Mesenchyme homeobox 2 regulation of fetal endothelial progenitor cell function

Abstract

In the United States, 10% of pregnancies are complicated by diabetes mellitus (DM). Intrauterine DM exposure can have long-lasting implications for the fetus, including cardiovascular morbidity. Previously, we showed that fetal endothelial colony forming cells (ECFCs) from DM pregnancies have decreased vessel-forming ability and increased senescence. However, the molecular mechanisms responsible for this dysfunction remain largely unknown. The objective of this thesis was to understand how Mesenchyme Homeobox 2 (MEOX2) interacts with pathways that regulate cell cycle progression and migration, and how this interaction results in impaired vasculogenesis in DM exposed ECFCs. We tested the hypothesis that upregulated MEOX2 in DM-exposed ECFCs decreases network formation through impairments in senescence, cell cycle progression, migration, and adhesion. MEOX2 is a transcription factor which inhibits angiogenesis by upregulating cyclin dependent kinase inhibitors. Here, data show that nuclear MEOX2 is increased in DM-exposed ECFCs. Lentiviral-mediated overexpression of MEOX2 in control ECFCs increased network formation, altered cell cycle progression, increased senescence, and enhanced migration. In contrast, MEOX2-knockdown in DM-exposed ECFCs decreased network formation and migration, while cell cycle progression and senescence were unchanged. Adhesion and integrin expression defects were evaluated as mechanisms by which MEOX2 altered ECFC migration. While MEOX2-overexpression did not alter adhesion or cell surface integrin levels in control cells, MEOX2 overexpression in DM-exposed ECFCs resulted in an increase in α6 integrin surface expression. Similarly, MEOX2-knockdown in DM-exposed ECFCs did not alter adhesion, though did reduce α6 integrin surface expression and total cellular α6 mRNA and protein levels. Together, these data suggest that alterations in cell cycle progression and senescence are not responsible for the disrupted vasculogenesis of DM-exposed ECFCs. Importantly, these data suggest that altered migration may be a key mechanism involved and that altered cell surface levels of the α6 integrin may modify migratory capacity. Moreover, these data suggest that the α6 integrin may be a previously unrecognized transcriptional target of MEOX2. Ultimately, while initially believed to be maladaptive, these data suggest that increased nuclear MEOX2 in DM-exposed ECFCs may serve a protective role, enabling vessel formation despite exposure to a DM intrauterine environment.