Association of Maternal Antiangiogenic Profile at Birth With Early Postnatal Loss of Microvascular Density in Offspring of Hypertensive Pregnancies.

Offspring of hypertensive pregnancies are more likely to have microvascular rarefaction and increased blood pressure in later life. We tested the hypothesis that maternal angiogenic profile during a hypertensive pregnancy is associated with fetal vasculogenic capacity and abnormal postnatal microvascular remodeling. Infants (n=255) born after either hypertensive or normotensive pregnancies were recruited for quantification of postnatal dermal microvascular structure at birth and 3 months of age. Vasculogenic cell potential was assessed in umbilical vein endothelial cells from 55 offspring based on in vitro microvessel tube formation and proliferation assays. Maternal angiogenic profile (soluble fms-like tyrosine kinase-1, soluble endoglin, vascular endothelial growth factor, and placental growth factor) was measured from postpartum plasma samples to characterize severity of pregnancy disorder. At birth, offspring born after hypertensive pregnancy had similar microvessel density to those born after a normotensive pregnancy, but during the first 3 postnatal months, they had an almost 2-fold greater reduction in total vessel density (-17.7±16.4% versus -9.9±18.7%; P=0.002). This postnatal loss varied according to the vasculogenic capacity of the endothelial cells of the infant at birth (r=0.49; P=0.02). The degree of reduction in both in vitro and postnatal in vivo vascular development was proportional to levels of antiangiogenic factors in the maternal circulation. In conclusion, our data indicate that offspring born to hypertensive pregnancies have reduced vasculogenic capacity at birth that predicts microvessel density loss over the first 3 postnatal months. Degree of postnatal microvessel reduction is proportional to levels of antiangiogenic factors in the maternal circulation at birth.

Junctional Adhesion Molecule-A Is Highly Expressed on Human Hematopoietic Repopulating Cells and Associates with the Key Hematopoietic Chemokine Receptor CXCR4.

Hematopoietic stem/progenitor cells (HSPCs) reside in specialized bone marrow microenvironmental niches, with vascular elements (endothelial/mesenchymal stromal cells) and CXCR4-CXCL12 interactions playing particularly important roles for HSPC entry, retention, and maintenance. The functional effects of CXCL12 are dependent on its local concentration and rely on complex HSPC-niche interactions. Two Junctional Adhesion Molecule family proteins, Junctional Adhesion Molecule-B (JAM)-B and JAM-C, are reported to mediate HSPC-stromal cell interactions, which in turn regulate CXCL12 production by mesenchymal stromal cells (MSCs). Here, we demonstrate that another JAM family member, JAM-A, is most highly expressed on human hematopoietic stem cells with in vivo repopulating activity (p < .01 for JAM-A(high) compared to JAM-A(Int or Low) cord blood CD34(+) cells). JAM-A blockade, silencing, and overexpression show that JAM-A contributes significantly (p < .05) to the adhesion of human HSPCs to IL-1ß activated human bone marrow sinusoidal endothelium. Further studies highlight a novel association of JAM-A with CXCR4, with these molecules moving to the leading edge of the cell upon presentation with CXCL12 (p < .05 compared to no CXCL12). Therefore, we hypothesize that JAM family members differentially regulate CXCR4 function and CXCL12 secretion in the bone marrow niche. Stem Cells 2016;34:1664-1678.

The hematopoietic chemokine CXCL12 promotes integration of human endothelial colony forming cell-derived cells into immature vessel networks.

Proangiogenic factors, vascular endothelial growth factor (VEGF), and fibroblast growth factor-2 (FGF-2) prime endothelial cells to respond to "hematopoietic" chemokines and cytokines by inducing/upregulating expression of the respective chemokine/cytokine receptors. Coculture of human endothelial colony forming cell (ECFC)-derived cells with human stromal cells in the presence of VEGF and FGF-2 for 14 days resulted in upregulation of the "hematopoietic" chemokine CXCL12 and its CXCR4 receptor by day 3 of coculture. Chronic exposure to the CXCR4 antagonist AMD3100 in this vasculo/angiogenesis assay significantly reduced vascular tubule formation, an observation recapitulated by delayed AMD3100 addition. While AMD3100 did not affect ECFC-derived cell proliferation, it did demonstrate a dual action. First, over the later stages of the 14-day cocultures, AMD3100 delayed tubule organization into maturing vessel networks, resulting in enhanced endothelial cell retraction and loss of complexity as defined by live cell imaging. Second, at earlier stages of cocultures, we observed that AMD3100 significantly inhibited the integration of exogenous ECFC-derived cells into established, but immature, vascular networks. Comparative proteome profiler array analyses of ECFC-derived cells treated with AMD3100 identified changes in expression of potential candidate molecules involved in adhesion and/or migration. Blocking antibodies to CD31, but not CD146 or CD166, reduced the ECFC-derived cell integration into these extant vascular networks. Thus, CXCL12 plays a key role not only in endothelial cell sensing and guidance, but also in promoting the integration of ECFC-derived cells into developing vascular networks.

The angiogenic properties of mesenchymal stem/stromal cells and their therapeutic potential.

BACKGROUND: Blood vessel formation is fundamental to development, while its dysregulation can contribute to serious disease. Expectations are that hundreds of millions of individuals will benefit from therapeutic developments in vascular biology. MSCs are central to the three main vascular repair mechanisms. SOURCES OF DATA: Key recent published literature and ClinicalTrials.gov. AREAS OF AGREEMENT: MSCs are heterogeneous, containing multi-lineage stem and partly differentiated progenitor cells, and are easily expandable ex vivo. There is no single marker defining native MSCs in vivo. Their phenotype is strongly determined by their specific microenvironment. Bone marrow MSCs have skeletal stem cell properties. Having a perivascular/vascular location, they contribute to vascular formation and function and might be harnessed to regenerate a blood supply to injured tissues. AREAS OF CONTROVERSY: These include MSC origin, phenotype and location in vivo and their ability to differentiate into functional cardiomyocytes and endothelial cells or act as vascular stem cells. In addition their efficacy, safety and potency in clinical trials in relation to cell source, dose, delivery route, passage and timing of administration, but probably even more on the local preconditioning and the mechanisms by which they exert their effects. GROWING POINTS: Understanding the origin and the regenerative environment of MSCs, and manipulating their homing properties, proliferative ability and functionality through drug discovery and reprogramming strategies are important for their efficacy in vascular repair for regenerative medicine therapies and tissue engineering approaches. AREAS TIMELY FOR DEVELOPING RESEARCH: Characterization of MSCs' in vivo origins and biological properties in relation to their localization within tissue niches, reprogramming strategies and newer imaging/bioengineering approaches.

A novel function for the haemopoietic supportive murine bone marrow MS-5 mesenchymal stromal cell line in promoting human vasculogenesis and angiogenesis.

The bone marrow contains specific microenvironmental stem cell niches that maintain haemopoiesis. CXCL12-expressing mesenchymal stromal cells are closely associated with the bone marrow sinusoidal endothelia, forming key elements of the haemopoietic stem cell niche, yet their ability to regulate endothelial function is not clearly defined. Given that the murine nestin(+) cell line, MS-5, provides a clonal surrogate bone marrow stromal niche capable of regulating both murine and human primitive haemopoietic stem/progenitor cell (HSC/HPC) fate in vitro, we hypothesized that MS-5 cells might also support new blood vessel formation and function. Here, for the first time, we demonstrate that this is indeed the case. Using proteome arrays, we identified HSC/HPC active angiogenic factors that are preferentially secreted by haemopoietic supportive nestin(+) MS-5 cells, including CXCL12 (SDF-1), NOV (CCN3), HGF, Angiopoietin-1 and CCL2 (MCP-1). Concentrating on CXCL12, we confirmed its presence in MS-5 conditioned media and demonstrated that its antagonist in receptor binding, AMD-3100, which mobilizes HSC/HPCs and endothelial progenitors from bone marrow, could significantly reduce MS-5 mediated human vasculogenesis in vitro, principally by regulating human endothelial cell migration. Thus, the clonal nestin(+) MS-5 murine bone marrow stromal cell line not only promotes human haemopoiesis but also induces human vasculogenesis, with CXCL12 playing important roles in both processes.

Endothelial progenitor cells and their potential therapeutic applications.

Endothelial progenitor cells (EPCs) are derived from the bone marrow (BM) and peripheral blood (PB), contributing to tissue repair in various pathological conditions via the formation of new blood vessels, that is, neovascularization. EPCs can be mobilized into the circulation in response to growth factors and cytokines released following stimuli such as vascular trauma, wounding and cancer. EPCs are involved in vasculogenesis during embryogenesis, but are now recognized to have a significant bearing upon disease outcome through their contribution to neovascularization in a variety of pathological states in adulthood. EPCs exist in very small numbers, especially in circulating blood in adults where they only account for 0.01% of all cells. We discuss the contribution and potential therapeutic applications of EPCs in disease, also noting the prognostic value of PB EPC numbers, especially in heart disease and cancer.