Volume Retention, Metabolism, and Cellular Composition of Human Fat Xenografts

The fates of different types of adipose tissue after transplantation in mice

Fat grafting is one of the most commonly applied procedure for soft-tissue repair. However, it remains unclear whether the type of adipose tissue would have any effects on fat graft survival. The present study aimed to determine fates of fat grafting of three different types of fat tissue. In this study, mice were randomly divided into three groups, white adipose tissue (WAT) group, beige adipose tissue (beige AT) group and brown adipose tissue (BAT) group. Before transplantation, donor mice were injected with rosiglitazone or phosphate-buffered saline (PBS). The WAT and BAT were obtained from PBS-treated mice while beige AT was obtained from the rosiglitazone-treated mice. Three types of fat tissue (150 mg each) were transplanted in three groups, respectively, and harvested at 2, 4 or 12 weeks. The BAT and beige AT contained smaller adipocytes and expressed higher level of uncoupling protein-1 gene. The retention rate of the transplanted fat was significantly higher for beige than for white fat, but was significantly lower for brown than for white fat. Transplanted brown fat was characterized by upregulated inflammation and high endoplasmic reticulum stress. By contrast, fat grafts in beige AT group showed the best adipogenic capacity, moderate inflammation level and superior angiongenesis. In vitro, under hypoxic condition, fewer apoptotic cells were found in beige adipocyte group than that in brown and white adipocyte group. Conditioned medium from brown adipocytes induced M1 polarization of RAW 264.7 macrophages while that from beige adipocytes effectively promoted M2 polarization. Therefore, we suggest that beige AT provides a new potential choice for fat grafting because of low inflammation and superior survival but BAT might not be ideal for fat grafting due to its poor survival.

Fat Grafts Augmented With Vitamin E Improve Volume Retention and Radiation-Induced Fibrosis

BACKGROUND

Treatments for radiation-induced fibrosis range from vitamin E and pentoxifylline systemically to deferoxamine and fat grafting locally. Regarding fat grafting, volume retention hinders its long-term functionality and is affected by two factors: inflammation and necrosis secondary to hypovascularity.

OBJECTIVE

We aimed to simultaneously improve fat graft retention and radiation-induced fibrosis by integrating vitamin E and pentoxifylline into fat grafts locally.

METHODS

Forty adult CD-1 nude male mice at 6 weeks of age underwent scalp irradiation and recovered for four weeks to allow for the development of fibrosis. Mice received 200μL of donor human fat graft to the scalp. Mice were separated into 4 conditions: no grafting, fat graft without treatment, graft treated with pentoxifylline, and graft treated with vitamin E. Fat graft volume retention was monitored in-vivo using microCT scans at weeks 0, 1, 2, 4, 6, and 8 after grafting. Histological and cytokine analysis of the scalp skin and fat grafts were also performed.

RESULTS

Vitamin E (VE) treated grafts had significant improvement in dermal thickness and collagen density of overlying skin compared to all other groups. VE decreased 8-isoprostane and increased CD31 + staining compared to the other grafted groups. Cytokine analysis revealed decreased inflammatory and increased angiogenic markers in both the fat graft and overlying skin of the vitamin E group. Fat graft volume retention was significantly improved in the vitamin E group starting at 1 week post grafting.

CONCLUSION

Radiation-induced fibrosis and fat graft volume retention are both simultaneously improved with local administration of vitamin E.

The Effect of Ultrasonic Liposuction Energy Levels on Fat Graft Viability

BACKGROUND

The use of fat obtained from ultrasound-assisted liposuction is popular. However, no study has considered the effect of different energy levels on fat grafts.

OBJECTIVES

We hypothesized that different ultrasonic energy levels could change the fat graft viability.

METHODS

Both flanks of 15 CD1 nude mice (30 experimental areas) were used, with experimental areas randomly distributed into five groups. Using different energy settings, fat grafts were obtained from a patient's abdominoplasty material and applied to the mouse flank regions. Device settings were intermittent mode with 50% vibration amplitude in group 1, continuous mode with 50% vibration amplitude in group 2, intermittent mode with 90% vibration amplitude in group 3, and continuous mode with 90% vibration amplitude in group 4. The control group was grafted with fat obtained via the conventional method. After 6 weeks, all mice were sacrificed, and fat grafts were excised. Sections were stained with hematoxylin-eosin, Masson's trichrome, and anti-perilipin A antibody.

RESULTS

The perilipin A immunostaining result was lowest in group 4, indicating the lowest viable cell count (p < 0.01). There was no significant difference between groups for the other parameters (p > 0.05).

CONCLUSION

High ultrasonic energy may affect fat graft survival. If fat injection is planned, avoiding high energy settings (our recommendation is not to exceed 16 Watts.) should be considered. We also recommend increasing the vibration amplitude rather than switching from intermittent to continuous mode in body parts that are relatively resistant to liposuction.

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