CD34 expression modulates tube-forming capacity and barrier properties of peripheral blood-derived endothelial colony-forming cells (ECFCs)

Abstract

Endothelial colony-forming cells (ECFC) are grown from circulating CD34+ progenitors present in adult peripheral blood, but during in vitro expansion part of the cells lose CD34. To evaluate whether the regulation of CD34 characterizes the angiogenic phenotypical features of PB-ECFCs, we investigated the properties of CD34+ and CD34− ECFCs with respect to their ability to form capillary-like tubes in 3D fibrin matrices, tip-cell gene expression, and barrier integrity. Selection of CD34+ and CD34− ECFCs from subcultured ECFCs was accomplished by magnetic sorting (FACS: CD34+: 95 % pos; CD34−: 99 % neg). Both fractions proliferated at same rate, while CD34+ ECFCs exhibited higher tube-forming capacity and tip-cell gene expression than CD34− cells. However, during cell culture CD34− cells re-expressed CD34. Cell-seeding density, cell–cell contact formation, and serum supplements modulated CD34 expression. CD34 expression in ECFCs was strongly suppressed by newborn calf serum. Stimulation with FGF-2, VEGF, or HGF prepared in medium supplemented with 3 % albumin did not change CD34 mRNA or surface expression. Silencing of CD34 with siRNA resulted in strengthening of cell–cell contacts and increased barrier function of ECFC monolayers as measured by ECIS. Furthermore, CD34 siRNA reduced tube formation by ECFC, but did not affect tip-cell gene expression. These findings demonstrate that CD34+ and CD34− cells are different phenotypes of similar cells and that CD34 (1) can be regulated in ECFC; (2) is positively involved in capillary-like sprout formation; (3) is associated but not causally related to tip-cell gene expression; and (4) can affect endothelial barrier function.Electronic supplementary materialThe online version of this article (doi:10.1007/s10456-016-9506-9) contains supplementary material, which is available to authorized users.

Angiopoietin‐2 Promotes Pathological Angiogenesis and Is a Therapeutic Target in Murine Nonalcoholic Fatty Liver Disease

“…Indeed, CD34 acts to reduce endothelial barrier function and enhances the sprouting capacity. (33) Interestingly, CD34 immunopositivity correlated with Ang-2 serum levels in our cohort. These data substantiate the link between angiogenesis and NALFD progression and indicate the role of Ang-2 in this process.…”

“…While CD34 expression in resting endothelial cells is low, it is expressed in activated endothelium and in circulating endothelial progenitor cells that contribute to angiogenesis. Indeed, CD34 acts to reduce endothelial barrier function and enhances the sprouting capacity . Interestingly, CD34 immunopositivity correlated with Ang‐2 serum levels in our cohort.…”

Osteoprotegerin Induces CD34+ Differentiation in Endothelial Progenitor Cells

“…Our finding that OPG increases CD34 could reflect a mobilization of a more immature state of ECFCs. Previous study on CD34 in ECFCs suggests that CD34 expression is not related to different ECFCs subpopulations but is a reflect of cell plasticity and the result of angiogenic stimuli interfering with the endothelial tube formation ( 32 ). The CD34 expression is known to be inducible and down-regulated, in HUVECs, by angiogenic growth factors ( 32 , 33 ).…”

“…Previous study on CD34 in ECFCs suggests that CD34 expression is not related to different ECFCs subpopulations but is a reflect of cell plasticity and the result of angiogenic stimuli interfering with the endothelial tube formation ( 32 ). The CD34 expression is known to be inducible and down-regulated, in HUVECs, by angiogenic growth factors ( 32 , 33 ). Thus, upregulation of CD34 observed in OPG-exposed ECFCs could be both attributed to progenitor subtype expansion but also to an increased ECFCs vasculogenic potential.…”

Evidence for the existence of CD34+ angiogenic stem cells in human first‐trimester decidua and their therapeutic for ischaemic heart disease

“…CD34 is predominantly considered to be a marker of hematopoietic stem cells and vascular progenitor cells. [11][12][13] Some experts have found that human umbilical cord blood-derived CD34 + cells can repair the vascular structure of the retina and myocardium in mice. 14,15 This shows that CD34 is closely related to the formation of vessels.…”