Culture of bovine thoracic duct endothelial cells

The topography of microstructured surfaces differently affects fibrillin deposition by blood and lymphatic endothelial cells in culture

While tissue-engineered blood vessels have already been successfully used in surgical practice, artificially restoring lymphatic circulation when needed is still far to be realized. Stability of arterial vessel wall depends on proper fibrillin deposition; fibrillin in fact is the scaffold for elastic fiber formation. In lymphatic vessels fibrillin is probably implied in lymph formation in response to interstitial requirements. This study was designed to verify whether fibrillin deposition is influenced by the topography of the substrate on which blood and lymphatic endothelial cells grow. Blood and lymphatic endothelial cells were cultured on microstructured surfaces with different topography: stripes of different widths (25, 50, and 100 microm), squares and rectangles, and spiral geometry, obtained by the photoimmobilization of Hyaluronan (Hyal) on aminosilanized glass. Cell orientation and fibrillin deposition were influenced by the topography of the microstructure. Blood endothelial cells deposited fibrillin as a bundle running parallel to the major axis of stripes and spirals, whereas the irregular network of fibrillin deposited by lymphatic endothelial cells was affected by the topography of the substrate only in the smallest stripes. These data bring a contribution to the basic knowledge required to design tissue-engineered blood and lymphatic vessels capable of adapting to the functional requirements of the surrounding environment.

Protein expression profiles of Bos taurus blood and lymphatic vessel endothelial cells

The endothelium is a metabolically active organ that regulates the interaction between blood or lymph and the vessel or the surrounding tissue. Blood endothelium has been the object of many investigations whereas lymphatic endothelium biology is yet poorly understood. This report deals with a proteomic approach to the characterization and comparative analysis of lymphatic and blood vessel endothelial cells (ECs). By 2-DE we visualized the protein profiles of EC extracts from the thoracic aorta, inferior vena cava, and thoracic duct of Bos taurus. The three obtained electropherograms were then analyzed by specific software, and 113 quantitative and 25 qualitative differences were detected between the three endothelial gels. The cluster analysis of qualitative and quantitative differences evidenced the protein pattern of lymphatic ECs to be more similar to the venous than to the arterial one. Moreover, venous ECs were interestingly found showing a protein expression profile more similar to the lymphatic ECs than to the arterial ones. We also identified 64 protein spots by MALDI-TOF MS and ESI-IT MS/MS and three reference maps of bovine endothelium were obtained. The functional implications of the identified proteins in vascular endothelial biology are discussed.

Lymphangiogenesis does not occur in breast cancer

Breast cancer metastasis predominantly occurs via lymphatic vessels. However, the study of lymphatic vessels and lymphangiogenesis has been hampered by lack of specific markers. Recently, antibodies directed against M2A (D2-40), Podoplanin, and Prox-1 that specifically mark lymphatic vessels in paraffin-embedded sections have become available. These were used to study lymphangiogenesis in archival paraffin sections of normal breast (n = 23), fibrocystic disease (n = 7), ductal carcinoma in situ (n = 32), invasive ductal carcinoma (n = 50), and invasive lobular carcinoma (n = 5). In addition, endothelial proliferation in lymphatic vessels was analyzed by dual-color immunohistochemistry with D2-40 and proliferating cell nuclear antigen (PCNA). Expression of D2-40, Prox-1, and Podoplanin was seen in lymphatic vessels but not in blood vessels. Lymphatic vessels were seen in the peritumoral area and as "entrapped" intratumoral vessels adjacent to preexisting normal lobules and ducts. Unlike angiogenesis, there was no increase of lymphatic vessel density in association with neoplastic transformation. On the contrary, a marked reduction in intratumoral lymphatic vessel density was seen in comparison to normal breast tissue, fibrocystic disease, and ductal carcinoma in situ (P = 0.0001). There was an increase in peritumoral lymphatic vessel density as compared with normal breast (P = 0.0001). However, the endothelial cells in the "entrapped" or the peritumoral lymphatic vessels did not show any expression of PCNA indicating minimal or no proliferative activity. This was in contrast to the strong expression seen in adjacent tumor cells and blood vessel endothelial cells. Thus, lymphangiogenesis was not evident when studied by lymphatic vessel density or by lymph vessel endothelial proliferation.

Role of the Hyal−Cu (II) Complex on Bovine Aortic and Lymphatic Endothelial Cells Behavior on Microstructured Surfaces

The ability of micropatterned surfaces to modulate cell behavior is combined with the well-known angiogenic property of the hyaluronan-Cu (II) complex. Hyaluronan-Cu (II) microstripes 100 and 25 mum wide on aminosilanised glass substrates were fabricated by photoimmobilization following two different methods: i.e., method I consisting in the photoimmobilization of the Hyal-Cu (II) complex; and method II based on the photoimmobilization of Hyal followed by the coordination with Cu (II). The chemistry and topography of the fabricated micropatterned samples were investigated by ATR FT-IR, atomic absorption, AFM, SEM, and ToF-SIMS. ATR FT-IR analysis demonstrated that hyaluronan conjugated with a photoreactive moiety was able to coordinate Cu (II) ions and that the photoimmobilization process was successful, as indicated by the intensity decrease of the IR band of the azidic group after the photoreaction. AFM and SEM images showed that reproducible Hyal-Cu (II) microstructures with both chemical and topographical heterogeneities have been obtained by the two preparation methods. The distribution of copper on the fabricated Hyal-Cu (II) microstructures has been investigated by ToF-SIMS. In both ToF-SIMS images and spectra, on Hyal-Cu (II) microstructures prepared by method I, the Cu peak (63 m/z) was detected only on the Hyal-Cu (II) microstripes, while on Hyal-Cu (II) microstructures prepared by method II, the Cu peak showed the same intensity both on the Hyal-Cu (II) microstripes and on the aminosilanised glass substrate, in agreement with the higher amount of Cu revealed by atomic absorption. The influence of Hyal-Cu (II) micropatterned surfaces on BAEC and LEC, in terms of migration and adhesion, has been analyzed. The results obtained indicate that Hyal-Cu (II) influences BAEC behavior inducing cell migration, while it is devoid of any effect on LEC.

Lymphatics at the crossroads of angiogenesis and lymphangiogenesis

The lymphatic system is implicated in interstitial fluid balance regulation, immune cell trafficking, oedema and cancer metastasis. However, the sequence of events that initiate and coordinate lymphatic vessel development (lymphangiogenesis) remains obscure. In effect, the understanding of physiological regulation of lymphatic vasculature has been overshadowed by the greater emphasis focused on angiogenesis, and delayed by a lack of specific markers, thereby limiting this field to no more than a descriptive characterization. Recently, new insights into lymphangiogenesis research have been due to the discovery of lymphatic-specific markers and growth factors of vascular endothelial growth factor (VEGF) family, such as VEGF-C and VEGF-D. Studies using transgenic mice overexpressing VEGF-C and VEGF-D have demonstrated a crucial role for these factors in tumour lymphangiogenesis. Knowledge of lymphatic development has now been redefined at the molecular level, providing an interesting target for innovative therapies. This review highlights the recent insights and advances into the field of lymphatic vascular research, outlining the most important aspects of the embryo development, structure, specific markers and methods applied for studying lymphangiogenesis. Finally, molecular mechanisms involved in the regulation of lymphangiogenesis are described.

Focal adhesion molecules expression and fibrillin deposition by lymphatic and blood vessel endothelial cells in culture

The microfibrils of anchoring filaments, a typical ultrastructural feature of initial lymphatic vessels, consist mainly of fibrillin and are similar to the microfibrils of elastic fibers. As we previously demonstrated, they radiate from focal adhesions of lymphatic endothelium to the perivascular elastic network. Although present in large blood vessels, fibrillin microfibrils have never been detected in blood capillaries. Here we report immunohistochemical evidence that cultured bovine aortic and lymphatic endothelial cells express fibrillin microfibrils. These microfibrils form an irregular web in lymphatic endothelial cells, whereas in blood vessel endothelial cells they are arranged in a honeycomb pattern. Cultured lymphatic and blood vessel endothelial cells also produce focal adhesion molecules: focal adhesion kinase, vinculin, talin, and cytoskeletal beta-actin. Our data suggest that anchoring filaments of initial lymphatic vessels in vivo may be produced by endothelium. Through their connection with focal adhesions, they may form a mechanical anchorage for the thin wall of initial lymphatic vessels and a transduction device for mechanical signals from the extracellular matrix into biochemical signals in endothelial cells. The complex anchoring filaments-focal adhesions may control the permeability of lymphatic endothelium and finely adjust lymph formation to the physiological conditions of the extracellular matrix. The different deposition of fibrillin microfibrils in blood vessel endothelial cells may be related to the necessity of withstanding shear forces. Thus, in our opinion, differences in fibrillin deposition imply a different role of fibrillin in blood vessel and lymphatic endothelium.

A novel monoclonal antibody specific for lymphatic endothelium

The difficulty of identifying and differentiating lymphatic and blood microvessels in tissue sections can be overcome by a monoclonal antibody specific for lymphatic endothelium. Unfortunately, the only known antibody also reacts with the endothelium of some blood vessels. The technique of double immunization (passive, with an antiserum to blood endothelium, and active, with a suspension of lymphatic endothelial cells) was, therefore, used to increase the chances of recognizing specific lymphatic antigens by the mouse immune system. The monoclonal antibody obtained, LyMAb, a G1 immunoglobulin, reacted strongly with the endothelium of bovine thoracic duct, mesenteric collecting vessels and lymphatic vessels of gallbladder and lymph nodes and moderately with those of the intestinal wall. Blood vessels (intercostal arteries, azygos vein and blood microvessels of all organs tested) were consistently negative. The antibody was species-specific and did not react with formalin-fixed, paraffin-embedded sections. Cross-reactivity was limited to some connective tissue fibres and scattered cells in the lymph node parenchyma, intestinal villi and hepatic lobules.