Vascular Growth Factor Production Research Articles

Luteinizing hormone receptor promotes angiogenesis in ovarian endothelial cells of Macaca fascicularis and Homo sapiens†.

Angiogenesis within the ovarian follicle is an important component of ovulation. New capillary growth is initiated by the ovulatory surge of luteinizing hormone (LH), and angiogenesis is well underway at the time of follicle rupture. LH-stimulated follicular production of vascular growth factors has been shown to promote new capillary formation in the ovulatory follicle. The possibility that LH acts directly on ovarian endothelial cells to promote ovulatory angiogenesis has not been addressed. For these studies, ovaries containing ovulatory follicles were obtained from cynomolgus macaques and used for histological examination of ovarian vascular endothelial cells, and monkey ovarian microvascular endothelial cells (mOMECs) were enriched from ovulatory follicles for in vitro studies. mOMECs expressed LHCGR mRNA and protein, and immunostaining confirmed LHCGR protein in endothelial cells of ovulatory follicles in vivo. Human chorionic gonadotropin (hCG), a ligand for LHCGR, increased mOMEC proliferation, migration and capillary-like sprout formation in vitro. Treatment of mOMECs with hCG increased cAMP, a common intracellular signal generated by LHCGR activation. The cAMP analog dibutyryl cAMP increased mOMEC proliferation in the absence of hCG. Both the protein kinase A (PKA) inhibitor H89 and the phospholipase C (PLC) inhibitor U73122 blocked hCG-stimulated mOMEC proliferation, suggesting that multiple G-proteins may mediate LHCGR action. Human ovarian microvascular endothelial cells (hOMECs) enriched from ovarian aspirates obtained from healthy oocyte donors also expressed LHCGR. hOMECs also migrated and proliferated in response to hCG. Overall, these findings indicate that the LH surge may directly activate ovarian endothelial cells to stimulate angiogenesis of the ovulatory follicle.

Polycythemia Vera as a Predisposing Factor for Aortic Stenosis: Prevalence and Correlation with Blood Cells Count and Mutational Status

The association between Polycythemia Vera (PV) and thrombosis is multi-factorial involving the complex interaction between activated leukocytes, platelets and endothelium. Recent reports have postulated that PV patients may over express adhesive molecules on red cell surface, likely by JAK2 mutation (Wautier M et al. Blood. 2007; 110(3):894–901). This process activates endothelium with production of vascular growth factors and other mechanisms leading to atherosclerosis. Aortic Stenosis (AS) is the commonest valvular heart disease in western countries; its pathogenesis is mainly related to a degenerative process sharing many characteristics with atherosclerosis. At the present is not known whether patients with PV are at high risk of developing AS.Objective of the study. We perform a case-control study for evaluating rate of AS and its correlation with blood cells count and mutational status in patients with PV.Materials and methods. Prevalence of AS among PV patients have been compared with control patients matched for age, cardiovascular risk factors (hypertension, hyperlipidemia, diabetes, smoke and alcohol abuse) and coexisting cardiac diseases (i.e. heart failure). Diagnosis of PV has been posted accordingly to PVSG criteria. Diagnosis and severity of AS has been posted by echocardiography: stenosis with a valve area <1.0 cm2 has been considered severe.Results. Over a period of 18 months we recruited 43 PV patients (28 males and 15 females) and 74 controls. No differences were found in regard of the above cited characteristics; median age was 66.7 among PV patients and 68.2 among controls. The average duration of PV was 5.7 years with an average follow-up of 2.5 years. Most of the PV patients were on antiplatelet/anticoagulant therapy (27/43, 62.7%) and have been treated with cytoreductive therapy. Twelve (27.9%) had a thrombotic event before PV diagnosis; 4 (9.3%) developed thrombosis during the follow-up (median 1.3 years). A moderate/severe AS was found in 11 PV patients (25.6%) in comparison to 4 (5.4%) in control group (P= 0.023), thus giving a Relative Risk of 4.7. Among PV patients, the multivariate analysis did not show any correlation regarding JAK2 V617F mutational status, duration of disease, previous thrombosis, cytoreductive therapy and other common cardiovascular factors. Comparison of laboratory findings is reported in Table 1; a not significant trend was demonstrated in favor of patients with elevated hematocrit (>55%).Conclusions. Our study clearly shows that PV patients carry a fourfold risk of developing AS, without a clear association with blood cell alterations or previous thrombosis. Whether high prevalence of AS may be related to expression of adhesive molecules on red cells or altered share stress is currently under investigation.Table 1. Comparison of laboratory findings between PV patients with and without ASLaboratory parameter*PV patients with AS (11)PV patients without AS (32)Relative RiskP valueWhite blood cell×109/L (mean± SD)9520 ± 123012.900 ± 21200.73.078Hemoglobin, g/dL (mean ± SD)17.5 ± 1.317.1 ± 1.21.02.088Hematocrit, % (mean ± SD)56.2 ± 0.651.1 ± 0.81.10.06Platelets × 109/L(mean ± SD)415.9 ± 43353 ± 551.10.76JAK2 V617F, n/N (%)11/11 (100%)31/32 (97%)--*At diagnosisLegend: PV (Polycythemia Vera), AS (Aortic Stenosis)

Gene targeting of VEGF-A in thymus epithelium disrupts thymus blood vessel architecture

The thymus harbors an organ-typical dense network of branching and anastomosing blood vessels. To address the molecular basis for morphogenesis of this thymus-specific vascular pattern, we have inactivated a key vascular growth factor, VEGF-A, in thymus epithelial cells (TECs). Both Vegf-A alleles were deleted in TECs by a complementation strategy termed nude mouse [mutated in the transcription factor Foxn1 (forkhead box N1)] blastocyst complementation. Injection of Foxn1(+/+) ES cells into Foxn1(nu/nu) blastocysts reconstituted a functional thymus. By dissecting thymus stromal cell subsets, we have defined, in addition to medullary TECs (mTECs) and cortical TECs (cTECs), another prominent stromal cell subset designated cortical mesenchymal cells (cMes). In chimeric thymi, mTECs and cTECs but not cMes were exclusively ES cell-derived. According to this distinct origin, the Vegf-A gene was deleted in mTECs and cTECs, whereas cMes still expressed Vegf-A. This genetic mosaic was associated with hypovascularization and disruption of the organ-typical network of vascular arcades. Thus, vascular growth factor production by TECs is required for normal thymus vascular architecture. These experiments provide insights into Foxn1-dependent and Foxn1-independent stromal cell development and demonstrate the value of this chimeric approach to analyzing gene function in thymus epithelium.

Vascular Growth Factor Expression in a Rat Model of Severe Limb Ischemia

Background. In ischemic tissue hypoxia induces production of vascular growth factors, especially VEGF, which initiate local angiogenesis. Collateralization—or arteriogenesis—occurs at a distance from the ischemic tissue and depends on different growth factors such as FGF-2. A spatial discrepancy in endogenous growth factor production in limb ischemia may have implications for therapeutic angiogenesis. The present study elucidates if such spatial and temporal variation occurs. Materials and methods. A two-staged procedure was performed to generate severe long-lasting limb ischemia in 60 rats. At 1, 7, 28, and 56 days, subgroups were subjected to perfusion assessment with laser Doppler imaging and angiography. Muscle samples and foot skin were gathered to measure growth factor expression and signs of angiogenesis using immunohistochemistry. Results. There was an early twofold increase ( P < 0.05) in both VEGF and FGF-2 levels in distal muscle from the ischemic leg, but no significant rise in the thigh. The concentrations decreased over time with an exception for VEGF in soleus and FGF-2 in anterior tibial muscle, which remained high. An increased capillarity was noted ( P < 0.05) in soleus after 28 days, and the number of BrdU-positive ECs was elevated in all ischemic samples at 56 days. Collateral arteries were observed on the angiograms after 7 days. Conclusions. The results suggest that in limb ischemia any major increase in vascular growth factor production is limited to ischemic tissue. The spatial and temporal distribution patterns of growth factor production are complex and to a great extent influenced by inflammation.