Faculty Bibliography

Recent technical and scientific advances in fat grafting procedures and concepts have improved predictability of fat grafting. Large-volume fat injection is gaining much attention as an attracting procedure for body contouring and reconstruction, but an increasing number of complications also has been recognized over the world. In this article, typical complications after fat grafting are described, as well as an explanation of how and why they occur, and how surgeons can avoid and treat complications.

Autologous fat grafting is an exciting part of plastic and reconstructive surgery. Fat serves as a filler and its role in tissue regeneration will likely play a more important role in our specialty. As we learn more about the basic science of fat grafting and the standardized techniques and instruments used for fat grafting, this procedure alone or in conjunction with invasive procedures may be able to replace many operations that we perform currently. Its minimally invasive nature will benefit greatly our cosmetic and reconstructive patients, and may even achieve better clinical outcomes.

BACKGROUND: Clinical results of fat grafting have been unpredictable. In this article, the authors hypothesize that centrifugation creates "graded densities" of fat with varying characteristics that influence lipoaspirate persistence and quality. METHODS: Aliquots of human female lipoaspirate (10 cc) were centrifuged for 3 minutes at 1200 g. The bloody and oil fractions were discarded. Subsequently, 1.0 cc of the highest density and lowest density fat was separated for lipoinfiltration or analysis. Highest density or lowest density fat grafted into adult FVB mice was harvested at 2 and 10 weeks to quantify short- and long-term persistence, respectively. Progenitor cell number and expression of vascular endothelial growth factor, stromal cell-derived factor-1alpha, platelet-derived growth factor, and adiponectin were analyzed by flow cytometry and enzyme-linked immunosorbent assay, respectively. RESULTS: Greater percentages of highest density fat grafts remain at 2 and 10 weeks after injection compared with lowest density fat grafts (85.4 +/- 1.9 percent versus 62.3 +/- 0.1 percent, p = 0.05; and 60.8 +/- 4.9 versus 42.2 +/- 3.9, p < 0.05, respectively). Highest density fractions contain more progenitor cells per gram than lowest density fractions (2.0 +/- 0.2-fold increase, p < 0.01). Furthermore, concentrations of vascular endothelial growth factor, stromal vascular fraction, platelet-derived growth factor, and adiponectin are all elevated in highest density compared with lowest density fractions (34.4 percent, p < 0.01; 34.6 percent, p < 0.05; 52.2 percent, p < 0.01; and 45.7 percent, p < 0.05, respectively). CONCLUSIONS: Greater percentages of highest density fractions of lipoaspirate persist over time compared with lowest density fractions. A vasculogenic mechanism appears to contribute significantly, as highest density fractions contain more progenitor cells and increased concentrations of several vasculogenic mediators than lowest density fractions.

BACKGROUND: : Lipoaspirate centrifugation creates graded density of adipose tissue. High-density fat contains more vasculogenic cytokines and progenitor cells and has greater graft survival than low-density fat. The authors hypothesize that accelerating the bone marrow-derived progenitor cell response to injected low-density fat will improve its graft survival. METHODS: : Male 8-week-old FVB mice (n = 60) were grafted with either high-density (n = 20) or low-density (n = 40) human lipoaspirate. Half of the mice receiving low-density fat (n = 20) were treated with a stem cell mobilizer for 14 days. Grafted fat was harvested at 2 and 10 weeks for analysis. RESULTS: : Low-density fat, low-density fat plus daily AMD3100, and high-density fat had 26 +/- 3.0, 61.2 +/- 7.5, and 49.6 +/- 3.5 percent graft survival, respectively, at 2 weeks (low-density fat versus low-density fat plus daily AMD3100 and low-density fat versus high-density fat, both p < 0.01). Similar results were observed 10 weeks after grafting. Mice receiving low-density fat plus daily AMD3100 had significantly more vasculogenic progenitor cells per cubic centimeter of peripheral blood (p < 0.01) and more new blood vessels (p < 0.01). Both low-density fat plus daily AMD3100 and high-density fat contained more stromal-derived factor-1alpha and vascular endothelial growth factor mRNA/protein. CONCLUSION: : Endogenous progenitor cell mobilization enhances low-density fat neovascularization, increases vasculogenic cytokine expression, and improves graft survival to a level equal to that of high-density fat grafts.

BACKGROUND: Fat grafting has been shown clinically to improve the quality of burn scars. To date, no study has explored the mechanism of this effect. We aimed to do so by combining our murine model of fat grafting with a previously described murine model of thermal injury. METHODS: Wild-type FVB mice (n=20) were anaesthetised, shaved and depilitated. Brass rods were heated to 100 degrees C in a hot water bath before being applied to the dorsum of the mice for 10s, yielding a full-thickness injury. Following a 2-week recovery period, the mice underwent Doppler scanning before being fat/sham grafted with 1.5cc of human fat/saline. Half were sacrificed 4 weeks following grafting, and half were sacrificed 8 weeks following grafting. Both groups underwent repeat Doppler scanning immediately prior to sacrifice. Burn scar samples were taken following sacrifice at both time points for protein quantification, CD31 staining and Picrosirius red staining. RESULTS: Doppler scanning demonstrated significantly greater flux in fat-grafted animals than saline-grafted animals at 4 weeks (fat=305+/-15.77mV, saline=242+/-15.83mV; p=0.026). Enzyme-linked immunosorbent assay (ELISA) analysis in fat-grafted animals demonstrated significant increase in vasculogenic proteins at 4 weeks (vascular endothelial growth factor (VEGF): fat=74.3+/-4.39ngml(-1), saline=34.3+/-5.23ngml(-1); p=0.004) (stromal cell-derived factor-1 (SDF-1): fat=51.8+/-1.23ngml(-1), saline grafted=10.2+/-3.22ngml(-1); p<0.001) and significant decreases in fibrotic markers at 8 weeks (transforming growth factor-ss1(TGF-ss): saline=9.30+/-0.93, fat=4.63+/-0.38ngml(-1); p=0.002) (matrix metallopeptidase 9 (MMP9): saline=13.05+/-1.21ngml(-1), fat=6.83+/-1.39ngml(-1); p=0.010). CD31 staining demonstrated significantly up-regulated vascularity at 4 weeks in fat-grafted animals (fat=30.8+/-3.39 vessels per high power field (hpf), saline=20.0+/-0.91 vessels per high power field (hpf); p=0.029). Sirius red staining demonstrated significantly reduced scar index in fat-grafted animals at 8 weeks (fat=0.69+/-0.10, saline=2.03+/-0.53; p=0.046). CONCLUSIONS: Fat grafting resulted in more rapid revascularisation at the burn site as measured by laser Doppler flow, CD31 staining and chemical markers of angiogenesis. In turn, this resulted in decreased fibrosis as measured by Sirius red staining and chemical markers

BACKGROUND: Autogenous fat grafting has been observed to alleviate the sequelae of chronic radiodermatitis. To date, no study has replicated this finding in an animal model. METHODS: The dorsa of adult wild-type FVB mice were shaved and depilitated. The dorsal skin was then distracted away from the body and radiated (45Gy) using a Varian 2300 Linear Accelerator. Four weeks following radiation, 1.5cc fat or sham grafts were placed in the dorsal subcutaneous space. Gross results were analyzed photometrically. The animals were sacrificed at 4 and 8 weeks following fat or sham grafting and their dorsal skin was processed for histologic analysis. Inflammation was assessed by epidermal thickness measurements on H&E stained sections. Vascular density was assessed using CD31 staining. Fibrosis was assessed using Smad-3 and Picrosirius Red staining. RESULTS: Hyperpigmentation and ulceration were grossly improved in fat-grafted mice compared to sham-grafted controls. Epidermal thickness measurements demonstrated decreased thickness in fat-grafted animals at both timepoints (20.6+/-1.5mum vs 55.2+/-5.6mum, p=0.004; 17.6+/-1.1mum vs 36.3+/-6.1mum, p=0.039). Vascular density was decreased in fat-grafted mice compared to sham-grafted at both timepoints (17.5+/-1.3 vessels/hpf vs 29+/-3.5, p=0.055; 13.25+/-1.4 vs 17.0+/-1.6, p=0.003). Intensity of Smad3 staining was significantly decreased in fat-grafted animals at both timepoints (2.77+/-0.3% vs 4.98+/-0.9%, p=0.004; 3.05+/-0.2% vs 5.81+/-0.3%, p=0.011). Picrosirius red staining demonstrated a diminished scar-index in fat-treated animals at both timepoints (.54+/-0.05 vs .74+/-0.07, p=0.034; .55+/-0.06 vs .93+/-.07, p=0.001). CONCLUSIONS: Fat grafting attenuates inflammation in acute radiodermatitis and slows the progression of fibrosis in chronic radiodermatitis

BACKGROUND: : Radiation therapy is a cornerstone of oncologic treatment. Skin tolerance is often the limiting factor in radiotherapy. To study these issues and create modalities for intervention, the authors developed a novel murine model of cutaneous radiation injury. METHODS: : The dorsal skin was isolated using a low-pressure clamp and irradiated. Mice were followed for 8 weeks with serial photography and laser Doppler analysis. Sequential skin biopsy specimens were taken and examined histologically. Tensiometry was performed and Young's modulus calculated. RESULTS: : High-dose radiation isolated to dorsal skin causes progressive changes in skin perfusion, resulting in dermal thickening, fibrosis, persistent alopecia, and sometimes ulceration. There is increased dermal Smad3 expression, and decreased elasticity and bursting strength. CONCLUSIONS: : This model of cutaneous radiation injury delivers reproducible localized effects, mimicking the injury pattern seen in human subjects. This technique can be used to study radiation-induced injury to evaluate preventative and therapeutic strategies for these clinical issues

The viability of fat grafts harvested with an established technique after cryopreservation remains unknown. This study was conducted in vitro to evaluate the viability of autologous fat grafts harvested with the Coleman technique and subsequently preserved with our preferred cryopreservation method. Eight adult females were enrolled in this study. In each patient, 10 mL of fat grafts were harvested with the Coleman technique by a single surgeon from the lower abdomen. In group 1, 5 mL of fresh fat grafts were mixed with cryoprotective agents and underwent cryopreservation with controlled slow cooling and fast rewarming. In group 2, 5 mL of fresh fat grafts without cryopreservation from the same patient served as a control. The fat graft samples from both groups were evaluated with trypan blue vital staining, glycerol-3-phophatase dehydrogenase assay, and routine histology. Viable adipocyte counts were found similar in both group 1 and group 2 (3.46 +/- 0.91 vs. 4.12 +/- 1.11 x 10/mL, P = 0.22). However, glycerol-3-phophatase dehydrogenase activity was significantly lower in group 1 compared with group 2 (0.47 +/- 0.09 vs. 0.66 +/- 0.09 u/mL, P < 0.001). Histologically, the normal structure of fragmented fatty tissues was found primarily in both groups. Our results indicate that autologous fat grafts harvested with the Coleman technique and preserved with our preferred cryopreservation method have a normal histology with near the same number of viable adipocytes as compared with the fresh fat grafts. However, those cryopreserved fat grafts appear to have a less optimal level of adipocyte specific enzyme activity compared with the fresh ones and thus may not survive well after they are transplanted without being optimized

BACKGROUND: The study of human autologous fat grafting has been primarily anecdotal. In this study, the authors aim to develop a murine model that recapitulates human fat grafting to study the fate of injected fat and the cell populations contained within. METHODS: The authors' method of fat harvesting and refinement has been described previously. The authors injected nude and tie2/lacZ mice with 2 ml of human lipoaspirate placed on the dorsal surface in a multipass, fan-like pattern. Fatty tissue was injected in small volumes of approximately 1/30 ml per withdrawal. The dorsal skin and associated fat was excised at various time points. Sections were stained with hematoxylin and eosin and cytochrome c oxidase IV. Transgenic tie2/lacZ samples were stained with X-galactosidase. At the 8-week time point, volumetric analysis was performed. RESULTS: Volumetric analysis at the 8-week time point showed 82 percent persistence of the original volume. Gross analysis showed it to be healthy, nonfibrotic, and vascularized. Hematoxylin and eosin analysis showed minimal inflammatory or capsular reaction, with viable adipocytes. Fat grafted areas were vascularized with multiple blood vessels. Cytochrome c oxidase IV human-specific stain and beta-galactosidase expression revealed these vessels to be of human origin. CONCLUSIONS: The authors have developed a murine model with which to study the fate of injected lipoaspirate. There is a high level of persistence of the grafted human fat, with minimal inflammatory reaction. The fat is viable and vascularized, demonstrating human-derived vessels in a mouse model. This model provides a platform for studying the populations of progenitor cells known to reside in lipoaspirate