Effect of hypoxia on cellular adhesion to vitronectin and fibronectin

Regenerative potential of mesenchymal stromal cells in wound healing: unveiling the influence of normoxic and hypoxic environments

The innate and adaptive immune systems rely on the skin for various purposes, serving as the primary defense against harmful environmental elements. However, skin lesions may lead to undesirable consequences such as scarring, accelerated skin aging, functional impairment, and psychological effects over time. The rising popularity of mesenchymal stromal cells (MSCs) for skin wound treatment is due to their potential as a promising therapeutic option. MSCs offer advantages in terms of differentiation capacity, accessibility, low immunogenicity, and their central role in natural wound-healing processes. To accelerate the healing process, MSCs promote cell migration, angiogenesis, epithelialization, and granulation tissue development. Oxygen plays a critical role in the formation and expansion of mammalian cells. The term "normoxia" refers to the usual oxygen levels, defined at 20.21 percent oxygen (160 mm of mercury), while "hypoxia" denotes oxygen levels of 2.91 percent or less. Notably, the ambient O2 content (20%) in the lab significantly differs from the 2%-9% O2 concentration in their natural habitat. Oxygen regulation of hypoxia-inducible factor-1 (HIF-1) mediated expression of multiple genes plays a crucial role in sustaining stem cell destiny concerning proliferation and differentiation. This study aims to elucidate the impact of normoxia and hypoxia on MSC biology and draw comparisons between the two. The findings suggest that expanding MSC-based regenerative treatments in a hypoxic environment can enhance their growth kinetics, genetic stability, and expression of chemokine receptors, ultimately increasing their effectiveness.

Methylmercury cytotoxicity and possible mechanisms in human trophoblastic HTR-8/SVneo cells

Methylmercury (MeHg) exposure during pregnancy can lead to adverse outcomes, including miscarriage and intrauterine growth retardation. In this study, MeHg cytotoxicity and its mechanisms in HTR-8/SVneo cells were investigated. MeHg inhibited HTR-8/SVneo cell viability and severely disrupted the cellular submicrostructure, showing a time-dose effect relationship. After MeHg treatment, the reactive oxygen species levels, malondialdehyde content, and superoxide dismutase (SOD) and catalase activities in the HTR-8/SVneo cells increased significantly with increased MeHg concentration (P<0.05). Similarly, MeHg also induced HTR-8/SVneo cell apoptosis in a dose-dependent manner. The proportion of cells in G1 phase decreased with increasing MeHg concentration, while that in the S and G2/M phases gradually increased. Moreover, cell migration and invasion capacities gradually decreased with increasing MeHg concentration, showing a significant difference between the MeHg-treated and control groups. Genes related to oxidative stress (HSPA6, HSPA1A, Nrf2, SOD1, HO-1, NQO1, OSGIN1, and gPX1), cell cycle (P21 and CDC25A), apoptosis (CYCS and AIFM2), and migration and invasion (CXCL8, CXCL3, CLU, IL24, COL3A1, MAPT, and ITGA7) were differentially expressed in the MeHg-treated group, indicating MeHg toxicity and mechanism of action. This study will provide insights into the prevention and treatment of pregnancy-related diseases caused by MeHg.

Nitric oxide restores peripheral blood mononuclear cell adhesion against hypoxia via NO-cGMP signalling

Hypoxia is the most detrimental threat to humans residing at high altitudes, affecting multifaceted cellular responses that are crucial for normal homeostasis. Inhalation of nitric oxide has been successfully implemented to combat the hypoxia effect in the high altitude patients. We hypothesize that nitric oxide (NO) restores the peripheral blood mononuclear cell-matrix deadhesion during hypoxia. In the present study, we investigate the cellular action of exogenous NO in the hypoxia-mediated diminution of cell-matrix adhesion of PBMNC and NO bioavailability in vitro. The result showed that NO level and cell-matrix adhesion of PBMNC were significantly reduced in hypoxia as compared with normoxia, as assessed by the DAF-FM and cell adhesion assay, respectively. In contrast, cellular oxidative damage response was indeed upregulated in hypoxic PBMNC. Further, gene expression analysis revealed that mRNA transcripts of cell adhesion molecules (Integrin α5 and β1) and eNOS expressions were significantly downregulated. The mechanistic study revealed that administration of NO and 8-Br-cGMP and overexpression of eNOS-GFP restored the basal NO level and recovers cell-matrix adhesion in PBMNC via cGMP-dependent protein kinase I (PKG I) signalling. In conclusion, NO-cGMP/PKG signalling may constitute a novel target to recover high altitude-afflicted cellular deadhesion. SIGNIFICANCE OF THIS STUDY: Cellular adhesion is a complex multistep process. The ability of cells to adhere to extracellular matrix is an essential physiological process for normal homeostasis and function. Hypoxia exposure in the PBMNC culture has been proposed to induce oxidative damage and cellular deadhesion and is generally believed to be the key factor in the reduction of NO bioavailability. In the present study, we demonstrated that NO donor or overexpression of eNOS-GFP has a protective effect against hypoxia-induced cellular deadhesion and greatly improves the redox balance by inhibiting the oxidative stress. Furthermore, this protective effect of NO is mediated by the NO-cGMP/PKG signal pathway, which may provide a potential strategy against hypoxia.

Microtubule-associated protein 4 phosphorylation regulates epidermal keratinocyte migration and proliferation

Both cell migration and proliferation are indispensable parts of reepithelialization during skin wound healing, which is a complex process for which the underlying molecular mechanisms are largely unknown. Here, we identify a novel role for microtubule-associated protein 4 (MAP4), a cytosolic microtubule-binding protein that regulates microtubule dynamics through phosphorylation modification, as a critical regulator of epidermal wound repair. We showed that MAP4 phosphorylation was induced in skin wounds. In an aberrant phosphorylated MAP4 mouse model, hyperphosphorylation of MAP4 (S737 and S760) accelerated keratinocyte migration and proliferation and skin wound healing. Data from both primary cultured keratinocytes and HaCaT cells in vitro revealed the same results. The promigration and proproliferation effects of MAP4 phosphorylation depended on microtubule rearrangement and could be abolished by MAP4 dephosphorylation. We also identified p38/MAPK as an upstream regulator of MAP4 phosphorylation in keratinocytes. Our findings provide new insights into the molecular mechanisms underlying wound-associated keratinocyte migration and proliferation and identify potential targets for the remediation of defective wound healing.

Physiological Hypoxia (Physioxia) Impairs the Early Adhesion of Single Lymphoma Cell to Marrow Stromal Cell and Extracellular Matrix. Optical Tweezers Study

Adhesion is critical for the maintenance of cellular structures as well as intercellular communication, and its dysfunction occurs prevalently during cancer progression. Recently, a growing number of studies indicated the ability of oxygen to regulate adhesion molecules expression, however, the influence of physiological hypoxia (physioxia) on cell adhesion remains elusive. Thus, here we aimed: (i) to develop an optical tweezers based assay to precisely evaluate single diffuse large B-cell lymphoma (DLBCL) cell adhesion to neighbor cells (mesenchymal stromal cells) and extracellular matrix (Matrigel) under normoxia and physioxia; and, (ii) to explore the role of integrins in adhesion of single lymphoma cell. We identified the pronouncedly reduced adhesive properties of lymphoma cell lines and primary lymphocytes B under physioxia to both stromal cells and Matrigel. Corresponding effects were shown in bulk adhesion assays. Then we emphasized that impaired β1, β2 integrins, and cadherin-2 expression, studied by confocal microscopy, account for reduction in lymphocyte adhesion in physioxia. Additionally, the blockade studies conducted with anti-integrin antibodies have revealed the critical role of integrins in lymphoma adhesion. To summarize, the presented approach allows for precise confirmation of the changes in single cell adhesion properties provoked by physiological hypoxia. Thus, our findings reveal an unprecedented role of using physiologically relevant oxygen conditioning and single cell adhesion approaches when investigating tumor adhesion in vitro.

Hypoxia Enhances Fusion of Oral Squamous Carcinoma Cells and Epithelial Cells Partly via the Epithelial-Mesenchymal Transition of Epithelial Cells

Increasing evidence and indications showed that cell fusion is crucial in tumor development and metastasis, and hypoxia, a closely linked factor to tumor microenvironment, which can lead to EMT, induces angiogenesis and metastasis in tumor growth. However, the relationship between hypoxia and fusion has not been reported yet. EMT will change some proteins in the epithelial cell surface and the changes of proteins in cell surface may increase cell fusion. This study found that hypoxia promotes the spontaneous cell fusion between Oral Squamous Carcinoma Cells (OSCCs) and Human Immortalized Oral Epithelial Cells (HIOECs). At the same time, Hypoxia can lead to EMT, and hypoxia-pretreated HIOECs increased fusion rate with OSCC, while the fusion rate was significantly reduced by DAPT, a kind of EMT blocker. Therefore, epithelial cells can increase spontaneously cell fusion with OSCC by EMT. Our study may provide a new insight to link among tumor microenvironment, cell fusion, and cancer.

Human Mesenchymal Stem Cell Failure to Adapt to Glucose Shortage and Rapidly Use Intracellular Energy Reserves Through Glycolysis Explains Poor Cell Survival After Implantation

Mesenchymal stem cells (MSCs) hold considerable promise in tissue engineering (TE). However, their poor survival when exogenously administered limits their therapeutic potential. Previous studies from our group demonstrated that lack of glucose (glc) (but not of oxygen) is fatal to human MSCs because it serves as a pro-survival and pro-angiogenic molecule for human MSCs (hMSCs) upon transplantation. However, which energy-providing pathways MSCs use to metabolize glc upon transplantation? Are there alternative energetic nutrients to replace glc? And most importantly, do hMSCs possess significant intracellular glc reserves for ensuring their survival upon transplantation? These remain open questions at the forefront of TE based-therapies. In this study, we established for the first time that the in vivo environment experienced by hMSCs is best reflected by near-anoxia (0.1% O₂ ) rather than hypoxia (1%-5% O₂ ) in vitro. Under these near-anoxia conditions, hMSCs rely almost exclusively on glc through anerobic glycolysis for ATP production and are unable to use either exogenous glutamine, serine, or pyruvate as energy substrates. Most importantly, hMSCs are unable to adapt their metabolism to the lack of exogenous glc, possess a very limited internal stock of glc and virtually no ATP reserves. This lack of downregulation of energy turnover as a function of exogenous glc level results in a rapid depletion of hMSC energy reserves that explains their poor survival rate. These new insights prompt for the development of glc-releasing scaffolds to overcome this roadblock plaguing the field of TE based-therapies. Stem Cells 2018;36:363-376.

Hypoxia primed placental mesenchymal stem cells for wound healing

AIMS

To investigate how Placental Mesenchymal Stem Cells (P-MSCs) would adapt themselves and survive under hypoxic conditions which are prevalent in most injury sites.

MAIN METHODS

P-MSCs were isolated from term placenta and characterised under normoxia and hypoxia (2-2.5% O₂). Cells were examined for morphology and surface marker variations by flow cytometry analysis. Glucose stimulated insulin secretion was assayed by Insulin ELISA Kit. Gene expression levels were estimated using Real Time PCR for hypoxia inducible factor1 alpha, Insulin (INS), Glucose transporters (GLUT-1, GLUT-2 and GLUT-3), Adhesion Proteins- Integrins, Fibronectin1 (FN1), E-Cadherin (CDH1), and N-Cadherin (CDH2) and angiogenesis marker VEGFA. Immunofluorescence assay was done to confirm the presence of C-Peptide, GLUT 2, E-Cadherin and ITGB3. Adhesion was confirmed assessed on fibronectin binding.

KEY FINDINGS

We show that insulin secretion is not hampered under hypoxia. We found an upregulation of glucose transporters under hypoxia indicating enhanced glucose uptake needed to cater to metabolic demands of proliferating cells. Up regulation of adhesion molecules was seen under hypoxia indicative of a favoured environment for retention of cells at the injury site. We also found increased level of angiogenesis of P-MSCs under hypoxia.

SIGNIFICANCE

Our present study thus demonstrates for the first time that P-MSCs modulate themselves under hypoxic conditions by secreting insulin, up regulating glucose transporters and adhesion molecules and eventually exhibiting an increased angiogenic potential. We thus infer that priming P-MSCs under hypoxia, could make them more suitable for wound healing applications.

Cellular bone matrices: viable stem cell-containing bone graft substitutes

BACKGROUND CONTEXT

Advances in the field of stem cell technology have stimulated the development and increased use of allogenic bone grafts containing live mesenchymal stem cells (MSCs), also known as cellular bone matrices (CBMs). It is estimated that CBMs comprise greater than 17% of all bone grafts and bone graft substitutes used.

PURPOSE

To critically evaluate CBMs, specifically their technical specifications, existing published data supporting their use, US Food and Drug Administration (FDA) regulation, cost, potential pitfalls, and other aspects pertaining to their use.

STUDY DESIGN

Areview of literature.

METHODS

A series of Ovid, Medline, and Pubmed-National Library of Medicine/National Institutes of Health (www.ncbi.nlm.nih.gov) searches were performed. Only articles in English journals or published with English language translations were included. Level of evidence of the selected articles was assessed. Specific technical information on each CBM was obtained by direct communication from the companies marketing the individual products.

RESULTS

Five different CBMs are currently available for use in spinal fusion surgery. There is a wide variation between the products with regard to the average donor age at harvest, total cellular concentration, percentage of MSCs, shelf life, and cell viability after defrosting. Three retrospective studies evaluating CBMs and fusion have shown fusion rates ranging from 90.2% to 92.3%, and multiple industry-sponsored trials are underway. No independent studies evaluating spinal fusion rates with the use of CBMs exist. All the commercially available CBMs claim to meet the FDA criteria under Section 361, 21 CFR Part 1271, and are not undergoing FDA premarket review. The CBMs claim to provide viable MSCs and are offered at a premium cost. Numerous challenges exist in regard to MSCs' survival, function, osteoblastic potential, and cytokine production once implanted into the intended host.

CONCLUSIONS

Cellular bone matrices may be a promising bone augmentation technology in spinal fusion surgery. Although CBMs appear to be safe for use as bone graft substitutes, their efficacy in spinal fusion surgery remains highly inconclusive. Large, nonindustry sponsored studies evaluating the efficacy of CBMs are required. Without results from such studies, surgeons must be made aware of the potential pitfalls of CBMs in spinal fusion surgery. With the currently available data, there is insufficient evidence to support the use of CBMs as bone graft substitutes in spinal fusion surgery.

CNN3 regulates trophoblast invasion and is upregulated by hypoxia in BeWo cells

CNN3 is an ubiquitously expressed F-actin binding protein, shown to regulate trophoblast fusion and hence seems to play a role in the placentation process. In this study we demonstrate that CNN3 levels are upregulated under low oxygen conditions in the trophoblast cell line BeWo. Since hypoxia is discussed to be a pro-migratory stimulus for placental cells, we examined if CNN3 is involved in trophoblast invasion. Indeed, when performing a matrigel invasion assay we were able to show that CNN3 promotes BeWo cell invasion. Moreover, CNN3 activates the MAPKs ERK1/2 and p38 in trophoblast cells and interestingly, both kinases are involved in BeWo invasion. However, when we repeated the experiments under hypoxic conditions, CNN3 did neither promote cell invasion nor MAPK activation. These results indicate that CNN3 promotes invasive processes by the stimulation of ERK1/2 and/or p38 under normoxic conditions in BeWo cells, but seems to have different functions at low oxygen levels. We further speculated that CNN3 expression might be altered in human placentas derived from pregnancies complicated by IUGR and preeclampsia, since these placental disorders have been described to go along with impaired trophoblast invasion. Our studies show that, at least in our set of placenta samples, CNN3 expression is neither deregulated in IUGR nor in preeclampsia. In summary, we identified CNN3 as a new pro-invasive protein in trophoblast cells that is induced under low oxygen conditions.

Low-oxygen culture conditions extend the multipotent properties of human retinal progenitor cells

PURPOSE

Development of an effective cell-based therapy is highly dependent upon having a reproducible cell source suitable for transplantation. One potential source, isolated from the developing fetal neural retina, is the human retinal progenitor cell (hRPC). One limiting factor for the use of hRPCs is their in vitro expansion limit. As such, the aim of this study was to determine whether culturing hRPCs under 3% O2 would support their proliferative capacity while maintaining multipotency.

METHODS

To determine the effect of low oxygen on the ability of hRPCs to self-renew, rates of proliferation and apoptosis, telomerase activity, and expression of proliferative, stemness, and differentiation markers were assessed for hRPCs cultured in 3% and 20% oxygen conditions.

RESULTS

Culture under 3% oxygen increases the proliferation rate and shifts the proliferation limit of hRPCs to greater 40 divisions. This increased capacity for proliferation is correlated with an upregulation of Ki67, CyclinD1, and telomerase activity and a decrease in p53 expression and apoptosis. Increased expression of cMyc, Klf4, Oct4, and Sox2 in 3% O₂ is correlated with stabilization of both HIF1α and HIF2α. The eye field development markers Pax6, Sox2, and Otx2 are present in hRPCs up to passage 16 in 3% O₂ . Following in vitro differentiation hRPCs expanded in the 3% O₂ were able to generate specialized retinal cells, including rods and cones.

CONCLUSIONS

Low-oxygen culture conditions act to maintain both multipotency and self-renewal properties of hRPCs in vitro. The extended expansion limits permit the development of a clinical-grade reagent for transplantation.

Synthesis, spectral characterization, and in vitro cellular activities of metapristone, a potential cancer metastatic chemopreventive agent derived from mifepristone (RU486)

Mifepristone (RU486) is marketed and used widely by women as an abortifacient, and experimentally for psychotic depression and anticancer treatments. After administration, metapristone is found to be the most predominant metabolite of mifepristone. We hypothesized that adhesion of circulating tumor cells (CTCs) to vascular endothelial bed is a crucial starting point in metastatic cascade, and that metapristone can serve as a cancer metastatic chemopreventive agent that can interrupt adhesion and invasion of CTCs to the intima of microvasculature. In the present study, we modified the synthesis procedure to produce grams of metapristone, fully characterized its spectral properties and in vitro cellular activities, including its cytostatic effects, cell cycle arrest, mitochondrial membrane potential, and apoptosis on human colorectal cancer HT-29 cells. Metapristone concentration dependently interrupted adhesion of HT-29 cells to endothelial cells. Metapristone may potentially be a useful agent to interrupt metastatic initiation.

Hypoxic conditioned medium from human amniotic fluid-derived mesenchymal stem cells accelerates skin wound healing through TGF-β/SMAD2 and PI3K/Akt pathways

In a previous study, we isolated human amniotic fluid (AF)-derived mesenchymal stem cells (AF-MSCs) and utilized normoxic conditioned medium (AF-MSC-norCM) which has been shown to accelerate cutaneous wound healing. Because hypoxia enhances the wound healing function of mesenchymal stem cell-conditioned medium (MSC-CM), it is interesting to explore the mechanism responsible for the enhancement of wound healing function. In this work, hypoxia not only increased the proliferation of AF-MSCs but also maintained their constitutive characteristics (surface marker expression and differentiation potentials). Notably, more paracrine factors, VEGF and TGF-β1, were secreted into hypoxic conditioned medium from AF-MSCs (AF-MSC-hypoCM) compared to AF-MSC-norCM. Moreover, AF-MSC-hypoCM enhanced the proliferation and migration of human dermal fibroblasts in vitro, and wound closure in a skin injury model, as compared to AF-MSC-norCM. However, the enhancement of migration of fibroblasts accelerated by AF-MSC-hypoCM was inhibited by SB505124 and LY294002, inhibitors of TGF-β/SMAD2 and PI3K/AKT, suggesting that AF-MSC-hypoCM-enhanced wound healing is mediated by the activation of TGF-β/SMAD2 and PI3K/AKT. Therefore, AF-MSC-hypoCM enhances wound healing through the increase of hypoxia-induced paracrine factors via activation of TGF-β/SMAD2 and PI3K/AKT pathways.

αV β5 and CD44 are oxygen-regulated human embryonic stem cell attachment factors

Human embryonic stem cells (hESCs) have great potential for clinical therapeutic use. However, relatively little is known of the mechanisms which dictate their specificity of adhesion to substrates through adhesion proteins including integrins. Previous observations demonstrated enhanced clonogenicity in reduced oxygen culture systems. Here, we demonstrated via antibody blocking experiments that αVβ5 and α6 significantly promoted hESC attachment in 2% O₂ only, whereas blockage of CD44 inhibited cell attachment in 21% O₂ alone. Immunofluorescence confirmed expression of αVβ5 and CD44 in both 2% O₂ and 21% O₂ cultured hESCs while flow cytometry revealed significantly higher αVβ5 expression in 2% O₂ versus 21% O₂ cultured hESCs and higher CD44 expression in 21% O₂ versus 2% O₂ cultured hESCs. Adhered hESCs following blockage of αVβ5 in 2% O₂ displayed a reduction in nuclear colocalisation of Oct-4 and Nanog with little effect observed in 21% O₂. Blockage of CD44 had the converse effect with dramatic reductions in nuclear colocalisation of Oct-4 and Nanog in 21% O₂ cultured hESC which retained adherence, but not in 2% O₂ cultured cells. Identification of oxygen-dependent substrate attachment mechanisms in hESCs has the potential to play a role in the development of novel substrates to improve hESC attachment and culture.

Effects of hypoxia on human cancer cell line chemosensitivity

Background

Environment inside even a small tumor is characterized by total (anoxia) or partial oxygen deprivation, (hypoxia). It has been shown that radiotherapy and some conventional chemotherapies may be less effective in hypoxia, and therefore it is important to investigate how different drugs act in different microenvironments. In this study we perform a large screening of the effects of 19 clinically used or experimental chemotherapeutic drugs on five different cell lines in conditions of normoxia, hypoxia and anoxia.

Methods

A panel of 19 commercially available drugs: 5-fluorouracil, acriflavine, bortezomib, cisplatin, digitoxin, digoxin, docetaxel, doxorubicin, etoposide, gemcitabine, irinotecan, melphalan, mitomycin c, rapamycin, sorafenib, thalidomide, tirapazamine, topotecan and vincristine were tested for cytotoxic activity on the cancer cell lines A2780 (ovarian), ACHN (renal), MCF-7 (breast), H69 (SCLC) and U-937 (lymphoma). Parallel aliquots of the cells were grown at different oxygen pressures and after 72 hours of drug exposure viability was measured with the fluorometric microculture cytotoxicity assay (FMCA).

Results

Sorafenib, irinotecan and docetaxel were in general more effective in an oxygenated environment, while cisplatin, mitomycin c and tirapazamine were more effective in a low oxygen environment. Surprisingly, hypoxia in H69 and MCF-7 cells mostly rendered higher drug sensitivity. In contrast ACHN appeared more sensitive to hypoxia, giving slower proliferating cells, and consequently, was more resistant to most drugs.

Conclusions

A panel of standard cytotoxic agents was tested against five different human cancer cell lines cultivated at normoxic, hypoxic and anoxic conditions. Results show that impaired chemosensitivity is not universal, in contrast different cell lines behave different and some drugs appear even less effective in normoxia than hypoxia.

A Prominin-1-Rich Pediatric Glioblastoma: Biologic Behavior Is Determined by Oxygen Tension-Modulated CD133 Expression but Not Accompanied by Underlying Molecular Profiles

Few studies on the biologic and molecular properties of pediatric glioblastoma have been performed. Until now, differential genomic analysis of CD133(+)ve and CD133(-)ve fractions has not been described in pediatric glioma. We hypothesize not only that the presence of CD133 could be the source of tumor resistance but also that maintenance of this molecule by hypoxia dictates cellular and molecular behavior. From a series of human glioblastoma biopsies investigated, only one, IN699 (from a pediatric glioblastoma), generated greater than 4% of the total cell volume as CD133(+)ve cells. Using this pediatric glioblastoma, containing unprecedented high levels of the putative brain tumor stem cell marker CD133, as a study model, we report biologic and molecular characteristics of the parent culture and of CD133(+)ve and CD133(-)ve populations derived therefrom under atmospheric and hypoxic culture conditions. Immunocytochemistry and flow cytometry were performed with antigenic markers known to characterize neural stem cells and associated glioma behavior. Behavioral analysis was carried out using proliferation, adhesion, migration, and invasion assays. Cell cycle analysis and array comparative genomic hybridization were used to assess copy number profiles for parental cells and CD133(+)ve and CD133(-)ve fractions, respectively. With regard to invasion and proliferation, CD133(+)ve and CD133(-)ve fractions were inversely proportional, with a significant increase in invasive propensity within the CD133(-)ve cells (P < .005) and a significant increase in proliferation within CD133(+)ve cells (P < .005). Our observations indicate identical genomic imbalances between CD133(+)ve and CD133(-)ve fractions. Furthermore, our research documents a direct link between decreasing oxygen tension and CD133 expression.

Hypoxic tumor microenvironments reduce collagen I fiber density

Although the mechanisms through which hypoxia influences several phenotypic characteristics such as angiogenesis, selection for resistance to apoptosis, resistance to radiation and chemotherapy, and increased invasion and metastasis are well characterized, the relationship between tumor hypoxia and components of the extracellular matrix (ECM) is relatively unexplored. The collagen I (Col1) fiber matrix of solid tumors is the major structural part of the ECM. Col1 fiber density can increase tumor initiation, progression, and metastasis, with cancer cell invasion occurring along radially aligned Col1 fibers. Here we have investigated the influence of hypoxia on Col1 fiber density in solid breast and prostate tumor models. Second harmonic generation (SHG) microscopy was used to detect differences in Col1 fiber density and volume between hypoxic and normoxic tumor regions. Hypoxic regions were detected by fluorescence microscopy, using tumors derived from human breast and prostate cancer cell lines stably expressing enhanced green fluorescent protein (EGFP) under transcriptional control of the hypoxia response element. In-house fiber analysis software was used to quantitatively analyze Col1 fiber density and volume from the SHG microscopy images. Normoxic tumor regions exhibited a dense mesh of Col1 fibers. In contrast, fewer and structurally altered Col1 fibers were detected in hypoxic EGFP-expressing tumor regions. Microarray gene expression analyses identified increased expression of lysyl oxidase and reduced expression of some matrix metalloproteases in hypoxic compared with normoxic cancer cells. These results suggest that hypoxia mediates Col1 fiber restructuring in tumors, which may impact delivery of macromolecular agents as well as dissemination of cells.

Hypoxic tumors and their effect on immune cells and cancer therapy

The abnormal decrease or the lack of oxygen supply to cells and tissues is called hypoxia. This condition is commonly seen in various diseases such as rheumatoid arthritis and atherosclerosis, also in solid cancers. Pre-clinical and clinical studies have shown that hypoxic cancers are extremely aggressive, resistant to standard therapies (chemotherapy and radiotherapy), and thus very difficult to eradicate. Hypoxia affects both the tumor and the immune cells via various pathways. This review summarizes the most common effects of hypoxia on immune cells that play a key role in the anti-tumor response, the limitation of current therapies, and the potential solutions that were developed for hypoxic malignancies.

Hypoxia and Ionizing Radiation: Changes in Adhesive Properties and Cell Adhesion Molecule Expression in MG-63 Three-Dimensional Tumor Spheroids

The effects of chemically induced hypoxia and ionizing radiation on the adhesive properties of MG-63 human osteosarcoma three-dimensional spheroids were investigated. Hypoxia was induced by addition of CoCl2 to small, nonhypoxic spheroids and verified by HIF-1alpha expression. In addition, the possible role of important cell adhesion molecules involved in tumor dissemination in inducing adhesive changes were also studied. In particular, two key integrins (i.e., the alpha chain of the fibronectin receptor, alpha5, and the alpha chain of the collagen receptor, alpha2), an important member of the immunoglobulin superfamily (CD54 or ICAM-1) and the strategic molecule CD44 (H-CAM, the principal receptor for hyaluronan) were examined. Because of the important role of fibronectin in adhesive processes, variations in this extracellular matrix component were also examined. The results seem to indicate that CoCl2-induced hypoxia greatly increases adhesion of MG-63 spheroids to both tissue culture plates and plates coated with fibronectin or collagen when compared to controls, while ionizing radiation induces a great decrease in this attachment. Furthermore, chemically induced hypoxia also partially inhibits the effects of ionizing radiation. The data also show that these adhesive changes are accompanied by concomitant variations in the expression of alpha5 and alpha2 integrins, CD44, and CD54 and fibronectin.

Extracellular matrix-dependent regulation of angiogenin expression in human placenta

Knowledge of the rapidly developing hierarchy of controls affecting vascular development in placenta is required to understand how the growth factors and their receptor-mediated signals actually produce vessels. At the cell biological level, these events clearly require stable interactions between the cells, and cells with the surrounding ECM. The objective of the study was to understand the role of integrins and ECM on the expression and secretion of angiogenin in placentas and from trophoblasts in culture. Functionally active term placental explant culture and trophoblast cultures were used to demonstrate the differential secretion profile of angiogenin and real-time quantitative RT-PCR to demonstrate the mRNA expression in the presence or absence of ECM proteins. In this study, a significant increase in expression and secretion of angiogenin occurred in the presence of vitronectin (VN) and fibronectin (FN). Using antibody-blocking experiments it was also demonstrated that the angiogenin secretion is mediated by placental integrins, alpha(V)beta3 and alpha5beta1. In addition, exposure to hypoxic conditions resulted in diminished angiogenin secretion in the presence of both ECMs suggesting that angiogenin expression in the presence of ECM is modulated by local O2 concentration. In conclusion, this study provides evidence for the regulatory role of ECM and integrins on the mRNA expression and secretion of angiogenin in human placenta. ECMs may have a pivotal role in enhancing secretion of this peptide necessary for placental angiogenesis and provides the impetus as additional targets for the control of angiogenesis in pathological pregnancy.

Review: implications of in vitro research on the effect of radiotherapy and chemotherapy under hypoxic conditions

As it is now well established that human solid tumors frequently contain a substantial fraction of cells that are hypoxic, more and more in vitro research is focusing on the impact of hypoxia on the outcome of radiotherapy and chemotherapy. Indeed, the efficacy of irradiation and many cytotoxic drugs relies on an adequate oxygen supply. Consequently, hypoxic regions in solid tumors often contain viable cells that are intrinsically more resistant to treatment with radiotherapy or chemotherapy. Moreover, efforts have been made to exploit hypoxia as a potential difference between malignant and normal tissues.Nowadays, a body of evidence indicates that oxygen deficiency clearly influences some major intracellular pathways such as those involved in cell proliferation, cell cycle progression, apoptosis, cell adhesion, and others. Obviously, when investigating the effects of radiotherapy or chemotherapy or both combined under hypoxic conditions, it is essential to consider the influences of hypoxia itself on the cell. In this review, we first focus on the effects of hypoxia per se on some critical biological pathways. Next, we sketch an overview of preclinical and clinical research on radiotherapy, chemotherapy, and chemoradiation under hypoxic conditions.

Effects of hypoxia on human mesenchymal stem cell expansion and plasticity in 3D constructs

Low oxygen tension is thought to be an integral component of the human mesenchymal stem cell (hMSC) native bone marrow microenvironment. HMSC were cultured under physiologically relevant oxygen environments (2% O2) in three-dimensional (3D) constructs for up to 1 month in order to investigate the combined effects of chronic hypoxia and 3D architecture on hMSC tissue-development patterns. Hypoxic hMSC exhibited an extended lag phase in order to acclimatize to culture conditions. However, they subsequently proliferated continuously throughout the culture period, while maintaining significantly higher colony-forming unit capabilities and expressing higher levels of stem cell genes than hMSC cultured at 20% O2 (normoxic) conditions. Upon induction, hypoxic hMSC also expressed higher levels of osteoblastic and adipocytic differentiation markers than normoxic controls. Hypoxia induced increased total protein levels in hMSC throughout the culture period, as well as significantly different fibronectin expression patterns suggesting that oxygen levels can significantly affect tissue-development patterns. Importantly, hMSC maintained the ability to thrive in prolonged hypoxic conditions suggesting that hypoxia may be an essential element of the in vivo hMSC niche. Further studies are required to determine how variations in cellular characteristics and ECM expression impact on the physiological properties of the engineered tissue, yet these results strongly indicate that oxygen tension is a key parameter that influences the in vitro characteristics of hMSC and their development into tissues.

Low Oxygen Concentrations Inhibit Trophoblast Cell Invasion from Early Gestation Placental Explants via Alterations in Levels of the Urokinase Plasminogen Activator System1

Extravillous trophoblast cell (EVT) invasion in early pregnancy occurs in a relatively low-oxygen environment. The role of oxygen in regulation of EVT invasion remains controversial. We hypothesized that 1) culture in 3% oxygen inhibits EVT invasion compared with culture at 8% or 20% oxygen and 2) inhibition of invasion is due to alterations in levels of components of the urokinase plasminogen activator (PLAU, uPA) system rather than through increased apoptosis and/or decreased proliferation. Placental samples (8-10, 12-14, and 16-20 wk gestation) were obtained from women undergoing elective surgical termination of pregnancy or after cesarean section delivery (term) at the Royal Victoria Infirmary, Newcastle upon Tyne, U.K. EVT invasion from placental explants cultured at 3%, 8%, or 20% oxygen was assessed using Matrigel invasion assays. Invasion was assessed on Day 6, explants were harvested for analysis of apoptosis and proliferation, and medium was stored for analysis of PLAU system components by ELISA and casein zymography. Culture at 3% oxygen inhibited EVT invasion. PLAU receptor and plasminogen activator inhibitor-2 protein levels were increased and PLAU activity decreased in these cultures. There was no difference in the proliferation in explants cultured at the three different oxygen concentrations. Apoptosis, assessed by M30 immunostaining, was increased in EVT at both 3% and 8% oxygen. The reduction in the invasive capacity of EVT cultured at 3% oxygen appears to be mediated both by a general inhibition of the PLAU system and a decrease in the number of cells available to invade.

The regulation of trophoblast differentiation by oxygen in the first trimester of pregnancy

In the first trimester of human pregnancy villous cytotrophoblasts are able to differentiate to form either the overlying syncytiotrophoblast layer or, in anchoring villi, extravillous trophoblasts which grow out from the villi and invade into the maternal decidua, acting to both physically attach the placenta to the decidua, and modify the maternal spiral arteries to sustain pregnancy. During the first 10-12 weeks of gestation, extravillous trophoblast plugs block the spiral arteries and prevent maternal blood flow entering the intervillous space, thereby creating an environment of physiological hypoxia in which placental and fetal development occur. As extravillous trophoblasts migrate away from the villus they differentiate from a proliferative to an invasive phenotype. The hypoxic environment of the first trimester is believed to play an important role in the regulation of trophoblast differentiation. However, there is currently a large body of conflicting experimental evidence concerning this topic. This review examines the experimental evidence to date on the role of oxygen in trophoblast differentiation.

Effects of mifepristone on invasive and metastatic potential of human gastric adenocarcinoma cell line MKN-45 in vitro and in vivo

AIM: To investigate the effects of mifepristone on the invasive and metastatic potential of human gastric adenocarcinoma cell line MKN-45 and its mechanisms.

METHODS: After incubation with various concentrations of mifepristone (5, 10, 20 μmol/L), the adhesion to artificial basement membrane, Matrigel, and the migration of MKN-45 cells were assayed using MTT assay and Transwell cell culture chambers, respectively. Enzyme- linked immunoabsorbent assay (ELISA) and flow cytometry were used to determine the expression of vascular endothelial growth factor (VEGF) and integrin β3 in the cells. After subcutaneous transplantation of MKN-45 cells in nude mice, mifepristone (50 mg/kg·d) was administrated subcutaneously for 8 wk to assess its effects on tumor metastasis. Immunohistochemical analysis was used to detect the expression of VEGF and microvascular density (MVD) in xenografted tumors.

RESULTS: Mifepristone dose-dependently inhibited the heterotypic adhesion to Matrigel of MKN-45 cells. The inhibition was accompanied by a significant down-regulation of integrin β3 expression in the cells. After incubation with 5, 10, 20 μmol/L mifepristone, the number of migrated MKN-45 cells was 72 ± 8, 50 ± 6, 41 ± 5 in experiment group, and 94 ± 16 in control group (P < 0.01). Meanwhile, secreted VEGF protein of MKN-45 cells in mifepristone-treated group (14.2 ± 2.9, 8.9 ± 3.1, 5.4 ± 2.1 ng/g per liter) was significantly lower than that in control group (22.7 ± 4.3 ng/g per liter, P < 0.01). In vivo, mifepristone decreased the number of metastatic foci in lungs of nude mice and down-regulated the expression of VEGF and MVD in the xenograted tumors.

CONCLUSION: Mifepristone can effectively inhibit the invasive and metastatic potential of human gastric adenocarcinoma cell line MKN-45 in vitro and in vivo through inhibition of heterotypic adhesion to basement membrane, cell migration and angiogenesis.

Interaction of cocultured decidual endothelial cells and cytotrophoblasts in preeclampsia

Disturbed cell-cell communication between trophoblasts and the maternal endothelium may be responsible for the deficient endovascular invasion seen in preeclampsia. In vitro studies have been hampered by lack of suitable models to directly examine interactions between these cell types. Using a bilayer coculture model, we examined the effect of decidual endothelial cells on matrix metalloproteinase secretion and the migration of cytotrophoblasts from preeclamptic pregnancies. Cells were incubated on semipermeable membranes in 20% or 2% O(2) with or without the tumor promoter phorbol 12-myristate 13-acetate, which activates matrix metalloproteinase-2 and -9 in endothelial cells. Cytotrophoblasts from preeclamptic pregnancies secreted significantly less matrix metalloproteinase-2 and -9 than their normal counterparts. Although decidual endothelial cells downregulated cytotrophoblast migration in normal pregnancy, this was not observed in cocultures with cytotrophoblasts from preeclamptic pregnancies. In addition, cytotrophoblasts from preeclamptic pregnancies altered phorbol myristate acetate-induced activation of endothelial matrix metalloproteinases. Hypoxia increased cytotrophoblast migration when cells were incubated alone but not in coculture with decidual endothelial cells due to increased adhesion between the two cell types. These results suggest dysfunctional interactive regulation of migration and matrix metalloproteinase secretion in preeclampsia that could result in abnormal endovascular trophoblast invasion of the maternal vasculature.

Inhibition of breast carcinoma and trophoblast cell invasiveness by vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen and angiogenic growth factor that enhances endothelial cell invasion through the extracellular matrix (ECM). While various cell types express VEGF receptors, little is known about the biological actions of VEGF on nonendothelial cells. Therefore, the main objective of the present study was to determine the effect of VEGF on the in vitro invasiveness and proliferation of human MDA-MB-231 breast carcinoma cells and human HTR-8/SVneo trophoblast cells. Reverse-transcriptase polymerase chain reaction analysis demonstrated the presence of transcripts encoding VEGF receptors (VEGFR) -1, -2, and -3 as well as neuropilins-1 and -2 in the trophoblast cells, and the presence of transcripts encoding VEGFR-2 and neuropilins-1 and -2 in the breast carcinoma cells. Both cell lines also expressed transcripts for VEGF-A, -B, -C and -D, as well as for placenta growth factor (PlGF). Although incubation with exogenous VEGF-A(165) or VEGF-A(121) did not affect the rate of proliferation of either the trophoblast or the breast carcinoma cells, incubation with these molecules reduced their ability to invade through reconstituted ECM (Matrigel). The effect of VEGF-A(165) on the invasiveness of both cell lines was inhibited by the inclusion of a neutralizing antibody to VEGF. Exogenous VEGF-A(165) also decreased the cell surface expression of the urokinase-type plasminogen activator (a molecule required for invasion) by the breast carcinoma and trophoblast cells. These results indicate that the biological actions of VEGF on certain cell types may differ from the effects of this molecule on vascular endothelial cells, and therefore are relevant to angiogenesis-based therapies.

Possible physiological role of H19 RNA

The product of the imprinted oncofetal H19 gene is an untranslated RNA of unknown function. With the human cDNA Atlas microarray, we detected differentially expressed genes modulated by the presence of H19 RNA. Many of the genes that are upregulated by H19 RNA are known to contribute to the invasive, migratory, and angiogenic capacities of cells. Moreover, we provided experimental data indicating that whereas H19 RNA did not have any growth advantage for the cells when cultured in 10% fetal calf serum, it did confer an advantage when cells were cultured in serum-poor medium. This observation can be explained in part by the inability of the H19-expressing cells to induce the cyclin-dependent kinase inhibitor p57(kip2) in response to serum stress. Our results favor the possible role of the H19 gene in promoting cancer progression, angiogenesis, and metastasis.

Calpain is required for MMP-2 and u-PA expression in SV40 large T-antigen-immortalized cells

The absence of both mu- and m-calpain activity, caused by disruption of the capn4 gene in mice, retarded migration, and disrupted the cytoskeleton, both in primary capn4(-/-) embryonic fibroblasts (mEF) and in capn4(-/-) mEF immortalized with SV40 large T-antigen (TAg). These results are thought to reflect the role of calpain in integrin signaling to the cytoskeleton. The integrins are also involved, together with matrix metalloproteinases (MMP) and plasminogen activators (PA), in cellular invasion. This study therefore aimed to establish whether links exist between the calpain, MMP, and PA systems, using both primary and TAg-immortalized capn4(+/+) and capn4(-/-) embryonic fibroblasts. Both Matrigel invasion, and expression of MMP-2 and u-PA activities, correlated with calpain expression in TAg-containing cells, but not in primary cells. MMP-2 mRNA synthesis also correlated with calpain expression in the presence of TAg, but u-PA mRNA synthesis was not so correlated. The results suggest that calpain acquires new regulatory roles in the presence of TAg. Calpain is also required for v-Src-mediated transformation. It appears that calpain may have previously unsuspected roles in oncogenic transformation.