“The preadipocyte factor” DLK1 marks adult mouse adipose tissue residing vascular cells that lack in vitro adipogenic differentiation potential

Delta‐like 1 (Dlk1) is expressed in 3T3‐L1 preadipocytes and has frequently been referred to as “the” preadipocyte marker, yet the phenotype of DLK1 + cells in adipose tissue remains undetermined. Herein, we demonstrate that DLK1 + cells encompass around 1–2% of the adult mouse adipose stromal vascular fraction (SVF). Unexpectedly, the DLK1 + SVF population was enriched for cells expressing genes generally ascribed to the vascular lineage and did not possess any adipogenic differentiation potential in vitro. Instead, DLK1 + cells comprised an immediate ability for cobblestone formation, generation of tube‐like structures on matrigel, and uptake of Acetylated Low Density‐Lipoprotein, all characteristics of endothelial cells. We therefore suggest that DLK1 + SVF cells are of a vascular origin and not them‐selves committed preadipocytes as assumed hitherto.