of 2:1 but after approximately one year of culture, the ratio had changed to 4.6:1 suggesting that the culture contained predominatly endothelial cells.     

Maintenance and repair of the lung endothelium does not involve contributions from marrow-derived endothelial precursor cells

Lung endothelium is believed to be a quiescent tissue with the potential to exhibit rapid and effective repair after injury. Endothelial progenitor cells derived from the bone marrow have been proposed as one source of new endothelial cells that may directly contribute to pulmonary endothelial cell homeostasis and repair. Here we use bone marrow transplantation models, using purified hematopoietic stem cells (HSCs) or unfractionated whole marrow, to assess engraftment of cells in the endothelium of a variety of tissues. We find scant evidence for any contribution of bone marrow-derived cells to the pulmonary endothelium in the steady state or after recovery from hyperoxia-induced endothelial injury. Although a rare population of CD45-/CD31+/VECadherin+ bone marrow-derived cells, originating from HSCs, can be found in lung tissue after transplantation, these cells are not readily found in anatomic locations that define the pulmonary endothelium. Moreover, by tracking transplanted bone marrow cells obtained from donor transgenic mice containing endothelial lineage-selective reporters (Tie2-GFP), no contribution of bone marrow-derived cells to the adult lung, liver, pancreas, heart, and kidney endothelium can be detected, even after prolonged follow-up periods of 11 months or after recovery from hyperoxic pulmonary endothelial injury. Our findings argue against any significant engraftment of bone marrow-derived cells in the pulmonary vascular endothelium.     

VEGF coordinates interaction of pericytes and endothelial cells during vasculogenesis and experimental angiogenesis.

Biological activities of vascular endothelial growth factor (VEGF) have been studied extensively in endothelial cells (ECs), but few data are available regarding its effects on pericytes. In murine embryoid body cultures, VEGF-induced expression of desmin and alpha-smooth muscle actin (alpha-SMA) in CD-31+ cells. The number of CD-31+/desmin+ vascular chords increased with VEGF treatment time and peaked during a differentiation window between 6 and 9 days after plating. In vivo, VEGF-induced elongation and migration of desmin-positive pericytes and coverage of angiogenic capillaries, as revealed by analysis of Sambucus nigra lectin-stained vascular beds of the chick chorioallantoic membrane. VEGF also caused significant decrease of intercapillary spaces, an indicator for intussusceptive vascular growth. These VEGF-mediated effects point at a more intricate interaction between ECs and pericytes cells than previously demonstrated and suggest that pericytes may be derived from EC progenitors in vitro and not only stabilize capillaries but also participate in vascular remodeling in vivo.     

Low-molecular-weight peptides derived from extracellular matrix as chemoattractants for primary endothelial cells.

The development of synthetic and naturally occurring scaffolds for tissue engineering applications has included strategies to promote attachment of specific cell types, control the rate of scaffold degradation, encourage angiogenesis, or otherwise modulate the host response. We have reported that bioscaffolds developed from porcine small intestinal submucosa (SIS) facilitate the constructive remodeling of tissues and recruit marrow-derived cells that persist long after the acute inflammatory stages have resolved. We have not yet determined which cells are recruited, the eventual fate of these cells, or via what mechanisms the events occur. We now have analyzed various molecular weight fractions of acid-hydrolyzed SIS by both functional and morphologic methods and have determined that fraction 4 (5 to 16 kDa) possesses chemoattractant activity for primary murine adult liver, heart, and kidney endothelial cells in vitro. Addition of fraction 4 to Matrigel plugs promoted in vivo vascularization when the plugs were implanted subcutaneously in mice. These results indicate that small-molecular-weight peptides derived from the degradation of porcine SIS are biologically active in the recruitment of murine endothelial cells in vitro and in vivo.     

Cerebral endothelial derived vascular endothelial growth factor promotes the migration but not the proliferation of oligodendrocyte precursor cells in vitro

In gray matter, cerebral endothelium is known to provide trophic support for neighboring cells such as neurons. However, signaling from cerebral endothelium to white matter cells remains to be elucidated. Here, we show that vascular endothelial growth factor (VEGF-A) secreted from cerebral endothelial cells promotes the migration but not the proliferation of oligodendrocyte precursor cells (OPCs). Cultured OPCs were obtained from newborn rat cortex, and treatment with conditioned culture media of cerebral endothelial cells increased the OPC proliferation and migration. Importantly, co-treatment with anti-neutralizing antibody for Flk-1 (VEGF-receptor2) inhibited OPC movement but did not affect OPC propagation. Western blot and flow cytometry analyses confirmed that our cultured cerebral endothelial cells produced VEGF-A and our cultured OPCs expressed Flk-1. Taken together, our current data suggest that cerebral endothelium is supportive for oligodendrocyte lineage cells and VEGF-A may participate in the endothelium–OPC cell–cell signaling. This phenomenon may be important for white matter homeostasis.     

Beta1 integrin expression on endothelial cells is required for angiogenesis but not for vasculogenesis.

Integrins are a family of cell adhesion receptors that are involved in cell-matrix and cell-cell communications. They facilitate cell proliferation, migration, and survival. Using the Cre-Lox system, we deleted beta1 integrin on Tie2-positive (Tie2-cre beta1 Int (fl/fl)) vascular endothelial cells. Deletion of beta1 integrin on vascular endothelial cells results in embryonic lethality. Blood vessel defects are encountered in the Tie2-Cre beta1 Int (fl/fl) embryos at embryonic age (E9.5), and embryos die before reaching E10.5. The embryos exhibit growth retardation and both histological evaluation and PECAM-1 staining of E9.5 embryos revealed defects in angiogenic sprouting and vascular branching morphogenesis. Large and medium-size vessel formation is not affected in these embryos. Angiogenic defects were observed in several regions of the embryo and yolk sacs. These results indicate that beta1 integrin expression on vascular endothelial cells is crucial for embryonic angiogenesis but dispensable for vasculogenesis.     

A self-assembled fibroblast-endothelial cell co-culture system that supports in vitro vasculogenesis by both human umbilical vein endothelial cells and human dermal microvascular endothelial cells

The construction of vascularized connective tissues is an important goal in tissue engineering in that the presence of a patent bio-engineered vasculature should facilitate vascularization of an implant. Fibroblasts play an essential role in the angiogenic process through their production of extracellular matrix molecules and through their release of essential growth factors. Therefore, the aim of this study is to develop a thin 3-dimensional model in which fibroblasts support endothelial cells in the formation of tube-like structures. Macro- and microvascular endothelial cells were seeded onto confluent lawns of human fibroblasts and were cultured in the presence of high levels of ascorbate 2-phosphate to create a tissue-like structure in which endothelial cell organized into tube-like structures. The process was visualized in the culture dish through labeling of cells with a long-lasting fluorescent vital dye. Intact sheet-like structures were created in which endothelial cell tube-like structures were encased by fibroblasts and were surrounded by a basement membrane. These structures appeared to contain a lumen and remained stable for up to 5 weeks in culture. This culture system provides an in vitro method to study fibroblast-endothelial cell interactions and to study the effects of pro- and anti-angiogenic factors on endothelial cell differentiation. This system also provides an experimental basis for developing vascularized tissue-engineered connective tissue.     

Simultaneous differentiation of endothelial and trophoblastic cells derived from human embryonic stem cells

Here we present a simple two-step in vitro model of vascularized trophoblastic tissue derived from human embryonic stem (hES) cells. The first step is the formation of cystic embryoid bodies (EBs) in suspension in a semisolid methyl cellulose medium, within which an endothelial platelet/endothelial cell adhesion molecule-1 (PECAM-1(+)) cell network develops. In a second step, deposition of these EBs on the bottom of nontreated, polystyrene tissue culture plates, leads by centrifugal outgrowth of the EB to the emergence of an adherent cell layer, with which a PECAM-1(+) network is associated. Cells of this adherent layer expressed VE-cadherin (CD144), PECAM-1 (CD31), and alpha-fetoprotein (alpha-FP). Trophoblastic differentiation was strongly suggested by the secretion of beta-human chorionic gonadotropin (beta-hCG) and by the presence of the cytotrophoblast and syncytiotrophoblast marker GB25. The INSL4 gene, a cyto and syncytio-trophoblast marker, was also highly expressed in the adherent layer, as well as other trophoblast genes such as CGA, CDX1, CDX2, and HAND1, compared to hES cell gene expression taken as reference. In contrast, expression of self-renewal genes, such as TERT, POU5F1, ZFP42, GDF3, and NODAL were decreased. No ectodermal or endodermal genes were expressed, but the mesodermal genes PECAM-1 and GATA2 were. The possibility of removing the EBs during the second step would permit analysis of their relative contribution to angiogenesis or possible hemangioblast formation, compared to that of the trophoblastic adherent layer. This primitive vascularized trophoblastic model could also provide a tool to study early steps of normal and pathological placental development.     

人外周血单个核细胞来源内皮祖细胞的生物学性状

目的 探讨从成人外周血单个核细胞中分离、培养内皮祖细胞（EPCs）的方法以及EPCs的生物学特征。方法 密度梯度离心法获得单个核细胞（MNCs），种植于纤连蛋白包被的培养板中。每2h去除1次未黏附细胞共2次，然后隔日换液1次，7d后计数早期集落。每例血样均分为2等份，1份在获得早期集落后进行实验；另1份持续培养至晚期集落出现进行相同实验。流式细胞技术检测细胞表面抗原表达，ELISA法测定上清液中血管内皮生长因子（VEGF）浓度。胶原凝胶细胞种植实验测定体外血管生成功能。结果 早期集落中心为圆形细胞，周边是放射状排列的纺锤形细胞，再种植不能形成第二代集落且无体外血管形成功能，细胞表面主要表达CD14和CD45，培养上清液中可测到高浓度的VEGF。晚期集落在培养21至28d间出现，再种植可形成第二代内皮细胞集落，并能在胶原凝胶中形成管腔样结构。其构成细胞与早期集落相比CD45、CD14表达显著减少（P<0.001）而CD146表达明显增加（P<0.01）。结论 人外周血单个核细胞在内皮培养条件下可形成早期和晚期集落，构成早期集落的绝大多数细胞属于单核细胞系列，可分泌VEGF但不能分化成内皮细胞，晚期集落具有内皮祖细胞的形态和生物学特征。     

Culture and characterization of microvascular endothelial cells derived from human brain

Primary cultures of human cerebral endothelial cells were established from microvessels isolated from cortical fragments removed at surgery for seizure disorder and from brains at autopsy. A uniform population of cells growing in close association to each other formed confluent monolayers by 7 to 10 days in culture. They contained factor VIII/Von Willebrand antigen, the most specific marker for cells of endothelial origin, and showed lectin-binding sites for Ulex europaeus agglutinin characteristic of human endothelium. Cultured cells formed thin, continuous monolayers, contained few pinocytotic vesicles, and were joined together by tight junctional complexes. More than 99% of the intercellular junctions restricted the transendothelial passage of horseradish peroxidase. Monolayers of human brain microvessel endothelial cells thus resemble cerebral endothelium in vivo and should provide a useful in vitro model for studies of the biology of these cells and their role in the pathogenesis of certain human central nervous system diseases associated with abnormal blood-brain barrier function.     

Embryonic cardiomyocyte expression of endothelial genes.

Vertebrate precardiac mesoderm contains cells destined to become cardiomyocyte or endothelial cells. To determine the stability of these phenotypes freshly isolated embryonic day (E) 2.5-E6 chicken hearts were immunostained for myosin heavy chain (MyHC) to identify cardiomyocytes, and von Willebrand factor (vWF) and Flk-1 to identify endothelial cells. At E2.5-E3, 90% of cells express only MyHC and 6% express only vWF/Flk-1. However, 2% MyHC+ cells in E2.5-E3 hearts and 0.3% in E4-E6 hearts, also express vWF/Flk-1; and when cultured 3 days, >40% of the MyHC+ cells express vWF/Flk-1, but they do not express Vezf1, vascular endothelial cadherin, or Tie2. Thus, only a subset of endothelial genes are induced in cultured cardiomyocytes. While the subsequent developmental fate of embryonic heart cells exhibiting a vWF+/MyHC+ phenotype is unknown, analysis of this phenotype may provide information pertinent to mechanisms of cell phenotype stability, cellular transdifferentiation, and induction of stable cell types from embryonic stem cells.     

Apoptotic sphingolipid signaling by ceramides in lung endothelial cells

The de novo pathway of ceramide synthesis has been implicated in the pathogenesis of excessive lung apoptosis and murine emphysema. Intracellular and paracellular-generated ceramides may trigger apoptosis and propagate the death signals to neighboring cells, respectively. In this study we compared the sphingolipid signaling pathways triggered by the paracellular- versus intracellular-generated ceramides as they induce lung endothelial cell apoptosis, a process important in emphysema development. Intermediate-chain length (C(8:0)) extracellular ceramides, used as a surrogate of paracellular ceramides, triggered caspase-3 activation in primary mouse lung endothelial cells, similar to TNF-alpha-generated endogenous ceramides. Inhibitory siRNA against serine palmitoyl transferase subunit 1 but not acid sphingomyelinase inhibited both C(8:0) ceramide- and TNF-alpha (plus cycloheximide)-induced apoptosis, consistent with the requirement for activation of the de novo pathway of sphingolipid synthesis. Tandem mass spectrometry analysis detected increases in both relative and absolute levels of C(16:0) ceramide in response to C(8:0) and TNF-alpha treatments. These results implicate the de novo pathway of ceramide synthesis in the apoptotic effects of both paracellular ceramides and TNF-alpha-stimulated intracellular ceramides in primary lung endothelial cells. The serine palmitoyl synthase-regulated ceramides synthesis may contribute to the amplification of pulmonary vascular injury induced by excessive ceramides.     

Arthritis transferred by cells derived from pre-inflammatory rat synovium.

Different cell populations isolated from rats during the period of latency of adjuvant arthritis were injected into the bloodstream of naive rats to test their ability to transfer articular disorders. Synovium-derived cells (synoviocytes) were able to induce arthritis in 3 out of 4 recipient animals, whereas peripheral blood leukocytes, peritoneal exudate macrophages, lymph node cells, synoviocyte lysates and synoviocytes from control animals were not able to do so. This model of cellular transferred arthritis is associated with antibody titres to hsp65 in rat sera. Our findings suggest a crucial role for synovial cells in the pathogenesis of adjuvant disease, which might be linked to their function as accessory cells.     

Egfl7 knockdown causes defects in the extension and junctional arrangements of endothelial cells during zebrafish vasculogenesis.

The endothelial cell (EC) -specific secreted protein EGFL7 is important for tubulogenesis in newly forming blood vessels. We studied its role in vascular tube formation by a quantitative ultrastructural analysis of Egfl7-knockdown zebrafish embryos. At 24 hours postfertilization, the endothelia of dorsal aorta (DA) and posterior cardinal vein (PCV) were correctly anchored to the hypochord and endoderm, respectively, but failed to expand into the vascular area. This resulted in vessels with reduced or split lumen and open sheets of ECs. Concomitantly, the organization of hematopoietic cells-identified by the presence of previously undescribed membrane tubules-between DA and PCV, and within the vessels, was severely disturbed. Strikingly, ectopic cell junctions occurred across the obstructed vessel lumen, on the luminal EC surfaces, which in control conditions never display junctions of any kind. These data suggest that Egfl7 provides ECs with a cue for their extension into the vascular area and in establishing EC cell polarity.     

Exosomes derived from monocytes and from endothelial cells mediate monocyte and endothelial cell activation under high d-glucose conditions

Diabetes mellitus type 2 (DMT2) is characterized by hyperglycemia and associated with low grade inflammation affecting both endothelial cells and monocytes. Exosomes are nanovesicles, allow communication between endothelial cells and monocytes and have been associated with diabetic complications. In this study we evaluated whether high glucose can activate monocytes and endothelial cells and whether exosomes play a role in this activation. Moreover, we studied whether endothelial cells and monocytes communicate with each other via exosomes under high and basal glncubation. In the first experiment, monomac 6 cells (MM6) were exposed to high glucose (HG; 25?mmol/L) or to exosomes from MM6 exposed to HG (exoMM6-HG) or basal glucose (5.5?mmol/L) (exoMM6-BG). In the second experiment, MM6 were exposed to exosomes from human umbilical vein endothelial cells (HUVECs) and HUVECs to exosomes from MM6. In the third experiment, MM6 and HUVECs were exposed to a mixture of exosomes from MM6 and HUVECs (exoMix). Cell activation was evaluated by measuring the protein surface expression of intracellular adhesion molecule-1 (ICAM-1) by flow cytometry. HG increased ICAM-1 expression in MM6 and monocytic exosomes from HG or BG shown similar effect in HG and BG MM6 cells. Exosomes from HUVECs increased ICAM-1 expression in MM6 cells, incubated under HG or BG, while also exosomes from MM6 increased ICAM-1 expression in HUVECs incubated under HG or BG. The combination of exosomes from both cell types (exoMixHG or exoMixBG) also increased ICAM-1 expression in both type cells in most conditions. However, the exoMixBG reversed the effect of HG in both MM6 and HUVECs. Our results show that HG activated monocytes and endothelial cells and that exosomes play a role in this HG-induced cell ICAM-1 expression. We hypothesize that during DMT2, exosomes may act as a communication mechanism between monocytes and endothelial cells, inducing and maintaining activating of both cell types in the presence of high glucose.     

Vascular endothelial cells and pituitary hormone producing cells derived from embryonic stem cells therapy for hypopituitarism

The common causes of hypopituitarism today are pituitary tumors, brain damage including traumatic brain injury, subarachnoid hemorrhage, neurosurgery, irradiation, and stroke. The main mechanism of hypopituitarism is vascular and neuronal damage of the hypothalamic-pituitary axis. At present, medical treatment of hypopituitarism caused by brain damage is hormone substitute with disadvantages of side effects, high expense and a requirement for daily injections over several years.A new protocol indicates that embryonic stem cells can be efficiently induced to differentiate into vascular endothelial cells, which integrated with host cells to form chimeric vasculature. Also, the growing body of recent evidence shows that specific hormone producing cells can be differentiated from embryonic stem cells under certain conditions. Additionally, a recent study demonstrates that endocrine cells generated from embryonic stem cells could integrate into the host in vivo and have endocrine function.Therefore, we hypothesize that vascular endothelial cells and pituitary hormone producing cells derived from embryonic stem cells labeled by iron oxide nanoparticles are injected into pituitary fossa by endoscopic transsphenoidal approach, the transplanted cells might restore vascular and neuronal damage of hypothalamic-pituitary axis, cellular therapy for hypopituitarism caused by brain damage.     

Favorable proliferation and differentiation capabilities of neural precursor cells derived from rat cochlear nucleus

NSCs/NPCs could be used for Sensorineural hearing loss treatment, because of the extensive capacity for self-renewal and pluripotency. In order to isolate and identify neural precursor cells (NPCs), we established a strategy to isolate and cultivate NPCs. Immunohistochemistry, immunofluorescence, Western blotting, and electron microscopy were used to characterize the cells and compare their differentiation patterns with those of olfactory bulb and olfactory epithelium NPCs. Furthermore, NPCs from the cochlear nucleus were sustained good cell viability and cloning efficiency after cryopreservation and thawing. Finally, high capacity to differentiate into astrocytes, oligodendrocytes, and neurons of NPCs was found. In conclusion, NPCs isolated from the cochlear nucleus can proliferate and differentiate into functional neurons, which offers a potential strategy for sensorineural hearing loss treatment. In addition, the storage method developed here will benefit further exploration of NPCs.