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<p id="p1">Despite extensive research during the last couple of years, lipedema still appears enigmatic in respect to its pathogenesis. In our in vitro study, we have set out to further characterize lipedema adipocytes, concentrating on gene and protein expression, which might help to develop ideas explaining the excessive accumulation of adipose tissue in women with lipedema. Using 2D cultures we show that gene expression in lipedema and non-lipedema adipocytes differs significantly in terms of genes related to lipid droplet size determination, insulin signaling and glucose uptake. A pronounced hypertrophy, recognizable by a significantly increased average lipid droplet size, was visible in differentiated lipedema adipocytes grown in 3D cultures. In addition, gene and protein expression related to inflammation and fibrosis were upregulated in lipedema adipocytes compared to controls, supporting earlier reports. Taken together, results from our in vitro studies suggest that lipedema adipose cells are capable of retaining their hypertrophic nature under culture conditions and open new aspects focusing on insulin signaling and PDGFRA-mediated balancing of adipogenic versus fibrogenic differentiation of lipedema adipose tissue.</p>

When studying the current literature, one might get the impression that lipedema is a “modern” disease, with increasing incidence and augmenting prevalence throughout Western countries during the last decade. However, a quick look into older textbooks shows that disproportionate accumulation of fat in female bodies has long been known without being recognized as an independent disease. Nevertheless, it was not until 1940 that Allen and Hines described a “syndrome characterized by fat legs and orthostatic edema” in a seminal publication. The mere awareness that people who have lipedema are not just overweight but suffer from a yet poorly defined pathological condition, may be considered a decisive leap forward in the understanding of lipedema. A number of comprehensive publications have since dealt with the clinical presentation of lipedema and have provided the first clues towards the potential pathological mechanisms underlying its initiation and progression. Nevertheless, despite all effort that has been undertaken to unravel lipedema pathology, many questions have remained unanswered. What can be deduced with certainty from all experimental and medical evidence available so far is that lipedema is neither a cosmetic problem nor is it a problem of lifestyle but should be accepted as a serious disease with yet undetermined genetic background, which makes women’s lives unbearable from both a physical and psychological point of view. To date, results from clinical inspections have led to the categorization of various types and stages of lipedema, describing how the extremities are affected and evaluating its progression, as demonstrated by skin alterations, adipose tissue volume increase and physical and everyday-behavioral impediments. There is accumulating evidence showing that advanced stages of lipedema are usually accompanied by excessive weight or obesity. Thus, it is not unreasonable to assume that the progression of lipedema is largely driven by weight gain and the pathological alterations associated with it. Similarly, secondary lymphedema is frequently found in lipedema patients at advanced stages. Needless to say, both conditions considerably blur the clinical presentation of lipedema, making diagnosis difficult and scientific research challenging. The present literature review will focus on lipedema research, based on evidence fromex vivo and in vitro data, which has accumulated throughout the last few decades. We will also open the discussion as to whether the currently used categorization of lipedema stages is still sufficient and up-to-date for the accurate description of this enigmatic disease, whose name, strangely enough, does not match its pathologic correlate.

BACKGROUND: Lipedema is characterized by localized accumulation of fat in the extremities, which is typically unresponsive to dietary regimens or physical activity. Although the disease is well described and has a high incidence, little is known regarding the molecular and cellular mechanisms underlying its pathogenesis. The aim of this study was to investigate the pathophysiology of lipedema adipose cells in vitro. METHODS: Adipose-derived stem cells were isolated from lipoaspirates derived from lipedema and nonlipedema patients undergoing tumescent liposuction. In vitro differentiation studies were performed for up to 14 days using adipogenic or regular culture medium. Supernatants and cell lysates were tested for adiponectin, leptin, insulin-like growth factor-1, aromatase (CYP19A1), and interleukin-8 content at days 7 and 14, using enzyme-linked immunosorbent assays. Adipogenesis was evaluated by visualizing and measuring cytoplasmic lipid accumulation. RESULTS: Lipedema adipose-derived stem cells showed impeded adipogenesis already at early stages of in vitro differentiation. Concomitant with a strongly reduced cytoplasmic lipid accumulation, significantly lower amounts of adiponectin and leptin were detectable in supernatants from lipedema adipose-derived stem cells and adipocytes compared with control cells. In addition, lipedema and nonlipedema cells differed in their expression of insulin-like growth factor-1, aromatase (CYP19A1), and interleukin-8 and in their proliferative activity. CONCLUSIONS: The authors' findings indicate that in vitro adipogenesis of lipedema adipose-derived stem cells is severely hampered compared with nonlipedema adipose-derived stem cells. Lipedema adipose cells differ not only in their lipid storage capacity but also in their adipokine expression pattern. This might serve as a valuable marker for diagnosis of lipedema, probably from an early stage on.

BACKGROUND: Lipedema is a progressive disease, diagnosed most often in women, which is characterized by the unproportionate and symmetrical distribution of adipose tissue primarily in the extremities. Despite numerous results from in vitro and in vivo studies, many questions regarding the pathology and genetic background of lipedema have remained unanswered. METHODS: Adipose tissue-derived stromal/stem cells (ASCs) were isolated from lipoaspirates derived from non-obese and obese lipedema and non-lipedema donors. Growth/morphology, metabolic activity, differentiation potential and gene expression were evaluated using quantification of lipid accumulation, metabolic activity assay, live-cell imaging, RT-PCR, quantitative PCR and immunocytochemical staining. RESULTS: The adipogenic potential of lipedema and non-lipedema ASCs did not rise in parallel with the donors' BMI and did not differ significantly between groups. However, in vitro differentiated adipocytes from non-obese lipedema donors showed significant upregulation of adipogenic gene expression compared to non-obese controls. All other genes tested were equally expressed in lipedema and non-lipedema adipocytes. The ADIPOQ/LEP ratio (ALR) was significantly reduced in adipocytes from obese lipedema donors compared to their non-obese lipedema counterparts. Increased stress fiber-integrated SMA was visible in lipedema adipocytes compared to non-lipedema controls and appeared enhanced in adipocytes from obese lipedema donors. CONCLUSIONS: Not only lipedema per se but also BMI of donors impact adipogenic gene expression substantially in vitro. The significantly reduced ALR and the increased occurrence of myofibroblast-like cells in "obese" lipedema adipocyte cultures underlines the importance of attention towards the co-occurrence of lipedema and obesity. These are important findings towards accurate diagnosis of lipedema.