Expansion of adipose tissue leading to obesity is associated with metabolic diseases, such as type 2 diabetes. However, not all adipose tissue is the same. Expansion of visceral (VAT) and abdominal subcutaneous (ASAT) adipose tissues is associated with metabolic disease and, in contrast, expansion of gluteal-femoral (GFAT) adipose tissue most likely protects against metabolic disease. Whether these differences in metabolism are due to intrinsic, cell-autonomous properties is unknown. Hence, we aimed to identify the adipocyte progenitor cells (APCs) present in the tissues and assess their metabolic properties.
We isolated APCs from the stromal vascular fraction (SVF) of human VAT, ASAT and GFAT based on the expression of cluster differentiation (CD) markers through Fluorescent Activated Cells Sorting (FACS). APCs were identified as CD31-CD45-CD29+CD34+. The number of APCs in each depot was determined by FACS analysis. The in vitro adipogenic potential of APCs was analysed by Oil-Red-O staining of lipids and quantifying the adipogenic gene expression by qPCR.
The number of SVF cells in GFAT (2.3 x 106/g) was higher (n=9, P=0.001) than in VAT (1.4 x 106/g) and ASAT (1.3 x 106/g) by 39.1 and 43.5%, respectively. The number of APCs in GFAT (0.2 x 106/g) was also higher (n=7, P=0.007) compared with APCs in VAT (0.1 x 106/g; 50%) and ASAT (0.09 x 106/g; 55%). The number of lymphocytes was highest in VAT (n=8, P=0.01), being 66.7% greater than in GFAT SVF. Purified APCs from VAT were more adipogenic in vitro than heterogenic VAT SVF cells as visualized through more Oil Red O staining and increased expression of the adipogenic genes, PLIN1 (56.6%) and AP2 (53.1%).
In conclusion, we have identified a bona fide APC population in human adipose tissues. The results demonstrate that these APCs are more highly populated in GFAT compared with VAT and ASAT.