Human umbilical cord blood-derived f-macrophages retain pluripotentiality after thrombopoietin expansion

We have previously characterized a new type of stem cell from human peripheral blood, termed fibroblast-like macrophage (f-MΦ). Here, using umbilical cord blood as a source, we identified cells with similar characteristics including expression of surface markers (CD14, CD34, CD45, CD117, and CD163), phagocytosis, and proliferative capacity. Further, thrombopoietin (TPO) significantly stimulated the proliferation of cord blood-derived f-MΦ (CB f-MΦ) at low dosage without inducing a megakaryocytic phenotype. Additional experiments demonstrated that TPO-expanded cord blood-derived f-MΦ (TCB f-MΦ) retained their surface markers and differentiation ability. Treatment with vascular endothelial cell growth factor (VEGF) gave rise to endothelial-like cells, expressing Flt-1, Flk-1, von Willebrand Factor (vWF), CD31, acetylated low density lipoprotein internalization, and the ability to form endothelial-like cell chains. In the presence of lipopolyssacharide (LPS) and 25 mM glucose, the TCB f-MΦ differentiated to express insulin mRNA, C-peptide, and insulin. In vitro functional analysis demonstrated that these insulin-positive cells could release insulin in response to glucose and other secretagogues. These findings demonstrate a potential use of CB f-MΦ and may lead to develop new therapeutic strategy for treating dominant disease.