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.

Cyclic High Negative-Pressure External Volume Expansion Reduces Daily Device Application Time With Similar Effects on Recipient Site Preparation in a Murine Model

Introduction: Recipient site preparation using external volume expansion (EVE) increases graft survival in large-volume fat grafting. To improve patient compliance with using the device, we tested a new cyclic high negative-pressure (CHNP) mode that involves 1 h/day at -55 mm Hg, cycled between 1-second negative-pressure activation, followed by a 2-second deactivation period in an animal model. Material and Method: A miniaturized EVE device was applied to 30 8-week-old male Sprague-Dawley rats. The rats were assigned to 3 groups (no pressure for the control group, conventional -25 mm Hg for 8 h/day for conventional EVE, and CHNP mode for the CHNP group). After 28 days, micro-computed tomography was performed and skin biopsy specimens were obtained. Results: The CHNP group showed a 6.6-fold increase and the conventional EVE group showed a 4.4-fold increase in volume compared to the control group. Hematoxylin and eosin staining showed a similar increase in subcutaneous tissue thickness in both EVE groups, compared to the control group. Masson's trichome and proliferating cell nuclear antigen staining showed significantly higher collagen deposition and subdermal adipocytes in EVE groups. Immunohistochemistry against platelet endothelial cell adhesion molecule 1 showed 2.5- and 2.7-times higher vessel density in the conventional and CHNP EVE groups, respectively. There was no statistically significant difference in subcutaneous tissue thickness, collagen deposition, subdermal adipocyte proliferation, and vessel density between the 2 EVE groups. Conclusion: CHNP produced comparable results in recipient site preparation (subcutaneous tissue thickening and angiogenesis) compared to the conventional protocol, while markedly reducing the daily wear-time from 8 hours to 1 hour. Although further clinical data must be acquired, our new pressure setting seems promising and provides a more patient-friendly pre-expansion environment.

Promotion of dermal tissue engineering in a rat model using a composite 3D-printed scaffold with electrospun nanofibers and recipient-site preconditioning with an external volume expansion device

We hypothesized that use of a composite three-dimensionally (3D) printed scaffold with electrospun nanofibers in conjunction with recipient-site preconditioning with an external volume expansion (EVE) device would enable successful dermal tissue regeneration of a synthetic polymer scaffold. Cell viability, cell infiltration, extracellular matrix deposition, scaffold contraction, and mRNA expression by dermal fibroblasts cultured on three different scaffolds, namely, 3D-printed scaffold with a collagen coating, 3D-printed scaffold with an electrospun polycaprolactone nanofiber and collagen coating, and 3D-printed scaffold with an electrospun polycaprolactone/collagen nanofiber, were measured. Before scaffold implantation, rats were treated for 2 h with an EVE device to evaluate the effect of this device on the recipient site. Cell proliferation rates were significantly higher on the 3D-printed scaffold with electrospun polycaprolactone nanofiber and collagen coating than on the other scaffolds. In cell invasion studies, the 3D-printed scaffold with electrospun polycaprolactone nanofiber and collagen coating showed better cell integration than the other scaffolds. Under stereomicroscopy, fibroblasts adhered tightly to the electrospun area, and the fibroblasts effectively produced both collagen and elastin. Rat skin treated with an EVE device exhibited increased HIF-1α protein expression and capillary neoformation compared with control skin. Invasion of CD8⁺ cytotoxic lymphocytes surrounding the scaffold decreased when the recipient site was preconditioned with the EVE device. The composite 3D printed scaffold with electrospun nanofibers provided a favorable environment for proliferation, migration, and extracellular matrix synthesis by fibroblasts. Recipient-site preconditioning with an EVE device allowed for scaffold incorporation with less inflammation due to improved angiogenesis.

体外扩张器辅助自体脂肪移植乳房再造研究进展

OBJECTIVE

To review the application progress, mechanism, application points, limitations, and oncological safety of external volume expansion (EVE) assisted autologous fat grafting for breast reconstruction and provide a reference for optimizing the design of EVE.

METHODS

Based on the latest relevant articles, the basic experiments and clinical applications of EVE were summarized.

RESULTS

EVE can reduce interstitial fluid pressure, increase blood supply, and promote adipogenic differentiation, thereby benefiting the survival of transplanted fat. EVE assisted autologous fat grafting in clinical practice can improve the retention rate of breast volume and the outcome of breast reconstruction, meanwhile it doesn't increase the risk of local recurrence. But there is no standard parameters for application, and there are many complications and limitations.

CONCLUSION

EVE improves the survival of transplanted fat, but its complications and poor compliance are obvious, so it is urgent to further investigate customized products for breast reconstruction after breast cancer and establish relevant application guidelines.

Increase of glandular epithelial cell clusters by an external volume expansion device promotes adipose tissue regeneration by recruiting macrophages

Background: There is a clinical need for the use of engineered adipose tissue in place of surgical reconstruction. We previously found that the external volume expansion (EVE) device increased special cell clusters in well-vascularized connective stroma during adipose regeneration. However, the origin of these cell clusters and their role in adipose tissue regeneration remain unknown. Aim: In the present study, we evaluated EVE in the construction of expanded prefabricated adipose tissue (EPAT) in a rat model. Methods: Rats were randomized into an EVE suction group and a control group, with 24 rats in each group. The structure and origin of the special cell clusters were determined by hematoxylin and eosin staining, and immunohistochemistry; their role in adipose tissue regeneration was investigated by immunohistochemistry and Western blot analyses. Results: Special cell clusters began to increase at week 1 with a peak at week 4, and then receded from weeks 8 to 12. Clusters were identified as glandular epithelial cells as determined by their gland-like structure and expression of specific markers. The cell clusters induced significant infiltration of macrophage antigen-2 (Mac-2) positive macrophages by secreting monocyte chemoattractant protein-1 (MCP-1) at the early stage of suction. Subsequently, these infiltrated macrophages expressed massive vascular endothelial growth factor (VEGF) to promoted angiogenesis. Conclusion: EVE generated glandular epithelial cell clusters, which recruited macrophages to promote angiogenesis and subsequent adipose tissue regeneration. These findings shed light on the mechanisms underlying the effects of EVE devices on adipose tissue regeneration.