All-trans retinoic acid induces in vitro angiogenesis via retinoic acid receptor: possible involvement of paracrine effects of endogenous vascular endothelial growth factor signaling

Insight into perfluorooctanoic acid-induced impairment of mouse embryo implantation via single-cell RNA-seq

Perfluorooctanoic acid (PFOA) is an environmentally persistent chemical that poses significant risks to human health. Studies have shown that PFOA affects female reproduction, but the specific impact on endometrial receptivity and the underlying mechanisms remain poorly understood. In this study, we investigated the effects of low-dose PFOA exposure through drinking water on endometrial receptivity in a murine model. Our results demonstrate that PFOA exposure significantly impaired endometrial receptivity, which led to a marked decrease in embryo implantation rates. Utilizing single-cell RNA sequencing technology, we conducted a comprehensive analysis that revealed specific mechanisms by which PFOA disrupts the function and development of endometrial epithelial cells. Notably, we identified dysregulation of the ANGPTL (angiopoietin-like) signaling pathway, which is critical for communication between endometrial stromal and epithelial cells, ultimately contributing to embryo implantation failure. These findings provide novel insights into the reproductive toxicity of PFOA and highlight potential targets for therapeutic interventions aimed at addressing infertility associated with environmental contaminants.

Generation of iPSC-derived human venous endothelial cells for the modeling of vascular malformations and drug discovery

Venous malformations (VMs) represent prevalent vascular anomalies typically attributed to non-inherited somatic mutations within venous endothelial cells (VECs). The lack of robust disease models for VMs impedes drug discovery. Here, we devise a robust protocol for the generation of human induced VECs (iVECs) through manipulation of cell-cycle dynamics via the retinoic signaling pathway. We introduce an L914F mutation into the TIE2 gene locus of induced pluripotent stem cells (iPSCs) and show that the mutated iVECs form dilated blood vessels after transplantation into mice, thereby recapitulating the phenotypic characteristics observed in VMs. Moreover, utilizing a deep neural network and a high-throughput digital RNA with perturbation of genes sequencing (DRUG-seq) approach, we perform drug screening and demonstrate that bosutinib effectively rescues the disease phenotype in vitro and in vivo. In summary, by leveraging genome editing and stem cell technology, we generate VM models that enable the development of additional therapeutics.

Signaling via retinoic acid receptors mediates decidual angiogenesis in mice and human stromal cell decidualization

At the maternal-fetal interface, tightly regulated levels of retinoic acid (RA), the physiologically active metabolite of vitamin A, are required for embryo implantation and pregnancy success. Herein, we utilize mouse models, primary human cells, and pharmacological tools to demonstrate how depletion of RA signaling via RA receptor (RAR) disrupts implantation and progression of early pregnancy. To inhibit RAR signaling during early pregnancy, BMS493, an inverse pan-RAR agonist that prevents RA-induced differentiation, was administered to pregnant mice during the peri-implantation period. Attenuation of RA/RAR signaling prior to embryo implantation results in implantation failure, whereas attenuation of RA/RAR signaling after embryo implantation disrupts the post-implantation decidual vasculature and results in pregnancy failure by mid-gestation. To inhibit RAR signaling during human endometrial stromal cell (HESC) decidualization, primary HESCs and decidualized primary HESCs were transfected with silencing RNA specific for human RARA. Inhibition of RA/RARA signaling prevents initiation of HESC decidualization, but not maintenance of the decidualized HESC phenotype. These data show that RA/RAR signaling is required for maintenance of the decidual vasculature that supports early pregnancy in mice, and distinct RAR signaling is required for initiation, but not maintenance of primary HESC decidualization in vitro.

Small molecule agents against alopecia: Potential targets and related pathways

Alopecia has emerged as a global concern, extending beyond the middle-aged and elderly population and increasingly affecting younger individuals. Despite its growing prevalence, the treatment options and effective drugs for alopecia remain limited due to the incomplete understanding of its underlying mechanisms. Therefore, it is urgent to explore the pathogenesis of alopecia and discover novel and safer therapeutic agents. This review provided an overview of the prevailing clinical disorders of alopecia, and the key pathways and targets involved in hair growth process. Additionally, it discusses FDA-approved drugs and clinical candidates for the treatment of alopecia, and explores small molecule compounds with anti-alopecia potential in the drug discovery phase. These endeavors are expected to provide researchers with valuable scientific insights and practical information for anti-alopecia drug discovery.

Dynamics of Endothelial Cell Diversity and Plasticity in Health and Disease

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity.

Advances in Engineered Nanoparticles for the Treatment of Ischemic Stroke by Enhancing Angiogenesis

Angiogenesis, or the formation of new blood vessels, is a natural defensive mechanism that aids in the restoration of oxygen and nutrition delivery to injured brain tissue after an ischemic stroke. Angiogenesis, by increasing vessel development, may maintain brain perfusion, enabling neuronal survival, brain plasticity, and neurologic recovery. Induction of angiogenesis and the formation of new vessels aid in neurorepair processes such as neurogenesis and synaptogenesis. Advanced nano drug delivery systems hold promise for treatment stroke by facilitating efficient transportation across the the blood-brain barrier and maintaining optimal drug concentrations. Nanoparticle has recently been shown to greatly boost angiogenesis and decrease vascular permeability, as well as improve neuroplasticity and neurological recovery after ischemic stroke. We describe current breakthroughs in the development of nanoparticle-based treatments for better angiogenesis therapy for ischemic stroke employing polymeric nanoparticles, liposomes, inorganic nanoparticles, and biomimetic nanoparticles in this study. We outline new nanoparticles in detail, review the hurdles and strategies for conveying nanoparticle to lesions, and demonstrate the most recent advances in nanoparticle in angiogenesis for stroke treatment.

Cellular and micro-environmental responses influencing the antitumor activity of all-trans retinoic acid in breast cancer

All-trans retinoic acid (ATRA) is the most relevant and functionally active metabolite of Vitamin-A. From a therapeutic standpoint, ATRA is the first example of pharmacological agent exerting its anti-tumor activity via a cell differentiating action. In the clinics, ATRA is used in the treatment of Acute Promyelocytic Leukemia, a rare form of myeloid leukemia with unprecedented therapeutic results. The extraordinary effectiveness of ATRA in the treatment of Acute Promyelocytic Leukemia patients has raised interest in evaluating the potential of this natural retinoid in the treatment of other types of neoplasias, with particular reference to solid tumors.The present article provides an overview of the available pre-clinical and clinical studies focussing on ATRA as a therapeutic agent in the context of breast cancer from a holistic point of view. In detail, we focus on the direct effects of ATRA in breast cancer cells as well as the underlying molecular mechanisms of action. In addition, we summarize the available information on the action exerted by ATRA on the breast cancer micro-environment, an emerging determinant of the progression and invasive behaviour of solid tumors. In particular we discuss the recent evidences of ATRA activity on the immune system. Finally, we analyse and discuss the results obtained with the few ATRA-based clinical trials conducted in the context of breast cancer.

Angiogenesis, coagulation, and fibrinolytic markers in acute promyelocytic leukemia (NB4): An evaluation of melatonin effects

Melatonin is a powerful biological agent that has been shown to inhibit angiogenesis and also exerts anti-inflammatory effects. It is well known that new blood vessel formation (angiogenesis) has become an urgent issue in leukemia as well as solid tumors. Acute promyelocytic leukemia (APL) is a form of liquid cancer that manifests increased angiogenesis in the bone marrow of patients. Despite high-rate curable treatment with all-trans-retinoic acid (ATRA) and recently arsenic-trioxide (ATO), early death because of hemorrhage, coagulopathy, and Disseminated intravascular coagulation (DIC) remains still a concerning issue in these patients. It is, therefore, urgent to seek treatment strategies with antiangiogenic capabilities that also diminish coagulopathy and hyperfibrinolysis in APL patients. In this study, a coculture system with human umbilical vein endothelial cells (HUVECs) and NB4 APL cells was used to investigate the direct effect of melatonin on angiogenesis and its possible action on tissue factor (TF) and tissue-type plasminogen activator-1 (TPA-1) expression. Our experiments revealed that HUVEC-induced angiogenesis by cocultured NB4 cells was suppressed when melatonin alone or in combination with ATRA was added to the incubation medium. Melatonin at concentrations of 1 mM inhibited tube formation of HUVECs and also decreased interleukin-6 secretion and VEGF mRNA expression in HUVEC and NB4 cells. Taken together, the results of this study demonstrate that melatonin inhibits accelerated angiogenesis of HUVECs and ameliorates the coagulation and fibrinolysis indices stimulated by coculturing with NB4 cells.

Increasing adipocyte number and reducing adipocyte size: the role of retinoids in adipose tissue development and metabolism

The rising prevalence of obesity is a grave public health threat. In response to excessive energy intake, adipocyte hypertrophy impairs cellular function and leads to metabolic dysfunctions while de novo adipogenesis leads to healthy adipose tissue expansion. Through burning fatty acids and glucose, the thermogenic activity of brown/beige adipocytes can effectively reduce the size of adipocytes. Recent studies show that retinoids, especially retinoic acid (RA), promote adipose vascular development which in turn increases the number of adipose progenitors surrounding the vascular vessels. RA also promotes preadipocyte commitment. In addition, RA promotes white adipocyte browning and stimulates the thermogenic activity of brown/beige adipocytes. Thus, vitamin A is a promising anti-obesity micronutrient.

Hemocompatibility of all-trans retinoic acid-loaded citrate polymer coatings for vascular stents

Purpose

Current strategies implementing drug-eluting polymer stent coatings fail to fully address the lasting effects of endothelial suppression which ultimately result in delayed reendothelialization and thrombogenic complications. The present study investigates the in vitro hemocompatibility of all-trans retinoic acid loaded poly (1,8-octanediol-co-citrate) coatings (AtRA-POC coatings) for advanced intravascular stent technology. The ability of these materials in supporting endothelial restoration via migration and proliferation while inhibiting smooth muscle cell growth is also explored.

Methods

Using in vitro models, the hemocompatibility of AtRA-loaded POC-coated cobalt chromium (CoCr) vascular stents was evaluated in terms of platelet and inflammatory activity. Platelet activity was quantified by platelet adhesion and platelet activation, further supported by SEM visualization. Inflammatory activity was quantified by the production of proinflammatory cytokines by THP1 monocytes. Lastly, in vitro wound healing and an 5-Ethynyl-2'deoxyuridine (EdU) and pico green DNA assays were used in quantitating endothelial and smooth muscle cell migration and proliferation.

Results

Experimental examinations of platelet adhesion and activation demonstrate significant reductions in the platelet response to POC coated AtRA loaded stents when compared to bare CoCr stents. Such findings reveal AtRA-POC coatings to have significantly improved hemocompatibility compared to that of bare metal stents and at least as good as POC alone. Similarly, in reference to LPS-stimulated controls, Human monocyte-like THP1 cells in culture with AtRA-POC-CoCr stents for 24 hours showed reduced detection of proinflammatory cytokines, comparable to that of bare CoCr and untreated controls. This result supports AtRA-POC coatings as possessing limited immunological potential. Observations from in vitro endothelial and smooth muscle cell investigations demonstrate the ability of the drug AtRA to allow cell processes involved in restoration of the endothelium while inhibiting smooth muscle cell processes.

Conclusion

This study demonstrates AtRA loaded POC coatings are hemocompatible, noninflammatory, and provide a promising strategy in enhancing vascular stent techniques and clinical integration. Possessing hemocompatibility and immunological compatibility that is at least as good as bare metal stents as clinical standards support the use of AtRA-POC coatings for vascular applications. Additionally, selectively reducing smooth muscle cell proliferation while supporting endothelial cell proliferation and migration further demonstrates the potential of these materials in significantly improving the state of vascular stent technology in the area of stent thrombosis and neointimal hyperplasia.

Direct Reprograming of Mouse Fibroblasts into Dermal Papilla Cells via Small Molecules

The reprogramming of somatic fibroblasts into alternative cell linages could provide a promising source of cells for regenerative medicine and cell therapy. However, the direct conversion of fibroblasts into other functional cell types is still challenging. In this study, we show that dermal-papilla-cell-like cells (DPC-LCs) can be generated by treating fibroblasts, including L929 mouse fibroblast cell lines and somatic mouse fibroblasts, with small molecules. Based on alkaline phosphatase activity and other molecular markers, different compounds or their combinations are needed for converting the two different fibroblasts into DPC-LCs. Notably, we found that TTNPB alone can efficiently convert primary adult mouse fibroblasts into DPC-LCs. DPC-LCs generated from mouse fibroblasts showed a stronger hair-inducing capacity. Transcriptome analysis reveals that expression of genes associated with a hair-inducing capacity are increased in DPC-LCs. This pharmacological approach to generating functional dermal papilla cells may have many important implications for hair follicle regeneration and hair loss therapy.

Expression and Distribution Pattern of Retinoic Acid Receptors in the Nasal Mucosa

Background and Objectives

Retinoids are naturally occurring vitamin A derivatives that regulate cellular processes and metabolism. In particular, retinoids play a key role in cellular proliferation by binding to retinoic acid receptors (RAR)-alpha, beta, and gamma. Considering the functional role of nasal mucosa where active cell regeneration occurs, RAR may play a role in tissue remodeling of the human nasal mucosa.

Methods

In this study, we investigated the expression and distribution pattern of RAR using reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry (IHC) and Western blot in normal ethmoid mucosa (NE), chronic rhinosinusitis (IE) and polyp (P).

Results

IE and P samples showed higher expression levels of RAR in RT-PCR and Western blot than NE samples. RAR reactivity was also observed in the NE group, which indicates that cell regeneration also occurs in normal condition. Through IHC, we found the localization of RAR. RAR-α was distributed in the epithelial cells, submucosal glands, and endothelial cells. RAR-β was located in the basal epithelium, while RAR-γ was present in goblet cells and submucosal glands. The staining intensity of RAR-α, β and γ was higher than that in the NE group. Especially in the P group, RARs were abundantly distributed in the stalks of polyps.

Conclusion

The stalk region contains a lot of collagen and fibroblasts to support polyp formation, and the greater amount of RAR in the stalk suggested that RARs may be associated with angiogenesis and cell proliferation. Accordingly, elevated RAR levels in chronic rhinosinusitis could indicate that RARs play a critical role in cell regeneration, angiogenesis and immunomodulation under inflammatory conditions in the human nasal mucosa.

Aberrant regulation of retinoic acid signaling genes in cerebral arterio venous malformation nidus and neighboring astrocytes

BACKGROUND

Cerebral arterio venous malformations (AVM) are a major causal factor for intracranial hemorrhage, which result in permanent disability or death. The molecular mechanisms of AVM are complex, and their pathogenesis remains an enigma. Current research on cerebral AVM is focused on characterizing the molecular features of AVM nidus to elucidate the aberrant signaling pathways. The initial stimuli that lead to the development of AVM nidus structures between a dilated artery and a vein are however not known.

METHODS

In order to understand the molecular basis of development of cerebral AVM, we used in-depth RNA sequencing with the total RNA isolated from cerebral AVM nidus. Immunoblot and qRT-PCR assays were used to study the differential gene expression in AVM nidus, and immunofluorescence staining was used to study the expression pattern of aberrant proteins in AVM nidus and control tissues. Immunohistochemistry was used to study the expression pattern of aberrant proteins in AVM nidus and control tissues.

RESULTS

The transcriptome study has identified 38 differentially expressed genes in cerebral AVM nidus, of which 35 genes were upregulated and 3 genes were downregulated. A final modular analysis identified an upregulation of ALDH1A2, a key rate-limiting enzyme of retinoic acid signaling pathway. Further analysis revealed that CYR61, a regulator of angiogenesis, and the target gene for retinoic acid signaling is upregulated in AVM nidus. We observed that astrocytes associated with AVM nidus are abnormal with increased expression of GFAP and Vimentin. Triple immunofluorescence staining of the AVM nidus revealed that CYR61 was also overexpressed in the abnormal astrocytes associated with AVM tissue.

CONCLUSION

Using high-throughput RNA sequencing analysis and immunostaining, we report deregulated expression of retinoic acid signaling genes in AVM nidus and its associated astrocytes and speculate that this might trigger the abnormal angiogenesis and the development of cerebral AVM in humans.

Explainable drug sensitivity prediction through cancer pathway enrichment

Computational approaches to predict drug sensitivity can promote precision anticancer therapeutics. Generalizable and explainable models are of critical importance for translation to guide personalized treatment and are often overlooked in favor of prediction performance. Here, we propose PathDSP: a pathway-based model for drug sensitivity prediction that integrates chemical structure information with enrichment of cancer signaling pathways across drug-associated genes, gene expression, mutation and copy number variation data to predict drug response on the Genomics of Drug Sensitivity in Cancer dataset. Using a deep neural network, we outperform state-of-the-art deep learning models, while demonstrating good generalizability a separate dataset of the Cancer Cell Line Encyclopedia as well as provide explainable results, demonstrated through case studies that are in line with current knowledge. Additionally, our pathway-based model achieved a good performance when predicting unseen drugs and cells, with potential utility for drug development and for guiding individualized medicine.

An in vitro model for investigation of vitamin A effects on wound healing

Wound healing consists of a series of highly orderly overlapping processes characterized by hemostasis, inflammation, proliferation, and remodeling. Prolongation or interruption in each phase can lead to delayed wound healing or a non-healing chronic wound. Vitamin A is a crucial nutrient that is most beneficial for the health of the skin. The present study was undertaken to determine the effect of vitamin A on regeneration, angiogenesis, and inflammation characteristics in an in vitro model system during wound healing. For this purpose, mouse skin normal fibroblast (L929), human umbilical vein endothelial cell (HUVEC), and monocyte/macrophage-like cell line (RAW 264.7) were considered to evaluate proliferation, angiogenesis, and anti-inflammatory responses, respectively. Vitamin A (0.1-5 μM) increased cellular proliferation of L929 and HUVEC (p < 0.05). Similarly, it stimulated angiogenesis by promoting endothelial cell migration up to approximately 4 fold and interestingly tube formation up to 8.5 fold (p < 0.01). Furthermore, vitamin A treatment was shown to decrease the level of nitric oxide production in a dose-dependent effect (p < 0.05), exhibiting the anti-inflammatory property of vitamin A in accelerating wound healing. These results may reveal the therapeutic potential of vitamin A in diabetic wound healing by stimulating regeneration, angiogenesis, and anti-inflammation responses.

Vitamin A as a Transcriptional Regulator of Cardiovascular Disease

Vitamin A is a micronutrient and signaling molecule that regulates transcription, cellular differentiation, and organ homeostasis. Additionally, metabolites of Vitamin A are utilized as differentiation agents in the treatment of hematological cancers and skin disorders, necessitating further study into the effects of both nutrient deficiency and the exogenous delivery of Vitamin A and its metabolites on cardiovascular phenotypes. Though vitamin A/retinoids are well-known regulators of cardiac formation, recent evidence has emerged that supports their role as regulators of cardiac regeneration, postnatal cardiac function, and cardiovascular disease progression. We here review findings from genetic and pharmacological studies describing the regulation of both myocyte- and vascular-driven cardiac phenotypes by vitamin A signaling. We identify the relationship between retinoids and maladaptive processes during the pathological hypertrophy of the heart, with a focus on the activation of neurohormonal signaling and fetal transcription factors (Gata4, Tbx5). Finally, we assess how this information might be leveraged to develop novel therapeutic avenues.

Isotretinoin does not alter VEGF-A and VEGF-C levels: do retinoids behave differently in dose-dependent and/or in vivo/in vitro conditions?

BACKGROUND

It is seen that various forms of retinoids have different results on VEGF-A and VEGF-C levels when tested at different dosages, in different diseases and under different conditions such as in vivo or in vitro.

OBJECTIVE

To evaluate the effects of isotretinoin on VEGF-A and VEGF-C levels in humans.

METHODS

Blood samples at the third month of the patient group and blood samples of the control group were compared in terms of VEGF-A and VEGF-C concentrations.

RESULTS

No statistically significant difference was observed between the patient group and the control group in terms of VEGF-A and VEGF-C levels.

LIMITATIONS

Most of the patients discontinued treatment and could not reach the required number, the study was converted to case-control.

CONCLUSIONS

We think that 0.5 mg/kg/day isotretinoin has no effect on blood concentrations of VEGF-A and VEGF-C in humans. Therefore, there is a need for studies using isotretinoin in different doses and durations in humans in order to better evaluate its effects.

All-Trans Retinoic Acid Grafted Poly Beta-Amino Ester Nanoparticles: A Novel Anti-angiogenic Drug Delivery System

Purpose: Developing chemotherapy with nanoplatforms offers a promising strategy for effective cancer treatment. In the present study, we propose a novel all-trans retinoic acid (ATRA) grafted poly beta-amino ester (PBAE) copolymer for preparing nanoparticles (NPs). Methods: ATRA grafted PBAE (ATRA-g-PBAE) copolymer was synthesized by grafting ATRA to PBAE; it was characterized by proton nuclear magnetic resonance, Fourier transform infrared, and thermogravimetric analysis. ATRA-g-PBAE NPs were prepared by the solvent displacement method. Design-Expert software was employed to optimize size of NPs. The morphology was evaluated by transmission electron microscope, and ultraviolet-visible spectroscopy was applied for drug release. Cytotoxicity was evaluated toward HUVEC cell line, and the 3D collagencytodex model was used to evaluate anti-angiogenic property of PBAE, ATRA, and NPs. Results: The optimum size of the NPs was 139.4 ± 1.41 nm. After 21 days, 66.09% ± 1.39 and 42.14% ± 1.07 of ATRA were released from NPs at pH 5.8 and 7.4, respectively. Cell culture studies demonstrated antiangiogenic effects of ATRA-g-PBAE NPs. Anti-angiogenesis IC50 was 0.007 mg/mL for NPs (equal to 0.002 mg/mL of ATRA) and 0.005 mg/mL for free ATRA. Conclusion: This study proposes the ATRA-g-PBAE NPs with inherent anti-angiogenic effects as promising carrier for anticancer drugs with purpose of dual drug delivery.

Effect of isotretinoin (13-cis-retinoic acid) on levels of soluble VEGF receptors (sVEGFR1, sVEGFR2, sVEGFR3) in patients with acne vulgaris

Background/aim: The effect of isotretinoin on soluble VEGFRs has not been previously investigated. This study evaluate the effects of isotretinoin (13-cis-retinoic acid) on soluble VEGFR1 (sVEGFR1), soluble VEGFR2 (sVEGFR2) and soluble VEGFR3 (sVEGFR3).Methods: The study included 38 patients (28 females, 10 males) receiving systemic isotretinoin treatment and 38 healthy individuals (28 females, 10 males) with similar age and gender characteristics. The blood samples of the patient group at third months and blood samples of the control group were compared in terms of sVEGFR1, sVEGFR2 and sVEGFR3 concentrations.Results: It was significant that sVEGFR1 was low and sVEGFR3 was high in patients receiving isotretinoin (p: .038, p: .021, respectively). There was no significant change in sVEGFR2 levels between the groups (p: .519).Conclusions: We think that the effect of isotretinoin on sVEGFR1, sVEGFR2 and sVEGFR3 may be secondary to its effects on the VEGF family. However, after clarifying the effect of isotretinoin on the VEGF family, we think that it can be used in some tumors and vascular diseases.

Interpreting Coronary Artery Disease Risk Through Gene-Environment Interactions in Gene Regulation

GWAS and eQTL studies identified thousands of genetic variants associated with complex traits and gene expression. Despite the important role of environmental exposures in complex traits, only a limited number of environmental factors were measured in these studies. Measuring molecular phenotypes in tightly controlled cellular environments provides a more tractable setting to study gene-environment interactions in the absence of other confounding variables. We performed RNA-seq and ATAC-seq in endothelial cells exposed to retinoic acid, dexamethasone, caffeine, and selenium to model genetic and environmental effects on gene regulation in the vascular endothelium-a common site of pathology in cardiovascular disease. We found that genes near regions of differentially accessible chromatin were more likely to be differentially expressed [OR = (3.41, 6.52), [Formula: see text]]. Furthermore, we confirmed that environment-specific changes in transcription factor binding are a key mechanism for cellular response to environmental stimuli. Single nucleotide polymorphisms (SNPs) in these transcription response factor footprints for dexamethasone, caffeine, and retinoic acid were enriched in GTEx eQTLs from artery tissues, indicating that these environmental conditions are latently present in GTEx samples. Additionally, SNPs in footprints for response factors in caffeine are enriched in colocalized eQTLs for coronary artery disease (CAD), suggesting a role for caffeine in CAD risk. By combining GWAS, eQTLs, and response genes, we annotated environmental components that can increase or decrease disease risk through changes in gene expression in 43 genes. Interestingly, each treatment may amplify or buffer genetic risk for CAD, depending on the particular SNP or gene considered.

In Vitro Models to Study the Regulatory Roles of Retinoids in Angiogenesis

Retinoids are reported to regulate vascular growth and remodeling during embryonic development and wound healing. A better understanding of angiogenic mechanisms of retinoids has clinical implication in pathological conditions such as chronic nonhealing wounds. Here, we describe in vitro angiogenesis assays that can be a useful tool to study the role of retinoids and retinoic acid signaling in the regulation of different features of angiogenesis such as tubulogenesis and branching.

All-Trans-Retinoic Acid Suppresses Neointimal Hyperplasia and Inhibits Vascular Smooth Muscle Cell Proliferation and Migration via Activation of AMPK Signaling Pathway

The proliferation and migration of vascular smooth muscle cells (VSMC) is extensively involved in pathogenesis of neointimal hyperplasia. All-trans-retinoic acid (ATRA) is a natural metabolite of vitamin A. Here, we investigated the involvement of AMP-activated protein kinase (AMPK) in the anti-neointimal hyperplasia effects of ATRA. We found that treatment with ATRA significantly reduced neointimal hyperplasia in the left common carotid artery ligation mouse model. ATRA reduced the proliferation and migration of VSMC, A7r5 and HASMC cell lines. Our results also demonstrated that ATRA altered the expression of proliferation-related proteins, including CyclinD1, CyclinD3, CyclinA2, CDK2, CDK4, and CDK6 in VSMC. ATRA dose-dependently enhanced the phosphorylation level of AMPKα (Thr172) in the left common carotid artery of experimental mice. Also, the phosphorylation level of AMPKα in A7r5 and HASMC was significantly increased. In addition, ATRA dose-dependently reduced the phosphorylation levels of mTOR and mTOR target proteins p70 S6 kinase (p70S6K) and 4E-binding protein 1 (4EBP1) in A7r5 and HASMC. Notably, the inhibition of AMPKα by AMPK inhibitor (compound C) negated the protective effect of ATRA on VSMC proliferation in A7r5. Also, knockdown of AMPKα by siRNA partly abolished the anti-proliferative and anti-migratory effects of ATRA in HASMC. Molecular docking analysis showed that ATRA could dock to the agonist binding site of AMPK, and the binding energy between AMPK and ATRA was -7.91 kcal/mol. Molecular dynamics simulations showed that the binding of AMPK-ATRA was stable. These data demonstrated that ATRA might inhibit neointimal hyperplasia and suppress VSMC proliferation and migration by direct activation of AMPK and inhibition of mTOR signaling.

FLORID NEOVASCULARIZATION OF THE RETINA IN A DIABETIC PATIENT UNDERGOING INDUCTION AND CONSOLIDATION THERAPY FOR ACUTE PROMYELOCYTIC LEUKEMIA

PURPOSE

To report on a 39-year-old gentleman with a background of Type 2 diabetes mellitus who was diagnosed with acute promyelocytic leukemia (APL), which was treated by all-trans retinoic acid (ATRA), and subsequently developed bilateral neovascularization of the disk (NVD).

METHODS

Ophthalmic examination and investigation including fundus photography and fluorescein angiography.

RESULTS

Three months after commencement of ATRA therapy, the patient was found to have florid bilateral NVD with adjacent preretinal and intraretinal hemorrhages. Fundus fluorescein angiography was undertaken and NVD was confirmed in both eyes, which was significantly greater than expected for the extent of disease secondary to diabetic retinopathy. As a result of the fluorescein angiography findings, we believe ATRA-mediated upregulation of vascular endothelial growth factor may be the etiology of the NVD. Literature review shows some in vitro studies, which describe ATRA-induced upregulation of vascular endothelial growth factor in ocular tissues. The patient was managed successfully by cessation of ATRA and a single intravitreal injection of bevacizumab in each eye.

CONCLUSION

Acute promyelocytic leukemia treated with ATRA may result in upregulation of vascular endothelial growth factor in retinal tissues. Subsequent development of NVD may occur; however, this resolves well by cessation of ATRA and intravitreal injection of bevacizumab. We recommend that all patients undergoing treatment with ATRA for acute promyelocytic leukemia be monitored by an ophthalmologist.

Retinoic acid signaling in vascular development

Formation of the vasculature is an essential developmental process, delivering oxygen and nutrients to support cellular processes needed for tissue growth and maturation. Retinoic acid (RA) and its downstream signaling pathway is vital for normal pre- and post-natal development, playing key roles in the specification and formation of many organs and tissues. Here, we review the role of RA in blood and lymph vascular development, beginning with embryonic yolk sac vasculogenesis and remodeling and discussing RA's organ-specific roles in angiogenesis and vessel maturation. In particular, we highlight the multi-faceted role of RA signaling in CNS vascular development and acquisition of blood-brain barrier properties.

Temporal Dynamics of Gene Expression During Endothelial Cell Differentiation From Human iPS Cells: A Comparison Study of Signalling Factors and Small Molecules

Endothelial cell (EC) therapy may promote vascular growth or reendothelization in a variety of disease conditions. However, the production of a cell therapy preparation containing differentiated, dividing cells presenting typical EC phenotype, functional properties and chemokine profile is challenging. We focused on comparative analysis of seven small molecule-mediated differentiation protocols of ECs from human induced pluripotent stem cells. Differentiated cells showed a typical surface antigen pattern of ECs as characterized with flow cytometry analysis, functional properties, such as tube formation and ability to uptake acetylated LDL. Gene expression analysis by RNA sequencing revealed an efficient silencing of pluripotency genes and upregulation of genes related to cellular adhesion during differentiation. In addition, distinct patterns of transcription factor expression were identified during cellular reprogramming providing targets for more effective differentiation protocols in the future. Altogether, our results suggest that the most optimal EC differentiation protocol includes early inhibition of Rho-associated coiled-coil kinase and activation of cyclic AMP signaling, and inhibition of transforming growth factor beta signaling after mesodermal stage. These findings provide the first systematic characterization of the most potent signalling factors and small molecules used to generate ECs from human induced pluripotent stem cells and, consequently, this work improves the existing EC differentiation protocols and opens up new avenues for controlling cell fate for regenerative EC therapy.

Intravenous administration of retinoic acid-loaded polymeric nanoparticles prevents ischemic injury in the immature brain

Perinatal stroke is often difficult to diagnose and an established treatment has not yet been validated, except for symptomatic measures. Herein, we propose to test the neuroprotective potential of the intravenous injection of retinoic acid-loaded nanoparticles (RA-NP) upon ischemic injury to the immature brain. The role of RA-NP on endothelial cells and organotypic slice cultures exposed to oxygen and glucose deprivation was assessed by evaluating markers pertaining to survival, proliferation, oxidative stress (NO, ROS), neuronal damage (enolase), vascular oxidation (p47phox) and microglia activation (CD68). Data showed that RA-NP (3 μg/ml) increased endothelial proliferation and survival, and normalized NO and ROS levels. The intravenous administration of RA-NP (10 μg/g) prevented ischemic injury in the hippocampus of 2-day-old mice by inhibiting cell death and normalizing markers of neurovascular function and inflammation. In sum, systemic administration of RA-NP protected neurovascular integrity and the inflammatory milieu from ischemia in the immature brain, highlighting its therapeutic value for perinatal stroke.

Physiological and pathological implications of retinoid action in the endometrium

Retinol (vitamin A) and its derivatives, collectively known as retinoids, are required for maintaining vision, immunity, barrier function, reproduction, embryogenesis and cell proliferation and differentiation. Despite the fact that most events in the endometrium are predominantly regulated by steroid hormones (estrogens and progesterone), accumulating evidence shows that retinoid signaling is also involved in the development and maintenance of the endometrium, stromal decidualization and blastocyst implantation. Moreover, aberrant retinoid metabolism seems to be a critical factor in the development of endometriosis, a common gynecological disease, which affects up to 10% of reproductive age women and is characterized by the ectopic localization of endometrial-like tissue in the pelvic cavity. This review summarizes recent advances in research on the mechanisms and molecular actions of retinoids in normal endometrial development and physiological function. The potential roles of abnormal retinoid signaling in endometriosis are also discussed. The objectives are to identify limitations in current knowledge regarding the molecular actions of retinoids in endometrial biology and to stimulate new investigations toward the development potential therapeutics to ameliorate or prevent endometriosis symptoms.

β-Cryptoxanthin Inhibits Angiogenesis in Human Umbilical Vein Endothelial Cells Through Retinoic Acid Receptor

SCOPE

β-Cryptoxanthin is an abundant carotenoid in fruits and vegetables that can be quantified in human blood serum. Yet, contrary to other carotenoids, its effects on endothelial cells and angiogenesis remain unknown.

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVEC) are treated with 0.01, 0.1, or 1 μm of β-cryptoxanthin. Antioxidant activity is determined by its free radical scavenging and oxygen-radical absorbance capacity. The effect on migration and formation of tubular structures is studied. Additionally, effect on angiogenesis is also analyzed using an in vivo model. β-Cryptoxanthin exhibits scavenging ability, having an antioxidant effect on HUVEC. Interestingly, β-cryptoxanthin reduces their migration and angiogenesis, even in the presence of vascular endothelial growth factor (VEGF). Additionally, such carotenoid inhibits in vivo angiogenesis induced by VEGF. In addition, treatment of HUVEC with LE540 (retinoic acid receptor [RAR] panantagonist) inhibits β-cryptoxanthin antiangiogenic effect on HUVEC.

CONCLUSION

β-Cryptoxanthin inhibits angiogenesis through RAR. Thus, this carotenoid and food containing it may be useful for the prevention and treatment of angiogenic pathologies. That includes tumoral growth and wet macular degeneration associated with aging. To the best of our knowledge, this is the first report of the antioxidant effect and antiangiogenic activity of this carotenoid on HUVEC, both in vitro and in vivo.

Retinoic acid induces white adipose tissue browning by increasing adipose vascularity and inducing beige adipogenesis of PDGFRα+ adipose progenitors

Formation of beige adipocytes within white adipose tissue enhances energy expenditure, which is a promising strategy to reduce obesity and prevent metabolic symptoms. Vitamin A and its bioactive metabolite, retinoic acid (RA), have regulatory roles in lipid metabolism. Here we report that RA induces white adipose tissue browning via activating vascular endothelial growth factor (VEGF) signaling. RA triggered angiogenesis and elicited de novo generation of platelet-derived growth factor receptor α positive (PDGFRα⁺) adipose precursor cells via VEGFA/VEGFR2 signaling. In addition, RA promoted beige/brown adipocyte formation from capillary networks in vitro. Using PDGFRα tracking mice, we found that the vascular system acted as an adipogenic repository by containing PDGFRα⁺ progenitors which differentiated into beige adipocytes under RA or VEGF164 treatments. Conditional knockout of VEGF receptors blocked RA-stimulated white adipose tissue browning. Moreover, the VEGFA and RA activated p38MAPK to enhance the binding of RA receptor to RA response elements of the Prdm16 promoter and upregulated Prdm16 transcription. In conclusion, RA induces white adipose tissue browning by increasing adipose vascularity and promoting beige adipogenesis of PDGFRα⁺ adipose progenitors.

Challenging the great vascular wall: Can we envision a simple yet comprehensive therapy for stroke?

Stroke is a leading cause of death in adult life, closely behind ischemic heart disease, and causes a significant and abiding socioeconomic burden. However, current therapies are not able to ensure full neurologic and/or sequelae-free recovery to all stroke survivors. We believe treatment efficacy and patient rehabilitation could be enhanced significantly by targeting blood-brain barrier (BBB) deregulation and inflammation-induced barrier loss that occurs after stroke. In this pathological context, bone marrow-derived endothelial progenitor cells (EPC) enter the bloodstream towards the lesion site, but their insufficient numbers and impaired angiogenic ability compromise neurovascular regeneration. In this context, cell-based therapies have become increasingly appealing since treating patients with large numbers of mesenchymal or hematopoietic stem/progenitor cells alone may boost repair. However, this approach could be met with several challenges in terms of logistics and cost; hence, the development of a drug delivery system suitable for intravenous administration and functionalized for selective uptake by circulating EPC could enhance their restorative potential without perceived complications. The ability to encapsulate proangiogenic and anti-inflammatory agents, such as retinoic acid, and to safely and easily deliver them systemically may open new therapeutic perspectives for the treatment of cerebrovascular disorders. Copyright © 2017 John Wiley & Sons, Ltd.

All-trans retinoic acid preconditioning enhances proliferation, angiogenesis and migration of mesenchymal stem cell in vitro and enhances wound repair in vivo

OBJECTIVES

Stem cell therapy is considered to be a suitable alternative in treatment of a number of diseases. However, there are challenges in their clinical application in cell therapy, such as to reduce survival and loss of transplanted stem cells. It seems that chemical and pharmacological preconditioning enhances their therapeutic efficacy. In this study, we investigated effects of all-trans retinoic acid (ATRA) on survival, angiogenesis and migration of mesenchymal stem cells (MSCs) in vitro and in a wound-healing model.

MATERIALS AND METHODS

MSCs were treated with a variety of concentrations of ATRA, and mRNA expression of cyclo-oxygenase-2 (COX-2), hypoxia-inducible factor-1 (HIF-1), C-X-C chemokine receptor type 4 (CXCR4), C-C chemokine receptor type 2 (CCR2), vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2) and Ang-4 were examined by qRT-PCR. Prostaglandin E2 (PGE2) levels were measured using an ELISA kit and MSC angiogenic potential was evaluated using three-dimensional tube formation assay. Finally, benefit of ATRA-treated MSCs in wound healing was determined with a rat excisional wound model.

RESULTS

In ATRA-treated MSCs, expressions of COX-2, HIF-1, CXCR4, CCR2, VEGF, Ang-2 and Ang-4 increased compared to control groups. Overexpression of the related genes was reversed by celecoxib, a selective COX-2 inhibitor. Tube formation and in vivo wound healing of ATRA-treated MSCs were also significantly enhanced compared to untreated MSCs.

CONCLUSION

Pre-conditioning of MSCs with ATRA increased efficacy of cell therapy by activation of survival signalling pathways, trophic factors and release of pro-angiogenic molecules.

All-trans retinoic acid and rapamycin normalize Hutchinson Gilford progeria fibroblast phenotype

Hutchinson Gilford progeria syndrome is a fatal disorder characterized by accelerated aging, bone resorption and atherosclerosis, caused by a LMNA mutation which produces progerin, a mutant lamin A precursor. Progeria cells display progerin and prelamin A nuclear accumulation, altered histone methylation pattern, heterochromatin loss, increased DNA damage and cell cycle alterations. Since the LMNA promoter contains a retinoic acid responsive element, we investigated if all-trans retinoic acid administration could lower progerin levels in cultured fibroblasts. We also evaluated the effect of associating rapamycin, which induces autophagic degradation of progerin and prelamin A. We demonstrate that all-trans retinoic acid acts synergistically with low-dosage rapamycin reducing progerin and prelamin A, via transcriptional downregulation associated with protein degradation, and increasing the lamin A to progerin ratio. These effects rescue cell dynamics and cellular proliferation through recovery of DNA damage response factor PARP1 and chromatin-associated nuclear envelope proteins LAP2α and BAF. The combined all-trans retinoic acid-rapamycin treatment is dramatically efficient, highly reproducible, represents a promising new approach in Hutchinson-Gilford Progeria therapy and deserves investigation in ageing-associated disorders.

All-trans retinoic acid ameliorates glycemic control in diabetic mice via modulating pancreatic islet production of vascular endothelial growth factor-A

Patients with type 1 diabetes mellitus are associated with impairment in vitamin A metabolism. This study evaluated whether treatment with retinoic acid, the biologically active metabolite of vitamin A, can ameliorate diabetes. All-trans retinoic acid (atRA) was used to treat streptozotocin (STZ)-induced diabetic mice which revealed atRA administration ameliorated blood glucose levels of diabetic mice. This hyperglycemic amelioration was accompanied by an increase in the amount of β cells co-expressed Pdx1 and insulin and by restoration of the vascular laminin expression. The atRA-induced production of vascular endothelial growth factor-A from the pancreatic islets was possibly the key factor that mediated the restoration of islet vascularity and recovery of β-cell mass. Furthermore, the combination of islet transplantation and atRA administration significantly rescued hyperglycemia in diabetic mice. These findings suggest that vitamin A derivatives can potentially be used as a supplementary treatment to improve diabetes management and glycemic control.

Effects of vitamin A deficiency in the postnatal mouse heart: role of hepatic retinoid stores

To determine whether hepatic depletion of vitamin A (VA) stores has an effect on the postnatal heart, studies were carried out with mice lacking liver retinyl ester stores fed either a VA-sufficient (LRVAS) or VA-deficient (LRVAD) diet (to deplete circulating retinol and extrahepatic stores of retinyl esters). There were no observable differences in the weights or gross morphology of hearts from LRVAS or LRVAD mice relative to sex-matched, age-matched, and genetically matched wild-type (WT) controls fed the VAS diet (WTVAS), but changes in the transcription of functionally relevant genes were consistent with a state of VAD in LRVAS and LRVAD ventricles. In silico analysis revealed that 58/67 differentially expressed transcripts identified in a microarray screen are products of genes that have DNA retinoic acid response elements. Flow cytometric analysis revealed a significant and cell-specific increase in the number of proliferating Sca-1 cardiac progenitor cells in LRVAS animals relative to WTVAS controls. Before myocardial infarction, LRVAS and WTVAS mice had similar cardiac systolic function and structure, as measured by echocardiography, but, unexpectedly, repeat echocardiography demonstrated that LRVAS mice had less adverse remodeling by 1 wk after myocardial infarction. Overall, the results demonstrate that the adult heart is responsive to retinoids, and, most notably, reducing hepatic VA stores (while maintaining circulating levels of VA) impacts ventricular gene expression profiles, progenitor cell numbers, and response to injury.

Combined antenatal therapy with retinoic acid and tracheal occlusion in a rat model of congenital diaphragmatic hernia

AIM

To investigate the effect of combined prenatal treatment with retinoic acid (RA) and tracheal occlusion (TO) on the pulmonary vascular morphology and expression of vascular endothelial growth factors (VEGF) and its receptors in a rat model of congenital diaphragmatic hernia (CDH).

MATERIAL AND METHODS

Rats were given nitrofen at 9 days of gestation followed by no treatment (CDH), RA (CDH + RA), TO (CDH + TO), or both (CDH + RA + TO) (n = 16). We measured the median wall thickness of the pulmonary arterioles (MWT) and analyzed the expression of VEGF and its receptors (VEGFR1 and VEGFR2).

RESULTS

Compared to control animals, CDH had increased MWT (44 ± 15 vs. 58 ± 7; p < 0.05) and decreased expression of VEGF, VEGFR1, and VEGFR2 (p < 0.05). Treatment with RA or TO alone, and RA + TO reduced the MWT (46 ± 9, 42 ± 11, 46 ± 8, respectively) and improved the expression of VEGF, VEGFR1, and VEGFR2 compared to CDH (p < 0.05). However, the combination of RA + TO did not confer additional benefit in the reduction of the MWT or in increasing the VEGF and its receptors compared to either treatment alone.

CONCLUSION

Antenatal treatment with either RA or TO improved the MWT and expression of VEGF and its receptors in a CDH rat model. However, combined treatment with RA + TO was not superior to either treatment alone.

A novel all-trans retinoic acid derivative 4-amino‑2‑trifluoromethyl-phenyl retinate inhibits the proliferation of human hepatocellular carcinoma HepG2 cells by inducing G0/G1 cell cycle arrest and apoptosis via upregulation of p53 and ASPP1 and downregulation of iASPP

4-Amino-2-trifluoromethyl-phenyl retinate (ATPR), a novel all-trans retinoic acid (ATRA) derivative, was reported to function as a tumor inhibitor in various types of cancer cells in vitro. However, little is known concerning its antitumor effect on human hepatocellular carcinoma (HCC) HepG2 cells. The aims of the present study were to investigate the effects of ATPR on the proliferation of HepG2 cells and to explore the probable mechanisms. A series of experiments were performed following the treatment of HepG2 cells with ATRA and ATPR. MTT and plate colony formation assays were used to measure the cell viability. To confirm the influence on proliferation, flow cytometry was used to detect the distribution of the cell cycle. Apoptosis was observed by Hoechst staining and flow cytometry. In addition, to characterize the underlying molecular mechanisms, immunofluorescence was applied to observe the distribution of p53. The transcription and translation levels of p53 were analyzed by real-time quantitative RT-PCR (qRT-PCR) and western blotting. The expression levels of murine double minute 2 (MDM2), apoptosis stimulating proteins of p53 (ASPP), cell cycle- and apoptosis-associated proteins were detected by western blotting. After HepG2 cells were incubated with ATRA and ATPR, the viability of the HepG2 cells was inhibited in a dose- and time-dependent manner. As well, ATPR significantly suppressed HepG2 cell colony formation and arrested cells at the G0/G1 phase, while ATRA had no obvious effects. Both Hoechst staining and flow cytometry unveiled the apoptosis of HepG2 cells. Moreover, the fluorescent density of p53 was higher in the nuclei after exposure to ATPR than that in the ATRA group. HepG2 cells treated with ATPR showed elevated mRNA and protein levels of p53 when compared with these levels in the ATRA-treated cells. Western blotting showed that ATPR increased ASPP1, p21 and Bax expression and decreased MDM2, iASPP, cyclin D and E, cyclin-dependent kinase 6 (CDK6) and Bcl-2 expression, while CDK4 and ASPP2 expression were scarcely altered. Consequently, ATPR exerted a better inhibitory effect on the proliferation of HepG2 cells than ATRA through increased expression of p53 and ASPP1 and downregulation of iASPP, thereby resulting in G0/G1 cell cycle arrest and apoptosis.

Retinoic acid-loaded polymeric nanoparticles enhance vascular regulation of neural stem cell survival and differentiation after ischaemia

Stroke is one of the leading causes of death and disability worldwide. However, current therapies only reach a small percentage of patients and may cause serious side effects. We propose the therapeutic use of retinoic acid-loaded nanoparticles (RA-NP) to safely and efficiently repair the ischaemic brain by creating a favourable pro-angiogenic environment that enhances neurogenesis and neuronal restitution. Our data showed that RA-NP enhanced endothelial cell proliferation and tubule network formation and protected against ischaemia-induced death. To evaluate the effect of RA-NP on vascular regulation of neural stem cell (NSC) survival and differentiation, endothelial cell-conditioned media (EC-CM) were collected. EC-CM from healthy RA-NP-treated cells reduced NSC death and promoted proliferation while EC-CM from ischaemic RA-NP-treated cells decreased cell death, increased proliferation and neuronal differentiation. In parallel, human endothelial progenitor cells (hEPC), which are part of the endogenous repair response to vascular injury, were collected from ischaemic stroke patients. hEPC treated with RA-NP had significantly higher proliferation, which further highlights the therapeutic potential of this formulation. To conclude, RA-NP protected endothelial cells from ischaemic death and stimulated the release of pro-survival, proliferation-stimulating factors and differentiation cues for NSC. RA-NP were shown to be up to 83-fold more efficient than free RA and to enhance hEPC proliferation. These data serve as a stepping stone to use RA-NP as vasculotrophic and neurogenic agents for vascular disorders and neurodegenerative diseases with compromised vasculature.

VEGF and endothelium-derived retinoic acid regulate lung vascular and alveolar development

Prevention or treatment of lung diseases caused by the failure to form, or destruction of, existing alveoli, as observed in infants with bronchopulmonary dysplasia and adults with emphysema, requires understanding of the molecular mechanisms of alveolar development. In addition to its critical role in gas exchange, the pulmonary circulation also contributes to alveolar morphogenesis and maintenance by the production of paracrine factors, termed "angiocrines," that impact the development of surrounding tissue. To identify lung angiocrines that contribute to alveolar formation, we disrupted pulmonary vascular development by conditional inactivation of the Vegf-A gene during alveologenesis. This resulted in decreased pulmonary capillary and alveolar development and altered lung elastin and retinoic acid (RA) expression. We determined that RA is produced by pulmonary endothelial cells and regulates pulmonary angiogenesis and elastin synthesis by induction of VEGF-A and fibroblast growth factor (FGF)-18, respectively. Inhibition of RA synthesis in newborn mice decreased FGF-18 and elastin expression and impaired alveolarization. Treatment with RA and vitamin A partially reversed the impaired vascular and alveolar development induced by VEGF inhibition. Thus we identified RA as a lung angiocrine that regulates alveolarization through autocrine regulation of endothelial development and paracrine regulation of elastin synthesis via induction of FGF-18 in mesenchymal cells.

PML-RARa modulates the vascular signature of extracellular vesicles released by acute promyelocytic leukemia cells

Oncogenic transformation is believed to impact the vascular phenotype and microenvironment in cancer, at least in part, through mechanisms involving extracellular vesicles (EVs). We explored these questions in the context of acute promyelocytic leukemia cells (NB4) expressing oncogenic fusion protein, PML-RARa and exquisitely sensitive to its clinically used antagonist, the all-trans retinoic acid (ATRA). We report that NB4 cells produce considerable numbers of EVs, which are readily taken up by cultured endothelial cells triggering their increased survival. NB4 EVs contain PML-RARa transcript, but no detectable protein, which is also absent in endothelial cells upon the vesicle uptake, thereby precluding an active intercellular trafficking of this oncogene in this setting. ATRA treatment changes the emission profile of NB4-related EVs resulting in preponderance of smaller vesicles, an effect that occurs in parallel with the onset of cellular differentiation. ATRA also increases IL-8 mRNA and protein content in NB4 cells and their EVs, while decreasing the levels of VEGF and tissue factor (TF). Endothelial cell uptake of NB4-derived EVs renders these cells more TF-positive and procoagulant, and this effect is diminished by pre-treatment of EV donor cells with ATRA. Profiling angiogenesis-related transcripts in intact and ATRA-treated APL cells and their EVs reveals multiple differences attributable to cellular responses and EV molecular packaging. These observations point to the potential significance of changes in the angiogenic signature and activity associated with EVs released from tumor cells subjected to targeted therapy.

The Use of Chemical-Chemical Interaction and Chemical Structure to Identify New Candidate Chemicals Related to Lung Cancer

Lung cancer causes over one million deaths every year worldwide. However, prevention and treatment methods for this serious disease are limited. The identification of new chemicals related to lung cancer may aid in disease prevention and the design of more effective treatments. This study employed a weighted network, constructed using chemical-chemical interaction information, to identify new chemicals related to two types of lung cancer: non-small lung cancer and small-cell lung cancer. Then, a randomization test as well as chemical-chemical interaction and chemical structure information were utilized to make further selections. A final analysis of these new chemicals in the context of the current literature indicates that several chemicals are strongly linked to lung cancer.

Deregulation of Retinaldehyde Dehydrogenase 2 Leads to Defective Angiogenic Function of Endothelial Colony-Forming Cells in Pediatric Moyamoya Disease

OBJECTIVE--

Moyamoya disease (MMD) is a common cause of childhood stroke, in which the abnormal function of the endothelial colony-forming cell (ECFC) plays a key role in the pathogenesis of the disease. This study was designed to identify genes involved in MMD pathogenesis using gene expression profiling and to understand the defective function of MMD ECFCs.

APPROACH AND RESULTS--

We compared gene expression profiles of ECFCs isolated from patients with MMD and normal controls. Among the differentially expressed genes, we selected a gene with the most downregulated expression, retinaldehyde dehydrogenase 2 (RALDH2). The activity of RALDH2 in MMD ECFCs was assessed by in vitro tube formation assay and in vivo Matrigel plug assay in the presence of all-trans retinoic acid. The transcriptional control of RALDH2 was tested using ChIP assays on acetyl-histone H3. In the results, MMD ECFCs inefficiently formed capillary tubes in vitro and capillaries in vivo, a defect restored by all-trans retinoic acid treatment. Knockdown of RALDH2 mRNA in normal ECFCs also induced decreased activity of capillary formation in vitro. The decreased level of RALDH2 mRNA in MMD ECFCs was attributed to defective acetyl-histone H3 binding to the promoter region.

CONCLUSIONS--

From these results, we conclude that the expression of RALDH2 was epigenetically suppressed in ECFCs from patients with MMD, which may play a key role in their functional impairment.

Effects of all‑trans retinoic acid on VEGF and HIF‑1α expression in glioma cells under normoxia and hypoxia and its anti‑angiogenic effect in an intracerebral glioma model

All‑trans retinoic acid (ATRA) is one of the most potent inducers of differentiation and is capable of inducing differentiation and apoptosis in glioma cells. However, the effect of ATRA on glioma angiogenesis is yet to be elucidated. The present study investigated the effects of ATRA on the expression of vascular endothelial growth factor (VEGF) and hypoxia‑inducible factor‑1α (HIF‑1α) in various glioma cell lines under normoxia and hypoxia. The effect of ATRA on angiogenesis in a rat intracerebral glioma model was also investigated, with the aim of revealing the effect of ATRA on glioma angiogenesis. In the present study, U‑87 MG and SHG44 glioma cells were treated with ATRA at various concentrations (0, 5, 10, 20 and 40 µmol/l) under normoxia or hypoxia. Quantitative polymerase chain reaction and western blot analysis were used to investigate VEGF and HIF‑1α mRNA and protein expression, respectively. An intracerebral glioma model was generated using intracerebral implantation of C6 glioma cells into rats. Tumor‑bearing rats were treated with ATRA at different doses (0, 5 and 10 mg/kg/day) for two weeks, and immunohistochemical assays were performed to detect the cluster of differentiation 34‑positive cells in order to evaluate the microvessel density (MVD) in each group. Following ATRA treatment, the expression of VEGF and HIF‑1α was found to vary among the different concentration groups. In the glioma cells in the lower concentration groups (5 and 10 µmol/l ATRA), a significant increase in VEGF and HIF‑1α expression was observed. Conversely, a significant decrease in VEGF and HIF‑1α expression was found in the glioma cells in the high ATRA concentration group (40 µmol/l), compared with that in the cells in the control group. Furthermore, in the rat intracerebral glioma model, ATRA decreased glioma MVD, particularly in the high‑dose group (10 mg/kg/day), compared with the control group. These results suggest that ATRA may exhibit a dose‑dependent effect on glioma angiogenesis and may inhibit glioma angiogenesis in vivo.

Retinoic acid receptor alpha is associated with tamoxifen resistance in breast cancer

About one-third of oestrogen receptor alpha-positive breast cancer patients treated with tamoxifen relapse. Here we identify the nuclear receptor retinoic acid receptor alpha as a marker of tamoxifen resistance. Using quantitative mass spectrometry-based proteomics, we show that retinoic acid receptor alpha protein networks and levels differ in a tamoxifen-sensitive (MCF7) and a tamoxifen-resistant (LCC2) cell line. High intratumoural retinoic acid receptor alpha protein levels also correlate with reduced relapse-free survival in oestrogen receptor alpha-positive breast cancer patients treated with adjuvant tamoxifen solely. A similar retinoic acid receptor alpha expression pattern is seen in a comparable independent patient cohort. An oestrogen receptor alpha and retinoic acid receptor alpha ligand screening reveals that tamoxifen-resistant LCC2 cells have increased sensitivity to retinoic acid receptor alpha ligands and are less sensitive to oestrogen receptor alpha ligands compared with MCF7 cells. Our data indicate that retinoic acid receptor alpha may be a novel therapeutic target and a predictive factor for oestrogen receptor alpha-positive breast cancer patients treated with adjuvant tamoxifen.

Expression of retinoic acid target genes in coronary artery disease

Coronary atherosclerosis can lead to myocardial infarction, and secondarily to post-infarct remodelling and heart failure. Retinoic acid (RA) influences cell proliferation. We hypothesized that RA could influence gene expression and proliferation of cardiovascular cells. Left ventricular biopsies from patients with end-stage heart failure due to coronary artery disease (CAD) or dilated cardiomyopathy were investigated for the content of RA metabolites using liquid chromatography mass spectrometry (LC-MS/MS), and compared with healthy donors. All-trans retinoic acid (ATRA) was increased in the hearts of CAD patients. Gene expression (quantitative PCR) of RA target genes was not influenced in failing hearts, but was increased in the hearts of patients with CAD undergoing open heart surgery. The expression of RA target genes was increased in atherosclerotic lesions from carotid arteries compared to healthy arteries. Stimulation of cardiomyocytes, cardiofibroblasts, smooth muscle cells and endothelial cells with ATRA increased the gene expression of the key enzymes. Cardiofibroblast and smooth muscle cell proliferation were reduced by ATRA, which increased endothelial cell proliferation. Coronary artery disease leads to increased expression of RA target genes. ATRA accumulated in the failing human heart. All investigated cell types present in the heart had induced expression of RA target genes when stimulated with ATRA, which also influenced cell proliferation.

In Vitro Characterization of Valproic Acid, ATRA, and Cytarabine Used for Disease-Stabilization in Human Acute Myeloid Leukemia: Antiproliferative Effects of Drugs on Endothelial and Osteoblastic Cells and Altered Release of Angioregulatory Mediators by Endothelial Cells

The combined use of the histone deacetylase inhibitor valproic acid (VPA), the retinoic acid receptor- α agonist all-trans retinoic acid (ATRA), and the deoxyribonucleic acid polymerase- α inhibitor cytarabine (Ara-C) is now considered for disease-stabilizing treatment of acute myeloid leukemia (AML). Leukemogenesis and leukemia cell chemoresistance seem to be supported by neighbouring stromal cells in the bone marrow, and we have therefore investigated the effects of these drugs on primary human endothelial cells and the osteoblastic Cal72 cell line. The results show that VPA and Ara-C have antiproliferative effects, and the antiproliferative/cytotoxic effect of Ara-C was seen at low concentrations corresponding to serum levels found during low-dose in vivo treatment. Furthermore, in functional assays of endothelial migration and tube formation VPA elicited an antiangiogenic effect, whereas ATRA elicited a proangiogenic effect. Finally, VPA and ATRA altered the endothelial cell release of angiogenic mediators; ATRA increased levels of CXCL8, PDGF-AA, and VEGF-D, while VPA decreased VEGF-D and PDGF-AA/BB levels and both drugs reduced MMP-2 levels. Several of these mediators can enhance AML cell proliferation and/or are involved in AML-induced bone marrow angiogenesis, and direct pharmacological effects on stromal cells may thus indirectly contribute to the overall antileukemic activity of this triple drug combination.