The browning and mobilization of subcutaneous white adipose tissue supports efficient skin repair.

Adipocytes in dermis are considered to be important participants in skin repair and regeneration, but the role of subcutaneous white adipose tissue (sWAT) in skin repair is poorly understood. Here, we revealed the dynamic changes of sWAT during wound healing process. Lineage-tracing mouse studies revealed that sWAT would enter into the large wound bed and participate in the formation of granulation tissue. Moreover, sWAT undergoes beiging after skin injury. Inhibition of sWAT beiging by genetically silencing PRDM16, a key regulator to beiging, hindered wound healing process. The transcriptomics results suggested that beige adipocytes in sWAT abundantly express neuregulin 4 (NRG4), which regulated macrophage polarization and the function of myofibroblasts. In diabetic wounds, the beiging of sWAT was significantly suppressed. Thus, adipocytes from sWAT regulate multiple aspects of repair and may be therapeutic for inflammatory diseases and defective wound healing associated with aging and diabetes.

Challenges and opportunities in obesity: the role of adipocytes during tissue fibrosis.

Obesity is a chronic disease that affects the energy balance of the whole body. In addition to increasing fat mass, tissue fibrosis occurred in white adipose tissue in obese condition. Fibrosis is the over-activation of fibroblasts leading to excessive accumulation of extracellular matrix, which could be caused by various factors, including the status of adipocytes. The morphology of adipocytes responds rapidly and dynamically to nutrient fluctuations. Adaptive hypertrophy of normal adipocytes protects peripheral organs from damage from lipotoxicity. However, the biological behavior of hypertrophic adipocytes in chronic obesity is abnormally altered. Adipocytes lead to fibrotic remodeling of the extracellular matrix by inducing unresolved chronic inflammation, persistent hypoxia, and increasing myofibroblast numbers. Moreover, adipocyte-induced fibrosis not only restricts the flexible expansion and contraction of adipose tissue but also initiates the development of various diseases through cellular autonomic and paracrine effects. Regarding anti-fibrotic therapy, dysregulated intracellular signaling and epigenetic changes represent potential candidate targets. Thus, modulation of adipocytes may provide potential therapeutic avenues for reversing pathological fibrosis in adipose tissue and achieving the anti-obesity purpose.

Combining High-Density Fat and Condensed Low-Density Fat Injections for Precise Facial Rejuvenation.

BACKGROUND: Facial aging involves ptosis, adipose atrophy, and skeletal resorption. Depletion of adipose tissue primarily affects the deep facial fat compartment, leading to facial depression or ptosis, accompanied by atrophy of the superficial compartment. Restoring volume in the deep fat compartment is crucial for facial rejuvenation, while enhancing its supportive properties is also important. The superficial fat compartment contains small-sized adipocytes, and autologous fat grafting is a popular approach. However, variability in fat retention, homogeneity, and processing methods can impact outcomes, necessitating careful selection of a suitable fat processing material for precise facial fat grafting. METHOD: A retrospective study was conducted on 50 patients who underwent facial augmentation using combined transplantation of high-density fat (HDF) and condensed low-density fat (CLDF) and 25 patients who underwent conventional Coleman fat grafting. Coleman fat was harvested by standard technique and the adipose tissue was divided into HDF and CLDF fractions through centrifugation. Subsequently, the low-density fat fraction was subjected to a process involving physical disruption followed by additional centrifugation to obtain CLDF. The CLDF fraction was consequently injected into the pre-SMAS subcutaneous layer of the superficial fat compartments. Patient satisfaction was evaluated using a typical Likert scale. Photographs were taken and imageological examinations were performed before and after treatment. RESULT: The CLDF+HDF grafting group demonstrated a significantly shorter duration of swelling (6.0 ± 1.2 to 12.6 ± 3.3 days) and higher level of patient satisfaction when compared to the Coleman fat group. No serious complications were observed among all the patients who received the injections. CONCLUSION: The use of this new treatment approach allows for precise fat transplantation in facial regions. The use of high-concentration fat filling for deep facial layers and CLDF filling for superficial layers is a safe and effective treatment plan for facial rejuvenation. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Clinical, Histologic, and Transcriptomic Evaluation of Sequential Fat Grafting for Morphea: A Nonrandomized Controlled Trial.

Importance: Morphea is a rare disease of unknown etiology without satisfactory treatment for skin sclerosis and soft tissue atrophy. Objective: To provide clinical, histologic, and transcriptome evidence of the antisclerotic and regenerative effects of sequential fat grafting with fresh fat and cryopreserved stromal vascular fraction gel (SVF gel) for morphea. Design, Setting, and Participants: This single-center, nonrandomized controlled trial was conducted between January 2022 and March 2023 in the Department of Plastic and Reconstructive Surgery of Nanfang Hospital, Southern Medical University and included adult participants with early-onset or late-onset morphea who presented with varying degrees of skin sclerosis and soft tissue defect. Interventions: Group 1 received sequential grafting of fresh fat and cryopreserved SVF gel (at 1 and 2 months postoperation). Group 2 received single autologous fat grafting. All patients were included in a 12-month follow-up. Main Outcome and Measures: The primary outcome included changes in the modified Localized Scleroderma Skin Severity Index (mLoSSI) and Localized Scleroderma Skin Damage Index (LoSDI) scores as evaluated by 2 independent blinded dermatologists. The histologic and transcriptome changes of morphea skin lesions were also evaluated. Results: Of 44 patients (median [IQR] age, 26 [23-33] years; 36 women [81.8%]) enrolled, 24 (54.5%) were assigned to group 1 and 20 (45.5%) to group 2. No serious adverse events were noted. The mean (SD) mLoSSI scores at 12 months showed a 1.6 (1.50) decrease in group 1 and 0.9 (1.46) in group 2 (P = .13), whereas the mean (SD) LoSDI scores at 12 months showed a 4.3 (1.34) decrease in group 1 and 2.1 (1.07) in group 2 (P < .001), indicating that group 1 had more significant improvement in morphea skin damage but not disease activity compared with group 2. Histologic analysis showed improved skin regeneration and reduced skin sclerosis in group 1, whereas skin biopsy specimens of group 2 patients did not show significant change. Transcriptome analysis of skin biopsy specimens from group 1 patients suggested that tumor necrosis factor α signaling via NFκB might contribute to the immunosuppressive and antifibrotic effect of sequential fat grafting. A total of 15 hub genes were captured, among which many associated with morphea pathogenesis were downregulated and validated by immunohistochemistry, such as EDN1, PAI-1, and CTGF. Conclusions and Relevance: The results of this nonrandomized trial suggest that sequential fat grafting with fresh fat and cryopreserved SVF gel was safe and its therapeutic effect was superior to that of single autologous fat grafting with improved mLoSSI and LoSDI scores. Histological and transcriptomic changes further support the effectiveness after treatment. Trial Registration: Chinese Clinical Trial Registry identifier: ChiCTR2200058003.

Transplantation of beige adipose organoids fabricated using adipose acellular matrix hydrogel improves metabolic dysfunction in high-fat diet-induced obesity and type 2 diabetes mice.

Transplantation of brown adipose tissue (BAT) is a promising approach for treating obesity and metabolic disorders. However, obtaining sufficient amounts of functional BAT or brown adipocytes for transplantation remains a major challenge. In this study, we developed a hydrogel that combining adipose acellular matrix (AAM) and GelMA and HAMA that can be adjusted for stiffness by modulating the duration of light-crosslinking. We used human white adipose tissue-derived microvascular fragments to create beige adipose organoids (BAO) that were encapsulated in either a soft or stiff AAM hydrogel. We found that BAOs cultivated in AAM hydrogels with high stiffness demonstrated increased metabolic activity and upregulation of thermogenesis-related genes. When transplanted into obese and type 2 diabetes mice, the HFD + BAO group showed sustained improvements in metabolic rate, resulting in significant weight loss and decreased blood glucose levels. Furthermore, the mice showed a marked reduction in nonalcoholic liver steatosis, indicating improved liver function. In contrast, transplantation of 2D-cultured beige adipocytes failed to produce these beneficial effects. Our findings demonstrate the feasibility of fabricating beige adipose organoids in vitro and administering them by injection, which may represent a promising therapeutic approach for obesity and diabetes.

Adipose Component Transplantation: An Advanced Fat-Grafting Strategy for Facial Rejuvenation.

BACKGROUND: Autologous fat grafting is frequently used for volume augmentation and tissue regeneration. The uniform physical and biological characteristics of fat grafts, however, limit their optimal effects in various situations. Subjecting fat tissue to different mechanical processes results in adipose-derived products with distinct biological components and physical features. The present study describes a novel facial fat-grafting strategy, adipose component transplantation (ACT), that yields different adipose products that can be applied to specific injection sites. METHODS: All patients who underwent ACT were evaluated retrospectively. Fat tissue samples were fractionated into high-density fat, adipose matrix complex, stromal vascular fraction gel, and adipose collagen fragment, as described. Each of these fractions was processed and injected into indicated recipient sites. Additional SVF gel was cryopreserved and, if necessary, injected during the following 3 months. Patients were followed up after 1, 2, 3, and 6 months, and annually thereafter. RESULTS: From March of 2020 to September of 2021, 78 patients underwent whole face fat grafting using the ACT strategy. All operations and secondary injections of cryopreserved SVF gel were uneventful. There were no major complications, and final aesthetic results were satisfactory in 91% of patients. CONCLUSIONS: The ACT strategy allows specific adipose products to be applied to specific injection sites, as warranted. Adipose matrix complex is indicated for sufficient rigid support, high-density fat when large volumes are required, SVF gel for precise injection and cryopreservation, and ACF as mesotherapy for skin rejuvenation. The ACT strategy optimizes the biological functions and physical features of different adipose-derived products. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Comparable Effects on Healing between Autologous Diabetic Adipose-Derived Stem Cells and Allogeneic Normal Counterparts.

BACKGROUND: Adipose-derived stem cell (ASC) therapy is considered a promising strategy for improving impaired wound healing, especially in diabetics. Although the therapeutic potential of allogeneic ASCs from healthy donors is naturally limited, that of autologous ASCs from diabetic patients is questionable. The aim of this study was to investigate the impact of diabetic ASCs in the treatment of diabetic wounds. METHODS: Diabetic ASCs (DMA) and nondiabetic ASCs were isolated from db/db and C57BL/6J mice, and characterized by immunocytochemistry, proliferation, differentiation, and gene expression assays. The effects of both ASCs on healing were investigated using 36 male 10- to 12-week-old db/db mice. Wound size was measured semiweekly until day 28, and histologic and molecular analyses were performed at day 14. RESULTS: Both ASCs had fibroblast-like morphology and were CD44 + /CD90 + /CD34 - /CD45 - at passage 4. Compared with nondiabetic ASCs in vitro, DMA proliferative capability was restored by passage 4 ( P > 0.05). Although DMA osteogenesis was attenuated ( P < 0.01), both ASCs had similar adipogenesis and expressions of PPARγ/LPL/OCN/RUNX2 ( P > 0.05). In vivo experiments showed that, compared with phosphate-buffered saline control, both ASCs are comparable in improving wound healing ( P < 0.0001), angiogenesis ( P < 0.05), epithelial cell proliferation ( P < 0.05), and granulation tissue formation ( P < 0.0001). CONCLUSIONS: In both in vitro and in vivo murine models, DMAs have shown a comparable therapeutic capacity to normal ASCs in promoting diabetic wound healing by improving angiogenesis, reepithelialization, and granulation tissue formation. These results support clinical applications of autologous ASCs in diabetic wound treatments. CLINICAL RELEVANCE STATEMENT: This work has particular surgical relevance as it highlights a theoretical and clinical pathway to use diabetic patients' own ASCs to treat their wounds, bypassing any concerns of cross-host sourcing issues in regenerative medicine.

Brown adipose tissue transplantation improves skin fibrosis in localized scleroderma.

Adipose tissue transplantation shows great therapeutic potential in reversing localized scleroderma-associated skin fibrosis. Brown adipose tissue (BAT) can specifically secrete various cytokines against fibrosis, but its therapeutic potential in improving skin fibrosis has not yet been demonstrated. In this study, we have demonstrated the superior therapeutic efficacy of BAT transplantation for sclerotic skin by transplanting two distinct types of adipose tissue. In comparison to the white adipose tissue (WAT) group, mice treated with BAT transplantation exhibited a significant reduction in dermal thickness. BAT transplantation effectively reverses skin sclerosis through mechanisms involving inflammation reduction, promotion of angiogenesis, inhibition of myofibroblast accumulation, and collagen deposition. This therapeutic effect can be attributed to its unique paracrine effects. Furthermore, transcriptome sequencing (RNA-Seq) revealed upregulation of pathways associated with lipogenesis and fatty acid metabolism in BAT while downregulating pathways are related to transforming growth factor ß(TGF-ß), epithelial-mesenchymal transition (EMT), and inflammatory response. These findings suggest that BAT transplantation holds great promise as a novel approach for localized scleroderma treatment.

Delivery of adipose-derived growth factors from heparinized adipose acellular matrix accelerates wound healing.

Dermal white adipocytes are closely associated with skin homeostasis and wound healing. However, it has not been fully investigated whether adipose-derived products improve wound healing. Here, we obtained adipose acellular matrix (AAM) and adipose-derived growth factors (ADGFs) from human adipose tissue and fabricated an ADGF-loaded AAM via surface modification with heparin. The product, HEP-ADGF-AAM, contained an adipose-derived scaffold and released ADGFs in a controlled fashion. To test its efficacy in promoting wound healing, mice with full thickness wound received three different treatments: HEP-ADGF-AAM, AAM and ADM. Control mice received no further treatments. Among these treatments, HEP-ADGF-AAM best improved wound healing. It induced adipogenesis in situ after in vivo implantation and provided an adipogenic microenvironment for wounds by releasing ADGFs. HEP-ADGF-AAM not only induced adipocyte regeneration, but also enhanced fibroblast migration, promoted vessel formation, accelerated wound closure, and enhanced wound epithelialization. Moreover, there was a close interaction between HEP-ADGF-AAM and the wound bed, and collagen was turned over in HEP-ADGF-AAM. These results show that HEP-ADGF-AAM might substantially improve re-epithelialization, angiogenesis, and skin appendage regeneration, and is thus a promising therapeutic biomaterial for skin wound healing.

Physical Expansion Preconditioning Promotes Host-derived Adipocyte Dedifferentiation and Migration into Fat Grafts in A Murine Model.

BACKGROUND: The unstable recipient conditions after fat grafting remains an obstacle for tissue volumization. The interaction between fat grafts and recipient sites is not fully understood. We hypothesize that recipient-derived adipocytes undergo dedifferentiation and migrate into fat grafts in tissue regeneration. METHODS: To observe the participation from recipient fat pad, we established a recipient adipocyte-tracing model where 0.2 ml inguinal fat from ten 8-week-old C57BL/6 mice was grafted to ten tamoxifen-treated AdipoqCre;mT/mG mice. Next, to evaluate the impact of physical force on recipient fat and fat graft, murine internal expansion model was established by implanting a 1 ml internal expander upon the inguinal fat pad of the lineage tracing mice that received fat graft from C57BL/6 mice. Transplanted adipose tissue was collected and analyzed by immunostaining of GFP, tdTomato, perilipin, CD31. RESULTS: In the observing model, immunostaining revealed that both GFP+ and tdTomato+ cells from recipient fat pad presented in fat grafts. Among the GFP+ cells, most of them were perilipin+ adipocytes and other perilipin- cells co-expressed OCT4, indicating dedifferentiated adipocytes. In the internal expansion model, internal expansion increased GFP+ cells in fat graft. Both OCT4+/GFP+ (0.23 ± 0.01 vs. 0.12 ± 0.04) and perilipin+/GFP+ (0.17 ± 0.02 vs. 0.06 ± 0.01) cells were increased in the expanded group, compared with control. CONCLUSIONS: Host-derived adipocytes participate in fat graft regeneration through migration and dedifferentiation, which could be enhanced by internal expansion to increase fat graft retention rate. Further study using larger animal model is needed, since this is a murine study.

Dedifferentiated fat cells: current applications and future directions in regenerative medicine.

Stem cell therapy is the most promising treatment option for regenerative medicine. Therapeutic effect of different stem cells has been verified in various disease model. Dedifferentiated fat (DFAT) cells, derived from mature adipocytes, are induced pluripotent stem cells. Compared with ASCs and other stem cells, the DFAT cells have unique advantageous characteristics in their abundant sources, high homogeneity, easily harvest and low immunogenicity. The DFAT cells have shown great potential in tissue engineering and regenerative medicine for the treatment of clinical problems such as cardiac and kidney diseases, autoimmune disease, soft and hard tissue defect. In this review, we summarize the current understanding of DFAT cell properties and focus on the relevant practical applications of DFAT cells in cell therapy in recent years.

Transplantation of in vitro prefabricated adipose organoids attenuates skin fibrosis by restoring subcutaneous fat and inducing dermal adipogenesis.

Localized scleroderma is a complex autoimmune disease characterized by dermal fibrosis and loss of cutaneous fat. While cytotherapy offers a promising treatment option, stem cell transplantation results in low survival rates and fails in target cell differentiation. In this study, we aimed to prefabricate syngeneic adipose organoids (ad-organoids) using microvascular fragments (MVFs) via three-dimensional (3D) culturing and transplant them beneath the fibrotic skin to restore subcutaneous fat and reverse the pathological manifestation of localized scleroderma. We employed 3D culturing of syngeneic MVFs with stepwise angiogenic and adipogenic induction to produce ad-organoids and evaluated their microstructure and paracrine function in vitro. C57/BL6 mice with induced skin scleroderma were treated with adipose-derived stem cells (ASCs), adipocytes, ad-organoids, and Matrigel, and the therapeutic effect was assessed histologically. Our results showed that ad-organoids derived from MVF contained mature adipocytes and a well-established vessel network, secreted multiple adipokines, promoted adipogenic differentiation of ASCs, and suppressed proliferation and migration of scleroderma fibroblasts. Subcutaneous transplantation of ad-organoids reconstructed the subcutaneous fat layer and stimulated dermal adipocyte regeneration in bleomycin-induced scleroderma skin. It reduced collagen deposition and dermal thickness, attenuating dermal fibrosis. Moreover, ad-organoids suppressed macrophage infiltration and promoted angiogenesis in the skin lesion. In conclusion, 3D culturing of MVFs with stepwise angiogenic and adipogenic induction is an effective strategy for the fabrication of ad-organoids, and the transplantation of prefabricated ad-organoids can improve skin sclerosis by restoring cutaneous fat and attenuating skin fibrosis. These findings offer a promising therapeutic approach for the treatment of localized scleroderma.

Internal Expansion Preconditioning of Recipient Site Increases Fat Graft Retention by Enriching Stem Cell Pool and Inducing Browning in Rats.

BACKGROUND: Fat grafting has an unsatisfactory retention rate for breast reconstruction due to poor recipient conditions. The contribution of the recipient site to fat grafts is unknown. In this study, we hypothesize that tissue expansion could improve fat graft retention by preconditioning the recipient fat fad. METHODS: Over-expansion was achieved using 10 ml cylindrical soft-tissue expanders implanted beneath the left inguinal fat flaps of 16 Sprague-Dawley rats (weighing 250-300 g), whose contralateral parts were implanted with a silicone sheet as control. After 7-days expansion, the implants were removed and both inguinal fat flaps received 1 ml of fat grafts from 8 donor rats. Fluorescent dye-labeled mesenchymal stromal cells (MSCs) were injected into rats and tracked in vivo by fluorescence imaging. Transplanted adipose tissue was harvested at 4 and 10 weeks (n = 8 per time point). RESULTS: After 7-days expansion, OCT4+ (p = 0.0002) and Ki67+ (p = 0.0004) positive area were increased with up-regulated expression of CXCL12 in recipient adipose flaps. An increasing number of DiI-positive MSCs were observed in the expanded fat pad. At 10 weeks after fat grafting, retention rate, measured using the Archimedes principle, was much higher in the expanded group than that in the non-expanded group (0.3019 ± 0.0680 vs. 0.1066 ± 0.0402, p = 0.0005). Histologic and transcriptional analyses revealed that angiogenesis was enhanced, and macrophage infiltration was decreased in the expanded group. CONCLUSIONS: Internal expansion preconditioning increased circulating stem cells into recipient fat pad and contributed to improved fat graft retention.

Corrigendum: Spontaneous browning of white adipose tissue improves angiogenesis and reduces macrophage infiltration after fat grafting in mice.

[This corrects the article DOI: 10.3389/fcell.2022.845158.].

Condensing of Low-Density Fat by Mechanical Process Improves Fat Retention and Reduces Oil Cyst Formation in Breast Reconstruction.

BACKGROUND: Although autologous fat grafting is a useful adjunct for breast reconstruction, its indications remain limited as large-volume fat grafting results in high absorption and complication rates. Low-density fat includes small numbers of viable cells and considerable oil, resulting in nodules and oil cysts. This study evaluated the volumization effect and complications with combined fat grafting of condense low-density fat and high-density fat. METHODS: This retrospective, single-center study included 25 patients who underwent combined grafting of condensed low-density fat and high-density fat (CLDF + HDF) and 20 patients who underwent conventional Coleman fat grafting for breast reconstruction from December 2017 to January 2022. Retention rates and complications were evaluated by magnetic resonance imaging and ultrasound rates. Patient satisfaction was evaluated using a typical Likert scale. Photographs were taken and imageological examinations were performed before and after treatment. OUTCOMES: Graft retention rate was higher in patients who underwent CLDF + HDF than Coleman fat grafting for breast reconstruction (38.40 ± 4.41% vs. 31.43 ± 5.43%, p <0.05). One patient in the CLDF + HDF grafting group, compared with twelve in the Coleman fat grafting group, developed oil cysts exceeding 1 cm. Patient satisfaction rate was higher in the CLDF + HDF grafting group. CONCLUSIONS: Mechanical processes can concentrate the cellular content of LDF and remove oil, condensing LDF to the level of HDF. Combined grafting of CLDF optimized by mechanical processing and HDF is effective for breast reconstruction, with a higher retention rate and a lower incidence of complications than conventional Coleman fat grafting. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Fat transplantation induces dermal adipose regeneration and reverses skin fibrosis through dedifferentiation and redifferentiation of adipocytes.

BACKGROUND: Localized scleroderma causes cosmetic disfigurement, joint contractures, and other functional impairment, but no currently available medications can reverse the resulting skin lesions. Fat grafting is beneficial for reversing skin fibrosis; however, the mechanism by which adipose tissue transplantation contributes to lesion improvement has not been fully clarified. The purpose of our study was to verify the therapeutic effect of fat grafts in reversing skin fibrosis. METHODS: Inguinal fat pads from AdipoqCreER+;mT/mG mice, which were treated with tamoxifen, were transplanted to the skin lesion in bleomycin-treated wild-type C57 mice. Tdtomato transgenic mice-derived adipocytes, adipose-derived stem cells (ASCs), dedifferentiated adipocytes (DAs) were embedded in matrigel and transplanted beneath the skin lesion of bleomycin-treated wild-type C57 mice. A transwell co-culture system was used to verify the effect of ASCs, adipocytes or DAs on scleroderma fibroblasts or monocytes. RESULTS: Adipocytes from the fat grafts could undergo dedifferentiation and redifferentiation for dermal adipose tissue re-accumulation within the skin lesion. Moreover, compared with ASCs and adipocytes, DAs show greater potency of inducing adipogenesis. ASCs and DAs showed comparable effect on inducing angiogenesis and suppressing macrophage infiltration in fibrotic skin. Co-culture assay showed that DAs and ASCs were able to reduce fibrosis-related genes in human scleroderma fibroblasts and drive M2 macrophage polarization. CONCLUSION: Our results indicated that adipocytes would transform into a more functional and dedifferentiated state and reverse dermal fibrosis, by promoting dermal adipose tissue regeneration, improving angiogenesis, suppressing macrophage-mediated inflammation and myofibroblast accumulation.

Ceiling culture of human mature white adipocytes with a browning agent: A novel approach to induce transdifferentiation into beige adipocytes.

Excess and dysfunctional adipose tissue plays an important role in metabolic diseases, including obesity, atherosclerosis and type 2 diabetes mellitus. In mammals, adipose tissue is categorized into two types: white and brown. Adult brown tissue is mainly composed of beige adipocytes, which dispose of stored energy as heat and have become increasingly popular as a therapeutic target for obesity. However, there is still a paucity of cell models that allow transdifferentiation of mature white adipocytes into beige adipocytes, as seen in vivo. Here, we describe a novel, ceiling culture-based model of human mature white adipocytes, which transdifferentiate into beige adipocytes under the mechanical force and hypoxia of ceiling culture. We also show that the use of rosiglitazone and rapamycin can modulate transdifferentiation, up and down regulating expression of beige adipocyte-specific genes, respectively. Rosiglitazone additionally facilitated the upregulation of fatty acid lipolysis and oxidation genes. Finally, these beige adipocytes derived from dedifferentiated adipocytes exhibited a progenitor-specific phenotype, with higher expression of mature adipocyte-specific genes than adipocyte-derived stem cells. Overall, we report a novel approach to conveniently cultivate beige adipocytes from white adipocytes in vitro, suitable for mechanistic studies of adipose biology and development of cell and drug therapies in the future.

Corrigendum: Spontaneous browning of white adipose tissue improves angiogenesis and reduces macrophage infiltration after fat grafting in mice.

[This corrects the article DOI: 10.3389/fcell.2022.845158.].

The fates of different types of adipose tissue after transplantation in mice.

Fat grafting is one of the most commonly applied procedure for soft-tissue repair. However, it remains unclear whether the type of adipose tissue would have any effects on fat graft survival. The present study aimed to determine fates of fat grafting of three different types of fat tissue. In this study, mice were randomly divided into three groups, white adipose tissue (WAT) group, beige adipose tissue (beige AT) group and brown adipose tissue (BAT) group. Before transplantation, donor mice were injected with rosiglitazone or phosphate-buffered saline (PBS). The WAT and BAT were obtained from PBS-treated mice while beige AT was obtained from the rosiglitazone-treated mice. Three types of fat tissue (150 mg each) were transplanted in three groups, respectively, and harvested at 2, 4 or 12 weeks. The BAT and beige AT contained smaller adipocytes and expressed higher level of uncoupling protein-1 gene. The retention rate of the transplanted fat was significantly higher for beige than for white fat, but was significantly lower for brown than for white fat. Transplanted brown fat was characterized by upregulated inflammation and high endoplasmic reticulum stress. By contrast, fat grafts in beige AT group showed the best adipogenic capacity, moderate inflammation level and superior angiongenesis. In vitro, under hypoxic condition, fewer apoptotic cells were found in beige adipocyte group than that in brown and white adipocyte group. Conditioned medium from brown adipocytes induced M1 polarization of RAW 264.7 macrophages while that from beige adipocytes effectively promoted M2 polarization. Therefore, we suggest that beige AT provides a new potential choice for fat grafting because of low inflammation and superior survival but BAT might not be ideal for fat grafting due to its poor survival.

Adipose-Derived Stem Cell-Enriched Lipotransfer Reverses Skin Sclerosis by Suppressing Dermal Inflammation.

BACKGROUND: Scleroderma is a chronic autoimmune disease with an incidence of 2.7 per 100,000 people. Traditional lipotransfer has been used to treat atrophic sclerotic skin. Enzymatically processed cell-assisted lipotransfer and mechanically processed stromal vascular fraction gel are fat products with abundant adipose-derived stem cells. This study assessed whether adipose-derived stem cell-enriched lipotransfer elicits superior therapeutic effects on scleroderma. METHODS: Scleroderma was induced in nude mice by injections of bleomycin for 4 weeks. Human-derived Coleman fat, cell-assisted lipotransfer, or stromal vascular fraction gel (0.1 ml) was injected into sclerotic lesions. Histologic examinations, terminal deoxynucleotidyl transferase dUTP nick end labeling, and expression analyses of inflammatory factors in skin lesions and transferred fat were performed at 4 weeks after implantation. RESULTS: Dermal thickness was lower in the groups injected with Coleman fat (339.0 ± 19.66 µm), cell-assisted lipotransfer (271.0 ± 16.15 µm), and stromal vascular fraction gel (197.8 ± 12.99 µm) than in the group injected with phosphate-buffered saline (493.3 ± 28.13 µm) ( p < 0.05). The numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling + and Mac2 + cells in fat tissue were significantly higher in the group injected with Coleman fat than in those injected with stromal vascular fraction gel and cell-assisted lipotransfer. Expression of monocyte chemotactic protein-1 and interleukin-6 was significantly lower in the adipose-derived stem cell-enriched groups than in the Coleman fat group. Histologic analysis showed there were far fewer macrophages and myofibroblasts in skin lesions in the adipose-derived stem cell-enriched groups than in the Coleman fat group. CONCLUSIONS: Transplantation of stromal vascular fraction gel and cell-assisted lipotransfer, which contain abundant adipose-derived stem cells, reduces the levels of apoptotic cells and inflammation, significantly reverses skin sclerosis, and elicits superior anti-inflammatory and antifibrotic effects on scleroderma. CLINICAL RELEVANCE STATEMENT: This study provided an alternative adipose-based therapy, adipose-derived stem cell-enriched fat, for sclerotic lesions and showed its validity for interfering with the inflammation and fibrosis.