VEGFR1 primes a unique cohort of dental pulp stem cells for vasculogenic differentiation

Dental pulp stem cells (DPSCs) constitute a unique group of cells endowed with multipotency, self-renewal, and capacity to regenerate the dental pulp tissue. While much has been learned about these cells in recent years, it is still unclear if each DPSC is multipotent or if unique sub-populations of DPSCs are "primed" to undergo specific differentiation paths. The purpose of the present study was to define whether a sub-population of DPSCs was uniquely primed to undergo vasculogenic differentiation. Permanent-tooth DPSCs or stem cells from human exfoliated deciduous teeth (SHED) were flow-sorted for vascular endothelial growth factor receptor 1 (VEGFR1) and exposed to vasculogenic differentiation medium, i.e., Microvascular-Endothelial-Cell-Growth-Medium-2-BulletKit™ supplemented with 50 ng/mL rhVEGF165 in the presence of 0 or 25 μg/mL anti-human VEGF antibody (bevacizumab; Genentech). In addition, sorted SHED (i.e., VEGFR1high or VEGFR1low) were seeded in biodegradable scaffolds and transplanted into the subcutaneous space of immunodeficient mice. Despite proliferating at a similar rate, VEGFR1high generated more in vitro sprouts than VEGFR1low cells (p < 0.05). Blockade of VEGF signaling with bevacizumab inhibited VEGFR1high-derived sprouts, demonstrating specificity of responses. Similarly, VEGFR1high SHED generated more blood vessels when transplanted into murine hosts than VEGFR1low cells (p < 0.05). Collectively, these data demonstrated that DPSCs contain a unique sub-population of cells defined by high VEGFR1 expression that are primed to differentiate into vascular endothelial cells. These data raise the possibility of purifying stem cells with high vasculogenic potential for regeneration of vascularized tissues or for vascular engineering in the treatment of ischemic conditions.