The effect of interleukin-8 on the viability of injected adipose tissue in nude mice

Inhibition of Adipocyte Necroptosis Alleviates Fat Necrosis and Fibrosis After Grafting in a Murine Model

BACKGROUND

Because of the delicate structure of the adipose tissue, fat necrosis accounts for 43.7% of all complications after autologous fat grafting; however, its regulation remains unclear.

OBJECTIVES

The purpose of this study was to examine the role of necroptosis in fat graft remodeling after grafting.

METHODS

Clinical fat graft necrosis samples were collected, and the expression levels of the necroptosis marker phosphorylated(p)-MLKL were analyzed. Transcriptome analysis was performed on fat grafts before and 1 week after transplantation in C57BL/6 mouse fat grafting models. Additionally, the in vivo effects of RIPK1 inhibitor Nec-1s or RIPK3 inhibitor GSK'872 on the fat grafting complications, including fat necrosis and fibrosis, were investigated.

RESULTS

Necroptosis markers were observed and associated with higher occurrence of fibrosis in clinical fat graft necrosis samples compared to normal fat tissue. Amplification and RNA-Seq were conducted on RNA isolated from fat grafts before and after grafting. MLKL, RIPK1, and RIPK3's expression levels were significantly upregulated in comparison to controls. Higher expression levels of necroptotic RNAs were associated with higher levels of DAMPs, including Cxcl2, HMGB1, S100a8, S100a9, Nlrp3, and IL33, and activated proinflammatory signaling pathways, including the TNF, NF-kappa B, and chemokine signaling pathways. Necroptotic inhibitor Nec-1s and GSK'872 robustly suppressed the p-MLKL expression level and significantly inhibited necroptotic cell death, especially in adipocytes. Moreover, administration of Nec-1s and GSK'872 significantly alleviated fat necrosis and subsequent fibrosis in fat grafts.

CONCLUSIONS

Collectively, our study findings highlight the potential therapeutic applications of necroptosis inhibitors in preventing fat necrosis and fibrosis after grafting.

LEVEL OF EVIDENCE: 4

Lymphatic Vessel-Mediated Attenuation of Persistent Macrophage Infiltration Improves Fat Grafting Outcomes in Mice Models

BACKGROUND

Persistent macrophage infiltration may lead to adverse consequences, such as calcifications and nodules in fat grafts. Lymphatic vessels, which transport inflammatory cells, are involved in regulating inflammatory responses. Less is known, however, about lymphatic vessels after fat grafting.

OBJECTIVES

The aim of this study was to explore the regulation of fat graft survival by lymphatic vessels.

METHODS

A common adipose graft model was constructed to assess the processes responsible for changes in the number of lymphatic vessels in grafts. Adipose tissue samples from C57/BL6 mice and green fluorescent protein-expressing mice were cross-grafted to determine the source of lymphatic vessels. The number of lymphatic vessels in the grafts was increased by treatment with vascular endothelial growth factor C, and the effects of this increase on fat grafting were evaluated.

RESULTS

The number of lymphatic vessels was greater in postgrafted fat than in inguinal fat before transplantation, with lymphatic vessels in these grafts gradually transitioning from donor to recipient sources. Lymphatic vessels grew more slowly than blood vessels during early stages of grafting; during later stages, however, the number of blood vessels declined markedly, with more lymphatic vessels than blood vessels being observed 60 days after grafting. Vascular endothelial growth factor C treatment increased graft lymphatics and distant volume retention, while reducing fibrosis and oil sacs. Lymphatic vessels acted as drainage channels for macrophages, with the degree of sustained macrophage infiltration decreasing with increases in the number of lymphatic vessels.

CONCLUSIONS

Increasing the number of lymphatic vessels is beneficial for fat graft survival, which may be related to a reduction in prolonged macrophage infiltration.

LEVEL OF EVIDENCE: 4

Glutathione supplementation improves fat graft survival by inhibiting ferroptosis via the SLC7A11/GPX4 axis

BACKGROUND

Autologous fat grafting is hampered by unpredictable graft survival, which is potentially regulated by ferroptosis. Glutathione (GSH), a powerful antioxidant used in tissue preservation, has ferroptosis-regulating activity; however, its effects on fat grafts are unclear. This study investigated the effects and mechanisms of GSH in fat graft survival.

METHODS

Human lipoaspirates were transplanted subcutaneously into the backs of normal saline-treated (control) or GSH-treated nude mice. Graft survival was evaluated by magnetic resonance imaging and histology. RNA sequencing was performed to identify differentially expressed genes and enriched pathways. GSH activity was evaluated in vitro using an oxygen and glucose deprivation (OGD) model of adipose-derived stem cells.

RESULTS

Compared with control group, GSH induced better outcomes, including superior graft retention, appearance, and histological structures. RNA sequencing suggested enhanced negative regulation of ferroptosis in the GSH-treated grafts, which showed reduced lipid peroxides, better mitochondrial ultrastructure, and SLC7A11/GPX4 axis activation. In vitro, OGD-induced ferroptosis was ameliorated by GSH, which restored cell proliferation, reduced oxidative stress, and upregulated ferroptosis defense factors.

CONCLUSIONS

Our study confirms that ferroptosis participates in regulating fat graft survival and that GSH exerts a protective effect by inhibiting ferroptosis. GSH-assisted lipotransfer is a promising therapeutic strategy for future clinical application.

Heating Pretreatment of the Recipient Site Enhances Survival of Transplanted Fat in a Mouse Model

BACKGROUND

Despite several studies about the preparation of the recipient site in fat grafting, optimizing techniques with clinical usefulness is still necessary. Through previous animal studies reporting that heat can increase tissue vascular endothelial growth factor and vascular permeability, the authors hypothesize that pretreatment heating of the recipient site will increase retention of grafted fat.

METHODS

Twenty 6-week-old female BALB/c mice had two pretreatment sites on their back, one for the experimental temperatures (44°C and 48°C) and the other for the control. A digitally controlled aluminum block was used to apply the contact thermal damage. Human fat (0.5 mL) was grafted on each site and harvested on days 7, 14, and 49. The percentage volume and weight, histologic changes, and peroxisome proliferator-activated receptor gamma expression, a key regulator of adipogenesis, were measured by the water displacement method, light microscopy, and quantitative real-time polymerase chain reaction, respectively.

RESULTS

The harvested percentage volumes were 74.0% ± 3.4%, 82.5% ± 5.0%, and 67.5% ± 9.6% for the control, 44°C-pretreatment, and 48°C-pretreatment groups, respectively. The percentage volume and weight of the 44°C-pretreatment group was higher than the other groups ( P < 0.05). The 44°C-pretreatment group exhibited significantly higher integrity with fewer cysts and vacuoles than the other groups. Both heating pretreatment groups showed markedly higher rates of vascularity than the control group ( P < 0.017), and also increased the expression of peroxisome proliferator-activated receptor gamma over two-fold.

CONCLUSION

Heating preconditioning of the recipient site during fat grafting can increase the retention volume and improve the integrity, which is partly explained by increased adipogenesis in a short-term mouse model.

CLINICAL RELEVANCE STATEMENT

Tanning could be an alternative pretreatment for fat grafting.

Use of platelet-rich fibrin in fat grafts during facial lipostructure

BACKGROUND

This review was designed to discuss the safety and efficacy of using platelet-rich fibrin (PRF) in fat grafts during facial lipostructure.

METHODS

From January 2018 to December 2021, 650 fat grafts for facial lipostructure were performed in the authors' department. According to their wishes, we divided the patients into two groups: 498 patients were treated with autologous fat injection (control group), and 152 patients were treated with autologous fat injection combined with PRF. All of the patients were monitored for at least six months. The effects were evaluated via physician assessment and patient satisfaction rates, and the incidences of complications were compared.

RESULTS

All the cases had a degree of improvement after treatment. The patient satisfaction rate was 55.3% in the PRF group and 43.4% in the control group. In all, 68.4% of the patients in the PRF group and 58.2% in the control group indicated that one-stage surgery was sufficient to achieve the desired effect. According to the evaluation conducted by the plastic surgeon, 59.2% of patients in the PRF group and 47.0% in the control group achieved a perfect effect. A total of 76.3% of patients in the PRF group and 63.9% in the control group reported that one surgery achieved satisfactory results. The difference between the PRF and control groups was statistically significant.

CONCLUSION

Using an autologous fat graft during facial lipostructure is beneficial and safe when combined with PRF. The combination may enhance the effect and satisfaction rate. Further research and prospective clinical studies are needed to understand the role of PRF in fat grafting.

Effects of miR126 Expressing Adipose-Derived Stem Cells on Fat Graft Survival and Angiogenesis

BACKGROUND

Fat transplantation supported by supplementation with ASCs has become a reliable procedure for treating soft tissue defects. However, the unpredictable survival rates for grafted fat remains a challenge with post-transplantation ischemia causing tissue loss. MiR126, which regulates VEGF signaling, is an endothelial cell-specific miRNA known to play an essential role in angiogenesis. We hypothesized that increased miR126 expression in grafted ASCs may promote fat survival within an autologous fat transfer model.

METHODS

Rat adipose-derived stem cells were isolated, expanded ex vivo for three passages and then transduced with miR126. We used PCR to verify lentiviral transduction and ELISA to confirm VEGF expression. We then mixed autologous fat tissues from our rat model with transduced ASCs, augmented with a nonsense control or miR126 expression vector. These mixtures were used in the fat grafting procedure, completed via subcutaneous injection at three paravertebral points in each rat. Fat grafts were then harvested on days 4, 7, 14, and 28 post-transplant and evaluated for survival, neovascularization, and protein expression via western blot.

RESULTS

VEGF expression levels in ASCs, Con-ASCs, and miR126-ASCs were not significantly different. However, miR126-ASCs experienced significantly improved survival on days 7, 14, and 28 when compared with the other groups. These ASCs also presented with the greatest capillary density on days 7, 14, and 28 post-transplantation as well as increased p-ERK and p-AKT expression when compared to the other groups.

CONCLUSION

This data suggests that miR126 augmentation of ASCs may help to enhance the survival and angiogenic capacity of transplanted fat tissues, and that this augmentation was not dependent on VEGF but rather the activation of the ERK/AKT 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 .

Platelet-Rich Fibrin in Fat Grafts for Facial Lipofilling: A Randomized, Controlled Split-Face Clinical Trial

Objective

Previous studies have reported that platelet-rich fibrin (PRF) may enhance the efficacy of fat grafts in facial lipofilling. However, these studies either lacked objective data or were not randomized, controlled trials. Thus, we aimed to objectively evaluate the efficacy of PRF in facial lipofilling.

Methods

A controlled, split-face, randomized trial (January 2018 to May 2019) based on 18 patients who underwent fat grafts for bilateral temple lipofilling was performed. Each patient received a combination of an autologous fat graft and PRF on one side and a fat graft combined with an equal volume of saline on the other side. The effects of PRF were evaluated by comparing the remaining bilateral fat graft volumes through a digital three-dimensional reconstruction technique. Improvements in the appearance and recovery time of each temple were assessed by both a surgeon and patients who were blinded to the treatment assignment. Complications were also recorded.

Results

Bilateral temple lipofilling showed no evidence of fat embolism, vascular/nerve injury, infection, massive edema, or prolonged bruising. Three-dimensional reconstruction data and the assessments from both the surgeon and patients revealed no significant differences in fat graft retention volume between the PRF-positive and PRF-negative lipofilling groups. However, recovery time in the PRF-positive lipofilling sites was significantly shortened compared with that of the PRF-negative lipofilling sites.

Conclusion

Facial filling with autologous fat grafts is effective and safe. Our results show that PRF does not markedly improve fat graft volume retention in the temple but significantly reduces postoperative recovery time.

Trial Registration Number

ChiCTR2100053663.

Washing Lipoaspirate Improves Fat Graft Survival in Nude Mice

BACKGROUND

The optimal fat processing technique of fat grafting has not been determined. We have proved the importance of washing lipoaspirate to remove blood, but the necessity of washing when there is no obvious bleeding during liposuction is not clear.

OBJECTIVES

The purpose of this study is to further investigate the effect of washing on fat graft survival and the underlying mechanisms, from the perspective of inflammation, oxidative stress and apoptosis.

METHODS

To exclude the influence of blood, de-erythrocyte infranatant (dEI) isolated from lipoaspirate was obtained. Purified fat processed by cotton pad filtration mixed with dEIs after sedimentation (sedimentation group), washing (washing group) or phosphate buffer solution (control group) was transplanted to nude mice subcutaneously. Samples were harvested at 1 day and 1, 3, 8 weeks after transplantation. Volume and weight retention, histologic examination, immunostaining of perilipin-1, CD31, CD45 and Ly6g, mRNA expression of PPAR-γ, C/EBPα, VEGF, bFGF, IL-6, IL10, TNF-α, TGF-β, Bax and Bcl-2, and protein contents of 8-iso-PGF2α, IL-6, IL10, TNF-α and TGF-β were all compared among groups.

RESULTS

After transplantation, volume and weight retention, histologic scores, viable adipocytes and vascularization were all improved in the washing group, with increased expression of adipogenic and angiogenic genes. Compared with the sedimentation group, the washing group had milder inflammation, lower levels of oxidative stress and apoptosis.

CONCLUSIONS

Washing lipoaspirate to eliminate mixed components can improve fat graft survival and promote adipogenesis and angiogenesis, possibly by relieving inflammation, reducing oxidative stress injury and inhibiting apoptosis.

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 47 these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Human umbilical cord mesenchymal stem cell promotes angiogenesis via integrin β1/ERK1/2/HIF-1α/VEGF-A signaling pathway for off-the-shelf breast tissue engineering

Background

Mesenchymal stem cells (MSC)-based tissue engineered breast represent the visible future for breast reconstruction after mastectomy. However, autologous MSCs might not be appropriate for the large graft construction due to cell senescence during excessive cell expansion, thus hindering its further off-the-shelf application. The human umbilical cord mesenchymal stem cells (hUCMSCs) have been found to induce low immune response and can be easily stored, making them ideal for off-the-shelf tissue engineering application. Here, we explored the feasibility of using umbilical cord mesenchymal stem cells as tissue-engineered breast seed cells.

Methods

The allogenic hUCMSCs were injected into transplanted fat tissue with or without breast scaffolds as an alternative for breast tissue engineering in vivo, and its potential mechanism of angiogenesis in vitro was explored.

Results

Transplantation of hUCMSCs promoted proliferation, migration, and angiogenesis of human umbilical vein endothelial cells (HUVECs) through paracrine mechanism by activating the integrin β1/ERK1/2/HIF-1α/VEGF-A signaling pathway. Histological examination of grafted fat revealed that the group which received hUCMSCs transplantation had more fat tissue [(93.60 ± 2.40) %] and fewer MAC2⁺CD206⁻ M1 macrophages [(0.50 ± 0.47) cells/field] compared to the control group [fat tissue (45.42 ± 5.96) and macrophage cells/field (5.00 ± 2.23)]. Moreover, the hUCMSCs- labeled with a tracing dye differentiated into adipocytes and vascular endothelial cells in the adipose tissue. When applied to the tissue-engineered breast with a scaffold, the group treated with hUCMSCs had more adipose tissues and CD31⁺ cells than the control group.

Conclusions

These results demonstrate that allogeneic hUCMSCs promote the regeneration of adipose tissue and can be used to construct a tissue engineered breast.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02770-x.

Cameroonian Spice Extracts Modulate Molecular Mechanisms Relevant to Cardiometabolic Diseases in SW 872 Human Liposarcoma Cells

The molecular pathophysiology of cardiometabolic diseases is known to be influenced by dysfunctional ectopic adipose tissue. In addition to lifestyle improvements, these conditions may be managed by novel nutraceutical products. This study evaluatedthe effects of 11 Cameroonian medicinal spice extracts on triglyceride accumulation, glucose uptake, reactive oxygen species (ROS) production and interleukin secretion in SW 872 human adipocytes after differentiation with 100 µM oleic acid. Triglyceride content was significantly reduced by all spice extracts. Glucose uptake was significantly increased by Tetrapleura tetraptera, Aframomum melegueta and Zanthoxylum leprieurii. Moreover, Xylopia parviflora, Echinops giganteus and Dichrostachys glomerata significantly reduced the production of ROS. Concerning pro-inflammatory cytokine secretion, we observed that Tetrapleura tetraptera, Echinops giganteus, Dichrostachys glomerata and Aframomum melegueta reduced IL-6 secretion. In addition, Xylopia parviflora, Monodora myristica, Zanthoxylum leprieurii, and Xylopia aethiopica reduced IL-8 secretion, while Dichrostachys glomerata and Aframomum citratum increased it. These findings highlight some interesting properties of these Cameroonian spice extracts in the modulation of cellular parameters relevant to cardiometabolic diseases, which may be further exploited, aiming to develop novel treatment options for these conditions based on nutraceutical products.

Salvianolic acid-B improves fat graft survival by promoting proliferation and adipogenesis

Background

Our previous study proved that Salvia miltiorrhiza could enhance fat graft survival by promoting adipogenesis. However, the effect of salvianolic acid B (Sal-B), the most abundant and bioactive water-soluble compound in Salvia miltiorrhiza, on fat graft survival has not yet been investigated.

Objective

This study aims to investigate whether salvianolic acid B could improve fat graft survival and promote preadipocyte differentiation. The underlying mechanism has also been studied.

Methods

In vivo, 0.2 ml of Coleman fat was transplanted into nude mice with salvianolic acid B. The grafts were evaluated by HE and IF at 2 and 4 weeks posttransplantation and by micro-CT at 4 weeks posttransplantation. In vitro, the adipogenesis and proliferative activities of salvianolic acid B were analyzed in cultured human adipose-derived stem cells (h-ADSCs) and 3T3-L1 cells to detect the mechanism by which salvianolic acid B affects graft survival.

Results

In vivo, the weights and volumes of the fat grafts in the Sal-B-treated groups were significantly higher than those of the fat grafts in the control group. In addition, higher fat integrity and more viable adipocytes were observed in the Sal-B-treated groups. In vitro, salvianolic acid B showed the ability to promote 3T3-L1 and h-ADSC proliferation and adipogenesis.

Conclusions

Our in vitro experiments demonstrated that salvianolic acid B can promote the proliferation of adipose stem cells and enhance the differentiation of adipose stem cells. Simultaneously, in vivo experiments showed that salvianolic acid B can improve the survival rate of fat transplantation. Therefore, our research shed light on the potential therapeutic usage of salvianolic acid B in improving the survival rate of fat transplantation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02575-4.

The significance of erythropoietin and insulin administration on survival of fat tissue after autologous fat transplantation in Wistar rats. An experimental study

Autologous fat transfer is widely used by plastic surgeons for aesthetic and reconstructive purpose, but it has a great disadvantage because of its high variability rate of resorption. Numerous studies have examined the use of different agents to increase the viability of fat grafts. The results were discouraging because the use of a single angiogenic factor to stimulate fat graft angiogenesis may be inappropriate. We proposed to use two pharmacological factors, erythropoietin (EPO) and insulin (INS), in order to decrease the resorption rate, to improve graft vascularization, and to reduce the number of complications. Twenty-four Wistar male rats were randomly divided in four groups (I–IV) of six animals each. The rats belonging to control group were given autologous transfer of simple fat. In group II, the graft was improved with EPO, in group III with INS, and in group IV both pharmacological agents were administered. Histological evaluation of the grafts at two months after injection demonstrated adipocyte survival in all four groups. The volume of the graft has progressively decreased in all groups and the difference in graft volume at one and two months after transplantation was not significant. The highest maintenance of fat graft volume (95%) at two months was observed in group IV, followed by group II and group III. Necrotic cystic changes and increased fibrosis were most extensive in the control group. The combination of INS with EPO may have a synergistic and additive effect. Efficient administration and dose optimization of these growth factors are important things to consider in the future.

Platelet-rich fibrin: An effective chronic wound healing accelerator

BACKGROUND

Platelets are cells that play a central role in wound healing, and they are the main source of the growth factor complex that plays the main role in natural wound healing. It is aimed to present the beneficial effects of topical application of PRF on chronic ulcers that do not respond to standard wound care in cases of chronic ulcers that require a long treatment process and high costs.

MATERIALS AND METHODS

The study included 16 patients between the dates of January 2017 and September 2019. The study was approved by the local ethics board and planned retrospectively.

RESULTS

The mean number of PRF applications in the patients was 4.37 (range: 1-8), while the wounds of 10 patients were completely closed up to the mean number of applications, and at least 50% of the wounds of 4 patients were closed up to the mean number of applications.

DISCUSSION

Choukroun's platelet-rich fibrin may be considered as a 2nd-generation platelet concentration. Its preparation protocol is reported to be highly simple and low-cost.

CONCLUSION

PRF is a safe, practical, easy to use adjuvant treatment method which has a potential for closing chronic wounds.

Hydrogel from acellular porcine adipose tissue promotes survival of adipose tissue transplantation

Lipofilling is a popular technique for soft tissue augmentation, limited by unpredictable graft survival. This study aimed at exploring the effect of hydrogel from acellular porcine adipose tissue (HAPA) on angiogenesis and survival of adipose tissue used for lipofilling. The effect of HAPA on adipose-derived stem cells (ADSCs) proliferation, adipogenic differentiation, and vascular endothelial growth factor (VEGF) secretion were evaluated in hypoxia and normoxiain vitro. For thein vivostudy, adipose tissue with phosphate buffered saline, ADSCs, and HAPA (with or without ADSCs) were co-injected subcutaneously into nude mice. HAPA-ADSCs mixture (tissue engineering adipose tissue) was also grafted. Gross observation, volume measurement, and ultrasound observation were assessed. For histological assessment, hematoxylin and eosin, perilipin, cluster of differentiation 31 (CD31), Ki67, and transferase-mediated d-UTP nick end labelling (TUNEL) staining were performed. HAPA improved ADSCs proliferation, VEGF secretion, and adipogenic differentiation under normoxia and hypoxia conditionsin vitrostudy. For thein vivostudy, HAPA showed improved volume retention and angiogenesis, and reduced cell apoptosis when compared to ADSCs-assisted lipofilling and pure lipofilling. In conclusion, HAPA could maintain ADSCs viability and improve cell resistant to hypoxia and might be a promising biomaterial to assist lipofilling.

Cosmetic Fat Transplantation: A Review

AIM

To review current techniques used in fat grafting to optimise graft persistence and achieve optimal cosmetic outcomes.

BACKGROUND

Fat transplantation has been used extensively in the reconstruction and cosmetic industry for many years. However, there is significant adipocyte loss and reabsorption rates, leading to the loss of external cosmetic volume and the need for repeat procedures. Adipocyte loss can occur at all four stages of transplantation and this review discusses each of these methods with the aim being to optimise graft outcome.

RESULTS

Several new techniques have been discussed including liposuction techniques, fat processing, and assisted fat grafting which show an improvement in adipocyte survival, revasculisation and graft outcomes.

CONCLUSION

There have been many improvements in fat grafting and the implementation of these will optimise surgical outcomes but there are still strategies to improve further. However, there is still a lack of standardised techniques and training. More research is needed in the areas of fat processing and the use of additives to the fat graft. More clinical research is needed in the fat placement technique, which has very little published evidence and current techniques are mostly anecdotal by cosmetic surgeons.

Human ESC-derived MSCs enhance fat engraftment by promoting adipocyte reaggregation, secreting CCL2 and mobilizing macrophages

Mesenchymal stem cells (MSCs) derived from somatic tissues have been used to promote lipotransfer, a common practice in cosmetic surgery. However, the effect of lipotransfer varies, and the mechanism of action remains vague. To address these questions, we differentiated human embryonic stem cells, a stable and unlimited source, into MSCs (EMSCs). Then we subcutaneously transplanted human fat aspirates together with EMSCs or PBS as a control into the back of nude mice. Within 24 h of transplantation, EMSCs promoted aggregation and encapsulation of injected fat tissues. Afterward, all grafts gradually shrank. However, EMSC-containing grafts were larger, heavier and had fewer dark areas on the surface than the control grafts. Histologically, more live adipocytes, vascular cells, and macrophages and less fibrosis were observed in EMSC-containing grafts than in the controls. Some EMSCs differentiated into vascular cells and adipocytes in the EMSC-containing grafts. RNA sequencing revealed that human RNA was shown to decline rapidly, while mouse RNA increased in the grafts; further, human genes related to extracellular matrix remodeling, adipogenesis, and chemokine (including CCL2) signaling were expressed at higher levels in the EMSC-containing grafts than they were in the controls. CCL2 knockout reduced macrophage migration towards EMSCs in vitro and early macrophage recruitment to the grafts and the pro-engraftment effect of EMSCs in vivo. Treating mice with a macrophage inhibitor abolished the EMSC effects and converted the grafts to heavy masses of cell debris. Together, these data demonstrate that EMSCs promote fat engraftment via enhanced tissue reconstitution and encapsulation of implanted tissues, which was followed by increased angiogenesis and adipocyte survival and reduced fibrosis, in which stimulated CCL2 signaling and mobilized macrophages play pivotal roles.

[Preliminary exploration on the application of hydrogel from acellular porcine adipose tissue to assist lipofilling]

Objective

To investigate the effect of hydrogel from acellular porcine adipose tissue (HAPA) on the survival of transplanted adipose tissue.

Methods

For in vitro study, adipose tissue and HAPA-adipose tissue complex were cultured in normoxia and hypoxia atmospheres for 24 and 72 hours. TUNEL and Perilipin immunofluorescence staining were performed to observe the effect of HAPA on apoptosis and survival of adipocities. For in vivo study, 42 healthy male nude mice (4-6 weeks old) weighing 15-18 g were randomly divided into adipose group (group A), 10%HAPA group (group B), 20%HAPA group (group C), 30%HAPA group (group D), 40%HAPA group (group E), and 50%HAPA group (group F) according to different HAPA/adipose tissue volume ratio ( n=7). For each group, 1 mL adipose tissue or HAPA-adipose tissue complex was injected subcutaneously into the dorsum of the nude mice. At 4 weeks after transplantation, 7 nude mice in each group were sacrificed and grafts were harvested, gross observation, volume measurement, ultrasound examination, and histologic staining (HE staining, CD31 and Perilipin immunofluorescence stainings) were applied.

Results

Hypoxia showed a tendency of promoting adipose tissue necrosis and apoptosis, while HAPA exhibited an obvious effect of inhibiting cell apoptosis in vitro study ( P<0.05). For in vivo study, grafts of all groups had intact fibrocapsule. No obvious signs of infection and necrosis were observed at 4 weeks. Volume shrinkage was observed in all groups, however, the groups A-D had significantly higher volume retention rate than groups E and F ( P<0.05). Ultrasound examination showed that there were no significant difference in the number and volume of liquify area of the grafts in each group ( P>0.05). With the increase of HAPA's volume ratio, HE staining proved an improved fat integrity while a gradually decreased vacuoles and fibrosis. CD31 immunohistochemical staining showed that the number of neo-vascularisation in groups E and F were significantly higher than those in groups A-D ( P<0.05). Perilipin immunofluorescence staining showed that with the increase of HAPA volume ratio, the number of living adipocytes increased gradually, and more new adipocytes could be seen in the field of vision.

Conclusion

As the volume ratio of HAPA gradually increased, the survival of transplanted adipose tissue also increased, but the volume retention rate decreased gradually. 30%HAPA was considered the relative optimal volume ratio for its superior adipose tissue survival and volume retation rate.

Fat Graft Enrichment Strategies: A Systematic Review

BACKGROUND

Autologous fat grafting is a dynamic modality used in plastic surgery as an adjunct to improve functional and aesthetic form. However, current practices in fat grafting for soft-tissue augmentation are plagued by tremendous variability in long-term graft retention, resulting in suboptimal outcomes and repetitive procedures. This systematic review identifies and critically appraises the evidence for various enrichment strategies that can be used to augment and improve the viability of fat grafts.

METHODS

A comprehensive literature search of the Medline and PubMed databases was conducted for animal and human studies published through October of 2017 with multiple search terms related to adipose graft enrichment agents encompassing growth factors, platelet-rich plasma, adipose-derived and bone marrow stem cells, gene therapy, tissue engineering, and other strategies. Data on level of evidence, techniques, complications, and outcomes were collected.

RESULTS

A total of 1382 articles were identified, of which 147 met inclusion criteria. The majority of enrichment strategies demonstrated positive benefit for fat graft survival, particularly with growth factors and adipose-derived stem cell enrichment. Platelet-rich plasma and adipose-derived stem cells had the strongest evidence to support efficacy in human studies and may demonstrate a dose-dependent effect.

CONCLUSIONS

Improved understanding of enrichment strategies contributing to fat graft survival can help to optimize safety and outcomes. Controlled clinical studies are lacking, and future studies should examine factors influencing graft survival through controlled clinical trials in order to establish safety and to obtain consistent outcomes.

Fat Therapeutics: The Clinical Capacity of Adipose-Derived Stem Cells and Exosomes for Human Disease and Tissue Regeneration

Fat grafting is a well-established surgical technique used in plastic surgery to restore deficient tissue, and more recently, for its putative regenerative properties. Despite more frequent use of fat grafting, however, a scientific understanding of the mechanisms underlying either survival or remedial benefits of grafted fat remain lacking. Clinical use of fat grafts for breast reconstruction in tissues damaged by radiotherapy first provided clues regarding the clinical potential of stem cells to drive tissue regeneration. Healthy fat introduced into irradiated tissues appeared to reverse radiation injury (fibrosis, scarring, contracture and pain) clinically; a phenomenon since validated in several animal studies. In the quest to explain and enhance these therapeutic effects, adipose-derived stem cells (ADSCs) were suggested as playing a key role and techniques to enrich ADSCs in fat, in turn, followed. Stem cells - the body's rapid response 'road repair crew' - are on standby to combat tissue insults. ADSCs may exert influences either by releasing paracrine-signalling factors alone or as cell-free extracellular vesicles (EVs, exosomes). Alternatively, ADSCs may augment vital immune/inflammatory processes; or themselves differentiate into mature adipose cells to provide the 'building-blocks' for engineered tissue. Regardless, adipose tissue constitutes an ideal source for mesenchymal stem cells for therapeutic application, due to ease of harvest and processing; and a relative abundance of adipose tissue in most patients. Here, we review the clinical applications of fat grafting, ADSC-enhanced fat graft, fat stem cell therapy; and the latest evolution of EVs and nanoparticles in healing, cancer and neurodegenerative and multiorgan disease.

Exosomes Are Comparable to Source Adipose Stem Cells in Fat Graft Retention with Up-Regulating Early Inflammation and Angiogenesis

BACKGROUND

Exosomes derived from mesenchymal stem cells possess functional properties similar to those of their parent cells, suggesting that they could play a pivotal role in tissue repair and regeneration.

METHODS

Using lipotransfer as a surrogate, exosomes were isolated from mouse adipose-derived stem cell-conditioned medium and characterized. Minced fat tissue mixed with exosomes, source cells (cell-assisted lipotransfer), or saline was implanted subcutaneously in the lower back of C57/BL mice bilaterally (n = 16 each). Transferred fat tissues were harvested and analyzed at 3 and 10 weeks.

RESULTS

At 3 and 10 weeks after the transfer, fat grafts in groups of exosomes and cell-assisted lipotransfer showed better fat integrity, fewer oil cysts, and reduced fibrosis. At week 10, graft retention rates in cell-assisted lipotransfer (50.9 ± 2.4 percent; p = 0.03) and exosome groups (56.4 ± 1.6 percent; p < 0.001) were significantly higher than in the saline group (40.7 ± 4.7 percent). Further investigations of macrophage infiltration, inflammatory factors, angiogenic factors, adipogenic factors, and extracellular matrix revealed that those exosomes promoted angiogenesis and up-regulated early inflammation, whereas during mid to late stages of fat grafting, they exerted a proadipogenic effect and also increased collagen synthesis level similarly to their source cells.

CONCLUSIONS

The adipose-derived stem cell-derived exosomes demonstrated effects comparable to those of their source cells in achieving improved graft retention by up-regulating early inflammation and augmenting angiogenesis. These features may enable exosomes to be an attractive cell-free alternative in therapeutic regenerative medicine.

Recipient-Site Preconditioning with Deferoxamine Increases Fat Graft Survival by Inducing VEGF and Neovascularization in a Rat Model

BACKGROUND

The authors hypothesize that ischemic preconditioning of the recipient site with deferoxamine will increase fat graft survival by enhancing angiogenesis in a rat model.

METHODS

Cell viability, tube formation, and mRNA expression were measured in human umbilical vein endothelial cells treated with deferoxamine. A total of 36 rats were then used for an in vivo study. A dose of 100 mg/kg of deferoxamine was injected subcutaneously into the rat scalp every other day for five treatments. On the day after the final injection, the scalp skin was harvested from half the animals to evaluate the effects of deferoxamine on the recipient site. In the remaining animals, inguinal fat tissue was transplanted to the scalp. Eight weeks after transplantation, the grafts were harvested to evaluate the effects of deferoxamine preconditioning on fat graft survival.

RESULTS

In human umbilical vein endothelial cells, treatment with a deferoxamine concentration higher than 400 μM decreased cell viability compared with the control (p = 0.002). Treatment with 100 and 200 μM deferoxamine increased endothelial tube formation (p = 0.001) and mRNA levels of angiogenesis-related factors (p = 0.02). Rat scalps treated with deferoxamine exhibited increased capillary neoformation (p = 0.001) and vascular endothelial growth factor protein expression (p = 0.024) compared with controls. Fat graft volume retention, capillary density (p < 0.001), and adipocyte viability (p < 0.001) in the grafted fat increased when the recipient site was preconditioned with deferoxamine.

CONCLUSION

This study demonstrated that recipient site preconditioning with deferoxamine increases fat graft survival by inducing vascular endothelial growth factor and neovascularization.

Cell-Enriched Fat Grafting Improves Graft Retention in a Porcine Model: A Dose-Response Study of Adipose-Derived Stem Cells versus Stromal Vascular Fraction

BACKGROUND

Cell-enrichment of fat grafts has produced encouraging results, but the optimal concentrations and types of added cells are unknown. The authors investigated the effects of enrichment with various concentrations of ex vivo-expanded adipose-derived stem/stromal cells and stromal vascular fraction on graft retention in a porcine model.

METHODS

Adipose-derived stem/stromal cells were culture-expanded, and six fat grafts (30 ml) were prepared for each minipig (n = 13). The authors investigated grafts enriched with 2.5 × 10 to 20 × 10 adipose-derived stem cells/ml and stromal vascular fraction and nonenriched control grafts. Each pig served as its own control. Magnetic resonance imaging was performed immediately after grafting and 120 days postoperatively before the pigs were euthanized, and histologic samples were collected.

RESULTS

The authors recorded an enhanced relative graft retention rate of 41 percent in a pool of all cell-enriched grafts compared to the nonenriched control (13.0 percent versus 9.2 percent; p = 0.0045). A comparison of all individual groups showed significantly higher graft retention in the 10 × 10-adipose-derived stem/stromal cells per milliliter group compared with the control group (p = 0.022). No significant differences were observed between the cell-enriched groups (p = 0.66). All fat grafts showed a significantly better resemblance to normal fat tissue in the periphery than in the center (p < 0.009), but no differences in overall graft morphology were observed between groups (p > 0.17).

CONCLUSIONS

Cell-enriched fat grafting improved graft retention and was feasible in this porcine model. No significant differences in graft retention were observed among the various adipose-derived stem/stromal cell concentrations or between adipose-derived stem/stromal cell and stromal vascular fraction enrichment. Future studies using this model can help improve understanding of the role of adipose-derived stem/stromal cells in cell-enriched fat grafting.

Electrical stimulation promotes the angiogenic potential of adipose-derived stem cells

Autologous fat transfer (AFT) is limited by post-operative volume loss due to ischemia-induced cell death in the fat graft. Previous studies have demonstrated that electrical stimulation (ES) promotes angiogenesis in a variety of tissues and cell types. In this study we investigated the effects of ES on the angiogenic potential of adipose-derived stem cells (ASC), important progenitor cells in fat grafts with proven angiogenic potential. Cultured human ASC were electrically stimulated for 72 hours after which the medium of stimulated (ES) and non-stimulated (control) ASC was analysed for angiogenesis-related proteins by protein array and ELISA. The functional effect of ES on angiogenesis was then assessed in vitro and in vivo. Nine angiogenesis-related proteins were detected in the medium of electrically (non-)stimulated ASC and were quantified by ELISA. The pro-angiogenic proteins VEGF and MCP-1 were significantly increased following ES compared to controls, while the anti-angiogenic factor Serpin E1/PAI-1 was significantly decreased. Despite increased levels of anti-angiogenic TSP-1 and TIMP-1, medium of ES-treated ASC significantly increased vessel density, total vessel network length and branching points in chorio-allantoic membrane assays. In conclusion, our proof-of-concept study showed that ES increased the angiogenic potential of ASC both in vitro and in vivo.

The Preparation of the Recipient Site in Fat Grafting: A Comprehensive Review of the Preclinical Evidence

BACKGROUND

Several methods to prepare the recipient site in fat grafting have been proposed in recent decades. However, to date, these procedures have never been reviewed exhaustively. The purpose of the present study is to provide a comprehensive overview of the different techniques to prepare the recipient site for fat grafting as they were investigated in preclinical studies, with resulting outcomes and underlying mechanisms of action.

METHODS

The PubMed/MEDLINE database was queried to search for preclinical investigations on the preparation of the recipient site in fat grafting using the following algorithm: ((recipient site) AND (fat grafting) OR (lipofilling) OR (lipograft)). A priori criteria were applied to review the resulting articles.

RESULTS

Thirteen animal studies met inclusion criteria. Overall, five techniques were identified: external volume expansion, implantation of alloplastic material (silicone sheets), administration of cell-proliferation factors (i.e., vascular endothelial growth factor, adipose tissue-derived stromal vascular fraction, and interleukin-8), ischemia, and microneedling. A positive effect on cellular activity (cell proliferation and angiogenesis) was demonstrated by all studies and achieved with all techniques. Seven of the eight authors who examined this aspect reported enhancement of fat graft survival.

CONCLUSIONS

Improvement of fat grafting surgical outcomes is documented preclinically using different recipient-site preparation techniques, particularly through enhancement of vascularization and soft-tissue expansion. This understanding will lead to further clinical research, especially for those cases where improvement of the recipient site is recommended, such as contracted scars or preirradiated tissues.

Insulin Promotes Adipose-Derived Stem Cell Differentiation after Fat Grafting

BACKGROUND

Adipose-derived stem cells are used to enhance fat graft survival. However, their mechanism of action when grafted is controversial. The grafted cells can be replaced by connective tissue or survive at the recipient site and differentiate. Insulin is a powerful agent used to induce their differentiation to adipocytes. The purpose of this study was to elucidate the fate of grafted adipose-derived stem cells in nonvascularized fat grafts with or without insulin.

METHODS

Fat was harvested from a female human donor who had undergone reduction mammaplasty. The authors also isolated and cultured adipose-derived stem cells expressing green fluorescent protein from transgenic Sprague-Dawley rats. Injection of free fat graft, the adipose-derived stem cells, phosphate-buffered saline, and insulin was performed on the four paravertebral points of the back of each mouse (n = 30) as follows: group A (control group) received adipose tissue and phosphate-buffered saline; group B received adipose tissue and adipose-derived stem cells; group C received adipose tissue, adipose-derived stem cells, and phosphate-buffered saline; and group D received adipose tissue, adipose-derived stem cells, and insulin. Green fluorescent protein expression was evaluated using an in vivo imaging system. The volume of transplanted fat was evaluated at 8 weeks after graft with six histologic parameters. The fat graft was immunostained with green fluorescent protein, 4',6-diamidino-2-phenylindole, and perilipin. Statistical analysis was performed using a one-way analysis of variance test.

RESULTS

The fat graft volume was significantly higher in group D (p < 0.05). Histologic examination revealed reduced fibrosis and increased cysts, vacuoles, integrity, and vascularity in group D. The green fluorescent protein and perilipin co-positive area was more apparent in group D compared with groups B and C.

CONCLUSION

Insulin could enhance the survival and differentiation of adipose-derived stem cells in nonvascularized fat grafts.

Endothelial Differentiated Adipose-Derived Stem Cells Improvement of Survival and Neovascularization in Fat Transplantation

Background

Adipose-derived stem cells (ASCs) assisted lipotransfer have been considered to facilitate the survival of fat grafts. However, emerging evidence of insufficient vascularization is another obstacle for fat graft survival in cell-assisted lipotransfer.

Objectives

This study evaluated if endothelial phenotype ASCs with fat lipoaspirate improves survival and neovascularization in fat transplantation.

Methods

ASCs were isolated from human periumbilical fat tissue and cultured in endothelial growth medium for 2 weeks. Fat lipoaspirate was mixed with fresh adipose stroma vascular fraction (SVF), endothelial differentiated ASCs (EC/ASCs), and fat lipoaspirate alone. Three fat mixtures were subcutaneously injected into the adult male Sprague-Dawley rat's dorsum at 3 locations. At 8 weeks after transplantation, the grafted fat lipoaspirates were harvested, and the extracted fat was evaluated using photographic, survival weights measurements and histological examination. Neo-vascularization was quantified by immunofluorescence and real-time RT-PCR.

Results

Grafts from the EC/ASC assisted group had a higher survival rate, morphologic integrity, and most uniform lipid droplets. They also revealed less inflammation and fibrosis with increased number of vessels by histological and immunofluorescence analysis. Quantitative RT-PCR analysis indicated that the expression levels of EC-specific markers of CD31 and vWF were higher in the EC/ASC group compared with in the control and fat with SVF transplants.

Conclusions

These results indicated that co-implantation of fat lipoaspirate with ASCs differentiated toward an endothelial phenotype improves both survival and neovascularization of the transplanted fat lipoaspirate, which might provide benefits and represents a promising strategy for clinical application in autologous fat transplantation.

Co-Transplantation of Nanofat Enhances Neovascularization and Fat Graft Survival in Nude Mice

BACKGROUND

Autologous fat grafting is commonly used for soft-tissue augmentation and reconstruction. However, this technique is limited by a high rate of graft absorption. Thus, approaches to improve fat graft survival that promote neovascularization are of great interest. Nanofat has several beneficial features that may render it more suitable for clinical applications than other stem-cell based approaches.

OBJECTIVES

We aimed to determine whether nanofat could enhance new vessel formation and improve the long-term retention of fat grafts.

METHODS

Nanofat was processed via mechanical emulsification and filtration. Fat grafts were transplanted subcutaneously under the scalps of nude mice with different nanofat volumes or without nanofat. The grafted fat was dissected 12 weeks after transplantation. Graft weight and volume were measured, and histological evaluations, including capillary density measurement, were performed.

RESULTS

The co-transplantation of fat with nanofat showed higher graft weight and volume retention, better histological structure, and higher capillary density compared to that in controls. However, there were no significant differences between the two nanofat volumes utilized.

CONCLUSIONS

Nanofat can enhance neovascularization and improve fat graft survival, providing a potential clinically viable approach to fat graft supplementation in plastic and reconstructive surgery.

Effects of Collagenase Digestion and Stromal Vascular Fraction Supplementation on Volume Retention of Fat Grafts

OBJECTIVE

The use of autologous fat as a soft tissue filler has increased over the past decade in both reconstructive and aesthetic surgeries. Enhancement of autologous fat grafts with the addition of the stromal vascular fraction (SVF) has been reported to improve long-term volume retention. Stromal vascular fraction is most commonly isolated using enzymatic digestion, but it is unknown what effect the digestion process has on the adipocytes and SVF cells that comprise the graft. Some clinicians have reported use of enzymatically digested fat grafts to alter the physical properties of the tissue in specialized applications. We have previously reported that increasing collagenase digestion duration adversely affects the viability of adipocytes and SVF cells. Here, we aimed to determine if collagenase digestion of adipocytes before grafting is detrimental to long-term graft retention and if SVF supplementation can abrogate these potential deleterious effects.

METHODS AND RESULTS

We used a published xenograft model in which human lipoaspirate was implanted into the scalp of immunocompromised mice to study the effects of collagenase digestion on in vivo graft survival after 12 weeks. We used 4 experimental groups: grafts composed of collagenase-digested and nondigested adipocytes (50-minute digestion) and grafts with and without SVF supplementation. We used microcomputed tomography to serially and noninvasively quantify graft volume, in conjunction with hematoxylin-eosin staining of histological cross-sections of implanted and excised grafts to assess overall tissue viability. We found that adipocytes that were collagenase-digested before implantation had significantly lower retention rates at 12 weeks and poorer tissue health, which was assessed by quantifying the number of intact adipocytes, the number of cystic formations, and by scoring the degree of inflammation and fibrosis. Further, we found that SVF supplementation of the digested grafts improved graft survival, but not to the level observed in undigested grafts.

CONCLUSIONS

We conclude that collagenase digestion adversely affects the long-term volume retention of fat grafts, but that graft retention is improved by SVF supplementation. These experimental results can serve as an initial framework to further elucidate the reported efficacy and safety of using collagenase-digested fat grafts and SVF in the clinical setting.

Clinical Application of Platelet-Rich Fibrin in Plastic and Reconstructive Surgery: A Systematic Review

BACKGROUND

Platelet-rich fibrin (PRF) has been applied in the clinical field for more than a decade, but largely in oral surgery and implant dentistry. Its utilization in plastic and reconstructive surgery is limited and lacking a comprehensive review. Hence, this article focuses on the various clinical applications of PRF pertaining to the plastic and reconstructive field through a systematic review.

METHODS

In this review, articles describing the clinical application of PRF in plastic and reconstructive surgery were screened using predetermined inclusion and exclusion criteria. The articles were summarized and divided into groups based on the utilization of PRF. The effects and complications of PRF were analyzed and concluded.

RESULTS

Among the 634 articles searched, 7 articles describing 151 cases are eligible. PRF was applied on 116 (76.8%) wounds to facilitate tissue healing, and the complete wound closure rate was 91.4% (106/116). Otherwise, PRF was applied in 10 (6.6%) cases of zygomaticomaxillary fracture to reconstruct orbital floor defects and in 25 (16.6%) cases of facial autologous fat grafts to increase the fat retention rate successfully. There is no report of PRF-related complications.

CONCLUSIONS

PRF could facilitate wound healing, including the healing of soft tissues and bony tissues, and facilitate fat survival rate. Further studies are needed to test the mechanism of PRF and expand its scope of application in plastic and reconstructive surgery.

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 .

Heat-Shock Protein 70 Overexpression in Adipose-Derived Stem Cells Enhances Fat Graft Survival

BACKGROUND

Autologous fat grafting is a prevalent technique used for soft-tissue augmentation; however, the poor survival rate of the grafted tissue remains a drawback of this method. Although adipose-derived stem cells (ASCs) are an attractive candidate for enhancing graft retention, the poor posttransplantation viability of these cells limits their application. Here we investigated whether overexpression of the antiapoptotic protein heat-shock protein 70 (Hsp70) could enhance ASCs' therapeutic potential for fat transplant survival.

METHODS

Recombinant adenoviral vectors were used to overexpress Hsp70 in ASCs isolated from a healthy woman. The Hsp70 expression was assessed by quantitative real-time polymerase chain reaction and Western blot analyses. The adipose tissue granules aspirated from another woman were mixed with ASCs expressing green fluorescent protein (GFP)-tagged Hsp70 (group A) or GFP alone (group B), untreated ASCs (group C), and phosphate-buffered saline (group D). Fat mixtures were then injected subcutaneously into the backs of nude mice, and graft survival was compared after 3 months.

RESULTS

Adipose-derived stem cells transduced with recombinant adenoviral vectors exhibited significantly increased Hsp70 expression in vitro. Meanwhile, weight retention analyses demonstrated that fat grafts using the group A cell population exhibited significantly higher survival rates than the other treatment groups in vivo. Moreover, histological analyses revealed that fat grafts containing GFP-Hsp70-expressing ASCs yielded significantly lower levels of tissue fibrosis and fat cysts/vacuoles, higher capillary densities, and increased numbers of viable adipocytes than the control groups.

CONCLUSIONS

Our data indicate that Hsp70 overexpression enhances the efficacy of ASC therapy by improving the survival and quality of the transplanted fat tissues.

Bone marrow mesenchymal stem cell‑derived extracellular vesicles improve the survival of transplanted fat grafts

Autologous fat grafting is a promising surgical technique for soft tissue augmentation, reconstruction and rejuvenation. However, it is limited by the low survival rate of the transplanted fat, due to the slow revascularization of such grafts. Previous studies have demonstrated that bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) are proangiogenic. The present study aimed to investigate whether BMSC-EVs could improve the survival of transplanted fat grafts. Extracellular vesicles were isolated from the supernatant of cultured rat bone marrow mesenchymal stem cells, and characterized by flow cytometry and scanning electron microscopy. Their proangiogenic potential was measured in vitro using tube formation and cell migration assays. Subsequently, human fat tissue grafts, alongside various concentrations of BMSC-EVs, were subcutaneously injected into nude mice. A total of 12 weeks following transplantation, the mice were sacrificed and the grafts were harvested. The grafts from the experimental group had a higher survival rate and an increased number of vessels compared with grafts from the control group, as demonstrated by tissue volume, weight and histological analyses. Reverse transcription-quantitative polymerase chain reaction analysis indicated that the expression levels of proangiogenic factors were increased in the experimental group compared with in the control group, thus suggesting that BMSC-EVs may promote neovascularization by stimulating the secretion of proangiogenic factors. The present study is the first, to the best of our knowledge, to demonstrate that supplementation of fat grafts with BMSC-EVs improves the long-term retention and quality of transplanted fat.

[Ultrasonic examination of the breast adipose grafts after mammoplasty]

AIM

To present the results of PRP-adipose grafts implanatation.

MATERIAL AND METHODS

The study included 25 patients after transplantation of autologous adipose tissue. Autotransplantation was performed to correct volume defects of breast and to restore lost volume after polyacrylamide gel removal in 4 patients; after mastectomy in 6 cases; after complicated replacement using silicone endoprostheses in 11 patients; after previous reduction in 2 cases; after augmentation mammoplasty in 2 cases. Mean age of patients was 42 years. Patients were divided into 2 groups. Group 1 included 12 patients in whom pure adipose tissue was transplanted. Group 2 consisted of 13 patients who received autologous fat with platelet-rich plasma (PRP).

RESULTS

Dynamic ultrasonic monitoring showed early resorption processes (liponecrosis foci) after autologous fat injection. Locally increased vascular pattern of breast tissue is an inflammatory sign requiring anti-inflammatory therapy. PRP-adipose grafts have improved outcomes.

The Opposite Expected Effect of p38 Inhibitors on Fat Graft Survival

BACKGROUND

Fat grafting is an increasingly popular method of augmentation/reconstruction of soft tissue defects. However, the clinical unpredictability and high resorption rates of the grafts remain problematic. Cellular stress from the harvest and the ensuing ischemic episode may be the cause of this. Cellular stress activates the p38 mitogen-activated protein kinase (MAPK) signaling pathway. In response to cellular stress, the p38 pathway can lead to apoptosis and can negatively regulate cell proliferation. Inhibition of p38 in ex vivo experiments has been shown to promote the expansion of human cord blood hematopoietic stem cell and improve the adipogenesis process through its upstream regulator, Shp2. Because of its wide-ranging cell regulation and antiinflammatory properties, large-scale clinical trials using p38 inhibitors are also currently being performed, especially for therapeutic effect in chronic obstructive pulmonary disease and asthma. The rationale for our study was that the treatment of fat grafts with p38 inhibitor would (a) prevent apoptosis of adipose-derived stem cells in the fat grafts, (b) increase adipose-derived stem cells proliferation, and (c) stimulate the release of several angiogenic factors and promote revascularization.

METHODS

Clinical and histological testing was performed on 5 fat-transplanted (1 mL) CD-1 nude mice compared with the test group of 5 mice, which were injected with a p38 MAPK inhibitor at 1, 3, 6, and 9 days after the fat transplantation.

RESULTS

The weights and volumes of the control group grafts were significantly higher than those of the p38 MAPK inhibitor-treated grafts. Average volume resorption was 36% in the control group and 92% in the test group. Histological evaluation of the grafts revealed significantly improved integration, with a significant reduction of fibrosis and inflammation in the control group versus the treated group.

CONCLUSIONS

This preliminary study suggests that as opposed to our hypothesis, inhibition of p38 significantly increases fat graft resorption. The dramatic effects observed in our study may suggest that p38 may act differently on the numerous cell types that constitute the fat graft, and further investigation is necessary.

An Overview of Fat Grafting

The use of autologous fat grafting for a wide variety of clinical applications has increased dramatically over the past few decades. The article provides an overview of the technique, a historic background, and briefly explores some of the current ways in which fat grafting is being used in plastic surgery.

Autologous fat grafting: current state of the art and critical review

BACKGROUND

Despite the widespread use of autologous fat grafting in both reconstructive and cosmetic surgery, volume retention remains a significant problem. We aimed to critically appraise the current body of literature in fat grafting to provide a framework to guide application and comparison.

METHOD

Search of scientific databases and gray literature was conducted. Articles examining nonadipogenic applications of adipose tissue and those specific to breast reconstruction were excluded.

RESULTS

One hundred three articles were included. These fell under the headings of donor site, effect of infiltration solution, harvest method, effect of centrifugation, reinjection method, supplementation, the role of adipose-derived stem cells, and scaffolding.

CONCLUSIONS

Despite the significant research effort in this field, there remains no consensus as to the optimum technique. This stems from the vast array of research methods and short follow-up durations. Further, extrapolation of in vitro results to clinical settings has led to many conflicting practices.

The effect of combined use of platelet-rich plasma and adipose-derived stem cells on fat graft survival

BACKGROUND

Free fat grafts have an unpredictable survival rate that limits their successful use. To increase the viability of fat grafts, it is important to minimize the reabsorption rate.

OBJECTIVE

Our aim was to investigate whether the combined use of platelet-rich plasma (PRP) and adipose derived stem cells (ADSCs) would contribute an improvement in lower resorption rates of fat grafts.

METHODS

Inbred Fischer 344 rats were randomized into 4 groups (n = 10). Fat grafts were mixed with Dulbecco modified Eagle medium in group A, with PRP in group B, with ADSC in group C, and with PRP + ADSC in group D and were injected to the scalp.In vitro growth factor (vascular endothelial growth factor, transforming growth factor-β, and fibroblast growth factor) levels were compared using enzyme-linked immunoassay method. After 12 weeks weight, volume and histology of the transplants were evaluated.

RESULTS

The mean weight and volume of the fat grafts were highest in group D. Histopathological investigations revealed that the number of viable adipocytes and blood vessels were highest in group D. The level of growth factors was significantly higher in stem cell plus PRP group.

CONCLUSION

Adipose-derived stem cells combined with PRP can enhance the survival of transplanted fat tissue.

Effect of N-Acetylcysteine on Adipose-Derived Stem Cell and Autologous Fat Graft Survival in a Mouse Model

BACKGROUND

Autologous fat grafting is a popular reconstructive technique, but is limited by inconsistent graft retention. The authors examined whether a widely available, clinically safe antioxidant, N-acetylcysteine, could improve adipose-derived stem cell survival and graft take when added to tumescent solution during fat harvest.

METHODS

Inguinal fat pads were harvested from C57BL/6 mice using tumescent solution with or without N-acetylcysteine. Flow cytometric, proliferation, and differentiation assays were performed on isolated primary adipose-derived stem cells and 3T3-L1 preadipocytes treated with or without hydrogen peroxide and/or N-acetylcysteine. N-Acetylcysteine-treated or control grafts were injected under recipient mouse scalps and assessed by serial micro-computed tomographic volumetric analysis. Explanted grafts underwent immunohistochemical analysis.

RESULTS

In culture, N-acetylcysteine protected adipose-derived stem cells from oxidative stress and improved cell survival following hydrogen peroxide treatment. Combined exposure to both N-acetylcysteine and hydrogen peroxide led to a 200-fold increase in adipose-derived stem cell proliferation, significantly higher than with either agent alone. N-Acetylcysteine decreased differentiation of adipose-derived stem cells into mature adipocytes, as evidenced by decreased transcription of adipocyte differentiation markers and reduced Oil Red-O staining. In vivo, N-acetylcysteine treatment resulted in improved graft retention at 3 months compared with control (46 versus 17 percent; p = 0.027). N-Acetylcysteine-treated grafts demonstrated less fibrosis and inflammation, and a 33 percent increase in adipocyte density compared with controls (p < 0.001) that was not associated with increased vascularity.

CONCLUSION

These findings provide proof of principle for the addition of N-acetylcysteine to tumescent harvest solution in the clinical setting to optimize fat graft yields.

Studies in Fat Grafting: Part V. Cell-Assisted Lipotransfer to Enhance Fat Graft Retention Is Dose Dependent

BACKGROUND

Cell-assisted lipotransfer has shown much promise as a technique for improving fat graft take. However, the concentration of stromal vascular fraction cells required to optimally enhance fat graft retention remains unknown.

METHODS

Human lipoaspirate was processed for both fat transfer and harvest of stromal vascular fraction cells. Cells were then mixed back with fat at varying concentrations ranging from 10,000 to 10 million cells per 200 μl of fat. Fat graft volume retention was assessed by means of computed tomographic scanning over 8 weeks, and then fat grafts were explanted and compared histologically for overall architecture and vascularity.

RESULTS

Maximum fat graft retention was seen at a concentration of 10,000 cells per 200 μl of fat. The addition of higher number of cells negatively impacted fat graft retention, with supplementation of 10 million cells producing the lowest final volumes, lower than fat alone. Interestingly, fat grafts supplemented with 10,000 cells showed significantly increased vascularity and decreased inflammation, whereas fat grafts supplemented with 10 million cells showed significant lipodegeneration compared with fat alone

CONCLUSIONS

: The authors' study demonstrates dose dependence in the number of stromal vascular fraction cells that can be added to a fat graft to enhance retention. Although cell-assisted lipotransfer may help promote graft survival, this effect may need to be balanced with the increased metabolic load of added cells that may compete with adipocytes for nutrients during the postgraft period.

Targeted protection of donor graft vasculature using a phosphodiesterase inhibitor increases survival and predictability of autologous fat grafts

BACKGROUND

Fat grafting is limited by unpredictable long-term graft retention. The authors postulate that injury to the donor-derived microvasculature during harvest and subsequent ischemia may account for this clinical variability. They examined the use of the U.S. Food and Drug Administration-approved phosphodiesterase-5 inhibitor sildenafil citrate to protect graft microvasculature and its role in revascularization and survival.

METHODS

Inguinal fat of donor Tie2/LacZ mice was infiltrated with sildenafil or saline, harvested, and transplanted onto the dorsa of recipient FVB mice. Additional donor mice were perfused with intraarterial trypsin to inactivate the fat graft microvasculature before harvest and transplantation. Differences in graft revascularization, perfusion, volume of retention, and biochemical changes were assessed.

RESULTS

Surviving fat grafts were characterized by exclusively donor-derived vasculature inosculating with the recipient circulation at the graft periphery. Inactivation of donor-derived microvasculature decreased early graft perfusion and led to nearly total graft loss by 8 weeks. Sildenafil attenuated vascular ischemic injury, consistent with reductions in VCAM-1 and SDF1α expression at 48 hours and 4-fold increases in microvasculature survival by 2 weeks over controls. Compared with controls, targeted sildenafil treatment improved early graft perfusion, doubled graft retention at 12 weeks (83 percent versus 39 percent; p < 0.05), ultimately retaining 64 percent of the original graft volume by 24 weeks (compared to 4 percent; p < 0.05) with superior histologic features.

CONCLUSIONS

Fat graft vascularization is critically dependent on maintenance of the donor microvasculature. Sildenafil protects the donor microvasculature during transfer and revascularization, increasing long-term volume retention. These data demonstrate a rapidly translatable method of increasing predictability and durability of fat grafting in clinical practice.

Adipose-derived stem cells in radiotherapy injury: a new frontier

Radiotherapy is increasingly used to treat numerous human malignancies. In addition to the beneficial anti-cancer effects, there are a series of undesirable effects on normal host tissues surrounding the target tumor. While the early effects of radiotherapy (desquamation, erythema, and hair loss) typically resolve, the chronic effects persist as unpredictable and often troublesome sequelae of cancer treatment, long after oncological treatment has been completed. Plastic surgeons are often called upon to treat the problems subsequently arising in irradiated tissues, such as recurrent infection, impaired healing, fibrosis, contracture, and/or lymphedema. Recently, it was anecdotally noted - then validated in more robust animal and human studies - that fat grafting can ameliorate some of these chronic tissue effects. Despite the widespread usage of fat grafting, the mechanism of its action remains poorly understood. This review provides an overview of the current understanding of: (i) mechanisms of chronic radiation injury and its clinical manifestations; (ii) biological properties of fat grafts and their key constituent, adipose-derived stem cells (ADSCs); and (iii) the role of ADSCs in radiotherapy-induced soft-tissue injury.

Improvement of the survival of autologous free-fat transplants in rats using vascular endothelial growth factor 165-transfected bone mesenchymal stem cells

BACKGROUND

Autologous free-fat transplantation is limited by fat absorption and fibrosis due to fat necrosis. In this study, we explored the feasibility of using bone mesenchymal stem cells (BMSCs) transfected by vascular endothelial growth factor (VEGF) 165 gene to improve the survival of transplanted fat tissues in a rat model.

METHODS

Bone mesenchymal stem cells with (group A) and without (group B) VEGF165 gene transfection were each mixed with free transplanted fat tissue; then, they were injected subcutaneously at sites on the backs of 36 Sprague-Dawley rats. A control group (group C) was established by using low-glucose Dulbecco modified Eagle medium. The transplants from groups A, B, and C were gathered respectively at 30, 90, and 180 days after transplantation. Transplanted tissue volume and histology were evaluated, and revascularization was quantified by counting the number of capillaries.

RESULTS

The survival rate of the A group was significantly higher than that of the B group (P < 0.05), which was significantly higher than that of the C group (P < 0.05). Histologic analysis revealed that both groups A and B had significantly less fat necrosis and fibrosis (P < 0.05). Group A had significantly higher capillary density than the other 2 groups (P < 0.05), and its chloromethyl-1-1'-dioctadecyl-3,3,3', 3'-tetramethylindocarbocyanineperchlorate-labeled BMSCs were also von Willebrand factor positive.

CONCLUSIONS

When transfected by the VEGF165 gene, the BMSCs of a rat can better promote the regeneration of capillaries, which can improve the survival rate of transplanted free-fat tissue. This experiment combined correlative theory and techniques of stem cell research, genetic technology, and autologous free-fat transplantation. It may provide a new way to improve the survival of tissue undergoing autologous free-fat transplantation.

Platelet-rich plasma mixed-fat grafting: a reasonable prosurvival strategy for fat grafts?

BACKGROUND

One of the most interesting developments in practical applications of fat grafting in recent years is the use of prosurvival strategies to improve maintenance of volume. Platelet-rich plasma (PRP) plays a decisive role in the repair and regeneration of different tissues via the activation and secretion of a great variety of growth factors and other cytokines stored in the alpha-granules of the platelets. This review aimed to assess the efficacy of PRP mixed-fat grafting as a prosurvival strategy for fat grafts.

METHODS

Online searches of the Cochrane Library and MEDLINE until January 2014 were conducted. The review included studies with at least one clinical end point in which the effect of PRP on the absorption and viability of the fat graft could be assessed.

RESULTS

The review comprised 6 preclinical studies with a control group and 9 clinical studies of humans. It also included comparative studies performed with other prosurvival strategies for fat grafts, such as combination with the stromal vascular fraction and second-generation PRP, also called "platelet-rich fibrin." The results indicate that PRP may have a dose-dependent positive effect on fat grafts and suggest low complication rates.

CONCLUSIONS

The development of new growth factor delivery systems or cell therapies to enrich fat grafts is an area that merits further research.

Effects of the diabetic condition on grafted fat survival: an experimental study using streptozotocin-induced diabetic rats

Background

Autologous fat grafts have been widely used for cosmetic purposes and for soft tissue contour reconstruction. Because diabetes mellitus is one of the major chronic diseases in nearly every country, the requirement for fat grafts in diabetes patients is expected to increase continuously. However, the circulation complications of diabetes are serious and have been shown to involve microvascular problems, impairing ischemia-driven neovascularization in particular. After injection, revascularization is vital to the survival of the grafted fat. In this study, the authors attempted to determine whether the diabetic condition inhibits the survival of injected fat due to impaired neovascularization.

Methods

The rat scalp was used for testing fat graft survival. Forty-four seven-week-old male Sprague-Dawley rats were allocated to a diabetic group or a control group. 1.0 mL of processed fat was injected subcutaneously into the scalp of each rat. The effect of diabetes was evaluated by calculating the volume and the weight of the grafted fat and by histologically analyzing the fat sections.

Results

The surviving fat graft volume and weight were considerably smaller in the diabetic group than in the control group (P<0.05), and histological evaluations showed less vascularity, and more cysts, vacuoles, and fibrosis in the diabetic group (P<0.05). Cellular integrity and inflammation were not considerably different in the two groups.

Conclusions

As the final outcome, we found that the presence of diabetes might impair the survival and the quality of fat grafts, as evidenced by lower fat graft weights and volumes and poor histologic graft quality.