Angiopoietin-like 7 secretion is induced by glaucoma stimuli and its concentration is elevated in glaucomatous aqueous humor

ANGPTL7 and Its Role in IOP and Glaucoma

Purpose

Loss-of-function variants in the ANGPTL7 gene are associated with protection from glaucoma and reduced intraocular pressure (IOP). We investigated the role of ANGPTL7 in IOP homeostasis and its potential as a target for glaucoma therapeutics.

Methods

IOP, outflow facility, and outflow tissue morphology of Angptl7 knockout (KO) mice were assessed with and without dexamethasone (Dex). ANGPTL7 was quantified in conditioned media from human trabecular meshwork cells in response to Dex, in effluent from perfused human donor eyes, and in aqueous humor from human patients treated with steroids. Antibodies to ANGPTL7 were generated and tested in three-dimensional (3D) culture of outflow cells and perfused human donor eyes. Rabbits were injected intravitreally with a neutralizing antibody targeting ANGPTL7, and IOP was measured.

Results

IOP was significantly elevated, but outflow facility and outflow tissue morphology were not different between Angptl7 KO mice and littermates. When challenged with Dex, IOP increased in wild-type but not Angptl7 KO mice. In human samples, increased ANGPTL7 was seen in the aqueous humor of patients treated with steroids, regardless of glaucoma status. Using 3D culture, recombinant ANGPTL7 decreased, and ANGPTL7-blocking antibodies increased hydraulic conductivity. Significantly, outflow facility increased in human eyes treated ex vivo with ANGPTL7-blocking antibodies, and IOP decreased for 21 days in rabbits after a single injection of blocking antibodies.

Conclusions

Using multiple models, we have demonstrated that excess ANGPTL7 increases outflow resistance and IOP and that neutralizing ANGPTL7 has beneficial effects in both naïve and steroid-induced hypertensive eyes, thus motivating the development of ANGPTL7-targeting therapeutics for the treatment of glaucoma.

Angiopoietin-Like Proteins: Cardiovascular Biology and Therapeutic Targeting for the Prevention of Cardiovascular Diseases

Despite the best pharmacologic tools available, cardiovascular diseases (CVDs) remain a major cause of morbidity and mortality in developed countries. After 2 decades of research, new therapeutic targets, such as angiopoietin-like proteins (ANGPTLs), are emerging. ANGPTLs belong to a family of 8 members, from ANGPTL1 to ANGPTL8; they have structural homology with angiopoietins and are secreted in the circulation. ANGPTLs display a multitude of physiological and pathologic functions; they contribute to inflammation, angiogenesis, cell death, senescence, hematopoiesis, and play a role in repair, maintenance, and tissue homeostasis. ANGPTLs-particularly the triad ANGPTL3, 4, and 8-have an established role in lipid metabolism through the regulation of triacylglycerol trafficking according to the nutritional status. Some ANGPTLs also contribute to glucose metabolism. Therefore, dysregulation in ANGPTL expression associated with abnormal circulating levels are linked to a plethora of CVD and metabolic disorders including atherosclerosis, heart diseases, diabetes, but also obesity and cancers. Because ANGPTLs bind to different receptors according to the cell type, antagonists are therapeutically inadequate. Recently, direct inhibitors of ANGPTLs, mainly ANGPTL3, have been developed, and specific monoclonal antibodies and antisense oligonucleotides are currently being tested in clinical trials. The aim of the current review is to provide an up-to-date preclinical and clinical overview on the function of the 8 members of the ANGPTL family in the cardiovascular system, their contribution to CVD, and the therapeutic potential of manipulating some of them.

Integrated Analysis of Transcriptome and Proteome of the Human Cornea and Aqueous Humor Reveal Novel Biomarkers for Corneal Endothelial Cell Dysfunction

Earlier studies have reported that elevated protein levels in the aqueous humor (AH) are associated with corneal endothelial cell dysfunction (CECD), but the details of the underlying mechanism as well as specific biomarkers for CECD remain elusive. In the present study, we aimed to identify protein markers in AH directly associated with changes to corneal endothelial cells (CECs), as AH can be easily obtained for analysis. We carried out an in-depth proteomic analysis of patient-derived AH as well as transcriptomic analysis of CECs from the same patients with bullous keratopathy (BK) resulting from CECD. We first determined differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) from CECs and AH in CECD, respectively. By combining transcriptomic and proteomic analyses, 13 shared upregulated markers and 22 shared downregulated markers were observed between DEGs and DEPs. Among these 35 candidates from biomarker profiling, three upregulated markers were finally verified via data-independent acquisition (DIA) proteomic analysis using additional individual AH samples, namely metallopeptidase inhibitor 1 (TIMP1), Fc fragment of IgG binding protein (FCGBP), and angiopoietin-related protein 7 (ANGPTL7). Furthermore, we confirmed these AH biomarkers for CECD using individual immunoassay validation. Conclusively, our findings may provide valuable insights into the disease process and identify biofluid markers for the assessment of CEC function during BK development.

Rare protective variants and glaucoma-relevant cell stressors modulate Angiopoietin-like 7 expression

Rare missense and nonsense variants in the Angiopoietin-like 7 (ANGPTL7) gene confer protection from primary open-angle glaucoma (POAG), though the functional mechanism remains uncharacterized. Interestingly, a larger variant effect size strongly correlates with in silico predictions of increased protein instability (r = -0.98), suggesting that protective variants lower ANGPTL7 protein levels. Here, we show that missense and nonsense variants cause aggregation of mutant ANGPTL7 protein in the endoplasmic reticulum (ER) and decreased levels of secreted protein in human trabecular meshwork (TM) cells; a lower secreted:intracellular protein ratio strongly correlates with variant effects on intraocular pressure (r = 0.81). Importantly, accumulation of mutant protein in the ER does not increase expression of ER stress proteins in TM cells (P > 0.05 for all variants tested). Cyclic mechanical stress, a glaucoma-relevant physiologic stressor, also significantly lowers ANGPTL7 expression in primary cultures of human Schlemm's canal (SC) cells (-2.4-fold-change, P = 0.01). Collectively, these data suggest that the protective effects of ANGPTL7 variants in POAG stem from lower levels of secreted protein, which may modulate responses to physiologic and pathologic ocular cell stressors. Downregulation of ANGPTL7 expression may therefore serve as a viable preventative and therapeutic strategy for this common, blinding disease.

Metastasis from the tumor interior and necrotic core formation are regulated by breast cancer-derived angiopoietin-like 7

Necrosis in the tumor interior is a common feature of aggressive cancers that is associated with poor clinical prognosis and the development of metastasis. How the necrotic core promotes metastasis remains unclear. Here, we report that emergence of necrosis inside the tumor is correlated temporally with increased tumor dissemination in a rat breast cancer model and in human breast cancer patients. By performing spatially focused transcriptional profiling, we identified angiopoietin-like 7 (Angptl7) as a tumor-specific factor localized to the perinecrotic zone. Functional studies showed that Angptl7 loss normalizes central necrosis, perinecrotic dilated vessels, metastasis, and reduces circulating tumor cell counts to nearly zero. Mechanistically, Angptl7 promotes vascular permeability and supports vascular remodeling in the perinecrotic zone. Taken together, these findings show that breast tumors actively produce factors controlling central necrosis formation and metastatic dissemination from the tumor core.

ANGPTL7, a therapeutic target for increased intraocular pressure and glaucoma

Glaucoma is a leading cause of blindness. Current glaucoma medications work by lowering intraocular pressure (IOP), a risk factor for glaucoma, but most treatments do not directly target the pathological changes leading to increased IOP, which can manifest as medication resistance as disease progresses. To identify physiological modulators of IOP, we performed genome- and exome-wide association analysis in >129,000 individuals with IOP measurements and extended these findings to an analysis of glaucoma risk. We report the identification and functional characterization of rare coding variants (including loss-of-function variants) in ANGPTL7 associated with reduction in IOP and glaucoma protection. We validated the human genetics findings in mice by establishing that Angptl7 knockout mice have lower (~2 mmHg) basal IOP compared to wild-type, with a trend towards lower IOP also in heterozygotes. Conversely, increasing murine Angptl7 levels via injection into mouse eyes increases the IOP. We also show that acute Angptl7 silencing in adult mice lowers the IOP (~2-4 mmHg), reproducing the observations in knockout mice. Collectively, our data suggest that ANGPTL7 is important for IOP homeostasis and is amenable to therapeutic modulation to help maintain a healthy IOP that can prevent onset or slow the progression of glaucoma.

Short and long-term effect of dexamethasone on the transcriptome profile of primary human trabecular meshwork cells in vitro

In the quest of identifying newer molecular targets for the management of glucocorticoid-induced ocular hypertension (GC-OHT) and glaucoma (GCG), several microarray studies have attempted to investigate the genome-wide transcriptome profiling of primary human trabecular meshwork (TM) cells in response to dexamethasone (DEX). However, no studies are reported so far to demonstrate the temporal changes in the expression of genes in the cultured human TM cells in response to DEX treatment. Therefore, in the present study, the time-dependent changes in the genome-wide expression of genes in primary human TM cells after short (16 hours: 16 h) and long exposure (7 days: 7 d) of DEX was investigated using RNA sequencing. There were 199 (118 up-regulated; 81 down-regulated) and 525 (119 up-regulated; 406 down-regulated) DEGs in 16 h and 7 d treatment groups respectively. The unique genes identified in 16 h and 7 d treatment groups were 152 and 478 respectively. This study found a distinct gene signature and pathways between two treatment regimes. Longer exposure of DEX treatment showed a dys-regulation of Wnt and Rap1 signaling and so highlighted potential therapeutic targets for pharmacological management of GC-OHT/glaucoma.

ANGPTL7 is transcriptionally regulated by SP1 and modulates glucocorticoid-induced cross-linked actin networks in trabecular meshwork cells via the RhoA/ROCK pathway

Glaucoma is one of the leading causes of worldwide irreversible blindness. Lowering elevated intraocular pressure (IOP) is currently the only effective approach for controlling the progress of glaucoma. Angiopoietin-like 7 (ANGPTL7) takes a key part in elevated outflow resistance of aqueous humor in dysfunctional trabecular meshwork (TM), along with the formation of cross-linked actin networks (CLANs), leading to high IOP. In this study, we explored the role of the ANGPTL7 signaling pathway in CLAN formation. We detected the expression of ANGPTL7 in cultured primary TM cells treated with dexamethasone (DEX) and ethanol as a control using qRT-PCR and western blotting. Actin filaments were revealed by phalloidin staining. ANGPTL7 short hairpin RNA (shRNA) was applied to TM cells to examine the effect of ANGPTL7 on DEX-induced CLAN formation. Western blotting was used to assess the effect of ANGPTL7 on the RhoA/Rho-associated kinase (Rho-kinase/ROCK) signaling pathway. Bioinformatics, dual-luciferase reporter assays, and chromatin immunoprecipitation were employed to identify the transcription factors of ANGPTL7. Transcription factor specificity protein 1 (SP1) overexpression and silencing were performed to determine their roles in the modulation of ANGPTL7 expression. We found DEX-induced ANGPTL7 expression and stress fiber rearrangement in TM cells. ANGPTL7 knockdown effectively inhibited the formation of CLANs. Moreover, it was involved in the regulation of the RhoA/ROCK signaling pathway, further affecting DEX-induced CLAN formation. SP1 was identified as a transcription factor of ANGPTL7 which regulated ANGPTL7 level to mediate CLAN formation through the RhoA/ROCK signaling pathway. This study contributes to revealing the molecular mechanisms of ANGPTL7 in CLAN formation, which is involved in TM dysfunction and glaucoma pathogenesis.

Replacement of the Trabecular Meshwork Cells-A Way Ahead in IOP Control?

Glaucoma is one of the leading causes of vision loss worldwide, characterised with irreversible optic nerve damage and progressive vision loss. Primary open-angle glaucoma (POAG) is a subset of glaucoma, characterised by normal anterior chamber angle and raised intraocular pressure (IOP). Reducing IOP is the main modifiable factor in the treatment of POAG, and the trabecular meshwork (TM) is the primary site of aqueous humour outflow (AH) and the resistance to outflow. The structure and the composition of the TM are key to its function in regulating AH outflow. Dysfunction and loss of the TM cells found in the natural ageing process and more so in POAG can cause abnormal extracellular matrix (ECM) accumulation, increased TM stiffness, and increased IOP. Therefore, repair or regeneration of TM's structure and function is considered as a potential treatment for POAG. Cell transplantation is an attractive option to repopulate the TM cells in POAG, but to develop a cell replacement approach, various challenges are still to be addressed. The choice of cell replacement covers autologous or allogenic approaches, which led to investigations into TM progenitor cells, induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs) as potential stem cell source candidates. However, the potential plasticity and the lack of definitive cell markers for the progenitor and the TM cell population compound the biological challenge. Morphological and differential gene expression of TM cells located within different regions of the TM may give rise to different cell replacement or regenerative approaches. As such, this review describes the different approaches taken to date investigating different cell sources and their differing cell isolation and differentiation methodologies. In addition, we highlighted how these approaches were evaluated in different animal and ex vivo model systems and the potential of these methods in future POAG treatment.

Altered Expression of Secreted Mediator Genes That Mediate Aggressive Breast Cancer Metastasis to Distant Organs

Simple Summary

Heterogeneity is the characteristic of breast tumors, making it difficult to understand the molecular mechanism. Alteration of gene expression in the primary tumor versus the metastatic lesion remains challenging for getting any specific targeted therapy. To better understand how gene expression profile changes during metastasis, we compare the primary tumor and distant metastatic tumor gene expression using primary breast tumors compared with its metastatic variant in animal models. Our RNA sequencing data from cells revealed that parental cell and the metastatic variant cell are different in gene expression while gene signature significantly altered during metastasis to distant organs than primary breast tumors. We found that secreted mediators encoding genes (ANGPTL7, MMP3, LCN2, S100A8, and ESM1) are correlated with poor prognosis in the clinical setting as divulged from METABRIC and TCGA-BRCA cohort data analysis.

Abstract

Due to the heterogeneous nature of breast cancer, metastasis organotropism has been poorly understood. This study assessed the specific cancer-related gene expression changes occurring with metastatic breast cancer recurrence to distant organs compared with non-metastatic breast cancer. We found that several secreted mediators encoding genes notably, LCN2 and S100A8 overexpressed at the distant metastatic site spine (LCN2, 5-fold; S100A8, 6-fold) and bone (LCN2, 5-fold; S100A8, 3-fold) vs. primary tumors in the syngeneic implantation/tumor-resection metastasis mouse model. In contrast, the ESM-1 encoding gene is overexpressed in the primary tumors and markedly downregulated at distant metastatic sites. Further digging into TCAGA-BRCA, SCAN-B, and METABRIC cohorts data analysis revealed that LCN2, S100A8, and ESM-1 mediators encoding individual gene expression scores were strongly associated with disease-specific survival (DSS) in the METABRIC cohort (hazard ratio (HR) > 1, p < 0.0004). The gene expression scores predicted worse clinically aggressive tumors, such as high Nottingham histological grade and advanced cancer staging. Higher gene expression score of ESM-1 gene was strongly associated with worse overall survival (OS) in the triple-negative breast cancer (TNBC) and hormonal receptor (HR)-positive/HER2-negative subtype in METABRIC cohort, HER2+ subtype in TCGA-BRCA and SCAN-B breast cancer cohorts. Our data suggested that mediators encoding genes with prognostic and predictive values may be clinically useful for breast cancer spine, bone, and lung metastasis, particularly in more aggressive subtypes such as TNBC and HER2+ breast cancer.

Alterations in proteome of human sclera associated with primary open-angle glaucoma involve proteins participating in regulation of the extracellular matrix

Purpose

Primary open-angle glaucoma (POAG) is a common ocular disease, associated with abnormalities in aqueous humor circulation and an increase in intraocular pressure (IOP), leading to progressive optical neuropathy and loss of vision. POAG pathogenesis includes alterations of the structural properties of the sclera, especially in the optic nerve head area, contributing to the degeneration of the retinal ganglion cells. Abnormal sclera biomechanics hinder adequate compensation of IOP fluctuations, thus aggravating POAG progression. The proteomic basis of biomechanical disorders in glaucomatous sclera remains poorly understood. This study is aimed at revealing alterations in major scleral proteins, associated with POAG, at different stages of the disease and with different IOP conditions.

Methods

Samples of sclera were collected from 67 patients with POAG during non-penetrating deep sclerectomy and from nine individuals without POAG. Scleral proteins were extracted with a strong lysis buffer, containing a combination of an ionic detergent, a chaotropic agent, and a disulfide reducing agent, and were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The major scleral proteins were selected, subjected to in-gel digestion, and identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF)/TOF mass spectrometry (MS), coupled with tandem mass spectrometry (MS/MS). The specific POAG-associated alterations of the selected proteins were analyzed with SDS-PAGE and confirmed with western blotting of the scleral extracts, using the respective antibodies. The group of POAG-associated proteins was analyzed using Gene Ontology and genome-wide association study enrichment and protein-protein interaction network prediction.

Results

A total of 11 proteins were identified, among which six proteins, namely, vimentin, angiopoietin-related protein 7, annexin A2, serum amyloid P component, serum albumin, and thrombospondin-4, were found to be upregulated in the sclera of patients with advanced and terminal POAG. In the early stages of the disease, thrombospondin-4 level was, on the contrary, reduced when compared with the control, whereas the concentration of vimentin varied, depending on the IOP level. Moreover, angiopoietin-related protein 7 manifested as two forms, exhibiting opposite behavior: The common 45 kDa form grew with the progression of POAG, whereas the 35 kDa (apparently non-glycosylated) form was absent in the control samples, appeared in patients with early POAG, and decreased in concentration over the course of the disease. Functional bioinformatics analysis linked the POAG-associated proteins with IOP alterations and predicted their secretion into extracellular space and their association with extracellular vesicles and a collagen-containing extracellular matrix.

Conclusions

POAG is accompanied by alterations of the scleral proteome, which represent a novel hallmark of the disease and can reflect pathological changes in scleral biochemistry and biomechanics. The potential mechanisms underlying these changes relate mainly to the structure of the extracellular matrix, protein glycosylation, and calcium binding, and may involve fibroblast cytoskeleton regulation, as well as oxidative and inflammatory responses.

Molecular taxonomy of human ocular outflow tissues defined by single-cell transcriptomics

Ocular hypertension is the primary and only modifiable risk factor for glaucoma, the leading cause of irreversible blindness. Intraocular pressure is regulated homeostatically by resistance to aqueous humor outflow through an architecturally complex tissue, the conventional/trabecular pathway. In this study, we generated a comprehensive cell atlas of the human trabecular meshwork and neighboring tissues using single-cell RNA sequencing. We identified 12 distinct cell types and mapped region-specific expression of candidate genes. The utility of our atlas was demonstrated by mapping glaucoma-relevant genes to conventional outflow cell types. Our study provides a comprehensive molecular and cellular classification of tissue structures responsible for intraocular pressure homeostasis in health and dysregulation in disease.

The conventional outflow pathway is a complex tissue responsible for maintaining intraocular pressure (IOP) homeostasis. The coordinated effort of multiple cells with differing responsibilities ensures healthy outflow function and IOP maintenance. Dysfunction of one or more resident cell types results in ocular hypertension and risk for glaucoma, a leading cause of blindness. In this study, single-cell RNA sequencing was performed to generate a comprehensive cell atlas of human conventional outflow tissues. We obtained expression profiles of 17,757 genes from 8,758 cells from eight eyes of human donors representing the outflow cell transcriptome. Upon clustering analysis, 12 distinct cell types were identified, and region-specific expression of candidate genes was mapped in human tissues. Significantly, we identified two distinct expression patterns (myofibroblast- and fibroblast-like) from cells located in the trabecular meshwork (TM), the primary structural component of the conventional outflow pathway. We also located Schwann cell and macrophage signatures in the TM. The second primary component structure, Schlemm’s canal, displayed a unique combination of lymphatic/blood vascular gene expression. Other expression clusters corresponded to cells from neighboring tissues, predominantly in the ciliary muscle/scleral spur, which together correspond to the uveoscleral outflow pathway. Importantly, the utility of our atlas was demonstrated by mapping glaucoma-relevant genes to outflow cell clusters. Our study provides a comprehensive molecular and cellular classification of conventional and unconventional outflow pathway structures responsible for IOP homeostasis.

Rare protein-altering variants in ANGPTL7 lower intraocular pressure and protect against glaucoma

Protein-altering variants that are protective against human disease provide in vivo validation of therapeutic targets. Here we use genotyping data from UK Biobank (n = 337,151 unrelated White British individuals) and FinnGen (n = 176,899) to conduct a search for protein-altering variants conferring lower intraocular pressure (IOP) and protection against glaucoma. Through rare protein-altering variant association analysis, we find a missense variant in ANGPTL7 in UK Biobank (rs28991009, p.Gln175His, MAF = 0.8%, genotyped in 82,253 individuals with measured IOP and an independent set of 4,238 glaucoma patients and 250,660 controls) that significantly lowers IOP (β = -0.53 and -0.67 mmHg for heterozygotes, -3.40 and -2.37 mmHg for homozygotes, P = 5.96 x 10-9 and 1.07 x 10-13 for corneal compensated and Goldman-correlated IOP, respectively) and is associated with 34% reduced risk of glaucoma (P = 0.0062). In FinnGen, we identify an ANGPTL7 missense variant at a greater than 50-fold increased frequency in Finland compared with other populations (rs147660927, p.Arg220Cys, MAF Finland = 4.3%), which was genotyped in 6,537 glaucoma patients and 170,362 controls and is associated with a 29% lower glaucoma risk (P = 1.9 x 10-12 for all glaucoma types and also protection against its subtypes including exfoliation, primary open-angle, and primary angle-closure). We further find three rarer variants in UK Biobank, including a protein-truncating variant, which confer a strong composite lowering of IOP (P = 0.0012 and 0.24 for Goldman-correlated and corneal compensated IOP, respectively), suggesting the protective mechanism likely resides in the loss of interaction or function. Our results support inhibition or down-regulation of ANGPTL7 as a therapeutic strategy for glaucoma.

Stem Cells from Human Trabecular Meshwork Hold the Potential to Develop into Ocular and Non-Ocular Lineages After Long-Term Storage

Stem cells from the eye hold a great potential for vision restoration and can also be used for regeneration in other tissues. In this study, we characterized the stem cell properties of Trabecular meshwork stem cells (TMSCs) after long-term cryopreservation (∼8 years). TMSCs derived from four donors were examined for their viability and proliferation, as well as stem cell marker expression. Spheroid formation, colony formation, and multipotency were investigated. We observed that TMSCs were fully viable with variable proliferation ability. They expressed the stem cell markers CD90, CD166, CD105, CD73, OCT4, SSEA4, Notch1, KLF4, ABCG2, Nestin, and HNK1 detected by flow cytometry, quantitative polymerase chain reaction, or immunofluorescent staining. They could form spheroids and colonies after thawing. All TMSCs were able to differentiate into osteocytes, neural cells, and trabecular meshwork (TM) cells, but not adipocytes. Differentiated TM cells responded to dexamethasone treatment with increased expression of myocilin and angiopoietin-like 7 (ANGPTL7). In a nutshell, our study demonstrated that TMSCs retain their stem cell properties after long-term cryopreservation and hence can be an effective cell therapy source for various clinical applications.

Effect of ANGPTL7 on Proliferation and Differentiation of MC3T3-E1 Cells

BACKGROUND Angiopoietin-like proteins (ANGPTL) are a family of secretory glycoproteins that are involved in many pathophysiological processes. ANGPTL7 is a newly-discovered member of the ANGPTL family and plays a role in corneal morphogenesis, angiogenesis, glaucoma, and cancer. To date, whether ANGPTL7 is involved in osteoporosis is unknown. Therefore, to discover the effects of ANGPTL7 on osteoporosis, we explored the expression of ANGPTL7 in preosteoblasts and assessed the mechanism underlying its effects on proliferation and differentiation abilities of preosteoblasts. MATERIAL AND METHODS Mouse MC3T3-E1 cells were cultured in osteogenic medium for osteogenic differentiation. The expression levels of ANGPTL7 were detected by RT-qPCR and Western blot assays. Moreover, the overexpressed plasmid of ANGPTL7 pMSCV-ANGPTL7 was transfected into MC3T3-E1 cells. CCK-8 was used to evaluate cell proliferation. ALP activity detection and alizarin red staining were performed to measure the effect of ANGPTL7 on osteogenic differentiation. The expression levels bone morphogenetic proteins (BMPs) and osteogenic markers ALP, runt-related transcription factor 2 (Runx2), osteocalcin (OCN), and collagen I (Col I) were analyzed by Western blot. RESULTS When MC3T3-E1 cells were exposed to osteogenic medium, there was a significant increase in ANGPTL7, and overexpression of ANGPTL7 markedly promoted cell proliferation, ALP activity, and mineralization. Moreover, ANGPTL7 upregulated the levels of BMPs, especially BMP2/7, and the osteogenic markers ALP, Runx2, OCN, and Col I. CONCLUSIONS The results suggest that by regulating the expression of BMPs, ANGPTL7 directly promotes proliferation, differentiation, and mineralization of osteoblasts.

Role of Fibronectin in Primary Open Angle Glaucoma

Primary open angle glaucoma (POAG) is the most common form of glaucoma and the 2nd most common cause of irreversible vision loss in the United States. Nearly 67 million people have the disease worldwide including >3 million in the United States. A major risk factor for POAG is an elevation in intraocular pressure (IOP). The increase in IOP is believed to be caused by an increase in the deposition of extracellular matrix proteins, in particular fibronectin, in a region of the eye known as the trabecular meshwork (TM). How fibronectin contributes to the increase in IOP is not well understood. The increased density of fibronectin fibrils is thought to increase IOP by altering the compliance of the trabecular meshwork. Recent studies, however, also suggest that the composition and organization of fibronectin fibrils would affect IOP by changing the cell-matrix signaling events that control the functional properties of the cells in the trabecular meshwork. In this article, we will discuss how changes in the properties of fibronectin and fibronectin fibrils could contribute to the regulation of IOP.

Identification of genes involved in glaucoma pathogenesis using combined network analysis and empirical studies

Glaucoma is a leading cause of blindness. We aimed in this study to identify genes that may make subtle and cumulative contributions to glaucoma pathogenesis. To this end, we identified molecular interactions and pathways that include transcription factors (TFs) FOXC1, PITX2, PAX6 and NFKB1 and various microRNAs including miR-204 known to have relevance to trabecular meshwork (TM) functions and/or glaucoma. TM tissue is involved in glaucoma pathogenesis. In-house microarray transcriptome results and data sources were used to identify target genes of the regulatory molecules. Bioinformatics analyses were done to filter TM and glaucoma relevant genes. These were submitted to network-creating softwares to define interactions, pathways and a network that would include the genes. The network was stringently scrutinized and minimized, then expanded by addition of microarray data and data on TF and microRNA-binding sites. Selected features of the network were confirmed by empirical studies such as dual luciferase assays, real-time PCR and western blot experiments and apoptosis assays. MYOC, WDR36, LTPBP2, RHOA, CYP1B1, OPA1, SPARC, MEIS2, PLEKHG5, RGS5, BBS5, ALDH1A1, NOMO2, CXCL6, FMNL2, ADAMTS5, CLOCK and DKK1 were among the genes included in the final network. Pathways identified included those that affect ECM properties, IOP, ciliary body functions, retinal ganglion cell viability, apoptosis, focal adhesion and oxidative stress response. The identification of many genes potentially involved in glaucoma pathology is consistent with its being a complex disease. The inclusion of several known glaucoma-related genes validates the approach used.

Angiopoietin-Like Protein 7 Promotes an Inflammatory Phenotype in RAW264.7 Macrophages Through the P38 MAPK Signaling Pathway

Angiopoietin-like protein 7 (Angptl7) has been extensively studied for decades, but its potential immune functions have not been characterized. Hence, we investigated the relationship between Angptl7 and inflammation by using RAW264.7 monocyte/macrophage cells. The expression of genes encoding inflammation-associated factors cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, IL-10, and transforming growth factor beta 1 (TGF-β1)) decreased after RAW264.7 cells were treated with anti-Angptl7 polyclonal antibody but increased after the cells were transfected with an Angptl7-expressing plasmid. Angptl7 overexpression enhanced phagocytosis and inhibited the proliferation of RAW264.7 cells. In addition, Angptl7 antagonized the anti-inflammatory effects of TGF-β1 and dexamethasone. Pathway analysis showed that Angptl7 promoted the phosphorylation of both p65 and p38, but only the P38 mitogen-activated protein kinase (MAPK) signaling pathway mediated Angptl7-associated inflammatory functions. Additionally, after 1 week of daily intraperitoneal injections of recombinant TNF-α in a mouse model of peripheral inflammation, Angptl7 expression increased in the mouse eyes. Thus, Angptl7 is a factor that promotes pro-inflammatory responses in macrophages through the P38 MAPK signaling pathway and represents a potential therapeutic target for treatment of inflammatory diseases.

Plasma and adipose tissue level of angiopoietin-like 7 (ANGPTL7) are increased in obesity and reduced after physical exercise

Objective

ANGPTL7 is a member of the Angiopoietin-like (ANGPTL) protein family that is composed of eight proteins (1–8). Increasing evidence is associating ANGPTL proteins to obesity and insulin resistance. The biological role of ANGPTL7 is yet to be understood except for a recently proposed role in the pathophysiology of glaucoma. This study was designed to shed light on the function of ANGPTL7 in obesity and its modulation by physical exercise as well as its potential association with lipid profile.

Methods

A total of 144 subjects were enrolled in this study and finished three months of physical exercise. The participants were classified based on their BMI, 82 subjects were non-obese and 62 obese. ANGPTL7 levels in plasma and adipose tissue were measured by ELISA, RT-PCR and immunohistochemistry.

Results

In this study, we showed that ANGPTL7 level was increased in the plasma of obese subjects (1249.05± 130.39 pg/mL) as compared to non-obese (930.34 ± 87.27 pg/mL) (p-Value = 0.032). ANGPTL7 Gene and protein expression levels in adipose tissue also showed over two fold increase. Physical exercise reduced circulating level of ANGPTL7 in the obese subjects to 740.98± 127.18 pg/mL, (p-Value = 0.007). ANGPTL7 expression in adipose tissue was also reduced after exercise. Finally, ANGPTL7 circulating level showed significant association with TG level in the obese subjects (R² = 0.183, p-Value = 0.03).

Conclusion

In conclusion, our data shows for the first time that obesity increases the level of ANGPTL7 in both plasma and adipose tissue. Increased expression of ANGPTL7 might play a minor role in the regulation of TG level in obese subjects either directly or through interaction with other ANGPTL protein members. Physical exercise reduced the level of ANGPTL7 highlighting the potential for targeting this protein as a therapeutic target for regulating dyslipidemia.

Plasma citrate concentration: a possible biomarker for glaucoma in children

OBJECTIVES

The main aim of the present study was to examine a possible role of plasma and urine citrate levels as glaucoma indicators in school-aged children with glaucoma diagnosis.

PATIENTS

34 school-aged children with a glaucoma diagnosis (mean age 15.69±1.86 years) were qualified for the study group and 34 patients with no ophthalmological ailments were qualified for the control group (mean age 16.1±1.98 years). Plasma and urine citrate levels in the study and the control group (Kruskal-Wallis test) were compared.

RESULTS

Plasma citrate levels in the study (16.33±4.51 mg/L) and the control group (19.11±3.66 mg/L) were different; the statistical significance (p=0.0036). Plasma citrate concentrations were significantly lower in the study group in comparison with the control group. There were no statistically important differences between the study group (291.12±259.13 mg/24 hours; 275.82±217.57 mg/g) and the control group (434.88±357.66 mg/24 hours; 329.81±383.27 mg/g) including urine citrate level (p=0.052) and urine citrate to creatine ratio (p=0.4667).

CONCLUSION

Plasma citrate concentration might be considered as glaucoma biomarker in paediatric population.

Angiopoietin-like 7 is an anti-angiogenic protein required to prevent vascularization of the cornea

Purpose

We sought to identify the anti-angiogenic molecule expressed in corneal keratocytes that is responsible for maintaining the avascularity of the cornea.

Methods

Human umbilical vein endothelial cells (HUVECs) were cultured with either human dermal fibroblasts or with human corneal keratocytes under serum-free conditions. The areas that exhibited blood vessel formation were estimated by immunostaining the cultures with an antitibody against CD31, a blood vessel marker. We also performed microarray gene-expression analysis and selected one molecule, angiopoietin-like 7 (ANGPTL7) for further functional studies conducted with the keratocytes and in vivo in mice.

Results

Areas showing blood vessel formation in normal serum-free medium were conditions were markedly smaller when HUVECs were co-cultured with corneal keratocytes than when they were co-cultured with the dermal fibroblasts under the same conditions. Microarray analysis revealed that ANGPTL7 expression was higher in keratocytes than in dermal fibroblasts. In vitro, inhibiting ANGPTL7 expression by using a specific siRNA led to greater tube formation than did the transfection of cells with a control siRNA, and this increase in tube formation was abolished when recombinant ANGPTL7 protein was added to the cultures. In vivo, intrastromal injections of an ANGPTL7 PshRNA into the avascular corneal stroma of mice resulted in the growth of blood vessels.

Conclusions

ANGPTL7, which is abundantly expressed in keratocytes, plays a major role in maintaining corneal avascularity and transparency.

Transforming Growth Factor Beta 3 Modifies Mechanics and Composition of Extracellular Matrix Deposited by Human Trabecular Meshwork Cells

Pseudoexfoliation syndrome is a systemic disorder of the extracellular matrix (ECM) with ocular manifestations in the form of chronic open angle glaucoma. Elevated levels of TGFβ3 in the aqueous humor of individuals with pseudoexfoliation glaucoma (PEX) have been reported. The influence of TGFβ3 on the biochemical composition and biomechanics of ECM of human trabecular meshwork (HTM) cells was investigated. HTM cells from eye bank donor eyes were isolated, plated on aminosilane functionalized glass substrates and cultured in the presence or absence of 1 ng/mL TGFβ3 for 4 weeks. After incubation, samples were decellularized and decellularization was verified by immunostaining. The mechanics of the remaining ECM that was deposited by the treated or the control cells were measured by atomic force microscopy (AFM). Imaged by AFM, the surface features of the ECM from both sets of samples had a similar roughness/topography (as determined by RMS values) suggesting surface features of the ECM were similar in both cases; however, the ECM from the HTM cells treated with TGFβ3 was between 3- and 5-fold stiffer than that produced by the control HTM cells. Proteins present in the ECM were solubilized and analyzed using liquid chromatography tandem mass spectroscopy (LC-MS/MS). Data indicate that multiple proteins previously reported to be altered in glaucoma were changed in the ECM as a result of the presence of TGFβ3, including inhibitors of the BMP and Wnt signaling pathways. Gremlin1and 4, SERPINE1 and 2, periostin, secreted frizzled related protein (SFRP) 1 and 4, and ANGPTL4 were among those proteins that were overexpressed in the ECM after TGFβ3 treatment.

Uromodulin retention in thick ascending limb of Henle's loop affects SCD1 in neighboring proximal tubule: renal transcriptome studies in mouse models of uromodulin-associated kidney disease

Uromodulin-associated kidney disease (UAKD) is a hereditary progressive renal disease which can lead to renal failure and requires renal replacement therapy. UAKD belongs to the endoplasmic reticulum storage diseases due to maturation defect of mutant uromodulin and its retention in the enlarged endoplasmic reticulum in the cells of the thick ascending limb of Henle's loop (TALH). Dysfunction of TALH represents the key pathogenic mechanism of UAKD causing the clinical symptoms of this disease. However, the molecular alterations underlying UAKD are not well understood. In this study, transcriptome profiling of whole kidneys of two mouse models of UAKD, Umod^A227T and Umod^C93F, was performed. Genes differentially abundant in UAKD affected kidneys of both Umod mutant lines at different disease stages were identified and verified by RT-qPCR. Additionally, differential protein abundances of SCD1 and ANGPTL7 were validated by immunohistochemistry and Western blot analysis. ANGPTL7 expression was down-regulated in TALH cells of Umod mutant mice which is the site of the mutant uromodulin maturation defect. SCD1 was expressed selectively in the S3 segment of proximal tubule cells, and SCD1 abundance was increased in UAKD affected kidneys. This finding demonstrates that a cross talk between two functionally distinct tubular segments of the kidney, the TALH segment and the S3 segment of proximal tubule, exists.

Angiopoietin-like 7, a novel pro-angiogenetic factor over-expressed in cancer

Angiopoietin-like (ANGPTL) proteins are secreted proteins showing structural similarity to members of the angiopoietin family. Some ANGPTL proteins possess pleiotropic activities, being involved in cancer lipid, glucose energy metabolisms, and angiogenesis. ANGPTL7 is the less characterized member of the family whose functional role is only marginally known. In this study, we provide experimental evidences that ANGPTL7 is over-expressed in different human cancers. To understand the role played by ANGPTL7 in tumor biology, we asked whether ANGPTL7 is endogenously expressed by malignant cells or in response to environmental stimuli. We found that ANGPTL7 is marginally expressed under standard growth condition while it is specifically up-regulated by hypoxia. Interestingly, the protein is secreted and partially associated with the exosomal fraction, suggesting that it could be found in the systemic circulation of oncologic patients and act in an endocrine way. Moreover, we found that ANGPTL7 exerts a pro-angiogenetic effect on human differentiated endothelial cells by stimulating their proliferation, motility, invasiveness, and capability to form capillary-like networks while it does not stimulate progenitor endothelial cells. Finally, we showed that ANGPTL7 promotes vascularization in vivo in the mouse Matrigel sponge assay, thereby accrediting this molecule as a pro-angiogenic factor.

Human trabecular meshwork cells exhibit several characteristics of, but are distinct from, adipose-derived mesenchymal stem cells

PURPOSE

To support the growing promise of regenerative medicine in glaucoma, we characterized the similarities and differences between human trabecular meshwork (HTM) cells and human mesenchymal stem cells (hMSCs).

METHODS

HTM cells and hMSCs were phenotypically characterized by flow cytometry. Using quantitative polymerase chain reaction, the expression of myoc, angptl7, sox2, pou5f1, and notch1 was determined in both cell types with and without dexamethasone (Dex). Immunosuppressive behavior of HTM cells and hMSCs was determined using T cells activated with phytohemagglutinin. T-cell proliferation was determined using BrdU incorporation and flow cytometry. Multipotency of HTM cells and hMSCs was determined using adipogenic and osteogenic differentiation media as well as aqueous humor (AH). Alpha-smooth muscle actin (αSMA) expression was determined in HTM cells, hMSCs, and HTM tissue.

RESULTS

Phenotypically, HTM and hMSCs expressed CD73, CD90, CD105, and CD146 but not CD31, CD34, and CD45 and similar sox2, pou5f1, and notch1 expression. Both cell types suppressed T-cell proliferation. However, HTM cells, but not hMSCs, upregulated myoc and angptl7 in response to Dex. Additionally, HTM cells did not differentiate into adipocytes or osteocytes. Culture of hMSCs in 20%, but not 100%, AH potently induced alkaline phosphatase activity. HTM cells in culture possessed uniformly strong expression of αSMA, which contrasted with the limited expression in hMSCs and spatially discrete expression in HTM tissue.

CONCLUSIONS

HTM cells possess a number of important similarities with hMSCs but lack multipotency, one of the defining characteristics of stem cells. Further work is needed to explore the molecular mechanisms and functional implications underlying the phenotypic similarities.

Biomarkers of primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a primary neuronal disease of the optic nerve without a definable cause, and is often associated with increased intraocular pressure. Worldwide, POAG is the second leading cause of blindness; there are 45 million people today with POAG and bilateral blindness is present in 4.5 million of these. In order to elucidate the possible etiologic factors in POAG, we have cataloged all known biomarkers in the aqueous humor, trabecular meshwork, optic nerve and blood into four categories, namely extracellular matrix (ECM), cell signaling molecules, aging/stress and immunity-related changes. We present a theoretical model to show possible signaling pathways of the ECM, cell signaling and innate immune response through activation of Toll-like receptor 4. Our article suggests that ECM and innate immune biomarkers are the lead candidates for developing the 'POAG biomarker signature'. We suggest that current research is critical to pinpoint the causes of the disease so that new treatment modalities can become available for better regulation of the intraocular pressure and neuroprotection of the optic nerve.

Angiopoietin-like proteins: a comprehensive look

Angiopoietin-like proteins (ANGPTLs) are a family of proteins structurally similar to the angiopoietins. To date, eight ANGPTLs have been discovered, namely ANGPTL1 to ANGPTL8. Emerging evidence implies a key role for ANGPTLs in the regulation of a plethora of physiological and pathophysiological processes. Most of the ANGPTLs exhibit multibiological properties, including established functional roles in lipid and glucose metabolism, inflammation, hematopoiesis, and cancer. This report represents a systematic and updated appraisal of this class of proteins, focusing on the main features of each ANGPTL.

New therapeutic targets for intraocular pressure lowering

Primary open-angle glaucoma (POAG) is a leading cause of irreversible and preventable blindness and ocular hypertension is the strongest known risk factor. With current classes of drugs, management of the disease focuses on lowering intraocular pressure (IOP). Despite of their use to modify the course of the disease, none of the current medications for POAG is able to reduce the IOP by more than 25%-30%. Also, some glaucoma patients show disease progression despite of the therapeutics. This paper examines the new described physiological targets for reducing the IOP. The main cause of elevated IOP in POAG is thought to be an increased outflow resistance via the pressure-dependent trabecular outflow system, so there is a crescent interest in increasing trabecular meshwork outflow by extracellular matrix remodeling and/or by modulation of contractility/TM cytoskeleton disruption. Modulation of new agents that act mainly on trabecular meshwork outflow may be the future hypotensive treatment for glaucoma patients. There are also other agents in which modulation may decrease aqueous humour production or increase uveoscleral outflow by different mechanisms from those drugs available for glaucoma treatment. Recently, a role for the ghrelin-GHSR system in the pathophysiology modulation of the anterior segment, particularly regarding glaucoma, has been proposed.

Biomarkers in primary open angle glaucoma

Glaucoma, a leading cause of blindness worldwide, is currently defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may lead to specific visual field defects over time. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP). Glaucoma can be divided roughly into two main categories, ‘ open angle ’ and ‘ closed angle ’ glaucoma.Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice loss of vision until the disease has progressed significantly. Primary open angle glaucoma(POAG) is described distinctly as a multifactorial optic neuropathy that is chronic and progressive with a characteristic acquired loss of optic nerve fibers. Such loss develops in the presence of open anterior chamber angles, characteristic visual field abnormalities, and IOP that is too high for the healthy eye. It manifests by cupping and atrophy of the optic disc, in the absence of other known causes of glaucomatous disease. Several biological markers have been implicated with the disease. The purpose of this study was to summarize the current knowledge regarding the non-genetic molecular markers which have been predicted to have an association with POAG but have not yet been validated.

Role of substratum stiffness in modulating genes associated with extracellular matrix and mechanotransducers YAP and TAZ

PURPOSE

Primary open-angle glaucoma is characterized by increased resistance to aqueous humor outflow and a stiffer human trabecular meshwork (HTM). Two Yorkie homologues, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif, encoded by WWTR1 (TAZ), are mechanotransducers of the extracellular-microenvironment and coactivators of transcription. Here, we explore how substratum stiffness modulates the YAP/TAZ pathway and extracellular matrix genes in HTM cells and how this may be play a role in the onset and progression of glaucoma.

METHODS

HTM cells from normal donors were cultured on hydrogels mimicking the stiffness of normal (5 kPa) and glaucomatous (75 kPa) HTM. Changes in expression of YAP/TAZ related genes and steroid responsiveness were determined. Additionally, transglutaminase-2 expression was determined after YAP silencing.

RESULTS

YAP and TAZ are both expressed in human trabecular meshwork cells. In vitro, YAP and TAZ were inversely regulated by substratum stiffness. YAP and 14-3-3σ were downregulated to different extents on stiffer substrates; TAZ, tissue transglutaminase (TGM2), and soluble frizzled-related protein-1 (sFRP-1) were significantly upregulated. CTGF expression appeared to be altered differentially by both YAP and TAZ. Myocilin and angiopoietin-like 7 expression in response to dexamethasone was more pronounced on stiffer substrates. We demonstrated a direct effect by YAP on TGM2 when YAP was silenced by small interfering RNA.

CONCLUSIONS

The expression of YAP/TAZ and ECM-related-genes is impacted on physiologically relevant substrates. YAP was upregulated in cells on softer substrates. Stiffer substrates resulted in upregulation of canonical Wnt modulators, TAZ and sFRP-1, and thus may influence the progression of glaucoma. These results demonstrate the importance of YAP/TAZ in the HTM and suggest their role in glaucoma.

Toward an integrative view of Optineurin functions

This review highlights recent advances in our understanding of the mechanisms of Optineurin (Optn) action and its implication in diseases. Optn has emerged as a key player regulating various physiological processes, including membrane trafficking, protein secretion, cell division and host defense against pathogens. Furthermore, there is growing evidence for an association of Optn mutations with human diseases such as primary open-angle glaucoma, amyotrophic lateral sclerosis and Paget's disease of bone. Optn functions depend on its precise subcellular localization and its interaction with other proteins. Here, we review the mechanisms that allow Optn to ensure a timely and spatially coordinated integration of different physiological processes and discuss how their deregulation may lead to different pathologies.

Fibroblasts from phenotypically normal palmar fascia exhibit molecular profiles highly similar to fibroblasts from active disease in Dupuytren's Contracture

BACKGROUND

Dupuytren's contracture (DC) is a fibroproliferative disorder characterized by the progressive development of a scar-like collagen-rich cord that affects the palmar fascia of the hand and leads to digital flexion contractures. DC is most commonly treated by surgical resection of the diseased tissue, but has a high reported recurrence rate ranging from 27% to 80%. We sought to determine if the transcriptomic profiles of fibroblasts derived from DC-affected palmar fascia, adjacent phenotypically normal palmar fascia, and non-DC palmar fascial tissues might provide mechanistic clues to understanding the puzzle of disease predisposition and recurrence in DC.

METHODS

To achieve this, total RNA was obtained from fibroblasts derived from primary DC-affected palmar fascia, patient-matched unaffected palmar fascia, and palmar fascia from non-DC patients undergoing carpal tunnel release (6 patients in each group). These cells were grown on a type-1 collagen substrate (to better mimic their in vivo environments). Microarray analyses were subsequently performed using Illumina BeadChip arrays to compare the transcriptomic profiles of these three cell populations. Data were analyzed using Significance Analysis of Microarrays (SAM v3.02), hierarchical clustering, concordance mapping and Venn diagram.

RESULTS

We found that the transcriptomic profiles of DC-disease fibroblasts and fibroblasts from unaffected fascia of DC patients exhibited a much greater overlap than fibroblasts derived from the palmar fascia of patients undergoing carpal tunnel release. Quantitative real time RT-PCR confirmed the differential expression of select genes validating the microarray data analyses. These data are consistent with the hypothesis that predisposition and recurrence in DC may stem, at least in part, from intrinsic similarities in the basal gene expression of diseased and phenotypically unaffected palmar fascia fibroblasts. These data also demonstrate that a collagen-rich environment differentially alters gene expression in these cells. In addition, Ingenuity pathway analysis of the specific biological pathways that differentiate DC-derived cells from carpal tunnel-derived cells has identified the potential involvement of microRNAs in this fibroproliferative disorder.

CONCLUSIONS

These data show that the transcriptomic profiles of DC-disease fibroblasts and fibroblasts from unaffected palmar fascia in DC patients are highly similar, and differ significantly from the transcriptomic profiles of fibroblasts from the palmar fascia of patients undergoing carpal tunnel release.

Myosin VI and its binding partner optineurin are involved in secretory vesicle fusion at the plasma membrane

During constitutive secretion, proteins synthesized at the endoplasmic reticulum (ER) are transported to the Golgi complex for processing and then to the plasma membrane for incorporation or extracellular release. This study uses a unique live-cell constitutive secretion assay to establish roles for the molecular motor myosin VI and its binding partner optineurin in discrete stages of secretion. Small interfering RNA-based knockdown of myosin VI causes an ER-to-Golgi transport delay, suggesting an unexpected function for myosin VI in the early secretory pathway. Depletion of myosin VI or optineurin does not affect the number of vesicles leaving the trans-Golgi network (TGN), indicating that these proteins do not function in TGN vesicle formation. However, myosin VI and optineurin colocalize with secretory vesicles at the plasma membrane. Furthermore, live-cell total internal reflection fluorescence microscopy demonstrates that myosin VI or optineurin depletion reduces the total number of vesicle fusion events at the plasma membrane and increases both the proportion of incomplete fusion events and the number of docked vesicles in this region. These results suggest a novel role for myosin VI and optineurin in regulation of fusion pores formed between secretory vesicles and the plasma membrane during the final stages of secretion.

Evidence for a role of angiopoietin-like 7 (ANGPTL7) in extracellular matrix formation of the human trabecular meshwork: implications for glaucoma

The trabecular meshwork tissue controls the drainage of the aqueous humor of the eye. A dysfunctional trabecular meshwork leads to an altered fluid resistance, which results in increased intraocular pressure (IOP). IOP is the major risk factor of glaucoma, the second-leading cause of blindness in the developed world. In the search for genes altered by glaucomatous insults, we identified angiopoietin-like7 (ANGPTL7), a member of the ANGPTL family. Although structurally related to the angiopoietins, ANGPTL7's function is poorly understood. Because ANGPTL7 is secreted and because extracellular matrix (ECM) deposition and organization is critical for aqueous humor resistance, we investigated the effect of ANGPTL7 on relevant trabecular meshwork ECM genes and proteins. We find that overexpression of ANGPTL7 in primary human trabecular meshwork cells altered the expression of fibronectin, collagens type I, IV & V, myocilin, versican, and MMP1. ANGPTL7 also interfered with the fibrillar assembly of fibronectin. Finally, we find that silencing ANGPTL7 during the glucocorticoid insult significantly affected the expression of other steroid-responsive proteins. These results indicate that ANGPTL7 modulates the trabecular meshwork's ECM as well as the response of this tissue to steroids. Together with previous findings, these properties strengthen ANGPTL7's candidacy for the regulation of IOP and glaucoma.

Vascular gene expression in mice overexpressing human endothelin-1 targeted to the endothelium

Endothelin (ET)-1 plays an important pathophysiological role in several vascular diseases including hypertension and atherosclerosis. Transgenic mice overexpressing human preproET-1 selectively in the endothelium (eET-1) exhibit vascular injury in the absence of blood pressure elevation. ET-1 overexpression may induce vascular injury by inducing changes in gene expression. To understand mechanisms whereby ET-1 induces vascular damage, vascular gene expression profiling was performed using DNA microarrays. RNA from mesenteric arteries of male and female young (6-7 wk) and mature (6-8 mo) eET-1 and wild-type (WT) mice was isolated, and changes in gene expression were determined by genome-wide expression profiling using Illumina microarray and FlexArray software. Data were analyzed using a relaxed and a stringent statistical approach. The gene lists were compared and analyzed as well with Ingenuity Pathway Analysis. The most common change was an increase in the expression of lipid metabolism genes. Four of these genes were validated by qPCR, cyp51, dgat2, and scd1 genes in young and elovl6 in both young and mature male mice, supporting a role of ET-1 in atherosclerosis. To test the hypothesis that ET-1 participates in mechanisms leading to atherosclerosis, we crossed eET-1 with atherosclerosis-prone apoE(-/-) mice to determine whether ET-1 overexpression exacerbates high-fat diet (HFD)-induced atherosclerosis using oil red O staining of descending thoracic aorta. HFD increased lipid plaques by 3-, 27-, and 86-fold in eET-1, apoE(-/-), and crossed mice, respectively, vs. WT. This suggests that increased endothelial ET-1 expression results in early changes in gene expression in the vascular wall that enhance lipid biosynthesis and accelerate progression of atherosclerosis.

Ontogeny of angiopoietin-like protein 1, 2, 3, 4, 5, and 7 genes during chick embryonic development

Angiopoietin-like proteins (ANGPTLs) are secreted proteins possessing an amino-terminal coiled-coil domain and a carboxyl-terminal fibrinogen-like domain and are known as angiogenic factors. Several members of ANGPTLs also regulate lipid metabolism independently of angiogenic effects, but most of their functions during vertebrate development are not demonstrated. To ascertain their developmental functions, we examined the expression patterns of Angptl1, 2, 3, 4, 5, and 7 orthologues during chick development using whole-mount in situ hybridization. Angptl1 was first detected at embryonic day 3 (E3) in the somite. At E4, Angptl1 was expressed in somite-derivatives and limb mesenchyme. Angptl2 was first detected at E3 in the hindbrain. At E4, Angptl2 was expressed in neuroepithelium of forebrain and hindbrain and partly in the heart. Angptl3 was first detected at E3 and continued to be expressed in the liver and yolk sac at E4. Angptl4 was first detected at E3 in the somites and liver. At E4, Angptl4 was also observed in the heart. Angptl5 was not detected in these developmental stages. Angptl7 was first detected at E3 in the ectoderm overlying the lenses of the eyes. At E4, Angptl7 was specifically expressed in cornea. These data suggest that each member of the ANGPTL family could be related to angiogenesis during various organogeneses of the developing chick embryo.

The role of steroids in outflow resistance

Glucocorticoid (GC)-induced ocular hypertension and secondary iatrogenic open-angle glaucoma are serious side effects of GC therapy. Its clinical presentation is similar in many ways to primary open-angle glaucoma, including increased aqueous outflow resistance and morphological and biochemical changes to the trabecular meshwork (TM). Therefore, a large number of studies have examined the effects of GCs on TM cells and tissues. GCs have diverse effects on the TM, altering TM cell functions, gene expression, extracellular matrix metabolism, and cytoskeletal structure. Some or all of these effects may be responsible for the increased outflow resistance associated with GC therapy. In contrast to GCs, several different classes of steroids appear to lower IOP. Additional research will help better define the molecular mechanisms responsible for GC-induced ocular hypertension and steroid-induced IOP lowering activity.