Increased Vascular Endothelial Growth Factor Secretion Research Articles

HIF-1α–dependent regulation of angiogenic factor expression in Müller cells by mechanical stimulation

Mechanical stress regulates various biological processes in cells, tissues, and organs as well as contributes to the pathogenesis of various diseases. The retina is subjected to mechanical stress imposed by intraocular pressure as well as by retinal hemorrhage and edema. Responses to mechanical stress have been studied in retinal pigment epithelial cells and Müller cells of the retina, with the former cells having been found to undergo a stress-induced increase in the expression of vascular endothelial growth factor (VEGF), which plays a key role in physiological and pathological angiogenesis in the retina. We here examined the effects of stretch stimulation on the expression of angiogenic factors in cultured human Müller cells. Reverse transcription and quantitative PCR analysis revealed that expression of the VEGF-A gene was increased by such stimulation in Müller cells, whereas that of the angiopoietin 1 gene was decreased. An enzyme-linked immunosorbent assay showed that stretch stimulation also increased VEGF secretion from these cells. Expression of the transcription factor HIF-1α (hypoxia-inducible factor–1α) was increased at both mRNA and protein levels by stretch stimulation, and the HIF-1α inhibitor CAY10585 prevented the effects of mechanical stress on VEGF-A gene expression and VEGF secretion. Furthermore, RNA-sequencing analysis showed that the expression of angiogenesis-related pathway genes was upregulated by stretch stimulation. Our results thus suggest that mechanical stress induces VEGF production in Müller cells in a manner dependent on HIF-1α, and that HIF-1α is therefore a potential therapeutic target for conditions such as diabetic retinopathy, age-related macular degeneration, and retinal vein occlusion.

Exosomes released by oxidative stress-induced mesenchymal stem cells promote murine mammary tumor progression through activating the STAT3 signaling pathway.

Mesenchymal stem cells (MSCs) may play a pivotal role in shaping the tumor microenvironment (TME), influencing tumor growth. Nonetheless, conflicting evidence exists regarding the distinct impacts of MSCs on tumor progression, with some studies suggesting promotion while others indicate suppression of tumor cell growth. Considering that oxidative stress is implicated in the dynamic interaction between components of the TME and tumor cells, we investigated the contribution of exosomes released by hydrogen peroxide (H2O2)-treated MSCs to murine mammary tumor growth and progression. Additionally, we aimed to identify the underlying mechanism through which MSC-derived exosomes affect breast tumor growth and angiogenesis. Our findings demonstrated that exosomes released by H2O2-treated, stress-induced MSCs (St-MSC Exo) promoted breast cancer cell progression by inducing the expression of vascular endothelial growth factor (VEGF) and markers associated with epithelial-to-mesenchymal transition. Further clarification revealed that the promoting effect of St-MSC Exo on VEGF expression may, in part, depend on activating STAT3 signaling in BC cells. In contrast, exosomes derived from untreated MSCs retarded JAK1/STAT3 phosphorylation and reduced VEGF expression. Additionally, our observations revealed that the activation of the transcription factor NF-κB in BC cells, stimulated with St-MSC Exo, occurs concurrently with an increase in intracellular ROS production. Moreover, we observed that the increase in VEGF secretion into the conditioned media of 4T1 BC, mediated by St-MSC Exo, positively influenced endothelial cell proliferation, migration, and vascular behavior in vitro. In turn, our in vivo studies confirmed that St-MSC Exo, but not exosomes derived from untreated MSCs, exhibited a significant promoting effect on breast tumorigenicity. Collectively, our findings provide new insights into how MSCs may contribute to modulating the TME. We propose a novel mechanism through which exosomes derived from oxidative stress-induced MSCs may contribute to tumor progression and angiogenesis.

Effect of VEGF on neurological impairment and prognosis of acute cerebral infarction patients: A retrospective case-control study.

Due to the complex pathological mechanism of acute cerebral infarction, the role of vascular endothelial growth factor (VEGF) on the disease is not clear. Therefore, a retrospective case-control study was performed to explore the effect of VEGF on neurological impairment and prognosis of acute cerebral infarction patients. A total of 100 patients with acute cerebral infarction admitted to our hospital from April 2021 to April 2022 were selected. Blood samples from all patients would be routinely collected to detect the expression of serum VEGF. Pearson chi-square, Spearman correlation and univariate Logistic regression were used to analyze the clinical data to explore the relationship between VEGF expression and basic information, stroke degree, quality of life, and prognosis of patients. To determine whether VEGF can provide relevant basis for the early prevention and prognostic treatment of acute cerebral infarction. And multivariate logistic regression was used to calculate the odds ratio between each variable and VEGF expression. Pearson chi-square test and Spearman correlation coefficient showed that sex, degree of stroke, limb convulsions, loss of consciousness, hemiplegia, aphasia, mental functioning score, overall quality of life score, and short-term prognosis were significantly correlated with VEGF expression in 100 patients. Univariate logistic regression was used to describe the ORs and 95% confidence interval of subjects at the univariate level, and the degree of stroke (OR = 83.333, P < 0.001), tic of limbs (OR = 26.316, P < 0.001), loss of consciousness (OR = 23.256, P < 0.001), hemiplegia (OR = 62.500, P < 0.001), aphasia (OR = 76.923, P < 0.001), mental functioning score (OR = 7.937, P < 0.001), overall quality of life score (OR = 5.464, P < 0.001), short-term prognosis (OR = 37.037, P < 0.001) was significantly correlated with the high expression of VEGF. The level of serum VEGF was positively correlated with neurological impairment degree and prognosis in patients with acute cerebral infarction, the more severe the degree of stroke and the worse the prognosis.

Astrocytic responses to high glucose impair barrier formation in cerebral microvessel endothelial cells.

Hyperglycemic conditions are prodromal to blood-brain barrier (BBB) impairment. The BBB comprises cerebral microvessel endothelial cells (CMECs) that are surrounded by astrocytic foot processes. Astrocytes express high levels of gap junction connexin 43 (Cx43), which play an important role in autocrine and paracrine signaling interactions that mediate gliovascular cross talk through secreted products. One of the key factors of the astrocytic "secretome" is vascular endothelial growth factor (VEGF), a potent angiogenic factor that can disrupt BBB integrity. We hypothesize that high-glucose conditions change the astrocytic expression of Cx43 and increase VEGF secretion leading to impairment of CMEC barrier properties in vitro and in vivo. Using coculture of neonatal rat astrocytes and CMEC, we mimic hyperglycemic conditions using high-glucose (HG) feeding media and show a significant decrease in Cx43 expression and the corresponding increase in secreted VEGF. This result was confirmed by the analyses of Cx43 and VEGF protein levels in the brain cortex samples from the type 2 diabetic rat (T2DN). To further characterize inducible changes in BBB, we measured transendothelial cell electrical resistance (TEER) and tight junction protein levels in cocultured conditioned astrocytes with isolated rat CMEC. The coculture monolayer's integrity and permeability were significantly compromised by HG media exposure, which was indicated by decreased TEER without a change in tight junction protein levels in CMEC. Our study provides insight into gliovascular adaptations to increased glucose levels resulting in impaired cellular cross talk between astrocytes and CMEC, which could be one explanation for cerebral BBB disruption in diabetic conditions.

Anticancer effect of the fruit and seed extracts of Momordica charantia L. (Cucurbitaceae) on human cancer cell lines

Purpose: To investigate anticancer effects of Momordica charantia L. (M. charantia) fruit and seed extracts on some cancer cell lines.&#x0D; Methods: Human cancer cell lines, including lung cancer (A549), breast cancer (MCF-7), chronic myeloid leukemia (K562) and T cell leukemia (Jurkat) were incubated with the extracts (0 - 0.8 mg/mL) for 72 h. The cytotoxic effects of the extracts were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5- dipenyltetrazolium bromide (MTT) assay. A549 and MCF-7 cells were treated with the ethanol fruit extract (FE) for 24 h and stained with propidium iodide (PI) for the analysis of cell cycle arrest using flow cytometry. Annexin V-FITC/PI staining along with flow cytometry analysis and caspase-3 assays were carried out to determine the apoptosis of the cells treated with FE extract for 24 h. Vascular endothelial growth factor (VEGF) secretion of the cells exposed to FE extract for 1 h was determined using enzyme-linked immunosorbent assay (ELISA). Cell invasion assay was applied to detect cell migration after treatment with FE extract for 48 h.&#x0D; Results: Ethanol fruit extract (FE) resulted in 90, 92, 85 and 87 % cytotoxicity against K562, A549, MCF-7 and Jurkat cell lines, respectively. However, ethanol seed extract of seed (SE) was less effective (≤42 %) on cytotoxicity against cancer cells. Acetone fruit extract (FA) caused 82, 75 and 59 % cytotoxicity on MCF-7, Jurkat and K562 cells, respectively, whereas 20 % cytotoxicity was observed on A549 cells. Dose analyses of FE extract indicated that K562 cells had the lowest IC50 value (0.082 mg/mL). In addition, FE extract treatment caused accumulation of A549 and MCF-7 cells in the S phase of the cell cycle. Moreover, apoptotic cell death was observed in A549 or MCF-7 cells treated with the FE extract. While the treatment of A549 cells with LPS for 24 h resulted in 19-fold increase in VEGF secretion, combination of FE with LPS caused 9.6-fold decrease in VEGF secretion, indicating the antiangiogenic activity of FE extract. Furthermore, FE extract treatment led to a significant decrease in the invasive properties of A549 and PC-3 cells when compared to untreated cells.&#x0D; Conclusion: Among the M. charantia extracts, FE extract displayed the highest anticancer potency against cancer cell lines, indicating that M. charantia FE extract may be a potential source for development of anticancer compounds in future.

3D cell sheet structure augments mesenchymal stem cell cytokine production

Mesenchymal stem cells (MSCs) secrete paracrine factors that play crucial roles during tissue regeneration. An increasing body of evidence suggests that this paracrine function is enhanced by MSC cultivation in three-dimensional (3D) tissue-like microenvironments. Toward this end, this study explored scaffold-free cell sheet technology as a new 3D platform. MSCs cultivated on temperature-responsive culture dishes to a confluent 2D monolayer were harvested by temperature reduction from 37 to 20 °C that induces a surface wettability transition from hydrophobic to hydrophilic. Release of culture-adherent tension induced spontaneous cell sheet contraction, reducing the diameter 2.4-fold, and increasing the thickness 8.0-fold to render a 3D tissue-like construct with a 36% increase in tissue volume. This 2D-to-3D transition reorganized MSC actin cytoskeleton from aligned to multidirectional, corresponding to a cell morphological change from elongated in 2D monolayers to rounded in 3D cell sheets. 3D culture increased MSC gene expression of cell interaction proteins, β-catenin, integrin β1, and connexin 43, and of pro-tissue regenerative cytokines, vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and interleukin-10 (IL-10), and increased VEGF secretion per MSC 2.1-fold relative to 2D cultures. Together, these findings demonstrate that MSC therapeutic potency can be enhanced by 3D cell sheet tissue structure.

VEGF and FGF-2 Released In Palatal Suture after Rapid Maxillary Expansion (RME).

Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) have the ability to increase vascular proliferation and permeability. The aim of this study was to quantify the release of two diffusible angiogenic growth factors (VEGF and FGF-2) after rapid maxillary expansion (RME). Thirty animals were randomly assigned to two groups. Control group (5 rats - intact suture) and Experimental groups (25 rats with RME) which were evaluated in different periods of treatment. Five animals were euthanized in different periods of healing at 0, 1, 2, 3, 5 and 7 days after RME. RT-PCR was used to evaluate the gene expression of angiogenic growth factors released on different periods of study. Data were submitted to statistical analysis using ANOVA followed by Tukey test and significance was assumed at a=0.05. RT-PCR showed that mRNAs of VEGF and FGF-2 were expressed in intact palatal suture tissue. mRNAs of VEGF and FGF-2 was upregulated in early periods (24 h) after RME (p<0.001 and p<0.01, respectively). The molecular levels of VEGF never returned to its original baseline values, and FGF-2 expression decreased up to day 5 (p<0.001) and suddenly increased at day 7, returning to its original level. RME increased VEGF secretion, but decreased FGF-2 secretion when compared to intact tissue. The results showed that these angiogenic growth factors are released and regulated in the palatal suture tissue after RME and could make an important contribution to the knowledge of overall reparative response of the suture tissue during the bone remodeling process.

The Influence of Melatonin and Light on VEGF Secretion in Primary RPE Cells

(1) Background: Retinal pigment epithelial cells (RPE) cells constitutively secrete vascular endothelial growth factor (VEGF) in the retina, protecting the neuronal cells and the choroid. Increased VEGF secretion, however, can result in neovascularization and edema. Many factors regulate VEGF secretion. In this study, we investigated the effect of external stimuli in relation to diurnal rhythm on constitutive VEGF secretion. (2) Methods: Single-eye RPE cell culture was prepared from porcine eyes. RPE cells were cultured in darkness, treated with daylight or room light, and treated with melatonin at different time frames, either respectively or in combination. Supernatants were collected and VEGF content evaluated using ELISA. Expression of the clock protein BMAL1 was evaluated with Western blot. (3) Results: VEGF secretion of the RPE shows a diurnal rhythm. While the rhythm is not influenced by either light or melatonin, the amount of secreted VEGF can be increased by nocturnal melatonin, especially in combination with morning daylight. These findings disclose another layer of VEGF regulation in the retina.

De novo Vessel Formation Through Cross-Talk of Blood-Derived Cells and Mesenchymal Stromal Cells in the Absence of Pre-existing Vascular Structures.

BackgroundThe generation of functional blood vessels remains a key challenge for regenerative medicine. Optimized in vitro culture set-ups mimicking the in vivo perivascular niche environment during tissue repair may provide information about the biological function and contribution of progenitor cells to postnatal vasculogenesis, thereby enhancing their therapeutic potential.AimWe established a fibrin-based xeno-free human 3D in vitro vascular niche model to study the interaction of mesenchymal stromal cells (MSC) with peripheral blood mononuclear cells (PBMC) including circulating progenitor cells in the absence of endothelial cells (EC), and to investigate the contribution of this cross-talk to neo-vessel formation.Materials and MethodsBone marrow-derived MSC were co-cultured with whole PBMC, enriched monocytes (Mo), enriched T cells, and Mo together with T cells, respectively, obtained from leukocyte reduction chambers generated during the process of single-donor platelet apheresis. Cells were embedded in 3D fibrin matrices, using exclusively human-derived culture components without external growth factors. Cytokine secretion was analyzed in supernatants of 3D cultures by cytokine array, vascular endothelial growth factor (VEGF) secretion was quantified by ELISA. Cellular and structural re-arrangements were characterized by immunofluorescence and confocal laser-scanning microscopy of topographically intact 3D fibrin gels.Results3D co-cultures of MSC with PBMC, and enriched Mo together with enriched T cells, respectively, generated, within 2 weeks, complex CD31+/CD34+ vascular structures, surrounded by basement membrane collagen type-IV+ cells and matrix, in association with increased VEGF secretion. PBMC contained CD31+CD34+CD45dimCD14– progenitor-type cells, and EC of neo-vessels were PBMC-derived. Vascular structures showed intraluminal CD45+ cells that underwent apoptosis thereby creating a lumen. Cross-talk of MSC with enriched Mo provided a pro-angiogenic paracrine environment. MSC co-cultured with enriched T cells formed “cell-in-cell” structures generated through internalization of T cells by CD31+CD45dim⁣/– cells. No vascular structures were detected in co-cultures of MSC with either Mo or T cells.ConclusionOur xeno-free 3D in vitro vascular niche model demonstrates that a complex synergistic network of cellular, extracellular and paracrine cross-talk can contribute to de novo vascular development through self-organization via co-operation of immune cells with blood-derived progenitor cells and MSC, and thereby may open a new perspective for advanced vascular tissue engineering in regenerative medicine.

Caveolin-1 Derived from Brain Microvascular Endothelial Cells Inhibits Neuronal Differentiation of Neural Stem/Progenitor Cells In Vivo and In Vitro

Caveolin-1 (Cav-1) is an important modulator for adult neurogenesis in post stroke brain repair but its underlying mechanisms are largely unknown. In the present study, we report that endothelial Cav-1 inhibits neuronal differentiation of neural stem/progenitor cells (NSCs/NPCs) in post ischemic brain via regulating vascular endothelial growth factor (VEGF) and NeuroD1 signaling pathway. We first investigated the dynamic change of Cav-1 and its impact on neuronal differentiation in rat and mouse models of 2 h transient middle cerebral artery occlusion (MCAO) plus 1, 7, 14, 21 and 28 day of reperfusion. We then studied the roles of endothelial Cav-1 in modulating the neuronal differentiation of NPCs which were co-cultured with brain microvascular endothelial cells (BMVECs) under 2 h oxygen-glucose deprivation plus 5 days reoxygenation (OGD/R). The major discoveries include: (1) Cav-1 expression in the hippocampal dentate gyrus (DG) was down-regulated on day 1 after 2 h cerebral ischemia, and gradually recovered with reperfusion time, accompanied with transient increased but gradually reduced neuronal differentiation of NPCs marked by doublecortin (DCX). (2) Cav-1 knockout mice exhibited the increased DCX and VEGF at the granular cell layers of hippocampal DG in post-ischemic brains. (3) Co-cultured with BMVECs, NPCs had remarkably decreased neuronal differentiation under OGD/R. Knockdown of Cav-1 in the BMVECs increased VEGF secretion into the medium and NeuroD1+ cells, and rescued the neuronal differentiation of NPCs without affecting astroglial and oligodendroglial differentiation. (4) Cav-1 exosomes released from BMVECs inhibited neuronal differentiation of NPCs via decreasing the expression of VEGF, p44/42MAPK phosphorylation and NeuronD1 upon OGD/R insults. Taken together, endothelial Cav-1 serves as a niche regulator to inhibit neuronal differentiation via negatively modulating VEGF, p44/42MAPK phosphorylation and NeuronD1 signaling pathway.

Vascular endothelial growth factor contributes to lung vascular hyperpermeability in sepsis-associated acute lung injury.

Vascular endothelial growth factor (VEGF) is a prime regulator of vascular permeability. Acute lung injury (ALI) is characterized by high-permeability pulmonary edema in addition to refractory hypoxemia and diffuse pulmonary infiltrates. In this study, we examined whether VEGF can be implicated as a pulmonary vascular permeability factor in sepsis-associated ALI. We found that a great increase in lung vascular leak occurred in mice instilled intranasally with lipopolysaccharide (LPS), as assessed by IgM levels in bronchoalveolar lavage fluid. Treatment with the VEGF-neutralizing monoclonal antibody bevacizumab significantly reduced this hyperpermeability response, suggesting active participation of VEGF in non-cardiogenic lung edema associated with LPS-induced ALI. However, this was not solely attributable to excessive levels of intrapulmonary VEGF. Expression levels of VEGF were significantly reduced in lung tissues from mice with both intranasal LPS administration and cecal ligation and puncture (CLP)-induced sepsis, which may stem from decreases in non-endothelial cells-dependent VEGF production in the lungs. In support of this assumption, stimulation with LPS and interferon-γ (IFN-γ) significantly increased VEGF in human pulmonary microvascular endothelial cells (HPMECs) at mRNA and protein levels. Furthermore, a significant rise in plasma VEGF levels was observed in CLP-induced septic mice. The increase in VEGF released from HPMECs after LPS/IFN-γ challenge was completely blocked by either specific inhibitor of mitogen-activated protein kinase (MAPK) subgroups. Taken together, our results indicate that VEGF can contribute to the development of non-cardiogenic lung edema in sepsis-associated ALI due to increased VEGF secretion from pulmonary vascular endothelial cells through multiple MAPK-dependent pathways.

Mechanical Cues Regulating Proangiogenic Potential of Human Mesenchymal Stem Cells through YAP-Mediated Mechanosensing.

Stem cells secrete trophic factors that induce angiogenesis. These soluble factors are promising candidates for stem cell-based therapies, especially for cardiovascular diseases. Mechanical stimuli and biophysical factors presented in the stem cell microenvironment play important roles in guiding their behaviors. However, the complex interplay and precise role of these cues in directing pro-angiogenic signaling remain unclear. Here, a platform is designed using gelatin methacryloyl hydrogels with tunable rigidity and a dynamic mechanical compression bioreactor to evaluate the influence of matrix rigidity and mechanical stimuli on the secretion of pro-angiogenic factors from human mesenchymal stem cells (hMSCs). Cells cultured in matrices mimicking mechanical elasticity of bone tissues in vivo show elevated secretion of vascular endothelial growth factor (VEGF), one of representative signaling proteins promoting angiogenesis, as well as increased vascularization of human umbilical vein endothelial cells (HUVECs) with a supplement of conditioned media from hMSCs cultured across different conditions. When hMSCs are cultured in matrices stimulated with a range of cyclic compressions, increased VEGF secretion is observed with increasing mechanical strains, which is also in line with the enhanced tubulogenesis of HUVECs. Moreover, it is demonstrated that matrix stiffness and cyclic compression modulate secretion of pro-angiogenic molecules from hMSCs through yes-associated protein activity.

Non-proteolytic calpain-6 interacts with VEGFA and promotes angiogenesis by increasing VEGF secretion

Angiogenesis is involved in both normal physiological and pathological conditions. Vascular endothelial growth factor (VEGF) is a major factor for promoting angiogenesis. The current anti-VEGF therapies have limited efficacy and significant adverse effects. To find novel targets of VEGFA for angiogenesis inhibition, we performed yeast two-hybrid screening and identified calpain-6 as a novel VEGFA-interaction partner and confirmed the endogenous VEGFA–calpain-6 interaction in mammalian placenta. A domain mapping study revealed that the Gly321–Asp500 domain in calpain-6 is required for the interaction with the C-terminus of the VEGFA protein. The functional significance of the VEGFA–calpain-6 interaction was explored by assessing its effect on angiogenesis in vitro. Whereas forced overexpression of calpain-6 increased the secretion of the VEGF protein and tube formation, knockdown of calpain-6 expression abrogated the calpain-6-mediated VEGF secretion and tube formation in HUVECs. Consistent with the domain mapping result, overexpressing calpain-6 without the VEGFA-interacting domain III (Gly321–Asp500) failed to increase the secretion of VEGF protein. Our results identify calpain-6, an unconventional non-proteolytic calpain, as a novel VEGFA-interacting protein and demonstrate that their interaction is necessary to enhance VEGF secretion. Thus, calpain-6 might be a potential molecular target for angiogenesis inhibition in many diseases.

Eicosapentaenoic acid suppresses angiogenesis via reducing secretion of IL‑6 and VEGF from colon cancer‑associated fibroblasts.

Eicosapentaenoic acid (EPA) improves interleukin (IL)‑6 hypercytokinemia in patients with advanced cancer due to its anti‑inflammatory effects. This EPA mechanism has been revealed to lead to several anticancer effects. While the effects of EPA on cancer cells have been investigated, particularly in terms of angiogenesis, its effects on the tumor stroma remain unclear. In the present study, the authors clarified the role of EPA in cancer angiogenesis against colon cancer‑associated fibroblasts (CAFs) from the colon stroma. With established human CAFs and normal fibroblasts from colon stroma (NFs), the authors evaluated IL‑6 and vascular endothelial growth factor (VEGF) secretion with or without EPA treatment using ELISA. The signal inhibition of mitogen‑activated protein kinase (ERK) in CAFs by EPA was evaluated using western blotting. In vitro anti‑angiogenesis effects were evaluated by the angiogenesis assay on Matrigel using human umbilical vein endothelial cells (HUVECs) cultured with the supernatant obtained from CAF cultures with or without EPA. IL‑6 secretion was greater from CAFs compared with that from NFs and stimulation with lipopolysaccharide (LPS) resulted in greater IL‑6 secretion from the two fibroblast types compared with that from fibroblasts without LPS stimulation. While LPS stimulation increased VEGF secretion from the two fibroblast types, EPA decreased IL‑6 and VEGF secretion from CAFs. Western blotting revealed that the addition of 30 µM EPA inhibited the ERK phosphorylation signal in CAFs. Furthermore, the angiogenesis assay with Matrigel revealed that the CAF culture supernatants treated with EPA suppressed tubular formation in HUVECs. These reductions may have been caused by the inhibition of ERK phosphorylation by EPA. Thus, EPA reduces cancer angiogenesis associated with CAFs. Additional studies will be needed to clarify the continuous anti‑angiogenetic effect of chemotherapy using angiogenesis inhibitors (e.g. bevacizumab and aflibercept) in conjunction with or without EPA, and the clinical usage of EPA in conjunction with chemotherapy in vivo.

Osteogenic Effects of VEGF-Overexpressed Human Adipose-Derived Stem Cells with Whitlockite Reinforced Cryogel for Bone Regeneration.

Bone is a vascularized tissue that is comprised of collagen fibers and calcium phosphate crystals such as hydroxyapatite (HAp) and whitlockite (WH). HAp and WH are known to elicit bone regeneration by stimulating osteoblast activities and osteogenic commitment of stem cells. In addition, vascular endothelial growth factor (VEGF) is shown to promote osteogenesis and angiogenesis which is considered as an essential process in bone repair by providing nutrients. In this study, VEGF-secreting human adipose-derived stem cells (VEGF-ADSCs) are developed by transducing ADSCs with VEGF-encoded lentivirus. Additionally, WH-reinforced gelatin/heparin cryogels (WH-C) are fabricated by loading WH into gelatin/heparin cryogels. VEGF-ADSC secrete tenfold more VEGF than ADSC and show increased VEGF secretion with cell growth. Also, incorporation of WH into cryogels provides a mineralized environment with ions secreted from WH. When the VEGF-ADSCs are seeded on WH-C, sustained release of VEGF is observed due to the specific affinity of VEGF to heparin. Finally, the synergistic effect of VEGF-ADSC and WH on osteogenesis is successfully confirmed by alkaline phosphatase and real-time polymerase chain reaction analysis. In vivo bone formation is demonstrated via implantation of VEGF-ADSC seeded WH-C into mouse calvarial bone defect model, resulted in enhanced bone development with the highest bone volume/total volume.

Inflection point in glioma growth and angiogenesis driven by potassium channels

Background and Aim: The overexpression and alternative splicing of calcium-activated potassium channel subunit alpha-1 (KCNMA1) that encodes large-conductance calcium-activated voltage-sensitive potassium (BKCa) channels are implicated in the development of human cancers. Dysfunctional angiogenesis in hypoxic tumors is a challenge to intravenous anticancer drug treatments. Hypoxic factors also lead to abnormal vascular functions posing hurdle for anticancer drug delivery to tumors. The aim of this study was to explore the role of BKCachannels in tumor angiogenesis, specifically with regard to release of vascular endothelial growth factor (VEGF). Materials and Methods: We subjected the glioma cells under hypoxia and normoxia and studied the expression and activity of BKCachannels in in vitro and in vivo tumor models. Then, we studied the proangiogenic factor, VEGF, in tumors and monitored the neoangiogenic process. The study protocol was approved by the Institutional Animal Care and Use Committee, Mercer University, Atlanta, GA, USA (approved No. A0706007_01) on July 20, 2007. Results: We presented in vivo and cell based in vitro experimental evidence on the direct and indirect interactions of BKCachannels with VEGF signaling. There was evidence that under hypoxia, glioma cells overexpressed KCNMA1 and increased VEGF secretion. By inhibiting KCNMA1, we showed that VEGF secretion was significantly reduced, thus potentially controlling angiogenesis, which has implications for vascular permeability and anticancer drug delivery. Moreover, there were differences in alternate splicing of KCNMA1 between normal and malignant cells under hypoxia and normoxia. Conclusion: We conclude that BKCachannels regulate hypoxia-induced angiogenesis. Therefore, serious effort is needed to better understand the molecular mechanisms of BKCachannelopathies triggering angiogenesis and progression of glioma. The modulators of BKCachannels could be viable in new anticancer therapeutics.

Induction of VEGF secretion from bone marrow stromal cell line (ST-2) by the dissolution products of mesoporous silica glass particles containing CuO and SrO

Certain biomaterials are capable of inducing the secretion of Vascular Endothelial Growth Factor (VEGF) from cells exposed to their biochemical influence, which plays a vital role in stimulating angiogenesis. Looking for this capacity, in this study three porous glasses were synthesized and characterized. Glass compositions (in mol-%) were: 60SiO2–(36-2x)CaO–4P2O5–xCuO–xSrO with x = 0, 1 or 2.5, respectively, for B60, CuSr-1 or CuSr-2.5 glasses. Cu2+ and Sr2+ ions were added because of the reported biological capabilities of Cu2+ as angiogenic stimulator and Sr2+ as osteogenic stimulator. The objective of this study was to determine the concentration of the glass particles that, being out of the cytotoxic range, could increase VEGF secretion. The viability of cultivated bone marrow stromal cells (ST-2) was assessed. The samples were examined with light microscopy (LM) after the histochemical staining for haematoxylin and eosin (HE). The biological activity of glasses was evaluated in terms of the influence of the Cu2+ and Sr2+ ions on the cells. The dissolution products of CuSr-1 and CuSr-2.5 produced the highest secretion of VEGF from ST-2 cells after 48 h of incubation. The combination of Cu2+ and Sr2+ lays the foundation for engineering a bioactive glass than can lead to vascularized, functional bone tissue when used in bone regeneration applications.

Thymosin β4 promotes endothelial progenitor cell angiogenesis via a vascular endothelial growth factor‑dependent mechanism.

Endothelial progenitor cells (EPCs) are a promising cell source for tissue repair and regeneration, predominantly through angiogenesis promotion. Paracrine functions serve a pivotal role in EPC‑mediated angiogenesis, which may be impaired by various cardiovascular risk factors. Therefore, it is important to identify a solution that optimizes the paracrine function of EPCs. Thymosin β4 (Tβ4) is a peptide with the potential to promote tissue regeneration and wound healing. A previous study demonstrated that Tβ4 enhances the EPC‑mediated angiogenesis of the ischemic myocardium. In the present study, whether Tβ4 improved angiogenesis by enhancing the paracrine effects of EPCs was investigated. A tube formation assay was used to assess the effect of angiogenesis, and the paracrine effects were measured using an ELISA kit. The results indicated that Tβ4 improved the paracrine effects of EPCs, evidenced by an increase in the expression of vascular endothelial growth factor (VEGF). EPC‑conditioned medium (EPC‑CM) significantly promoted human umbilical vein endothelial cell angiogenesis invitro, which was further enhanced by pretreatment with Tβ4. The effect of Tβ4 pretreated EPC‑CM on angiogenesis was abolished by VEGF neutralizing antibody invitro, indicating that increased VEGF secretion had a pivotal role in Tβ4‑mediated EPC angiogenesis. Furthermore, transplantation of EPCs pretreated with Tβ4 into infarcted rat hearts resulted in significantly higher VEGF expression in the border zone, compared with EPC transplantation alone. To further investigate whether the Akt/eNOS pathway was involved in Tβ4‑induced VEGF secretion in EPCs, the expression levels of VEGF in EPC‑CM were significantly decreased following knockdown of Akt or eNOS by small interfering RNA transfection. In conclusion, Tβ4 significantly increased angiogenesis by enhancing the paracrine effects of EPCs, evidenced by the increased expression of VEGF. The RAC‑α serine/threonine‑protein kinase/endothelial nitric oxide synthase signal transduction pathway was involved in the regulation of Tβ4‑induced VEGF secretion in EPCs. Further studies are required to investigate the long‑term prognosis of patients with coronary heart disease following Tβ4‑pretreated EPC transplantation.

116 - Hypoxia increases vegf secretion in multiple sources of mesenchymal stem cell

It is already known worldwide that mesenchymal stem cell (MSC) is rich in paracrine factors. In fact, numbers of paracrine factors have been discovered including chemokines and cytokines as well as pro-angiogenic factors contained therein. Co-culturing MSC with endothelial progenitor cell (EPC) improved EPC function without it was differentiated. This indicated that MSC secreted pro-angiogenic factors such as Vascular Endothelial Growth Factor (VEGF) which influence this phenomenon. The aim of this study is to investigate the influence of oxygen tension in VEGF secreted by MSC. Multiple MSCs; bone marrow (BM), adipose tissue (AD), and umbilical cord (UC)-derived mesenchymal stem cells were cultured up to 6th passage in Minimum Essential Medium (MEM) with 10% FBS and 1% Antibiotic-Antimycotic. After 80% confluency was reached, the culture medium was replaced with serum-free medium and incubated for 72 hours. These steps were done simultaneously in two different conditions; normoxia (21% O2) and hypoxia (3% O2). MSCs‘ secretome were collected and quantified by Enzyme-Linked Immunosorbent Assay (ELISA) method. VEGF secreted by hypoxic-conditioned MSCs increased more than 50 times compared to normoxic-conditioned ones. Our result showed that VEGF secreted by UC-MSC, BM-MSC, AD-MSC in normoxia were 2.436 pg/mL, 385.782 pg/mL, and 105.682 pg/mL respectively. On the other hand, VEGF secreted by UC-MSC, BM-MSC, AD-MSC in hypoxic condition were 2,795.982 pg/mL, 1,588.982 pg/mL, and 1,402.982 pg/mL respectively. After the culture was accomplished, the cells were also harvested to be checked further their immunophenotype and gene expressions. Surface markers of all three MSCs in both conditions showed no significant differences. Hypoxia-induced Factor 1-alpha (HIF1A) and VEGFA genes were expressed more intense in hypoxic-conditioned UC-MSCs than normoxic-conditioned ones. It can be concluded that in hypoxic condition, MSCs derived from umbilical cord, bone marrow, and adipose tissue increase VEGF secretion which possibly impacts their clinical outcome as cell therapies towards vascular diseases. Figure 2Genes expression (VEGFA and HIF1A) of umbilical cord derived mesenchymal stem cell in normoxia vs hypoxia 3%. View Large Image Figure Viewer Download Hi-res image Table IImmunophenotyping of UC-MSC, BM-MSC, AD-MSC in Normoxia (21% O2) Condition. MSC SURFACE MARKERS UC-MSC BM-MSC AT-MSC CD 105 90.75% 95.28% 96.5% CD 73 94.65% 99.34% 96.28% CD 90 92.76% 99.97% 99.85% Open table in a new tab Table IIImmunophenotyping of UC-MSC, BM-MSC, AD-MSC in Hypoxia (3% O2) Condition. MSC SURFACE MARKERS UC-MSC BM-MSC AT-MSC CD 105 95.52% 99.32% 95.37% CD 73 99.58% 99% 95.29% CD 90 99.47% 99.8% 95.27% Open table in a new tab

Engineering fibrin hydrogels to promote the wound healing potential of mesenchymal stem cell spheroids.

Mesenchymal stem cells (MSCs) are under investigation for wound healing applications due to their secretion of bioactive factors that enhance granulation tissue formation, blood vessel ingrowth, and reduce inflammation. However, the effectiveness of cell-based therapies is reduced due to poor engraftment and high rates of cell death when transplanted into harsh environments characteristic of large wounds. Compared to dissociated cells, MSCs exhibit increased overall function when aggregated into three-dimensional spheroids, and transplantation of cells using biomaterials is one strategy for guiding cell function in the defect site. The present study demonstrates that the biophysical properties of fibrin hydrogels, designed for use as a cell carrier, can be engineered to dictate the secretion of bioactive factors by entrapped MSC spheroids. This strategy enables MSCs to contribute to wound healing by synergistically promoting neovascularization and modulating the inflammatory milieu.