Induced Beige Adipocytes Improved Fat Graft Retention by Promoting Adipogenesis and Angiogenesis.

BACKGROUND: Fat grafting is commonly used in treating soft-tissue defects. However, the basic biology behind fat grafting is still not fully understood. Evidence of adipose browning into beige adipose tissue after fat grafting was revealed, but its role in fat grafting remains unclear. METHODS: Induced beige adipocytes and adipose-derived stem cells were obtained from human lipoaspirates and labeled with green fluorescent protein. Nude mice were each injected with 300 mg of human lipoaspirate containing green fluorescent protein-labeled adipose-derived stem cells, green fluorescent protein-labeled induced beige adipocytes, or phosphate-buffered saline. Grafted fat was harvested after 1, 4, 8, and 12 weeks for immunohistochemistry and histologic examination. Graft retention, vascularization, and adipogenic gene expression were compared. RESULTS: After 7 days' induction, adipocytes achieved browning with multilocular lipid droplets, increased mitochondria, and up-regulated browning gene expression. Fat graft retention rates at week 12 were significantly higher after injection of induced beige adipocytes than after injection of phosphate-buffered saline (46.0 ± 4.9 percent versus 31.0 ± 3.6 percent; p = 0.01), but were similar after injection of induced beige adipocytes and adipose-derived stem cells (p > 0.05). Induced beige adipocytes underwent rewhitening into white adipocytes and showed up-regulation of peroxisome proliferator-activated receptor-γ expression. Induced beige adipocytes enhanced angiogenesis, but were not active in forming vessel structures. CONCLUSIONS: Induced beige adipocytes and adipose-derived stem cells were comparable in improving fat graft retention rates. Induced beige adipocytes promote angiogenesis in a paracrine manner and are prone to rewhitening after fat grafting.

Biochemical and biomechanical comparisions of decellularized scaffolds derived from porcine subcutaneous and visceral adipose tissue.

Decellularized adipose tissue (DAT) is a promising biomaterial for adipose tissue engineering. However, there is a lack of research of DAT prepared from xenogeneic porcine adipose tissue. This study aimed to compare the adipogenic ability of DAT derived from porcine subcutaneous (SDAT) and visceral adipose tissue (VDAT). The retention of key collagen in decellularized matrix was analysed to study the biochemical properties of SDAT and VDAT. For the biomechanical study, both DAT materials were fabricated into three-dimensional (3D) porous scaffolds for rheology and compressive tests. Human adipose-derived stem cells (ADSCs) were cultured on both scaffolds to further investigate the effect of matrix stiffness on cellular morphology and on adipogenic differentiation. ADSCs cultured on soft VDAT exhibited significantly reduced cellular area and upregulated adipogenic markers compared to those cultured on SDAT. In vivo results revealed higher adipose regeneration in the VDAT compared to the SDAT. This study further demonstrated that the relative expression of collagen IV and laminin was significantly higher in VDAT than in SDAT, while the collagen I expression and matrix stiffness of SDAT was significantly higher in comparison to VDAT. This result suggested that porcine adipose tissue could serve as a promising candidate for preparing DAT.

Mechanical Micronization of Lipoaspirates for Regenerative Therapy.

Stromal vascular fraction (SVF) has become a regenerative tool for various diseases; however, legislation strictly regulates the clinical application of cell products using collagenase. Here, we present a protocol to generate an injectable mixture of SVF cells and native extracellular matrix from adipose tissue by a purely mechanical process. Lipoaspirates are put into a centrifuge and spun at 1,200 x g for 3 min. The middle layer is collected and separated into two layers (high-density fat at the bottom and low-density fat on the top). The upper layer is directly emulsified by intersyringe shifting, at a rate of 20 mL/s for 6x to 8x. The emulsified fat is centrifuged at 2,000 x g for 3 min, and the sticky substance under the oil layer is collected and defined as the extracellular matrix (ECM)/SVF-gel. The oil on the top layer is collected. Approximately 5 mL of oil is added to 15 mL of high-density fat and emulsified by intersyringe shifting, at a rate of 20 mL/s for 6x to 8x. The emulsified fat is centrifuged at 2,000 x g for 3 min, and the sticky substance is also ECM/SVF-gel. After the transplantation of the ECM/SVF-gel into nude mice, the graft is harvested and assessed by histologic examination. The result shows that this product has the potential to regenerate into normal adipose tissue. This procedure is a simple, effective mechanical dissociation procedure to condense the SVF cells embedded in their natural supportive ECM for regenerative purposes.

[Systemic therapy for defects of skin and soft tissue on the knees after severe trauma or burn].

OBJECTIVE: To explore the methods of systemic treatment of defects of skin and soft tissue on the knees after severe trauma or burn. METHODS: Twenty patients with defects of skin and soft tissue on the knees after severe trauma or burn hospitalized in our center from January 2009 to December 2011. The injury areas on the knees ranged from 5 cm×4 cm to 30 cm×20 cm. The wounds were treated with radical debridement, vacuum sealing drainage, and douche through dripping to control infection in early stage. Then they were covered with transplantation of skin grafts plus flap or only with flap. Totally 8 local flaps (including 6 local rotation or transposition flaps and 2 saphenous artery flaps) and 12 free flaps (including 8 anterolateral thigh flaps and 4 latissimus dorsi musculocutaneous flaps) were used. The flap size ranged from 6 cm×5 cm to 32 cm×22 cm. The rehabilitation training of the knee joints was carried out in the early stage after wound healing. RESULTS: All free skin grafts and flaps used in 15 patients survived. Thirteen of them were primarily healed, while some small parts of skin grafts of the other two patients were in poor condition because of infection, and they healed after another session of skin transplantation. Infection occurred under the free flap in one of the 5 patients transplanted with flaps only, which was healed after continuous douche through dripping and another surgical debridement following wet dressing. The knee joints were in good function during the follow-up period of 1 - 3 years. CONCLUSIONS: The systemic therapy of radical debridement, vacuum sealing drainage technique, douche through dripping, transplantation of large autologous grafts and flaps, and the early rehabilitation training are effective and reliable in repairing defects of skin and soft tissue at the knee region after severe injuries.