Angiopoietins in angiogenesis. Cancer Lett. 2013;328:18-26. [PMID: 22922303 DOI: 10.1016/j.canlet.2012.08.018]

Glipizide suppresses prostate cancer progression in the TRAMP model by inhibiting angiogenesis

Drug repurposing of non-cancer drugs represents an attractive approach to develop new cancer therapy. Using the TRAMP transgenic mouse model, glipizide, a widely used drug for type 2 diabetes mellitus, has been identified to suppress prostate cancer (PC) growth and metastasis. Angiogenesis is intimately associated with various human cancer developments. Intriguingly, glipizide significantly reduces microvessel density in PC tumor tissues, while not inhibiting prostate cancer cell proliferation from the MTT assay and flow cytometry investigation. Moreover, glipizide inhibits the tubular structure formation of human umbilical vein endothelial cells by regulating the HMGIY/Angiopoietin-1 signaling pathway. Taken together, these results demonstrate that glipizide has the potential to be repurposed as an effective therapeutic for the treatment of PC by targeting tumor-induced angiogenesis.

Selenium Induces an Anti-tumor Effect Via Inhibiting Intratumoral Angiogenesis in a Mouse Model of Transplanted Canine Mammary Tumor Cells

Selenium (Se) has been widely reported to possess anti-tumor effects. Angiogenesis is the formation of new blood vessels and is required to supply oxygen, nutrients, and growth factors for tumor growth, progression, and metastasis. To explore whether the anti-tumor effect of Se was associated with angiogenesis in vivo, we studied the effects of sodium selenite (Sel) and methylseleninic acid (MSA) on tumors induced by canine mammary tumor cells (CMT1211) in mice; cyclophosphamide (CTX) served as a positive control. The results showed that the Se content was significantly increased in the Sel and MSA groups. Se significantly inhibited the tumor weights and volumes. Large necrotic areas and scattered and abnormal small necrotic areas were observed in the Se treatment group. Immunofluorescence double staining showed a reduction in the microvessel density (MVD) and increment in the vessel maturation index (VMI) compared with the untreated control group. As expected, the protein and mRNA levels of the angiogenesis factors angiopoietin-2 (Ang-2), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) were decreased in the Se-treated tumors by IHC, as shown by western blotting and RT-QPCR. We also found that organic Se MSA provided stronger inhibition of tumor growth compared with inorganic sodium selenite (Sel). Altogether, our results indicated that Se exerted anti-tumor effects in vivo at least partially by inhibiting angiogenic factors.

FGFR inhibitors: Effects on cancer cells, tumor microenvironment and whole-body homeostasis (Review)

Fibroblast growth factor (FGF)2, FGF4, FGF7 and FGF20 are representative paracrine FGFs binding to heparan-sulfate proteoglycan and fibroblast growth factor receptors (FGFRs), whereas FGF19, FGF21 and FGF23 are endocrine FGFs binding to Klotho and FGFRs. FGFR1 is relatively frequently amplified and overexpressed in breast and lung cancer, and FGFR2 in gastric cancer. BCR-FGFR1, CNTRL-FGFR1, CUX1-FGFR1, FGFR1OP-FGFR1, MYO18A-FGFR1 and ZMYM2-FGFR1 fusions in myeloproliferative neoplasms are non-receptor-type FGFR kinases, whereas FGFR1-TACC1, FGFR2-AFF3, FGFR2-BICC1, FGFR2-PPHLN1, FGFR3-BAIAP2L1 and FGFR3-TACC3 fusions in solid tumors are transmembrane-type FGFRs with C-terminal alterations. AZD4547, BGJ398 (infigratinib), Debio-1347 and dovitinib are FGFR1/2/3 inhibitors; BLU9931 is a selective FGFR4 inhibitor; FIIN-2, JNJ-42756493, LY2874455 and ponatinib are pan-FGFR inhibitors. AZD4547, dovitinib and ponatinib are multi-kinase inhibitors targeting FGFRs, colony stimulating factor 1 receptor (CSF1R), vascular endothelial growth factor (VEGF)R2, and others. The tumor microenvironment consists of cancer cells and stromal/immune cells, such as cancer-associated fibroblasts (CAFs), endothelial cells, M2-type tumor-associating macrophages (M2-TAMs), myeloid-derived suppressor cells (MDSCs) and regulatory T cells. FGFR inhibitors elicit antitumor effects directly on cancer cells, as well as indirectly through the blockade of paracrine signaling. The dual inhibition of FGF and CSF1 or VEGF signaling is expected to enhance the antitumor effects through the targeting of immune evasion and angiogenesis in the tumor microenvironment. Combination therapy using tyrosine kinase inhibitors (FGFR or CSF1R inhibitors) and immune checkpoint blockers (anti-PD-1 or anti-CTLA-4 monoclonal antibodies) may be a promising choice for cancer patients. The inhibition of FGF19-FGFR4 signaling is associated with a risk of liver toxicity, whereas the activation of FGF23-FGFR4 signaling is associated with a risk of heart toxicity. Endocrine FGF signaling affects the pathophysiology of cancer patients who are prescribed FGFR inhibitors. Whole-genome sequencing is necessary for the detection of promoter/enhancer alterations of FGFR genes and rare alterations of other genes causing FGFR overexpression. To sustain the health care system in an aging society, a benefit-cost analysis should be performed with a focus on disease-free survival and the total medical cost before implementing genome-based precision medicine for cancer patients.

Effects of prolonged ingestion of epigallocatechin gallate on diabetes type 1-induced vascular modifications in the erectile tissue of rats

Diabetes Mellitus type 1 is a metabolic disease that predisposes to erectile dysfunction, partly owing to structural and molecular changes in the corpus cavernosum (CC) vessels. The aim of this study was to determine the effects of early treatment with the antioxidant epigallocatechin gallate (EGCG) in cavernous diabetes-induced vascular modifications. Diabetes was induced in two groups of young Wistar rats; one group was treated with EGCG for 10 weeks. A reduction in smooth muscle content was observed in the CC of diabetic rats, which was significantly attenuated with EGCG consumption. No differences were observed among groups, neither in the expression of VEGF assayed by western blotting nor in the immunofluorescent labeling of vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2). VEGFR2 was restricted to the endothelium, whereas VEGF and VEGFR1 co-localized in the smooth muscle layer. With regard to the Angiopoietin/Tie-2 system, no quantitative differences in Angiopoietin 1 were observed among the experimental groups. Ang1 localization was restricted to the smooth muscle layer, and receptor Tie2 and Angiopoietin 2 were both expressed in the endothelium. In brief, our results suggest that EGCG consumption prevented diabetes-induced loss of cavernous smooth muscle but does not affect vascular growth factor expression in young rats.

Cartilage oligomeric matrix protein enhances the vascularization of acellular nerves

Vascularization of acellular nerves has been shown to contribute to nerve bridging. In this study, we used a 10-mm sciatic nerve defect model in rats to determine whether cartilage oligomeric matrix protein enhances the vascularization of injured acellular nerves. The rat nerve defects were treated with acellular nerve grafting (control group) alone or acellular nerve grafting combined with intraperitoneal injection of cartilage oligomeric matrix protein (experimental group). As shown through two-dimensional imaging, the vessels began to invade into the acellular nerve graft from both anastomotic ends at day 7 post-operation, and gradually covered the entire graft at day 21. The vascular density, vascular area, and the velocity of revascularization in the experimental group were all higher than those in the control group. These results indicate that cartilage oligomeric matrix protein enhances the vascularization of acellular nerves.

Association of Angiopoietin-2 and Ki-67 Expression with Vascular Density and Sunitinib Response in Metastatic Renal Cell Carcinoma

The Angiopoietin-2 (Ang2, Angpt2) growth factor is a context-dependent antagonist/agonist ligand of the endothelial Tie2 receptor tyrosine kinase and known to promote tumour angiogenesis and metastasis. Angiopoietin antagonists have been tested in clinical cancer trials in combination with VEGF-based anti-angiogenic therapy, including sunitinib, which is widely used as a first-line therapy for metastatic renal cell carcinoma (mRCC). However, little is known about Ang2 protein expression in human tumours and the correlation of tumour Ang2 expression with tumour vascularization, tumour cell proliferation and response to anti-angiogenic therapies. Here, we evaluated, using immunohistochemistry, the expression of Ang2, CD31 and the cell proliferation marker Ki-67 in the primary kidney cancer from 136 mRCC patients, who received first-line sunitinib after nephrectomy. Ang2 protein expression was restrained to RCC tumour vessels, and correlated with tumour vascularization and response to sunitinib. High pre-therapeutic Ang2 expression, and more strongly, combined high expression of both Ang2 and CD31, were associated with a high clinical benefit rate (CBR). Low cancer Ki-67 expression, but not Ang2 or CD31 expression, was associated with favourable progression-free (PFS) and overall survival (OS) as compared to patients with high Ki-67 expression (PFS 6.5 vs. 10.6 months, P = 0.009; OS, 15.7 vs. 28.5 months, P = 0.015). In summary, in this study to investigate endothelial Ang2 in mRCC patients treated with first-line sunitinib, high cancer Ang2 expression was associated with the CBR, but not PFS or OS, whereas low Ki-67 expression was significantly associated with long PFS and OS.

Computational Identification of Key Regulators in Two Different Colorectal Cancer Cell Lines

Transcription factors (TFs) are gene regulatory proteins that are essential for an effective regulation of the transcriptional machinery. Today, it is known that their expression plays an important role in several types of cancer. Computational identification of key players in specific cancer cell lines is still an open challenge in cancer research. In this study, we present a systematic approach which combines colorectal cancer (CRC) cell lines, namely 1638N-T1 and CMT-93, and well-established computational methods in order to compare these cell lines on the level of transcriptional regulation as well as on a pathway level, i.e., the cancer cell-intrinsic pathway repertoire. For this purpose, we firstly applied the Trinity platform to detect signature genes, and then applied analyses of the geneXplain platform to these for detection of upstream transcriptional regulators and their regulatory networks. We created a CRC-specific position weight matrix (PWM) library based on the TRANSFAC database (release 2014.1) to minimize the rate of false predictions in the promoter analyses. Using our proposed workflow, we specifically focused on revealing the similarities and differences in transcriptional regulation between the two CRC cell lines, and report a number of well-known, cancer-associated TFs with significantly enriched binding sites in the promoter regions of the signature genes. We show that, although the signature genes of both cell lines show no overlap, they may still be regulated by common TFs in CRC. Based on our findings, we suggest that canonical Wnt signaling is activated in 1638N-T1, but inhibited in CMT-93 through cross-talks of Wnt signaling with the VDR signaling pathway and/or LXR-related pathways. Furthermore, our findings provide indication of several master regulators being present such as MLK3 and Mapk1 (ERK2) which might be important in cell proliferation, migration, and invasion of 1638N-T1 and CMT-93, respectively. Taken together, we provide new insights into the invasive potential of these cell lines, which can be used for development of effective cancer therapy.

Novel anti-angiogenic therapeutic strategies in colorectal cancer

INTRODUCTION

Anti-angiogenetic agents are currently the standard of care in metastatic CRC patients. Bevacizumab, aflibercept, regorafenib and recently ramucirumab have significantly improved both progression-free and overall survival in different lines of treatment. Since bevacizumab's approval, a number of novel anti-VEGF agents have been tested in preclinical and clinical models.

AREAS COVERED

This review is focused on the most recent clinical results of novel agents targeting VEGF and its receptors with a major focus on those investigated recently in clinical trials.

EXPERT OPINION

In the last 15 years, a number of new anti-angiogenetic agents have been tested. Unfortunately, most of them have demonstrated unacceptable toxicities or failed to show activity. When tested as single agents, encouraging preliminary results were reported with fruquintinib, famitinib, and nintedanib. Interesting novel mechanisms of action are also being explored: VGX-100 is a monoclonal antibody (mAb) which binds to VEGF-C, inhibiting activation of VEGFR-2 and VEGFR-3 when combined with bevacizumab; tanibirumab is a mAb which binds to VEGFR-2 and vanucizumab is a bispecific mAb binding both to VEGF-A and Angiopoietin-2. Data about the combination of these agents with chemotherapy are very encouraging, even though preliminary. However, the definition of specific predictive biomarkers remains a priority.

Elevated Serum Level of Angiopoietin-2 as a Potential Marker for Poor Prognosis in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is a fast-growing cancer with poor prognosis. Patients with extensive-stage SCLC are generally treated with chemotherapy. Thus, it is essential to identify a predictor of efficacy and prognosis for SCLC. Angiopoietin-2 promotes vascular remodeling and angiogenesis. Increasing evidence reveals that angiopoietin-2 is preferentially expressed in cancer cells, and elevated angiopoietin-2 expression is related to invasive and metastatic phenotypes in various cancers. However, serum angiopoietin-2 level and its prognostic potential in SCLC have not been investigated. The aim of this study was to determine the usefulness of angiopoietin-2 level as a predictor of efficacy and prognosis for SCLC. This study consisted of sixty patients with SCLC. Each patient received four cycles of cisplatin-etoposide chemotherapy, and was followed for 36 months. Serum angiopoietin-2 levels were measured by Enzyme-linked immunosorbent assays. The angiopoietin-2 levels were significantly higher in SCLC patients than those in healthy subjects (P < 0.001). The patients were divided into high-level group (32 patients, 2,923.9 ± 294.7 pg/ml) and low-level group (28 patients, 1,789.5 ± 355.1 pg/ml) according to the mean value of the angiopoietin-2 level (2,400 pg/ml). Compared with the patients in the high-level group, the patients in the low-level group showed remarkably survival advantage (P = 0.002). During chemotherapy, the patients in the low-level group showed better treatment response than the patients in the high-level group (P < 0.05). Therefore, angiopoietin-2 might be useful as a prognostic factor for SCLC and for predicting SCLC response to chemotherapy.

Adipose-derived stem cell differentiation as a basic tool for vascularized adipose tissue engineering

The development of in vitro adipose tissue constructs is highly desired to cope with the increased demand for substitutes to replace damaged soft tissue after high graded burns, deformities or tumor removal. To achieve clinically relevant dimensions, vascularization of soft tissue constructs becomes inevitable but still poses a challenge. Adipose-derived stem cells (ASCs) represent a promising cell source for the setup of vascularized fatty tissue constructs as they can be differentiated into adipocytes and endothelial cells in vitro and are thereby available in sufficiently high cell numbers. This review summarizes the currently known characteristics of ASCs and achievements in adipogenic and endothelial differentiation in vitro. Further, the interdependency of adipogenesis and angiogenesis based on the crosstalk of endothelial cells, stem cells and adipocytes is addressed at the molecular level. Finally, achievements and limitations of current co-culture conditions for the construction of vascularized adipose tissue are evaluated.

Angiopoietins in the bone marrow microenvironment of acute lymphoblastic leukemia

OBJECTIVE

Angiogenesis have implications in leukemia biology. Angiopoietin 1 (Ang 1) is an angiogenic cytokine which is essential in survival and proliferation of endothelial cells. Angiopoietin 2 (Ang 2) promotes dissociation of pericytes and increases vascular permeability and stromal derived factor 1 alpha (SDF 1α) which is a key player in stem cell traffic in the bone marrow (BM), has stimulating effects on angiogenesis as well. Here, we investigated the role of the leukemic BM microenvironment and specifically, the role of SDF 1α-CXCR4 and Ang 1/Ang 2-Tie 2 axes.

METHODS

Here, Ang 1, Ang 2, and SDF 1α levels were measured in the BM plasma and in supernatants of mesenchymal stem/stromal cells (MSCs) of patients with ALL and compared with those of healthy controls.

RESULTS

The results showed that at diagnosis, BM plasma levels of Ang 1 and SDF 1α were significantly low and Ang 2 was high when compared to control values. Remission induction was associated with an increase in Ang 1/Ang 2 ratio and SDF levels in BM plasma.

DISCUSSION

The results suggest that BM microenvironment and leukemic cell-stroma interaction influences the secretion of Ang 1, 2 and SDF 1α, thus, may affect both angiogenesis, homing and mobilization of leukemic blasts.

Pro-apoptotic and anti-angiogenic properties of the α /β-thujone fraction from Thuja occidentalis on glioblastoma cells

The most aggressive type of brain tumor is glioblastoma multiforme, which to date remains incurable. Thuja occidentalis is used in homeopathy for the treatment of cancer, however, its mechanism of action remains unknown. We set out to study the effects of thujone fractions of Thuja on glioblastoma using in vitro and in vivo models. We found that the α/ β-thujone fraction decrease the cell viability and exhibit a potent anti-proliferative, pro-apoptotic and anti-angiogenic effects in vitro. In vivo assays showed that α /β-thujone promotes the regression of neoplasia and inhibits the angiogenic markers VEGF, Ang-4 and CD31 into the tumor.

Significance and therapeutic implications of endothelial progenitor cells in angiogenic-mediated tumour metastasis

Cancer conveys profound social and economic consequences throughout the world. Metastasis is responsible for approximately 90% of cancer-associated mortality and, when it occurs, cancer becomes almost incurable. During metastatic dissemination, cancer cells pass through a series of complex steps including the establishment of tumour-associated angiogenesis. The human endothelial progenitor cells (hEPCs) are a cell population derived from the bone marrow which are required for endothelial tubulogenesis and neovascularization. They also express abundant inflammatory cytokines and paracrine angiogenic factors. Clinically hEPCs are highly correlated with relapse, disease progression, metastasis and treatment response in malignancies such as breast cancer, ovarian cancer and non-small-cell lung carcinoma. It has become evident that the hEPCs are involved in the angiogenesis-required progression and metastasis of tumours. However, it is not clear in what way the signalling pathways, controlling the normal cellular function of human BM-derived EPCs, are hijacked by aggressive tumour cells to facilitate tumour metastasis. In addition, the actual roles of hEPCs in tumour angiogenesis-mediated metastasis are not well characterised. In this paper we reviewed the clinical relevance of the hEPCs with cancer diagnosis, progression and prognosis. We further summarised the effects of tumour microenvironment on the hEPCs and underlying mechanisms. We also hypothesized the roles of altered hEPCs in tumour angiogenesis and metastasis. We hope this review may enhance our understanding of the interaction between hEPCs and tumour cells thus aiding the development of cellular-targeted anti-tumour therapies.

Negative pressure wound therapy promotes vessel destabilization and maturation at various stages of wound healing and thus influences wound prognosis

Negative pressure wound therapy (NPWT) has been observed to accelerate the wound healing process in humans through promoting angiogenesis. However, the potential biological effect and relevant molecular mechanisms, including microvessel destabilization, regression and endothelial cell proliferation in the early stage (1–3 days), and the neovascular stabilization and maturation in the later stage (7–15 days), have yet to be fully elucidated. The current study aimed to research the potential effect of NPWT on angiogenesis and vessel maturation, and investigate relevant association between mature microvessels and wound prognosis, as well as the regulatory mechanisms in human wound healing. Patients in the present study (n=48) were treated with NPWT or a petrolatum gauze, and relevant growth factors and vessel changes were detected using various experimental methods. NPWT increased the expression levels of angiogenin-2 (Ang-2), and decreased the expression levels of Ang-1 and ratios of Ang-1/Ang-2 in the initial stages of wound healing. However, in the latter stages of wound healing, NPWT increased the expression levels of Ang-1 and ratios of Ang-1/Ang-2, as well as the phosphorylation level of tyrosine kinase receptor-2. Consequently, microvessel pericyte coverage was gradually elevated, and the basement membrane was gradually supplied with new blood at the later stage of wound healing. In conclusion, NPWT may preferentially stimulate microvessel destabilization and regression in the early stage of wound healing, and as a consequence, increase angiogenesis. Subsequently, in the later stage of wound healing, NPWT may preferentially promote microvessel stabilization, thereby promoting microvessel maturation in human wounds through the angiogenin/tyrosine kinase receptor-2 signaling pathway. The results of the present study results demonstrated that NPWT was able to accelerate wound healing speed, and thus influence wound prognosis, as a result of an abundance of mature microvessels in human wounds.

The Mechanism of Ligamentum Flavum Hypertrophy: Introducing Angiogenesis as a Critical Link That Couples Mechanical Stress and Hypertrophy

BACKGROUND

Biochemical alterations associated with mechanical stress have been explored as an initiating step in the pathological progression of ligamentum flavum hypertrophy (LFH); however, this mechanism remains poorly understood. Recently, the inflammation induced after mechanical stress and the subsequent response of ligamentum flavum (LF) cells have been implicated in LFH pathology.

OBJECTIVE

To investigate the hypothesis that angiogenesis may be a critical link between hypertrophy and a series of stimulating events, including mechanical stress.

METHODS

LF from 20 lumbar spinal canal stenosis (LSCS) patients and 16 non-LSCS patients (control group) were collected during surgery. Patient demographic and radiographic data were obtained. The levels of angiogenic factors (vascular endothelial growth factor [VEGF], angiopoietin-1, vascular cell adhesion molecule, and basic fibroblast growth factor) in the LF were investigated by using an enzyme-linked immunosorbent assay. Angiogenesis was also quantified by immunohistochemical detection of CD34-positive capillaries. The correlations among clinical factors, including radiographic factors, angiogenic factors, and angiogenesis, were statistically analyzed.

RESULTS

The LSCS group was older and exhibited a longer symptom duration, wider segmental motion, and thicker LF than the control group. The LSCS group showed significantly higher tissue concentrations of VEGF (P < .001) that positively correlated with LF thickness (r = 0.557, P < .001) and segmental motion (r = 0.586, P < .001). The LSCS group showed significantly more CD34-positive capillaries than the control group (P = .004).

CONCLUSION

The LSCS group showed greater segmental motion, higher VEGF concentrations, and more CD34-positive capillaries than the control group. These data indicate that VEGF-mediated angiogenesis following mechanical stress may be a critical step within the series of pathological events in LFH.

Tissue engineering strategies for promoting vascularized bone regeneration

This review focuses on current tissue engineering strategies for promoting vascularized bone regeneration. We review the role of angiogenic growth factors in promoting vascularized bone regeneration and discuss the different therapeutic strategies for controlled/sustained growth factor delivery. Next, we address the therapeutic uses of stem cells in vascularized bone regeneration. Specifically, this review addresses the concept of co-culture using osteogenic and vasculogenic stem cells, and how adipose derived stem cells compare to bone marrow derived mesenchymal stem cells in the promotion of angiogenesis. We conclude this review with a discussion of a novel approach to bone regeneration through a cartilage intermediate, and discuss why it has the potential to be more effective than traditional bone grafting methods.

Delayed vasculogenesis and impaired angiogenesis due to altered Ang-2 and VE-cadherin levels in the chick embryo model following exposure to cadmium

PURPOSE

Cadmium (Cd) causes chick embryo malformation and abnormal extra-embryonic vasculature. This study investigates the effect of Cd on vasculogenesis, quantifies extra-embryonic vascular development following exposure to cadmium acetate (CdAc).

METHODS

After 48 or 60 h incubation, chicks were explanted and treated with 50 µl of 50 µM CdAc or equimolar sodium acetate. Embryos were again incubated then re-examined 4, 8, 24 and 48 h later. Gross morphological and histological manifestations were noted. Vasculogenesis was assessed by the development of omphalomesenteric vessels from blood islands. Sinus terminalis (ST), area vasculosa (AV), vessel density and embryo crown-rump length (CRL) were measured. Ang-2 and VE-cadherin mRNA expression was analysed by RT-PCR.

RESULTS

Vasculogenesis was delayed on gross and histological examination. ST length, AV area, vessel density and CRL were significantly reduced in the Cd group. Ang-2 was increased 4 h after exposure to Cd, whereas VE-cadherin was reduced.

CONCLUSION

Cd exposure inhibits normal development of extra-embryonic vasculature in line with growth retardation of the chick embryo in association with altered expression of Ang-2 and VE-cadherin.

Prorenin stimulates a pro-angiogenic and pro-inflammatory response in retinal endothelial cells and an M1 phenotype in retinal microglia

Angiogenesis and inflammation are causative factors in the development of neovascular retinopathies. These processes involve the retinal endothelium and the retinal immune cells, microglia. The renin-angiotensin system contributes to retinal injury via the actions of the type 1 angiotensin receptor (AT1R). However, it has been suggested that prorenin, the initiator of the renin-angiotensin system cascade, influences retinal injury independently from the AT1R. We evaluated whether prorenin induced a pro-angiogenic and pro-inflammatory response in retinal endothelial cells and a pro-inflammatory phenotype in retinal microglia. Primary cultures of retinal endothelial cells and microglia were studied. Rat recombinant prorenin (2 nmol/L) stimulated the proliferation and tubulogenesis of retinal endothelial cells; it increased the levels of pro-angiogenic factors, vascular endothelial growth factor, angiopoietin-1, and tyrosine kinase with immunoglobulin and epidermal growth factor homology domains, and pro-inflammatory factors, intercellular adhesion molecule-1 and monocyte chemoattractant protein-1, relative to the controls. The messenger RNA levels of the (pro)renin receptor were also increased. These effects occurred in the presence of the AT1R blocker candesartan (10 μmol/L) and the renin inhibitor aliskiren (10 μmol/L). Microglia, which express the (pro)renin receptor, elicited an activated phenotype when exposed to prorenin, which was characterized by increased levels of intercellular adhesion molecule-1, monocyte chemoattractant protein-1, tumour necrosis factor-α, interleukin-6, and interleukin-1β and by decreased levels of interleukin-10 and arginase-1 relative to controls. Candesartan did not influence the effects of prorenin on retinal microglia. In conclusion, prorenin has distinct pro-angiogenic and pro-inflammatory effects on retinal cells that are independent of the AT1R, indicating the potential importance of prorenin in retinopathy.

Angiogenesis- and Hypoxia-Associated Proteins as Early Indicators of the Outcome in Patients with Metastatic Breast Cancer Given First-Line Bevacizumab-Based Therapy

PURPOSE

We examined whether pretreatment levels of angiogenesis- or hypoxia-related proteins and their changes after one cycle of first-line bevacizumab-based therapy were associated with response, PFS, or OS in patients with metastatic breast cancer.

EXPERIMENTAL DESIGN

We included 181 patients enrolled in the phase II ATX trial evaluating first-line paclitaxel and bevacizumab without or with capecitabine (NTR1348). Plasma samples were analyzed for VEGF-A, soluble VEGFR2 (sVEGFR2), angiopoietin 2 (ANG2), soluble TIE2 (sTIE2), IL6, IL8, and carbonic anhydrase 9 (CA9). Baseline serum CA15-3 was documented. HR was adjusted for confounding factors. Where appropriate, an optimal cut-off value defining a high and a low group was determined with Martingale residuals.

RESULTS

At baseline, multiple proteins were significantly associated with PFS (ANG2, IL6, IL8, CA9, CA15-3) and OS (ANG2, sTIE2, IL6, IL8, CA9, CA15-3). After one cycle, VEGF-A, ANG2, sTIE2, and IL8 significantly decreased, while sVEGFR2 and CA9 significantly increased. The relative change in sVEGFR2 (P= 0.01) and IL8 (P= 0.001) was associated with response. Defining optimal cut-off, patients with a high CA9 rise (>2.9%) had better PFS (HR 0.45) and OS (HR 0.54) than those with low/no rise.

CONCLUSIONS

Multiple angiogenesis- or hypoxia-related proteins were prognostic for PFS and OS. Molecular agents targeting these proteins might be beneficial in patients with high levels. Changes in IL8 or sVEGFR2 levels at second cycle appear predictive for response. Changes in CA9 levels during bevacizumab-based therapy for prediction of PFS and OS merit further study.

[Changes of angiopoietin 1 expression in G-CSF induced hematopoietic stem progenitor cells mobilization]

目的

探讨G-CSF诱导的造血干／祖细胞（HSPC）动员过程中血管生成素1(Ang1)在小鼠骨髓的表达变化及导致其变化的机制。

方法

采用流式细胞术检测小鼠动员前及动员后外周血Lin⁻Sca1⁺cKit⁺(LSK)细胞比例变化，并应用ELISA、免疫组化、RQ-PCR等方法检测G-CSF动员不同时间点小鼠外周血和骨髓标本，观察Ang1、骨钙素（OCN）基因及蛋白水平变化，显微镜下计数骨髓标本成骨细胞数量。

结果

G-CSF动员5 d小鼠外周血LSK细胞比例为（0.61±0.05)%，相对于对照组的(0.04±0.01)%显著增高(P<0.05)；稳态小鼠OCN及Ang1 mRNA在骨内膜细胞表达高于骨髓有核细胞；动员后骨内膜细胞OCN及Ang1 mRNA相对表达量对照组（28.64±8.61及2.84±0.95)、G-CSF动员3 d组（12.55±7.06及0.93±0.30）及动员5 d组（4.75±1.62及0.92±0.22）均下降；动员后骨内膜成骨细胞数量显著减少，骨髓组织Ang1蛋白表达下降；对照组、动员3 d及5 d组外周血OCN及Ang1浓度分别为（24.11±3.17）及（2.24±0.52)ng/ml、(9.96±2.16）及（1.21±0.38)ng/ml和（8.43±2.62）及(0.90±0.24) ng/ml，动员3 d及5 d组均明显低于对照组，差异均有统计学意义(P值均<0.05)。

结论

在G-CSF介导的HSPC动员过程中，骨髓微环境中成骨细胞数量下降、功能减低，进而导致骨髓Ang1表达下降，导致骨髓对HSPC的趋化和黏附能力下降，有利于HSPC动员的发生。

Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle

Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.

The study on vascularisation and osteogenesis of BMP/VEGF co-modified tissue engineering bone in vivo

To evaluate the osteogenic capacity of tissue engineering bone in vivo and compare the vascularization and osteogenesis between co- and single-modified tissue engineered bone.

Protective Role of Selenium Compounds on the Proliferation, Apoptosis, and Angiogenesis of a Canine Breast Cancer Cell Line

We herein examined the effects of different doses, forms, and compatibilities of selenium on a canine mammary gland tumor cell line, CTM1211, and explored the related mechanisms. Three selenium compounds, sodium selenite (SSE), methylseleninic acid (MSA), and methylselenocysteine (MSC), were selected for these experiments, and cyclophosphamide (CTX) served as a positive control. In the cell viability assay, the cell viability of each group at 48/72 h decreased significantly compared with the control group (p < 0.05), and the cell viability of the CTX + MSA group was lower than that of CTX and MSA groups (p < 0.05). Moreover, the inhibitory effect of selenium on cell proliferation was time-dependent but not concentration-dependent. In the cell apoptosis assay, the apoptosis values of each group increased significantly compared with the control group, and the apoptosis values of the CTX + MSA group increased the most significantly (p < 0.01). The protein and mRNA expression levels of vascular endothelial growth factor-alpha (VEGF-alpha), angiopoietin-2 (Ang-2), and hypoxia inducible factor-1 alpha (HIF-1 alpha) were downregulated in each group, while that of phosphatase and tensin homolog (PTEN) were upregulated (p < 0.05). In conclusion, these three selenium compounds, especially MSA, could significantly inhibit the viability and growth of the CTM1211 cell line, which is partly due to the induction of apoptosis and regulation of tumor angiogenesis.

Evaluating the Impact of Human Amnion Epithelial Cells on Angiogenesis

The effects of human amnion epithelial cells (hAECs) on angiogenesis remain controversial. It is yet unknown if the presence of inflammation and/or gestational age of hAEC donors have an impact on angiogenesis. In this study, we examined the differences between term and preterm hAECs on angiogenesis in vitro and in vivo. Conditioned media from term hAECs induced the formation of longer huVEC tubules on Matrigel. Both term and preterm hAECs expressed VEGFA, PDGFB, ANGPT1, and FOXC1, which significantly increased after TNFα and IFNγ stimulation. In the presence of TNFα and IFNγ, coculture with term hAECs reduced gene transcription of Tie-2 and Foxc1 in huVECs, while coculture with preterm hAECs increased gene transcription of PDGFRα and PDGFRβ and reduced gene transcription of FOXC1 in huVECs. In vivo assessment of angiogenesis using vWF immunostaining revealed that hAEC treatment decreased angiogenesis in a bleomycin model of lung fibrosis but increased angiogenesis in a neonatal model of hyperoxia-induced lung injury. In summary, our findings suggested that the impact of hAECs on angiogenesis may be influenced by the presence of inflammation and underlying pathology.

Ordinary and Activated Bone Grafts: Applied Classification and the Main Features

Bone grafts are medical devices that are in high demand in clinical practice for substitution of bone defects and recovery of atrophic bone regions. Based on the analysis of the modern groups of bone grafts, the particularities of their composition, the mechanisms of their biological effects, and their therapeutic indications, applicable classification was proposed that separates the bone substitutes into “ordinary” and “activated.” The main differential criterion is the presence of biologically active components in the material that are standardized by qualitative and quantitative parameters: growth factors, cells, or gene constructions encoding growth factors. The pronounced osteoinductive and (or) osteogenic properties of activated osteoplastic materials allow drawing upon their efficacy in the substitution of large bone defects.

Expression of Angiogenic Factors in Patients With Sporadic Small Bowel Angiodysplasia

GOALS

To identify putative angiogenic factors associated with sporadic small bowel angiodysplasia (SBA).

BACKGROUND

SBAs account for 50% of obscure gastrointestinal bleeding and due to delays in diagnosis and ineffective treatments, are associated with high levels of morbidity and mortality. Treatment development is impeded by a limited knowledge of the pathophysiology behind SBA formation.

STUDY

We identified patients with definite sporadic SBA, and fecal immunochemical-negative controls were recruited from our institution's colorectal cancer screening program. Serum levels of VEGF, endoglin, Angiopoietin-2 (Ang-2), PDGF, Angiopoietin-1 (Ang-1), and TNF-α were measured using commercially available enzyme-linked immunosorbent assay kits. On the basis of serum results, we measured gene expression of target angiogenic factors in small bowel biopsy samples from angiodysplasias and unaffected tissue by quantitative PCR assessment.

RESULTS

Serum samples were analyzed from 40 SBA patients and 40 controls. Median serum levels of Ang-2 were significantly higher in patients than controls with levels of Ang-1 and TNF-α significantly lower. There were no differences in serum levels of VEGF, endoglin, or PDGF. Gene expression levels of Ang-1, Ang-2, and their receptor Tie2 were all significantly higher in biopsies from areas of angiodysplasia compared with normal small bowel.

CONCLUSIONS

This study, the first to explore the role of angiogenic factors in SBA, has identified a positive association between SBA and the Angiopoietin pathway, with increased serum and mucosal expression of Ang-2, which could potentially be used as a serum biomarker and future therapeutic target to improve outcome in affected patients.

Tie-1: A potential target for anti-angiogenesis therapy

The tyrosine kinase system angiopoietin (Ang)/Tie interacts with vascular endothelial growth factor pathway and regulates vessel quiescence in adults as well as later steps of the angiogenic cascade related to vessel maturation. Since all Angs are able to bind to Tie-2 but none binds to Tie-1, the function of Tie-2 and its ligands have captured attention. However, emerging evidence indicates unique roles of the orphan receptor Tie-1 in angiogenesis under physiological and pathological conditions. It is required for maintaining vascular endothelial cell integrity and survival during murine embryo development and in adult and may be involved in modulating differentiation of hematopoietic cells in adult. Tie-1 exhibits poor tyrosine kinase activity and signals via forming heterodimers with Tie-2, inhibiting Tie-2 signaling mediated by Angs. This inhibition can be relieved by Tie-1 ectodomain cleavage mediated by tumor- and inflammatory-related factors, which causes destabilization of vessels and initiates vessel remodeling. Up-regulated Tie-1 expression has been found not only in some leukemia cells and tumor related endothelial cells but also in cytoplasm of carcinoma cells of a variety of human solid tumors, which is associated with tumor progression. In addition, it has pro-inflammatory functions in endothelial cells and is involved in some inflammatory diseases associated with angiogenesis. Recent research indicated that Tie-1 gene ablation exhibited significant effects on tumor blood- and lymph-angiogenesis and improved anti-Ang therapy, suggesting Tie-1 may be a potential target for tumor anti-angiogenesis treatment.

The great escape; the hallmarks of resistance to antiangiogenic therapy

The concept of antiangiogenic therapy in cancer treatment has led to the approval of different agents, most of them targeting the well known vascular endothelial growth factor pathway. Despite promising results in preclinical studies, the efficacy of antiangiogenic therapy in the clinical setting remains limited. Recently, awareness has emerged on resistance to antiangiogenic therapies. It has become apparent that the intricate complex interplay between tumors and stromal cells, including endothelial cells and associated mural cells, allows for escape mechanisms to arise that counteract the effects of these targeted therapeutics. Here, we review and discuss known and novel mechanisms that contribute to resistance against antiangiogenic therapy and provide an outlook to possible improvements in therapeutic approaches.

Vascular dysfunction as a target for adjuvant therapy in cerebral malaria

Cerebral malaria (CM) is a life-threatening complication of Plasmodium falciparum malaria that continues to be a major global health problem. Brain vascular dysfunction is a main factor underlying the pathogenesis of CM and can be a target for the development of adjuvant therapies for the disease. Vascular occlusion by parasitised red blood cells and vasoconstriction/vascular dysfunction results in impaired cerebral blood flow, ischaemia, hypoxia, acidosis and death. In this review, we discuss the mechanisms of vascular dysfunction in CM and the roles of low nitric oxide bioavailability, high levels of endothelin-1 and dysfunction of the angiopoietin-Tie2 axis. We also discuss the usefulness and relevance of the murine experimental model of CM by Plasmodium berghei ANKA to identify mechanisms of disease and to screen potential therapeutic interventions.

Regulation of skeletal muscle capillary growth in exercise and disease

Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations.

The stereotypical molecular cascade in neovascular age-related macular degeneration: the role of dynamic reciprocity

This review summarises our current understanding of the molecular basis of subretinal neovascularisation (SRNV) in age-related macular degeneration (AMD). The term neovascular AMD (NVAMD) is derived from the dominant early clinical features of haemorrhage, fluid, and lipid in the subretinal space (SRS) and the historical role of fluorescein angiography in detecting the presence of NV tissue. However, at the cellular level, SRNV resembles an aberrant but stereotypical tissue repair response that incorporates both an early inflammatory phase and a late fibrotic phase in addition to the neovascular (NV) component that dominates the early clinical presentation. This review will seek not only to highlight the important molecules involved in each of these components but to demonstrate that the development of SRNV has its origins in the earliest events in non-NV AMD pathogenesis. Current evidence suggests that this early-stage pathogenesis is characterised by complement-mediated immune dysregulation, leading to a state of chronic inflammation in the retinal pigment epithelium/Bruch's membrane/choriocapillaris complex. These initial events can be seamlessly and inextricably linked to late-stage development of SRNV in AMD by the process of dynamic reciprocity (DyR), the ongoing bidirectional communication between cells, and their surrounding matrix. Moreover, this correlation between disease onset and eventual outcome is reflected in the temporal and spatial correlation between chronic inflammation, NV, and fibrosis within the reparative microenvironment of the SRS. In summary, the downstream consequences of the earliest dysfunctional molecular events in AMD can result in the late-stage entity we recognize clinically as SRNV and is characterized by a spectrum of predictable, related, and stereotypical processes referred to as DyR.

Classical and non-classical proangiogenic factors as a target of antiangiogenic therapy in tumor microenvironment

Angiogenesis is sustained by classical and non-classical proangiogenic factors (PFs) acting in tumor microenvironment and these factors are also potential targets of antiangiogenic therapies. All PFs induce the overexpression of several signaling pathways that lead to migration and proliferation of endothelial cells contributing to tumor angiogenesis and survival of cancer cells. In this review, we have analyzed each PF with its specific receptor/s and we have summarized the available antiangiogenic drugs (e.g. monoclonal antibodies) targeting these PFs, some of these agents have already been approved, others are currently in development for the treatment of several human malignancies.

Inosculation potential of angiopoietin-4-immobilized pHEMA-based bone scaffolds

Although angiopoietin-1has potential therapeutic use in angiogenesis, the biological role of angiopoietin-4, especially in its immobilized form, is already unknown. In this study, vascularization potential of angiopoietin-4 either alone or in combination with vascular endothelial growth factor (VEGF) was investigated following its immobilization onto the poly(2-hydroxyethyl methacrylate)-based bone scaffolds. Poly(2-hydroxyethyl methacrylate) (pHEMA)-based superporous hydrogels (SPHs) were synthesized by radical polymerization of hydroxyethyl methacrylate in the presence of gelatin or chitosan and the porosity was achieved by gas foaming. However, only pHEMA-gelatin SPHs fulfill the structural and biological characteristics of a bone scaffold. Therefore, angiopoietin-4 and/or VEGF were immobilized successfully onto the pHEMA–gelatin SPHs using carbodiimide chemistry. The cell culture studies that were performed with human umbilical vein endothelial cells (HUVECs) for 28 days showed that immobilized angiopoietin-4 supported sprout formation more than that of other groups, while the immobilized VEGF including scaffolds promoted proliferation of HUVECs.

A secretomic study on human hepatocellular carcinoma multiple drug-resistant cell lines

The aim of this study was to identify pivotal dysregulated proteins that are biomarkers for multiple drug resistance (MDR) of human hepatocellular carcinoma (HCC). The secretome profiles of the human HCC MDR cell line BEL7402/5-FU and its parental cell line BEL7402 were comparatively analyzed using isobaric tags for the relative and absolute quantification (iTRAQ)-coupled 2D LC-MS/MS. In total, 279 differentially expressed proteins were identified, of which, with a consistent result in the duplex test, 131 proteins were overexpressed in BEL7402/5-FU compared to its parental cell line, and 56 proteins were underexpressed. Several differentially expressed proteins determined by western blot analysis were also validated. The association of MDR with one of the highly regulated proteins, α-2-HS-glycoprotein (AHSG) was determined. This study detailed the application of iTRAQ technology to MDR biomarkers in the HCC cell secretome. The results showed that differentially expressed proteins that may be associated with MDR of HCC provide valuable additional information with regard to understanding the role of MDR.

Imidazole-based alkaloid derivative LCB54-0009 suppresses ocular angiogenesis and lymphangiogenesis in models of experimental retinopathy and corneal neovascularization

BACKGROUND AND PURPOSE

Abnormally induced angiogenesis and lymphangiogenesis are associated with human diseases, including neovascular eye disease. Substances that inhibit these processes may have potential as an attractive therapeutic strategy for these diseases.

EXPERIMENTAL APPROACH

In vitro and in vivo angiogenesis and/or lymphangiogenesis were assessed in VEGF- or hypoxia-stimulated endothelial and retinal cells and in animal models of oxygen-induced retinopathy (OIR), streptozotocin-induced diabetic retinopathy (SIDR), suture-induced inflammatory corneal neovascularization (SICNV) and silver nitrate-induced corneal neovascularization. HUVECs and retinal cells were cultured under hypoxic conditions or incubated with VEGF to identify the molecular mechanisms involved.

KEY RESULTS

The imidazole-based alkaloid derivative LCB54-0009 inhibited capillary-like tube formation in VEGF-induced HUVECs without inducing cytotoxic effects. Intravitreal injection of LCB54-0009 into retinas suppressed the formation of the pathological neovascular tufts and increased vascular permeability in both OIR of mice and SIDR of rats. Furthermore, subconjunctival injection of LCB54-0009 into the cornea suppressed corneal inflammation and inflammation-associated angiogenesis and lymphangiogenesis in SICNV of mice and silver nitrate cauterization of rats. These pharmacological activities were associated with effects on HIF-1α protein stability and HIF-1α/NF-κB redox sensitivity through its antioxidant activities. LCB54-0009 also inhibited the hypoxia-induced expression of angiopoietin-2, and VEGF-induced VEGFR-2 activation and downstream signalling, resulting in the down-regulation of the expression of pro-angiogenic factors and pro-inflammatory mediators and an up-regulation of the expression of anti-angiogenic factors.

CONCLUSIONS AND IMPLICATIONS

LCB54-0009 is a potential candidate molecule for blocking pathological angiogenesis and lymphangiogenesis mediated by HIF-1α- angiopoietin-2 expression and VEGFR-2 activation.

Malaria in Pregnancy Interacts with and Alters the Angiogenic Profiles of the Placenta

Malaria in pregnancy remains a substantial public health problem in malaria-endemic areas with detrimental outcomes for both the mother and the foetus. The placental changes that lead to some of these detrimental outcomes have been studied, but the mechanisms that lead to these changes are still not fully elucidated. There is some indication that imbalances in cytokine cascades, complement activation and angiogenic dysregulation might be involved in the placental changes observed. Nevertheless, the majority of studies on malaria in pregnancy (MiP) have come from areas where malaria transmission is high and usually restricted to Plasmodium falciparum, the most pathogenic of the malaria parasite species. We conducted a cross-sectional study in Cruzeiro do Sul, Acre state, Brazil, an area of low transmission and where both P. vivax and P. falciparum circulate. We collected peripheral and placental blood and placental biopsies, at delivery from 137 primigravid women and measured levels of the angiogenic factors angiopoietin (Ang)-1, Ang-2, their receptor Tie-2, and several cytokines and chemokines. We measured 4 placental parameters (placental weight, syncytial knots, placental barrier thickness and mononuclear cells) and associated these with the levels of angiogenic factors and cytokines. In this study, MiP was not associated with severe outcomes. An increased ratio of peripheral Tie-2:Ang-1 was associated with the occurrence of MiP. Both Ang-1 and Ang-2 had similar magnitudes but inverse associations with placental barrier thickness. Malaria in pregnancy is an effect modifier of the association between Ang-1 and placental barrier thickness.

Regulation of Angiogenic Functions by Angiopoietins through Calcium-Dependent Signaling Pathways

Angiopoietins are vascular factors essential for blood vessel assembly and correct organization and maturation. This study describes a novel calcium-dependent machinery activated through Angiopoietin-1/2-Tie receptor system in HUVECs monolayer. Both cytokines were found to elicit intracellular calcium mobilization. Targeting intracellular Ca²⁺ signaling, antagonizing IP₃ with 2-APB or cADPR with 8Br-cADPR, was found to modulate in vitro angiogenic responses to Angiopoietins in a specific way. 2-APB and 8Br-cADPR impaired the phosphorylation of AKT and FAK induced by Ang-1 and Ang-2. On the other hand, phosphorylation of ERK1/2 and p38, as well as cell proliferation, was not affected by either inhibitor. The ability of ECs to migrate following Angs stimulation, evaluated by “scratch assay,” was reduced by either 2-APB or 8Br-cADPR following Ang-2 stimulation and only slightly affected by 2-APB in cells stimulated with Ang-1. These results identify a novel calcium-dependent machinery involved in the complex interplay regulating angiogenic processes showing that IP₃- and cADPR-induced Ca²⁺ release specifically regulates distinct Angs-mediated angiogenic steps.

Insulin-resistant subjects have normal angiogenic response to aerobic exercise training in skeletal muscle, but not in adipose tissue

Reduced vessel density in adipose tissue and skeletal muscle is associated with obesity and may result in decreased perfusion, decreased oxygen consumption, and insulin resistance. In the presence of VEGFA, Angiopoietin-2 (Angpt2) and Angiopoietin-1 (Angpt1) are central determinants of angiogenesis, with greater Angpt2:Angpt1 ratios promoting angiogenesis. In skeletal muscle, exercise training stimulates angiogenesis and modulates transcription of VEGFA, Angpt1, and Angpt2. However, it remains unknown whether exercise training stimulates vessel growth in human adipose tissue, and it remains unknown whether adipose angiogenesis is mediated by angiopoietin signaling. We sought to determine whether insulin-resistant subjects would display an impaired angiogenic response to aerobic exercise training. Insulin-sensitive (IS, N = 12) and insulin-resistant (IR, N = 14) subjects had subcutaneous adipose and muscle (vastus lateralis) biopsies before and after 12 weeks of cycle ergometer training. In both tissues, we measured vessels and expression of pro-angiogenic genes. Exercise training did not increase insulin sensitivity in IR Subjects. In skeletal muscle, training resulted in increased vessels/muscle fiber and increased Angpt2:Angpt1 ratio in both IR and IS subjects. However, in adipose, exercise training only induced angiogenesis in IS subjects, likely due to chronic suppression of VEGFA expression in IR subjects. These results indicate that skeletal muscle of IR subjects exhibits a normal angiogenic response to exercise training. However, the same training regimen is insufficient to induce angiogenesis in adipose tissue of IR subjects, which may help to explain why we did not observe improved insulin sensitivity following aerobic training.

Cartilage Oligomeric Matrix Protein Angiopoeitin-1 Provides Benefits During Nerve Regeneration In Vivo and In Vitro

Our group pioneered the study of nerve regeneration in China and has successfully developed human "acellular nerve grafts (ACNGs)". However, our clinical studies revealed that the effects of ACNGs for long and large nerve defects are far from satisfactory. To improve the efficacy of ACNGs, we combined Cartilage oligomeric matrix protein angiopoietin-1 (COMP-Ang1) with ACNGs in rat sciatic nerve injury models and observed the outcomes via angiographic, morphological, and functional analyses. Co-cultures of endothelial cells (ECs) and dorsal root ganglion neurons (DRGs) were also used to characterize the relationship between neovascularization and nerve regeneration. The results showed significant improvements in early neovascularization, nerve regeneration, and functional outcomes in vivo in the ACNG + COMP-Ang1 group. In vitro, neurite length, and density as well as the expression levels of neurofilament 68 (NF68) and phosphorylated-Tie-2 (p-Tie-2) significantly increased when ECs were co-cultured with DRGs using COMP-Ang1. p-Tie-2 expression dramatically decreased after treatment with a Tie-2 kinase inhibitor (S157701), which consequently decreased the level of NF68. COMP-Ang1 can be concluded to promote early neovascularization followed by brisk nerve regeneration, and the mechanism of this regeneration may involve the modulation of the p-Tie-2 and Tie-2 receptors on ECs. These findings demonstrate that ACNGs can be modified using COMP-Ang1 to improve their efficacy in repairing peripheral nerve defects in clinical trials.

Muscle cell derived angiopoietin-1 contributes to both myogenesis and angiogenesis in the ischemic environment

Recent strategies to treat peripheral arterial disease (PAD) have focused on stem cell based therapies, which are believed to result in local secretion of vascular growth factors. Little is known, however, about the role of ischemic endogenous cells in this context. We hypothesized that ischemic muscle cells (MC) are capable of secreting growth factors that act as potent effectors of the local cellular regenerative environment. Both muscle and endothelial cells (ECs) were subjected to experimental ischemia, and conditioned medium (CM) from each was collected and analyzed to assess myogenic and/or angiogenic potential. In muscle progenitors, mRNA expression of VEGF and its cognate receptors (Nrp1, Flt, Flk) was present and decreased during myotube formation in vitro, and EC CM or VEGF increased myoblast proliferation. Angiopoietin-1 (Ang-1), Tie1, and Tie2 mRNA increased during MC differentiation in vitro. Exogenous Ang-1 enhanced myogenic (MyoD and Myogenin) mRNA in differentiating myoblasts and increased myosin heavy chain protein. Myotube formation was enhanced by MC CM and inhibited by EC CM. Ang-1 protein was present in CM from MCs isolated from both the genetically ischemia-susceptible BALB/c and ischemia-resistant C57BL/6 mouse strains, and chimeric Tie2 receptor trapping in situ ablated Ang-1's myogenic effects in vitro. Ang-1 or MC CM enhanced myotube formation in a mixed isolate of muscle progenitors as well as a myoblast co-culture with pluripotent mesenchymal cells (10T1/2) and this effect was abrogated by viral expression of the extracellular domain of Tie2 (AdsTie2). Furthermore, mesh/tube formation by HUVECs was enhanced by Ang-1 or MC CM and abrogated by Tie2 chimeric receptor trapping. Our results demonstrate the ability of muscle and endothelial cell-derived vascular growth factors, particularly Ang-1, to serve as multi-functional stimuli regulating crosstalk between blood vessels and muscle cells during regeneration from ischemic myopathy.

Fibrinogen-Related Proteins in Tissue Repair: How a Unique Domain with a Common Structure Controls Diverse Aspects of Wound Healing

Significance: Fibrinogen-related proteins (FRePs) comprise an intriguing collection of extracellular molecules, each containing a conserved fibrinogen-like globe (FBG). This group includes the eponymous fibrinogen as well as the tenascin, angiopoietin, and ficolin families. Many of these proteins are upregulated during tissue repair and exhibit diverse roles during wound healing. Recent Advances: An increasing body of evidence highlights the specific expression of a number of FRePs following tissue injury and infection. Upon induction, each FReP uses its FBG domain to mediate quite distinct effects that contribute to different stages of tissue repair, such as driving coagulation, pathogen detection, inflammation, angiogenesis, and tissue remodeling. Critical Issues: Despite a high degree of homology among FRePs, each contains unique sequences that enable their diversification of function. Comparative analysis of the structure and function of FRePs and precise mapping of regions that interact with a variety of ligands has started to reveal the underlying molecular mechanisms by which these proteins play very different roles using their common domain. Future Directions: Fibrinogen has long been used in the clinic as a synthetic matrix serving as a scaffold or a delivery system to aid tissue repair. Novel therapeutic strategies are now emerging that harness the use of other FRePs to improve wound healing outcomes. As we learn more about the underlying mechanisms by which each FReP contributes to the repair response, specific blockade, or indeed potentiation, of their function offers real potential to enable regulation of distinct processes during pathological wound healing.

Cancer-associated mesenchymal stem cells aggravate tumor progression

Mesenchymal stem cells (MSCs) have both stemness and multi-modulatory activities on other cells, and the immunosuppressive and tumor-promotive mechanisms have been intensively investigated in cancer. The role of MSCs appears to be revealed in tumor aggravation, and targeting MSCs seems to be a promising strategy for treating cancer patients. However, it is still impractical in clinical therapy, since the precise MSCs are poorly understood in the in vivo setting. In previous studies, MSCs were obtained from different sources, and were prepared by ex vivo expansion for a long term. The inconsistent experimental conditions made the in vivo MSCs obscure. To define the MSCs in the host is a priority issue for targeting MSCs in cancer therapy. We recently identified a unique subpopulation of MSCs increasing in mice and human with cancer metastasis. These MSCs are specifically expanded by metastatic tumor cells, and promote tumor progression and dissemination accompanied by immune suppression and dysfunction in the host, more powerfully than normal MSCs growing without interference of cancer. In this review, we summarize current knowledge of the role of MSCs in tumor aggravation, along with our new findings of the bizarre MSCs.

Angiopoietins promote ovarian cancer progression by establishing a procancer microenvironment

Despite decades of research, the survival rate of ovarian cancer patients is largely unchanged. Current chemotherapeutic drugs are effective only transiently because patients with advanced disease eventually develop resistance. Thus, there is a pressing need for identifying novel therapeutic targets in ovarian cancer. Mounting evidence suggests that angiopoietins (Angpts) may play an essential role in cancer progression; however, the expression profiles and biological effects of Angpts on ovarian cancer remain largely unknown. Here, we show that, compared with their normal counterparts, expressions of Angpt1, Angpt2, and Angpt4 are increased in ovarian cancer cells and tissues and that human ovarian cancer cells also express the Angpt receptor Tie-2-receptor tyrosine kinase. We show that increased expression of Angpt1, Angpt2, or Angpt4 promotes intraperitoneal growth of ovarian cancers and shortens survival of the experimental mice. We further show, for the first time, that Angpts promote accumulation of cancer-associated fibroblasts and tumor angiogenesis in the ovarian cancer microenvironment, as well as enhance ovarian cancer cell proliferation and invasion in vivo. In addition, we establish a novel function of Angpts in promoting proliferation and invasion and inducing Tie-2 and extracellular signal-regulated kinase 1/2 activation in ovarian cancer-associated fibroblasts. Taken together, these data suggest that the Angpt-Tie-2 functional axis is an important player in ovarian cancer progression and an attractive target for ovarian cancer therapy.

Hematopoietic stem and progenitor cells regulate the regeneration of their niche by secreting Angiopoietin-1

Hematopoietic stem cells (HSCs) are maintained by a perivascular niche in bone marrow but it is unclear whether the niche is reciprocally regulated by HSCs. Here, we systematically assessed the expression and function of Angiopoietin-1 (Angpt1) in bone marrow. Angpt1 was not expressed by osteoblasts. Angpt1 was most highly expressed by HSCs, and at lower levels by c-kit⁺ hematopoietic progenitors, megakaryocytes, and Leptin Receptor⁺ (LepR⁺) stromal cells. Global conditional deletion of Angpt1, or deletion from osteoblasts, LepR⁺ cells, Nes-cre-expressing cells, megakaryocytes, endothelial cells or hematopoietic cells in normal mice did not affect hematopoiesis, HSC maintenance, or HSC quiescence. Deletion of Angpt1 from hematopoietic cells and LepR⁺ cells had little effect on vasculature or HSC frequency under steady-state conditions but accelerated vascular and hematopoietic recovery after irradiation while increasing vascular leakiness. Hematopoietic stem/progenitor cells and LepR⁺ stromal cells regulate niche regeneration by secreting Angpt1, reducing vascular leakiness but slowing niche recovery.

DOI:http://dx.doi.org/10.7554/eLife.05521.001

In adults, blood cells develop from a set of stem cells that are found in bone marrow. There are also specialized blood vessels and cells called ‘stromal cells’ within the bone marrow that provide these stem cells with oxygen, nutrients, and other molecules. This local environment, or ‘niche’, plays an important role in regulating the maintenance of these stem cells. But it has not been known whether stem cells can reciprocally regulate their niches.

Unfortunately, radiation used to treat cancer obliterates the stem cells and their niche; both must recover after such a treatment before the patient can produce blood cells normally again. A protein called Angpt1 is thought to play a role in this post-treatment recovery. Angpt1 is known to regulate blood vessels in the bone marrow, and one influential study had previously suggested that bone cells produce Angpt1, which promotes and regulates the maintenance of the stem cells within the niche. However, this previous study did not directly test this. Thus, it was not clear whether Angpt1 promotes the regeneration of the stem cells themselves or if it regulates the rebuilding of the niche.

Now, Zhou, Ding and Morrison have genetically engineered mice to make a ‘reporter’ molecule—which glows green when viewed under a microscope—wherever and whenever the gene for Angpt1 is active. These experiments showed where the protein is produced, and unexpectedly revealed that the bone cells do not make Angpt1. Instead, it is the stem cells and the stromal cells in the niche that made the protein. Further experiments showed that deleting the gene for Angpt1 from mice, or just from their bone cells, did not affect blood cell production; nor did it affect the maintenance or regulation of the stem cells.

Next, Zhou, Ding and Morrison looked at whether Angpt1 might be involved in rebuilding the niche after being exposed to radiation. Some of these irradiated mice had been genetically engineered to lack Angpt1; and, in these mice, blood stem cells and blood cell production recovered more quickly than in mice with Angpt1. The blood vessels in the niche also grew back more quickly in the irradiated mice that lacked Angpt1. However, these regenerated blood vessels were leaky. This suggests that blood stem cells produce Angpt1 to slow the recovery of the niche and reduce leakage from the blood vessels. Thus, blood stem cells can regulate the regeneration of the niches that maintain them.

DOI:http://dx.doi.org/10.7554/eLife.05521.002