Two new applications in the study of angiogenesis the CAM assay: Acellular scaffolds and organoids.

The chick embryo chorioallantoic membrane (CAM) is a rich vascularized extraembryonic membrane that is commonly used as an in vivo experimental model to study molecules with angiogenic and anti-angiogenic activity, tumor growth and metastasis. Among other applications of the CAM assay, more recently this assay has been used for the study of acellular scaffolds and of organoids, and of their angiogenic capacity. The aim of this review article is to summarize the literature data concerning these two new applications of the CAM assay and to underline the advantages of this assay.

BML-111, the lipoxin A4 agonist, modulates VEGF or CoCl2-induced migration, angiogenesis and permeability in tumor-derived endothelial cells.

Tumor angiogenesis plays a vital role in carcinogenesis, cancer progression, and metastasis. Lipoxin A4 (LXA4) is an endogenously-produced family of effective anti-inflammatory with a potent inhibitory effect on angiogenesis. However, BML-111, a LXA4 agonist, its governing tumor-derived endothelial cells (Td-EC) mechanisms remain unknown. In the present study, we utilized VEGF or CoCl2 to mimic tumor microenvironment in vitro to study the effect of BML-111 on angiogenesis and permeability of Td-EC, and preliminarily explore its specific mechanism. Data suggested that BML-111 inhibited viability, migration and angiogenesis in VEGF or CoCl2-treated Td-EC by modulating MMP2/9-TIMP1, and decreasing the production of HIF-1α and COX-2 level. In addition, we observed that BML-111 inhibited Td-EC permeability induced by VEGF or CoCl2, through the stabilization of VE-cadherin/ß-catenin-dependent adherens junctions and TRPC1 pathway. Nevertheless, these effects could be blocked by BOC-2 which was the specific inhibitor of FPR2/ALX (the receptor of LXA4).These results suggest that BML-111 may have inhibitory effects on VEGF or CoCl2-induced migration, angiogenesis and permeability in tumor-derived endothelial cells.

Insights into the dual role of angiogenesis following stroke.

Stroke remains a major cause of serious disability due to the brain's limited capacity to regenerate. Current treatments focus on acute recanalization of the occluded blood vessels; however, currently there are no approved therapy options to regenerate neural circuits and reduce stroke-related disability. To promote recovery, therapeutic angiogenesis has been proposed as a promising target. Although restoration of blood vessels providing oxygen and nutrients to the peri-infarct regions may be beneficial, newly generated capillaries may also carry pathophysiological risk factors that need to be considered. One major concern are adverse effects including edema formation and haemorrhagic transformation due to the comprised endothelial barrier function during vascular remodelling. This brief opinion article will discuss the challenges and the newest advancements of angiogenesis as a therapeutic strategy for ischemic stroke.

The Molecular Mechanism of EPO Regulates the Angiogenesis after Cerebral Ischemia through AMPK-KLF2 Signaling Pathway.

OBJECTIVE: In this study, the molecular mechanism by which EPO regulates the angiogenesis after cerebral ischemia through AMPK-KLF2 signaling pathway was investigated. METHODS: Sixty healthy, male, C57BL/6 mice were randomly divided into three groups of 20 mice: a sham group, the middle cerebral artery occlusion (MCAO) group, and a MCAO+EPO treatment group. The MCAO model was established using a modified ZeaLonga method. Mice in the EPO treatment group were injected with EPO immediately after reperfusion (5000 IU/kg), and EPO was injected the following day. The number of mouse deaths and neurologic function scores were recorded during the experiment. On day 7 after cerebral ischemia, brain tissue proteins were extracted. The following proteins expressions were detected by western blot assay: EPO, vascular endothelial growth factor (VEGE), vascular endothelial growth factor receptor (KDR), adenosine activated protein kinase (AMPK), and alpha HIF-1α alpha (HIF-1α), KLF2 and nitric oxide synthase (eNOS). RESULTS: Compared with the MCAO group, the survival rate of mice in the EPO group was significantly improved and neurological function was significantly improved (P < 0.01). Western blot results showed that the content of EPO in brain tissue in MCAO group significantly increased compared with sham group. The content of EPO in the brain tissue of mice in the MCAO+EPO treatment group was significantly higher than in that of the MCAO group, which indicates that EPO increased the content of EPO in mouse brain tissue. Compared with the sham group, the protein expression of vascular endothelial growth factor (VEGE) and its receptor (KDR) in brain tissue of the MCAO group significantly decreased. However, the protein expression of VEGE and its receptor KDR in brain tissue of rats treated with MCAO+EPO was significantly higher than in that of the MCAO group. Thus, in this study, EPO was associated with vascular endothelial differentiation after cerebral ischemia in mice. The results of AMPK and KLF2 showed that the expression levels of AMPK and KLF2 in brain tissues of MCAO group mice significantly decreased compared with the sham group. However, the expression levels of AMPK and KLF2 in brain tissues of mice treated with MCAO+EPO were significantly higher than those in the MCAO group. Thus, EPO can activate AMPK and upregulate the expression of the transcription factor KLF2. The protein expression of HIF-1α in the brain tissue of mice in the MCAO group significantly increased compared with the sham group. However, the expression of HIF-1α in mice brain tissues in the MCAO+EPO treatment group was significantly lower than in that of the MCAO group, indicating that EPO was involved in regulating HIF-1α expression. The eNOS results showed that, compared with Sham group, the protein expression of eNOS in brain tissue of MCAO group mice significantly decreased. In the MCAO+EPO treatment group, the protein expression of eNOS was significantly higher in the brain tissue of the mice than in that of the MCAO group, indicating that EPO was involved in the synthesis of NO and promoted the angiogenesis. CONCLUSION: EPO promotes VEGE and its receptor (KDR) expression and participates in the regulation of HIF-1α and eNOS protein expression through the activation of AMPK-KLF2 signaling pathways to promote new vascular development after cerebral ischemia.

Characterization of a Porcine Model for Von Willebrand Disease Type 1 and 3 Regarding Expression of Angiogenic Mediators in the Nonpregnant Female Reproductive Tract.

Von Willebrand disease (VWD), a blood coagulation disorder, is also known to cause angiodysplasia. Hitherto, no animal model has been found with angiodysplasia that can be studied in vivo. In addition, VWD patients tend to have a higher incidence of miscarriages for reasons unknown. Thus, we aimed to examine the influence of von Willebrand factor (VWF) on the female reproductive tract histology and the expression and distribution of angiogenic factors in a porcine model for VWD types 1 and 3. The disease-causing tandem duplication within the VWF gene occurred naturally in these pigs, making them a rare and valuable model. Reproductive organs of 6 animals (2 of each mutant genotype and 2 wildtype (WT) animals) were harvested. Genotype plus phenotype were confirmed. Several angiogenic factors were chosen for possible connections to VWF and analyzed alongside VWF by immunohistochemistry and quantitative gene expression studies. VWD type 3 animals showed angiodysplasia in the uterus and shifting of integrin αVß3 from the apical membrane of uterine epithelium to the cytoplasm accompanied by increased vascular endothelial growth factor (VEGF) expression. Varying staining patterns for angiopoietin (Ang)-2 were observed among the genotypes. As compared with WT, the ovaries of the VWD type 3 animals showed decreased gene expression of ANG2 and increased gene expression of TIE (tyrosine kinase with immunoglobulin and epidermal growth factor homology domains) 2, with some differences in the ANG/TIE-system among the mutant genotypes. In conclusion, severely reduced VWF seems to evoke angiodysplasia in the porcine uterus. Varying distribution and expression of angiogenic factors suggest that this large animal model is promising for investigation of influence of VWF on angiogenesis in larger groups.

Capillary rarefaction and altered renal development: the imbalance between pro- and anti-angiogenic factors in response to angiotensin II inhibition in the developing rat kidney.

Proper and timely assembly of the kidney vasculature with their respective nephrons is crucial during normal kidney development. In this study, we investigated the effects of enalapril (angiotensin-converting enzyme inhibitor) on angiogenesis-related gene expression and microvascular endothelium related to glomeular and tubular changes in the neonatal rat kidney. Enalapril-treated rats had higher tubular injury scores and lower glomerular maturity grades than those of untreated rats. In the enalapril-treated group, intrarenal angiopoietin-2, Tie-2, and thrombospondin-1 protein expression increased, whereas intrarenal angiopoietin-1 protein expression decreased. JG12-positive glomerular and peritubular capillary staining was reduced in the enalapril-treated rat kidney. The number of JG12-positive capillary endothelial cells was directly correlated with glomerular maturation grade and was inversely related with the tubular injury. Our findings suggest the imbalance between pro- and anti-angiogenic factors may be implicated in the loss of capillaries in associated with impaired nephrogenesis after angiotensin II blockade in the developing rat kidney.

5,6-dehydrokawain from the rhizome of Alpinia mutica Roxb. induced proangiogenic tumour-derived VEGF of HT-29 colorectal cancer.

Vascular endothelial growth factor (VEGF) is a glycoprotein vital to the regulation of vascular endothelial cells proliferation, migration and angiogenesis. The expression of VEGF is required for the formation of new blood vessels critical in supplying oxygen and nutrition in the course of tumorigenesis. The present study investigated the effect of 5,6-dehydrokawain isolated from the rhizomes of Alpinia mutica on VEGF expression in vitro using HT-29 cell line. The results revealed that 5,6-dehydrokawain induced the expression of proangiogenic tumour-derived VEGF of HT-29 cells, which may explain the inability of 5,6-dehydrokawain in suppressing cancer cells proliferation.

[Quality of life in patients with lower extremity atherosclerosis during standard treatment and therapeutic angiogenesis]. / Kachestvo zhizni u patsientov s aterosklerozom nizhnikh konechnostei pri ispol'zovanii standartnogo lecheniia i terapevticheskogo angiogeneza.

AIM: To compare the impact of standard conservative treatment (SCT) and its combination with therapeutic angiogenesis for 3 to 5 years on quality of life in patients with Stage II (according to the classification developed by A.V. Pokrovsky-Fontaine) lower extremity atherosclerosis. SUBJECTS AND METHODS: 92 patients (69 men and 23 women) (mean age 65.2±7.7 years) were examined and divided into 2 groups of 46 people each. Only SCT (statins at an individually adjusted dose, antiaggregants, and graded exercise walking 3 to 5 km daily were used in Group 1; while Group 2 received SCT in combination with double injection of a plasmid-based VEGF165 gene drug (1.2 mg) into the ischemic limb muscles. The Russian version of the standard SF-36 questionnaire was applied; pain-free walking distances were measured before treatment and then every year; limb preservation and survival rates were determined in the patients. RESULTS: It was determined that standard treatment did not significantly affect patients' quality of life throughout the follow-up period. Addition of gene therapy leads to a significant improvement in both physical (p=0.00001) and psychological (p=0.00002) health components just in the first year of the follow-up. This is achieved through a significant (500%) increase in the average leg pain-free walking distance; p=0.007). CONCLUSION: The obtained result is consistently high throughout the subsequent period. There was no statistically significant difference in survival rates between the groups; limb preservation remained comparable.

Angiomodulators in cancer therapy: New perspectives.

The formation of new blood vessels plays a crucial for the development and progression of pathophysiological changes associated with a variety of disorders, including carcinogenesis. Angiogenesis inhibitors (anti-angiogenics) are an important part of treatment for some types of cancer. Some natural products isolated from marine invertebrates have revealed antiangiogenic activities, which are diverse in structure and mechanisms of action. Many preclinical studies have generated new models for further modification and optimization of anti-angiogenic substances, and new information for mechanistic studies and new anti-cancer drug candidates for clinical practice. Moreover, in the last decade it has become apparent that galectins are important regulators of tumor angiogenesis, as well as microRNA. MicroRNAs have been validated to modulate endothelial cell migration or endothelial tube organization. In the present review we summarize the current knowledge regarding the role of marine-derived natural products, galectins and microRNAs in tumor angiogenesis.

Quercetin Attenuates Cell Survival, Inflammation, and Angiogenesis via Modulation of AKT Signaling in Murine T-Cell Lymphoma.

AKT signaling is important to maintaining normal physiology. Hyperactivation of AKT signaling is frequent in cancer, which maintains a high oxidative state in a tumor microenvironment that is needed for tumor adaptation. Therefore, antioxidants are proposed to exhibit anticancer properties by interfering with the tumor microenvironment. Quercetin is an ubiquitous bioactive antioxidant rich in vegetables and beverages. The present study aimed to analyze cancer preventive property of quercetin in ascite cells of Dalton's lymphoma-bearing mice. Protein level was determined by Western blotting. Nitric oxide (NO) level was estimated spectrophotometrically using Griess reagent. Results show downregulation in phosphorylation of AKT and PDK1 by quercetin, which was consistent with decreased phosphorylation of downstream survival factors such as BAD, GSK-3ß, mTOR, and IkBα. Further, quercetin attenuated the levels of angiogenic factor VEGF-A and inflammatory enzymes COX-2 and iNOS as well as NO levels, whereas it increased the levels of phosphatase PTEN. Overall results suggest that quercetin modulates AKT signaling leading to attenuation of cell survival, inflammation, and angiogenesis in lymphoma-bearing mice.

Synthesis of MR-49, a deiodinated analog of tetraiodothyroacetic acid (tetrac), as a novel pro-angiogenesis modulator.

The tyrosine-based hormones 3,3',5-triiodo-l-thyronine (l-T3) and l-thyroxine (l-T4) that are produced by the thyroid gland control metabolic functions. Iodothyronine deiodinase enzymes convert l-T4 to l-T3, the form of thyroid hormone critical to genomic actions within cells and regulation of metabolism, and to reverse-l-T3, a hormone isoform that is largely inactive. We used tertiary amines in a study of deiodination based on derivatives of tetraiodothyroacetic acid (tetrac)-a naturally occurring derivative of l-T4-to mimic the action of the iodothyronine deiodinases and deiodination of the outer ring iodines. Deiodinated tetrac, MR-49, was found to be pro-angiogenic, with this activity exceeding that of l-T3 and l-T4 in a hemoglobin Matrigel® plug assay of angiogenesis. Tetrac is anti-angiogenic via several nongenomic pathways, and the present studies of MR-49 reveal the critical contribution of outer ring iodines to the angiogenic properties of thyroid hormone analogues, which may have utility as pro-angiogenic pharmaceuticals.

Beneficial roles of melanoma cell adhesion molecule in spinal cord transection recovery in adult zebrafish.

Melanoma cell adhesion molecule (MCAM) is a multifunctional protein involved in miscellaneous processes, including development and tumor angiogenesis. Here, spinal cord transection in adult zebrafish was used to investigate the effects of MCAM on spinal cord injury (SCI) and subsequent recovery. Expression of MCAM mRNA increased and co-localized with motoneurons in the spinal cord after SCI. With MCAM morpholino treatment, inhibition of MCAM retarded both axon regrowth and locomotor recovery in the spinal cord injured zebrafish. Furthermore, MCAM mRNA expression was also observed in fli1a:EGFP transgenic zebrafish, which specifically show labeled blood vessels. Inhibition of MCAM down-regulated the expression of angiogenesis-related factors, such as VEGFR-2, p-p38 and p-AKT, and the inflammatory factors TNF-α, IL-1ß and IL-8. Taken together, these data suggest that MCAM may have a beneficial role in the recovery from SCI, via the promotion of neurogenesis and angiogenesis. In the context of adult zebrafish spinal cord injury, we proved that Melanoma cell adhesion molecule (MCAM) is beneficial to the recovery, possibly via mechanisms of angiogenensis and inflammation. MCAM promotes angiogenesis by adjusting VEGFR-2, p-p38 and p-AKT. MCAM affects inflammatory factors such as TNF-α, IL-1ß and IL-8. Our results extend the beneficial role of MCAM in the regeneration of central nervous system.

Glucocorticoid effects on angiogenesis are associated with mTOR pathway activity.

Glucocorticoids (GC) often are administered during pregnancy, but despite their widespread use in clinical practice, it remains uncertain how GC exposure affects pro-angiogenic factors and their receptors. We investigated the effects of GC on vascular endothelial growth factor (VEGF), placental growth factor (PIGF), vascular endothelial growth factor receptor 1 (VEGFR1) and vascular endothelial growth factor receptor 2 (VEGFR2) protein and mRNA expressions and investigated the possible association of GC with the Akt/mTOR pathway. We incubated human umbilical vein endothelial cells (HUVECs) with a synthetic GC, triamcinolone acetonide (TA). TA administration caused decreased cellular and soluble VEGF and VEGFR1 protein expressions and increased soluble VEGFR2 expression. VEGF, VEGFR1 and VEGFR2 mRNA expressions were altered in a time and dose dependent manner. PIGF protein expression was unaffected by TA treatment, but PIGF mRNA expression decreased in a dose dependent manner after incubation for 48 and 72 h. Phospho-mTOR and phospho-Akt expressions were unaffected. Phospho-p70S6K and phospho-4EBP1 protein expressions and the vascular network forming capacity of HUVECs decreased in a dose dependent manner. We found that GC exert detrimental effects on angiogenesis by altering cellular and soluble angiogenic protein and mRNA levels, and vascular network forming capacities by the Akt/mTOR pathway.

Reactive oxygen species and synthetic antioxidants as angiogenesis modulators: Clinical implications.

Angiogenesis is important for normal functioning of organism and its disturbances are observed in many diseases, called angiogenesis-related states. Reactive oxygen species (ROSs) play an important role in physiology, but high level of cellular ROSs is cytotoxic and mutagenic for the cells, i.e. it can lead to oxidative stress. In this review we discuss close relationship between ROSs and angiogenesis process. Substances counteracting free radicals or their action and oxidative stress are known as antioxidants. We postulate that antioxidants, by affecting angiogenesis, may modulate therapy results in the case of angiogenesis-related disease. Herein, we present some antioxidant preparations of synthetic (N-acetylcysteine, curcumin and its analogs, Probucol, oleane tripertenoid, EGCG synthetic analogs) and nature-identical (vitamin E and C) origin. Then, we analyze their angiogenic properties and their multidirectional molecular effect on angiogenesis. Most preparations reduce neovascularization and diminish the level of proangiogenic molecules, downregulating signaling pathways related to angiogenesis. Moreover, we discuss studies concerning anticancer properties of presented synthetic antioxidants and their application in several angiogenesis-related diseases. We conclude that therapy in angiogenesis-related diseases should be planned with consideration of the angiogenic status of the patient.

Role of Isoprenoid Compounds on Angiogenic Regulation: Opportunities and Challenges.

Isoprenoids represent one of the largest classes of phytochemicals. The structural diversity of these compounds, as well as their remarkable biological activities, makes them suitable candidates for the development of novel therapeutic agents. Several isoprenoids have demonstrated promising potential in the modulation of angiogenesis processes, and therefore provide an appealing alternative and/or addition to the available pharmacotherapies. These compounds could be used per se or combined with standard therapies, which can potentially reduce the undesired secondary effects. Compounds like the sesquiterpenoid artemisinin, and its derivatives, or the diterpenoid triptolide have been successfully tested in a broad range of models (in vitro and in vivo). Moreover, sesquiterpenoids seem to be a promising resource of natural angiogenic modulators, as it can be attested by the significant number of recent publications in this subject. On the other hand, other isoprenoids, such as the triterpenoid ursolic acid, are still under-explored and further studies are needed to understand their role within angiogenic process. Further insights into isoprenoids mode of action in angiogenesis will hopefully pave the way towards their successful clinical use.

Sensitivity of glioma initiating cells to a monoclonal anti-EGFR antibody therapy under hypoxia.

AIMS: Glioma initiating cells (GICs) represent a subpopulation of tumor cells endowed with self-renewal and multilineage differentiation capacity but also with innate resistance to cytotoxic agents, a feature likely to pose major clinical challenges towards the complete eradication of minimal residual disease in glioma patients. MATERIALS AND METHODS: In this work, GICs were obtained from two patient-derived high-grade gliomas xenograft model, expressing differently EGFR. GICs were exposed to anti-EGFR monoclonal antibody cetuximab during 48h in 1% or 21% oxygen tension. Cell viability and self-renewal capacity were then evaluated as well as their angiogenic properties. KEY FINDINGS: GICs were sensitive to cetuximab only in normoxic condition whatever the EGFR status. Nevertheless, under hypoxia cetuximab was able to decrease the self-renewal capacity as well as the expression of CD133 while expression of GFAP increased. Moreover, cetuximab decreased the effect of GICs on endothelial cell migration under hypoxia. SIGNIFICANCE: Consequently, anti-EGFR therapy can be envisaged to target specifically GICs in order to limit the tumor recurrence.

Editorial: Therapeutic Potential of microRNAs in Vascular Disease.

Cardiovascular disease has become the predominant cause of human morbidity and mortality in the industrialized world, devouring extraordinary efforts to determine the molecular and pathophysiological characteristics of the diseased heart and vasculature, while aiming to develop novel diagnostic and therapeutic strategies to treat the associated diseases. The collective work of multiple research groups has uncovered a complex transcriptional and posttranscriptional regulatory circuit, which is believed to be essential for maintaining vascular homeostasis. Recently, a novel class of small noncoding RNAs, called microRNAs, was identified as powerful posttranscriptional regulators, orchestrating the translational output of target messenger RNAs (mRNAs) by promoting mRNA degradation and/or inhibiting translation. With the discovery of microRNAs being powerful modulators in a wide variety of diseases, it is only a logical consequence that the possibilities of viewing microRNAs as promising therapeutic entities are being heavily investigated.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use.

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Endothelial Jagged1 antagonizes Dll4 regulation of endothelial branching and promotes vascular maturation downstream of Dll4/Notch1.

OBJECTIVE: Notch signaling controls cardiovascular development and has been associated with several pathological conditions. Among its ligands, Jagged1 and Dll4 were shown to have opposing effects in developmental angiogenesis, but the underlying mechanism and the role of Jagged1/Notch signaling in adult angiogenesis remain incompletely understood. The current study addresses the importance of endothelial Jagged1-mediated Notch signaling in the context of adult physiological angiogenesis and the interactions of Jagged1 and Dll4 on angiogenic response and vascular maturation processes. APPROACH AND RESULTS: The role of endothelial Jagged1 in wound healing kinetics and angiogenesis was investigated with endothelial-specific Jag1 gain-of-function and loss-of-function mouse mutants (eJag1OE and eJag1cKO). To study the interactions between the 2 Notch ligands, genetic mouse models were combined with pharmacological inhibition of Dll4 or Jagged1, respectively. Jagged1 overexpression in endothelial cells increased vessel density, maturation, and perfusion, thus accelerating wound healing. The opposite effect was seen in eJag1cKO animals. Interestingly, Dll4 blockade in these animals led to an increase in vascular density but induced a greater decrease in perivascular cell coverage. However, Jagged1 inhibition in Dll4 gain-of-function (eDll4OE) mutants, with reduced angiogenesis, further diminished angiogenic growth and hampered perivascular cell coverage. Our findings suggest that as Dll4 blocks endothelial activation through Notch1 signaling, it also induces Jagged1 expression. Jagged1 then blocks Dll4 signaling through Notch1, allowing endothelial activation by vascular endothelial growth factor and endothelial layer growth. Jagged1 also initiates maturation of the newly formed vessels, possibly by binding and activating endothelial Notch4. Importantly, mice administered with a Notch4 agonistic antibody mimicked the mural cell phenotype of eJag1OE mutants without affecting angiogenic growth, which is thought to be Notch1 dependent. CONCLUSIONS: Endothelial Jagged1 is likely to operate downstream of Dll4/Notch1 signaling to activate Notch4 and regulate vascular maturation. Thus, Jagged1 not only counteracts Dll4/Notch in the endothelium but also generates a balance between angiogenic growth and maturation processes in vivo.

Metformin regulates ovarian angiogenesis and follicular development in a female polycystic ovary syndrome rat model.

Polycystic ovary syndrome (PCOS) is a frequent pathology that affects more than 5% of women of reproductive age. Among other heterogeneous symptoms, PCOS is characterized by abnormalities in angiogenesis. Metformin has been introduced in the treatment of PCOS to manage insulin resistance and hyperglycemia. Besides its metabolic effects, metformin has been shown to improve ovulation, pregnancy and live birth rates in PCOS patients. In the present study, we used a dehydroepiandrosterone-induced PCOS rat model to analyze the effect of metformin administration on ovarian angiogenesis. We found that metformin was able to restore the increased levels of vascular endothelial growth factor, angiopoietin (ANGPT)1, and ANGPT1/ANGPT2 ratio and the decreased levels of platelet-derived growth factor B and platelet-derived growth factor D observed in the dehydroepiandrosterone-treated rats. These effects could take place, at least in part, through a decrease in the levels of serum insulin. We also found an improvement in follicular development, with a lower percentage of small follicles and cysts and a higher percentage of antral follicles and corpora lutea after metformin administration. The improvement in ovarian angiogenesis is likely to restore the accumulation of small follicles observed in PCOS rats and to reduce cyst formation, thus improving follicular development and the percentage of corpora lutea. These results open new insights into the study of metformin action not only in glucose metabolism but also in ovarian dysfunction in PCOS women.