Effect of external volume expansion on the survival of fat grafts

External Volume Expansion: Timing and Effects on the Rate of Fat Graft Retention in BALB/c Nude Mice

BACKGROUND/AIM

Fat grafting has been widely used for soft-tissue augmentation. External volume expansion (EVE) is a favorable tool for improvement in the rate of fat graft retention. However, few studies have focused on the most appropriate time for its implementation. In this study, BALB/c nude mice were used to investigate the effective time for the implementation of external volume expansion to improve the rate of fat retention.

MATERIALS AND METHODS

Sixteen mice were divided into four groups, and EVE was performed at different time points before or both before and after fat grafting. Fat tissue from a human donor was injected into the mice following EVE. Visual assessment, micro-computed tomography analysis, and histopathological evaluation were used to assess fat retention.

RESULTS

After 10 weeks, the group that underwent EVE 5 days before fat grafting demonstrated a significantly higher preserved fat volume, as determined by micro-computed tomography (p<0.05). Moreover, the group that received additional EVE after fat grafting exhibited a higher retention rate compared to the groups receiving EVE only before grafting (p<0.05). Histopathological analysis indicated that swelling, edema, and inflammation were more pronounced in the group with EVE immediately before grafting, while angiogenesis and lipogenesis were more active in the group with additional EVE after grafting.

CONCLUSION

EVE is a safe and effective approach for improving the rate of fat graft retentions. Furthermore, the timing of external tissue expansion plays a crucial role in fat retention. Based on our animal study, performing EVE immediately before and after fat grafting may be an effective strategy for enhancing the rate of fat graft retentions.

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.

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.

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.

Tissue-Engineered Soft-Tissue Reconstruction Using Noninvasive Mechanical Preconditioning and a Shelf-Ready Allograft Adipose Matrix

BACKGROUND

Adipose tissue defects leading to severe functional (disability) and morphologic (disfigurement) morbidity are often treated in plastic surgery with fat grafting, which can be limited by resorption, necrosis, and cyst formation. This study aimed to assess whether adipose scaffolds could provide an environment for in situ autologous fat grafting, and to study whether adipose cell migration and proliferation (adipogenesis) within scaffolds could be enhanced by preliminarily increasing the vascularity (preconditioning) of the surrounding tissue receiving the scaffolds.

METHODS

Using an established rodent model of subcutaneous tissue/scaffold grafting, the authors tested the potential of a human-derived, shelf-ready, injectable, decellularized allograft adipose matrix to reconstruct soft-tissue defects when used in combination with noninvasive mechanical (suction-induced) skin preconditioning.

RESULTS

Combined use of the allograft adipose matrix and noninvasive skin preconditioning significantly improved long-term volume retention (50 to 80 percent higher at a 12-week follow-up) and histologic quality of reconstructed tissues compared with standard of care (autologous adipose grafts). The components of the allograft adipose matrix supported adipogenesis and angiogenesis. Combining the allograft adipose matrix with living adipose grafts mitigated negative outcomes (lower long-term volume retention, higher presence of cystic-like areas).

CONCLUSIONS

This study suggests that the synergistic use of the allograft adipose matrix and noninvasive tissue preconditioning provides an effective solution for improving fat grafting. These strategies can easily be tested in clinical trials and could establish the basis for a novel therapeutic paradigm in reconstructive surgery.

Recent Advances on the Application of Negative Pressure External Volume Expansion in Breast Plastic Surgery

BACKGROUND

External volume expansion (EVE) has been effectively applied as an assistance to fat transplantation on breast plastic surgery. Many indicators and refinements have been made in clinical practice; meanwhile, the related mechanism and more optimized preclinical model also have been explored in experimental studies.

METHODS

A literature search was conducted using PubMed with the keywords: EVE, negative pressure, breast enlargement, breast augmentation, breast reconstruction, breast plastic surgery and breast aesthetic surgery. Studies dealing with the clinical and preclinical aspects of the subject and also in vitro experiments related to a certain period of negative pressure and adipose-derived cells were selected, and those only focused on negative pressure were excluded.

RESULTS

The indications, contraindications, complications and treatments of EVE in clinical practice were summarized. The experimental studies were mainly classified into two groups (mechanical and translational) according to their contents. Mechanical studies were further divided into inference experimental validation phase studies. For the experimental validation phase, EVE was verified to promote angiogenesis, while it still remained controversial whether it would enhance adipogenesis and cell proliferation.

CONCLUSION

Clinically, our experience is on the stage of exploration, and there is a lack of standardized guidelines on its clinical application. Experimentally, the previous studies showed some subtly different views on the functional mechanisms. However, it is not enough to regulate the clinical practice yet. Therefore, related basic studies and long-term clinical follow-up are needed.

LEVEL OF EVIDENCE IV

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