Autologous Fat Transplantation Versus Adipose-Derived Stem Cell Enriched Lipografts: A Study

Transcription

1 INTERNATIONAL CONTRIBUTION Research Autologous Fat Transplantation Versus Adipose-Derived Stem Cell Enriched Lipografts: A Study Aesthetic Surgery Journal 31(6) The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journalspermissions.nav DOI: / X Aris Sterodimas, MD, MSc; Jose de Faria, MD; Beatriz Nicaretta, MD; and Filippo Boriani, MD, MSc Abstract Background: Several techniques for lipoinjection have been described in the literature. Recently, the role of adult stem cells in adipose tissue has gained interest. Objectives: The authors compare autologous fat transplantation to adipose-derived stem cell enriched lipografts. Methods: A group of 20 patients with congenital or acquired facial tissue defects were included in this study and randomly divided into two groups. Ten patients were treated with autologous fat transplantation (Group A; ml per session), and the remaining ten were treated with adipose-derived stem cell enriched lipografts (Group B; ml per session). Overall patient satisfaction after both treatments was evaluated at six, 12, and 18 months after the initial surgical procedure. Results: In Group A, three patients achieved aesthetically-acceptable results after the first treatment; the remaining seven patients required additional sessions. In Group B, all patients required only one treatment. Analysis of patient satisfaction in the first six months clearly demonstrated better results in Group B. However, by the 18-month evaluation, there was no statistical difference between the two groups in terms of patient satisfaction. Conclusions: Adipose-derived stem cell enriched lipografts produced aesthetically-acceptable results without the need for repeat treatment sessions, which are necessary with autologous fat transplantation. Further long-term studies are necessary to confirm the favorable results seen in this study. Keywords autologous fat transplantation, adipose-derived stem cells, enriched lipograft, stromal vascular fraction There is a major clinical call for techniques that enable cosmetic surgeons to adequately reconstruct congenital and acquired soft tissue defects. Human adipose tissue is an ideal source of autologous cells, since it is plentiful and easily obtained through liposuction. Therefore, autologous fat is frequently transplanted for a variety of cosmetic and reconstructive indications, including posttraumatic defects of the face and body, hemifacial atrophy, sequelae of radiation therapy, lip and facial augmentation, and facial rejuvenation for fine lines and wrinkles. 1-5 In the past 20 years, advancements in techniques and instrumentation have produced results that make fat grafting a viable option for soft tissue augmentation. 6,7 Successful three-dimensional sculpting requires careful attention to patient preparation, planning, and optimizing the harvesting, storage, and transplantation of the tissue. Fat is a living tissue that must be kept in close proximity to a nutritional and respiratory source to survive. Fatgrafting injections should be performed in a retrograde Dr. Sterodimas and Dr. de Faria are consultant plastic surgeons in the Department of Plastic Surgery, Pontifical Catholic University of Rio de Janeiro and the Carlos Chagas Post-Graduate Medical Institute, Rio de Janeiro, Brazil. Dr. Sterodimas is also a consultant plastic surgeon at the Ivo Pitanguy Institute, Rio de Janeiro, Brazil. Dr. Nicaretta is chief resident in the Department of Plastic Surgery, General Policlinic, Rio de Janeiro, Brazil. Dr. Boriani is specialist registrar in the Department of Plastic Surgery, Frenchay Hospital, North Bristol NHS Trust, Bristol, England. Corresponding Author: Dr. Aris Sterodimas, Rua Dona Mariana 65, , Rio de Janeiro, Brazil. aris@sterodimas.com

2 Sterodimas et al 683 Figure 1. Autologous fat transplant process (Group A). mode to avoid intravascular fat injection. Modifications of lipoinjection techniques to improve the survival rate for injected fat have also been studied, but there remains an unpredictable degree of resorption of the transplanted fat, and repeated treatment sessions are usually required to achieve the final result. 8,9 The role of adult stem cells in adipose tissue has generated much interest. 10,11 Lipoaspirate, an otherwise disposable by-product of cosmetic surgery, has been shown to contain a putative population of stem cells, termed adiposederived stem cells (ADSC), which share many similarities to the stromal cells derived from bone marrow. 12 ADSC reside within the stromal vascular fraction (SVF) in fat tissue, which is thought to harbor cells that display extensive proliferative capacity and multilineage potential. 13 Several authors have published articles on ADSC-enriched lipografting, but there has been no published study comparing this new technique with autologous fat transplantation. To our knowledge, this is the first such study. We compare the two techniques, describing their benefits and drawbacks and evaluating long-term patient satisfaction. procedures took place at the clinics of the authors and were performed by the same leading surgeon (AS). A group of 20 patients with congenital or acquired facial tissue defects were included in the study. The participants were randomly divided into two groups. Ten patients were treated with autologous fat transplantation (Group A; ml per session), and the remaining 10 were treated with ADSC-enriched lipografts (Group B; ml per session). Nine of the 20 patients (five in Group A, four in Group B) were smokers and were asked to refrain from smoking for one month before treatment. Four patients (two in Group A, two in Group B) had a history of hypertension under treatment. One patient in Group A had insulin-dependent diabetes, and one patient in Group B was being treated for a history of chronic obstructive pulmonary disease. Patients were followed up at six, 12, and 18 months after their initial treatment session and were asked to rate their overall satisfaction with their posttreatment facial appearance on a five-point scale (1 = poor, 2 = fair, 3 = good, 4 = very good, 5 = excellent). This scale has been utilized in and validated by several prior studies Methods Patients This prospective study was approved by the Northern Regional Ethics Committee, Rio de Janeiro, Brazil. The Surgical Technique The areas to be liposuctioned and grafted were marked with the patient standing. Preoperative anesthesia, administered in the surgical suite, consisted of an

3 684 Aesthetic Surgery Journal 31(6) Figure 2. Adipose-derived stem cell lipografting procedure (Group B). epidural block and intravenous sedation. Patients were placed in a supine position. After an injection of normal saline wetting solution containing 1:500,000 of adrenaline with a small-bore cannula and a waiting period of 15 minutes, a 60-mL syringe attached to a 4-mm blunt cannula was inserted through small incisions made in the abdominal area. Fat was aspirated through the syringe. For patients in Group A, the syringe was held vertically with the open end pointing downward. Isotonic saline was added to the syringe; the fat was washed; and the exudate was discarded. The procedure was repeated until the fat became yellow in color, free of blood and other contaminants 5,21,22 (Figure 1). For patients in Group B, the aspirated fatty tissue was treated in the following manner (Figure 2): Two-thirds of the aspirated fat was used to isolate the SVF, and digestion was completed with 0.075% collagenase (Sigma, St. Louis, Missouri) in buffered saline and agitation for 30 minutes at 37 C. Transfer was performed in 10-mL syringes. The SVF (containing the ADSC) was separated with centrifugation at 1200 g for five minutes (IEC Medispin Tabletop Centrifuge, Needham, Massachusetts). The SVF was located in the pellet derived from the centrifuged fat at the bottom of the lipoaspirate. The remaining one-third of the aspirated fat was treated similarly to the Group A procedure. It was separated into fat and fluid with the syringe held vertically, open end down. Isotonic saline was added to the syringe; the fat and saline were separated; and the exudate was discarded. The procedure was repeated until the fat became yellow in color, free of blood and other contaminants. 5 The SVF and the purified fat were mixed and transferred into 10-mL syringes for injection. For both groups, this whole procedure was performed inside the operating theater by two tissue engineers, biologists who had undergone a two-month course on regenerative biology and tissue engineering. The entire surgical portion took approximately 90 minutes. In both groups, the fat graft was woven into the deep tissues of the face with multiple passes of a 1-mm cannula, injecting only a tiny amount with each pass through stab incisions. The injections occurred on multiple planes, through different trajectories with the same cannula. The fat was transferred as the cannula was withdrawn, always from the deeper aspect to more superficial areas. In this way, the entire face was addressed, one cosmetic unit at a time. Antibiotics, analgesics, and anti-inflammatory medications were prescribed for three days posttreatment. Results The average age of the patients in Group A was 46.2 years (range, 25-70), and the average age of the patients in Group B was 43.9 (range, 22-72). Mean preoperative body mass index was 21.6 in Group A (range, ) and 21.5 in

4 Sterodimas et al 685 Table 1. Patient Demographic Data for Group A: Autologous Fat Grafting Age, y Sex M F F F F M F F F F Diagnosis BSS PRS FA FA T T T BSS BSS FA SEL, ml Session Session Session Follow-up, mos Satisfaction 6 mos mos mos BSS, Barraquer-Simons syndrome; PRS, Parry Romberg syndrome; FA, facial atrophy; T, traumatic; SEL, stromal enriched lipograft. Table 2. Patient Demographic Data for Group B: Adipose-Derived Stem Cell Enhanced Age, y Sex F M F F F F F M F M Diagnosis BSS PRS PRS T FA T T BSS FA LP SEL, ml a Follow-up, mos Satisfaction 6 mos mos mos BSS, Barraquer-Simons syndrome; PRS, Parry Romberg syndrome; T, traumatic; FA, facial atrophy; LP, lupus erythematosus; SEL, stromal enriched lipograft. a One session for each patient. Group B (range, ). Thirty to 400 ml of fat (average, 180 ml) were lipoaspirated in Group A (Table 1); 60 to 800 ml (average, 380 ml) were aspirated in Group B (Table 2). Twelve to 165 ml of fat (average, 78.5) were transplanted in the first treatment session in Group A. The amount of adipose tissue graft transplanted in Group B varied from 8 to 155 ml (average, 74.3 ml). There was only one infection among the Group A patients, which was treated with seven days of oral cefuroxime. Edema and bruising were noted in all patients in both groups but resolved within seven to 10 days. In Group A, three patients achieved aesthetically-acceptable results after a single treatment, but the remaining seven required additional sessions of autologous fat grafting. Three had one additional session, and four needed two additional sessions (Table 1). The volume of fat graft

5 686 Aesthetic Surgery Journal 31(6) Figure 3. Patient satisfaction rates six months after treatment. (A) Group A patients (autologous fat transplant). (B) Group B patients (adipose-derived stem cell lipografting). At this time point, satisfaction rates were significantly higher for the patients in Group B, who underwent fewer treatment sessions overall. Figure 4. Patient satisfaction rates 12 months after treatment. (A) Group A patients (autologous fat transplant). (B) Group B patients (adipose-derived stem cell lipografting). Figure 5. Patient satisfaction rates 18 months after treatment. (A) Group A patients (autologous fat transplant). B, Group B patients (adipose-derived stem cell lipografting). At this time point, there was no statistical difference between the satisfaction rates of patients in Group A and Group B.

6 Sterodimas et al 687 Figure 6. (A, D) This 42-year-old woman presented for treatment of bilateral facial depressions. She requested the least invasive procedure that could correct her facial deformity. She was randomly assigned to Group A (autologous fat transplantation). In the first session, 97 ml of fat were injected. (B, E) After six months, the patient was evaluated, and her satisfaction with the result was rated as good. She underwent a second procedure eight months after the initial treatment and received 22 ml of graft at that time. After 12 months, the patient was evaluated, and her satisfaction with the result was rated as very good. (C, F) Twenty months after the initial procedure. The patient s overall satisfaction with the appearance of her face at 18 months was rated as very good. transplanted in these extra sessions ranged from 12 to 75 ml. All patients in Group B required only one treatment session. Analysis of patient satisfaction in the first six months clearly demonstrated better results in Group B (Figure 3). However, by the 18-month evaluation, there was no statistical difference between the two groups in terms of patient satisfaction. Satisfaction ratings for both groups at all three follow-up points (six, 12, and 18 months) are shown in Figures 3 5. Clinical results from four patients in the series (two from Group A, two from Group B) are shown in Figures 6 9. Discussion As with every surgical procedure, the success of fat grafting depends on many factors: harvesting sites, the techniques and instruments utilized to harvest the fat tissue, fat processing, the volume of fat implantation,

7 688 Aesthetic Surgery Journal 31(6) Figure 7. (A) This 70-year-old woman presented for correction of posttraumatic frontal depression. She requested the least invasive procedure to correct her facial deformity. She was randomly included in Group A, to receive autologous fat grafting. In one session, 18 ml of fat were injected. After six and 12 months, the patient was evaluated, and her satisfaction with the result was rated as good. She was offered but declined any additional treatment. (B) Eighteen months posttreatment, the patient still rated her overall satisfaction with her facial appearance as good. sites to be implanted, and the level of placement. Because the process is multifactorial, variability inherently exists. These factors, along with others that may not yet be understood, cause the results of fat grafting to be unpredictable with some techniques and in some areas. Thus far, there is no agreement in the literature about the best way of processing fat to ensure maximal take and viability of the graft. 23 The limitations of autologous fat transplantation are well known, particularly its unpredictability in terms of volume maintenance and the need for multiple treatment sessions Adipose tissue is believed to constitute an ideal source of uncultured stromal stem cells, and the potential of using autologous adult stem cells derived from fat tissue is quickly becoming a clinical reality. 28 The presence of ADSC has clinical implications for autologous fat transfer because they may contribute to neoangiogenesis in the acute phase by acting as endothelial progenitor cells or angiogenic-factor-releasing cells. 29,30 ADSC are known to secrete angiogenic factors such as vascular endothelial growth factor and hepatocyte growth factor. 31 In vivo, ADSC demonstrate the capacity to proliferate in response to a hypoxic insult remote from their resident niche, and this has been supported by in vitro studies showing increasing ADSC proliferation with greater degrees of hypoxia. 32 ADSC also upregulate their proneovascular activity in response to hypoxia and may harbor the capacity to home to ischemic tissue and function cooperatively with existing vasculature to promote angiogenesis. 33 ADSC are thought to be more resistant to ischemia, as is the case for bone marrow derived marrow stromal cells, which can be functional for 72 hours under ischemia. 30 In addition, ADSC can affect long-term survival of transplanted adipose by acting as preadipocytes. 34 ADSC are isolated by enzymatic digestion, filtration, and centrifugation of the SVF, which contains the adipose stem cells along with nonadherent cells. The SVF can be used directly as a source of stem cells. This process converts ADSC-poor aspirated fat to ADSC-rich fat. The number of functional ADSC is likely to be important for tissue repair and remodeling. ADSC differentiate into vascular endothelial cells, which contribute to neoangiogenesis in the acute phase of fat transplantation. 14 A recent study demonstrated no statistical differences in adipocyte viability among abdominal fat, thigh fat, flank fat, or knee fat donor sites. 35 However, the abdomen seems to be preferable to the hip/thigh region for harvesting adipose tissue when SVF cells are considered for stem cell based therapies in one-step surgical procedures. 36 For this reason, the abdominal area was chosen as the donor area for liposuction in both groups in our present study. In harvesting and refining fat grafts, it is important to respect and maintain the tissue architecture of living fat. Any mechanical or chemical insult that damages its fragile tissue architecture will result in eventual necrosis of the injected fat. 37

8 Sterodimas et al 689 Figure 8. (A, C) This 38-year-old man presented with bilateral facial lipodystrophy (Barraquer-Simons syndrome). He requested the least invasive procedure to correct his facial deformities. He had not undergone any prior treatments. He was randomly included in Group B, to undergo lipografting enriched with adipose-derived stem cells. In one session, 127 ml of fat were injected. At six and 12 months, he was evaluated, and his satisfaction with the result was rated as excellent. (B, D) Twenty-one months posttreatment, the patient s satisfaction rating continued to be excellent.

9 690 Aesthetic Surgery Journal 31(6) Figure 9. (A, C) This 72-year-old woman presented for treatment of bilateral facial depressions. Before injection, she was receiving corticosteroid treatment for lupus erythematosus. She requested the least invasive procedure to correct her facial deformities. She was randomly included in Group B, to undergo lipografting enriched with adipose-derived stem cells. In one session, 78 ml of fat were injected. At six and 12 months, she was evaluated, and her satisfaction with the result was rated as very good. (B, D) Twenty months posttreatment, the patient s satisfaction rating continued to be very good.

10 Sterodimas et al 691 In Group A, the fat graft was prepared as described previously, avoiding any chemical or mechanical procedure. Recent reports have shown that mechanical centrifugation does not appear to enhance immediate fat tissue viability before implantation. 38 Centrifugation, however, plays a beneficial role in concentrating SVF and ADSC, although excessive centrifugation can destroy adipocytes as well as ADSC. The degree of adipocyte destruction differs among patients, but only minor differences in percentage of cell destruction have been shown among the different centrifugal forces. 39 A previous study found that centrifugation of aspirated fat at 1200 g decreased the fat volume by 30%, damaging 12% of the adipocytes and 0% of the ADSC. 15 This was confirmed by a recent study showing that cell survival rates were significantly lower when centrifugation forces of 1200 g were applied for more than five minutes and when forces of 3000 g were applied for more than one minute. 40 Among the tested centrifugal forces, 1200 g is considered optimal for obtaining good short- and long-term results in adipose transplantation. 39,41 A recent study also showed that ADSC concentration is significantly higher in lipoaspirate that has been washed by saline, as compared to the decanted and centrifuged lipoaspirate samples. However, the pellet collected at the bottom of the centrifuged lipoaspirate sample showed the highest concentration of ADSC. 42 Based on this finding, in Group B the washed autologous fat (one-third of the lipoaspirate) was supercharged by the SVF isolated by centrifugation from the remaining two-thirds of the lipoaspirate. The time needed to process the collected fat for SVF extraction was approximately 80 to 90 minutes in Group B. This is a limitation, since it is much longer than the time needed to perform the autologous fat-grafting procedure on the face. The amount of donor fat available is also an important limiting factor. This is particularly important when the ADSC-enriched lipograft is chosen as a treatment plan. In this study, the amount of lipoaspirated fat needed to perform lipografting was almost double the lipoaspirated fat needed for autologous fat transplantation in each treatment session. However, when one considers that more than one treatment session is usually needed for treatment with autologous fat, the total amounts of fat needed for both types of treatment are comparable. Surgeons should keep in mind that there is an additional cost per procedure associated with ADSC-enriched lipografting. The cost of consumables needed for the preparation, the presence of two tissue engineers, and the extra cost for the operating theater are all factors that increase the final cost of this surgical procedure. Again, though, the multiple treatment sessions needed for autologous fat grafting render the two procedures similar in cost; in fact, ADSC lipografting may even have a lower overall cost. In this study, all patients in Group B achieved aesthetically-acceptable results through a single session, which is the desired result after any surgical procedure. Analysis of patient satisfaction in the first six months clearly showed a higher outcome for patients in Group B, and this high percentage of satisfaction was maintained at 12 and 18 months after the procedure. Although the Group A satisfaction rates were much lower initially (at the sixmonth visit), the satisfaction rates of the two groups at the final visit (18 months) were not statistically different. Although patients in Group A had to undergo a significantly higher number of sessions, their final satisfaction was not inferior to the satisfaction rate of Group B patients. Conclusions Results from this study show that ADSC-enriched lipografting produces aesthetically-acceptable results without the need for repeated treatment sessions. Similar aestheticallyacceptable results are achieved with autologous fat transplantation, but more treatment sessions are generally required. Although this study evaluated results in only a small series of patients ADSC-enriched lipografting appears to be promising and advantageous when compared to traditional autologous fat transplantation. Further longterm studies are required to confirm the favorable results seen in this study. Disclosures The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article. Funding The authors received no financial support for the research, authorship, and publication of this article. References 1. Illouz YG. The fat cell graft : a new technique to fill depressions. Plast Reconstr Surg 1986;78: Guerrerosantos J, Guerrerosantos F, Orozco J. Classification and treatment of facial tissue atrophy in Parry- Romberg disease. Aesthetic Plast Surg 2007;31: Bucky LP, Percec I. The science of autologous fat grafting: views on current and future approaches to neoadipogenesis. Aesthet Surg J 2008;28: Phulpin B, Gangloff P, Tran N, Bravetti P, Merlin JL, Dolivet G. Rehabilitation of irradiated head and neck tissues by autologous fat transplantation. Plast Reconstr Surg 2009;123: Sterodimas A, Huanquipaco JC, de Souza Filho S, Bornia FA, Pitanguy I. Autologous fat transplantation for the treatment of Parry-Romberg syndrome. J Plast Reconstr Aesthet Surg 2009;62:e424-e Coleman SR. Facial augmentation with structural fat grafting. Clin Plast Surg 2006;33:

11 692 Aesthetic Surgery Journal 31(6) 7. Pereira LH, Sterodimas A. Macroscopic and microscopic proof of long-term survival of gluteal fat transplantation. Plast Reconstr Surg 2009;123(4):162e-163e. 8. Kaufman MR, Miller TA, Huang C, et al. Autologous fat transfer for facial recontouring: is there science behind the art? Plast Reconstr Surg 2007;119: Donofrio LM. Techniques in facial fat grafting. Aesthet Surg J 2008;28: Ashjian PH, De Ugarte DA, Katz AJ, Hedrick MH. Lipoplasty: from body contouring to tissue engineering. Aesthet Surg J 2002;22: Sterodimas A, De Faria J, Correa WE, Pitanguy I. Tissue engineering in plastic surgery: an up-to-date review of the current literature. Ann Plast Surg 2009;62: Zuk PA, Zhu M, Mizuno H, et al. Multilineage cells from human adipose tissue: implications for cell-based therapies. Tissue Eng 2001;7: Grimes BR, Steiner CM, Merfeld-Clauss S, et al. Interphase FISH demonstrates that human adipose stromal cells maintain a high level of genomic stability in longterm culture. Stem Cells Dev 2009;18(5): Matsumoto D, Sato K, Gonda K, et al. Cell-assisted lipotransfer: supportive use of human adipose-derived cells for soft tissue augmentation with lipoinjection. Tissue Eng 2006;12: Yoshimura K, Sato K, Aoi N, Kurita M, Hirohi T, Harii K. Cell-assisted lipotransfer for cosmetic breast augmentation: supportive use of adipose-derived stem/stromal cells. Aesthetic Plast Surg 2008;32: Sterodimas A, de Faria J, Nicaretta B, Pitanguy I. Tissue engineering with adipose-derived stem cells (ADSCs): current and future applications. J Plast Reconstr Aesthet Surg 2010;63: Sterodimas A, de Faria J, Nicaretta B, Papadopoulos O, Illouz YG. Cell assisted lipotransfer. Aesthet Surg J 2010;30: Pereira LH, Sterodimas A. Composite body contouring. Aesthetic Plast Surg 2009;33: Pereira LH, Sterodimas A. Transaxillary breast augmentation: a prospective comparison of subglandular, subfascial, and submuscular implant insertion. Aesthetic Plast Surg 2009;33(5): Citarella ER, Sterodimas A, Condé-Green A. Endoscopically assisted limited-incision rhytidectomy: a 10-year prospective study. J Plast Reconstr Aesthet Surg 2010;63: Haroldo Pereira L, Sterodimas A. Aesthetic restoration of axillary contour deformity after lymph node dissection. J Plast Reconstr Aesthet Surg 2008;61(2): Pereira LH, Sterodimas A. Free fat transplantation for the aesthetic correction of mild pectus excavatum. Aesthetic Plast Surg 2008;32: Toledo LS, Mauad R. Fat injection: a 20-year revision. Clin Plast Surg 2006;33: Illouz YG. Present results of fat injection. Aesthetic Plast Surg 1988;12: Billings E Jr, May JW Jr. Historical review and present status of free fat graft autotransplantation in plastic and reconstructive surgery. Plast Reconstr Surg 1989;83: Pu LL. Cryopreservation of adipose tissue. Organogenesis 2009;5: Santana KP, Pereira LH, Sabatovich O, Sterodimas A. Foreign-body granulomas caused by polymethylmethacrylate (PMMA) microspheres: successful correction by autologous fat transplantation. J Plast Reconstr Aesthet Surg 2010;63:e139-e Cherubino M, Marra KG. Adipose-derived stem cells for soft tissue reconstruction. Regen Med. 2009;4: Hamou C, Callaghan MJ, Thangarajah H, et al. Mesenchymal stem cells can participate in ischemic neovascularization. Plast Reconstr Surg. 2009;123(2):45S-55S. 30. Mylotte LA, Duffy AM, Murphy M, et al. Metabolic flexibility permits mesenchymal stem cell survival in an ischemic environment. Stem Cells 2008;26: Kilroy GE, Foster SJ, Wu X, et al. Cytokine profile of human adipose-derived stem cells: expression of angiogenic, hematopoietic, and pro-inflammatory factors. J Cell Physiol 2007;212: Suga H, Eto H, Shigeura T, et al. IFATS series: FGF-2- induced HGF secretion by adipose-derived stromal cells inhibits post-injury fibrogenesis through a JNK-dependent mechanism. Stem Cells 2009;27: Thangarajah H, Vial IN, Chang E, et al. IFATS series: adipose stromal cells adopt a proangiogenic phenotype under the influence of hypoxia. Stem Cells 2009;27: Rehman J, Traktuev D, Li J, et al. Secretion of angiogenic and antiapoptotic factors by human adipose stromal cells. Circulation 2004;109: Ullmann Y, Shoshani O, Fodor A, et al. Searching for the favorable donor site for fat injection: in vivo study using the nude mice model. Dermatol Surg 2005;31: Jurgens WJ, Oedayrajsingh-Varma MJ, Helder MN, et al. Effect of tissue-harvesting site on yield of stem cells derived from adipose tissue: implications for cell-based therapies. Cell Tissue Res 2008;332: Pereira LH, Sterodimas A. Long-term fate of transplanted autologous fat in the face. J Plast Reconstr Aesthet Surg 2010;63:e68-e Rohrich RJ, Sorokin ES, Brown SA. In search of improved fat transfer viability: a quantitative analysis of the role of centrifugation and harvest site. Plast Reconstr Surg 2004;113: Kurita M, Matsumoto D, Shigeura T, et al. Influences of centrifugation on cells and tissues in liposuction aspirates: optimized centrifugation for lipotransfer and cell isolation. Plast Reconstr Surg 2008;121: Kim IH, Yang JD, Lee DG, Chung HY, Cho BC. Evaluation of centrifugation technique and effect of epinephrine on

12 Sterodimas et al 693 fat cell viability in autologous fat injection. Aesthet Surg J 2009;29: Coleman SR. Structural fat grafting. In: Nahai F, ed. The Art of Aesthetic Surgery: Principles and Techniques. St Louis, MO: Quality Medical; 2005: Condé-Green A, Gontijo de Amorim NF, Pitanguy I. Influence of decantation, washing and centrifugation on adipocyte and mesenchymal stem cell content of aspirated adipose tissue: a comparative study. J Plast Reconstr Aesthet Surg 2010;63: