ESPE Yearbook of Paediatric Endocrinology

To read the full abstract: Cell Rep 2019; 27(5): 1528–40

These authors used FACS cell sorting, gene expression profiling, and metabolic and proteomic analyses to identify three distinct adipocyte progenitor cell (APCs) subtypes that reside in human white adipose tissues. Although they retain comparable differentiation capacity, they have different molecular profiles and give rise to adipocytes with divergent metabolic and endocrine features.

It is well established that different types of APCs exist, however, their molecular identities, e.g. cell surface markers, are not well defined. The International Fat Applied Technology Society (IFATS) defines an adipose derived stem cells as CD45-/CD235a-/CD31-/CD34+ cells, which represent approximately 20% of the whole stroma-vascular fraction (1) of white adipose tissue. Whilst CD34 was long used as a cell surface marker for the hematopoietic cell fraction, it is now considered to be a marker of adipose tissue stemness (2). It should be mentioned that CD34 expression is dynamic in cell culture; adherent cells lose this marker upon prolonged cultivation (2).

Here, the authors defined three subpopulations of APCs, dependent on CD34 expression before seeding: CD34 high; CD34 low; and CD34 negative APCs. Adipocytes which differentiated in vitro from high CD34 APCs showed extremely high rates of lipid flux compared with low CD34 APCs or CD34 negative APCs. By contrast, adipocytes derived from CD34 negative APCs displayed beige-like adipocyte properties and a unique endocrine profile. APCs were more abundant in gluteofemoral than abdominal subcutaneous and omental adipose tissues, but similar distribution patterns were found of APC subtypes between these adipose tissue depots and similar metabolic traits of these APC subtypes. The distribution of APC subtypes varied between depots and in patients with Type 2 diabetes.

In summary, this paper shows convincingly that adipocytes from three APC subtypes have distinct metabolic and endocrine profiles. The data suggest that enrichment of a certain adipocyte cell type may influence whole-body metabolism. Indeed, distribution of ASC subpopulations was altered in Type 2 diabetic patients. If this holds true, distribution of ASCs in adipose tissue might also help to predict disease development.

References: 1. Bourin P, Bunnell BA, Casteilla L, Dominici M, Katz AJ, March KL, et al. Stromal cells from the adipose tissue-derived stromal vascular fraction and culture expanded adipose tissue-derived stromal/stem cells: a joint statement of the International Federation for Adipose Therapeutics and Science (IFATS) and the International Society for Cellular Therapy (ISCT). Cytotherapy. 2013;15(6):641–8.

2. Baer PC. Adipose-derived mesenchymal stromal/stem cells: an update on their phenotype in vivo and in vitro. World Journal of Stem Cells. 2014;6(3):256–65.