Stromal vascular fraction cells plus sustained release VEGF/Ang-1-PLGA microspheres improve fat graft survival in mice

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE III

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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.

Pluronic F-127 Hydrogel Loaded with Human Adipose-Derived Stem Cell-Derived Exosomes Improve Fat Graft Survival via HIF-1α-Mediated Enhancement of Angiogenesis

Purpose

Autologous fat grafting is playing an increasingly important role in plastic surgery. However, high absorption and low survival of autologous fat grafts limit their clinical application. This study aimed to investigate whether human adipose-derived stem cell-derived exosomes (hASC-Exos) encapsulated in a PF-127 hydrogel can improve the survival of autologous fat grafts and to elucidate the underlying mechanisms.

Patients and Methods

Exosomes were isolated from hASCs and identified using transmission electron microscopy, nanoparticle tracking analysis and Western blotting. We performed functional assays in vitro to assess the effect of hASC-Exos on proliferation, migration, and tube formation as well as their regulatory role in the HIF-1α/VEGF signaling pathway. hASC-Exos encapsulated in the PF-127 hydrogel were used as an in vivo autologous fat graft model. The effects of the PF-127 hydrogel/hASC-Exos and the role of the HIF-1α/VEGF signaling pathway in promoting angiogenesis in an autologous fat grafting model were assessed.

Results

hASC-Exos were taken up by human umbilical vein endothelial cells and enhanced their proliferation, migration, and tubule formation in vitro. The effects of hASC-Exos on promoting angiogenesis were mediated by the HIF-1α/VEGF signaling pathway. Moreover, we fabricated a PF-127 hydrogel for the sustained release of hASC-Exos, and in vivo results showed that hASC-Exos encapsulated in PF-127 hydrogel improved the survival of autologous fat grafts.

Conclusion

Our findings indicated that hASC-Exos encapsulated in PF-127 hydrogel serve as a key regulator of angiogenesis by activating the HIF-1α/VEGF signaling pathway and provide a promising strategy for autologous fat grafting treatment.

Three-dimensional spheroid formation of adipose-derived stem cells improves the survival of fat transplantation by enhance their therapeutic effect

Adipose-derived stem cells (ADSCs) have important applications in basic research, especially in fat transplantation. Some studies have found that three-dimensional (3D) spheroids formed by mesenchymal stem cells have enhanced therapeutic potential. However, the fundamental basics of this effect are still being discussed. ADSCs were harvested from subcutaneous adipose tissues and 3D spheroids were formed by the automatic aggregation of ADSCs in a non-adhesive 6-well plate. Oxygen glucose deprivation (OGD) was used to simulate the transplantation microenvironment. We found that 3D culture of ADSCs triggered cell autophagy. After inhibiting autophagy by Chloroquine, the rates of apoptosis were increased. When the 3D ADSC-spheroids were re-planked, the number of senescent ADSCs decreased, and the proliferation ability was promoted. In addition, there were more cytokines secreted by 3D ADSC-spheroids including VEGF, IGF-1, and TGF-β. After adding the conditioned medium with human umbilical vein endothelial cells (HUVECs), 3D ADSC-spheroids were more likely to promote migration, and tube formation, stimulating the formation of new blood vessels. Fat grafting experiments in nude mice also showed that 3D ADSC-spheroids enhanced survival and neovascularization of fat grafts. These results suggested that 3D spheroids culturing of ADSCs can increase the therapeutic potential in fat transplantation.

Improving Autologous Fat Grafting in Regenerative Surgery through Stem Cell-Assisted Lipotransfer

Autologous fat transplantation -i.e., lipofilling- has become a promising and popular technique in aesthetic and reconstructive surgery with several application such as breast reconstruction, facial and hand rejuvenation. However, the use of this technology is still limited due to an unpredictable and low graft survival rate (which ranges from 25%-80%). A systematic literature review was performed by thoroughly searching 12 terms using the PubMed database. The objective of this study is to present the current evidence for the efficacy of adjuvant regenerative strategies and cellular factors, which have been tested to improve fat graft retention. We present the main results (fat retention rate, histological analysis for pre-clinical studies and satisfaction/ complication for clinical studies) obtained from the studies of the three main fat grafting enrichment techniques: platelet-rich plasma (PRP), the stromal vascular fraction (SVF) and adipose-derived stem cells (ADSCs) and discuss the promising role of recent angiogenic cell enrichment that could induce early vascularization of fat graft. All in all, adding stem or progenitor cells to autologous fat transplantation might become a new concept in lipofilling. New preclinical models should be used to find mechanisms able to increase fat retention, assure safety and transfer these technologies to a good manufacturing practice (GMP) compliant facility, to manufacture an advanced therapy medicinal product (ATMP).

MiR-24-3p regulates the differentiation of adipose-derived stem cells toward pericytes and promotes fat grafting vascularization

Adipose-derived stem cells (ADSCs) enhance fat graft survival by promoting neovascularization. The mechanism that promotes ADSCs differentiation toward pericytes was not known. We treated ADSCs with conditional medium (CM) from endothelial cells (ECs) or human recombinant transforming growth factor β (TGF-β) to induce differentiation into pericytes. Pericytes markers, including platelet-derived growth factor receptor β (PDGFRβ), alpha-smooth muscle actin (α-SMA), and desmin, were examined. Pericytes differentiation markers, migration, and their association with ECs were examined in ADSCs transfected with miR-24-3p mimics and inhibitors. Bioinformatics target prediction platforms and luciferase assays were used to investigate whether PDGFRβ was directly targeted by miR-24-3p. In vivo, fat mixed with ADSCs transfected with miR-24-3p mimics or inhibitors was implanted subcutaneously on the lower back region of nude mice. Fat grafts were harvested and analyzed at 2, 4, 6, and 8 weeks. Results showed that endogenous TGF-β derived from CM from EC or human recombinant TGF-β promoted migration, association with ECs, and induced expression of pericyte markers (PDGFRβ, α-SMA, Desmin) in ADSCs. MiR-24-3p directly targeted PDGFRβ in ADSCs by lucifer reporter assays. Inhibition of miR-24-3p promoted pericytes differentiation, migration, and association with ECs in ADSCs. Inhibition of miR-24-3p in ADSCs promoted survival, integrity, adipocyte viability, vascularization, pericytes association with ECs, and reduced fibrosis, whereas overexpression of miR-24-3p in ADSCs yielded the opposite results. Collectively, TGF-β released by ECs induced ADSCs differentiation toward pericytes through miR-24-3p. Downregulation of miR-24-3p in ADSCs induced survival, integrity, adipocyte viability, vascularization, pericytes association with ECs, and reduced fibrosis after fat grafting.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic diseases.

A Short-Term High-Fat Diet Improved the Survival of Fat Grafts in Mice by Promoting Macrophage Infiltration and Angiogenesis

Background: Adipose tissue is an ideal filler material that is widely used for soft tissue defects. But the low survival rate and complications associated with such grafts pose a serious challenge, which limits their clinical application. Adipose tissue is a metabolic diet-responsive tissue; however, the influence of diets on fat grafting remains ambiguous.

Methods: We extracted inguinal fat pads from C57/BL6 male mice, and transplanted them into the dorsal region of recipient mice (0.3 ml). Post-fat-grafting, mice (n = 54) were randomized into three groups, namely normal diet (ND), high carbohydrate diet (HC), and high-fat diet (HF). Structural changes were assessed by histological staining. Lipolysis activity and vascular regeneration of grafts on day 30 were analyzed using real-time polymerase chain reaction, immunofluorescence, and western blotting.

Results: The grafts of mice on HC and HF diets exhibited significantly fewer oil cysts and larger volume retention (0.18 ± 0.01, 0.21 ± 0.01, and 0.25 ± 0.01 ml, for ND, HC, and HF group, respectively, p < 0.05) on day 90. In comparison, grafts for the mice belonging to the HF groups exhibited higher expression of lipolysis-related genes, including adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and carnitine palmitoyltransferase 1 (CPT1), on day 30. Furthermore, increased infiltration of macrophages (F4/80+) and the higher expression of angiogenesis genes were reported in the HF groups.

Conclusion: Altogether, the administration of short-term HF diet remarkably enhanced angiogenesis and improved the quality of fat grafts, which was characterized by fewer oil cysts and higher long-term volume retention. The possible mechanisms may be due to the increased macrophage infiltration, and the promoted angiogenesis in HF grafts.

Acetyl l-carnitine protects adipose-derived stem cells against serum-starvation: regulation on the network composed of reactive oxygen species, autophagy, apoptosis and senescence

Adipose-derived stem cells (ADSCs) play an important role in cell therapy and regenerative medicine. However, local nutritional deficiency often limits therapeutical effect of the transplanted cells. Acetyl l-carnitine (ALC) is a common energy metabolism regulator and free radical scavenger. This study investigated the effect of ALC on ADSCs exposed to severe serum-deprivation and explored the relative machanisms. Treating with 1 mM ALC improved proliferation and alleviated senescence of starved cells, accompanied with reduced reactive oxygen species (ROS) and increased protein expression of SOD1 and catalase. In addition, ALC inhibited apoptosis but increased starvation-induced autophagy, which might be related to the regulation of phases of dissociation of Bcl-2-Beclin1 and Bcl-2-Bax complexes. Evidence obtained by replacing ALC with N-acetylcysteine (N-AC) suggested that ROS might be the central inducer of autophagy, apoptosis and senescence. There was a difference between ALC and N-AC in the protection mechanism, that was, compared with N-AC, ALC maintained autophagy well at the same time as anti-oxidation. Inhibition of autophagy by 3-methyladenine (3-MA) partially offset the protective effect of ALC. However, despite low-level ROS and enhanced autophagy, ALC with high concentration (10 mM) markedly aggravated cell apoptosis and senescence, thus losing cytoprotection and even causing damage.

Autologous decellularized extracellular matrix promotes adipogenic differentiation of adipose derived stem cells in low serum culture system by regulating the ERK1/2-PPARγ pathway

High viability and further adipogenic differentiation of adipose-derived stem cells (ADSCs) are fundamental for engraftment and growth of the transplanted adipose tissue. It has been demonstrated that extracellular matrix (ECM) regulates cell proliferation and differentiation by interacting with ERK1/2 signalling pathway. In this study, we prepared autologous decellularized extracellular matrix (d-ECM) and explored its effect on the proliferation and adipogenic ability of ADSCs in low serum culture. We found that 2% foetal bovine serum (FBS) in growth medium inhibited cell viability and DNA replication, and decreased mRNA and protein levels of PPARγ and C/EPBα compared with 10% FBS. Correspondingly, after 14-days adipogenic induction, cells cultured in 2% FBS possessed lower efficiency of adipogenesis and expressed less adipocyte differentiation markers ADIPOQ and aP2. On the contrary, the d-ECM-coated substrate continuously promoted the expression of PPARγ, and regulated the phosphorylation of ERK1/2 in different manners during differentiation. Pretreatment with ERK1/2 inhibitor PD98059 neutralized the effects of d-ECM, which suggested d-ECM might regulate the adipogenesis of ADSCs through ERK1/2-PPARγ pathway. In addition, d-ECM was revealed to regulate the transcription and expression of stemness-associated genes, such as OCT4, NANOG and SOX2, in the undifferentiated ADSCs, which might be related to the initiation of differentiation.

Substrate coated with autologous decellularized extracellular matrix facilitates in vitro spreading of spheroid from adipose-derived stem cells through regulating ERK1/2-MMP2/9 pathway

Adipose-derived stem cells (ADSCs) are easily available and play an important role in regenerative medicine. In recent years, Cell spheroid models have been in the spotlight because of their various advantages and physiological proximity. Promoting the spreading of ADSCs spheroids may improve the therapeutic effect the transplanted ADSCs. In this study, we prepared autologous decellularized extracellular matrix (d-ECM) and ADSCs spheroids, and investigated in vitro spreading of the spheroids on the d-ECM-coated substrate. In addition, the effect of d-ECM powder (ECM-P) on the aggregation of ADSCs was analyzed in a three-dimensional (3D) culture system. The results showed that d-ECM accelerated the spreading of spheroids, and promoted the migration and proliferation of the surrounding monolayer cells, accompanied by ERK1/2 activation and an increase in the expression of MMP2 and MMP9. In addition, ECM-P facilitated the aggregation of free cells in 3D culture in a concentration-dependent way. The spheroid spreading and cell aggregation were both prevented by ERK1/2 selective inhibitor PD98059. Our data suggest that the d-ECM substrate and its derivant may regulate the transformation between ADSCs spheroids and the monolayer or free cells, and ERK1/2 signalling pathway may be involved in these processes.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE: 4

Vascularization strategies for skin tissue engineering

Lack of proper vascularization after skin trauma causes delayed wound healing. This has sparked the development of various tissue engineering strategies to improve vascularization.