Vascular endothelial growth factor (VEGF) - key factor in normal and pathological angiogenesis.

Vascular endothelial growth factor (VEGF) represents a growth factor with important pro-angiogenic activity, having a mitogenic and an anti-apoptotic effect on endothelial cells, increasing the vascular permeability, promoting cell migration, etc. Due to these effects, it actively contributes in regulating the normal and pathological angiogenic processes. In humans, the VEGF family is composed of several members: VEGF-A (which has different isoforms), VEGF-B, VEGF-C, VEGF-D, VEGF-E (viral VEGF), VEGF-F (snake venom VEGF), placenta growth factor (PlGF), and, recently, to this family has been added endocrine gland-derived vascular endothelial growth factor (EG-VEGF). VEGF binds to tyrosine kinase cell receptors (VEGFRs): VEGFR-1 [Fms-like tyrosine kinase 1 (Flt-1)], VEGFR-2 [kinase insert domain receptor (KDR) in human; fetal liver kinase 1 (Flk-1) in mouse] and VEGFR-3 [Fms-like tyrosine kinase 4 (Flt-4)]. While VEGFR-1 and VEGFR-2 are expressed predominantly on vascular endothelial cells, VEGFR-3 is expressed especially on lymphatic endothelial cells. VEGFR-2 has the strongest pro-angiogenic activity and a higher tyrosine kinase activity than VEGFR-1. Endothelial cells also express co-receptors, such as neuropilin-1 (NP-1) and neuropilin-2 (NP-2), which modulate tyrosine kinase receptor activity. Both VEGF and VEGFRs are expressed not only on endothelial cells, but also on non-endothelial cells. This article aims to highlight the most recent data referring to the VEGF family and its receptors, as well as its implications in the angiogenesis process. At present, blocking angiogenesis in cancer or in other pathological processes, using anti-VEGF and anti-VEGFRs therapies, is considered to be extremely important.

Highlighting the R1 and R2 VEGF receptors in placentas resulting from normal development pregnancies and from pregnancies complicated by preeclampsia.

Preeclampsia (PE), a pathological entity characterized by hypertension and pregnancy-related proteinuria, is a medical condition of incompletely known etiopathogenesis. Placental defects and placental angiogenesis may be a cause of this condition. The main factor that controls angiogenesis in the early stages of placental development is vascular endothelial growth factor A (VEGF-A) and its two receptors, namely VEGFR-1 and VEGFR-2. This study analyzed the immunohistochemical (IHC) expression of the two VEGF receptors, R1 and R2, in pregnancies complicated by PE compared to pregnancies with a normal evolution. The pregnancies included into the study for the harvesting of placental tissue to be microscopically analyzed were divided into two groups: the group of physiological pregnancies (22 pregnancies) and the group of pregnancies complicated by preeclampsia (13 pregnancies). For the microscopic analysis, we used the Hematoxylin-Eosin (HE), Masson's trichrome and IHC stainings. The microscopic aspects of HE and Masson's trichrome stainings most commonly found in normal development pregnancies underlie the normal process of placental senescence. In the case of pregnancies complicated by PE, the microscopic analysis of the placentas revealed fibrinoid necrosis of the vascular wall, lipid-loaded endothelial cells, diffuse trophoblastic hypertrophy, microinfarctions, calcification areas, fibrin deposits, vascular-syncytial membrane surface reduction, basement membrane thickening. According to the established marker intensity score, the VEGFR-1 and VEGFR-2 receptors were more pronounced in the placentas resulting from pregnancies complicated by preeclampsia. The present study brings arguments that support the major regulatory role of VEGF-A and of the two receptors in the normal or pathological angiogenesis in the placenta, and implicitly in the pathogenesis of preeclampsia. Further studies are needed for a more comprehensive analysis of the stages in which these factors cause alteration of the placental angiogenesis and vasculogenesis processes, so that they can intervene effectively in the treatment or prevention of this disease.