VEGF gene therapy for the survival of transplanted fat tissue in nude mice

Brown Adipose Tissue Promotes Autologous Fat Grafts Retention Possibly Through Inhibiting Wnt/β-Catenin Pathway

BACKGROUND

In plastic surgery, autologous fat grafts (AFG) play an important role because of their abundant supply, biocompatibility, and low rejection rate. However, the lower retention rate of fat grafts limits their widespread use. Brown adipose tissue (BAT) can promote angiogenesis and regulate the level of associated inflammation. This study explored whether BAT has a facilitative effect on fat graft retention.

METHODS

We obtained white adipose tissue (WAT) from c57 mice and combined it with either BAT from c57 mice or phosphate-buffered saline (PBS) as a control. These mixtures were injected subcutaneously into the back of thymus-free nude mice. After 12 weeks, fat grafts were harvested, weighed, and analyzed.

RESULTS

We found that the BAT-grafted group had higher mass retention, more mature adipocytes, and higher vascularity than the other group. Further analysis revealed that BAT inhibited M1 macrophages; down-regulated IL-6, IL-1β, and TNF-β; upregulated M2 macrophages and Vascular endothelial growth factor-A (VEGFA); and promoted adipocyte regeneration by inhibiting the Wnt/β-catenin pathway, which together promoted adipose graft retention.

CONCLUSION

The study demonstrated that BAT improved adipose graft retention by promoting angiogenesis, inhibiting tissue inflammation levels and the Wnt/β-catenin pathway.

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.

Fatter Is Better: Boosting the Vascularization of Adipose Tissue Grafts

Adipose tissue resorption after fat grafting is a major drawback in plastic and reconstructive surgery, which is primarily caused by the insufficient blood perfusion of the grafts in the initial phase after transplantation. To overcome this problem, several promising strategies to boost the vascularization and, thus, increase survival rates of fat grafts have been developed in preclinical studies in recent years. These include the angiogenic stimulation of the grafts by growth factors and botulinum neurotoxin A, biologically active gels, and cellular enrichment, as well as the physical and pharmacological stimulation of the transplantation site. To transfer these approaches into future clinical practice, it will be necessary to establish standardized procedures for their safe application in humans. If this succeeds, the surgical outcomes of fat grafting may be markedly improved, resulting in a significant reduction of the physical and psychological stress for the patients.

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.

Effect of Adipose-Derived Stem Cell on Collagen Deposition in Nude Mouse Model of Scleroderma

Systemic sclerosis is an autoimmune disease featured by uncontrolled fibrosis and collagen deposition. This study aimed to investigate the impact of adipose-derived stem cells (ADSCs) transplantation on collagen in scleroderma. After establishment of scleroderma model using Bleomycin, the animals received subcutaneous injection of 0.3 ml fat (group B) or 0.3 ml fat+1×106 ADSCs (group C), or 1×106 ADSCs alone (group D). Mice treated with PBS were taken as control group (group A). One month after operation, the skin tissue at injection site was collected for H&E staining, and immunohistochemistry to determine the content of TGF-β1 and type III collagen. Compared to control group, group B, C, and D exhibited improvement in collagen deposition and reduction in TGF-β1 content and type III collagen. Combined graft of fat and ADSCs exerted more significant effect compared to single ADSCs treatment. In conclusion, fat and ADSCs transplantation improves collagen deposition in nude mice with scleroderma and the combined treatment exerts a higher efficacy, suggesting that ADSCs need adipose carrier and microenvironment. These findings provide a novel insight into the treatment of scleroderma.

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.

Effects of Temporary and Permanent Muscle Denervation on Fat Graft Retention in the Latissimus Dorsi Muscle: An Experimental Study in Rats

BACKGROUND

In breast reconstruction with a latissimus dorsi flap, immediate fat grafting is useful for increasing flap volume. However, factors such as latissimus dorsi muscle atrophy and fat graft retention affect the volume of the reconstructed breast, and reports are inconsistent regarding treatment of the thoracodorsal nerve. This study examined how thoracodorsal nerve treatment affects the rates of latissimus dorsi flap preservation and fat graft retention using a rat model.

METHODS

Fat harvested from the inguinal region was grafted to the latissimus dorsi muscle elevated as a pedicled muscle flap on the experimental side and to the intact LD muscle on the contralateral side (control). Rats were divided into intact thoracodorsal nerve (Ni), temporary denervation (Ntd), and permanent denervation (Npd) groups (n = 8 each). Fat retention and muscle preservation rates were determined, and histological changes were analyzed postoperatively.

RESULTS

Fat retention rates did not significantly differ between the Ni and Ntd groups. Only the Npd group showed a significant decrease in fat retention rate relative to the control side (p < 0.01). The quality of the grafted fat as reflected by histological parameters was significantly lower, and the viable adipocyte area and muscle fiber preservation rate significantly decreased, in the Npd group compared to the other groups.

CONCLUSIONS

Permanent thoracodorsal nerve denervation resulted in severe muscle atrophy and a significantly decreased fat retention rate. Temporary denervation had no significant benefit, suggesting that preserving the thoracodorsal nerve may be desirable for achieving sufficient volume in latissimus dorsi flap breast reconstruction with immediate fat grafting.

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 .

"Fasting: An Effective Preconditioning Method to Increase Fat Graft Survival"

BACKGROUND

Most preconditioning techniques before fat grafting require external manipulation. Since nutrition is the main factor maintaining the balance of lipogenesis and lipolysis, we hypothesized that fasting before undergoing autologous fat grafting may increase lipolysis and reduce adipocyte size, thereby improving the fat graft survival rate.

METHODS

C57BL/6 mice were divided into 24 h starved or fed groups. Adipose tissue lipolysis, adipogenesis, and angiogenesis-related gene expression, in fat from both groups, were analyzed. The volume and weight of the grafted fat at 4-8 weeks postoperatively were measured using micro-computed tomography. Immunohistochemistry staining and mRNA expression analysis were also performed to evaluate the effect of fasting on fat graft survival.

RESULTS

Fasting decreased adipocyte size by inducing adipose tissue lipolysis. Adipogenesis-related genes were remarkably downregulated while lipolysis-related genes and angiogenesis inducer genes were significantly upregulated in the starved adipose tissue. The mice grafted with the fat from the 24 h starved group had approximately 20% larger volumes and considerably heavier weights than those from the fed group. Increased viable adipocytes and vessels, and reduced macrophages in the fat grafts obtained from the 24 h starved group were also observed.

CONCLUSIONS

Fasting for 24 h before harvesting fat increased the retention volume of fat graft by increasing angiogenesis via VEGF induction. Therefore, fasting would be a novel and reliable preconditioning strategy to improve graft survival in autologous fat grafting.

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.

The Effects of Lipoaspirate-Derived Fibrous Tissue on Survival Quality and Mechanical Property of Fat Grafts

BACKGROUND

Fibrous connective tissue (referred to as fiber) in lipoaspirates would be discarded before lipotransfer in case of cannula blockage. However, the fiber contains extracellular matrix which provide structure support and is rich in stromal vascular fractions (SVFs). Removal of the fiber might theoretically affect the survival quality and mechanical properties of fat grafts. But there is few evidence in vivo and vitro about how the fiber affects the fat grafts.

OBJECTIVE

To assess the effect of fibers on the survival quality and mechanical property of fat grafts.

METHODS

The SVFs in both fat and fiber were obtained by collagenase digestion for cells counting and comparison. Three groups were designed according to the different proportions of fat and fiber: the fat group (100% fat), the mixed group (50% fat, 50% fiber in volume ratio), and the fiber group (100% fiber). Three groups of grafts were transplanted in vivo to evaluate the differences in volume retention rate, histological characteristics and mechanical properties.

RESULTS

The amount of SVF cells in fibers (3.47 ± 1.49 × 104 cells/mL) was significantly lower than that in fat (12.3 ± 4.95 × 104 cells/mL) (P < 0.05). Grafts in the mixed group and the fiber group showed an increase of volume retention at week 4, but the fiber content showed no significant effects on the volume retention of grafts in three groups at week 12. Elasticity modulus of grafts in the fat group was higher than that in the fiber group and the mixed group at week 4 and 8, the fiber content showed no significant effects on the elasticity modulus of grafts in three groups at week 12. The addition of the fiber reduced the inflammation, cysts, fibrosis, and capillaries density of the grafts.

CONCLUSIONS

There were few SVF cells in the fiber. When it was mixed with fat in different proportions and transplanted in vivo, the content of fiber showed no significantly different effects on the long-term volume retention and mechanical property of fat grafts. Due to the risk of blockage, it is recommended to discard the fiber in lipoaspirates.

Photobiomodulation with polychromatic light (600-1200 nm) improves fat graft survival by increasing adipocyte viability, neovascularization, and reducing inflammation in a rat model

OBJECTIVES

Unpredictability with the final volume and viability of the graft are the major concerns in fat grafting. An experimental study was conducted to increase graft retention using photobiomodulation (PBM) with polychromatic light in near-infrared region (600-1200 nm) by utilizing its stimulatory effects on angiogenesis, neovascularization, adipocyte viability, and anti-inflammatory properties.

METHODS

A total of 24 rats were divided into four groups (n = 6) according to the applied polychromatic light protocol to the recipient site (none, before fat transfer, after fat transfer, and combined). In all groups, inguinal fat pad was excised, measured for volume and weight, and transferred to the dorsum of the rat. At the end of the experiment, fat grafts were harvested from the recipient site for volume and weight measurements, histological, and immunohistochemical evaluation.

RESULTS

Intergroup comparison revealed that fat graft retention regarding weight and volume, was significantly superior in Group IV (p = 0.049 and p = 0.043, respectively), which polychromatic light was applied both before and after transfer of the graft. Hematoxylin-eosin and Masson's trichrome stained sections showed absence of necrosis, fibrosis, inflammation, cyst formation, and increased vascularization of both inner and outer zones of the grafts in Group IV. Also, immunohistochemical staining scores for perilipin (indicator for adipocyte viability), CD31 and VEGF (indicators for angiogenesis and neovascularization) were significantly higher (p < 0.001). Ki67 scores were significantly lower in this group because of anti-inflammatory environment (p < 0.001).

CONCLUSIONS

Application of PBM to the recipient site before and after fat transfer improved outcomes in rats at 56 day after fat grafting by means of volume retention, increased neovascularization and adipocyte viability and reduced necrosis, fibrosis and inflammation.

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.

Long-Term Effects of Platelet-Rich Fibrin on Fat Graft Survival and Their Optimal Mixing Ratio

BACKGROUND

Platelet-rich fibrin (PRF) can promote fat graft survival, but the reported mixing ratio of PRF to fat ranges from 1:25 to 1:2, lacking a clear standard for clinical application.

OBJECTIVES

The authors sought to explore the long-term effects of PRF on grafted fat and their optimal mixing ratio.

METHODS

Nude mice were randomly divided into a control group (receiving subcutaneous injection of fat granules) and 4 PRF groups (receiving subcutaneous injection of PRF and fat granules at volume ratios of 1:5, 1:10, 1:15, and 1:20, respectively). The graft samples (n = 12) were obtained in weeks 4, 8, and 12 to (1) calculate retention rates; (2) evaluate gene and protein expression of vascular endothelial growth factor A (VEGF-A), peroxisome proliferator-activated receptor-γ (PPAR-γ), type I collagen A1 (COL1-A1), and B-cell lymphoma-2 associated X protein (BAX); (3) perform hematoxylin and eosin, Masson's trichrome, α-smooth muscle action, and periplipin-1 stainings; and (4) count the microvessels and viable adipocytes.

RESULTS

Compared with the control group, PRF groups had higher retention rates, a higher gene/protein expression of VEGF-A, a lower gene/protein expression of COL1-A1 and BAX, less fibrosis, and more microvessels and viable adipocytes. Group 1:10 was superior to other groups in terms of retention rates and other evaluation indexes. The expression of PPAR-γ did not significantly differ among groups.

CONCLUSIONS

PRF may not play a long-term effect on adipogenesis, but it can still promote fat graft survival through facilitating vascularization, regulating collagen production, and inhibiting apoptosis. PRF can achieve the best promoting effect when the mixing ratio of PRF to fat is 1:10, which is recommended as the optimal ratio for clinical application.

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.

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.

Platelet-Rich Fibrin Improves Fat Graft Survival Possibly by Promoting Angiogenesis and Adipogenesis, Inhibiting Apoptosis, and Regulating Collagen Production

BACKGROUND

Platelet-rich fibrin (PRF) can promote fat graft survival, but limited data are currently available, and the underlying mechanism of this effect has not yet been explained.

OBJECTIVES

The aim of this study was to explore the mechanism by which PRF promotes fat graft survival, from the aspects of angiogenesis, adipogenesis, cellular apoptosis, and collagen production.

METHODS

Nude mice were randomly assigned to a PRF group (subcutaneously injected with PRF and fat in the ratio of 1:5 by volume) and a control group (subcutaneously injected with normal saline and fat in the ratio of 1:5 by volume). On days 0, 3, 7, 14, 21, and 28 after transplantation, graft samples (n = 12) were obtained for quantification of target growth factors. In weeks 1, 2, 3, and 4 after transplantation, graft samples (n = 12) were obtained for the following evaluations. The volume and weight retention rates were calculated; gene and protein expression of vascular endothelial growth factor A (VEGF-A), peroxisome proliferator-activated receptor γ (PPAR-γ), COL1-A1, and BAX were evaluated; hematoxylin & eosin staining, Masson's trichrome staining, α smooth muscle actin staining, and perilipin-1 staining were performed to evaluate graft survival.

RESULTS

After transplantation, the concentrations of growth factors produced by the fat increased to varying degrees, and the addition of PRF made these concentration changes ever greater. Compared with the control group, the PRF group had a higher volume and weight retention rate, a higher expression level of VEGF-A and PPAR-γ, a lower expression level of COL1-A1 and BAX, a higher vessel density, less fibrosis, and more viable adipocytes.

CONCLUSIONS

PRF can promote autocrine function of the grafted fat to produce more growth factors. It greatly increased fat retention rate, possibly by promoting vascularization and adipogenic differentiation, inhibiting cellular apoptosis, and regulating collagen production.

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.

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.

The Role of Platelet Concentrates in Facial Fat Grafting

Autologous fat grafting is increasingly being used as a method for the repair of facial soft tissue defects and facial rejuvenation, given its low risk of adverse effects and high efficacy. However, the unpredictability of graft retention is a limitation of this procedure. In addition, there is no standard procedure to date for autologous fat grafting. Different methods have been developed to increase the retention of grafted fat. For instance, platelet concentrates have been used to directly deliver bioactive factors to grafted fat. Platelet concentrates also provide incidental therapeutic benefits by enhancing the persistence of fat grafted in the face via the release of growth factors and cytokines. In this review, we describe current strategies for improving the survival of facial fat grafts, mainly focusing on the application of growth factors/cytokines and platelet concentrates to fat grafting.

A Study of the Effect of Platelet-Rich Plasma on Outcomes After Aspirated Human Fat Grafting With Experimental Design

INTRODUCTION

Over the past decade, some studies have focused on whether platelet-rich plasma (PRP) can promote the survival of fat grafts after transplantation. However, the results of these studies have been controversial because of the variations in research methods and assessment methodologies.

METHODS

In this study, the authors aspirated fat particles from the abdomen of a healthy woman, mixed them with PRP, and injected them into the backs of nude mice subcutaneously, which simulates the clinical model. The control group was designed to mix aspired fat with normal saline. The fat grafts were removed 10 weeks after transplantation, stained with hematoxylin and eosin, and sliced into pathological sections, which were subsequently scanned and analyzed using the Digital Slide Scanning System (PRECICE, Beijing, China).

RESULTS

The total area of the graft section and the necrotic adipose tissue area in the control group were significantly larger than that in the PRP group. The fibrosis tissue area in the PRP group was significantly larger than that in the control group. There were no statistically significant differences in the viable adipocyte area, the cyst area, and the mature blood vessel number between the PRP and control groups.

CONCLUSION

In this study, PRP did not cause an increase in the number of viable adipocytes; however, it did increase the amount of inflammation, which promoted necrotic tissue absorption and the proliferation of granulation tissue. Further research, including research on normalization of fat preparation and grafting, unification of the PRP preparation and application scheme, and optimization of histological measurement and analysis methods, is needed to assess the effect of PRP on fat grafting.

Effects of Platelet-Rich Plasma on Fat and Nanofat Survival: An Experimental Study on Mice

BACKGROUND

Nanofat and fat graft survival is an important clinical problem. The authors of this study investigated whether PRP has an impact on fat and nanofat graft survival and vascularization in a mouse model.

MATERIALS AND METHODS

Fat was harvested from a 50-year-old healthy woman by vacuum suction, and nanofat was obtained by emulsification and centrifugation procedures. PRP was collected after two rounds of centrifugation from an autologous blood sample. Twenty male nude mice were divided into four treatment groups: PRP/nanofat, PRP/fat, saline/nanofat and saline/fat. After 1 month and 3 months, the grafts were extracted and weighed. The microstructure of the fat and nanofat was examined with a scanning electron microscope. HE and immunohistochemical staining was applied to observe neovascularization. Western blot analysis was used to analyse the expression of CD31 and VEGF.

RESULTS

In fat tissue, fat cells had normal connections; the fat structure was complete and fibre networks were visible. In nanofat, the extracellular matrix vascular components were visible and their structures were intact. At 1 month and 3 months, the graft weights in the PRP/fat group were significantly higher than those in the other groups. Further, a higher degree of neovascularization was observed in the PRP/nanofat group, and the expression of CD31 and VEGF in the PRP/nanofat group was higher than that in the other groups.

CONCLUSION

PRP can promote nanofat and fat graft survival and vascularization.

NO LEVEL ASSIGNED

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 .

Utility of Adipocyte Fractions in Fat Grafting in an Athymic Rat Model

BACKGROUND

Multiple processing and handling methods of autologous fat yield to variations in graft retention and viability, which results in unpredictable clinical outcomes.

OBJECTIVES

This study aims to understand the skin effects of fat graft preparations that contain a varying ratio of free-lipid and stem-cell-bearing stromal vascular fractions (SVF).

METHODS

Lipoaspirates from consenting patients were processed into emulsified fat and then SVF and adipocyte fractions (free-lipid). SVF enriched with 0%, 5%, and 15% free-lipid were grafted along the dorsum of athymic rats. The xenografts were collected 45 days after grafting and then prepped for immunostaining.

RESULTS

Xenografts resulted in viable tissue mass under the panniculus carnosus of rats as confirmed with human specific markers. A low percentage of human cells was also detected in the lower reticular dermis. Although grafts with SVF formed adipocytes of normal architecture, grafts formed with free-lipid alone resulted in large lipid vacuoles in varying sizes. Among graft preparations, SVF with 10% free-lipid resulted in much-developed adipocyte architecture with collagen and elastin. Compared with SVF alone grafts, SVF with free-lipid had higher CD44 expression, suggesting a localized immune response of adipocytes.

CONCLUSIONS

Current studies suggest that SVF enriched with approximately 10% free-lipid provides the best conditions for fat graft differentiation into viable fat tissue formation as well as collagen and elastin production to provide mechanical support for overlaying skin in an athymic rat model. Additionally, application of this therapeutic modality in a simple clinical setting may offer a practical way to concentrate SVF with free-lipid in a small volume for the improvement of clinical defects.

LEVEL OF EVIDENCE 5

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.

Hair follicle growth by stromal vascular fraction-enhanced adipose transplantation in baldness

Great interest remains in finding new and emerging therapies for the treatment of male and female pattern hair loss. The autologous fat grafting technique is >100 years old, with a recent and dramatic increase in clinical experience over the past 10-15 years. Recently, in 2001, Zuk et al published the presence of adipose-derived stem cells, and abundant research has shown that adipose is a complex, biological active, and important tissue. Festa et al, in 2011, reported that adipocyte lineage cells support the stem cell niche and help drive the complex hair growth cycle. Adipose-derived regenerative cells (also known as stromal vascular fraction [SVF]) is a heterogeneous group of noncultured cells that can be reliably extracted from adipose by using automated systems, and these cells work largely by paracrine mechanisms to support adipocyte viability. While, today, autologous fat is transplanted primarily for esthetic and reconstructive volume, surgeons have previously reported positive skin and hair changes posttransplantation. This follicular regenerative approach is intriguing and raises the possibility that one can drive or restore the hair cycle in male and female pattern baldness by stimulating the niche with autologous fat enriched with SVF. In this first of a kind patient series, the authors report on the safety, tolerability, and quantitative, as well as photographic changes, in a group of patients with early genetic alopecia treated with subcutaneous scalp injection of enriched adipose tissue. The findings suggest that scalp stem cell-enriched fat grafting may represent a promising alternative approach to treating baldness in men and women.

Improvement of Fat Graft Survival with Autologous Bone Marrow Aspirate and Bone Marrow Concentrate: A One-Step Method

BACKGROUND

Stem cells have proven to be beneficial to fat graft survival, but a one-step method of cell-assisted lipotransfer is still missing. In the present work, the authors improved the fat graft survival using bone marrow aspirate and bone marrow concentrate, to ensure that both liposuction and cell-assisted lipotransfer were included in the same procedure.

METHODS

Bone marrow aspirate was collected from the iliac crest of the rabbits. Bone marrow concentrate was obtained using density gradient centrifugation and labeled with PKH26 fluorescent cell linker. Rabbits were divided into three groups: group A, bone marrow aspirate; group B, bone marrow concentrate; and group C, phosphate-buffered saline buffer as a blank control. The implanted mixture contained 1.5 ml of adipose granule and 1 ml of bone marrow aspirate or bone marrow concentrate. The rabbits were subjected to fluorescence imaging in vivo at four time points. Grafts were harvested and analyzed at 4 weeks and 12 weeks after fat grafting.

RESULTS

Bone marrow cell fluorescence signals were observed in the rabbits' injection regions during a follow-up of 12 weeks. The fat grafts of group A and B showed a better weight and volume retention, living quality, adipocyte viability, and angiogenesis after transplantation. The results of living tissue imaging also showed that the implanted bone marrow cells could contribute to fat graft survival by multilineage differentiation and could also contribute to adipogenesis and angiogenesis.

CONCLUSION

Both bone marrow aspirate and bone marrow concentrate improved the survival and angiogenesis of grafted fat tissue.

Morphological features of cell death and tissue remolding of fat grafts

BACKGROUND

Fat tissue graft has been commonly used for soft tissue augmentation. However, the mechanisms underlying the maintenance of graft volume and weight are still unclear. As morphological features provide direct evidences for cell death and survival, we aimed to investigate the fate of grafted adipocytes and the dynamic changes in the remodeling of adipose tissues by transmission electron microscopy technique.

METHODS

The unilateral inguinal fat pad of C57BL/6J mice was autografted to the dorsa of the mice. Perilipin expression and morphological changes were investigated by immunohistochemistry staining and transmission electron microscopy, respectively, in grafted tissues collected at posttransplantation days 0, 1, 3, 5, 7, 14, and 30.

RESULTS

Transmission electron microscopy analysis revealed that most adipocytes in grafts showed traits of cell death on postgrafting day 3. Multilocular adipocytes with naive nuclei were observed as early as day 5 and a larger number of multilocular adipocytes were found on day 14. Perilipin immunostaining revealed that only some adipocytes located in the margin of grafts survived through the ischemic injury. New adipocytes were visualized at the periphery of the grafts, although the scope of viable adipocyte zonal areas increased from day 5 to day 30.

CONCLUSIONS

The results provide ultrastructural evidences associated with the remodeling dynamics of adipose tissue grafts. It is suggested that maximized volume of graft should be obtained through promoting regeneration other than improving survival of grafted adipose tissues.

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.

Coimplanted endothelial cells improve adipose tissue grafts' survival by increasing vascularization

BACKGROUND

With goal of improving fat graft survival, many studies have focused on supplementing cells in the graft fat. In these studies, enhanced vascularization is considered the most important mechanism for the improved graft survival. Endothelial cells (ECs) are essential in vessel formation of the vascularization. Therefore, in this study, we coimplanted ECs with adipose tissue to investigate whether the ECs can enhance graft survival in a cell concentration-dependent manner.

METHODS

Endothelial cells were isolated from stromal vascular fraction derived from human liposuction aspirates, and the EC characteristics were confirmed by CD31 immunofluorescence staining, measuring acetylated low-density lipoprotein uptake, and observing the formation of capillary-like tubular structures in Matrigel. During the animal experiment, the isolated ECs were labeled, then added to 0.5-mL fat grafts at different numbers (0.5 × 10(6), 1 × 10(6), 2 × 10(6), and 4 × 10(6) cells) before subcutaneous implantation in nude mice. Grafts were harvested at 1 week, 1 month, and 2 months after -transplantation, and graft survival and vascularization were evaluated based on weight measurements, histological assessment, and vascular gene expression.

RESULTS

Stromal vascular fraction-derived vascular cells exhibited typical EC characteristics. The observed differences in explanted graft weight, vessel density, vascular gene expression, and cell tracking result indicated that coimplantation with ECs accelerated vascularization that increased graft survival in a concentration-dependent manner. Over the experimental period, fat grafts implanted with 4 × 10(6) ECs showed no weight loss and the greatest increases in measures of vascularization.

CONCLUSIONS

Endothelial cells can effectively enhance vascularization in fat grafts, and higher EC concentrations (eg, 4 × 10(6) ECs/0.5 mL adipose tissue) may best support graft survival.

Traditional Chinese Medicine: Salvia miltiorrhiza Enhances Survival Rate of Autologous Adipose Tissue Transplantation in Rabbit Model

OBJECTIVE

This study aimed to explore the influence of traditional Chinese medicines: Salvia miltiorrhiza on the survival of auto-transplantation of adipose tissue in a rabbit model.

METHODS

Minced adipose tissue harvested from the scapular region was transplanted into the dorsum of the ears of New Zealand rabbits. The experimental groups were intra-peritoneally injected with S. miltiorrhiza for a total 4 weeks. The rabbits in control group were intra-peritoneally injected with normal saline. Plasma VEGF levels were assayed at week 1, 2, 4, 6, and 8 after fat tissue auto-transplantation in the dorsum of rabbit ears. Graft samples were collected and measured at week 2, 4, and 12. Survival rates were calculated, and histologic morphology was evaluated. The expression of CD31 was detected by means of immune-histochemical staining to observe neo-vascularization of the auto-transplanted fat tissue. Perilipin was detected by means of immune-histochemical staining to observe the survival of fat cells.

RESULTS

At 12 weeks, the survival rates in the experimental group were statistically greater than that in the control group, respectively (p < 0.05). Plasma levels of VEGF in the experimental group at different time points were significantly higher than that in the control group (p < 0.05). Histologically, grafts in the experimental group showed better survival of adipocytes and neo-vascularization. By perilipin immuno-histochemical staining, the experimental group demonstrated better adipocyte survival.

CONCLUSIONS

In the rabbit model, S. miltiorrhiza can promote the neo-vascularization of adipose tissue grafts and significantly improves the survival rate of auto-transplanted adipose tissue.

NO LEVEL ASSIGNED

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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.

Brown adipose tissue and novel therapeutic approaches to treat metabolic disorders

In humans, 2 functionally different types of adipose tissue coexist: white adipose tissue (WAT) and brown adipose tissue (BAT). WAT is involved in energy storage, whereas BAT is involved in energy expenditure. Increased amounts of WAT may contribute to the development of metabolic disorders, such as obesity-associated type 2 diabetes mellitus and cardiovascular diseases. In contrast, the thermogenic function of BAT allows high consumption of fatty acids because of the activity of uncoupling protein 1 in the internal mitochondrial membrane. Interestingly, obesity reduction and insulin sensitization have been achieved by BAT activation-regeneration in animal models. This review describes the origin, function, and differentiation mechanisms of BAT to identify new therapeutic strategies for the treatment of metabolic disorders related to obesity. On the basis of the animal studies, novel approaches for BAT regeneration combining stem cells from the adipose tissue with active components, such as melatonin, may have potential for the treatment of metabolic disorders in humans.

Alternatively activated M2 macrophages improve autologous Fat Graft survival in a mouse model through induction of angiogenesis

BACKGROUND

Variability in graft retention with subsequent undercorrection remains a significant limitation of autologous fat grafting. The authors evaluated whether graft retention in a mouse model could be improved via graft supplementation with alternatively activated M2 macrophages, cells known to play a critical role in tissue repair.

METHODS

Grafts from C57BL/6 mouse inguinal fat pads were supplemented with M2 macrophages generated by intraperitoneal Brewer's thioglycollate injection and in vitro culture. Grafts with saline or M2 macrophages were injected under recipient mouse scalps and assessed by serial micro-computed tomographic analysis. Explanted grafts underwent immunohistochemical and flow cytometric analyses. M2 culture supernatants were added to stromal vascular fraction adipose-derived stem cells to assess adipogenic gene expression induction.

RESULTS

One month after graft injection, no significant difference was noted between M2 macrophage-supplemented (105 ± 7.0 mm) and control graft volumes (72 ± 22 mm). By 3 months after injection, M2 macrophage-supplemented grafts remained stable, whereas controls experienced further volume loss (103 ± 8 mm versus 39.4 ± 15 mm; p = 0.015). Presence of macrophages in supplemented grafts was confirmed by flow cytometry. M2 macrophage-supplemented grafts exhibited a 157 percent increase in vascular density compared with controls (p < 0.05). Induction of adipogenic C/EBPα gene expression was observed with M2 supernatants addition to stromal vascular fraction adipose-derived stem cells.

CONCLUSIONS

M2 macrophages improve autologous fat graft volume retention by stimulating angiogenesis. These findings provide proof-of-principle for development of fat grafting techniques that harness reparative properties of M2 macrophages.

Improvement of the survival of human autologous fat transplantation by adipose-derived stem-cells-assisted lipotransfer combined with bFGF

Adipose-derived stem cells (ASCs) transplanted along with autologous adipose tissue may improve fat graft survival; however, the efficacy of ASCs has been diluted by low vascularization. This study was designed to test the hypothesis that basic fibroblast growth factor (bFGF) may improve the effects of ASCs because it owns the property to boost angiogenesis. In the present study, human fat tissues were mixed with ASCs, ASCs plus 100 U bFGF, or medium as the control and then injected subcutaneously into immunologically compromised nude mice for 12 weeks. Our findings demonstrated that mixture with the ASCs significantly increased the weight and volume of the fat grafts compared to control grafts, and histological analysis revealed that both ASCs and ASCs plus bFGF grafts consisted predominantly of adipose tissue and had significantly less fibrosis but greater microvascular density compared with control and also grafts mixed with ASCs had a high expression of angiogenic factors. More importantly, the bFGF treated fat grafts shown elevate in survival, vascularization, and angiogenic factors expression when compared with the grafts that received ASCs alone. These results indicated that bFGF together with ASCs can enhance the efficacy of autologous fat transplantation and increase blood vessel generation involved in the benefits from bFGF.

Experimental and clinical methods used for fat volume maintenance after autologous fat grafting

Management of soft tissue deficits resulting from congenital abnormalities, trauma, systemic disease, and tumors is a particularly challenging field of plastic and reconstructive surgery. Fat grafting, a technique traditionally used in the correction of facial asymmetry, is commonly seen in aesthetic procedures which use the grafted fat for soft tissue augmentation and recontouring. Despite its widespread use in reconstruction and aesthetic surgery, therapeutic modalities applied in fat grafting are crude and the results of this intervention are unpredictable. The aim of this review was to present the most recent evidence regarding experimental studies and designs which confirmed or disproved fat volume expansion or fat maintenance after autologous fat grafting.

Tanshinone IIA pretreatment protects free flaps against hypoxic injury by upregulating stem cell-related biomarkers in epithelial skin cells

Background

Partial or total flap necrosis after flap transplantation is sometimes encountered in reconstructive surgery, often as a result of a period of hypoxia that exceeds the tolerance of the flap tissue. The purpose of this study was to determine whether Tanshinone IIA (TSA) pretreatment can protect flap tissue against hypoxic injury and improve its viability.

Methods

Primary epithelial cells isolated from the dorsal skin of mice were pretreated with TSA for 2 weeks. Cell Counting Kit-8 and Trypan Blue assays were carried out to examine the proliferation of TSA-pretreated cells after exposure to cobalt chloride. Polymerase chain reaction and western blot analysis were used to assess the expression of β-catenin, vascular endothelial growth factor (VEGF), sex determining region Y-box 2 (SOX2), OCT4 (also known as POU domain class 5 transcription factor 1), Nanog, and glycogen synthase kinase-3 beta (GSK-3β) in TSA-treated cells. In other experiments, after mice were pretreated with TSA for 2 weeks, a reproducible ischemic flap model was implemented, and the area of surviving tissue in the transplanted flaps was measured. Immunohistochemistry was conducted to examine Wnt signaling as well as stem cell- and angiogenesis-related biomarkers in epithelial tissue in vivo.

Results

Epidermal cells, pretreated with TSA, showed enhanced resistance to hypoxia. Activation of the Wnt signaling pathway in TSA-pretreated cells was characterized by the upregulation of β-catenin and the downregulation of GSK-3β. The expression of SOX2, Nanog, and OCT4 were also higher in TSA-pretreated epithelial cells than in control cells. In the reproducible ischemic flap model, pretreatment with TSA enhanced resistance to hypoxia and increased the area of surviving tissue in transplanted flaps. The expression of Wnt signaling pathway components, stem-cell related biomarkers, and VEGF and CD34, which are involved in the regeneration of blood vessels, was also upregulated in TSA-pretreated flap tissue.

Conclusions

TSA pretreatment protects free flaps against hypoxic injury and increases the area of surviving tissue by activating Wnt signaling and upregulating stem cell-related biomarkers.

Improvement in the repair of defects in maxillofacial soft tissue in irradiated minipigs by a mixture of adipose-derived stem cells and platelet-rich fibrin

To find out if adipose-derived stem cells (ASC) and platelet-rich fibrin (PRF), alone or combined, had any effect on the repair of maxillofacial soft tissue defects in irradiated minipigs, ASC were isolated, characterised, and expanded. Twenty female minipigs, the right parotid glands of which had been irradiated, were randomly divided into 4 groups of 5 each: those in the first group were injected with both ASC and PRF (combined group), the second group was injected with ASC alone (ASC group), the third group with PRF alone (PRF group), and the fourth group with phosphate buffer saline (PBS) (control group). Six months after the last injection, the size and depth of each defect were assessed, and subcutaneous tissues were harvested, stained with haematoxylin and eosin, and examined immunohistologically and for apoptosis. Expanded cells were successfully isolated and identified. Six months after injection the defects in the 3 treated groups were significantly smaller (p<0.001) and shallower (p<0.001) than those in the control group. Those in the combined group were the smallest and shallowest. Haematoxylin and eosin showed that the 3 treated groups contained more subcutaneous adipose tissue than the control group, and also had significantly greater vascular density (p<0.001) and fewer apoptotic cells (p<0.001). Both ASC and PRF facilitate the repair of defects in maxillofacial soft tissue in irradiated minipigs, and their combined use is more effective than their use as single agents.