Multi-Level Analysis of Adipose Tissue Reveals the Relevance of Perivascular Subpopulations and an Increased Endothelial Permeability in Early-Stage Lipedema

Abstract

Lipedema is a chronic, progressive disease of adipose tissue with unknown etiology. Based on the relevance of the stromal vascular fraction (SVF) cell population in lipedema, we performed a thorough characterization of subcutaneous adipose tissue, SVF isolated thereof and the sorted populations of endothelial cells (EC), pericytes and cultured adipose-derived stromal/stem cells (ASC) of early-stage lipedema patients. We employed histological and gene expression analysis and investigated the endothelial barrier by immunofluorescence and analysis of endothelial permeability in vitro. Although there were no significant differences in histological stainings, we found altered gene expression of factors relevant for local estrogen metabolism (aromatase), preadipocyte commitment (ZNF423) and immune cell infiltration (CD11c) in lipedema on the tissue level, as well as in distinct cellular subpopulations. Machine learning analysis of immunofluorescence images of CD31 and ZO-1 revealed a morphological difference in the cellular junctions of EC cultures derived from healthy and lipedema individuals. Furthermore, the secretome of lipedema-derived SVF cells was sufficient to significantly increase leakiness of healthy human primary EC, which was also reflected by decreased mRNA expression of VE-cadherin. Here, we showed for the first time that the secretome of SVF cells creates an environment that triggers endothelial barrier dysfunction in early-stage lipedema. Moreover, since alterations in gene expression were detected on the cellular and/or tissue level, the choice of sample material is of high importance in elucidating this complex disease.

Lipedema: Insights into Morphology, Pathophysiology, and Challenges

“…A 3D culture-based study mimicked the AT microenvironment more suitably than the 2D culture and showed no significant difference in the expression of ADIPOQ, PPARG, and lipoprotein lipase (LPL) among lipedema and healthy controls [ 36 ]. Similar findings were obtained by Strohmeier et al, who reported that quantitative polymerase chain reaction (qPCR) analysis showed no significant difference in the expression of LEP, ADIPOQ, and fatty-acid-binding protein 4 (FABP4) in lipedema samples compared to controls [ 43 ]. In contradiction with these findings, qPCR gene-expression analysis of differentiated adipose-derived stem cells (ADSCs), obtained from the abdomens and thighs of lipedema patients and healthy lean subjects, showed higher mRNA expression of PPARG and LEP in lipedema ADSCs [ 44 ].…”

“…Another gene, cyclin D1 (CCND1), has been pinned down as a potential target contributing to the hyperplastic phenotype of lipedema AT due to its positive correlation with MCE [ 51 , 52 , 53 ]. Following these findings, Strohmeier et al observed the upregulation of zinc finger protein 423 (ZNF423) in the lipedema stromal vascular fraction (SVF) and lipedema tAT pericytes compared to the respective control groups [ 43 ]. ZNF423 plays a crucial role in early preadipocyte commitment by inducing PPARG expression through the bone morphogenetic protein (BMP) signaling axis.…”

“…Gene-expression analysis showed a higher expression of aromatase (CYP19A1)—responsible for the conversion of androgens to estrogen—in lipedema tAT compared to lean healthy control tAT and the abdominal AT of the same lipedema patient. However, estrogen-receptor gene-expression levels have been shown to be unaffected in lipedema [ 40 , 43 ]. In highly proliferative breast cancer cells, estrogen was found to induce ZNF423 expression, a TF that has been confirmed to be upregulated in lipedema [ 58 ].…”

“…Lipedema is characterized by insufficient backflow leading to excess fluid accumulated in the interstitium. The excess IF might be associated with adipocyte hypertrophy and hyperplasia, inadvertently leading to hypoxia, microangiopathy, and a higher permeability of endothelial capillaries [ 7 , 43 , 59 , 60 ]. Microangiopathy in tAT (not the abdomen) for lipedema has been confirmed, which is the reason for the increased permeability of the microvessels leading to excess IF.…”

Integrated Transcriptome and Metabolome Analysis Reveals the Regulatory Mechanisms of FASN in Geese Granulosa Cells

“…After FASN interference, two transcriptional subtypes of DEGs, namely, aromatase and 3βHSD , were enriched into the steroid hormone biosynthesis pathway in phGCs. These two enzymes are responsible for E 2 [ 18 ] and P 4 synthesis [ 19 ]. Therefore, it could be speculated that FASN interference might inhibit the steroidogenesis of phGCs.…”