A single-cell-based characterization of mammalian adipose stem and progenitor cell heterogeneity and function

White adipose tissue (WAT) is a cellularly heterogeneous endocrine organ that not only serves as a reservoir for storing and releasing energy but also actively participates in metabolic homeostasis. Given the current rise in obesity and its associated comorbidities worldwide, there is a great interest in better characterizing what drives the plasticity of this tissue. Single-cell RNA-sequencing (scRNAseq) has recently given the unprecedented opportunity to dissect the cellular landscape of adipose-tissue residing cells. It notably revealed that the previously believed homogeneous adipose stem and pro-genitor cell (ASPC) pool, is in fact composed of distinct subpopulations. One of these subpopulations, characterized by high expression of F3, encoding for CD142, revealed to be refractory to adipogenic differentiation. But even more surprisingly, CD142+ ASPCs were shown to modulate the differentia-tion of other ASPCs by suppressing their ability to become mature adipocytes. In light of the consider-able implication of these cells named Adipogenesis regulators, or Aregs, in adipose biology, we first set up to show the robustness of their molecular and functional phenotype across various experi-mental and sampling condition. Thereby, we uncovered that their identity appears in an age-dependent fashion, where CD142+ ASPCs isolated from pups pre-weaning have a high adipogenic pro-pensity. Subsequently, based on multi-omic and functional assays we showed that the inhibitory na-ture of Aregs is driven by specifically secreted factors that cooperate with retinoic acid signaling pathway to transform the adipogenic state of other ASPCs into a non-adipogenic, Areg-like state. On top of the high cellular complexity of adipose tissue and their stem niche, they also harbor key physiological differences depending on their anatomical locations, which have been shown to correlate with metabolic health when overgrown. While great progress has been made to characterize the features contrasting healthy versus pathological adipose tissue expansion, considerably less is known in terms of the molecular and cellular determinants of these phenotypes. Driven by the power of scRNAseq, we wondered if differences in the cellular landscape across depots could at least partly explain this depot-specific behavior. We found that while the main subpopulations of ASPCs are con-served across subcutaneous, perirenal, omentum, and mesocolic adipose tissues, they also harbor in-trinsic molecular and functional specificities. More strikingly, we identified an omentum-specific pop-ulation, potentially transitioning between mesothelial and mesenchymal cell types, able to negatively modulate the differentiation of other cells through the secretion of IGFBP2.