Adipose stromal-vascular fraction-derived paracrine factors regulate adipogenesis

Visceral and subcutaneous adipose tissue depots have distinct features and contribute differentially to metabolic disease. Therefore, the adipogenic potential of different fat depots was investigated and found to be higher in subcutaneous compared with visceral stromal-vascular fraction (SVF), which contains adipocyte precursor cells. This increased differentiation capacity was not due to elevated numbers of Lin-Sca1+CD29+CD34+Pref1+ precursor cells, as the number of preadipocytes was higher in visceral than in subcutaneous SVF. The secreted heat-sensitive factors from the SVF inhibited adipocyte differentiation more in visceral than in subcutaneous SVF. In order to explore secreted proteins that potentially inhibit differentiation, the secretome of murine SVF was analyzed by mass spectrometry, which resulted in the identification of 113 secreted proteins with an overlap of 42 % between subcutaneous and visceral SVF. Comparison of the mRNA expression in SVF from both depots revealed 16 transcripts that were significantly expressed more in visceral than in subcutaneous SVF. A functional differentiation screen identified seven potential inhibitory candidates: biglycan, decorin, bone morphogenic protein 1, epidermal growth factor-containing fibulin-like extracellular matrix protein 2, elastin microfibril interfacer 1, matrix gla protein, and Sparc-like 1. For further verification, murine recombinant decorin or Sparc-like 1 was added to the media during the differentiation process leading to a dose-dependent decrease in adipogenesis. Further analysis will be necessary to assess the impact of the other candidates on adipocyte differentiation.