Characterization of Dedifferentiating Human Mature Adipocytes from the Visceral and Subcutaneous Fat Compartments: Fibroblast-Activation Protein Alpha and Dipeptidyl Peptidase 4 as Major Components of Matrix Remodeling

Abstract

Mature adipocytes can reverse their phenotype to become fibroblast-like cells. This is achieved by ceiling culture and the resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent. Beyond the potential value of these cells for regenerative medicine, the dedifferentiation process itself raises many questions about cellular plasticity and the pathways implicated in cell behavior. This work has been performed with the objective of obtaining new information on adipocyte dedifferentiation, especially pertaining to new targets that may be involved in cellular fate changes. To do so, omental and subcutaneous mature adipocytes sampled from severely obese subjects have been dedifferentiated by ceiling culture. An experimental design with various time points along the dedifferentiation process has been utilized to better understand this process. Cell size, gene and protein expression as well as cytokine secretion were investigated. Il-6, IL-8, SerpinE1 and VEGF secretion were increased during dedifferentiation, whereas MIF-1 secretion was transiently increased. A marked decrease in expression of mature adipocyte transcripts (PPARγ2, C/EBPα, LPL and Adiponectin) was detected early in the process. In addition, some matrix remodeling transcripts (FAP, DPP4, MMP1 and TGFβ1) were rapidly and strongly up-regulated. FAP and DPP4 proteins were simultaneously induced in dedifferentiating mature adipocytes supporting a potential role for these enzymes in adipose tissue remodeling and cell plasticity.

Unravelling the immunological roles of dipeptidyl peptidase 4 (DPP4) activity and/or structure homologue (DASH) proteins

“…In tumorigenic cells and wounds, this heteromeric complex is localised on the advancing portion of invadopodia that is believed to play an important role in tumour invasion, spreading of metastasis, angiogenesis and wound-healing, respectively [6,7,13,22]. Thus, to identify it as a pharmaceutical target, the expression of FAP has been investigated as potential biomarker in several types of cancers [6,7,13,[23][24][25]. Interestingly, it was shown that stromal FAP is more prominent in early-stage colorectal cancer and smaller tumour xenografts, with increased expression of FAP being an adverse prognostic indicator in patients with advanced metastatic disease [26].…”

Temporal Changes in Gene Expression Profile during Mature Adipocyte Dedifferentiation

“…However, in vitro studies have shown that mature adipocytes are able to return to a more primitive phenotype when they are subjected to ceiling culture [1]. In previous studies, we have shown that the dedifferentiation process is relatively independent of the fat depot, obesity level, sex, or age of the cell donor [2]. The fibroblast-like cells resulting from the process have a great potential for proliferation [1].…”

“…Cells lose their round shape and become elongated as they shed their lipid content. At day 12 of the process, cells have a fibroblastic appearance (Figure 1) [2]. In addition to morphological changes, some authors observed important modifications in the expression of genes associated with the adipogenic and lipogenic programs of mature adipocytes in DFAT cells.…”

“…We have previously corroborated these results by showing a significant decrease in PPARγ , CEBPA , and adiponectin (ADIPOQ) gene expression in DFAT cells compared to mature adipocytes. We also demonstrated that expression of genes encoding proteins implicated in extracellular matrix (ECM) remodeling including matrix-metalloproteinase 1 (MMP1) , fibroblast activated-protein (FAP) , dipeptidyl peptidase IV (DPP4) , and transforming growth factor β 1 (TGFβ1) was significantly upregulated during the dedifferentiation process [2]. …”

Expression of MMP-1, -2, and -8 in longissimus dorsi muscle and their relationship with meat quality traits in cattle

“…The remodeling of the ECM has important effects on differentiation of preadipocytes and their ability to accumulate triglyceride lipid droplets (Chun, 2012), which indicates that the expression of MMPs could regulate the IMF by remodeling the ECM of preadipocytes and fibroblasts. Interestingly, MMP-1 has been reported as the most up-regulated MMP during the differentiation of cultivated adipocytes (Lessard et al, 2015). MMP-2-deficient mice were more resistant to high-fat diet-induced weight gain than littermate wild-type mice (Van Hul and Lijnen, 2008), which indicates that MMP-2 is essential to deposit lipids in the body.…”