Angiogenesis during human extraembryonic development involves the spatiotemporal control of PDGF ligand and receptor gene expression

Development ◽  
1991 ◽  
Vol 113 (3) ◽  
pp. 749-754 ◽  
Author(s):  
L. Holmgren ◽  
A. Glaser ◽  
S. Pfeifer-Ohlsson ◽  
R. Ohlsson

We have examined the role of platelet-derived growth factor (PDGF) ligand and receptor genes in the angiogenic process of the developing human placenta. In situ hybridization analysis of first trimester placentae showed that most microcapillary endothelial cells coexpress the PDGF-B and PDGF beta-receptor genes. This observation indicates that PDGF-B may participate in placental angiogenesis by forming autostimulatory loops in capillary endothelial cells to promote cell proliferation. Endothelial cells of macro blood vessels maintained high PDGF-B expression, whereas PDGF beta-receptor mRNA was not detectable. In contrast, PDGF beta-receptor mRNA was readily detectable in fibroblast-like cells and smooth muscle cells in the surrounding intima of intermediate and macro blood vessels. Taken together, these data suggest that the PDGF-B signalling pathway appears to switch from an autocrine to a paracrine mechanism to stimulate growth of surrounding PDGF beta-receptor-positive mesenchymal stromal cells. Smooth muscle cells of the blood vessel intima also expressed the PDGF-A gene, the protein product of which is presumably targeted to the fibroblast-like cells of the mesenchymal stroma as these cells were the only ones expressing the PDGF alpha-receptor. PDGF-A expression was also detected in columnar cytotrophoblasts where it may have a potential role in stimulating mesenchymal cell growth at the base of the growing placental villi. We discuss the possibility that the regulation of the PDGF-B and beta-receptor gene expression might represent the potential targets for primary angiogenic factors.

Circulation ◽  
2000 ◽  
Vol 102 (15) ◽  
pp. 1828-1833 ◽  
Author(s):  
Georg Nickenig ◽  
Kerstin Strehlow ◽  
Sven Wassmann ◽  
Anselm T. Bäumer ◽  
Katja Albory ◽  
...  

1987 ◽  
Author(s):  
J L Gordon

ATP, although known mainly as an intracellular energy source, is also capable of acting extracellularly as a vasoactive agent of great potency, at concentrations around lμM or less. ADP is approximately equipotent with ATP in its actions on extracellular receptors in the vasculature.ATP and ADP can arise extracellularly through release from the cytoplasm of cellsexposed to damaging stimuli or by degranulation of platelets. The concentration of the nucleotides in the cytoplasm of most cells (including vascular endothelial and smooth muscle cells) is more than ImM, and the concentration in the dense storage granules of platelets approaches 1M. Thus, there is potential for very high localised concentrations of ATP and ADP in the plasma following platelet degranulation or damageto cells of the vessel well. Release from vascular endothelial and smooth muscle cells can occur with no loss of cell viability or leakage of cytoplasmic proteins.The vasoactivity of ATP and ADP is mediated via P2 purinoceptors. Vasodilation can be induced through the release of EDRF from endothelial cells or through stimulation of PGI2 production (PGI2 is a vasodilator in many, althoughnot all, arterial beds). Purinoceptor-mediated prostacyclin production can be stimulated from perfused vascular beds (e.g. theheart andthe lung), from isolated blood vessels or from cultured endothelial cells.In some blood vessels, purinoceptor-mediated vasoconstriction can be induced by direct actionon the vascular smooth muscle cells. The receptors responsible are sub-classified as P2X (which induce vasoconstriction) and P2Y (whichinduce vasodilation). The P2Y purinoceptor that mediates EDRF production is very similar to that which is responsible for PGI2 production, although there are some intriguing differences inthe potency of ATP analogs at stimulating these two responses, even on the same cells. The intracellular mechanisms responsible have not yet been fully elucidated, but it appears that elevation of intracellular calcium is likely to play a causal role.Adenosine, which is the product of ATP and ADP metabolism by nucleotidases, can also induce vasodilation in many blood vessels, acting via P1] purinoceptors on the smooth muscle cells, but its potency is often less than that of ATP and ADP.The fate of adenine nucleotides released into the plasma is determined by ectonucleotidases on the luminal surface of the endothelial cells, not by enzymes in the blood itself (the half-life of ATP in samples of blood or plasma is many minutes, while in the microcirculation the half-life isless than one second). Endothelial ectonucleotidases have been detected in several vascular beds, and many of their characteristics are now known. These enzymes are distinct entities from the P2 purinoceptors on endothelium, as shown by the marked differences in potency of several ATP analogs as P2 receptor stimulants and as substrates for the nucleotidases.In summary, vascular endothelial and smooth muscle cells respond to extracellularATP and ADP, and can also metabolise thesenucleotides extracellularly by ectonucleotidases. In addition, ATP and ADP can be selectively released from the cells of the vessel wall and from activated platelets. Thus, the endothelial pericellular environment can be the site of complex interactions by which vascular tone is regulated through the release, actions and metabolism ofextracellular nucleotides.


2001 ◽  
Vol 86 (07) ◽  
pp. 404-412 ◽  
Author(s):  
Houshang Monajemi ◽  
E. Karin Arkenbout ◽  
Hans Pannekoek

SummaryIt is conceivable that the extent and spatio-temperal expression of dozens or even a few hundred genes are significantly altered during the development and progression of atherosclerosis as compared to normal circumstances. Differential gene expression in vascular cells and in blood cells, due to gene-gene and gene-environment interactions can be considered the molecular basis for this disease. To comprehend the coherence of the complex genetic response to systemic and local atherosclerotic challenges, one needs accessible high through-put technologies to analyze a panel of differentially expressed genes and to describe the interactions between and among their gene products. Fortunately, new technologies have been developed which allow a complete inventory of differential gene expression, i.e. DD/RT-PCR, SAGE and DNA micro-array. The initial data on the application of these technologies in cardiovascular research are now being reported. This review summarizes a number of key observations. Special attention is paid to a few central transcription factors which are differentially expressed in endothelial cells, smooth muscle cells or monocytes/ macrophages. Recent data on the role of nuclear factor- B (NF-κB) and peroxisome proliferation-activating receptors (PPARs) are discussed. Like the PPARs, the NGFI-B subfamily of orphan receptors (TR3, MINOR and NOT) also belongs to the steroid/thryroid hormone receptor superfamily of transcription factors. We report that this subfamily is specifically induced in a sub-population of neointimal smooth muscle cells. Furthermore, intriguing new data implicating the Sp/XKLF family of transcription factors in cell-cell communication and maintenance of the atherogenic phenotype are mentioned. A member of the Sp/XKLF family, the shear stress-regulated lung Krüppel-like factor (LKLF) is speculated to be instrumental for the communication between endothelial cells and smooth muscle cells. Taken together, the expectation is that the fundamental knowledge obtained on atherogenesis and the data that will be acquired during the coming decade with the new, powerful high through-put methodologies will lead to novel modalities to treat patients suffering from cardiovascular disease. In view of the phenotypic changes of vascular and blood-borne cells during atherogenesis, therapeutic interventions likely will focus on reversal of an acquired phenotype by gene therapy approach or by using specific drugs which interfere with aberrant gene expression.


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