A comparative study on the effects of tumor necrosis factor-alpha (TNF-alpha), human angiogenic factor (h-AF) and basic fibroblast growth factor (bFGF) on the chorioallantoic membrane of the chick embryo

Tumor Necrosis Factor Alpha Signaling and Organogenesis

Tumor necrosis factor alpha (TNF-α) plays important roles in processes such as immunomodulation, fever, inflammatory response, inhibition of tumor formation, and inhibition of viral replication. TNF-α and its receptors are ubiquitously expressed in developing organs and they regulate the survival, proliferation, and apoptosis of embryonic stem cells (ESCs) and progenitor cells. TNF-α is an important inflammatory factor that also regulates the inflammatory response during organogenesis, and its cytotoxic effects can interfere with normal developmental processes, even leading to the onset of diseases. This review summarizes the various roles of TNF-α in organogenesis in terms of its secreting pattern, concentration-dependent activities, and interactions with other signaling pathways. We also explored new potential functions of TNF-α.

Chorioallantoic Membrane Models of Various Avian Species: Differences and Applications

The chorioallantoic membrane model (CAM) of an avian embryo is used as an experimental model in various fields of research, including angiogenesis research and drug testing, xenografting and cancer research, and other scientific and commercial disciplines in microbiology, biochemistry, cosmetics, etc. It is a low-cost, low-maintenance, and well-available in vivo animal model that is non-sentient and can be used as an alternative for other mammal experimental models. It respects the principles of the "3R" rule (Replacement, Reduction, and Refinement)-conditions set out for scientific community providing an essential framework for conducting a more human animal research, which is also in line with constantly raising public awareness of welfare and the ethics related to the use of animal experimental models. In this review, we describe the chorioallantoic membrane of an avian embryo, focusing on its properties and development, its advantages and disadvantages as an experimental model, and the possibilities of its application in various fields of biological research. Since the most common chicken CAM model is already well known and described in many publications, we are particularly focusing on the advantages and application of less known avian species that are used for the CAM model-quail, turkey, and duck.

An ex vivo model for anti-angiogenic drug testing on intact microvascular networks

New models of angiogenesis that mimic the complexity of real microvascular networks are needed. Recently, our laboratory demonstrated that cultured rat mesentery tissues contain viable microvascular networks and could be used to probe pericyte-endothelial cell interactions. The objective of this study was to demonstrate the efficacy of the rat mesentery culture model for anti-angiogenic drug testing by time-lapse quantification of network growth. Mesenteric windows were harvested from adult rats, secured in place with an insert, and cultured for 3 days according to 3 experimental groups: 1) 10% serum (angiogenesis control), 2) 10% serum + sunitinib (SU11248), and 3) 10% serum + bevacizumab. Labeling with FITC conjugated BSI-lectin on Day 0 and 3 identified endothelial cells along blood and lymphatic microvascular networks. Comparison between day 0 (before) and 3 (after) in networks stimulated by 10% serum demonstrated a dramatic increase in vascular density and capillary sprouting. Growing networks contained proliferating endothelial cells and NG2+ vascular pericytes. Media supplementation with sunitinib (SU11248) or bevacizumab both inhibited the network angiogenic responses. The comparison of the same networks before and after treatment enabled the identification of tissue specific responses. Our results establish, for the first time, the ability to evaluate an anti-angiogenic drug based on time-lapse imaging on an intact microvascular network in an ex vivo scenario.

A novel four-step system for screening angiogenesis inhibitors

Angiogenesis exhibits a significant effect on tumor progression. Inhibiting angiogenesis may provide significant advantages over currently available therapeutics for cancer therapies thus, the development of a system of screening angiogenesis is essential. In the present study, a novel available system of screening angiogenesis inhibitors by four steps was developed. The chorioallantoic membrane (CAM), yolk sac membrane and early chick embryo blood island assay were initially performed to obtain possible antitumor compounds. The MMTV‑PyMT transgenic breast cancer mouse model was used for final screening and to confirm potential antitumor effects. Four angiogenesis inhibitors were isolated from 480 compounds, which were obtained from ICCB known bioactives library, by a combination of the CAM, yolk sac membrane and early chick embryo blood island assay. The MMTV‑PyMT mouse was treated with one of four agents and it was demonstrated that the tumor volume was significantly inhibited. These results demonstrate that the four‑step screening system is feasible.

[Vascularization of the head and neck during development]

One of the earliest priorities of the embryonic vascular system is to ensure the metabolic needs of the head. This review covers some of the principles that govern the cellular assembly and localization of blood vessels in the head. In order to understand the development and organization of the cephalic vascular tree, one needs to recall the morphogenetic movements underlying vertebrate head formation and giving rise to the constituent cells of the vascular system. Some of the major signaling molecules involved in vascular development are discussed, including the angiopoietins, the endothelins, the FGFs, the Notch receptors, the PDGFs, Sonic hedgehog, the TGF family and the VEGFs, in order to underline similarities between embryonic and postnatal vascular development, even in the context of increasingly divergent form.

Toxicological overview of cigarette smoking on angiogenesis

Angiogenesis is the process of generating new capillary blood vessels. It occurs under tight regulation in the female reproductive system, during wound healing and during embryogenesis. Angiogenesis also plays an important role in the pregnancy-associated changes in the reproductive tract. Cigarette smoke inhibits processes that may hinder normal process of angiogenesis resulting in abnormal blood supply to tissues, decreased repair and remodeling. This report summarizes the evidences of the causal association between tobacco smoking and disruption of angiogenesis. Application of small amount of nicotine on day 5 old chorioallantoic membranes (CAMs) did not disrupt the process of angiogenesis, while application of mainstream smokes (MSS) solutions to CAMs caused varying levels of disruption on normal process of angiogenesis and adversely affect capillary plexus formation, diameters of secondary and tertiary vessels. We have also observed that at equivalent doses, sidestream smoke (SSS) can significantly be more potent than MSS and can alter the normal process of angiogenesis more drastically than MSS. It suggests that SSS either contains a toxicant(s) not present in MSS or that the toxicant(s) that produces these effects is present in higher concentration in SSS than in MSS. Therefore, it is undisputed that smoking can interfere the normal process of angiogenesis, which is a vital process to maintain pregnancy and development of fetus. Smoking during pregnancy is harmful to fetal development and is associated with an increased risk of miscarriage, perinatal death and sudden infant death syndrome. Smoking-cessation programs remain a crucial strategy for preventing poor birth outcomes and decreasing the social and financial costs of smoking during pregnancy.

Effects of retinoic acid steroidal analogs on human leukemic HL60 cell proliferation in vitro and on angiogenesis in vivo

Retinoic acid (RA) can be regarded as a pharmacological agent commonly used for its ability to affect growth and differentiation of a variety of cell types, such as acute promyelocytic leukemic and endothelial cells. In the present work we studied the effect of all-trans-RA (ATRA) and its steroidal analogs EA-4, EA-136 and EA-137 on the growth of human promyelocytic HL-60 cells in vitro. The specific steroidal substrates were chosen in order to further investigate their ability to improve the pharmacological properties of conjugated antileukemic agents. ATRA decreased the number of HL60 cells from the first 24 h after its addition to the cell culture medium. The decrease was significant at concentrations higher than 10(-5) M. All the analogs tested also decreased the number of HL60 cells with an IC50 similar to that of ATRA, except for EA-4 whose IC50 was almost two orders of magnitude lower than that of ATRA, 72 h after its addition to the cell culture medium. Since angiogenesis is important for the growth of hematological malignancies, we furthermore studied the effect of ATRA and its analogs on the formation of new capillaries in the in vivo chicken embryo chorioallantoic membrane (CAM). ATRA, EA-136 and EA-137 induced angiogenesis in the CAM, increased the layer of CAM keratinocytes, and resulted in a significant degree of extravasation. EA-4 had no effect on either angiogenesis or tissue structure in general. It seems that the retinoid EA-4 is a promising agent for the inhibition of human leukemia cell growth.

Quantification of anti-angiogenesis using the capillaries of the chick chorioallantoic membrane demonstrates that the effect of human angiostatin is age-dependent

We present a method whereby en face estimation of the chorionic capillary plexus can be generated in the living chick chorioallantoic membrane (CAM) and confirmed by post-fixation cross section analysis. This value does not alter significantly with age and provides a reliable and simple method to evaluate anti-angiogenesis. Anti-angiogenesis may be induced by an intervention, such as a pharmacological agent, applied to the surface of the CAM. We describe the use of silastic rings that are associated with minimal inflammatory reaction, in this process. By estimating changes in the chorionic capillary plexus to quantify anti-angiogenesis, together with silastic rings, we examined the anti-angiogenic effect of human angiostatin and demonstrated that although there is a significant loss of capillaries en face after exposure from days 7 to 9 of incubation, in contrast there is no significant inhibition after exposure to a similar dose of angiostatin from days 11 to 13 of incubation. This not only demonstrates the important effects on neo-angiogenesis compared to mature vessels, but also illustrates the potential of the CAM to readily provide a means for such a comparison.

The antimycotic ciclopirox olamine induces HIF-1alpha stability, VEGF expression, and angiogenesis

The heterodimeric hypoxia-inducible factor (HIF)-1 is a master regulator of oxygen homeostasis. Protein stability and transactivation function of the alpha subunit are controlled by iron- and oxygen-dependent hydroxylation of proline and asparagine residues. The anti-mycotic ciclopirox olamine (CPX) is a lipophilic bidentate iron chelator that stabilizes HIF-1alpha under normoxic conditions at lower concentrations than other iron chelators, probably by inhibiting HIF-1alpha hydroxylation. As shown by the inhibition of iron-dependent quenching of FITC-labeled deferoxamine (DFX) fluorescence, CPX appears to have an even higher affinity for iron than DFX. Initial observations that treatment with 1% CPX, but not with placebo, occasionally caused reddening of wound margins in a mouse skin wound model prompted us to investigate the capability of CPX to induce angiogenesis. CPX-induced HIF-1-mediated reporter gene activity and endogenous HIF-1 target gene expression, including elevation of transcription, mRNA, and protein levels of the vascular endothelial growth factor (VEGF). In the chick chorioallantoic membrane assay, inert polymer disks containing CPX but not the solvent alone induced angiogenesis. In summary, these results suggest that CPX induces angiogenesis in vivo via HIF-1 and VEGF induction. Therefore, CPX might serve as an alternative to recombinant VEGF treatment or to VEGF gene therapy for therapeutic angiogenesis.

A novel early chorioallantoic membrane assay demonstrates quantitative and qualitative changes caused by antiangiogenic substances

The chicken chorioallantoic membrane (CAM) has been extensively used in the study of angiogenesis. However, the CAM assay can be difficult and time-consuming to quantify, provides poor quality images of the results, and is not very reproducible. In this study, a novel early CAM assay was developed: It was found to be quantitative through relatively simple methods, enabled high-quality imaging of results, and was reproducible. Additionally, unique qualitative changes in vessel structure were observed, and it was possible to measure veins and arteries separately. Treatment of the CAM on days 4 and 5 with SU5614, suramin, fumagillin, amiloride, and PI-88 reduced blood-vessel growth. SU5614 (4 microg) resulted in significant reductions in artery but not vein length (60% and 111%, respectively, vs control). Suramin tended to increase CAM vasculature at 50 microg but caused dramatic reductions both in vessel length and CAM growth at 100 microg. As with SU5614, the effect was greater with regard to arterial compared with venous length (49% and 74%, respectively, vs control). PI-88 (20 microg) also decreased artery and vein length (66% and 80%, respectively, vs control). In contrast, fumagillin (5 microg) and amiloride (20 microg) both reduced arterial growth slightly less than venous growth (67% and 54% and 50% and 44%, respectively, vs control). Each antiangiogenic substance caused a different qualitative pattern of change in vessel branching and structure. The early CAM assay will be useful in the screening of antiangiogenic substances. Further study of the qualitative effects of antiangiogenic treatments may be a valuable tool to increase our understanding of the angiogenic process itself.

The human melanoma associated protein melanotransferrin promotes endothelial cell migration and angiogenesis in vivo

Melanotransferrin is a member of the transferrin family, which is comprised of serum transferrin, lactoferrin and ovotransferrin, and is highly expressed on melanoma cells compared to normal melanocytes. Since melanoma is an highly vascularized tumour that expresses melanotransferrin at high levels, we tested purified recombinant melanotransferrin for its capability to induce angiogenesis in the chick chorioallantoic membrane. Macroscopic and microscopic evaluation of the vascular density demonstrated that melanotransferrin exerts an angiogenic response quantitatively similar to that elicited by fibroblast growth factor-2. Overexpression of vascular endothelial growth factor-receptor-2 was observed in newly formed vessels, suggesting that the angiogenic activity of melanotransferrin may depend on activation of endogenous vascular endothelial growth factor. In addition, when antibodies against vascular endothelial growth factor were included in the assay, the angiogenic response was inhibited by 50%. In a Boyden chamber assay purified recombinant melanotransferrin induced chemotactic migration of vascular cells, which was decreased in the the presence of anti-vascular endothelial growth factor antibodies suggesting an involvement of vascular endothelial growth factor present in endothelial cells also in this assay. However, melanotransferrin was found not to directly bind to integrin alphavbeta3 or the vascular endothelial growth factor-receptor-2 as assessed in a BlAcore assay. A possible correlation between vascularization occurring during melanoma progression and the expression of melanotransferrin and vascular endothelial growth factor was established by immunolocalization of the two factors in sections of melanoma at different clinical steps of melanoma progression. These latter data strongly imply that melanotransferrin may participate in the vascularization of solid tumours and that inhibition of melanotransferrin could form the basis for intervention in tumours which use this pathway.

Chorioallantoic membrane capillary bed: a useful target for studying angiogenesis and anti-angiogenesis in vivo

The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane that is commonly used in vivo to study both angiogenesis and anti-angiogenesis. This review 1) summarizes the current knowledge about the structure of the CAM's capillary bed; 2) discusses the controversy about the existence of a single blood sinus or a capillary plexus underlying the chorionic epithelium; 3) describes a new model of the CAM vascular growth, namely the intussusceptive mode; 4) reports findings regarding the role played by endogenous fibroblast growth factor-2 in CAM vascularization; and 5) addresses the use and limitations of the CAM as a model for studying angiogenesis and anti-angiogenesis.

TNP-470 and recombinant human interferon-alpha2a inhibit angiogenesis synergistically

The hypothesis that the combination of two known antiangiogenic agents TNP-470 and interferon (IFN)-alpha exerts synergistic effects has been investigated in vitro and in vivo. In vitro, TNP-470 and recombinant human IFN-alpha2a (rhIFN-alpha2a) resulted in a dose-dependent inhibition of proliferation of human umbilical vein endothelial cells (HUVECs) and EA.hy926 endothelial cells. Compared with the two agents used singly at their lowest or ineffective doses, combined treatment with the same doses inhibited more intensely in the absence of cytotoxicity and displayed similar behaviour on cell chemotaxis and capillary morphogenesis on Matrigel. However, the secretion of matrix metalloproteinase 2 (MMP-2) and MMP-9 was not influenced by the two agents, either alone or in combination, even when they were applied at their lowest efficacious doses or at higher cytotoxic doses. Experiments in vivo with the chick embryo chorioallantoic membrane (CAM)-sponge assay revealed the same dose-dependent inhibition and synergy. As the basic fibroblast growth factor (bFGF)-induced angiogenesis in the CAM-sponge model was strongly inhibited by the combined treatment, TNP-470 and rhIFN-alpha2a would appear to exert antiangiogenesis synergistically, perhaps by interfering with the bFGF-mediated pathway.

Osteogenic protein-1, a bone morphogenetic protein, induces angiogenesis in the chick chorioallantoic membrane and synergizes with basic fibroblast growth factor and transforming growth factor-beta1

Capillary invasion is a vital regulatory signal during bone morphogenesis that is influenced by angiogenic molecules such as fibroblast growth factor (FGF) and some members of the transforming growth factor-beta (TGF-beta) superfamily, including TGF-betas themselves. Bone morphogenetic proteins (BMPs), which are members of the TGF-beta superfamily, have previously not been shown to possess direct angiogenic properties. Osteogenic protein-1 (OP-1; BMP-7) is a potent regulator of cartilage and bone differentiation in vivo. The osteogenic and angiogenic properties of OP-1 at both ortho- and heterotopic sites in adult chacma baboons (Papio ursinus) are enhanced synergistically by the simultaneous application of relatively low doses of TGF-beta1. The single application of relatively high doses of TGF-beta1 (20 ng), and bFGF (500 ng) or relatively low (100 ng) and high (1,000 ng) doses of OP-1 in the chick chorioallantoic membrane (CAM) assay elicited a prominent and (for OP-1) dose-dependent angiogenic response. The binary application of a relatively low dose of OP-1 (100 ng) with a relatively low dose of bFGF (100 ng) or with a relatively low (5 ng) or high (20 ng) dose of TGF-beta1 resulted in a synergistic enhancement of the angiogenic response. The angiogenic effect of the relatively low doses of the combined morphogens was distinctly more pronounced than that of the single application of the relatively high doses of the respective factors. The present findings suggest that these morphogens may be deployed in binary combination in order to accentuate experimental angiogenesis. The cooperative interaction of the different morphogens in the CAM assay may provide important biological clues towards the control of clinical angiogenesis.

Histology and ultrastructure of the chorioallantoic membrane of the mallard duck (Anas platyrhynchos)

The histology and fine structure of the chorioallantoic membrane of the mallard duck (Anas platyrhynchos), and the density of vessels per millimeter of membrane were assessed between days 12 and 24 of incubation. Light and transmission electron microscopy of the chorioallantoic membrane of the mallard duck after various days of incubation was carried out. Blood vessels within the mesoderm were counted per millimeter of membrane by light microscopy (40x). The chorioallantoic membrane had three distinct layers from day 12 to 24 of incubation, the chorionic epithelium, the mesoderm, and the allantoic epithelium. After day 12, chorionic epithelium consisted of two layers of flattened, elongated epithelial cells interfaced by numerous desmosomes, and separated from the underlying mesoderm by a basement membrane. At this stage, the allantoic epithelium consisted of a single layer of flattened, overlapping cells. Blood capillaries were observed in the mesoderm close to the chorionic epithelium on days 12 and 13; by day 14, these capillaries were located within the chorionic epithelium, forming a capillary sinus. Between days 14 and 16, the chorion underwent cellular and cytological differentiation into three cell types: capillary covering cells, villus cavity cells, and less differentiated basal cells. The mesoderm was composed of a loose matrix of mesenchymal cells and collagen fibrils through which coursed blood and lymphatic vessels. The vascular density in the mesoderm increased rapidly from 4.2+/-0.6 vessels per mm (n = 12) on day 12 to a maximum of 9.4+/-0.3 vessels per mm (n = 15) by day 16. From day 16, the allantoic epithelium had two to three layers of elongated and overlapping cells. The luminal layer of allantoic epithelial cells had microvillus projections and varying numbers of membrane-bound dense vesicles at all stages from day 12 onward. The histologic and ultrastructural features of mallard duck chorioallantoic membrane from day 12 to 24 of incubation were very similar to those described in the chorioallantoic membrane of the chicken (Gallus gallus) from day 8 to 20 of incubation. Much of the information available concerning the CAM of the chicken also may apply to the CAM of the mallard, with timing adjusted to match the developmental time-frame recorded here.

Antiangiogenesis Is Produced by Nontoxic Doses of Vinblastine

The effects of vinblastine (VBL) on endothelial cell functions involved in angiogenesis, namely proliferation, chemotaxis, spreading on fibronectin (FN), secretion of matrix-metalloproteinase-2 (MMP-2) and MMP-9, and morphogenesis on Matrigel were tested in vitro, whereas its effects on angiogenesis were studied in vivo by using the chick embryo chorioallantoic membrane (CAM) model. In vitro, at noncytotoxic doses (0.1, 0.25, 0.5, 0.75, and 1 pmol/L), VBL impacted all these functions, except secretion of MMPs, in a dose-dependent fashion. By contrast, proliferation of other primary cells such as fibroblasts and lymphoid tumor cells was not impacted. In vivo, VBL at 0.5, 0.75, and 1 pmol/L again displayed a dose-dependent antiangiogenic activity. Lack of cytotoxicity in vitro and in vivo was shown both morphologically, and also because the antiangiogenic effects were rapidly abolished when VBL was removed. Apoptosis was not induced. At the ultrastructural level, impairment of cell functions in vitro was associated with thin disturbance of the cytoskeleton, in the form of slight depolymerization and accumulation of microfilaments, which was equally reversible. Results suggest that VBL has an antiangiogenic component at very low, noncytotoxic doses, and that antiangiogenesis by VBL could be used to treat a wide spectrum of angiogenesis-dependent diseases, including certain chronic inflammatory diseases, Kaposi's sarcoma, and cancer.

Antiangiogenesis Is Produced by Nontoxic Doses of Vinblastine

The effects of vinblastine (VBL) on endothelial cell functions involved in angiogenesis, namely proliferation, chemotaxis, spreading on fibronectin (FN), secretion of matrix-metalloproteinase-2 (MMP-2) and MMP-9, and morphogenesis on Matrigel were tested in vitro, whereas its effects on angiogenesis were studied in vivo by using the chick embryo chorioallantoic membrane (CAM) model. In vitro, at noncytotoxic doses (0.1, 0.25, 0.5, 0.75, and 1 pmol/L), VBL impacted all these functions, except secretion of MMPs, in a dose-dependent fashion. By contrast, proliferation of other primary cells such as fibroblasts and lymphoid tumor cells was not impacted. In vivo, VBL at 0.5, 0.75, and 1 pmol/L again displayed a dose-dependent antiangiogenic activity. Lack of cytotoxicity in vitro and in vivo was shown both morphologically, and also because the antiangiogenic effects were rapidly abolished when VBL was removed. Apoptosis was not induced. At the ultrastructural level, impairment of cell functions in vitro was associated with thin disturbance of the cytoskeleton, in the form of slight depolymerization and accumulation of microfilaments, which was equally reversible. Results suggest that VBL has an antiangiogenic component at very low, noncytotoxic doses, and that antiangiogenesis by VBL could be used to treat a wide spectrum of angiogenesis-dependent diseases, including certain chronic inflammatory diseases, Kaposi's sarcoma, and cancer.

Bone Marrow Neovascularization, Plasma Cell Angiogenic Potential, and Matrix Metalloproteinase-2 Secretion Parallel Progression of Human Multiple Myeloma

To assess whether the progression of plasma cell tumors is accompanied by angiogenesis and secretion of matrix-degrading enzymes, bone marrow biopsy specimens from 20 patients with monoclonal gammopathy of undetermined significance (MGUS), 18 patients with nonactive multiple myeloma (MM), and 26 patients with active MM were evaluated for their angiogenic potential and matrix-metalloproteinase (MMP) production. A fivefold increase of the factor VIII+microvessel area was measured by a planimetric method of point counting in the bone marrow of patients with active MM as compared with nonactive MM and MGUS patients (P < .01). When serum-free conditioned media (CM) of plasma cells isolated from the bone marrow of each patient were tested in vivo for their angiogenic activity in the chick embryo chorioallantoic membrane (CAM) assay, the incidence of angiogenic samples was significantly higher (P< .01) in the active MM group (76%) compared with nonactive MM (33%) and MGUS (20%) groups. Moreover, a linear correlation (P < .01) was found between the extent of vascularization of the bone marrow of a given patient and the angiogenic activity exerted in the CAM assay by the plasma cells isolated from the same bone marrow. In vitro, a significantly higher fraction of the plasma cell CM samples from the active MM group stimulated human umbilical vein endothelial cell (HUVEC) proliferation (53%, P < .01), migration (42%, P < .05), and/or monocyte chemotaxis (38%,P < .05) when compared with nonactive MM and MGUS groups (ranging between 5% and 15% of the samples). Also, immunoassay of plasma cell extracts showed significantly higher (P < .01) levels of the angiogenic basic fibroblast growth factor (FGF)-2 in the active MM patients than in nonactive MM and MGUS patients (153 ± 59, 23 ± 17, and 31 ± 18 pg FGF-2/100 μg of protein, respectively). Accordingly, neutralizing anti–FGF-2 antibody caused a significant inhibition (ranging from 54% to 68%) of the biological activity exerted on cultured endothelial cells and in the CAM assay by plasma cell CM samples from active MM patients. Finally, in situ hybridization of bone marrow plasma cells and gelatin-zymography of their CM showed that active MM patients express significantly higher (P < .01) levels of MMP-2 mRNA and protein when compared with nonactive MM and MGUS patients, whereas MMP-9 expression was similar in all groups. Taken together, these findings indicate that the progression of plasma cell tumors is accompanied by an increase of bone marrow neovascularization. This is paralleled by an increased angiogenic and invasive potential of bone marrow plasma cells, which is dependent, at least in part, by FGF-2 and MMP-2 production. Induction of angiogenesis and secretion of MMPs by plasma cells in active disease may play a role in their medullary and extramedullary dissemination, raising the hypothesis that angiostatic/anti-MMP agents may be used for therapy of MM.

Bone Marrow Neovascularization, Plasma Cell Angiogenic Potential, and Matrix Metalloproteinase-2 Secretion Parallel Progression of Human Multiple Myeloma

To assess whether the progression of plasma cell tumors is accompanied by angiogenesis and secretion of matrix-degrading enzymes, bone marrow biopsy specimens from 20 patients with monoclonal gammopathy of undetermined significance (MGUS), 18 patients with nonactive multiple myeloma (MM), and 26 patients with active MM were evaluated for their angiogenic potential and matrix-metalloproteinase (MMP) production. A fivefold increase of the factor VIII+microvessel area was measured by a planimetric method of point counting in the bone marrow of patients with active MM as compared with nonactive MM and MGUS patients (P &lt; .01). When serum-free conditioned media (CM) of plasma cells isolated from the bone marrow of each patient were tested in vivo for their angiogenic activity in the chick embryo chorioallantoic membrane (CAM) assay, the incidence of angiogenic samples was significantly higher (P&lt; .01) in the active MM group (76%) compared with nonactive MM (33%) and MGUS (20%) groups. Moreover, a linear correlation (P &lt; .01) was found between the extent of vascularization of the bone marrow of a given patient and the angiogenic activity exerted in the CAM assay by the plasma cells isolated from the same bone marrow. In vitro, a significantly higher fraction of the plasma cell CM samples from the active MM group stimulated human umbilical vein endothelial cell (HUVEC) proliferation (53%, P &lt; .01), migration (42%, P &lt; .05), and/or monocyte chemotaxis (38%,P &lt; .05) when compared with nonactive MM and MGUS groups (ranging between 5% and 15% of the samples). Also, immunoassay of plasma cell extracts showed significantly higher (P &lt; .01) levels of the angiogenic basic fibroblast growth factor (FGF)-2 in the active MM patients than in nonactive MM and MGUS patients (153 ± 59, 23 ± 17, and 31 ± 18 pg FGF-2/100 μg of protein, respectively). Accordingly, neutralizing anti–FGF-2 antibody caused a significant inhibition (ranging from 54% to 68%) of the biological activity exerted on cultured endothelial cells and in the CAM assay by plasma cell CM samples from active MM patients. Finally, in situ hybridization of bone marrow plasma cells and gelatin-zymography of their CM showed that active MM patients express significantly higher (P &lt; .01) levels of MMP-2 mRNA and protein when compared with nonactive MM and MGUS patients, whereas MMP-9 expression was similar in all groups. Taken together, these findings indicate that the progression of plasma cell tumors is accompanied by an increase of bone marrow neovascularization. This is paralleled by an increased angiogenic and invasive potential of bone marrow plasma cells, which is dependent, at least in part, by FGF-2 and MMP-2 production. Induction of angiogenesis and secretion of MMPs by plasma cells in active disease may play a role in their medullary and extramedullary dissemination, raising the hypothesis that angiostatic/anti-MMP agents may be used for therapy of MM.

Lipoprotein (a) induces angiogenesis on the chick embryo chorioallantoic membrane

BACKGROUND

Both lipoprotein (a) [Lp(a)] and angiogenesis have been shown to be associated with initiation and progression of atherosclerotic plaque. Lp(a) and two neutralizing anti-Lp(a) antibodies were investigated for their capacity to affect the vasoproliferative processes of the chick embryo chorioallantoic membrane (CAM), a useful model for such an investigation.

METHODS

Gelatin sponges loaded with Lp(a) alone or together with anti-Lp(a) antibodies, or with vehicle alone, phosphate-buffered saline (PBS), were implanted in vivo onto the CAM at incubation day 8. Four days later, sponges and the adjacent CAM tissues were assessed for the extent of angiogenesis in terms of microvessel counts.

RESULTS

Lp(a)-loaded sponges gave significantly higher counts than those loaded with the LP(a)-anti-Lp(a) antibodies complex, which overlapped those treated with PBS. The angiogenic response was similar to that obtained with basic fibroblast growth factor, a well known angiogenic molecule.

CONCLUSION

These data suggest that Lp(a) is capable of inducing angiogenesis in vivo, which might account for its ability to enhance and support atherosclerosis.

Systemic sclerosis stimulates angiogenesis in the chick embryo chorioallantoic membrane

Skin biopsies from patients with systemic sclerosis (SSc) were investigated for their angiogenic activity by using the chick embryo chorioallantoic membrane (CAM) assay. Ten samples of SSc and 10 of normal skin from age- and sex-matched subjects were grafted onto the CAM, and the angiogenic response in pathological and control implants was assessed on histological sections by a planimetric point-count method 4 days after grafting. The vascular counts in the area underlying the SSc were significantly higher than those of normal skin and a dense mononuclear cell infiltrate was detectable around the blood vessels in pathological specimens. These results suggest that SSc may promote angiogenesis, perhaps leading to the release of several angiogenic factors. Moreover, the role played in the angiogenic response by the inflammatory cells forming the cellular infiltrate is suggested by this study.

Human lymphoblastoid cells produce extracellular matrix-degrading enzymes and induce endothelial cell proliferation, migration, morphogenesis, and angiogenesis

Human lymphoproliferative diseases can be hypothesized to invade locally and to metastatize via mechanisms similar to those developed by a variety of solid tumors, i.e., the secretion of extracellular matrix-degrading enzymes and stimulation of angiogenesis. To assess this hypothesis, Namalwa, Raji, and Daudi cell lines (Burkitt's lymphoma), LIK and SB cell lines (B-cell lymphoblastic leukemia), CEM and Jurkat cell lines (T-cell lymphoblastic leukemia), and U266 cell line (multiple myeloma) were evaluated for their capacity to produce matrix metalloproteinase-2 and -9, and urokinase-type plasminogen activator. These cell lines were also assessed for their ability: (1) to produce the angiogenic basic fibroblast growth factor and vascular endothelial growth factor; (2) to induce an angiogenic phenotype in cultured endothelial cells, represented by cell proliferation, chemotaxis, and morphogenesis; (3) to stimulate angiogenesis in different in vivo experimental models. All cell lines expressed the mRNA for one or both metalloproteinases. Namalwa, Raji, LIK, SB, and U266 cells secreted the active form of both metalloproteinases, while Daudi, CEM, and Jurkat cells produced metalloproteinase-2 but not-9. In contrast, urokinase-type plasminogen activator was secreted only by SB cells. While Raji, LIK, SB, CEM, and Jurkat cells secreted both basic fibroblast growth factor and vascular endothelial growth factor, Daudi and U266 cells produced only the former, and Namalwa cells only the latter. Accordingly, the conditioned medium of all cell lines stimulated cell proliferation and/or chemotaxis in cultured endothelial cells, with the exception of that of Namalwa cells which was ineffective. The conditioned medium of CEM and Jurkat cells induced morphogenesis in cultured endothelial cells grown on a reconstituted basement membrane (Matrigel). Lastly, Namalwa, Raji, LIK, SB, U266, CEM, and Jurkat cells induced angiogenesis and mononuclear cell recruitment in the murine Matrigel sponge model and in a chick embryo chorioallantoic membrane assay. The extent of angiogenesis in both models was strictly correlated with the density of the mononuclear cell infiltrate. The results indicate that human lymphoproliferative disease cells possess both local and remote invasive ability via the secretion of matrix-degrading enzymes and the induction of angiogenesis which is fostered by host inflammatory cells and by an intervening ensemble of angiogenic factors.

Transferrin promotes endothelial cell migration and invasion: implication in cartilage neovascularization

During endochondral bone formation, avascular cartilage differentiates to hypertrophic cartilage that then undergoes erosion and vascularization leading to bone deposition. Resting cartilage produces inhibitors of angiogenesis, shifting to production of angiogenic stimulators in hypertrophic cartilage. A major protein synthesized by hypertrophic cartilage both in vivo and in vitro is transferrin. Here we show that transferrin is a major angiogenic molecule released by hypertrophic cartilage. Endothelial cell migration and invasion is stimulated by transferrins from a number of different sources, including hypertrophic cartilage. Checkerboard analysis demonstrates that transferrin is a chemotactic and chemokinetic molecule. Chondrocyte-conditioned media show similar properties. Polyclonal anti-transferrin antibodies completely block endothelial cell migration and invasion induced by purified transferrin and inhibit the activity produced by hypertrophic chondrocytes by 50-70% as compared with controls. Function-blocking mAbs directed against the transferrin receptor similarly reduce the endothelial migratory response. Chondrocytes differentiating in the presence of serum produce transferrin, whereas those that differentiate in the absence of serum do not. Conditioned media from differentiated chondrocytes not producing transferrin have only 30% of the endothelial cell migratory activity of parallel cultures that synthesize transferrin. The angiogenic activity of transferrins was confirmed by in vivo assays on chicken egg chorioallantoic membrane, showing promotion of neovascularization by transferrins purified from different sources including conditioned culture medium. Based on the above results, we suggest that transferrin is a major angiogenic molecule produced by hypertrophic chondrocytes during endochondral bone formation.

Term ovine placental vasculature: comparison of sea level and high altitude conditions by corrosion cast and histomorphometry

The placental vascular architecture differs significantly at high altitude from that at sea level in the human and guinea-pig. Four sheep between 137 and 140 days of gestation, kept near sea level throughout gestation, were used as a normoxic control group for comparison of the placental vasculature with 10 other ewes, kept at high altitude (3820 m above sea level; Barcroft Laboratory, White Mountain Research Station, CA, USA). Placentomes from both groups were prepared for histology and scanning electron microscopy of vascular corrosion casts. Singular perfusion of fetal placentae, as well as combined maternal/fetal injection was performed. The influence of long-term hypoxaemia was determined by qualitative and semi-quantitative evaluation of corrosion casts and histological sections. The fetal vessel casts show a distinct difference in the arrangement of vessels of all sizes in response to long-term hypoxaemia. In the control group, stem arteries and veins are straight and parallel. In contrast, this is much less evident in the hypoxaemic group because arterioles and venules branch off the stem vessels more frequently and in an irregular manner. This leads to a capillary bed that is much more dense due to increased branching and capillary coiling. These observations are confirmed by histomorphometry. In the fetal vessels of high altitude sheep placentomes, we observed a decreased number of vascular cross sections (21.6 +/- 4.7 SEM versus 27.7 +/- 4.0 SEM; P = 0.02). However, the average luminal size per cross section (77.9 +/- 10.5 microns2 SEM versus 59.4 +/- 7.4 microns2 SEM; P = 0.004) was increased at high altitude and the percentage of lumina of the total area (5.7 +/- 0.5 SEM versus 5.3 +/- 0.3 SEM; P = 0.09) indicated a trend towards an increase. In maternal vessels of high altitude placentomes, the number of vessel cross sections (6.5 +/- 0.7 SEM versus 6.0 +/- 0.5 SEM; P = 0.2) remained unchanged, whereas the average luminal size (1108 +/- 122 microns2 SEM versus 844 +/- 77 microns2 SEM; P < 0.001) and the percentage of lumina out of the total area (20.9 +/- 1.8 SEM versus 17.5 +/- 1.7 SEM; P < 0.001) were increased. The interhaemal distance appeared to be slightly but not significantly increased at high altitude. These findings indicate that at high altitude the sheep placenta develops an increased materno-fetal absorptive surface to help guarantee substance exchange.

Bromodeoxyuridine: a diagnostic tool in biology and medicine, Part III. Proliferation in normal, injured and diseased tissue, growth factors, differentiation, DNA replication sites and in situ hybridization

This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.

Tumor necrosis factor alpha (rhTNF) fails to stimulate angiogenesis in the rabbit cornea

BACKGROUND

The objective of this study was to thoroughly examine the in vivo angiogenesis activity of human recombinant tumor necrosis factor alpha (rhTNF).

METHODS

rhTNF (0.5 ng to 1.0 microgram) was incorporated into the slow release polymers Hydron or HYPAN and implanted into the rabbit cornea. Release of biologically active rhTNF from the polymers was determined with the L929 cytotoxicity assay.

RESULTS

All concentrations tested failed to elicit capillary formation beyond that observed for controls. Less than 2% of the rhTNF was released from the Hydron over 7 days. HYPAN released five times the amount of rhTNF in vitro, but even at doses of 500 ng (104.3 ng suggested release) no angiogenesis was stimulated.

CONCLUSIONS

Under the circumstances tested, rhTNF is not angiogenic in vivo.

Contraction of fibrillar type I collagen by endothelial cells: a study in vitro

The formation of microvascular sprouts during angiogenesis requires that endothelial cells move through an extracellular matrix. Endothelial cells that migrate in vitro generate forces of traction that compress (i.e., contract) and reorganize vicinial extracellular matrix, a process that might be important for angiogenic invasion and morphogenesis in vivo. To study potential relationships between traction and angiogenesis, we have measured the contraction of fibrillar type I collagen gels by endothelial cells in vitro. We found that the capacity of bovine aortic endothelial (BAE) cells to remodel type I collagen was similar to that of human dermal fibroblasts--a cell type that generates high levels of traction. Contraction of collagen by BAE cells was stimulated by fetal bovine serum, human plasma-derived serum, bovine serum albumin, and the angiogenic factors phorbol myristate acetate and basic fibroblast growth factor (bFGF). In contrast, fibronectin and immunoglobulin from bovine serum, several nonserum proteins, and polyvinyl pyrrolidone (a nonproteinaceous substitute for albumin in artificial plasma) were not stimulatory. Contraction of collagen by BAE cells was diminished by an inhibitor of metalloproteinases (1,10-phenanthroline) at concentrations that were not obviously cytotoxic. Zymography of proteins secreted by BAE cells that had contracted collagen gels revealed matrix metalloproteinase 2. Subconfluent BAE cells that were migratory and proliferating were more effective contractors of collagen than were quiescent, confluent cells of the same strain. Moreover, bovine capillary endothelial cells contracted collagen gels to a greater degree than was seen with BAE cells. Collectively, our observations indicate that traction-driven reorganization of fibrillar type I collagen by endothelial cells is sensitive to different mediators, some of which, e.g., bFGF, are known regulators of angiogenesis in vivo.

Macromolecular selectivity of chick chorioallantoic membrane microvessels during normal angiogenesis and endothelial differentiation

Progressive angiogenesis and endothelial differentiation in the chick chorioallantoic membrane (CAM) serve to accommodate oxygen demands of the growing embryo. The present study evaluated CAM microvascular endothelial permselectivity during the most rapid phase of angiogenesis (day 10) and after initiation of endothelial cytodifferentiation (day 14). Chick embryos were incubated using established shell-less culture techniques for intravital and ultrastructural observations. Systemic microinjections of FITC-dextrans (40, 70 and 150 KDa) provided an index of endothelial permselectivity after 2.5 min and 10 min perfusions. Ultrastructural examinations of the same dextran probes served to detect small, intermittent foci within the perivascular interstitium. Although minor variations of dextran particle distributions around specific segments of the microcirculation were observed ultrastructurally, perivascular accumulation was not sufficient to elicit a detectable fluorescent signal. Thus, substantial accumulation of the graded-dextran series in the perivascular interstitium was not detected. Morphometric analyses of the precapillary, capillary, and postcapillary microvascular segments served to demonstrate a continuous endothelium which displayed cytoplasmic attenuation at day 14. Plasmalemmal vesicles were few and uniform within the microvascular units at day 10. A three-fold increase in vesicle densities characterized the precapillary endothelia at day 14. Average widths of the endothelial junctional clefts were homogeneous within the segmental microvascular endothelia at both days 10 and 14. Junctional cleft lengths were also homogeneous, except the significantly longer capillary endothelial clefts observed at day 10. These results are consistent with the concept that, despite certain differences in segmental vesicle densities and junctional cleft lengths, neovascularization of the CAM is achieved without excessive macromolecular efflux across the microvascular endothelia.