Summary. Background: Blood-derived endothelial progenitor cells (EPC) have been used to treat ischemic disease. However, the number of EPC that can be obtained from adult blood is limited. Objective: To characterize endotheliallike cells obtained from human bone marrow and determine their ability to stimulate new blood vessel formation in vivo. Methods: Mononuclear cells (MNC) were isolated from human bone marrow or umbilical cord blood and cultured in endothelial growth medium (EGM-2). Mesenchymal stem cells (MSC) were isolated from bone marrow and induced to differentiate into endothelial-like cells (MSCE), or adipocytes or osteocytes by growth in EGM-2, adipogenic or osteogenic medium. Results: Cells obtained by culturing bone marrow MNC in EGM-2 formed cord-or tube-like structures when grown on Matrigel TM and expressed several endothelial marker proteins. However, cell morphology and the profile of endothelial marker protein expression were different from those of cord blood-derived EPC (cbEPC). Cells with a similar phenotype were obtained by differentiation of MSC into MSCE, which was accompanied by an increase of endothelial marker proteins and a diminished capacity to differentiate into adipocytes. Subcutaneous implantation of MSCE in collagen plugs in non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice resulted in formation of functional blood vessels that had incorporated the MSCE. Conclusions: Our results show that MSCE and cbEPC are different cell types. The formation of functional blood vessels by MSCE, combined with high yields and a reduced capacity to differentiate into other cell types compared with MSC, makes these cells potentially useful for autologous therapy of ischemic disease.
SummaryAntiphospholipid antibodies (aPLA) are associated with thrombophilia and recurrent pregnancy loss. They bind directly to anionic phospholipids or via phospholipid-binding proteins such as β2-glycoprotein 1 (β2GP1). The underlying mechanisms by which aPLA induce a thrombophilic phenotype are not well understood.The present work was done to determine whether antibodies to β2GP1 activate endothelial cells (EC) and whether NFκB is involved in this activation. Incubation of EC with these antibodies resulted in a redistribution of NFκB from the cytoplasm to the nucleus after a delay of several hours. This was accompanied by an increased expression of tissue factor and of the leukocyte adhesion molecules ICAM-1, VCAM-1 and E-selectin. Inhibition of the nuclear translocation of NFκB abolished the response to these antibodies. In comparison to anti-β2GP1 antibodies, incubation of EC with TNF resulted in a more rapid (within 30 minutes) redistribution of NFκB and a more pronounced expression of tissue factor and of the leukocyte adhesion molecules. The slower response to the antibodies as compared to TNF suggests that the NFκB response to anti-β2GP1 antibodies is indirect.Taken together our results imply that NFκB is an essential intermediate in the activation of EC by anti-β2GP1 antibodies.
Objective— The gap junction protein connexin37 (Cx37) plays an important role in cell-cell communication in the vasculature. A C1019T Cx37 gene polymorphism, encoding a P319S substitution in the regulatory C terminus of Cx37 (Cx37CT), correlates with arterial stenosis and myocardial infarction in humans. This study was designed to identify potential binding partners for Cx37CT and to determine whether the polymorphism modified this interaction. Methods and Results— Using a high-throughput phage display, we retrieved 2 binding motifs for Cx37CT: WHK … [K,R]XP … and FHK … [K,R]XXP … , the first being more common for Cx37CT-319P and the second more common for Cx37CT-319S. One of the peptides (WHRTPRLPPPVP) showed 77.7% homology with residues 843 to 854 of endothelial nitric oxide synthase (eNOS). In vitro binding of this peptide or of the homologous eNOS sequence to both Cx37CT isoforms was confirmed by cross-linking and surface plasmon resonance. Electrophysiological analysis of Cx37 single channel activity in transfected N2a cells showed that eNOS-like and eNOS(843–854) increased the frequency of events with conductances higher than 300 pS. We demonstrated that eNOS coimmunoprecipitated with Cx37 in a mouse endothelial cell (EC) line (bEnd.3), human primary ECs, and a human EC line transfected with Cx37-319P or Cx37-319S. Cx37 and eNOS colocalized at EC membranes. Moreover, a dose-dependent increase in nitric oxide production was observed in ECs treated with Cx37 antisense. Conclusion— Overall, our data show for the first time a functional and specific interaction between eNOS and Cx37. This interaction may be relevant for the control of vascular physiology both in health and in disease.
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