Abstract
IntroductionEndothelial progenitor cells (EPCs) have an important role in the process of vascular injury repair. Platelets have been shown to mediate EPC recruitment, maturation and differentiation. Yet, the mechanism underlying this interaction is unclear. We, therefore, aimed to examine whether direct contact between platelets and EPCs is essential for the positive platelets-EPC effect, and to investigate the main mediators responsible for the improvement in EPCs function.MethodsHuman EPCs were isolated from donated buffy coats and cultured in either: 1. EPCs co-incubated with platelets placed in a 1 µm-Boyden chamber. 2. EPCs incubated with or without platelets in the presence or absence of bFGF/PDGF Receptor inhibitor (PDGFRI). After 7 days culture, EPCs ability to form colonies, proliferate and differentiate was examined. Culture supernatants were collected and growth factors levels were evaluated using ELISA. Growth factors mRNA levels in EPCs were evaluated using RT-PCR.Results and ConclusionsAfter 7 days culture, EPCs functional properties were higher following co-incubation with platelets (directly or indirectly), implying that direct contact is not essential for the platelet’s positive effect on EPCs. This effect was reduced by PDGFRI inhibition. Additionally, higher levels of PDGFB in EPCs-platelets supernatant and higher levels of PDGFC mRNA in EPCs co-incubated with platelets were found. In contrast, FGF and other potential mediators that were examined and inhibited did not significantly affect the interaction between platelets and EPCs. Thus, we conclude that PDGF has a central role in the interaction between platelets and EPCs. Further study is required to examine additional aspects of EPC-platelets interaction.
Highlights
Endothelial progenitor cells (EPCs) have an important role in the process of vascular injury repair
We found that the number of colonies and culture viability was significantly higher in Endothelial Progenitor Cells (EPCs) that had been co-incubated with platelets directly or indirectly compared to EPCs that were incubated on fibronectin alone [for indirect incubation: 3.1160.48 vs. 2.2260.35 colonies per field, respectively (Figure 2A, 2C) and 0.1560.031 vs. 0.1160.016 OD 560 nm, respectively (Figure 2B), for direct incubation: 3.3760.81 vs. 2.0560.48 colonies per field respectively (Figure 3A) and 0.14160.025 vs. 0.09560.0172 560 nm, respectively (Figure 3B)]
This study examined the potential pathways mediating the interaction between EPCs and platelets, and the positive effect platelets exert on EPCs
Summary
Endothelial progenitor cells (EPCs) have an important role in the process of vascular injury repair. Platelets have been shown to mediate EPC recruitment, maturation and differentiation. EPCs co-express CD133, CD34 and vascular endothelial growth factor receptor 2 (VEGFR-2) on their surface and have the potential to proliferate and differentiate into mature cells with endothelial phenotypic markers [3,4,5]. It has been reported that following vascular injury or ischemia these cells are recruited to the site of injury and enhance neovascularization and reendothelization [3,4,5,10] circulating CD34+ VEGFR2+ progenitor cells appear to have prognostic importance and their levels predict the occurrence of cardiovascular events including mortality in patients with cardiovascular disease [12]. EPCs isolated from patients with coronary artery disease, for instance, have a reduced capacity to migrate, proliferate, and form colonies and to differentiate [13,14,15,16,17,18]
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