Elabela and Apelin regulate coronary angiogenesis in a competitive manner.

APJ, a G-protein coupled receptor, regulates coronary angiogenesis in the developing mouse heart. However, the exact mechanism by which APJ regulates coronary angiogenesis from its dual ligands, ELABELA and APELIN, is unclear. Our study show that ELABELA and APELIN both stimulate angiogenic activities such as proliferation and sprouting outgrowth in explant cultures. We found APELIN to be a more robust angiogenic stimulant compared to ELABELA. When explant cultures were stimulated by both ligands together, we found that ELABELA repress the angiogenic activity of APELIN. Collectively, we show that ELABELA and APELIN regulate coronary angiogenesis in a competitive manner.

Bitter melon extract suppresses metastatic breast cancer cells (MCF-7 cells) growth possibly by hindering glucose uptake.

Breast cancer is one of the most commonly diagnosed cancers among women, however the complete cure for metastatic breast cancer is lacking due to poor prognosis. There has been an increasing trend of dietary modifications including consumption of natural food for the prevention of cancer. One of the popular natural foods is bitter melon. Bitter melon grows in tropical and subtropical areas. Some of the beneficial effects of bitter melon towards disease including cancer have been reported at the whole body/organismal level. However, specific cellular mechanisms by which bitter melon exerts beneficial effects in breast cancer are lacking. In this study, we used a human metastatic breast cancer cell line, MCF-7 cell, to study if bitter melon alters glucose clearance from the culture medium. We co-cultured MCF-7 cells with bitter melon extract in the presence and absence of supplemented insulin and subsequently measured MCF-7 cells viability. In this study, we report a noble finding that bitter melon extract exerts cytotoxic effects on MCF-7 cells possibly via inhibition of glucose uptake. Our findings show that insulin rescues MCF-7 cells from the effects of bitter melon extract.

APJ expression is lost in isolated embryonic coronary endothelial cell culture in vitro.

Coronary artery disease is one of the leading causes of death worldwide, and yet we lack the appropriate therapeutic treatments for it. Investigation into the mechanisms of coronary vessel development can provide insights into potential therapies to repair and regenerate damaged coronary arteries. Our previous study in the mouse embryo have implicated APJ, a G-protein coupled receptor that is expressed by coronary endothelial cells in vivo, to be an important regulator of coronary vessel development. In this study, we report an unexpected finding that the isolated embryonic coronary endothelial cells lose APJ expression in culture in vitro.

Hypoxia regulate developmental coronary angiogenesis potentially through VEGFR2- and SOX17-mediated signaling.

Background: Coronary vessels in embryonic mouse heart arises from multiple progenitor population including sinus venosus (SV), endocardium, and proepicardium. ELA/APJ signaling is shown to regulate coronary growth from SV pathway within the subepicardium, whereas VEGF-A/VEGF-R2 pathways is implicated to regulate coronary growth from endocardium pathway. Our previous study show hypoxia as a potential signaling cue to stimulate overall coronary growth and expansion within the myocardium. However, the role of hypoxia and its downstream signaling pathways in the regulation of coronary vessel development is not known. In this study, we investigated the role of hypoxia in coronary vessel development and have identified SOX17- and VEGF-R2-mediated signaling as a potential downstream pathway of hypoxia in the regulation of coronary vessel development. Results: We show that hypoxia gain-of-function in the myocardium through upregulation of HIF-1α disrupts the normal pattern of coronary angiogenesis in developing mouse hearts and displays phenotype that is reminiscent of accelerated coronary growth. We show that VEGF-R2 expression is increased in coronary endothelial cells under hypoxia gain-of-function in vivo and in vitro . Furthermore, we show that SOX17 expression is upregulated in developing mouse heart under hypoxia gain-of-function conditions, whereas SOX17 expression is repressed under hypoxia loss-of-function conditions. Furthermore, our results show that SOX17 loss-of-function disrupts normal pattern of coronary growth. Conclusion: Collectively, our data provide strong phenotypic evidence to show that hypoxia might regulate coronary growth in the developing mouse heart potentially through VEGF-R2- and SOX17-mediated downstream signaling pathways.

APJ+ cells in the SHF contribute to the cells of aorta and pulmonary trunk through APJ signaling.

Outflow tract (OFT) develops from cardiac progenitor cells in the second heart field (SHF) domain. APJ, a G-Protein Coupled Receptor, is expressed by cardiac progenitors in the SHF. By lineage tracing APJ+SHF cells, we show that these cardiac progenitors contribute to the cells of OFT, which eventually give rise to aorta and pulmonary trunk/artery upon its morphogenesis. Furthermore, we show that early APJ â€‹+ â€‹cells give rise to both aorta and pulmonary cells but late APJ â€‹+ â€‹cells predominantly give rise to pulmonary cells. APJ is expressed by the outflow tract progenitors in the SHF but its role is unclear. We performed knockout studies to determine the role of APJ in SHF cell proliferation and survival. Our data suggested that APJ knockout in the SHF reduced the proliferation of SHF progenitors, while there was no significant impact on survival. In addition, we show that ectopic overexpression of WNT in these cells disrupted aorta and pulmonary morphogenesis from OFT. Overall, our study has identified APJ â€‹+ â€‹progenitor population within the SHF that give rise to aorta and pulmonary trunk/artery cells. Furthermore, we show that APJ signaling stimulates proliferation of these cells in the SHF.

Endocardium-to-coronary artery differentiation during heart development and regeneration involves sequential roles of Bmp2 and Cxcl12/Cxcr4.

Endocardial cells lining the heart lumen are coronary vessel progenitors during embryogenesis. Re-igniting this developmental process in adults could regenerate blood vessels lost during cardiac injury, but this requires additional knowledge of molecular mechanisms. Here, we use mouse genetics and scRNA-seq to identify regulators of endocardial angiogenesis and precisely assess the role of CXCL12/CXCR4 signaling. Time-specific lineage tracing demonstrated that endocardial cells differentiated into coronary endothelial cells primarily at mid-gestation. A new mouse line reporting CXCR4 activity-along with cell-specific gene deletions-demonstrated it was specifically required for artery morphogenesis rather than angiogenesis. Integrating scRNA-seq data of endocardial-derived coronary vessels from mid- and late-gestation identified a Bmp2-expressing transitioning population specific to mid-gestation. Bmp2 stimulated endocardial angiogenesis in vitro and in injured neonatal mouse hearts. Our data demonstrate how understanding the molecular mechanisms underlying endocardial angiogenesis can identify new potential therapeutic targets promoting revascularization of the injured heart.

Age-dependent decline in remyelination capacity is mediated by apelin-APJ signaling.

Age-related regeneration failure in the central nervous system can occur as a result of a decline in remyelination efficacy. The responsiveness of myelin-forming cells to signals for remyelination is affected by aging-related epigenetic modification; however, the molecular mechanism is not fully clarified. In the present study, we report that the apelin receptor (APJ) mediates remyelination efficiency with age. APJ expression in myelin-forming cells is correlated with age-associated changes in remyelination efficiency, and the activation of APJ promotes remyelination through the translocation of myelin regulatory factor. APJ signaling activation promoted remyelination in both aged mice with toxin-induced demyelination and mice with experimental autoimmune encephalomyelitis. In human cells, APJ activation enhanced the expression of remyelination markers. Impaired oligodendrocyte function in aged animals can be reversibly reactivated; thus, the results demonstrate that dysfunction of the apelin-APJ system mediates remyelination failure in aged animals, and that their myelinating function can be reactivated by APJ activation.

In Vitro Model of Coronary Angiogenesis.

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects in these vessels represent severe health risks such as in atherosclerosis, which can lead to myocardial infarctions and heart failures in patients. Consequently, coronary artery disease is one of the leading causes of death worldwide. Despite its clinical importance, relatively little progress has been made on how to regenerate damaged coronary arteries. Nevertheless, recent progress has been made in understanding the cellular origin and differentiation pathways of coronary vessel development. The advent of tools and technologies that allow researchers to fluorescently label progenitor cells, follow their fate, and visualize progenies in vivo have been instrumental in understanding coronary vessel development. In vivo studies are valuable, but have limitations in terms of speed, accessibility, and flexibility in experimental design. Alternatively, accurate in vitro models of coronary angiogenesis can circumvent these limitations and allow researchers to interrogate important biological questions with speed and flexibility. The lack of appropriate in vitro model systems may have hindered the progress in understanding the cellular and molecular mechanisms of coronary vessel growth. Here, we describe an in vitro culture system to grow coronary vessels from the sinus venosus (SV) and endocardium (Endo), the two progenitor tissues from which many of the coronary vessels arise. We also confirmed that the cultures accurately recapitulate some of the known in vivo mechanisms. For instance, we show that the angiogenic sprouts in culture from SV downregulate COUP-TFII expression similar to what is observed in vivo. In addition, we show that VEGF-A, a well-known angiogenic factor in vivo, robustly stimulates angiogenesis from both the SV and Endo cultures. Collectively, we have devised an accurate in vitro culture model to study coronary angiogenesis.

A Unique Collateral Artery Development Program Promotes Neonatal Heart Regeneration.

Collateral arteries are an uncommon vessel subtype that can provide alternate blood flow to preserve tissue following vascular occlusion. Some patients with heart disease develop collateral coronary arteries, and this correlates with increased survival. However, it is not known how these collaterals develop or how to stimulate them. We demonstrate that neonatal mouse hearts use a novel mechanism to build collateral arteries in response to injury. Arterial endothelial cells (ECs) migrated away from arteries along existing capillaries and reassembled into collateral arteries, which we termed "artery reassembly". Artery ECs expressed CXCR4, and following injury, capillary ECs induced its ligand, CXCL12. CXCL12 or CXCR4 deletion impaired collateral artery formation and neonatal heart regeneration. Artery reassembly was nearly absent in adults but was induced by exogenous CXCL12. Thus, understanding neonatal regenerative mechanisms can identify pathways that restore these processes in adults and identify potentially translatable therapeutic strategies for ischemic heart disease.

Endothelial deletion of Ino80 disrupts coronary angiogenesis and causes congenital heart disease.

During development, the formation of a mature, well-functioning heart requires transformation of the ventricular wall from a loose trabecular network into a dense compact myocardium at mid-gestation. Failure to compact is associated in humans with congenital diseases such as left ventricular non-compaction (LVNC). The mechanisms regulating myocardial compaction are however still poorly understood. Here, we show that deletion of the Ino80 chromatin remodeler in vascular endothelial cells prevents ventricular compaction in the developing mouse heart. This correlates with defective coronary vascularization, and specific deletion of Ino80 in the two major coronary progenitor tissues-sinus venosus and endocardium-causes intermediate phenotypes. In vitro, endothelial cells promote myocardial expansion independently of blood flow in an Ino80-dependent manner. Ino80 deletion increases the expression of E2F-activated genes and endothelial cell S-phase occupancy. Thus, Ino80 is essential for coronary angiogenesis and allows coronary vessels to support proper compaction of the heart wall.

Alternative Progenitor Cells Compensate to Rebuild the Coronary Vasculature in Elabela- and Apj-Deficient Hearts.

Organogenesis during embryonic development occurs through the differentiation of progenitor cells. This process is extraordinarily accurate, but the mechanisms ensuring high fidelity are poorly understood. Coronary vessels of the mouse heart derive from at least two progenitor pools, the sinus venosus and endocardium. We find that the ELABELA (ELA)-APJ signaling axis is only required for sinus venosus-derived progenitors. Because they do not depend on ELA-APJ, endocardial progenitors are able to expand and compensate for faulty sinus venosus development in Apj mutants, leading to normal adult heart function. An upregulation of endocardial SOX17 accompanied compensation in Apj mutants, which was also seen in Ccbe1 knockouts, indicating that the endocardium is activated in multiple cases where sinus venosus angiogenesis is stunted. Our data demonstrate that by diversifying their responsivity to growth cues, distinct coronary progenitor pools are able to compensate for each other during coronary development, thereby providing robustness to organ development.

Endothelial APLNR regulates tissue fatty acid uptake and is essential for apelin's glucose-lowering effects.

Treatment of type 2 diabetes mellitus continues to pose an important clinical challenge, with most existing therapies lacking demonstrable ability to improve cardiovascular outcomes. The atheroprotective peptide apelin (APLN) enhances glucose utilization and improves insulin sensitivity. However, the mechanism of these effects remains poorly defined. We demonstrate that the expression of APLNR (APJ/AGTRL1), the only known receptor for apelin, is predominantly restricted to the endothelial cells (ECs) of multiple adult metabolic organs, including skeletal muscle and adipose tissue. Conditional endothelial-specific deletion of Aplnr (AplnrECKO ) resulted in markedly impaired glucose utilization and abrogation of apelin-induced glucose lowering. Furthermore, we identified inactivation of Forkhead box protein O1 (FOXO1) and inhibition of endothelial expression of fatty acid (FA) binding protein 4 (FABP4) as key downstream signaling targets of apelin/APLNR signaling. Both the Apln-/- and AplnrECKO mice demonstrated increased endothelial FABP4 expression and excess tissue FA accumulation, whereas concurrent endothelial Foxo1 deletion or pharmacologic FABP4 inhibition rescued the excess FA accumulation phenotype of the Apln-/- mice. The impaired glucose utilization in the AplnrECKO mice was associated with excess FA accumulation in the skeletal muscle. Treatment of these mice with an FABP4 inhibitor abrogated these metabolic phenotypes. These findings provide mechanistic insights that could greatly expand the therapeutic repertoire for type 2 diabetes and related metabolic disorders.

Coronary Artery Development: Progenitor Cells and Differentiation Pathways.

Coronary artery disease (CAD) is the number one cause of death worldwide and involves the accumulation of plaques within the artery wall that can occlude blood flow to the heart and cause myocardial infarction. The high mortality associated with CAD makes the development of medical interventions that repair and replace diseased arteries a high priority for the cardiovascular research community. Advancements in arterial regenerative medicine could benefit from a detailed understanding of coronary artery development during embryogenesis and of how these pathways might be reignited during disease. Recent research has advanced our knowledge on how the coronary vasculature is built and revealed unexpected features of progenitor cell deployment that may have implications for organogenesis in general. Here, we highlight these recent findings and discuss how they set the stage to interrogate developmental pathways during injury and disease.

Isolated extraocular orbital mass: a rare presentation of sarcoidosis.

We report a case of orbital sarcoidosis in a 66 year old male who presented with one month history of right eye swelling and intermittent diplopia. MRI revealed an enhancing infiltrative soft tissue mass in the inferior aspect of the right orbit and biopsy of the mass demonstrated non-necrotizing granulomas. Chest CT scan was normal and PET scan showed no other organ involvement. He was treated with tapering doses of prednisone over six months. Although relapse occurred while tapering prednisone to 20 mg per day, he responded well to the addition of azathioprine with complete resolution of visual difficulties and orbital the mass on repeat MRI. Sarcoidosis, presenting as an isolated orbital mass is rare, can be successfully treated and should be included in differential diagnosis.

Notch: A multi-functional integrating system of microenvironmental signals.

The Notch signaling cascade is an evolutionarily ancient system that allows cells to interact with their microenvironmental neighbors through direct cell-cell interactions, thereby directing a variety of developmental processes. Recent research is discovering that Notch signaling is also responsive to a broad variety of stimuli beyond cell-cell interactions, including: ECM composition, crosstalk with other signaling systems, shear stress, hypoxia, and hyperglycemia. Given this emerging understanding of Notch responsiveness to microenvironmental conditions, it appears that the classical view of Notch as a mechanism enabling cell-cell interactions, is only a part of a broader function to integrate microenvironmental cues. In this review, we summarize and discuss published data supporting the idea that the full function of Notch signaling is to serve as an integrator of microenvironmental signals thus allowing cells to sense and respond to a multitude of conditions around them.

The sinus venosus contributes to coronary vasculature through VEGFC-stimulated angiogenesis.

Identifying coronary artery progenitors and their developmental pathways could inspire novel regenerative treatments for heart disease. Multiple sources of coronary vessels have been proposed, including the sinus venosus (SV), endocardium and proepicardium, but their relative contributions to the coronary circulation and the molecular mechanisms regulating their development are poorly understood. We created an ApjCreER mouse line as a lineage-tracing tool to map SV-derived vessels onto the heart and compared the resulting lineage pattern with endocardial and proepicardial contributions to the coronary circulation. The data showed a striking compartmentalization to coronary development. ApjCreER-traced vessels contributed to a large number of arteries, capillaries and veins on the dorsal and lateral sides of the heart. By contrast, untraced vessels predominated in the midline of the ventral aspect and ventricular septum, which are vessel populations primarily derived from the endocardium. The proepicardium gave rise to a smaller fraction of vessels spaced relatively uniformly throughout the ventricular walls. Dorsal (SV-derived) and ventral (endocardial-derived) coronary vessels developed in response to different growth signals. The absence of VEGFC, which is expressed in the epicardium, dramatically inhibited dorsal and lateral coronary growth but left vessels on the ventral side unaffected. We propose that complementary SV-derived and endocardial-derived migratory routes unite to form the coronary vasculature and that the former requires VEGFC, revealing its role as a tissue-specific mediator of blood endothelial development.

Lumican exhibits anti-angiogenic activity in a context specific manner.

A series of overexpression studies have shown that lumican suppresses angiogenesis in tumors produced from pancreatic adenocarcinoma, fibrosarcoma, and melanoma tumor cells. Despite lumican's anti-angiogenic activity, a clear correlation of differential expression of lumican in various cancers and cancer malignancy has failed to emerge. Therefore, we hypothesized that either 1.) endogenously expressed lumican is not anti-angiogenic or alternatively that 2.) lumican exhibits angiostatic activity only in limited microenvironments. Previously, lumican was shown to suppress tumor growth and angiogenesis in subcutaneously injected PanO2 pancreatic adenocarcinoma cells. Therefore, to determine if endogenously expressed lumican is anti-angiogenic we subcutaneously injected PanO2 cells into wild-type and lumican knockout mice and compared tumor growth and vascular densities of the resulting tumors. We found that tumors grown in lumican knockout animals were larger and contained significantly elevated vascular densities compared to those grown in wild-type mice. Interestingly however lumican knockout animals did not exhibit enhanced angiogenesis in aortic ring assays, matrigel plugs, or healing wound biopsies raising the possibility that lumican suppresses angiogenesis only in tumor microenvironments. To test this possibility, we sought a tumor model wherein lumican did not exhibit anti-angiogenic activity. Utilizing the 4T1 breast cancer model, we found that lumican suppressed 4T1 tumor growth and lung metastasis, but not angiogenesis. In conclusion, these results show that the angiostatic activity of lumican is dependent on currently undefined microenvironmental cues and therefore helps to understand why differential expression of lumican does not consistently correlate with human tumor malignancy.

Matrix Gla protein reinforces angiogenic resolution.

Matrix Gla Protein (MGP) is an ECM molecule commonly associated with dysfunctions of large blood vessels such as arteriosclerosis and atherosclerosis. However, the exact role of MGP in the microvasculature is not clear. Utilizing a mouse MGP knockout model we found that MGP suppresses angiogenic sprouting from mouse aorta restricts microvascular density in cardiac and skeletal muscle, and is an endogenous inhibitor of tumor angiogenesis. Similarly, morpholino based knockdown of MGP in zebrafish embryos caused a progressive loss of luminal structures in intersegmental vessels, a phenotype reminiscent of Dll4/Notch inhibition. Accordingly, MGP suppressed Notch-dependent Hes-1 promoter activity and expression of Jagged1 mRNA relative to Dll4 mRNA. However, inhibition of BMP but not Notch or VEGF signaling reversed the excessive angiogenic sprouting phenotype of MGP knockout aortic rings suggesting that MGP may normally suppress angiogenic sprouting by blocking BMP signaling. Collectively, these results suggest that MGP is a multi-functional inhibitor of normal and abnormal angiogenesis that may function by coordinating with both Notch and BMP signaling pathways.