Cell‐assisted lipotransfer: Friend or foe in fat grafting? Systematic review and meta‐analysis

Effectiveness and Safety of Different Methods of Assisted Fat Grafting: A Network Meta-Analysis

OBJECTIVE

Numerous studies have proposed the utilization of stromal vascular fraction (SVF), adipose-derived stem cells (ADSCs), and platelet products as auxiliary grafting techniques to improve the survival rate of fat grafts. This study aimed to evaluate the efficacy and safety of various fat grafting methods since 2010 through a network meta-analysis, aiming to identify the most effective technique for fat grafting.

METHODS

Clinic trials on assisted fat grafting were searched from Pubmed, Embase, Web of Science, and the Cochrane Library, spanning the period from January 1, 2010 to March 2024. The risk of bias in the included trials was meticulously assessed using the Cochrane risk of bias tool. The survival rate of fat grafts served as the primary evaluation metric for effectiveness, while complications were employed as the indicator for safety.

RESULTS

The study incorporated 31 clinic trials, involving a total of 1656 patients. The findings indicated that the survival rate with assisted fat grafting significantly surpassed that of simple fat grafting (SUCRA, 10.43%). Notably, ADSC-assisted fat grafting exhibited the highest survival rate (SUCRA, 82.17%), followed by Salvia miltiorrhiza (SM)-assisted fat grafting (SUCRA, 69.76%). In terms of safety, the most prevalent complications associated with fat grafting were fat sclerosis and fat necrosis. Adc-assisted fat grafting was correlated with the lowest incidence of complications (SUCRA, 41.00%), followed by simple fat grafting (SUCRA, 40.99%). However, PRP-assisted (SUCRA, 52.86%) and SVF-assisted fat grafting (SUCRA, 65.14%) showed higher complication rates.

CONCLUSION

Various methods of assisted fat grafting can significantly enhance the survival rate, but they often fail to effectively mitigate the incidence of complications. Compared to other methods, adipose mesenchymal stem cells-assisted fat grafting consistently yielded a higher survival rate of grafts and fewer complications. Consequently, this approach represents a relatively effective method for assisting in fat grafting at present.

LEVEL OF EVIDENCE III

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 .

Comparative Efficacy and Safety of Cell-Assisted and Conventional Lipotransfer in Facial Filling: A Systematic Review and Meta-Analysis

PURPOSE

We aim to compare the efficacy and safety of cell-assisted lipotransfer (CAL) and conventional lipotransfer (CLT) in facial filling.

METHODS

The PubMed and Embase databases were searched for relevant publications until February 2023. All studies evaluating the efficacy and safety of cell-assisted and conventional lipotransfer in facial filling were included. We calculated pooled standardized mean difference (SMD) and 95% CIs for continuous outcomes and pooled risk ratio (RR) with 95% CIs for binary outcomes. The Cochrane's Risk of Bias Tool and the Newcastle-Ottawa Scale (NOS) were used to evaluate the quality of studies.

RESULTS

A total of 15 studies with 737 patients were included in this analysis. The fat survival rate and patient satisfaction rate were significantly higher in the CAL group compared to the CLT group (SMD: 3.04, 95% CI 2.09-3.99; RR: 1.34, 95% CI 1.08-1.67). However, no significant difference in complication rates (RR: 0.95, 95% CI 0.50-1.81) and a lower secondary operation rate in the CAL group (RR: 0.52, 95% CI 0.03-0.82) were observed. No obvious publication bias was observed in the funnel plot (Egger's P values = 0.084 and 0.403).

CONCLUSIONS

Based on the pooled results, we tentatively conclude that CAL may have superior fat survival rate and satisfaction rate compared to CLT in facial filling, without compromising patient safety. However, the majority of the included studies were observational studies with small sample sizes. Future research should focus on investigating the long-term efficacy and safety of these techniques.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

Evaluating the Efficacy of Dedifferentiated Fat Cells (DFATs) vs Adipose-Derived Stem Cells (ASCs) in Enhancing the Viability of Fat Grafts

BACKGROUND

Enhancing graft fat survival remains a paramount challenge in autologous fat transplantation surgeries. Dedifferentiated fat cells (DFATs) and adipose-derived stem cells (ASCs) represent 2 pivotal cells with potential to improve fat graft survival rates.

OBJECTIVES

In this study we aimed to compare the effectiveness of DFATs and ASCs in promoting fat graft survival, emphasizing their adipogenic and angiogenic capabilities.

METHODS

Both in vitro and in vivo experiments were conducted. In vitro assessments compared adipogenesis, angiogenesis, osteogenesis, chondrogenesis, cell migration abilities, and surface markers. For in vivo evaluation, a cell-assisted lipotransfer animal model was employed to gauge graft volume retention and histological morphology. Analysis techniques included hematoxylin and eosin staining, Western blotting, and real-time polymerase chain reaction.

RESULTS

In vitro findings suggested a slight superiority of DFATs in adipogenesis and angiogenesis compared to ASCs. In vivo tests demonstrated both cell types surpassed the control in terms of graft volume retention, with the DFATs group marginally outperforming in retention rates and the ASC group presenting a slightly enhanced graft tissue structure.

CONCLUSIONS

Our study underscores the distinct advantages of DFATs and ASCs in bolstering fat graft survival, offering potentially novel insights for plastic surgeons aiming to elevate fat graft survival rates.

In Vitro Study of Thymosin Beta 4 Promoting Transplanted Fat Survival by Regulating Adipose-Derived Stem Cells

BACKGROUND

Autologous fat grafting (AFG) has emerged as a highly sought-after plastic surgery procedure, although its success has been hampered by the uncertain fat survival rate. Current evidence suggests that adipose-derived stem cells (ADSCs) may contribute to fat retention in AFG. In previous studies, it was confirmed that thymosin beta 4 (Tβ4) could enhance fat survival in vivo, although the precise mechanism remains unclear.

METHODS

ADSCs were isolated from patients undergoing liposuction and their proliferation, apoptosis, anti-apoptosis, and migration were analyzed under Tβ4 stimulation using cell counting kit-8, flow cytometry, wound healing assay, and real-time quantitative PCR. The mRNA levels of genes relating to angiogenesis and Hippo signaling were also determined.

RESULTS

Tβ4 at 100 ng/mL (p-value = 0.0171) and 1000 ng/mL (p-value = 0.0054) significantly increased ADSC proliferation from day 1 compared to the control group (0 ng/mL). In addition, the mRNA levels of proliferation-associated genes were elevated in the Tβ4 group. Furthermore, Tβ4 enhanced the anti-apoptotic ability of ADSCs when stimulated with Tβ4 and an apoptotic induction reagent (0 ng/mL vs. 1000 ng/mL, p-value = 0.011). Crucially, the mRNA expression levels of angiogenesis-related genes and critical genes in the Hippo pathway were affected by Tβ4 in ADSCs.

CONCLUSIONS

Tβ4 enhances adipose viability in AFG via facilitating ADSC proliferation and reducing apoptosis, and acts as a crucial positive regulator of ADSC-associated angiogenesis. Additionally, Tβ4 could be accountable for the phenotypic adjustment of ADSCs by regulating the Hippo pathway.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 transplant: Amazing growth and regeneration of cells and rebirth with the miracle of fat cells

BACKGROUNDS AND OBJECTIVE

During fat transplantation, adipose tissue is removed from the body and injected into different areas under the skin. The goal of this review article is to look into the efficacy and applicability of fat transplantation in regenerative medicine and rejuvenation, including Nanofat, Microfat, and Millifat.

METHODS

As a search strategy and study selection, we searched the PubMed and Medline databases until 2023 using related keywords (e.g., Nanofat, Microfat and Millifat, Regenerative Medicine, and Rejuvenation).

RESULTS

Autologous fat transplantation has no risk of an allergic reaction or rejection of the transplant by the individual. Autologous adipose tissue is considered an ideal filler for facial rejuvenation and is suggested as the most biocompatible and non-immunogenic skin filler. Adipose tissue transplant may have semi-permanent to permanent effects. According to recent reports, adipose tissues possess a high percentage of mature stem cells. The effect of regenerating adipose tissue and its intrinsic cells can be described as an obvious process. Variations in the sizes of adipose tissues can result in different results depending on the surgical site. Based on topographic assessment, graft fats are assigned depending on the anatomical locations and the size such as Millifat (2-2.5 mm), Microfat (1 mm), and Nanofat (500 μm or less).

CONCLUSION

Some characteristics of fat tissue increase its effectiveness, such as increasing stem cells, growth factors, cytokines, and compounds effective in repair, regeneration, and rejuvenation.

Increased Fat Graft Survival by Promoting Adipocyte Dedifferentiation

BACKGROUND

Some adipocytes undergo dedifferentiation after fat transplantation, and this may affect the survival of fat grafts. However, this effect has not been adequately studied.

OBJECTIVES

This study aimed to clarify the effect of promoting the dedifferentiation of mature adipocytes on the survival of fat grafts.

METHODS

Mature adipocytes and adipose stem cells (ASCs) were treated with OSI-906 (a specific inhibitor of insulin receptor and insulin-like growth factor-1 receptor) in vitro, and then the dedifferentiation of mature adipocytes and the proliferation of ASCs were evaluated. In the in vivo experiment, human lipoaspirates mixed with phosphate-buffered saline (Group A) or OSI-906 (Group B) were compared in nude mice. Grafts were harvested at 2, 8, and 12 weeks, and volume retention rate, histologic, and immunohistochemical analyses were conducted.

RESULTS

OSI-906 can promote the dedifferentiation of mature adipocytes and inhibit the proliferation of ASCs. At 12 weeks, Group B showed a better volume retention rate (mean [standard deviation, SD], 62.3% [7.61%]) than group A (47.75% [6.11%]) (P < .05). Moreover, viable adipocytes and vascularization showed greater improvement in Group B than in Group A.

CONCLUSIONS

This study suggests that promoting the dedifferentiation of mature adipocytes can improve the survival rate and quality of fat grafts.

Adipose-derived stem cells exosome and its potential applications in autologous fat grafting

Recently, there has been renewed interest in autologous fat grafting both for its filler and regenerative traits. The universal application, however, has been impeded by the unstable survival rates and complications. There has been substantial research undertaken on the role of adipose-derived stem cells (ADSCs) involved in fat graft fates including angiogenesis, adipogenesis, and inflammatory regulation. As the effectors of their parental cells, ADSC-derived exosomes (ADSC-exos) encapsulating multiple bioactive cargoes mediate cell-to-cell communication in a paracrine manner. ADSC-exos have received much attention for their biocompatible and efficient therapeutic potentials as "cell-free therapy" in plastic surgery, including increasing fat grafting survival rates. In this review, we summarize the current knowledge about the biological basis of ADSC-exos, ADSC-related mechanisms of fat survival, research updates of ADSC-exos in autologous fat grafting, and discuss some challenges along with research prospects.

The efficacy of cell-assisted versus conventional lipotransfer: A systematic review and meta-analysis

Autologous lipotransfer is an essential component of soft tissue reconstruction. However, it is not widely applied or accepted by surgeons due to its unstable survival rate and uncertain efficacy. The cell-assisted fat transfer (CAL) is a promising technique that increases the fat survival rate. However, it is controversial based on various clinical studies. Here, we assessed the fat survival and complication rates of CAL, compared to the conventional autologous lipotransfer. To conduct our research, two reviewers independently screened related articles published in Medicine (via PubMed), EMBASE, Cochrane Library, and Web of Science. The combined effect estimates for efficacy evaluation was performed by the Review Manager software (RevMan 5.4.1). In total, 14 articles were included in our analysis (n = 722). Based on our analysis, the survival rate of the fat graft in CAL was significantly higher than the conventional fat grafting group (non-CAL group) (SMD = 2.81, 95%CI [1.54, 4.08], P < 0.01). In the subgroup, the fat retention of CAL in the facial filling was higher than the conventional one (SMD = 3.01, 95%CI [1.68, 4.33], P < 0.01). After breast augmentation, however, the difference between the experimental and control group was not statistically significant (SMD = 1.80, 95%CI [-0.31, 3.91], P = 0.09). Moreover, the CAL group exhibited comparable complications as the non-CAL group. Based on our analysis, the CAL group was significantly better than the conventional lipotransfer in terms of fat survival, particularly, during facial filling. However, it failed to reduce the complication rate, compared to the non-CAL group.

Role of adipose tissue grafting and adipose-derived stem cells in peripheral nerve surgery

The application of autologous fat grafting in reconstructive surgery is commonly used to improve functional form. This review aims to provide an overview of the scientific evidence on the biology of adipose tissue, the role of adipose-derived stem cells, and the indications of adipose tissue grafting in peripheral nerve surgery. Adipose tissue is easily accessible through the lower abdomen and inner thighs. Non-vascularized adipose tissue grafting does not support oxidative and ischemic stress, resulting in variable survival of adipocytes within the first 24 hours. Enrichment of adipose tissue with a stromal vascular fraction is purported to increase the number of adipose-derived stem cells and is postulated to augment the long-term stability of adipose tissue grafts. Basic science nerve research suggests an increase in nerve regeneration and nerve revascularization, and a decrease in nerve fibrosis after the addition of adipose-derived stem cells or adipose tissue. In clinical studies, the use of autologous lipofilling is mostly applied to secondary carpal tunnel release revisions with promising results. Since the use of adipose-derived stem cells in peripheral nerve reconstruction is relatively new, more studies are needed to explore safety and long-term effects on peripheral nerve regeneration. The Food and Drug Administration stipulates that adipose-derived stem cell transplantation should be minimally manipulated, enzyme-free, and used in the same surgical procedure, e.g. adipose tissue grafts that contain native adipose-derived stem cells or stromal vascular fraction. Future research may be shifted towards the use of tissue-engineered adipose tissue to create a supportive microenvironment for autologous graft survival. Shelf-ready alternatives could be enhanced with adipose-derived stem cells or growth factors and eliminate the need for adipose tissue harvest.

Adipose-Derived Stem Cells Exosomes Improve Fat Graft Survival by Promoting Prolipogenetic Abilities through Wnt/β-Catenin Pathway

Autologous fat grafting has been widely used in plastic surgery in recent years, but the unstable retention of fat graft has always been a key clinical problem. Adipose tissue has poor tolerant to ischemia, so the transplanted adipose tissue needs to rebuild blood supply at an early stage in order to survive stably. Our previous study has found that comparing to human foreskin fibroblast exosome (HFF-Exo), human adipose-derived stem cells exosome (hADSC-Exo) can significantly improve the proliferation of vascular endothelial cells and the angiogenic effect of artificial dermal preconstructed flaps. Therefore, the ability of hADSC-Exo to improve the retention of adipose grafts and its potential regenerative mechanism aroused our strong interest. In this study, we applied hADSC-Exo and HFF-Exo to adipose grafts and explored the potential regeneration mechanism through various means such as bioinformatics, immunofluorescence, immunohistochemistry, and adipogenic differentiation. The results showed that hADSC-Exo can significantly promote grafts angiogenesis and adipogenic differentiation of ADSC to improve the retention of fat grafts and may downregulate the Wnt/β-catenin signaling pathway to promote the adipogenic differentiation. In summary, our results provide a theoretical basis for the clinical translation of hADSC-Exo in fat grafting.

The oncological safety of autologous fat grafting: a systematic review and meta-analysis

Objective

To present a systematic review of the literature and a meta-analysis evaluating the oncological safety of autologous fat grafting (AFG).

Summary background data: AFG for breast reconstruction presents difficulties during follow-up radiological exams, and the oncological potential of grafted fat is uncertain. Previous studies confirmed that the fatty tissue could be transferred under a good condition suitable would not interfere with mammographic follow-up, although the issue of oncological safety remains.

Methods

We reviewed the literature published until 01/18/2021. The outcomes were overall survival (OS), disease-free survival (DFS), and local recurrence (LR). We included studies that evaluated women with breast cancer who undergone surgery followed by reconstruction with AFG. We synthesized data using the inverse variance method on the log-HR (log of the hazard ratio) scale for time-to-event outcomes using RevMan. We assessed heterogeneity using the Chi² and I² statistics.

Results

Fifteen studies evaluating 8541 participants were included. The hazard ratios (HR) could be extracted from four studies, and there was no difference in OS between the AFG group and control (HR 0.9, 95% CI 0.53 to 1.54, p = 0.71, I² = 58%, moderate certainty evidence), and publication bias was not detected. The HR for DFS could be extracted from six studies, and there was no difference between the AFG group and control (HR 1.01, 95% CI 0.73 to 1.38, p = 0.96, I² = 0%, moderate certainty evidence). The HR for LR could be extracted from ten studies, and there was no difference between the AFG group and control (HR 0.86, 95% CI 0.66 to 1.12, p = 0.43, I² = 1%, moderate certainty evidence).

Conclusion

According to the current evidence, AFG is a safe technique of breast reconstruction for patients that have undergone BC surgery and did not affect OS, DFS, or LR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09485-5.

Amniotic growth factors enhanced human pre-adipocyte cell viability and differentiation under hypoxia

One of the major drawbacks associated with autologous fat grafting is unpredictable graft retention. Various efforts to improve the survivability of these cells have been explored, but these methods are time‐consuming, complex, and demand significant technical skill. In our study, we examine the use of cryopreserved amniotic membrane as a source of exogenous growth factors to improve adipocyte survivability under normal and hypoxic conditions. Human primary preadipocytes were cultured in a gelatin‐ferulic acid (Gtn‐FA) hydrogel with variable oxygen concentration and treated with amniotic membrane‐derived condition medium (CM) for 7 days. This hydrogel provides a hypoxic environment and also creates a 3D cell culture to better mimic recipient site conditions. The O₂ concentration in the hydrogel was measured by electron paramagnetic resonance oxygen imaging (EPROI). The conjugation of FA was confirmed by FTIR and NMR spectroscopy. The cell viability and adipocyte differentiation were analyzed by alamarBlue™ assay, Oil Red O staining, and RT‐qPCR. The expression of genes: Pref‐1, C/EBP β, C/EBP α, PPAR‐ƴ, SLC2A4, and VEGF‐A were quantified. The cell viability results show that the 50% CM showed significantly higher cell pre‐adipocyte cell viability. In addition, compared to normal conditions, hypoxia/CM provided higher PPAR‐ƴ (p < .05), SLC2A4, and VEGF‐A (p < .05) (early and terminal differentiating markers) mRNA expression. This finding demonstrates the efficacy of amniotic CM supplementation as a novel way to promote adipocyte survival and retention via the expression of key gene markers for differentiation and angiogenesis.

Cell-Assisted Lipotransfer in Breast Augmentation Surgery: Clinical Outcomes and Considerations for Future Research

Autologous fat transfer is a widely used surgical technique, chosen by numerous plastic surgeons for breast augmentation surgery. This technique is based on three steps: 1. harvesting of the lipoaspirate from the patient, 2. centrifugation and removal of the top, oily, layer, and 3. implantation in the patient’s breast(s). It has been associated with various complications, including post-surgical fat resorption, as measured quantitatively with MRI, CT, and other 3D-quantification systems.

Adipose-derived stem cells have been explored as a means of addressing fat resorption. They can be separated from the lipoaspirate following centrifugation, and enzymatically purified from unwanted debris, with collagenase, forming the stromal vascular fraction. The stromal vascular fraction is then recombined with the graft volume prior to implantation. This novel technique, referred to as “cell-assisted lipotransfer”, has shown promising results in terms of reducing fat resorption. These results are due to the pro-angiogenic and pro-adipogenic ability of the stem cells, which allow the graft to address the conditions of ischemia more effectively than autologous fat transfer.

The aim of this review is to explore the ways in which cell-assisted lipotransfer is different from the autologous fat transfer, as well as how and why adipose-derived stem cells may contribute towards limiting fat resorption. The immunological background of these cells is discussed in detail, while grounds for further development are discussed, by means of the administration of external growth factors, which could, potentially, maximize outcomes, while limiting complications.

Human antigen R promotes angiogenesis of endothelial cells cultured with adipose stem cells derived exosomes via overexpression of vascular endothelial growth factor in vitro

Recent studies showed that exosomes obtained from adipose-derived stem cells (ADSCs) could improve the angiogenesis of fat grafts via overexpression of vascular endothelial growth factor (VEGF). Human antigen R (HuR) promotes the expression of VEGF in many cancers, but the effect of HuR in normal endothelial cells in the presence of ADSC-derived exosomes remains unclear. We aimed to investigate the effect of HuR on the expression of VEGF and angiogenesis of human umbilical vein endothelial cells (HUVECs) cultured with ADSCs-derived exosomes. The HuR-overexpressed HUVECs (HuR-HUVECs) were cocultured with ADSCs-derived exosomes. qRT-PCR and Western blotting were performed to examine the stability and expression of VEGF-A mRNA and protein. The proliferation, migration, and proangiogenic capacity of HuR-HUVECs were evaluated using cell counting kit-8 (CCK-8), scratch wound healing, and Matrigel tube formation assay. qRT-PCR showed that HuR-HUVECs had higher expression and slower attenuation of VEGF-A mRNA. Western blotting confirmed higher expression of VEGF-A in HuR-HUVECs. CCK-8, scratch wound healing, and Matrigel tube formation assay demonstrated an increased proangiogenic effect in HuR-HUVECs. HuR promotes angiogenesis of HUVECs cocultured with ADSCs-derived exosomes via stabilization and overexpression of VEGF in vitro. The HuR/VEGF pathway is an important regulatory mechanism of angiogenesis in endothelial cells.

A Systematic Review on Extracellular Vesicles-Enriched Fat Grafting: A Shifting Paradigm

BACKGROUND

Recent evidence confirms that mesenchymal stem cells (MSCs) facilitate angiogenesis mainly through paracrine function. Extracellular vesicles (EVs) are regarded as key components of the cell secretome, possessing functional properties of their source cells. Subsequently, MSC-EVs have emerged as a novel cell-free approach to improve fat graft retention rate.

OBJECTIVES

The authors sought to provide a systematic review of all studies reporting the utilization of MSC-EVs to improve graft retention rate.

METHODS

A systematic search was undertaken employing the Embase, PubMed, and Cochrane Central Register of Controlled Trials databases. Outcome measures included donor/receptor organism of the fat graft, study model, intervention groups, evaluation intervals, EV research data, and in vitro and in vivo results.

RESULTS

Of the total 1717 articles, 62 full texts were screened. Seven studies reporting on 294 mice were included. Overall, EV-treated groups showed higher graft retention rates compared with untreated groups. Notably, retention rate was similar following EV and MSC treatment. In addition to reduced inflammation, graft enrichment with EVs resulted in early revascularization and better graft integrity. Interestingly, hypoxic preconditioning of MSCs improved their beneficial paracrine effects and led to a more proangiogenic EV population, as observed by both in vitro and in vivo results.

CONCLUSIONS

MSC-EVs appear to offer an interesting cell-free alternative to improve fat graft survival. Although their clinical relevance remains to be determined, it is clear that not the cells but rather their secretome is essential for graft survival. Thus, a paradigm shift from cell-assisted lipotransfer towards "secretome-assisted lipotransfer" is well on its way.

LEVEL OF EVIDENCE: 4

Update on the Basic Science Concepts and Applications of Adipose-Derived Stem Cells in Hand and Craniofacial Surgery

SUMMARY

Adipose-derived stem cell therapy offers plastic surgeons a novel treatment alternative for conditions with few therapeutic options. Adipose-derived stem cells are a promising treatment because of their broad differentiation potential, capacity for self-renewal, and ease of isolation. Over the past decade, plastic surgeons have attempted to harness adipose-derived stem cells' unique cellular characteristics to improve the survival of traditional fat grafting procedures, a process known as cell-assisted lipotransfer. However, the full implications of cell-assisted lipotransfer in clinical practice remain incompletely understood, stressing the urgent need to assess the scientific evidence supporting adipose-derived stem cell-based interventions. Furthermore, with the strict regulatory climate surrounding tissue explantation therapies, reviewing the safety and efficacy of these treatments will clarify their regulatory viability moving forward. In this report, the authors provide a comprehensive, up-to-date appraisal of best evidence-based practices supporting adipose-derived stem cell-derived therapies, highlighting the known mechanisms behind current clinical applications in tissue engineering and regenerative medicine specific to plastic and reconstructive surgery. The authors outline best practices for the harvest and isolation of adipose-derived stem cells and discuss why procedure standardization will elucidate the scientific bases for their broad use. Finally, the authors discuss challenges posed by U.S. Food and Drug Administration oversight of these cell-based therapies and examine the role of adipose-derived stem cell-based applications in the future of plastic surgery.

Induced Beige Adipocytes Improved Fat Graft Retention by Promoting Adipogenesis and Angiogenesis

BACKGROUND

Fat grafting is commonly used in treating soft-tissue defects. However, the basic biology behind fat grafting is still not fully understood. Evidence of adipose browning into beige adipose tissue after fat grafting was revealed, but its role in fat grafting remains unclear.

METHODS

Induced beige adipocytes and adipose-derived stem cells were obtained from human lipoaspirates and labeled with green fluorescent protein. Nude mice were each injected with 300 mg of human lipoaspirate containing green fluorescent protein-labeled adipose-derived stem cells, green fluorescent protein-labeled induced beige adipocytes, or phosphate-buffered saline. Grafted fat was harvested after 1, 4, 8, and 12 weeks for immunohistochemistry and histologic examination. Graft retention, vascularization, and adipogenic gene expression were compared.

RESULTS

After 7 days' induction, adipocytes achieved browning with multilocular lipid droplets, increased mitochondria, and up-regulated browning gene expression. Fat graft retention rates at week 12 were significantly higher after injection of induced beige adipocytes than after injection of phosphate-buffered saline (46.0 ± 4.9 percent versus 31.0 ± 3.6 percent; p = 0.01), but were similar after injection of induced beige adipocytes and adipose-derived stem cells (p > 0.05). Induced beige adipocytes underwent rewhitening into white adipocytes and showed up-regulation of peroxisome proliferator-activated receptor-γ expression. Induced beige adipocytes enhanced angiogenesis, but were not active in forming vessel structures.

CONCLUSIONS

Induced beige adipocytes and adipose-derived stem cells were comparable in improving fat graft retention rates. Induced beige adipocytes promote angiogenesis in a paracrine manner and are prone to rewhitening after fat grafting.

Regenerative Strategy for Persistent Periprosthetic Leakage around Tracheoesophageal Puncture: Is It an Effective Long-Term Solution?

Autologous tissue-assisted regenerative procedures have been considered effective to close different types of fistula, including the leakage around tracheoesophageal puncture. The aim of this study was to retrospectively review 10 years of lipotransfer for persistent periprosthetic leakage in laryngectomized patients with voice prosthesis. Clinical records of patients who experienced periprosthetic leakage from December 2009 to December 2019 were reviewed. Patients receiving fat grafting were included. The leakage around the prosthesis was assessed with a methylene blue test. Twenty patients experiencing tracheoesophageal fistula enlargement were treated with fat grafting. At the one-month follow-up, all patients were considered improved with no leakage observed. At six months, a single injection was sufficient to solve 75% of cases (n 15), whereas 25% (n 5) required a second procedure. The overall success rate was 80% (n 16). Results remained stable for a follow-up of 5.54 ± 3.97 years. Fat grafting performed around the voice prosthesis, thanks to its volumetric and regenerative properties, is a valid and lasting option to solve persistent periprosthetic leakage.

Small extracellular vesicles from human adipose-derived mesenchymal stromal cells: a potential promoter of fat graft survival

BACKGROUND

Small extracellular vesicles (sEVs) with genetic information secreted by cells play a crucial role in the cellular microenvironment. In this study, our purpose is to explore the characteristics of the small extracellular vesicles of human adipose-derived mesenchymal stromal cells (hADMSC-sEVs) and studied the role of hADMSC-sEVs in improving the survival rate of grafted fat.

METHODS

In the present study, we used the transmission electron microscopy, nano-tracking analysis, nanoflow surface protein analysis, and zeta potential value to identify sEVs. SEVs' trajectory was traced dynamically to verify whether hADMSC-sEVs can be internalized into human umbilical vein endothelial cells (HUVECs) in vitro at different times. The angiogenic property of hADMSC-sEVs was observed by measuring the volume, weight, and histological analysis of the grafted fats in nude mouse models.

RESULTS

Our research showed that the hADMSC-sEVs were sEVs with double-layer membrane structure and the diameter of which is within 30-150 nm. hADMSC-sEVs exert biological influence mainly through internalization into cells. Compared with the control group, the hADMSC-sEVs group had a significantly higher survival rate of grafted fat, morphological integrity, and a lower degree of inflammation and fibrosis. And immunohistochemistry showed that hADMSC-sEVs significantly increased the neovascularisation and the expression of CD34, VEGFR2, and Ki-67 in the graft tissue.

CONCLUSIONS

As a potential nanomaterial, hADMSC-sEVs have been explored in the field of cell-free application of stem cell technology. hADMSC-sEVs promoted the survival of grafted fats by promoting the formation of new blood vessels, which is another promising progress in the field of regenerative medicine. We believe that hADMSC-sEVs will have a broad application prospect in the field of regenerative medicine in the future.

A pilot study on ex vivo expanded autologous adipose-derived stem cells of improving fat retention in localized scleroderma patients

In patients with localized scleroderma (LoS), facial deformity induced by subcutaneous atrophy greatly reduces life quality. Autologous fat grafting (AFG) is used for volume restoration but with low-fat retention due to various reasons. Adipose-derived stem cells (ADSCs) have shown potential effects in improving fat retention. We aimed to compare the feasibility and efficacy of improving fat retention in LoS patients among the ADSCs-assisted, the stromal vascular fraction (SVF)-assisted and conventional AFG methods. A pilot study with a 6-month follow-up among 18 LoS patients was conducted. Participants were randomly assigned into three AFG groups: conventional group, SVF-assisted group, and ADSCs-assisted group. The SVF-assisted group received SVF-assisted AFG at the SVF:fat ratio of 1:1. The ADSCs-assisted group received the mixture of ADSCs-enriched fat graft supplemented with 5 × 10⁵ ADSCs/mL fat. Volume retention was measured by magnetic resonance imaging, and clinical photographs were taken for outcome evaluation. At sixth-month follow-up, the fat retention of ADSCs-assisted group was 49.83 ± 3.61%, significantly higher than 31.75 ± 1.73% of SVF-assisted group (P = .0004), and 21.86 ± 1.68% of the conventional group (P < .0001). A significant difference of the fat retention was also observed between the SVF-assisted and conventional group (P = .0346). No severe adverse events occurred during the procedure and follow-up. This pilot study suggests that ADSCs-assisted AFG is a safe, feasible, and attractive alternative to conventional and SVF-assisted AFG in the correction of facial atrophy of LoS patients. Future studies with large patient samples are needed for confirmation. (Chinese Clinical Trial Registry, ChiCTR1900025717).

Comparison of the Efficacy and Safety of Cell-Assisted Lipotransfer and Platelet-Rich Plasma Assisted Lipotransfer: What Should We Expect from a Systematic Review with Meta-Analysis?

Due to the high absorption rate of traditional autologous fat grafting, cell-assisted lipotransfer (CAL) and platelet-rich plasma (PRP)-assisted lipotransfer were developed. The purpose of this article was to evaluate the efficacy and safety of CAL and PRP in promoting the survival of autologous fat grafting through systematic review and meta-analysis. We searched Pubmed, Cochrane Library, Web of Science, and EMBASE for clinical studies on CAL and PRP-assisted lipotransfer published from January 2010 to January 2020. Then a meta-analysis was performed to assess the efficacy of CAL and PRP-assisted lipotransfer through data analysis of fat survival rate. We also assessed the incidence of complications and multiple operations to analyze their safety. A total of 36 studies (1697 patients) were included in this review. Regardless of the recipient area, CAL and PRP-assisted lipotransfer significantly improved the fat survival rate (CAL vs non-CAL: 71% vs 48%, P < 0.0001; PRP vs non-PRP: 70% vs 40%, P < 0.0001; CAL vs PRP: 71% vs 70%, P = 0.7175). However, in large-volume fat grafting, such as breast reconstruction, both increased the incidence of complications and did not decrease the frequency of multiple operations after lipotransfer. Further prospective studies are needed to evaluate the clinical benefits of CAL and PRP-assisted lipotransfer.

Volume Retention After Facial Fat Grafting and Relevant Factors: A Systematic Review and Meta-analysis

BACKGROUND

Autologous fat grafting is common in facial reconstructive and cosmetic surgeries; the most important drawbacks are the high absorption rate and unpredictable volume retention rate. Surgeons usually make clinical judgements based on their own experience. Therefore, this study aimed to systematically and quantitatively review the volume retention rate of facial autologous fat grafting and analyse the relevant influencing factors.

METHODS

A systematic literature review was performed using the Medline, EMBASE, Cochrane Library, and Web of Science databases in October 2019 for articles that reported objectively measured volume retention rates of facial fat grafting. Patient characteristics, fat graft volumetric data, and complications were collected. A meta-analysis using a random-effects model was conducted to pool the estimated fat retention rate. Relevant factors were analysed and reviewed on the basis of subgroups.

RESULTS

We included 27 studies involving 1011 patients with facial fat grafting. The volume retention rate varied from 26 to 83%, with a mean follow-up of 3-24 months. The overall pooled retention rate was 47% (95% CI 41-53%). The volume measurement method significantly influenced the reported retention rate. A trend towards better retention was found for secondary fat grafting procedures and patients with congenital deformities. Only 2.8% of all patients had complications.

CONCLUSION

The exact percentage of facial fat grafts retained is currently unpredictable; the reported rate varies with different estimation methods. This review analysed studies that provided objectively measured volume retention rates, the pooled average percentage of facial fat graft retention (47%, 95% CI 41-53%), and relevant factors.

LEVEL OF EVIDENCE III

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 .

Exosomes from adipose-derived mesenchymal stem cells promote survival of fat grafts by regulating macrophage polarization via let-7c

The rate of fat graft survival is a critical aspect of successful surgery and has been a matter of concern for over 20 years. Owing to their anti-inflammatory effects and regenerative property, adipose-derived mesenchymal stem cells (AD-MSCs) have been adapted for clinical application in fat grafting, although the mechanism underlying their action remains unclear. Recently, exosomes derived from MSCs were suggested as a better alternative, and these exosomes have also been applied in diverse clinical therapies. Accumulating evidence suggests that MSCs modulate macrophage differentiation via exosome secretion, and the connection between macrophage regulation and the rate of fat graft survival has been established. Here, we identified that let-7c, the key factor in the regulatory process, is shuttled by AD-MSC-derived exosomes to downregulate the transcription factor CCAAT/enhancer-binding protein (C/EBP)-δ. The downregulation of C/EBP-δ resulted in the attenuation of pro-inflammatory M1 macrophages and elevation of anti-inflammatory M2 macrophages. These results suggest that AD-MSC-derived exosomes promote the survival of fat grafts by regulating macrophage polarization via let-7c. This is the first study to elucidate the mechanism underlying the promotion of the fat graft survival rate by AD-MSCs and to evaluate the immunotherapeutic potential of AD-MSC-derived exosomes in fat grafting.

In situ Adipogenesis in Biomaterials Without Cell Seeds: Current Status and Perspectives

For cosmetic and reconstructive purposes in the setting of small-volume adipose tissue damage due to aging, traumatic defects, oncological resections, and degenerative diseases, the current strategies for soft tissue replacement involve autologous fat grafts and tissue fillers with synthetic, bioactive, or tissue-engineered materials. However, they all have drawbacks such as volume shrinkage and foreign-body responses. Aiming to regenerate bioactive vascularized adipose tissue on biomaterial scaffolds, adipose tissue engineering (ATE) has emerged as a suitable substitute for soft tissue repair. The essential components of ATE include scaffolds as support, cells as raw materials for fat formation, and a tolerant local environment to allow regeneration to occur. The commonly loaded seeding cells are adipose-derived stem cells (ASCs), which are expected to induce stable and predictable adipose tissue formation. However, defects in stem cell enrichment, such as donor-site sacrifice, limit their wide application. As a promising alternative approach, cell-free bioactive scaffolds recruit endogenous cells for adipogenesis. In biomaterials without cell seeds, the key to sufficient adipogenesis relies on the recruitment of endogenous host cells and continuous induction of cell homing to scaffolds. Regeneration, rather than repair, is the fundamental dominance of an optimal mature product. To induce in situ adipogenesis, many researchers have focused on the mechanical and biochemical properties of scaffolds. In addition, efforts to regulate an angiogenic and adipogenic microenvironment in cell-free settings involve integrating growth factors or extracellular matrix (ECM) proteins onto bioactive scaffolds. Despite the theoretical feasibility and encouraging results in animal models, few of the reported cell-free biomaterials have been tested in humans, and failures of decellularized adipose tissues in adipogenesis have also been reported. In these cases, the most likely reason was the lack of supporting vasculature. This review summarizes the current status of biomaterials without cell seeds. Related mechanisms and influencing factors of in situ adipogenesis in cell-free biomaterials, dilemma in the development of biomaterials, and future perspectives are also addressed.

Analysis of oncological safety of autologous fat grafting after immediate breast reconstruction

Background

Fat grafting is now a common procedure for breast reconstruction. Many clinical studies have reported its aesthetic efficacy and oncological safety, but some experimental studies raise about the recurrence risk because of its regenerating property. This study aims to investigate the possibility of cancer recurrence associated with fat grafting.

Methods

In this retrospective cohort study, we analyzed a total of 339 patients who had undergone immediate reconstructive surgery after nipple-sparing mastectomy (NSM) or skin-sparing mastectomy (SSM) in our institution between February 28, 2009 and March 23, 2019. Patients who had undergone breast conserving surgery, radical mastectomy, or delayed reconstruction were excluded. We used univariate and multivariate Cox proportional hazards regression models to evaluate the association between fat grafting and cancer recurrence.

Results

Among the 339 patients during a median follow-up of 52 months, 27 patients (8.0%) were confirmed to have recurrent cancer. Of 67 patients who had undergone fat grafting, 10 patients were confirmed to have cancer recurrence. In multivariate analyses, fat grafting [hazard ratio (HR), 2.52; 95% CI, 1.005-6.317; P=0.0488] was independently associated with cancer recurrence.

Conclusions

In population of breast cancer patient who underwent immediate reconstruction in our institution, fat grafting showed significant higher risk of cancer recurrence. Although these results are at odds with many existing studies, it suggests that more careful follow-up may be necessary for patients who had undergone fat grafting after reconstructive surgery.

Aesthetic and therapeutic outcome of fat grafting for localized Scleroderma treatment: From basic study to clinical application

BACKGROUND

Localized scleroderma (LoS) is a rare autoimmune disease characterized by skin fibrosis and subcutaneous tissue atrophy, resulting in aesthetic impairment on patients. Fat grafting has been used to treat LoS patients, achieving aesthetic and therapeutic improvement.

AIMS

This article summarized the epidemiology and pathophysiology of LoS and the current progress and thorny questions of basic and clinical research on fat grafting treating LoS.

METHODS

The literature of the last 20 years concerning fat grafting of treating LoS was reviewed.

RESULTS

Fat grafting has been proved to produce aesthetic and therapeutic outcomes on LoS patients, including the improvement of soft tissue atrophy, skin fibrosis and pigmentation. Due to the inflammatory microenvironment of scleroderma, however, fat grafting still faces many difficulties, such as low fat retention. Novel fat grafting methods in order to supplement the deficiency of adipose-derived stem cells and improve fat retention in LoS groups have been proposed whose effectiveness and feasibility is still needed further study.

CONCLUSION

Currently, fat grafting has been regarded as an effective treatment with a combination of aesthetic and therapeutic outcomes on LoS patients.

Adipose tissue-derived stem cells in breast reconstruction: a brief review on biology and translation

Recent developments in adipose-derived stromal/stem cell (ADSC) biology provide new hopes for tissue engineering and regeneration medicine. Due to their pluripotent activity, paracrine activity, and immunomodulatory function, ADSCs have been widely administrated and exhibited significant therapeutic effects in the treatment for autoimmune disorders, neurodegenerative diseases, and ischemic conditions both in animals and human clinical trials. Cell-assisted lipotransfer (CAL) based on ADSCs has emerged as a promising cell therapy technology and significantly improved the fat graft retention. Initially applied for cosmetic breast and facial enhancement, CAL has found a potential use for breast reconstruction in breast cancer patients. However, more challenges emerge related to CAL including lack of a standardized surgical procedure, the controversy in the effectiveness of CAL, and the potential oncogenic risk of ADSCs in cancer patients. In this review, we summarized the latest research and intended to give an outline involving the biological characteristics of ADSCs as well as the preclinical and clinical application of ADSCs.

Adipose-Derived Mesenchymal Stromal Cells in Regenerative Medicine: State of Play, Current Clinical Trials, and Future Prospects

Significance: Wound healing is a complex process involving pain and inflammation, where innervation plays a central role. Managing wound healing and pain remains an important issue, especially in pathologies such as excessive scarring (often leading to fibrosis) or deficient healing, leading to chronic wounds. Recent Advances: Advances in therapies using mesenchymal stromal cells offer new insights for treating indications that previously lacked options. Adipose-derived mesenchymal stromal cells (AD-MSCs) are now being used to a much greater extent in clinical trials for regenerative medicine. However, to be really valid, these randomized trials must imperatively follow strict guidelines such as consolidated standards of reporting trials (CONSORT) statement. Indeed, AD-MSCs, because of their paracrine activities and multipotency, have potential to cure degenerative and/or inflammatory diseases. Combined with their relatively easy access (from adipose tissue) and proliferation capacity, AD-MSCs represent an excellent candidate for allogeneic treatments. Critical Issues: The success of AD-MSC therapy may depend on the robustness of the biological functions of AD-MSCs, which requires controlling source heterogeneity and production processes, and development of biomarkers that predict desired responses. Several studies have investigated the effect of AD-MSCs on innervation, wound repair, or pain management separately, but systematic evaluation of how those effects could be combined is lacking. Future Directions: Future studies that explore how AD-MSC therapy can be used to treat difficult-to-heal wounds, underlining the need to thoroughly characterize the cells used, and standardization of preparation processes are needed. Finally, how this a priori easy-to-use cell therapy treatment fits into clinical management of pain, improvement of tissue healing, and patient quality of life, all need to be explored.

Expanding Clinical Indications of Mechanically Isolated Stromal Vascular Fraction: A Systematic Review

BACKGROUND

Mechanically isolated stromal vascular fraction (tSVF, tissue SVF) is a potent regenerative solution, increasingly used as a therapeutic modality for a variety of pathologies. With recent evidence conclusively favoring mechanical isolation over enzymatic alternatives, the therapeutic share and indications of tSVF are expected to grow even further.

OBJECTIVES

The aim of this study was to provide a systematic review of all studies reporting on the use of tSVF.

METHODS

A systematic search was undertaken of the Embase, PubMed, Web of Science, and Cochrane Central Register of Controlled Trials databases. Outcome measures included clinical indications, such as recipient area, adverse events, clinical results recipient area, method of application, follow-up duration and evaluation methods.

RESULTS

Of the total of 4505 articles identified, 186 full-texts were screened. Thirty-four studies, reporting on 1443 patients were included. tSVF-based therapy was observed for 10 different pathologies, including aged skin (8 studies), scars (5), wounds (6), osteoarthritis (6), tendinopathy (2), temporomandibular joint disorders (1), androgenic alopecia (1), perianal fistula (3), migraine (1), and vocal fold scarring (1). Across all studies, tSVF-based therapy resulted in favorable clinical results. Overall, 50 (3.43%) minor and one (0.07%) major adverse events were observed, mainly related to the liposuction procedure.

CONCLUSIONS

tSVF offers a safe, easy and legal treatment modality for a range of indications. Future research is indicated to identify the optimal isolation protocol, dose and timing. In addition, basic research remains crucial to identify the mechanism of action of SVF within different pathologies.

LEVEL OF EVIDENCE: 4

Cancer-associated adipocytes: emerging supporters in breast cancer

Breast cancer (BC) is a malignant breast tumor confronted with high invasion, metastasis and recurrence rate, and adipocytes are the largest components in breast tissue. The aberrant adipocytes, especially the BC-neighbored cancer-associated adipocytes (CAAs), are found in the invasive front of BC. CAAs present a vicious phenotype compared with mature mammary adipocytes and mediate the crosstalk network between adipocytes and BC cells. By releasing multiple adipokines such as leptin, adiponectin, interleukin (IL)-6, chemokine ligand 2 (CCL2) and chemokine ligand 5 (CCL5), CAAs play essential roles in favor of proliferation, angiogenesis, dissemination, invasion and metastasis of BC. This article reviews the recent existing CAAs studies on the functions and mechanisms of adipocytes in the development of BC, including adipokine regulating, metabolic reprogramming, extracellular matrix (ECM) remodeling, microRNAs (miRNAs) and immune cell adjusting. Besides, adipocyte secretome and cellular interactions are implicated in the intervention to BC therapy and autologous fat grafting of breast reconstruction. Therefore, the potential functions and mechanisms of CAAs are very important for unveiling BC oncogenesis and progress. Deciphering the complex network between CAAs and BC is critical for designing therapeutic strategies and achieving the maximum therapeutic effects of BC.

[Long-term evaluation after autologous fat transplantation for breast augmentation]

Background The transplantation of autologous fat is an increasingly common but not standardized procedure in aesthetic and reconstructive surgery. Until now only studies about the short-term results after transplantation with autologous fat have been published. In this publication we present our results of a long-term study after fat transplantation.Patients/Material and Methods 14 patients underwent an MRI investigation which was done before and 5-9 years (mean 6 years) years after aesthetic breast lipofilling according to BEAULI-protocol. The difference in volume was calculated with the open source software OsiriX. Two groups were analyzed separately to calculate the influence of body weight changes in final volume gain. In the first group patients with a stable BMI (increase of less than 1 kg/m²⁾ were included. The second group includes patients with a BMI gain exceeding more than 1 kg/m². The mean increase in BMI was 1,6 kg/m² (minimum 0 - maximum 3,9). None of the patients lost weight.Results Depending on the desired amount of breast augmentation the patients underwent between one to four operations. An average of 176 ml fat was transplanted per breast and surgery. In the first group a mean volume survival of 74 % (IQR 58 % - 92 %) was observed. In the second group an increase of 135 % (IQR 105 % - 318 %) of the volume of transplanted fat was observed. After an intermediate weight loss one of the patients regained her initial weight.Conclusion In this study the transplantation of autologous fat renders good long-term results. There is a significant correlation between change of weight and fat transplant volume survival over the years. This also explains the very high increase in breast volume in some patients. Autologous fat transplantation seems to be a safe and efficient method for breast augmentation. For further statements studies with larger number of cases are necessary.

Ex vivo-expanded autologous adipose tissue-derived stromal cells ensure enhanced fat graft retention in breast augmentation: A randomized controlled clinical trial

Autologous fat grafting and implant surgery are used for volume restoration in plastic surgery. With the aim of producing a treatment superior to current solutions, we report a randomized, controlled, data assessor‐blinded clinical trial comparing fat grafts enriched with ex vivo‐expanded autologous adipose‐derived stromal cells (ASCs) to nonenriched fat grafts in breast augmentation. The intervention group received ASC‐enriched fat grafts (≥20 × 10⁶ viable ex vivo‐expanded ASCs per milliliter fat), and the control group received conventional nonenriched fat grafts. Volume retention was measured by magnetic resonance imaging, and clinical photographs were taken simultaneously for outcome evaluation. ASC‐enriched fat grafts had significantly higher retention rates (mean = 80.2%) compared with conventional fat grafts (mean = 45.1%). Clinical photos showed statistically significant superior results in the intervention group, assessed by independent clinical experts. These results improve the prospects for using culture‐expanded ASCs in both reconstructive and cosmetic volume restoration and make the procedure an attractive alternative to conventional fat grafting and implants. This study is registered at www.ClinicalTrials.gov, number H‐16046960.

Knockout of E2F1 Inhibits Adipose Stem Cell Proliferation and Differentiation in Fat Transplantation by Repressing Peroxisome Proliferator-Activated Receptor Gamma Expression

Adipose-derived stem cells (ADSCs) possess pluripotent differentiation potential and self-replication ability, which is highly significant in the field of tissue engineering. Cell-assisted lipotransfer (CAL) with ADSCs benefits fat survival. In this study, we focus on the effect of transcription factor E2F1 during CAL. The wild-type (WT) ADSCs were mixed with WT adipocytes, and the E2F1^-/- ADSCs were mixed with E2F1^-/- adipocytes. Then 2 cell mixtures were inoculated on the back 2 sides of E2F1^-/- mice, respectively denoted as the WT group (WT ADSCs + WT adipose cells) and E2F1^-/- group (E2F1^-/- ADSCs + E2F1^-/- adipose cells). At week 4, the fat graft was heavier in the WT group, with less necrotic area, more survival of mature adipocytes, and more proliferating ADSCs, compared with the E2F1^-/- group. More capillaries were transformed from ADSCs in the WT group than in the E2F1^-/- group. The in vitro protein levels of peroxisome proliferator-activated receptor gamma (PPAR-γ) were higher in WT ADSCs than in E2F1^-/- ADSCs. Therefore, these findings suggest that knockout of E2F1 could affect ADSCs to inhibit the survival of fat grafts by downregulating PPAR-γ expression.

Extracellular vesicles derived from human adipose-derived stem cells promote the exogenous angiogenesis of fat grafts via the let-7/AGO1/VEGF signalling pathway

Extracellular vesicles (EVs) derived from human adipose-derived stem cells (hADSCs) possess the proangiogenic potential for ischaemic diseases. Thus, our study aimed to evaluate the therapeutic effects of hADSC-EVs on fat grafting and explore the mechanism of hADSC-EVs promoting angiogenesis. The EVs released by hADSCs incubated under normal or hypoxic conditions were employed to supplement fat grafting in a nude mouse model. The proliferation, migration, tube formation and vascular endothelial growth factor (VEGF) secretion of vascular endothelial cells co-cultured with two kinds of hADSC-EVs were analysed. MicroRNA sequencing was performed to reveal the species and content of microRNAs in hADSC-EVs, the key microRNAs were blocked, and their effect in promoting angiogenesis was detected via above protocols as a reverse proof. The results demonstrate that hADSC-EVs could improve the survival of fat grafts by promoting exogenous angiogenesis and enhance the proliferation, migration, tube formation and VEGF secretion of vascular endothelial cells. In addition, the pro-angiogenic effect of hADSC-EVs in vivo and vitro could be enhanced by hypoxic pre-treatment. We found that the let-7 family, a kind of hypoxic-related microRNA, is enriched in hypoxic hADSC-EVs that contribute to angiogenesis via the let-7/argonaute 1 (AGO1)/VEGF signalling pathway.

Introduction of ligated vessels promote the retention and regeneration of free fat: constructing a fat flap in tissue engineering chamber

Background: Breast reconstruction with fat grafting has an unstable retention rate due to insufficient revascularization. Tissue Engineering Chamber (TEC) model can promote tissue regeneration in the chamber by introducing ligated vessels around the tissue. We introduced ligated vessels with free fat graft to investigate the retention rate and revascularization of grafted fat that in TEC model.

Methods: SD rats (n=24) was divided into 3 groups randomly. Group A: Standard TEC model was constructed; Group B: the epigastric vessel bundles were dissected from the fat flap and ligated, fat flap was cut into granules and planted into the chamber; Group C: Free fat was planted in the chamber. At week 6, samples in the chamber were harvested.

Results: Significant volume increase was observed in group A and B, while the volume decreased in group C (P<0.05). Regeneration morphology could be found according to the histological observation in A and B. Micro CT results showed the ligated vessels into grafted fat sprouting robustly, coordinated with volume changes.

Conclusion: Fat grafts in TEC model could not only survive but also regenerate. The combination of fat graft and TEC could fabricate a vascularized fat flap, which was a promising method in breast reconstruction.

Abbreviations: VOI: Volumes of Interest; TEC: Tissue Engineering Chamber; CAL: Cell Assisted Lipotransfer.

An Overview of Principles and New Techniques for Facial Fat Grafting

Facial fat grafting is a small-volume procedure and is primarily performed for facial rejuvenation, contouring, or regenerative surgery. The unsatisfying retention rate after fat grafting, however, led to unpredictable outcomes, subsequent multiple procedures, and even some complications. A variety of methods have been proposed to enhance the results of facial fat grafting, including several established surgical principles and many possible new techniques. Adding stem cells, fat preparations, and platelet concentrates may improve the survival after fat grafting but randomized controlled clinical studies are needed to determine their safety and efficacy as well as clinical indications for each technique.

Principles and Applications of Fat Grafting in Plastic Surgery

Autologous fat transplantation has become increasingly popular in recent years. Its biocompatable properties and availability made it a widely used treatment modality for soft tissue augmentation and volume replacement in both reconstructive and aesthetic plastic surgery. Multiple protocols and clinical applications have been described in the literature, with wide variations in the harvesting, processing, and injection techniques. In this review, the authors will discuss the basic principles and clinical applications of fat grafting in plastic and reconstructive surgery. The article will then conclude with a discussion of fat grafting limitations as well as potential future applications, giving the reader a well-rounded understanding of autologous fat transfer.

Optimal Use Ratio of the Stromal Vascular Fraction (SVF): An Animal Experiment Based on Micro-CT Dynamic Detection After Large-Volume Fat Grafting

BACKGROUND

The addition of the stromal vascular fraction (SVF) can enhance the postoperative survival rate of fat. However, a universal SVF application method is currently unavailable. Therefore, a simple and convenient guideline for SVF addition is needed for its clinical application.

OBJECTIVES

The authors sought to evaluate whether SVF can improve fat survival after large-volume fat grafting and to find a simple and convenient standard for the clinical use of SVF.

METHODS

Patient fat samples were obtained after liposuction for SVF preparation and grafting. Four types of grafts were prepared with different SVF ratios: 0:1, 1:1, 2:1, and 4:1 SVF:fat. After intensive mixing, fat grafts (5 mL) were randomly injected into both sides of the backs of athymic rats (n = 15). At 24 hours and 1, 3, 6, and 9 months after the operation, microcomputed tomography scanning was performed to calculate the fat survival rate.

RESULTS

Nine months after the operation, the survival rates of fat in the 4 groups were 8.89 ± 1.62% (0:1), 18.26 ± 3.85% (1:1), 8.83 ± 1.46% (2:1), and 7.96 ± 1.31% (4:1). The 1:1 group exhibited the greatest survival rate (P < 0.01), and the adipose tissue histological patterns and blood vessel quality were enhanced compared with those in the other groups.

CONCLUSIONS

An appropriate SVF ratio can increase the fat survival rate after large-volume fat grafting, but no linear relationship exists between the SVF ratio and fat survival. The optimal SVF:fat ratio for grafting is 1:1.

Facial aesthetic fat graft retention rates after filtration, centrifugation, or sedimentation processing techniques measured using three-dimensional surface imaging devices

OBJECTIVE

How to increase the long-term retention rate of autologous fat grafting has been widely discussed. This study aimed to evaluate long-term fat graft retention rates for the most widely used fat processing methods in the area of facial esthetic surgery, including centrifugation, filtration, and sedimentation, using three-dimensional (3D) imaging.

DATA SOURCES

PubMed, Embase, Wiley/Cochrane Library, and Web of Science databases were comprehensively searched from inception to July 2018 according to the guidelines of the American Society of Plastic Surgeons Fat Graft Task Force Assessment Methodology.

STUDY SELECTION

Articles were screened using predetermined inclusion and exclusion criteria. Data collected included patient characteristics, follow-up devices, fat grafting techniques, and clinical outcomes. Patient cohorts were pooled, and fat graft retention rates were calculated. Complications were summarized according to different clinical characteristics.

RESULTS

Of 77 articles, 10 clinical studies met the inclusion criteria and reported quantified measurement outcomes with 3D imaging which provide precise volumetric data with approximately 2% standard deviation compared to real volumes. Data of 515 patients were included. Fat grafting retention varied from 21% to 82%. We found filtration and centrifugation techniques could result in better retention outcomes. However, retention varied within each processing technique, with no significant difference among the 3 techniques. Twenty-two complications were reported among 515 patients, including donor-site hematoma (1 case), mild post-operative erythema (2 cases), mild volumetric asymmetries (2 cases), chronic edema (2 cases), overcorrection (2 cases), skin irregularity (6 cases), and headache or dysesthesia (7 cases).

CONCLUSIONS

Filtration and centrifugation techniques may result in better fat grafting retention outcomes than gravity sedimentation; however, more accurate statistical evidence is needed. Controversies continue to exist with respect to the performance of the different fat-processing techniques in fat graft retention.

The Disturbed Function of Neutrophils at the Early Stage of Fat Grafting Impairs Long-Term Fat Graft Retention

BACKGROUND

Fat grafting is a popular soft-tissue filler method; however, the mechanism of its survival and regeneration is still not fully understood. Neutrophils are the frontier inflammatory cells and closely associated with tissue regeneration. To understand the role of neutrophils in fat graft retention, we adopted neutrophil depletion and up-regulation models.

METHODS

Mouse inguinal fat (approximately 200 mg) was transferred autologously. The anti-mouse Ly6G antibody and lipopolysaccharides were used in the mouse fat grafting model for neutrophil depletion or activation, respectively. We examined the blood and graft stromal vascular fraction by fluorescence-activated cell sorting in manipulation/control groups. Graft weight, vascularization, and secreted factors were also compared.

RESULTS

There was a significant reduction/increase of neutrophil counts in the circulation and the transferred fat before day 7 with Ly6G antibody/lipopolysaccharides treatment. Early depletion of neutrophils resulted in incompetent angiogenesis and eventually a poor retention rate (27 ± 8 percent) compared with control (51 ± 10 percent; p < 0.05), whereas up-regulated neutrophils increased the inflammation and reactive oxygen species level, leading to tissue damage and poor retention rate (20 ± 9 percent) compared with control (51 ± 10 percent; p < 0.05). Enhanced macrophage infiltration could be found in both neutrophil depletion and up-regulation groups after week 4.

CONCLUSIONS

Undisturbed neutrophil function is the key to initiating downstream responses of macrophage infiltration, stimulating vessel formation, and regulating inflammation level; thus, it exerts a great impact on the long-term retention rate. Disturbed neutrophil function, either enhanced or weakened, can lead to impaired fat graft retention.