Autologous fat grafting (AFG) is not a new technique. It was first described by Neubar1 in 1893 to fill a depressed facial scar. Used only sparingly for the greater part of the next century, AFG was mostly overlooked in plastic and reconstructive surgery until the early 1980’s. In 1987, as the popularity of AFG surged, the American Society of Plastic and Reconstructive Surgeons issued a position paper on the use of autologous fat grafting in the breast. At the time, they did not condone the use of autologous fat grafting on the grounds that “much of the injected fat will not survive and the known physiological response to necrosis of this tissue is scarring and calcification. As a result, detection of early breast carcinoma through xenography and mammography will become difficult.2,3”
Since 1987, the popularity of fat grafting for a variety of indications has only increased, and a significant body of literature demonstrated that artifacts resulting from fat grafting, mainly calcifications and oil cysts, can be readily differentiated from malignancy in early breast cancer screening.4–9 This is due to improvements in imaging techniques and an expanded body of data on the subject. In 2009, the American Society of Plastic Surgeons published a new position paper evaluating the safety and efficacy of autologous fat grafting. The American Society of Plastic Surgeons task force determined that autologous fat grafting was a safe procedure with a relatively low rate of complications. In addition, they stated that artifacts could indeed be identified and distinguished from malignancy in early breast cancer screenings.10
In recent years, AFG has become a widely accepted and utilized technique in the field of plastic surgery due to its application in soft-tissue augmentation and its regenerative effects on local tissue such as reversal of hyperpigmentation, softening of hypertrophic scars, increased local vascularity, and improvement of radiated tissue.11–13 The diverse applications of fat grafting within the field of plastic surgery include facial rejuvenation, hand rejuvenation, breast reconstruction and volume enhancement, treatment of skin photoaging, correction of contour deformities, and improvement of senile and diabetic plantar fat pad atrophy.14–20 AFG is useful for both cosmetic and reconstructive indications because there is no scarring at the injection site, no foreign material implanted, a low rate of serious complications, and a typically desirable donor site.
Despite the beneficial effects, there are some drawbacks associated with AFG. Postfat grafting soft-tissue lesions such as calcifications and oil cysts are observed postoperatively. But it is clear that lesions appearing more than 1 year after fat grafting are not directly related to the procedure.14,21
The most troublesome and persistent issue in fat grafting, however, is the unpredictable degree of volume retention of fat grafts after transplant. Across the literature, studies have reported a wide range of reabsorption rates after transplantation.22 Although some of the variability is no doubt due to inconsistent methods of pre- and postoperative volume assessment used in various clinical studies reported, a lack of predictable volume retention is clearly a characteristic of autologous fat grafting. A better understanding of the fat graft microenvironment in which engraftment occurs is clearly critical to improvement of clinical outcomes. The current state of knowledge of fat graft failure points toward cellular hypoxia as the major factor adversely affecting the engraftment process and thus long-term volume retention. Studies demonstrate that mature adipocytes can tolerate hypoxia for approximately 24 hours at normal core body temperature due to the relatively active metabolic demand of their intracellular cytoplasm. In vivo, fat grafting involves placement of a 1–4 mm diameter adipose tissue fragments, each consisting of thousands of individual cells, into a profoundly ischemic adipose tissue recipient site microenvironment. Ideally, the graft fragment is initially nourished by diffusion of oxygen and glucose from the surrounding tissue and quickly revascularized through microvascular inosculation and neovascularization. The clinical success of fat grafting attests to the efficiency of this revascularization process. A significant proportion of injected fat, however, fails to successfully engraft due to irreversible anoxic injury suffered by adipocytes before revascularization can occur. Passive diffusion of oxygen and glucose is not sufficient to sustain adipocytes located centrally in the individual graft tissue fragment, that is, at a depth of more than about 10 cells from the fragment surface and thus anoxia-induced apoptosis and resorption is the fate of the central core of the graft fragment. Improvement in AFG technique is aimed at reducing the number of mature adipocytes located intermediate between the well-perfused outer cell layers and the anoxic central core of the graft fragment that enter an apoptotic pathway and fail to engraft.23
Studies have improved understanding of the cellular processes affecting the success of fat grafting and offer the possibility of improving the reliability and predictability of fat grafting. This work, for example, revealed hypoxia-induced factors expressed by adipocytes, which are exposed to ischemic conditions. But the identification of an adipose-specific apoptosis pathway induced by hypoxic conditions and which might be affected by changes in operative technique or medication remains an unrealized research goal. Still, it is possible to identify several factors that contribute to high rates of adipocyte apoptosis and ultimately fat graft resorption. These factors include the threshold parameters tolerated by grafted cells to specific hyponutritional microenvironments, anoxia, and physical trauma, which occurs before revascularization. The clinical value of this knowledge is supported by studies that show administration of proangiogenic factors such as erythropoietin and vascular endothelial growth factor improve the survival of transplanted fat tissue in mouse models.24,25 Another salient factor in successful engraftment is the presence of adipose-derived stem cells (ASCs). These cells are pluripotent mesenchymal stem cells that reside in large numbers in adipose tissue. They are concentrated in the stromal vascular fraction (SVF) of lipoaspirate. These small stellate-shaped cells are identified by surface antigens such as CD134 and their ability to form colonies in vitro. It is estimated that 1–3 million of these small stellate-shaped cells typically reside in proximity to small vessels of adipose tissue. Adipose stem cells are known to tolerate the conditions associated with harvest and graft injection more successfully than mature adipocytes, participate in the tissue response to these stresses, and direct adipose tissue regeneration. Importantly, the liposuction fat graft harvest process depletes the number of ASCs in fat graft material.26,27
These observations, and other factors known to affect successful engraftment, suggest several strategies that may be expected to improve volumetric retention by optimizing the processes of fat graft harvest, graft preparation, and the fat graft injection. The most salient factors amenable to adjustment are fat graft particle size, graft physical trauma, graft hypoxic time, number of ASCs in the fat graft material, and the recipient microenvironment. In this article, we review proposed methods to improve the effectiveness of AFG, the relevant basic research basis of the strategy, and the results of the relevant clinical research.
HARVEST, HANDLING, AND GRAFTING TECHNIQUE
Many groups have attempted to determine the optimal techniques for harvest, processing, and transplantation, but there is still no general consensus on the most effective technique. This lack of consensus regarding technique contributes to the wide range of graft retention rates reported across the literature. Part of the problem stems from the fact that AFG actually consists of a multiplicity of individual steps from fat harvest, to graft preparation, to fat injection. Most of the component steps at each stage are likely to substantially affect survival of each small adipose tissue fragment, which constitutes the injected graft, thereby affecting the permanent graft volume. Compounding the problem of controlling these multiple variables in clinical studies is the difficulty of studying the major end point, that is, volume retention. Volumetric measurements, although simpler today with more advanced photographic methods, are notoriously difficult and results are often difficult to compare due to significant differences in both the harvest and recipient site. Nevertheless, there is a significant body of knowledge concerning the factors known to affect graft viability and the engraftment process. These factors fall under graft harvest methods, fat graft processing methods, and grafting technique. They are reviewed below.
Fat Harvest Methods
In 2013, Fisher et al.28 investigated fat harvest techniques used in AFG. They compared fat harvest using either suction-assisted liposuction or ultrasound-assisted liposuction. In terms of graft retention and SVF content, there was no significant difference between the 2 methods. This was reinforced by Chung et al.29 in 2014 who reported no decrease in viability with ultrasound-assisted or suction-assisted liposuction; however, when comparing suction-assisted liposuction with laser-assisted liposuction, they noted that laser-assisted liposuction reduced viability of graft material.
Another factor that was proposed as a point of variance in producing lipoaspirate graft material is the location of harvest. Numerous studies have investigated fat graft characteristics and AFG results based on harvest location. In 2004, Rohrich et al.30 examined fat harvested from 4 body parts: the abdomen, the flank, the thigh, and the medial knee. They determined that there was no significant effect on adipocyte viability or survival based on harvest site. In general, harvest location has not been determined to not be a significant factor in the outcomes of AFG procedures. This information is beneficial because it allows the surgeon more versatility to harvest based on tissue availability and patient aesthetic preferences without compromising the outcomes.
Fat Processing Methods
Fisher et al.28 also compared 3 common processing techniques: filtration, cotton gauze rolling, and centrifugation. In the filtration method, lipoaspirate is passed through an 800 µm filter. In the centrifugation method, often referred to as the Coleman technique, lipoaspirate is centrifuged at 3,000 rpm for 3 minutes. The adipose layer is then separated from the aqueous and oil layers. In the cotton gauze rolling method, fat is gently rolled on a nonadherent cotton gauze dressing for 5 minutes using a sterile scalpel to remove the liquid portions. When grafted, the cotton gauze method was reported to have the highest volume retention compared with the other methods, with 70% retention. The filtration method retained 58% and the centrifugation method retained only 47%. Fisher et al.28 suggested that cotton-gauze was the preferred method for cosmetically sensitive parts of the body where less fat is required, but filtration and centrifugation were more practical options for large volumes.
No strict recommendation can be made about the best processing technique for AFG based on the literature. Various individual studies have found different methods to be superior depending on the protocols used in each study.31 However, there are common trends and observations reported across many studies. One observation is that grafts prepared using simple decantation contained the highest number of viable adipocytes, but also the highest number of contaminants. Additionally, grafts prepared using centrifugation at a speed above 400 g have decreased viability of adipocytes.
PLATELET RICH PLASMA
A method receiving a significant amount of attention for its potential to improve volumetric retention of fat grafts is the supplementation of graft tissue with autologous platelet-rich plasma (PRP). PRP is a growth factor–rich injectable that can be generated quickly and cost effectively from a patient’s own blood. Over 800 different proteins have been identified to be secreted by platelets into the plasma, which affect a wide range of cells in the body.32
Platelets are a vital part of the immune system response to endothelial injury. Platelets, normally inactive, become activated when they come in contact with damaged endothelial tissue and can also be quickly activated in vitro by contact with glass, freezing cycles, or the addition of calcium or thrombin. Once activated, platelets release stores of growth factors that facilitate tissue repair. Growth factor secretion is most intense in the first hour but continues for about 7 days.33 The growth factors synthesized by platelets stimulate healing and tissue repair through intercellular mediators and cytokines that stimulate angiogenesis and promote cell proliferation, cell differentiation, and extracellular matrix formation.34–36 Although synthetic forms of these growth factors have been previously studied, they are more readily available and more easily acquired for clinical use in the form of autologous PRP. PRP has been used over the last 30 years to promote bone regeneration, wound healing, tendon and cartilage repair, corneal repair, and skin rejuvenation.37–42 It should, however, be noted that results across different applications of PRP can sometimes be difficult to compare. This is because since the 1970’s a variety of different methods have been used to prepare PRP, leading to significant variation in the composition and outcomes.43,44
In terms of improving fat grafting, PRP has multiple potential beneficial qualities. The growth factor stores in PRP allow cells to resist the hypoxic stress experienced within the first few days after fat transfer and promote proper arrangement of transplanted tissue by facilitating production of the extracellular matrix. The growth factors in PRP also promote angiogenesis, which facilitates recovery from the ischemia associated with fat transfer. PRP has been shown to improve fat survival rate and promote stem cell proliferation and differentiation in vitro.45,46
Numerous animal studies have shown a positive relationship between PRP-enhancement and fat graft survival. A study published by Nakamura et al.47 in 2010 demonstrated that fat grafts enhanced with PRP retained significantly more volume than nonenhanced fat grafts in rats. A similar result was achieved by Pires Fraga et al.48 in 2010 using rabbits, demonstrating greater volume retention and blood vessel formation and less necrosis and fibrosis. A study by Rodríguez-Flores et al.49 in 2011 compared the histological characteristics of grafted tissue with and without PRP in rabbits. They noted that when PRP was included, there was less inflammation observed in the recipient site, fewer instances of oil cyst formation, and increased survival of transplanted fat cells.
Recently, additional studies have examined clinical applications of PRP-enhanced fat grafting for wound healing, facial reconstruction, and general aesthetic improvements.50 Studies have demonstrated that the application of SVF and PRP have similar effectiveness in the treatment of posttraumatic lower extremity ulcers and facial scars.51,52
In 2012, Gentile et al.53 published clinical results of a study comparing PRP-enhanced AFG and normal AFG in breast reconstruction. They observed that after 1 year, the PRP-enhanced group (n = 50) retained 69% of the initial 3-dimensional volume, whereas the control group (normal AFG, n = 50) retained only 39%. In 2013, the same group published another article expanding on their results with the procedure they termed Platelet-rich Lipotransfer.54 They observed that when using a PRP concentration of 0.5 mL or 0.4 mL of PRP per mL of fat tissue, 70% of the initial volume was retained at 1 year, compared with only 31% in the control group.
RECIPIENT SITE IMMOBILIZATION WITH NEUROTOXIN
An interesting approach proposed by Baek et al.55 in 2012 suggested that enhancement of fat grafts with Botulinum Toxin A (BoNTA) could improve fat graft survival in the facial region, and they tested this theory in a rat model. Fat was excised from the rat retroperitoneal area and then digested with collagenase for 2 hours to create a homogenate. This homogenized fat mixture was then centrifuged to remove the fluid components and used for grafting. In each rat, Baek et al.55 grafted 2 separate tissue deposits, 1 on each side of the back. One of these grafts was injected with fat, saline and BoNTA (0.5 IU), whereas the other received only fat and saline. Baek et al.55 observed a significant increase in the weight, volume, and cellular integrity of the graft which received BoNTA compared with the control graft. They reported 74% volume retention of the initial 0.5 mL of fat tissue grafted in the BoNTA group and only 44% in the control group.
The authors proposed that the increased retention was due to temporary muscle immobilization provided by the BoNTA, which decreases abnormal muscle contractions in the face and preserves graft viability. For the cosmetic treatment of facial aging, BoNTA injections to the face are commonly performed shortly before or after facial fat grafting procedures are conducted.56 This method proposed by Baek et al.55 seeks to consolidate these 2 into 1 procedure for patient convenience and potentially improved results. However, more clinical evidence is required to validate this technique in humans.
ADIPOSE-DERIVED STEM CELLS AND CELL-ASSISTED LIPOTRANSFER
In 2006, the research team led by Yoshimura et al. published an article in which they described a method of supplementing the lipoaspirate used for fat grafting with progenitor cells found in adipose tissue, adipose-derived stem cells (ASCs).58 They termed this process cell-assisted lipotransfer (CAL).57 The rationale behind this technique is that aspirated adipose tissue (lipoaspirate) is generally poor in progenitor cells, which is a contributing factor to poor survival in vivo. Lipoaspirate is poor in progenitor cells for 2 main reasons. The first is that ASCs tend to be located closer to major blood vessels in adipose tissue which are avoided during liposuction and other harvest techniques.26,27 The second reason is that a portion of the progenitor cells are contained in the fluid portion of the lipoaspirate, which is discarded before grafting.58 To combat this problem, Yoshimura et al. suggested harvesting excess lipoaspirate and isolating the progenitor cells contained within, which then can be used to supplement the lipoaspirate to create a progenitor-rich graft.26,27,58
Adipose-derived stem cells have many characteristics which aid in the retention of fat grafts. First, ASCs are able to differentiate into new adipocytes, replacing a portion of the adipocytes, which succumb to apoptosis due to hypoxic or physical stress.59–61 Second, ASCs have been shown to actively promote angiogenesis via growth factor secretion and through neovascular differentiation.62,63 ASCs have been shown to not only survive in hypoxic conditions, but actually significantly increase their production of soluble angiogenic growth factors, including vascular endothelial growth factor and hepatocyte growth factor.64,65 By promoting the development of new vasculature in the grafted tissue, ASCs are able to speed the recovery from ischemia after transplantation and reduce the number of cells succumbing to hypoxic stress, thereby improving graft volume retention.
Studies have been conducted using both the SVF and pure, cultured populations of ASCs. SVF is a heterogeneous population of cells that results from the processing of adipose tissue and is composed mainly of various blood cells, pericytes, macrophages, smooth muscle cells, and both adipose-derived and vascular endothelial progenitor cells.66 The use of a pure population of ASCs was not shown to be superior to using SVF cells. Using SVF cells is advantageous because they do not require culturing, which can take weeks. Instead, these cells can be isolated and injected in the same surgical procedure. Using cultured cells would require 2 procedures: 1 to harvest cells and 1 for the actual grafting. In the initial article describing CAL, they reported a 35% increase in retention of grafted tissue volume compared with normal fat grafting in a mouse model. This has led to many projects investigating the therapeutic potential of CAL. In 2013, Kølle et al.67 conducted a randomized placebo-controlled trial to investigate the effects of ASC enhancement on graft survival in humans. Using cultured ASCs, Kølle et al.67 reported significantly higher levels of volume retention compared with controls. The ASC-enhanced group retained 80.9% of the initial volume on average, compared with the control group which only retained 16.3% on average. Another study by Wang et al.68 published in 2012 reported CAL results from 18 patients. They reported retention of only about 50% of the grafted tissue at 6 months. Although there is still absorption of a significant portion of fat after grafting, studies on CAL have reported a positive correlation with ASC enhancement and volume retention compared with normal AFG, but how much the retention is improved is still debated, and no conclusive dose versus effect relationship has been established.69
The main application of CAL in the clinical setting has been for cosmetic breast augmentation and reconstruction, but with these recent advances in the field of AFG, essentially all previous applications of fat grafting are now being reinvestigated using CAL, including the treatment of lipodystrophy and contour defects, reduction of facial aging, and accelerated healing of chronic wounds, among others.
CAL AND PRP IN COMBINATION
The independent advances observed with both PRP and ASC enrichment of fat grafts naturally led to the attempt to combine the 2. PRP has been shown to increase the proliferation and differentiation of ASC in vitro.70,71 By supplementing ASC enhanced fat grafting (CAL) with PRP, researchers and clinicians hope to boost the regenerative effects of the stem cells, while still getting the benefit afforded by PRP enhancement, to achieve a method superior to supplementation with either alone.
In a recent study by Seyhan et al.,72 each of these 3 methods (ASC only, PRP only, and ASC + PRP) were compared in rats. They reported that after 12 weeks the PRP + ASC group had the highest weight and volume of fat grafts while also having the highest number of viable adipocytes and blood vessels. Growth factor levels were also the highest in the PRP + ASC group. While in vitro and animal studies are promising, there is relatively no clinical data available on the combination of the 2, most likely because of the lack of adequate clinical data on the use of ASCs alone. Studies have shown that the injection of ASC combined with PRP accelerated wound closure rates in patients with chronic skin ulcers, but the individual contributions of ASC and PRP to wound closure and their possible synergism has not yet been elucidated.73 There are also studies which examine the combination of PRP and ASCs in areas outside of fat grafting, such as improvement of knee joint function.74
Fat grafting continues to increase in popularity with new indications and novel technical modifications reported frequently. AFG helps augment and regenerate deficient, scarred, irradiated and aged subcutaneous soft tissue, and skin in a wide variety of clinical situations with a low complication rate and low donor-site morbidity. However, there is still no clinically vetted ideal technique that ensures maximum graft survival and predictability of lasting graft volume. There is currently no consensus on the optimal autologous fat grafting technique that produces the most predictable outcome for a given clinical situation. Unlike most operations, successful fat engraftment does not occur at the macroscopic tissue level, and tissue viability can not be assessed by more familiar parameters such as color, warmth, tension, and bleeding. Now plastic surgeons are compelled to delve to the level of very small tissue fragments and even individual cells which are affected by such novel factors as local oxygen tension, glucose concentration, micro physical stress, ambient temperature effects on cellular metabolism, and the like. But just as improved tissue rearrangement procedures using muscle flaps emerged from an improved understanding of the axial blood supply, it is expected that improved AFG outcomes will result from meticulous attention to the factors which affect viability of small fat tissue fragments and cells.
Studies have been conducted to examine if using PRP, ASC, or a combination of both will help combat the low fat graft retention rates, but no ideal method has been determined. Although there is some anecdotal evidence, more clinical evidence is required to validate the best technique to ensure the volumetric retention of adipose tissue after autologous fat grafting. Future research will hopefully refine our understanding of the effect of fat grafting on the local tissue micro-environment and provide clues toward its optimization. Correlating laboratory results with large-scale, controlled studies using human patients is needed to advance our ability to tailor fat grafting techniques to specific medical and cosmetic applications. Based on the results of cell biology research and the long-term accumulation of objective patient data, we believe that a standard technique of fat grafting for a given clinical scenario will emerge.
1. Neubar GA. Verhandlugen der Deutschen Gesellschaftfür Chirurgie. 1893;1:German)66 (
2. Delay E, Garson S, Tousson G, et al. Fat injection to the breast: technique, results, and indications based on 880 procedures over 10 years. Aesthet Surg J. 2009;29:360–376.
3. Report on autologous fat transplantation ASPRS Ad-Hoc committee on new procedures. Plast Surg Nurs. 1987;7:140–141.
4. Veber N, Prévost G, Planchon P, et al. Evidence for a growth effect of epidermal growth factor on MDA-MB-231 breast cancer cells. Eur J Cancer. 1994;30A:1352–1359.
5. Nagashima T, Suzuki M, Yagata H, et al. Cytomorphometric differentiation of intraductal proliferative breast lesions. Breast Cancer. 2000;7:43–47.
6. Rubin JP, Coon D, Zuley M, et al. Mammographic changes after fat transfer to the breast compared with changes after breast reduction: a blinded study. Plast Reconstr Surg. 2012;129:1029–1038.
7. Fiaschetti V, Pistolese CA, Fornari M, et al. Magnetic resonance imaging and ultrasound evaluation after breast autologous fat grafting combined with platelet-rich plasma. Plast Reconstr Surg. 2013;132:498e–509e.
8. Parikh RP, Doren EL, Mooney B, et al. Differentiating fat necrosis from recurrent malignancy in fat-grafted breasts: an imaging classification system to guide management. Plast Reconstr Surg. 2012;130:761–772.
9. Kneeshaw PJ, Turnbull LW, Smith A, et al. Dynamic contrast enhanced magnetic resonance imaging aids the surgical management of invasive lobular breast cancer. Eur J Surg Oncol. 2003;29:32–37.
10. Gutowski KA; ASPS Fat Graft Task Force. Current applications and safety of autologous fat grafts: a report of the ASPS fat graft task force. Plast Reconstr Surg. 2009;124:272–280.
11. Sultan SM, Stern CS, Allen RJ Jr, et al. Human fat grafting alleviates radiation skin damage in a murine model. Plast Reconstr Surg. 2011;128:363–372.
12. Silva VZ, Neto AA, Horácio GS, et al. Evidences of autologous fat grafting for the treatment of keloids and hypertrophic scars. Rev Assoc Med Bras (1992). 2016;62:862–866.
13. Garza R, Paik K, Ching M, et al. Studies in fat grafting: part III. Fat grafting irradiated tissue: improved skin quality and decreased fat graft retention. Plast Reconstr Surg. 2015;134:249–257.
14. Groen JW, Krastev TK, Hommes J, et al. Autologous fat transfer for facial rejuvenation: a systematic review on technique, efficacy, and satisfaction. Plast Reconstr Surg Glob Open. 2017;5:e1606.
15. Marten TJ, Elyassnia D. Fat grafting in facial rejuvenation. Clin Plast Surg. 2015;42:219–252.
16. Hoang D, Orgel MI, Kulber DA. Hand rejuvenation: a comprehensive review of fat grafting. J Hand Surg Am. 2016;41:639–644.
17. Kao WP, Lin YN, Lin TY, et al. Microautologous fat transplantation for primary augmentation rhinoplasty: long-term monitoring of 198 Asian patients. Aesthet Surg J. 2016;36:648–656.
18. Trivisonno A, Rossi A, Monti M, et al. Facial skin rejuvenation by autologous dermal microfat transfer in photoaged patients: clinical evaluation and skin surface digital profilometry analysis. J Plast Reconstr Aesthet Surg. 2017;70:1118–1128.
19. Luu CA, Larson E, Rankin TM, et al. Plantar fat grafting and tendon balancing for the diabetic foot ulcer in remission. Plast Reconstr Surg Glob Open. 2016;4:e810.
20. Chairman EL. Restoration of the plantar fat pad with autolipotransplantation. J Foot Ankle Surg. 1994;33:373–379.
21. Illouz YG, Sterodimas A. Autologous fat transplantation to the breast: a personal technique with 25 years of experience. Aesthetic Plast Surg. 2009;33:706–715.
22. Gir P, Brown SA, Oni G, et al. Fat grafting: evidence-based review on autologous fat harvesting, processing, reinjection, and storage. Plast Reconstr Surg. 2012;130:249–258.
23. Suga H, Eto H, Aoi N, et al. Adipose tissue remodeling under ischemia: death of adipocytes and activation of stem/progenitor cells. Plast Reconstr Surg. 2010;126:1911–1923.
24. Hamed S, Egozi D, Kruchevsky D, et al. Erythropoietin improves the survival of fat tissue after its transplantation in nude mice. PLoS One. 2010;5:e13986.
25. Zhang Y, Xiao LL, Li JX, et al. Improved fat transplantation survival by using the conditioned medium of vascular endothelial growth factor transfected human adipose-derived stem cells. Kaohsiung J Med Sci. 2017;33:379–384.
26. Yoshimura K, Sato K, Aoi N, et al. Cell-assisted lipotransfer for cosmetic breast augmentation: supportive use of adipose-derived stem/stromal cells. Aesthetic Plast Surg. 2008;32:48–55; discussion 56.
27. Yoshimura K, Suga H, Eto H. Adipose-derived stem/progenitor cells: roles in adipose tissue remodeling and potential use for soft tissue augmentation. Regen Med. 2009;4:265–273.
28. Fisher C, Grahovac TL, Schafer ME, et al. Comparison of harvest and processing techniques for fat grafting and adipose stem cell isolation. Plast Reconstr Surg. 2013;132:351–361.
29. Chung MT, Zimmermann AS, Paik KJ, et al. Isolation of human adipose-derived stromal cells using laser-assisted liposuction and their therapeutic potential in regenerative medicine. Stem Cells Transl Med. 2013;2:808–817.
30. 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;113:391–395; discussion 396.
31. Gupta R, Brace M, Taylor SM, et al. In search of the optimal processing technique for fat grafting. J Craniofac Surg. 2015;26:94–99.
32. Macaulay IC, Carr P, Gusnanto A, et al. Platelet genomics and proteomics in human health and disease. J Clin Invest. 2005;115:3370–3377.
33. Senzel L, Gnatenko DV, Bahou WF. The platelet proteome. Curr Opin Hematol. 2009;16:329–333.
34. Rubina K, Kalinina N, Efimenko A, et al. Adipose stromal cells stimulate angiogenesis via promoting progenitor cell differentiation, secretion of angiogenic factors, and enhancing vessel maturation. Tissue Eng Part A. 2009;15:2039–2050.
35. Kakudo N, Minakata T, Mitsui T, et al. Proliferation-promoting effect of platelet-rich plasma on human adipose-derived stem cells and human dermal fibroblasts. Plast Reconstr Surg. 2008;122:1352–1360.
36. Anitua E, Andía I, Sanchez M, et al. Autologous preparations rich in growth factors promote proliferation and induce VEGF and HGF production by human tendon cells in culture. J Orthop Res. 2005;23:281–286.
37. Marx RE, Carlson ER, Eichstaedt RM, et al. Platelet-rich plasma: growth factor enhancement for bone grafts. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1998;85:638–646.
38. Lacci KM, Dardik A. Platelet-rich plasma: support for its use in wound healing. Yale J Biol Med. 2010;83:1–9.
39. Yuan T, Zhang CQ, Wang JH. Augmenting tendon and ligament repair with platelet-rich plasma (PRP). Muscles Ligaments Tendons J. 2013;3:139–149.
40. Alio JL, Abad M, Artola A, et al. Use of autologous platelet-rich plasma in the treatment of dormant corneal ulcers. Ophthalmology. 2007;114:1286–1293.e1.
41. Kim DH, Je YJ, Kim CD, et al. Can platelet-rich plasma be used for skin rejuvenation? Evaluation of effects of platelet-rich plasma on human dermal fibroblast. Ann Dermatol. 2011;23:424–431.
42. Kon E, Filardo G, Di Matteo B, et al. PRP for the treatment of cartilage pathology. Open Orthop J. 2013;7:120–128.
43. Dhurat R, Sukesh M. Principles and methods of preparation of platelet-rich plasma: a review and author’s perspective. J Cutan Aesthet Surg. 2014;7:189–197.
44. Mazzocca AD, McCarthy MB, Chowaniec DM, et al. Platelet-rich plasma differs according to preparation method and human variability. J Bone Joint Surg Am. 2012;94:308–316.
45. Eppley BL, Woodell JE, Higgins J. Platelet quantification and growth factor analysis from platelet-rich plasma: implications for wound healing. Plast Reconstr Surg. 2004;114:1502–1508.
46. Li F, Guo W, Li K, et al. Improved fat graft survival by different volume fractions of platelet-rich plasma and adipose-derived stem cells. Aesthet Surg J. 2015;35:319–333.
47. Nakamura S, Ishihara M, Takikawa M, et al. Platelet-rich plasma (PRP) promotes survival of fat-grafts in rats. Ann Plast Surg. 2010;65:101–106.
48. Pires Fraga MF, Nishio RT, Ishikawa RS, et al. Increased survival of free fat grafts with platelet-rich plasma in rabbits. J Plast Reconstr Aesthet Surg. 2010;63:e818–e822.
49. Rodríguez-Flores J, Palomar-Gallego MA, Enguita-Valls AB, et al. Influence of platelet-rich plasma on the histologic characteristics of the autologous fat graft to the upper lip of rabbits. Aesthetic Plast Surg. 2011;35:480–486.
50. Cervelli V, Palla L, Pascali M, et al. Autologous platelet-rich plasma mixed with purified fat graft in aesthetic plastic surgery. Aesthetic Plast Surg. 2009;33:716–721.
51. Cervelli V, Gentile P, De Angelis B, et al. Application of enhanced stromal vascular fraction and fat grafting mixed with PRP in post-traumatic lower extremity ulcers. Stem Cell Res. 2011;6:103–111.
52. Gentile P, De Angelis B, Pasin M, et al. Adipose-derived stromal vascular fraction cells and platelet-rich plasma: basic and clinical evaluation for cell-based therapies in patients with scars on the face. J Craniofac Surg. 2014;25:267–272.
53. Gentile P, Orlandi A, Scioli MG, et al. A comparative translational study: the combined use of enhanced stromal vascular fraction and platelet-rich plasma improves fat grafting maintenance in breast reconstruction. Stem Cells Transl Med. 2012;1:341–351.
54. Cervelli V, Bocchini I, Di Pasquali C, et al. P.R.L. platelet rich lipotransfert: our experience and current state of art in the combined use of fat and PRP. Biomed Res Int. 2013;2013:434191.
55. Baek RM, Park SO, Jeong EC, et al. The effect of botulinum toxin A on fat graft survival. Aesthetic Plast Surg. 2012;36:680–686.
56. Wise JB, Greco T. Injectable treatments for the aging face. Facial Plast Surg. 2006;22:140–146.
57. 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;12:3375–3382.
58. Yoshimura K, Shigeura T, Matsumoto D, et al. Characterization of freshly isolated and cultured cells derived from the fatty and fluid portions of liposuction aspirates. J Cell Physiol. 2006;208:64–76.
59. Eto H, Kato H, Suga H, et al. The fate of adipocytes after nonvascularized fat grafting: evidence of early death and replacement of adipocytes. Plast Reconstr Surg. 2012;129:1081–1092.
60. Kato H, Araki J, Doi K, et al. Normobaric hyperoxygenation enhances initial survival, regeneration, and final retention in fat grafting. Plast Reconstr Surg. 2014;134:951–959.
61. Scott MA, Nguyen VT, Levi B, et al. Current methods of adipogenic differentiation of mesenchymal stem cells. Stem Cells Dev. 2011;20:1793–1804.
62. Baraniak PR, McDevitt TC. Stem cell paracrine actions and tissue regeneration. Regen Med. 2010;5:121–143.
63. Cao Y, Sun Z, Liao L, et al. Human adipose tissue-derived stem cells differentiate into endothelial cells in vitro
and improve postnatal neovascularization in vivo. Biochem Biophys Res Commun. 2005;332:370–379.
64. Lee EY, Xia Y, Kim WS, et al. Hypoxia-enhanced wound-healing function of adipose-derived stem cells: increase in stem cell proliferation and up-regulation of VEGF and bFGF. Wound Repair Regen. 2009;17:540–547.
65. Tsuji W, Rubin JP, Marra KG. Adipose-derived stem cells: implications in tissue regeneration. World J Stem Cells. 2014;6:312–321.
66. Zuk PA, Zhu M, Ashjian P, et al. Human adipose tissue is a source of multipotent stem cells. Mol Biol Cell. 2002;13:4279–4295.
67. Kølle SF, Fischer-Nielsen A, Mathiasen AB, et al. Enrichment of autologous fat grafts with ex-vivo expanded adipose tissue-derived stem cells for graft survival: a randomised placebo-controlled trial. Lancet. 2013;382:1113–1120.
68. Wang L, Lu Y, Luo X, et al. [Cell-assisted lipotransfer for breast augmentation: a report of 18 patients]. Zhonghua Zheng Xing Wai Ke Za Zhi. 2012;28:1–6.
69. Paik KJ, Zielins ER, Atashroo DA, et al. Studies in fat grafting: part V. Cell-assisted lipotransfer to enhance fat graft retention is dose dependent. Plast Reconstr Surg. 2015;136:67–75.
70. Atashi F, Serre Beinier V, Nayernia Z, et al. Platelet rich plasma promotes proliferation of adipose derived mesenchymal stem cells via activation of AKT and Smad2 signaling pathways. J Stem Cell Res Ther. 2015;5: 301.
71. Van Pham P, Bui KH, Ngo DQ, et al. Activated platelet-rich plasma improves adipose-derived stem cell transplantation efficiency in injured articular cartilage. Stem Cell Res Ther. 2013;4:91.
72. Seyhan N, Alhan D, Ural AU, et al. The effect of combined use of platelet-rich plasma and adipose-derived stem cells on fat graft survival. Ann Plast Surg. 2015;74:615–620.
73. Raposio E, Bertozzi N, Bonomini S, et al. Adipose-derived stem cells added to platelet-rich plasma for chronic skin ulcer therapy. Wounds. 2016;28:126–131.
74. Pak J, Lee JH, Lee SH. A novel biological approach to treat chondromalacia patellae. PLoS One. 2013;8:e64569.