Efficient differentiation of CD14⁺ monocytic cells into endothelial cells on degradable biomaterials

Vascular tissue engineering aims at creating self-renewing, anti-thrombogenic, vascular grafts, which can be based on endothelial progenitor cells (EPC). EPC harbor essential features such as plasticity and longevity. Unfortunately, the archetype CD34+ EPC is rare in peripheral blood. Monocytes, i.e. CD14+ cells also have the ability to differentiate into endothelial-like cells and are by far more abundant in peripheral blood than are CD34+ EPC. Therefore, CD14+ cells would seem appropriate candidates for tissue engineering of small-diameter blood vessels. In this study, we investigated the differentiation of CD14+ cells on three biodegradable biomaterials under angiogenic conditions. Morphological analyses, gene transcript analyses, endothelial marker (i.e. VE-Cadherin and eNOS) and macrophage marker (i.e. CD68 and CD163) expression analyses, revealed that a small fraction (15-25%) of cultured CD14+ cells differentiated into macrophages after 21 days of culture. The majority of CD14+ cells (>75%) differentiated into endothelial-like cells (ELC) on all biomaterials used. The expression of endothelial markers was similar to their expression on HUVEC. Since CD14+ cells are present in high numbers in adult peripheral blood, easy to isolate and because they easily differentiate into ELC on biomaterials, we conclude that CD14+ cells are a suitable cell source for progenitor-based vascular tissue engineering.