Dedifferentiated adipocyte-derived progeny cells (DFAT cells): Potential stem cells of adipose tissue

N-acetylcysteine promotes the proliferation of porcine adipose-derived stem cells during in vitro long-term expansion for cultured meat production

Cultured meat is an efficient, safe and sustainable meat production technology. Adipose-derived stem cell (ADSC) is a promising cell type for cultured meat. In vitro, obtaining numerous of ADSCs is a pivotal step for cultured meat. In this research, we demonstrated that the proliferation and adipogenic differentiation of ADSCs significantly decreased during serial passage. Then, senescence β-galactosidase (SA-β-gal) staining showed that the positive rate of P9 ADSCs was 7.74-fold than P3 ADSCs. Subsequently, RNA sequencing (RNA-seq) was performed for P3 and P9 ADSCs and found that PI3K-AKT pathway was up-regulated, but cell cycle and DNA repair pathway were down-regulated in P9 ADSCs. Then, N-Acetylcysteine (NAC) was added during long-term expansion and showed that NAC enhanced the ADSCs proliferation and maintained adipogenic differentiation. Finally, RNA-seq was performed for P9 ADSCs cultured with or without NAC and showed that NAC restored the cell cycle and DNA repair pathway in P9 ADSCs. These results highlighted that NAC was an excellent supplement for large-scale expansion of porcine ADSCs for cultured meat.

Adipocyte mesenchymal transition contributes to mammary tumor progression

Obesity is associated with increased cancer incidence and progression. However, the relationship between adiposity and cancer remains poorly understood at the mechanistic level. Here, we report that adipocytes from tumor-invasive mammary fat undergo de-differentiation to fibroblast-like precursor cells during tumor progression and integrate into the tumor microenvironment. Single-cell sequencing reveals that these de-differentiated adipocytes lose their original identities and transform into multiple cell types, including myofibroblast- and macrophage-like cells, with their characteristic features involved in immune response, inflammation, and extracellular matrix remodeling. The de-differentiated cells are metabolically distinct from tumor-associated fibroblasts but exhibit comparable effects on tumor cell proliferation. Inducing de-differentiation by Xbp1s overexpression promotes tumor progression despite lower adiposity. In contrast, promoting lipid-storage capacity in adipocytes through MitoNEET overexpression curbs tumor growth despite greater adiposity. Collectively, the metabolic interplay between tumor cells and adipocytes induces adipocyte mesenchymal transition and contributes to reconfigure the stroma into a more tumor-friendly microenvironment.

Zhu et al. report that in mammary tumors, adipocytes undergo metabolic reprograming and de-differentiation. They acquire myofibroblast- and macrophage-like features, a process referred to as “adipocyte mesenchymal transition,” which modifies the tumor microenvironment via ECM remodeling and activation of the immune response and likely contributes to tumor progression.

Reassessment of adipocyte technology for cellular agriculture of alternative fat

Alternative proteins, such as cultivated meat, have recently attracted significant attention as novel and sustainable food. Fat tissue/cell is an important component of meat that makes organoleptic and nutritional contributions. Although adipocyte biology is relatively well investigated, there is limited focus on the specific techniques and strategies to produce cultivated fat from agricultural animals. In the assumed standard workflow, stem/progenitor cell lines are derived from tissues of animals, cultured for expansion, and differentiated into mature adipocytes. Here, we compile information from literature related to cell isolation, growth, differentiation, and analysis from bovine, porcine, chicken, other livestock, and seafood species. A diverse range of tissue sources, cell isolation methods, cell types, growth media, differentiation cocktails, and analytical methods for measuring adipogenic levels were used across species. Based on our analysis, we identify opportunities and challenges in advancing new technology era toward producing "alternative fat" that is suitable for human consumption.

Perspectives on scaling production of adipose tissue for food applications

With rising global demand for food proteins and significant environmental impact associated with conventional animal agriculture, it is important to develop sustainable alternatives to supplement existing meat production. Since fat is an important contributor to meat flavor, recapitulating this component in meat alternatives such as plant based and cell cultured meats is important. Here, we discuss the topic of cell cultured or tissue engineered fat, growing adipocytes in vitro that could imbue meat alternatives with the complex flavor and aromas of animal meat. We outline potential paths for the large scale production of in vitro cultured fat, including adipogenic precursors during cell proliferation, methods to adipogenically differentiate cells at scale, as well as strategies for converting differentiated adipocytes into 3D cultured fat tissues. We showcase the maturation of knowledge and technology behind cell sourcing and scaled proliferation, while also highlighting that adipogenic differentiation and 3D adipose tissue formation at scale need further research. We also provide some potential solutions for achieving adipose cell differentiation and tissue formation at scale based on contemporary research and the state of the field.

Neurogenic and Neuroprotective Potential of Stem/Stromal Cells Derived from Adipose Tissue

Currently, the number of stem-cell based experimental therapies in neurological injuries and neurodegenerative disorders has been massively increasing. Despite the fact that we still have not obtained strong evidence of mesenchymal stem/stromal cells’ neurogenic effectiveness in vivo, research may need to focus on more appropriate sources that result in more therapeutically promising cell populations. In this study, we used dedifferentiated fat cells (DFAT) that are proven to demonstrate more pluripotent abilities in comparison with standard adipose stromal cells (ASCs). We used the ceiling culture method to establish DFAT cells and to optimize culture conditions with the use of a physioxic environment (5% O₂). We also performed neural differentiation tests and assessed the neurogenic and neuroprotective capability of both DFAT cells and ASCs. Our results show that DFAT cells may have a better ability to differentiate into oligodendrocytes, astrocytes, and neuron-like cells, both in culture supplemented with N21 and in co-culture with oxygen–glucose-deprived (OGD) hippocampal organotypic slice culture (OHC) in comparison with ASCs. Results also show that DFAT cells have a different secretory profile than ASCs after contact with injured tissue. In conclusion, DFAT cells constitute a distinct subpopulation and may be an alternative source in cell therapy for the treatment of nervous system disorders.

The neovascularization effect of dedifferentiated fat cells

Mature adipocyte-derived dedifferentiated fat (DFAT) cells can be prepared efficiently and with minimal invasiveness to the donor. They can be utilized as a source of transplanted cells during therapy. Although the transplantation of DFAT cells into an ischemic tissue enhances angiogenesis and increases vascular flow, there is little information regarding the mechanism of the therapeutic angiogenesis. To further study this, mice ischemic hindlimb model was used. It was confirmed that in comparison with the adipose derived stem cells and fibroblasts, the transplantation of DFAT cells led to a significant improvement in the blood flow and increased mature blood vessel density. The ability of DFAT cells to secrete angiogenic factors in hypoxic conditions and upon co-culture with vascular endothelial cells was then examined. Furthermore, we examined the possibility that DFAT cells differentiating into pericytes. The therapeutic angiogenic effects of DFAT cells were observed by the secretion of angiogenic factors and pericyte differentiation by transforming growth factor β1 signalling via Smad2/3. DFAT cells can be prepared with minimal invasiveness and high efficiency and are expected to become a source of transplanted cells in the future of angiogenic cell therapy.

PDGFRα/PDGFRβ signaling balance modulates progenitor cell differentiation into white and beige adipocytes

The relative abundance of thermogenic beige adipocytes and lipid-storing white adipocytes in adipose tissue underlie its metabolic activity. The roles of adipocyte progenitor cells, which express PDGFRα or PDGFRβ, in adipose tissue function have remained unclear. Here, by defining the developmental timing of PDGFRα and PDGFRβ expression in mouse subcutaneous and visceral adipose depots, we uncover depot specificity of pre-adipocyte delineation. We demonstrate that PDGFRα expression precedes PDGFRβ expression in all subcutaneous but in only a fraction of visceral adipose stromal cells. We show that high-fat diet feeding or thermoneutrality in early postnatal development can induce PDGFRβ⁺ lineage recruitment to generate white adipocytes. In contrast, the contribution of PDGFRβ⁺ lineage to beige adipocytes is minimal. We provide evidence that human adipose tissue also contains distinct progenitor populations differentiating into beige or white adipocytes, depending on PDGFRβ expression. Based on PDGFRα or PDGFRβ deletion and ectopic expression experiments, we conclude that the PDGFRα/PDGFRβ signaling balance determines progenitor commitment to beige (PDGFRα) or white (PDGFRβ) adipogenesis. Our study suggests that adipocyte lineage specification and metabolism can be modulated through PDGFR signaling.

Adipocyte nuclei captured from VAT and SAT

Background

Obesity-related comorbidities are thought to result from the reprogramming of the epigenome in numerous tissues and cell types, and in particular, mature adipocytes within visceral and subcutaneous adipose tissue, VAT and SAT. The cell-type specific chromatin remodeling of mature adipocytes within VAT and SAT is poorly understood, in part, because of the difficulties of isolating and manipulating large fragile mature adipocyte cells from adipose tissues.

Methods

We constructed MA-INTACT (Mature Adipocyte-Isolation of Nuclei TAgged in specific Cell Types) mice using the adiponectin (ADIPOQ) promoter (ADNp) to tag the surface of mature adipocyte nuclei with a reporter protein. The SUN1mRFP1Flag reporter is comprised of a fragment of the nuclear transmembrane protein SUN1, the fluorescent protein mRFP1, and three copies of the Flag epitope tag.

Results

Mature adipocyte nuclei were rapidly and efficiently immuno-captured from VAT and SAT (MVA and MSA nuclei, respectively), of MA-INTACT mice. MVA and MSA nuclei contained 1,000 to 10,000-fold higher levels of adipocyte-specific transcripts, ADIPOQ, PPARg2, EDNRB, and LEP, relative to uncaptured nuclei, while the latter expressed higher levels of leukocyte and endothelial cell markers IKZF1, RETN, SERPINF1, SERPINE1, ILF3, and TNFA. MVA and MSA nuclei differentially expressed several factors linked to adipogenesis or obesity-related health risks including CEBPA, KLF2, RETN, SERPINE1, and TNFA. The various nuclear populations dramatically differentially expressed transcripts encoding chromatin remodeler proteins regulating DNA cytosine methylation and hydroxymethylation (TETs, DNMTs, TDG, GADD45s) and nucleosomal histone modification (ARID1A, KAT2B, KDM4A, PRMT1, PRMT5, PAXIP1). Remarkably, MSA and MVA nuclei expressed 200 to 1000-fold higher levels of thermogenic marker transcripts PRDM16 and UCP1.

Conclusions

The MA-INTACT mouse enables a simple way to perform cell-type specific analysis of highly purified mature adipocyte nuclei from VAT and SAT and increases the statistical significance of data collected on adipocytes. Isolated VAT and SAT adipocyte nuclei expressed distinct patterns of transcripts encoding chromatin remodeling factors and proteins relevant to diabetes, cardiovascular disease, and thermogenesis. The MA-INTACT mouse is an useful model to test the impact of caloric intake, dietary nutrients, exercise, and pharmaceuticals on the epigenome-induced health risks of obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s40608-016-0112-6) contains supplementary material, which is available to authorized users.

Adipose depots differ in cellularity, adipokines produced, gene expression, and cell systems

The race to manage the health concerns related to excess fat deposition has spawned a proliferation of clinical and basic research efforts to understand variables including dietary uptake, metabolism, and lipid deposition by adipocytes. A full appreciation of these variables must also include a depot-specific understanding of content and location in order to elucidate mechanisms governing cellular development and regulation of fat deposition. Because adipose tissue depots contain various cell types, differences in the cellularity among and within adipose depots are presently being documented to ascertain functional differences. This has led to the possibility of there being, within any one adipose depot, cellular distinctions that essentially result in adipose depots within depots. The papers comprising this issue will underscore numerous differences in cellularity (development, histogenesis, growth, metabolic function, regulation) of different adipose depots. Such information is useful in deciphering adipose depot involvement both in normal physiology and in pathology. Obesity, diabetes, metabolic syndrome, carcass composition of meat animals, performance of elite athletes, physiology/pathophysiology of aging, and numerous other diseases might be altered with a greater understanding of adipose depots and the cells that comprise them-including stem cells-during initial development and subsequent periods of normal/abnormal growth into senescence. Once thought to be dormant and innocuous, the adipocyte is emerging as a dynamic and influential cell and research will continue to identify complex physiologic regulation of processes involved in adipose depot physiology.

Glial-like differentiation potential of human mature adipocytes

The potential ability to differentiate dedifferentiated adipocytes into a neural lineage is attracting strong interest as an emerging method of producing model cells for the treatment of a variety of neurological diseases. Here, we describe the efficient conversion of dedifferentiated adipocytes into a neural-like cell population. These cells grew in neurosphere-like structures and expressed a high level of the early neuroectodermal marker Nestin. These neurospheres could proliferate and express stemness genes, suggesting that these cells could be committed to the neural lineage. After neural induction, NeuroD1, Sox1, Double Cortin, and Eno2 were not expressed. Patch clamp data did not reveal different electrophysiological properties, indicating the inability of these cells to differentiate into mature neurons. In contrast, the differentiated cells expressed a high level of CLDN11, as demonstrated using molecular method, and stained positively for the glial cell markers CLDN11 and GFAP, as demonstrated using immunocytochemistry. These data were confirmed by quantitative results for glial cell line-derived neurotrophic factor production, which showed a higher secretion level in neurospheres and the differentiated cells compared with the untreated cells. In conclusion, our data demonstrate morphological, molecular, and immunocytochemical evidence of initial neural differentiation of mature adipocytes, committing to a glial lineage.

Ovarian germline stem cells: an unlimited source of oocytes?

While there has been progress in directing the development of embryonic stem cells and induced pluripotent stem cells toward a germ cell state, their ability to serve as a source of functional oocytes in a clinically relevant model or situation has yet to be established. Recent studies suggest that the adult mammalian ovary is not endowed with a finite number of oocytes, but instead possesses stem cells that contribute to their renewal. The ability to isolate and promote the growth and development of such ovarian germline stem cells (GSCs) would provide a novel means to treat infertility in women. Although such ovarian GSCs are well characterized in nonmammalian model organisms, the findings that support the existence of adult ovarian GSCs in mammals have been met with considerable evidence that disputes their existence. This review details the lessons provided by model organisms that successfully utilize ovarian GSCs to allow for a continual and high level of female germ cell production throughout their life, with a specific focus on the cellular mechanisms involved in GSC self-renewal and oocyte development. Such an overview of the role that oogonial stem cells play in maintaining fertility in nonmammalian species serves as a backdrop for the data generated to date that supports or disputes the existence of GSCs in mammals as well as the future of this area of research in terms of its potential for any application in reproductive medicine.

The phenotype and tissue-specific nature of multipotent cells derived from human mature adipocytes

Dedifferentiated fat (DFAT) cells derived from mature adipocytes have been considered to be a homogeneous group of multipotent cells, which present to be an alternative source of adult stem cells for regenerative medicine. However, many aspects of the cellular nature about DFAT cells remained unclarified. This study aimed to elucidate the basic characteristics of DFAT cells underlying their functions and differentiation potentials. By modified ceiling culture technique, DFAT cells were converted from human mature adipocytes from the human buccal fat pads. Flow cytometry analysis revealed that those derived cells were a homogeneous population of CD13(+) CD29(+) CD105(+) CD44(+) CD31(-) CD34(-) CD309(-) α-SMA(-) cells. DFAT cells in this study demonstrated tissue-specific differentiation properties with strong adipogenic but much weaker osteogenic capacity. Neither did they express endothelial markers under angiogenic induction.

Pluripotent stem cells derived from mouse and human white mature adipocytes

White mature adipocytes give rise to so-called dedifferentiated fat (DFAT) cells that spontaneously undergo multilineage differentiation. In this study, we defined stem cell characteristics of DFAT cells as they are generated from adipocytes and the relationship between these characteristics and lineage differentiation. Both mouse and human DFAT cells, prepared from adipose tissue and lipoaspirate, respectively, showed evidence of pluripotency, with a maximum 5-7 days after adipocyte isolation. The DFAT cells spontaneously formed clusters in culture, which transiently expressed multiple stem cell markers, including stage-specific embryonic antigens, and Sca-1 (mouse) and CD105 (human), as determined by real-time polymerase chain reaction, fluorescence-activated cell sorting, and immunostaining. As the stem cell markers decreased, markers characteristic of the three germ layers and specific lineage differentiation, such as α-fetoprotein (endoderm, hepatic), Neurofilament-66 (ectoderm, neurogenic), and Troponin I (mesoderm, cardiomyogenic), increased. However, no teratoma formation was detected after injection in immunodeficient mice. A novel modification of the adipocyte isolation aimed at ensuring the initial purity of the adipocytes and avoiding ceiling culture allowed isolation of DFAT cells with pluripotent characteristics. Thus, the adipocyte-derived DFAT cells represent a plastic stem cell population that is highly responsive to changes in culture conditions and may benefit cell-based therapies.

Emerging roles of zinc finger proteins in regulating adipogenesis

Proteins containing the zinc finger domain(s) are named zinc finger proteins (ZFPs), one of the largest classes of transcription factors in eukaryotic genomes. A large number of ZFPs have been studied and many of them were found to be involved in regulating normal growth and development of cells and tissues through diverse signal transduction pathways. Recent studies revealed that a small but increasing number of ZFPs could function as key transcriptional regulators involved in adipogenesis. Due to the prevalence of obesity and metabolic disorders, the investigation of molecular regulatory mechanisms of adipocyte development must be more completely understood in order to develop novel and long-term impact strategies for ameliorating obesity. In this review, we discuss recent work that has documented that ZFPs are important functional contributors to the regulation of adipogenesis. Taken together, these data lead to the conclusion that ZFPs may become promising targets to combat human obesity.