Cellular and molecular features of lipoma tissue: comparison with normal adipose tissue

Adipose and lipoma stem cells: A donor-matched comparison

Lipomas are slow growing benign fat tumors that develop in soft tissues of the mesoderm. Thus, the specific (dys-)function of mesenchymal stem cells (MSCs) has been suggested in the development of lipomas, but details of the tumor pathogenesis remain unclear. Existing studies comparing stem cells from native adipose (adipose stem cells [ASCs]) and lipomatous tissues (LSCs) have reported contradicting findings. However, harvesting ASCs and LSCs from different individuals might have influenced proper comparison. Therefore, we aimed to characterize donor-matched ASCs and LSCs to investigate metabolic activity, proliferation, capability for tri-linear differentiation (chondrogenesis, adipogenesis, osteogenesis), and the secretome of mature adipocytes and lipomacytes. Both stem cell types did not differ in metabolic activity, but ASCs demonstrated stronger proliferation than LSCs. While there was no difference in proteoglycan accumulation during chondrogenic differentiation, adipogenesis was higher in ASCs, with more lipid vacuole formation. Conversely, LSCs showed increased osteogenesis by higher calcium deposition. Lipomacytes showed stronger secretory activity and released higher levels of certain adipokines. Our findings indicated that LSCs possessed important characteristics of MSCs, including ASCs. However, LSCs' low proliferation and adipogenic differentiation behavior did not appear to account for enhanced tissue proliferation, but the secretome of lipomacytes could contribute to lipomatous neoplasm.

Expression profiles of exosomal tRNA-derived fragments and their biological functions in lipomas

There is evidence that exosomes derived from the lipoma tissue (Exo-LT) have a stronger capacity to promote the proliferation and migration of adipose-derived stem cells (ADSCs) than those from the adipose tissue (Exo-AT). But the Exo-LT do not have a significant effect on the adipogenic differentiation of the ADSCs. Recently, certain exosomal tRNA-derived fragments (tRFs) have been shown to play a crucial role in the pathogenesis of certain tumors. Therefore, it is necessary to identify the differently expressed tRFs in Exo-LT to further elucidate their molecular functions in lipomas. High-throughput sequencing was performed to examine the tRFs and mRNAs from the all samples belonging to the Exo-LT and Exo-AT groups. Target prediction and bioinformatics analysis were performed to explore their downstream mRNAs and biological functions. In total, 456 differently expressed tRFs and tiRNAs were identified in the Exo-LT group, 12 of which were up-regulated and 12 were down-regulated, respectively. Notably, tRF-1001 was most obviously down-regulated and tRF-3004a was most obviously up-regulated in the Exo-LT group. Moreover, among the target genes of tRF-1001 and tRF-3004a, both JAG2 and VSIG4 were significantly down-regulated in the Exo-LT group, while WNT5A, COL1A1, and PPARGC1A were highly expressed in both the Exo-LT and Exo-AT groups. The significant down-regulation of JAG2 and VSIG4 in the Exo-LT group could be due to the fact that Exo-LT had a stronger capacity to promote the proliferation and migration of ADSCs compared to the Exo-AT. The high expression of WNT5A, COL1A1, and PPARGC1A in both the Exo-LT and Exo-AT groups could be due to the similar ability of Exo-LT and Exo-AT to promote the adipogenic differentiation of ADSCs.

Genetic and cytometric analyses of subcutaneous adipose tissue in patients with hemophilia and HIV-associated lipodystrophy

Background

The authors recently performed plastic surgeries for a small number of patients with hemophilia, HIV infection, and morphologic evidence of lipodystrophy. Because the pathophysiological mechanism of HIV-associated lipodystrophy remains to be elucidated, we analyzed subcutaneous adipose tissues from the patients.

Methods

All six patients had previously been treated with older nucleoside analogue reverse-transcriptase inhibitors (NRTIs; stavudine, didanosine or zidovudine). Abdominal and inguinal subcutaneous fat samples were obtained from the HIV+ patients with hemophilia and HIV− healthy volunteers (n = 6 per group), and analyzed via DNA microarray, real-time PCR, flow cytometry and immunohistochemistry.

Results

The time from initial NRTI treatment to collecting samples were 21.7 years in average. Cytometric analysis revealed infiltration of inflammatory M1 macrophages into HIV-infected adipose tissue and depletion of adipose-derived stem cells, possibly due to exhaustion following sustained adipocyte death. Genetic analysis revealed that adipose tissue from HIV+ group had increased immune activation, mitochondrial toxicity, chronic inflammation, progressive fibrosis and adipocyte dysfunction (e.g. insulin resistance, inhibited adipocyte differentiation and accelerated apoptosis). Of note, both triglyceride synthesis and lipolysis were inhibited in adipose tissue from patients with HIV.

Conclusions

Our findings provide important insights into the pathogenesis of HIV-associated lipodystrophy, suggesting that fat redistribution may critically depend on adipocytes’ sensitivity to drug-induced mitochondrial toxicity, which may lead either to atrophy or metabolic complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12981-022-00432-9.

Effect of Tranexamic Acid Administration on Postoperative Ecchymosis and Edema in Excision of Lipomas

BACKGROUND

Previous studies have shown that systemic tranexamic acid reduces bleeding during soft tissue surgeries and reduces postoperative ecchymosis and edema experienced by surgical patients.

OBJECTIVE

To evaluate the effect of postoperative tranexamic acid administration on the reduction of ecchymosis and edema after lipoma surgery.

MATERIALS AND METHODS

A total of 40 patients who underwent lipoma excision were included in the comparative analysis. In the tranexamic acid group (n = 20), 1 g of tranexamic acid was administered daily for 5 consecutive postoperative days. Tranexamic acid was not administered to the control group (n = 20). The severity of ecchymosis and edema at the first visit after surgery was rated on a 4-point scale by 2 blinded dermatologists.

RESULTS

The mean interval of the initial visit after surgery was 1.1 ± 0.5 (range: 1-4) days. Mean ecchymosis scores were significantly lower in the tranexamic acid group (0.5 ± 0.8) than in the control group (1.2 ± 1.0) (p < .05). No statistical difference was seen in mean edema scores between groups (0.5 ± 0.6 in tranexamic acid vs 0.7 ± 0.8 in control).

CONCLUSION

We observed that postoperative administration of tranexamic acid significantly decreased ecchymosis in lipoma excision.

Therapeutic potential of small extracellular vesicles derived from lipoma tissue in adipose tissue regeneration-an in vitro and in vivo study

OBJECTIVE

To explore the adipogenic effects of the small extracellular vesicles derived from the lipoma tissues (sEV-LT), and to find a new cell-free therapeutic approach for adipose tissue regeneration.

METHODS

Adipose tissue-derived stem cells (ADSCs) and small extracellular vesicles derived from the adipose tissues (sEV-AT) were isolated from human adipose tissue, while sEV-LT were isolated from human lipomatous tissue. ADSCs were characterized by using flow cytometric analysis and adipogenic and osteogenic differentiation assays. sEV was identified by electron microscopy, nanoparticle tracking, and western blotting. ADSCs were treated with sEV-LT and sEV-AT, respectively. Fluorescence confocal microscopy was used to investigate whether sEV-LT and sEV-AT could be taken by ADSCs. The proliferation and migration abilities and adipogenic differentiation assay of ADSCs were evaluated by CCK-8 assays, scratch test, and oil red O staining test, and the expression levels of adipogenic-related genes C/EBP-δ, PPARγ2, and Adiponectin in ADSCs were assessed by real-time quantitative PCR (RT-PCR). The sEV-LT and sEV-AT transplantation tubes were implanted subcutaneously in SD rats, and the neotissues were qualitatively and histologically evaluated at 2, 4, 8, and 12 weeks after transplantation. Hematoxylin and eosin (H&E) staining was subsequently used to observe and compare the adipogenesis and angiogenesis in neotissues, while immunohistochemistry was used to examine the expression and the distribution of C/EBP-α, PPARγ, Adiponectin, and CD31 at the 4th week.

RESULTS

The in vitro experiments showed that both sEV-LT and sEV-AT could be taken up by ADSCs via endocytosis. The scratch experiment and CCK-8 experiment showed that the migration area and proliferation number of ADSCs in sEV-LT group and sEV-AT group were significantly higher than those in the non-sEV group (p < 0.05). Compared with sEV-AT group, sEV-LT group had larger migration area and proliferation number of ADSCs (p < 0.05). Oil red O staining and RT-PCR experiments showed that, compared with the non-sEVs group, the lipid droplets and the mRNA expression levels of adipogenesis-related genes PPARγ2 and Adiponectin of ADSCs in sEV-LT group and sEV-AT group were significantly upregulated (p < 0.05); however, there was no statistical significance in the expression level of C/EBP-δ (p > 0.05). In addition, no significant difference in the amount of lipid droplets and adipogenesis-related genes between the sEV-LT groups and sEV-AT was seen (p > 0.05). At 2, 4, 8, and 12 weeks, the adipocyte area and the number of capillaries in neotissues in the sEV-LT groups and sEV-AT groups were significantly increased compared with the Matrigel group (p < 0.05); however, there was no dramatic difference between sEV-LT groups and sEV-AT groups (p > 0.05). At the 4th week, neotissues in the sEV-LT groups and sEV-AT groups all showed upregulated expression of C/EBP-α, PPARγ, Adiponectin, and CD31 protein, while neotissues in the Matrigel group only showed positive expression of CD31 protein.

CONCLUSIONS

This study demonstrated that sEV-LT exerted promotion effects on adipose tissue regeneration by accelerating the proliferation, migration, and adipogenic differentiation of ADSCs in vitro and recruiting adipocytes and promoting angiogenesis in vivo. The sEV-LT could serve as an alternative cell-free therapeutic strategy for generating adipose tissue, thus providing a promising application prospect in tissue engineering.

D-Mannose Inhibits Adipogenic Differentiation of Adipose Tissue-Derived Stem Cells via the miR669b/MAPK Pathway

The adipogenic differentiation of adipose tissue-derived stem cells (ADSCs) plays an important role in the process of obesity and host metabolism. D-Mannose shows a potential regulating function for fat tissue expansion and glucose metabolism. To explore the mechanisms through which D-mannose affects the adipogenic differentiation of adipose-derived stem cells in vitro, we cultured the ADSCs with adipogenic medium inducement containing D-mannose or glucose as the control. The adipogenic differentiation specific markers Pparg and Fabp4 were determined by real-time PCR. The Oil Red O staining was applied to measure the lipid accumulation. To further explore the mechanisms, microarray analysis was performed to detect the differences between glucose-treated ADSCs (G-ADSCs) and D-mannose-treated ADSCs (M-ADSCs) in the gene expression level. The microarray data were further analyzed by a Venn diagram and Gene Set Enrichment Analysis (GSEA). MicroRNA inhibitor transfection was used to confirm the role of key microRNA. Results. D-Mannose intervention significantly inhibited the adipogenic differentiation of ADSCs, compared with the glucose intervention. Microarray showed that D-mannose increased the expression of miR669b, which was an inhibitor of adipogenesis. In addition, GSEA and western blot suggested that D-mannose suppressed the adipogenic differentiation via inhibiting the MAPK pathway and further inhibited the expression of proteins related to glucose metabolism and tumorigenesis. Conclusion. D-Mannose inhibits adipogenic differentiation of ADSCs via the miR669b/MAPK signaling pathway and may be further involved in the regulation of glucose metabolism and the inhibition of tumorigenesis.

A new human adipocyte model with PTEN haploinsufficiency

Few human cell strains are suitable and readily available as in vitro adipocyte models. We used resected lipoma tissue from a patient with germline phosphatase and tensin homolog (PTEN) haploinsufficiency to establish a preadipocyte cell strain termed LipPD1 and aimed to characterize cellular functions and signalling pathway alterations in comparison to the established adipocyte model Simpson-Golabi-Behmel-Syndrome (SGBS) and to primary stromal-vascular fraction cells. We found that both cellular life span and the capacity for adipocyte differentiation as well as adipocyte-specific functions were preserved in LipPD1 and comparable to SGBS adipocytes. Basal and growth factor-stimulated activation of the PI3 K/AKT signalling pathway was increased in LipPD1 preadipocytes, corresponding to reduced PTEN levels in comparison to SGBS cells. Altogether, LipPD1 cells are a novel primary cell model with a defined genetic lesion suitable for the study of adipocyte biology.

Reduced lipolysis in lipoma phenocopies lipid accumulation in obesity

BACKGROUND

Elucidation of lipid metabolism and accumulation mechanisms is of paramount importance to understanding obesity and unveiling therapeutic targets. In vitro cell models have been extensively used for these purposes, yet, they do not entirely reflect the in vivo setup. Conventional lipomas, characterized by the presence of mature adipocytes and increased adipogenesis, could overcome the drawbacks of cell cultures. Also, they have the unique advantage of easily accessible matched controls in the form of subcutaneous adipose tissue (SAT) from the same individual. We aimed to determine whether lipomas are a good model to understand lipid accumulation.

METHODS

We histologically compared lipomas and control SAT, followed by assessment of the lipidome using high-resolution ¹H NMR spectroscopy and ESI-IT mass spectrometry. RNA-sequencing was used to obtain the transcriptome of lipomas and the matched SAT.

RESULTS

We found a significant increase of small-size (maximal axis < 70 µm) and very big (maximal axis > 150 µm) adipocytes within lipomas. This suggests both enhanced adipocyte proliferation and increased lipid accumulation. We further show that there is no significant change in the lipid composition compared to matched SAT. To better delineate the pathophysiology of lipid accumulation, we considered two groups with different genetic backgrounds: (1) lipomas with HMGA2 fusions and (2) without gene fusions. To reduce the search space for genes that are relevant for lipid pathophysiology, we focused on the overlapping differentially expressed (DE) genes between the two groups. Gene Ontology analysis revealed that DE genes are enriched in pathways related to lipid accumulation.

CONCLUSIONS

We show that the common shared lipid accumulation mechanism in lipoma is a reduction in lipolysis, with most gene dysregulations leading to a reduced cAMP in the adipocyte. Superficial lipomas could thus be used as a model for lipid accumulation through altered lipolysis as found in obese patients.

Comparison of Properties of Stem Cells Isolated from Adipose Tissue and Lipomas in Dogs

Adipose-derived mesenchymal stem cells (ADSCs) have been suggested their benefits in regenerative medicine for various diseases. Lipomas, benign neoplasms in adipose tissue, have been reported as a potential source of stem cells. These lipoma-derived mesenchymal stem cells (LDSCs) may be useful for regenerative medicine. However, the detailed characteristics of LDSCs have not been fully elucidated. This study investigated the cellular proteomics and secretomes of canine LDSCs in addition to morphology and proliferation and differentiation capacities. Some LDSCs isolated from canine subcutaneous lipomas were morphologically different from ADSCs and showed a rounded shape instead of fibroblast-like morphology. The phenotype of cell surface markers in LDSCs was similar to those in ADSCs, but CD29 and CD90 stem cell markers were more highly expressed compared with those of ADSCs. LDSCs had noticeably high proliferation ability, but no significant differences were observed compared with ADSCs. In regard to differentiation capacity compared to ADSCs, LDSCs showed higher adipogenesis, but no differences were observed with osteogenesis. Cellular proteomic analysis using two-dimensional gel electrophoresis revealed that over 95% of protein spots showed similar expression levels between LDSCs and ADSCs. Secretome analysis was performed using iTRAQ and quantitative cytokine arrays. Over 1900 proteins were detected in conditioned medium (CM) of LDSCs and ADSCs, and 94.0% of detected proteins showed similar expression levels between CM of both cell types. Results from cytokine arrays including 20 cytokines showed no significant differences between CM of LDSCs and that of ADSCs. Our results indicate that canine LDSCs had variability in characteristics among individuals in contrast with those of ADSCs. Cellular proteomics and secretomes were similar in both LDSCs and ADSCs. These findings suggest that LDSCs may be suitable for application in regenerative medicine.

Investigation of stemness and multipotency of equine adipose-derived mesenchymal stem cells (ASCs) from different fat sources in comparison with lipoma

BACKGROUND

Adipose tissue-derived mesenchymal stem cells (ASCs) offer a promising cell source for therapeutic applications in musculoskeletal disorders. The appropriate selection of ASCs from various fat depots for cell-based therapy is challenging. The present study aims to compare stemness and multipotency of ASCs derived from retroperitoneal (RP), subcutaneous (SC), and lipoma (LP) fat to assess their usefulness for clinical application.

METHODS

Equine ASCs from the three fat tissue sources were isolated and characterized. The cell viability, proliferation, and self-renewal were evaluated using MTT, sulforhodamine B, and colony forming unit (CFU) assays. Stem cell relative marker CD44, CD90, and CD105 and tumor marker CA9 and osteopontin (OPN) expression were quantified using RT-qPCR. Multipotency of ASCs for adipogenic, osteogenic, and chondrogenic differentiation was examined by quantifying Oil Red O and Alizarin Red S staining, alkaline phosphatase activity (ALP), and expression of differentiation relative markers. All data were statistically analyzed using ANOVA.

RESULTS

RP fat-derived ASCs showed a higher cell proliferation rate compared to SC and LP derived cells. In contrast, ASCs from lipoma displayed a lower proliferation rate and impaired CFU capacities. The expression of CD44, CD90, and CD105 was upregulated in RP and SC derived cells but not in LP cells. RP fat-derived cells displayed a higher adipogenic potential compared to SC and LP cells. Although ASCs from all fat sources showed enhanced ALP activity following osteogenic differentiation, SC fat-derived cells revealed upregulated ALP and bone morphogenetic protein-2 expression together with a higher calcium deposition. We found an enhanced chondrogenic potency of RP and SC fat-derived cells as shown by Alcian blue staining and upregulation of aggrecan (Aggre), cartilage oligomeric matrix protein precursor (COMP), and collagen 2a1 (Col2a1) expression compared to LP. The expression of OPN and CA9 was exclusively upregulated in the ASCs of LP.

CONCLUSIONS

The results provide evidence of variation in ASC performance not only between normal fat depots but also compared to LP cells which suggest a different molecular regulation controlling the cell fate. These data provided are useful when considering a source for cell replacement therapy in equine veterinary medicine.

Identification of somatic alterations in lipoma using whole exome sequencing

Lipomas are benign fatty tumors with a high prevalence rate, mostly found in adults but have a good prognosis. Until now, reason for lipoma occurrence not been identified. We performed whole exome sequencing to define the mutational spectrum in ten lipoma patients along with their matching control samples. We presented genomic insight into the development of lipomas, the most common benign tumor of soft tissue. Our analysis identified 412 somatic variants including missense mutations, splice site variants, frameshift indels, and stop gain/lost. Copy number variation analysis highlighted minor aberrations in patients. Kinase genes and transcriptions factors were among the validated mutated genes critical for cell proliferation and survival. Pathway analysis revealed enrichment of calcium, Wnt and phospholipase D signaling in patients. In conclusion, whole exome sequencing in lipomas identified mutations in genes with a possible role in development and progression of lipomas.

The Effect of Conditioned Media of Stem Cells Derived from Lipoma and Adipose Tissue on Macrophages' Response and Wound Healing in Indirect Co-culture System In Vitro

Immunomodulatory and wound healing activities of adipose-derived stem cells (ADSCs) have been reported in various in vitro and in vivo experimental models suggesting their beneficial role in regenerative medicine and treatments of inflammatory-related disorders. Lipoma-derived stem cells (LDSCs) were reported as a potential tool in regenerative medicine due to the similarity with ADSCs but we have previously shown that LDSCs have different differentiation capacity than ADSCs despite a similar mesenchymal phenotype. To further analyze the potential differences and/or similarities between those two stem cell types, in the present study we examined the macrophages (MΦs)’ response, immunomodulatory and wound healing effect of conditioned media (CM) of LDSCs and ADSCs in indirect co-culture system in vitro. We confirmed similar mesenchymal phenotype and stemness state of LDSCs and ADSCs but indicated differences in expression of some inflammatory-related genes. Anti-inflammatory potential of CM of LDSCs and ADSCs, with pronounced effect of LDSCs, in unstimulated RAW 264.7 MΦs was evaluated by decrease in Tnf and increase in Il10 gene expression, which was confirmed by corresponding cytokines’ secretion analysis. Conditioned media of both LDSCs and ADSCs led to the functional activation of MΦs, with slightly more pronounced effect of CM of LDSCs, while both stimulated wound healing in vitro in a similar manner. Results of this study suggest that LDSCs secrete soluble factors like ADSCs and therefore may have a potential for application in regenerative medicine, due to immunomodulatory and wound healing activity, and indicate that LDSCs through secretome may interact with other cells in lipoma tissue.

Stem Cells Derived from Lipoma and Adipose Tissue-Similar Mesenchymal Phenotype but Different Differentiation Capacity Governed by Distinct Molecular Signature

Lipomas are benign adipose tissue tumors of unknown etiology, which can vary in size, number, body localization and cell populations within the tissue. Lipoma-derived stem cells (LDSCs) are proposed as a potential tool in regenerative medicine and tissue engineering due to their similar characteristics with adipose-derived stem cells (ADSCs) reported so far. Our study is among the first giving detailed insights into the molecular signature and differences in the differentiation capacity of LDSCs in vitro compared to ADSCs. Mesenchymal stem cell phenotype was analyzed by gene expression and flow cytometric analysis of stem cell markers. Adipogenesis and osteogenesis were analyzed by microscopic analysis, cytochemical and immunocytochemical staining, gene and protein expression analyses. We showed that both LDSCs and ADSCs were mesenchymal stem cells with similar phenotype and stemness state but different molecular basis for potential differentiation. Adipogenesis-related genes expression pattern and presence of more mature adipocytes in ADSCs than in LDSCs after 21 days of adipogenic differentiation, indicated that differentiation capacity of LDSCs was significantly lower compared to ADSCs. Analysis of osteogenesis-related markers after 16 days of osteogenic differentiation revealed that both types of cells had characteristic osteoblast-like phenotype, but were at different stages of osteogenesis. Differences observed between LDSCs and ADSCs are probably due to the distinct molecular signature and their commitment in the tissue that governs their different capacity and fate during adipogenic and osteogenic induction in vitro despite their similar mesenchymal phenotype.

Liposuction Assisted Lipoma Removal - Option or Alternative?

BACKGROUND:

Lipomas are the most frequent soft -tissue tumors arising from adipose tissue. Traditionally, open surgery is a mainstay of their treatment. Recently, new treatment modalities emerge in order to decrease morbidity, to increase satisfaction rate in patents, but not to raise recurrence risk at the same time.

AIM:

The aim of this article is to present our experience with liposuction assisted lipoma removal in terms of efficacy, complications, risk of recurrence and patient satisfaction.

METHODS:

The study was prospective in which treated lipomas with vacuum suction were analyzed. Preoperative diagnosis comprised clinical exam and additional diagnostic tools as to rule out malignancy. Subcutaneous lipomas with diameter of at least 5 cm were taken into account. Tumescent liposuction technique with modification was used.

RESULTS:

Lipoma’s size, distribution and demographics are given. Total removal with affordable rate of complication was achieved in each case. No recurrences in 12 months follow-up period were seen. Satisfaction rate in patients was high.

CONCLUSION:

Liposuction assisted lipoma removal is a good alternative to open approach lipectomy and we would recommend its use in selected cases where, it might be more advantageous. However, prospective randomized controlled studies are needed in order to estimate its accurate clinical value.

Characterization of two distinct lipomas: a comparative analysis from surgical perspective

BACKGROUND

Lipomas are common benign soft tissue tumors that are well-circumscribed and encapsulated. However, adipose masses that are not demarcated from the surrounding fat are often encountered. Two distinct types of lipomas were analyzed from surgical perspective.

METHODS

Thirty patients were enrolled after lipoma excision and diagnosed with either encapsulated (n = 20) or non-encapsulated lipoma (n = 10). Comparison of clinical variables, histologic analyses and characterization of the lipoma adipose-derived stem cells (ASCs) between the two lipomas were performed.

RESULTS

Non-encapsulated lipomas were associated with older age at operation, larger tumor and increased seroma formation. The density of lymphatic vessels and gene expressions related to lymphatic vessel, inflammation and proliferation were increased in non-encapsulated lipoma. ASCs of non-encapsulated lipoma showed enhanced proliferation when cultured with serum.

CONCLUSIONS

Non-encapsulated lipomas and their ASCs showed distinct lymphatic histology and cellular response. These findings elucidated the pathogenesis and pathophysiology of lipomas.

Hypothesis: The Intratumoral Immune Response against a Cancer Progenitor Cell Impacts the Development of Well-Differentiated versus Dedifferentiated Disease in Liposarcoma

Well-differentiated/dedifferentiated (WD/DD) liposarcoma is a rare malignancy of adipocyte origin (“fat cancer”). Tumors may be entirely WD, WD with a DD component, or rarely DD without a clear WD component. WD tumors are low grade and generally indolent, while tumors with a DD component are high grade and behave much more aggressively, with a modest potential for distant metastasis. The presence of cancer progenitor cells in WD/DD liposarcoma is suggested by clinical evidence and reported research findings. In addition, there are emerging data to support the existence of a naturally occurring, antigen-driven, and adaptive immune response within the tumor microenvironment. We hypothesize that the intratumoral immune response is directed against a cancer progenitor cell and that the outcome of this response impacts the development of WD versus DD disease. Further study will likely provide interesting insights into the disease biology of WD/DD liposarcoma that may be readily translated to other more common cancers.

Adipose-Derived Stromal Cells from Lipomas: Isolation, Characterisation and Review of the Literature

OBJECTIVE

The aim of this study was to characterize adipose-derived stromal cells (ADSCs) from patients diagnosed with multiple symmetric lipomatosis (MSL) in order to obtain potentially new insights into the pathophysiology, pathogenesis and treatment of this disease.

METHODS

Cells from the stromal vascular fraction were analysed by the colony-forming efficiency assay and flow cytometry using standard markers. Moreover, the power of adipogenic plasticity was evaluated. Finally, a literature review was performed from 1982 to 2015 using the US National Institutes of Health's PubMed database.

RESULTS

Three European-descent patients diagnosed with either MSL type I or II could be identified for analysis. The resulting mean colony-forming efficiency assay was 14.3 ± 5%. Flow-cytometric analysis of the ADSCs revealed high levels of CD34 (70 ± 9%), CD45 (37 ± 13%) and CD73 (55.8 ± 14%), whereas low levels of CD31 (16.8 ± 14%) and CD105 (5.8 ± 0.7%) were detected. Furthermore, ADSCs showed a strong adipogenic potential, which is in line with the literature review. The stem cell pool in lipoma shows several alterations in biological activities, such as proliferation, apoptosis and stemness.

CONCLUSIONS

ADSCs from lipoma may be interesting in the application of regenerative medicine. We discuss possible molecular treatment options to regulate their activities at the source of the MSL.

Adipose progenitor cells reside among the mature adipocytes: morphological research using an organotypic culture system

The precise localization and biological characteristics of the adipose progenitor cells are still a focus of debate. In this study, the localization of the adipose progenitor cells was determined using an organotypic culture system of adipose tissue slices. The tissue slices of subcutaneous white adipose tissue from rats were placed on a porous membrane and cultured at the interface between air and the culture medium for up to 5 days with or without adipogenic stimulation. The structure of adipose tissue components was sufficiently preserved during the culture and, following adipogenic stimulation with insulin, dexamethasone, and 3-isobutyl-1-methylxanthine, numerous multilocular adipocytes appeared in the interstitium among the mature adipocytes. Histomorphological 3-D observation using confocal laser microscopy revealed the presence of small mesenchymal cells containing little or no fat residing in the perivascular region and on the mature adipocytes and differentiation from the pre-existing mesenchymal cells to multilocular adipocytes. Immunohistochemistry demonstrated that these cells were initially present within the fibronectin-positive extracellular matrix (ECM). The adipose differentiation of the mesenchymal cells was confirmed by the enhanced expression of C/EBP-β suggesting adipose differentiation and the concurrent advent of CD105-expressing mesenchymal cells within the interstitium of the mature adipocytes. Based on the above, the mesenchymal cells embedded in the ECM around the mature adipocytes were confirmed to be responsible for adipogenesis because the transition of the mesenchymal cells to the stem state contributed to the increase in the number of adipocytes in rat adipose tissue.

Persistence of CD34 Stem Marker in Human Lipoma: Searching for Cancer Stem Cells

Background: Lipomas are benign solid tumours that develop in soft tissues with origin in mesenchymal progenitors. Macroscopically, they appear as soft-elastic nodules, varying in volume from a few millimiters to several centimetres and can enlarge progressively. Although they are usually asymptomatic, they can cause symptoms due to nerve or vessel compression. Microscopically they appear as fibrous connective tissue stroma with embedded adipocytes, and absence of inflammation. Up to now no characterisation of stem cell population present in this tissue has been performed.

Methods: Cytofluorimetric, biological and molecular biology analyses have been performed in order to test superficial cell markers and gene expression profile related to stemness and apoptotic activity of cells present in lipoma tissues compared to those of adipose tissue's cells.

Results: Our results confirmed that CD34⁺ cells in lipoma were present around small adipocytes, showing several altered biological activity such as proliferation, apoptotis and stemness.

Conclusions: The data emerging from the comparison of the lipoma cells and normal adipose tissue, suggests the presence of cell precursors involved in the development of the lipoma. This hypothesis requires further investigation and may indicate new thresholds in the study of benign tumour pathogenesis.

En-bloc resection of a giant retroperitoneal lipoma: a case report and review of the literature

BACKGROUND

Retroperitoneal lipomas are an extremely rare condition with only 17 cases described in the literature since 1980. They can reach enormous size and cause significant abdominal symptoms. The most important differential diagnosis is the well-differentiated liposarcoma, which preoperatively often may not definitely be ruled out.

CASE PRESENTATION

We present the case of a 73 year-old Caucasian patient with a giant retroperitoneal lipoma of 9 kg measuring 55 cm in diameter. The patient presented with abdominal pain and swelling that had been slowly progressive for the last 15 years. On computerized tomography an immense retroperitoneal tumor was revealed. Intraoperatively, the tumor did not show any signs of infiltrative growth, therefore sole tumor extirpation was performed.

CONCLUSION

Retroperitoneal lipomas are not clearly distinguishable from well-differentiated liposarcomas on imaging and even biopsies may be misleading. Moreover, abdominal symptoms, i.e. pain, obstipation and dysphagia may occur due to mechanical displacement. Therefore, surgical exploration with complete oncological resection is the therapy of choice if malignity cannot be ruled out.

Adipose-derived stem cells: fatty potentials for therapy

Adipose-derived stem cells (ASCs) are the mesenchymal stem cell (MSC) population found in the stromal-vascular fraction (SVF) of fat tissue. White adipose tissue (WAT), with well-established roles in lipid storage and adipokine secretion, is advantageous over bone marrow as the source of MSCs due to relative abundance and ease of isolation of the tissue. ASCs reside perivascularly within WAT and physiologically undergo adipogenesis to support WAT expansion in response to increased energy intake. Apart from adipogenesis, ASCs can be induced in vitro to differentiate into osteoblasts, chondroblasts, myocytes, neurons and other cell types. ASCs can also be reprogrammed to induced pluripotent stem (iPS) cells more efficiently than other cell types. ASCs are immunoprivileged cells and secrete immunomodulatory, angiogenic, anti-apoptotic and haematopoietic factors that facilitate tissue repair. The multi-lineage differentiation capacity, unique immunobiological properties and secretome of ASCs offer tremendous therapeutic potentials in regenerative medicine.

Histological and molecular features of lipomatous and nonlipomatous adipose tissue in familial partial lipodystrophy caused by LMNA mutations

OBJECTIVES

Type 2 familial partial lipodystrophy (FPLD2) is a rare adipose tissue (AT) disease caused by mutations in LMNA, in which lipomas appear occasionally. In this study, we aimed to histologically characterize FPLD2-associated lipomatosis and study the expression of genes and proteins involved in cell cycle control, mitochondrial function, inflammation and adipogenesis.

DESIGN AND PATIENTS

One lipoma and perilipoma fat from each of four subjects with FPLD2 and 10 control subjects were analysed by optical microscopy. The presence of inflammatory cells was evaluated by immunohistochemistry. Real-time RT-PCR and Western blot were used to evaluate gene and protein levels.

RESULTS

Adipocytes from lipodystrophic patients were significantly larger than those of controls, in both the lipomas and perilipoma fat. Lipodystrophic AT exhibited CD68(+) macrophages and CD3(+) lymphocytes infiltration. TP53 expression was reduced in all types of lipomas. At protein level, C/EBPβ, p53 and pRb were severely disturbed in both lipodystrophic lipomas and perilipoma fat coming from lipoatrophic areas, whereas the expression of CEBPα was normal. Mitochondrial function genes were less expressed in lipoatrophic fat. In both lipomas and perilipoma fat from lipoatrophic areas, the expression of adipogenes was lower than controls.

CONCLUSIONS

Even in lipomas, the adipogenic machinery is impaired in lipodystrophic fat coming from lipoatrophic regions in FPLD2, although the histological phenotype is near-normal, exhibiting low-grade inflammatory features. Our results suggest that the p53 pathway and some adipogenic proteins, such as CEBPα, could contribute to the maintenance of this near normal phenotype in the remnant AT present in these patients.

Adipocyte-derived stem cells for the face

This review gives a basic overview of the current state of fat transplantation in view of adipose-derived stem cells. Current technologies regarding facial rejuvenation are presented, with a brief review of the procedures.

The pivotal role of reactive oxygen species generation in the hypoxia-induced stimulation of adipose-derived stem cells

Adipose-derived stem cells (ASCs) offer a potential alternative for tissue repair and regeneration. We have recently shown that hypoxia stimulates ASCs and enhances the regenerative potential of ASCs, which is beneficial for ASC therapy. In the present study, we further investigated a key mediator and a signal pathway involved in the stimulation of ASC during hypoxia. Culturing ASC in a hypoxic incubator (2% oxygen tension) increased the proliferation and migration, and this was mediated by Akt and ERK pathways. To determine the generation of reactive oxygen species (ROS), 2',7'-dichlorofluorescin diacetate intensity was detected by fluorescence-activated cell sorting. Hypoxia significantly increased the dichlorofluorescin diacetate intensity, which was greatly reduced by N-acetyl-cysteine and diphenyleneiodonium treatment. Likewise, the hypoxia-induced proliferation and migration of ASCs were reversed by N-acetyl-cysteine and diphenyleneiodonium treatment, suggesting the involvement of ROS generation in ASC stimulation. Further, we examined the activation of receptor tyrosine kinases and observed that hypoxia stimulated the phosphorylation of platelet-derived growth factor receptor-β. In summary, the ROS produced by ASCs in response to hypoxia was mostly likely due to NADPH oxidase activity. The increased cellular ROS was accompanied by the phosphorylation of platelet-derived growth factor receptor-β as well as by the activation of ERK and Akt signal pathways. Our results suggest a pivotal role for ROS generation in the stimulation of ASCs by hypoxia.

Adipose tissue remodeling under ischemia: death of adipocytes and activation of stem/progenitor cells

BACKGROUND

Following various types of plastic surgery, such as adipose grafting and flap elevation, adipose tissue undergoes ischemia, leading to hypoxia and nutrient depletion. However, few studies have examined ischemic and/or hypoxic changes in adipose tissue.

METHODS

The authors established surgically induced ischemia models by severing blood vessels supplying the inguinal fat pads in mice. The partial pressure of oxygen in adipose tissue was measured with an oxygen monitor, and ischemic changes were analyzed by whole-mount staining, immunohistochemistry, flow cytometry, and Western blotting. The authors also examined cell survival under a hypoxic condition in vitro.

RESULTS

Models for three degrees (mild, intermediate, and severe) of ischemia showed approximately 75, 55, and 20 percent of the partial pressure of oxygen level in normal adipose tissue (50.5±1.3 mm Hg), respectively. Adipose tissue atrophy with substantial fibrosis on day 28 was seen, depending on the severity of ischemia. Intermediate and severe ischemia induced elevated expression of hypoxia-inducible factor 1α and fibroblast growth factor 2 on day 1 and degenerative changes (i.e., apoptosis, necrosis, and macrophage infiltration and phagocytosis) in adipose tissue. Dead cells included adipocytes, vascular endothelial cells, and blood-derived cells, but not adipose-derived stem/progenitor cells. Subsequent to degenerative changes, regenerative changes were seen, including angiogenesis, adipogenesis, and proliferation of cells (adipose-derived stem/progenitor cells, vascular endothelial cells, and blood cells). The authors found that, in vitro, the experimentally differentiated adipocytes underwent apoptosis and/or necrosis under severe hypoxia, but adipose-derived stem/progenitor cells remained viable.

CONCLUSIONS

Severe ischemia/hypoxia induces degenerative changes in adipose tissue and subsequent adaptive tissue remodeling. Adipocytes die easily under ischemic conditions, whereas adipose-derived stem/progenitor cells are activated and contribute to adipose tissue repair.

Rapid and dynamic alterations of gene expression profiles of adult porcine bone marrow-derived stem cell in response to hypoxia

This study sought to identify the gene expression patterns of porcine bone marrow-derived MSC in response to hypoxia and to investigate novel specific hypoxic targets that may have a role in determining MSC proliferation/survival and differentiation. MSC from 15 animals were incubated in 1% oxygen and 8% carbon dioxide for 6, 12, and 24 h. RNA samples were isolated and assayed with Affymetrix porcine arrays and quantitative reverse-transcription PCR. Significant gene expression levels among the four groups of normoxia, 6-, 12-, and 24-h hypoxia were identified. The pattern in the 12-h hypoxia group was similar to that of the 24-h group. Of 23,924 probes, 377 and 210 genes were regulated in the 6- and 24-h hypoxia groups, respectively. Functional classification of the hypoxic regulated genes was mainly clustered in cell proliferation and response to stress. However, the major upregulated genes in the 6-h group were activated in cell cycle phases; the genes in the 24-h hypoxia were evenly separated into cell differentiation, apoptosis, and cellular metabolic processes. Twenty-eight genes were upregulated in all hypoxia groups; these genes are considered as hypoxic targets. Our results identified a genome-wide hypoxia-induced gene expression pattern in porcine MSC. This study provides a global view of molecular events in the cells during exposure to hypoxia and revealed a set of novel candidate hypoxic targets.