VEGF and PlGF: two pleiotropic growth factors with distinct roles in development and homeostasis

Blood vessels are crucial for normal development and growth by providing oxygen and nutrients. As shown by genetic targeting studies in mice, zebrafish and Xenopus blood vessel formation (or angiogenesis) is a multistep process, which is highly dependent on angiogenic growth factors such as VEGF, the founding member of the VEGF family. VEGF binds to the tyrosine kinase receptors VEGFR-1 and VEGFR-2, and loss of VEGF or its receptors results in abnormal angiogenesis and lethality during development. In contrast, PlGF, another member of this family, binds only to VEGFR-1, and appears to be crucial exclusively for pathological angiogenesis in the adult. However, the expression of VEGFR-1 and VEGFR-2 on non-vascular cells suggests additional biological properties for these growth factors. Indeed, the VEGF family and its receptors determine development and homeostasis of many organs, including the respiratory, skeletal, hematopoietic, nervous, renal and reproductive system, independent of their vascular role. These new insights broaden the activity spectrum of these "angiogenic" growth factors, and may have therapeutic implications when using these growth factors for vascular and/or non-vascular purposes.     

Endothelial-pericyte interactions in angiogenesis

It takes two to make blood vessels—endothelial cells and pericytes. While the endothelial cells are the better characterized of the two, pericytes are now coming into focus as important regulators of angiogenesis and blood vessel function, and as potential drug targets. However, pericytes are still surrounded by much controversy. They are difficult to define, they constitute a heterogeneous population of cells, and their ontogeny is not well understood. They are plastic and have the capacity to differentiate into other mesenchymal cell types, such as smooth muscle cells, fibroblasts and osteoblasts. Recent interest in pericytes also stems from their potential involvement in diseases such as diabetic microangiopathy, tissue fibrosis, cancer, atherosclerosis and Alzheimer's disease. The present review focuses on the role of pericytes in physiological angiogenesis. The currently favored view states that the initial endothelial tubes form without pericyte contact, and that subsequent acquisition of pericyte coverage leads to vessel remodeling, maturation and stabilization. Improved means of identifying and visualizing pericytes now challenge this view and show that high numbers of pericytes invest in actively sprouting and remodeling vessels. Genetic data demonstrate the critical importance of pericytes for vascular morphogenesis and function, and imply specific roles for the cell type in various aspects of angiogenesis.The images were captured using a Leica confocal microscope, the purchase of which was made possible though a generous grant from the IngaBritt and Arne Lundberg's Research Foundation     

Somatostatin suppresses ghrelin secretion from the rat stomach

Ghrelin is an acylated peptide that stimulates food intake and the secretion of growth hormone. While ghrelin is predominantly synthesized in a subset of endocrine cells in the oxyntic gland of the human and rat stomach, the mechanism regulating ghrelin secretion remains unknown. Somatostatin, a peptide produced in the gastric oxyntic mucosa, is known to suppress secretion of several gastrointestinal peptides in a paracrine fashion. By double immunohistochemistry, we demonstrated that somatostatin-immunoreactive cells contact ghrelin-immunoreactive cells. A single intravenous injection of somatostatin reduced the systemic plasma concentration of ghrelin in rats. Continuous infusion of somatostatin into the gastric artery of the vascularly perfused rat stomach suppressed ghrelin secretion in both dose- and time-dependent manner. These findings indicate that ghrelin secretion from the stomach is regulated by gastric somatostatin.     

A molecular analysis of matrix remodeling and angiogenesis during long bone development

The replacement of cartilage by bone is the net result of genetic programs that control chondrocyte differentiation, matrix degradation, and bone formation. Disruptions in the rate, timing, or duration of chondrocyte proliferation and differentiation result in shortened, misshapen skeletal elements. In the majority of these skeletal disruptions, vascular invasion of the elements is also perturbed. Our hypothesis is that the processes involved in endochondral ossification are synchronized via the vasculature. The purpose of this study was to examine carefully the events of vascular invasion and matrix degradation in the context of chondrocyte differentiation and bone formation. Here, we have produced a ‘molecular map’ of the initial vascularization of the developing skeleton that provides a framework in which to interpret a wide range of fetal skeletal malformations, disruptions, and dysplasias.     

Dementia,the fate of brain? Neuropathological point of viewLe destin du cerveau ? Un point de vue neuropathologique sur les démences.

The prevalence of dementia dramatically increases during ageing, and this puts a serious strain on the optimism brought by the continuous increase in life expectancy observed in most industrialised countries. Diseases that produce dementia are numerous, and the cognitive deficit results from lesions of various regions and from different mechanisms. This modulates the possible prediction, prevention and cure of dementia. Emphasis is put on the necessity of, and prerequisite for, efficient research in the field of dementia. Three paradigmatic dementing disorders are reviewed. Subacute spongiform encephalopathies (prion diseases) constitute a biological enigma and a public health concern. In Alzheimer's disease and vascular or mixed dementia, the clinical diagnosis is still imperfect, and this hinders research. Distinguishing and accurately identifying the various types of dementia is essential for understanding their mechanism and for developing efficient therapeutic strategies, preventive and curative. For such objectives, the study of human brain tissue will remain mandatory until non-invasive markers and additional models are available. Ethical reasons banish the use of cerebral biopsy and favour the promotion of autopsy.     

Tetrahydrobiopterin improves vascular endothelial function in ovariectomized rats

The goal of the present study is to investigate the role of tetrahydrobiopterin (BH4) in the vascular response in ovariectomized rats. Rats were randomly assigned to two groups: (1) sham group: sham-operated female rats, and (2) Ovx group: rats were ovariectomized. Our results have shown that the plasma 17 beta-estradiol levels in the Ovx group at the end of the experiment were significantly lower than in the sham group. Vasoreactivity assessed with intact aortic rings indicated that the phenylephrine-induced vasocontractile response to aortic rings from the Ovx group was greater than that of the sham group. In contrast, the vasodilator responses to acetylcholine and L-arginine (L-Arg) in the sham group were significantly greater than in the Ovx group. Differences in vasoreactivity in denuded aorta between the two groups were not noted. Moreover, exogenous BH4 significantly restored L-Arg-induced vasodilator responses in the Ovx group. However, this improvement effect was not found in the sham group. In addition, there were significant increases in superoxide anion production in aortic tissue and significant decreases in plasma nitric oxide levels in the Ovx group. Furthermore, BH4 contents in the aorta in the Ovx group were significantly decreased compared with the sham group. In conclusion, the present study demonstrates that the impairment of vascular reactivity was found in the ovariectomized rats. The possible mechanism of this defect may have resulted from the deficiency of available BH4. Thus, this study may provide a novel therapeutic strategy for the treatment of postmenopausal cardiovascular disorders.     

Metalloprotease inhibitor blocks angiotensin II-induced migration through inhibition of epidermal growth factor receptor transactivation

In vascular smooth muscle cells (VSMCs), angiotensin II (AngII) induces transactivation of the EGF receptor (EGFR) which involves a metalloprotease that stimulates processing of heparin-binding EGF from its precursor. However, the identity and pharmacological sensitivity of the metalloprotease remain unclear. Here, we screened the effects of several metalloprotease inhibitors on AngII-induced EGFR transactivation in VSMCs. We found that an N-phenylsulfonyl-hydroxamic acid derivative [2R-[(4-biphenylsulfonyl)amino]-N-hydroxy-3-phenylpropinamide] (BiPS), previously known as matrix metalloprotease (MMP)-2/9 inhibitor, markedly inhibited AngII-induced EGFR transactivation, whereas the MMP-2 or -9 inhibition by other MMP inhibitors failed to block the transactivation. BiPS markedly inhibited AngII-induced ERK activation and protein synthesis without affecting AngII-induced intracellular Ca2+ elevation. VSMC migration induced by AngII was also inhibited not only by an EGFR inhibitor but also by BiPS. Thus, BiPS is a specific candidate to block AngII-induced EGFR transactivation and subsequent growth and migration of VSMCs, suggesting its potency to prevent vascular remodeling.