A Murine Model for Studying Diffusely Injected Human Fat:

Autologous Conditioned Serum Increases Fat Graft Viability More than Platelet-Rich Plasma in a Controlled Rat Model

BACKGROUND

Platelet-rich plasma has been used to support fat graft retention, but it may include inflammatory mediators such as interleukin-1β. Autologous conditioned serum also contains high levels of various anti-inflammatory cytokines. The authors hypothesized that combining autologous conditioned serum with fat graft would increase fat graft survival more than platelet-rich plasma.

METHODS

Twenty-seven adult, male, Sprague-Dawley rats were divided into three groups of nine. Ten nonstudy rats were used to prepare platelet-rich plasma, autologous conditioned serum, and fat grafts. Next, 0.7-ml fat graft with a combination of 0.2 ml of autologous conditioned serum, platelet-rich plasma, or phosphate-buffered saline was applied to their dorsa. Fat graft volume was assessed on postoperative day 2 and on the day of euthanization at 1, 3, and 5 months postoperatively. Histopathologic analysis was performed to measure integrity, inflammation, fibrosis, and vascularization.

RESULTS

The median volume percentages and interquartile ranges at 1 month postoperatively were 97.3 percent (77.3 to 119.6 percent), 40.4 percent (30.9 to 46.9 percent), and 72.1 percent (53.6 to 84.9 percent) in autologous conditioned serum plus fat graft, phosphate-buffered saline plus fat graft, and platelet-rich plasma plus fat graft, respectively (p < 0.05); at 3 months postoperatively, values were 82.3 percent (70.3 to 88.3 percent), 36.6 percent (29.4 to 43.1 percent), and 48.3 percent (31.4 to 57.9 percent) (p < 0.001); and at 5 months postoperatively, values had increased to 83.9 percent (58.3 to 102.4 percent), 40.3 percent (20.1 to 50.6 percent), and 56.3 percent (37.7 to 74.9 percent), respectively (p < 0.05).

CONCLUSIONS

Autologous conditioned serum and platelet-rich plasma improved fat graft outcomes compared to saline, whereas autologous conditioned serum was associated with less inflammation, greater fat viability, and more integrity.

CLINICAL RELEVANCE STATEMENT

Combining fat graft with autologous conditioned serum may be a better option to minimize resorption rate and improve graft survival.

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.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Blood Impairs Viability of Fat Grafts and Adipose Stem Cells: Importance of Washing in Fat Processing

BACKGROUND

Fat processing plays a pivotal role in graft survival. Each component of the blood in lipoaspirate affects fat survival in different ways, but the mechanisms are not clear.

OBJECTIVES

The aim of this study was to investigate, by various experimental methods, the effect of blood on the viability of fat grafts and adipose stem cells (ASCs).

METHODS

Blood and fat samples were obtained from 6 female patients undergoing aesthetic liposuction. For the in vivo experiment, we compared fat mixed with normal saline or various ratios of blood in nude mice. The samples were explanted at 2 and 8 weeks to evaluate the gross volume retention and histologic and immunohistochemical characteristics. For in vitro experiments, ASCs were pretreated with hemoglobin at different concentrations and for different times. We then assessed the proliferation, migration, adipogenesis, and reactive oxygen species production of ASCs.

RESULTS

Blood in the graft led to a decrease in graft viability, as evaluated by general observation and histologic and immunohistochemical morphology in vivo. In vitro experiments showed inhibited proliferation, migration, and adipogenesis, and increased reactive oxygen species production in ACSs, after hemoglobin treatment, suggesting impaired ASC viability.

CONCLUSIONS

This study suggests that blood impairs the viability of fat grafts and ASCs and provides evidence that washing to remove blood is important in fat processing.

Therapeutic Reversal of Radiotherapy Injury to Pro-fibrotic Dysfunctional Fibroblasts In Vitro Using Adipose-derived Stem Cells

Cancer patients often require radiotherapy (RTx) to enhance their survival. Unfortunately, RTx also damages nearby healthy non-cancer tissues, leading to progressive fibrotic soft-tissue injury, consisting of pain, contracture, tissue-breakdown, infection, and lymphoedema. Mechanisms underlying the clinically observed ability of fat grafting to ameliorate some of these effects, however, are poorly understood. It was hypothesized that RTx significantly alters fibroblast cell function and the paracrine secretome of adipose-derived stem cells (ADSC) may mitigate these changes.

Methods

To investigate cellular changes resulting in the fibrotic side-effects of RTx, cultured normal human dermal fibroblasts (NHDF) were irradiated (10Gy), then studied using functional assays that reflect key fibroblast functions, and compared with unirradiated controls. RNA-Seq and targeted microarrays (with specific examination of TGFβ) were performed to elucidate altered gene pathways. Finally, conditioned-media from ADSC was used to treat irradiated fibroblasts and model fat graft surgery.

Results

RTx altered NHDF morphology, with cellular functional changes reflecting transition into a more invasive phenotype: increased migration, adhesion, contractility, and disordered invasion. Changes in genes regulating collagen and MMP homeostasis and cell-cycle progression were also detected. However, TGFβ was not identified as a key intracellular regulator of the fibroblast response. Finally, treatment with ADSC-conditioned media reversed the RTx-induced hypermigratory state of NHDF.

Conclusions

Our findings regarding cellular and molecular changes in irradiated fibroblasts help explain clinical manifestations of debilitating RTx-induced fibrosis. ADSC-secretome-mediated reversal indicated that these constituents may be used to combat the devastating side-effects of excessive unwanted fibrosis in RTx and other human fibrotic diseases.

Fat Therapeutics: The Clinical Capacity of Adipose-Derived Stem Cells and Exosomes for Human Disease and Tissue Regeneration

Fat grafting is a well-established surgical technique used in plastic surgery to restore deficient tissue, and more recently, for its putative regenerative properties. Despite more frequent use of fat grafting, however, a scientific understanding of the mechanisms underlying either survival or remedial benefits of grafted fat remain lacking. Clinical use of fat grafts for breast reconstruction in tissues damaged by radiotherapy first provided clues regarding the clinical potential of stem cells to drive tissue regeneration. Healthy fat introduced into irradiated tissues appeared to reverse radiation injury (fibrosis, scarring, contracture and pain) clinically; a phenomenon since validated in several animal studies. In the quest to explain and enhance these therapeutic effects, adipose-derived stem cells (ADSCs) were suggested as playing a key role and techniques to enrich ADSCs in fat, in turn, followed. Stem cells - the body's rapid response 'road repair crew' - are on standby to combat tissue insults. ADSCs may exert influences either by releasing paracrine-signalling factors alone or as cell-free extracellular vesicles (EVs, exosomes). Alternatively, ADSCs may augment vital immune/inflammatory processes; or themselves differentiate into mature adipose cells to provide the 'building-blocks' for engineered tissue. Regardless, adipose tissue constitutes an ideal source for mesenchymal stem cells for therapeutic application, due to ease of harvest and processing; and a relative abundance of adipose tissue in most patients. Here, we review the clinical applications of fat grafting, ADSC-enhanced fat graft, fat stem cell therapy; and the latest evolution of EVs and nanoparticles in healing, cancer and neurodegenerative and multiorgan disease.

Role of Fat Graft Alone versus Enriched Fat Graft with Stromal Vascular Filtrate in Painful Amputation Stump

BACKGROUND

Traumatic amputations are very prevalent in today's world. Successful rehabilitation of an amputee largely depends on how well he/she adapt to prosthesis. However, because of poor scar characteristics, these patients often complain of pain while using prosthesis. Autologous fat graft is being vastly used all over the world to improve the scar of various etiologies. However, it has been associated with unpredictable resorption rate.

OBJECTIVES

We report the results of the study which was done to assess the consequences of fat grafting over scars and to see its effects on pain management in amputated stump and compare the autologous fat graft with stromal vascular filtrate (SVF)-enriched fat graft for scar remodeling and pain modulation on amputation stumps.

MATERIALS AND METHODS

A prospective randomized trial was conducted from July 2014 to December 2015. A group of ten patients, who were unable to wear prosthesis due to painful amputation stump, incorporated in the study and randomly distributed in two groups. Group A of five patients (case group) was treated with autologous fat graft enriched with SVF while Group B (control group) of remaining five patients was treated with fat graft alone. The results were assessed at baseline, at 1 month, and at 6 months postoperatively using patient and observer scar assessment scale (POSAS) score. Magnetic resonance imaging (MRI) was done to compare fat content preoperatively and 6 months postoperatively.

RESULTS

All ten patients reported improvement in scar characteristics, most notably in pain in both scales of POSAS score. The improvement was comparable in both groups. However, the fat content in case group was significantly more in comparison to control group when assessed 6 months postoperatively using MRI scan.

CONCLUSION

Autologous fat grafting is a viable and minimally invasive solution for painful amputation stump. Enrichment of fat graft with SVF can enhance its viability over long term. This study was done as a pilot project. Hence, further long term studies with large sample size are needed to ascertain the benefits observed in this study.

Preclinical Optimization of a Shelf-Ready, Injectable, Human-Derived, Decellularized Allograft Adipose Matrix

IMPACT STATEMENT

Trauma, disease, surgery, or congentital defects can cause soft tissue losses in patients, leading to disfigurement, functional impairment, and a low quality of life. In the lack of available effective methods to reconstruct these defects, acellular adipose matrices could provide a novel therapeutic solution to such challenge.

Effect of Cryopreservation on Human Adipose Tissue and Isolated Stromal Vascular Fraction Cells: In Vitro and In Vivo Analyses

BACKGROUND

Adipose tissue is a source of adipose-derived stromal/stem cells for tissue engineering and reconstruction and a tissue source for fat grafts. Although liposuction is a simple procedure for the harvest of adipose tissue, the repetition of this surgical intervention can cause adverse effects to the patient and can be a limiting factor for immediate use. Cryopreservation can avoid the morbidity associated with repetitive liposuction, allowing the use of stored tissue after the initial harvest procedure. This article focuses on the characterization of fresh and cryopreserved human adipose tissue.

METHODS

Lipoaspirates from eight donors were processed as fresh adipose tissue or cryopreserved for 4 to 6 weeks. Fresh and cryopreserved tissues were collagenase digested and the stromal vascular fraction cells were characterized immediately or cryopreserved. Characterization was based on stromal vascular fraction cell proliferation and immunophenotype. In vivo fat grafting was performed in C57BL/6 green fluorescent protein mice to analyze morphology of the tissue and its adiposity using confocal microscopy, histochemical staining (i.e., hematoxylin and eosin and Masson trichrome), and immunohistochemistry (i.e., green fluorescent protein, perilipin, and CD31).

RESULTS

Although tissue and stromal vascular fraction cell cryopreservation reduced the total cell yield, the remaining viable cells retained their adhesive and proliferative properties. The stromal vascular fraction cell immunophenotype showed a significant reduction in the hematopoietic surface markers and increased expression of stromal and adipogenic markers following cryopreservation. In vivo cryopreserved fat grafts showed morphology similar to that of freshly implanted fat grafts.

CONCLUSION

In this study, the authors demonstrated that cryopreserved adipose tissue is a potential source of stromal vascular fraction cells and a suitable source for fat grafts.

Experimental In-Vivo Models Used in Fat Grafting Research for Volume Augmentation in Soft Tissue Reconstruction

As the popularity of fat grafting research increases, animal models are being used as the source of pre-clinical experimental information for discovery and to enhance techniques. To date, animal models used in this research have not been compared to provide a standardized model. We analyzed publications from 1968–2015 to compare published accounts of animal models in fat grafting research. Data collected included: species used, graft characteristics (donor tissue, recipient area, amount injected, injection technique), time of sacrifice and quantification methods. Mice were most commonly used (56% of studies), with the “athymic nude” strain utilized most frequently (44%). Autologous fat was the most common source of grafted tissue (52%). Subcutaneous dorsum was the most common recipient site (51%). On average, 0.80±0.60 mL of fat was grafted. A single bolus technique was used in 57% of studies. Fat volume assessment was typically completed at the end of the study, occurring at less than 1 week to one year. Graft volume was quantified by weight (63%), usually in conjunction with another analysis. The results demonstrate the current heterogeneity of animal models in this research. We propose that the research community reach a consensus to allow better comparison of techniques and results. One example is the model used in our laboratory and others; this model is described in detail. Eventually, larger animal models may better translate to the human condition but, given increased financial costs and animal facility capability, should be explored when data obtained from small animal studies is exhausted or inconclusive.

Scar Tissue Causing Saphenous Nerve Entrapment: Percutaneous Scar Release and Fat Grafting

Painful neuropathies can be caused by nerve compression or neuromas. Nerve compressions can arise from scar adhesions causing painful posttraumatic entrapment of nerve branches via fibrosis. The classical treatment methods include neurolysis and nerve transposition. In this case, we present the treatment of recurrent scar entrapment of the saphenous nerve with percutaneous neurolysis and lipofilling in a patient who had previously undergone an open neurolysis procedure. Resolution of the condition without any complications was noted during the 2-month clinical follow-up. Percutaneous neurolysis and lipofilling are shown to be safe and reproducible methods for the treatment of neuropathic compressive scars.

Literature Review to Optimize the Autologous Fat Transplantation Procedure and Recent Technologies to Improve Graft Viability and Overall Outcome: A Systematic and Retrospective Analytic Approach

OBJECTIVE

Investigation and evaluation of the current methods and steps of autologous fat transplantation to optimize the viability of fat grafts and procedure outcome in quest of a more standardized protocol.

METHODS

A thorough literature search was performed across the CNKI, Wan Fang, PubMed, Ovid and EMBASE databases from the year 1970 to December 2014, collecting and classifying all of the autologous fat transplantation-related reports and articles, and after screening, a critical retrospective analysis was performed on the included data.

RESULTS

A total of 65 articles were included in the study. However, there were limited numbers of cases dealing with procedure-related steps such as the selection of donor sites, fat acquisition, graft treatment and methodology of transplant, resulting in a significant lack of evidence support, furthermore urging the need for more standardized protocol for the steps of autologous fat transplant to improve graft viability and overall outcome while decreasing procedure-related morbidity.

CONCLUSION

No good evidence was obtained to optimize the donor site, acquisition, processing and transplantation steps of the whole process of autologous fat transplantation. Tissue engineering and stem cell research have the potential to revolutionize the future of reconstructive surgery by replacing tissue, obviating the need for donor site morbidity. However, the use of stem cell therapies to expand and grow tissue for reconstruction must occur in the context of risk management. Balancing ease of harvest with yield and efficacy has been a delicate and often difficult trade-off which has prompted the scientific community to investigate alternative sources. However, there is much hope in the evaluation and implementation of multimodality approaches for autologous fat transplant, including thriving technologies such as ultrasound-assisted, water jet-assisted, nanotechnology-assisted liposuction in combination with revolutionary fat treatment technologies such as the VASER system.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Autologous fat grafting: current state of the art and critical review

BACKGROUND

Despite the widespread use of autologous fat grafting in both reconstructive and cosmetic surgery, volume retention remains a significant problem. We aimed to critically appraise the current body of literature in fat grafting to provide a framework to guide application and comparison.

METHOD

Search of scientific databases and gray literature was conducted. Articles examining nonadipogenic applications of adipose tissue and those specific to breast reconstruction were excluded.

RESULTS

One hundred three articles were included. These fell under the headings of donor site, effect of infiltration solution, harvest method, effect of centrifugation, reinjection method, supplementation, the role of adipose-derived stem cells, and scaffolding.

CONCLUSIONS

Despite the significant research effort in this field, there remains no consensus as to the optimum technique. This stems from the vast array of research methods and short follow-up durations. Further, extrapolation of in vitro results to clinical settings has led to many conflicting practices.

Power-assisted gluteal augmentation: a new technique for sculpting, harvesting, and transferring fat

BACKGROUND

A simple and reproducible surgical technique for gluteal shaping and augmentation with autologous fat is needed.

OBJECTIVES

The authors describe a novel approach to large-volume gluteal augmentation that combines power-assisted liposculpting and fat harvesting of the zones around the buttock with autologous fat transfer.

METHODS

One hundred ten patients who underwent gluteal augmentation were evaluated in a prospective study. Liposculpting and fat harvesting were performed with power-assisted liposuction. Fat then was transferred to the gluteal region with simultaneous power-assisted vibration and tunnelization. A questionnaire to assess patient satisfaction was administered at 6 months postoperatively.

RESULTS

The mean body mass index of the patients was 30 kg/m(2) (range, 26-36 kg/m(2)). Liposuction volumes ranged from 1400 to 5000 mL, and injection volumes ranged from 300 to 900 mL per side for each session. Operating times ranged from 60 to 120 minutes. Patients were monitored for an average of 20 months (range 12-48 months). Complications included a burning sensation in 5 of 110 patients (4.5%), persistent swelling in the lower back in 3 patients (2.7%), and a mild infection in 1 patient (0.9%).

CONCLUSIONS

Power-assisted gluteal augmentation with autologous fat is an efficient, safe, and reproducible procedure that produces an aesthetically pleasing gluteal projection and contour.

LEVEL OF EVIDENCE

4 Therapeutic.

Immediate Large-Volume Grafting of Autologous Fat to the Breast Following Implant Removal

BACKGROUND

To optimize autologous breast augmentation, a simple and reproducible surgical approach that maximizes the volume of fat transferred to the breast while minimizing the number of sessions and the operating time is needed.

OBJECTIVES

The authors describe a novel approach for large-volume fat grafting to the expanded skin and subcutaneous tissue of the breast immediately after explantation, exchanging the volume provided by the implants with transplanted fat in a single session.

METHODS

Eighty patients (160 breasts) undergoing explantation and autologous fat transfer were evaluated in a prospective study. Fat was harvested with the lipomatic power-assisted liposuction machine (Lipomatic Eva SP, Euromi SA, Verviers, Belgium) and was injected with simultaneous vibration and tunnelization of the recipient site by means of the same machine with suction disabled. Changes in breast volume were measured in terms of bra cup size, and patients were monitored by mammography and ultrasonography. Patient satisfaction was assessed with a questionnaire administered 6 months postoperatively.

RESULTS

Injected fat volumes ranged from 300 to 600 mL per breast. Operating times ranged from 45 to 90 minutes. For all patients, one injection session was sufficient to replace the volume of the previous implant. Patients were monitored for an average of 2 years, and complications included cyst formation in 9 of 160 breasts (5.6%) and infection in 2 breasts (1.25%).

CONCLUSIONS

Power-assisted transfer of autologous fat to the breast improves the ability of the recipient site to receive the graft and allows for explantation and fat transplantation in a single session. This approach is suitable for patients who desire a natural-appearing breast that is similar in volume to their previous implant.

Targeted protection of donor graft vasculature using a phosphodiesterase inhibitor increases survival and predictability of autologous fat grafts

BACKGROUND

Fat grafting is limited by unpredictable long-term graft retention. The authors postulate that injury to the donor-derived microvasculature during harvest and subsequent ischemia may account for this clinical variability. They examined the use of the U.S. Food and Drug Administration-approved phosphodiesterase-5 inhibitor sildenafil citrate to protect graft microvasculature and its role in revascularization and survival.

METHODS

Inguinal fat of donor Tie2/LacZ mice was infiltrated with sildenafil or saline, harvested, and transplanted onto the dorsa of recipient FVB mice. Additional donor mice were perfused with intraarterial trypsin to inactivate the fat graft microvasculature before harvest and transplantation. Differences in graft revascularization, perfusion, volume of retention, and biochemical changes were assessed.

RESULTS

Surviving fat grafts were characterized by exclusively donor-derived vasculature inosculating with the recipient circulation at the graft periphery. Inactivation of donor-derived microvasculature decreased early graft perfusion and led to nearly total graft loss by 8 weeks. Sildenafil attenuated vascular ischemic injury, consistent with reductions in VCAM-1 and SDF1α expression at 48 hours and 4-fold increases in microvasculature survival by 2 weeks over controls. Compared with controls, targeted sildenafil treatment improved early graft perfusion, doubled graft retention at 12 weeks (83 percent versus 39 percent; p < 0.05), ultimately retaining 64 percent of the original graft volume by 24 weeks (compared to 4 percent; p < 0.05) with superior histologic features.

CONCLUSIONS

Fat graft vascularization is critically dependent on maintenance of the donor microvasculature. Sildenafil protects the donor microvasculature during transfer and revascularization, increasing long-term volume retention. These data demonstrate a rapidly translatable method of increasing predictability and durability of fat grafting in clinical practice.

Magnetic Resonance Imaging of Human Tissue-Engineered Adipose Substitutes

Adipose tissue (AT) substitutes are being developed to answer the strong demand in reconstructive surgery. To facilitate the validation of their functional performance in vivo, and to avoid resorting to excessive number of animals, it is crucial at this stage to develop biomedical imaging methodologies, enabling the follow-up of reconstructed AT substitutes. Until now, biomedical imaging of AT substitutes has scarcely been reported in the literature. Therefore, the optimal parameters enabling good resolution, appropriate contrast, and graft delineation, as well as blood perfusion validation, must be studied and reported. In this study, human adipose substitutes produced from adipose-derived stem/stromal cells using the self-assembly approach of tissue engineering were implanted into athymic mice. The fate of the reconstructed AT substitutes implanted in vivo was successfully followed by magnetic resonance imaging (MRI), which is the imaging modality of choice for visualizing soft ATs. T1-weighted images allowed clear delineation of the grafts, followed by volume integration. The magnetic resonance (MR) signal of reconstructed AT was studied in vitro by proton nuclear magnetic resonance ((1)H-NMR). This confirmed the presence of a strong triglyceride peak of short longitudinal proton relaxation time (T1) values (200 ± 53 ms) in reconstructed AT substitutes (total T1=813 ± 76 ms), which establishes a clear signal difference between adjacent muscle, connective tissue, and native fat (total T1 ~300 ms). Graft volume retention was followed up to 6 weeks after implantation, revealing a gradual resorption rate averaging at 44% of initial substitute's volume. In addition, vascular perfusion measured by dynamic contrast-enhanced-MRI confirmed the graft's vascularization postimplantation (14 and 21 days after grafting). Histological analysis of the grafted tissues revealed the persistence of numerous adipocytes without evidence of cysts or tissue necrosis. This study describes the in vivo grafting of human adipose substitutes devoid of exogenous matrix components, and for the first time, the optimal parameters necessary to achieve efficient MRI visualization of grafted tissue-engineered adipose substitutes.

Adipose-derived stem cells in radiotherapy injury: a new frontier

Radiotherapy is increasingly used to treat numerous human malignancies. In addition to the beneficial anti-cancer effects, there are a series of undesirable effects on normal host tissues surrounding the target tumor. While the early effects of radiotherapy (desquamation, erythema, and hair loss) typically resolve, the chronic effects persist as unpredictable and often troublesome sequelae of cancer treatment, long after oncological treatment has been completed. Plastic surgeons are often called upon to treat the problems subsequently arising in irradiated tissues, such as recurrent infection, impaired healing, fibrosis, contracture, and/or lymphedema. Recently, it was anecdotally noted - then validated in more robust animal and human studies - that fat grafting can ameliorate some of these chronic tissue effects. Despite the widespread usage of fat grafting, the mechanism of its action remains poorly understood. This review provides an overview of the current understanding of: (i) mechanisms of chronic radiation injury and its clinical manifestations; (ii) biological properties of fat grafts and their key constituent, adipose-derived stem cells (ADSCs); and (iii) the role of ADSCs in radiotherapy-induced soft-tissue injury.

Assessment of viability of human fat injection into nude mice with micro-computed tomography

Lipotransfer is a vital tool in the surgeon's armamentarium for the treatment of soft tissue deficits of throughout the body. Fat is the ideal soft tissue filler as it is readily available, easily obtained, inexpensive, and inherently biocompatible.(1) However, despite its burgeoning popularity, fat grafting is hampered by unpredictable results and variable graft survival, with published retention rates ranging anywhere from 10-80%. (1-3) To facilitate investigations on fat grafting, we have therefore developed an animal model that allows for real-time analysis of injected fat volume retention. Briefly, a small cut is made in the scalp of a CD-1 nude mouse and 200-400 µl of processed lipoaspirate is placed over the skull. The scalp is chosen as the recipient site because of its absence of native subcutaneous fat, and because of the excellent background contrast provided by the calvarium, which aids in the analysis process. Micro-computed tomography (micro-CT) is used to scan the graft at baseline and every two weeks thereafter. The CT images are reconstructed, and an imaging software is used to quantify graft volumes. Traditionally, techniques to assess fat graft volume have necessitated euthanizing the study animal to provide just a single assessment of graft weight and volume by physical measurement ex vivo. Biochemical and histological comparisons have likewise required the study animal to be euthanized. This described imaging technique offers the advantage of visualizing and objectively quantifying volume at multiple time points after initial grafting without having to sacrifice the study animal. The technique is limited by the size of the graft able to be injected as larger grafts risk skin and fat necrosis. This method has utility for all studies evaluating fat graft viability and volume retention. It is particularly well-suited to providing a visual representation of fat grafts and following changes in volume over time.

The effects of platelet-rich plasma on recovery time and aesthetic outcome in facial rejuvenation: preliminary retrospective observations

BACKGROUND

This study focused on the possible effect of platelet-rich plasma (PRP) on recovery time and aesthetic outcome after facial rejuvenation. We conducted a retrospective analysis with regard to recovery time and the aesthetic improvement after treatment among four groups of patients: those treated with fat grafting only (Group I), those treated with fat grafting and PRP (Group II), those treated with a minimal access cranial suspension (MACS)-lift and fat grafting (Group III), and those treated with a MACS-lift, fat grafting, and PRP (Group IV).

METHODS

For the first part of this study, i.e., evaluation of recovery time after surgery, the following selection criteria were used: nonsmoking females, aged 35-65 years, with a complete documented follow-up. In total, 82 patients were included in the evaluation of patient-reported recovery time. For the second part of the study, i.e., evaluation of potential differences in aesthetic outcome, the records of these 82 patients were screened for the presence of pre- and postoperative standardized photographs in three views (AP, lateral, and oblique), leaving 37 patients to evaluate. A questionnaire was developed to evaluate the aesthetic outcome in all four groups of patients. This questionnaire was given to an expert panel that consisted of ten plastic surgeons.

RESULTS

The addition of PRP to a lipofilling procedure resulted in a significant drop in the number of days needed to recover before returning to work or to restart social activities [Group I (no PRP) took 18.9 days vs Group II (PRP) took 13.2 days, p = 0.019]. There seemed to be no effect when PRP was added to a MACS-lift + lipofilling procedure. Also, the aesthetic outcome of the lipofilling and MACS-lift + lipofilling groups that received PRP (Groups II and IV) was significantly better than the groups without PRP (Groups I and III).

CONCLUSIONS

Adding PRP to facial lipofilling reduces recovery time and improves the overall aesthetic outcome of a MACS-lift.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Fat Ful'fill'ment: A Review of Autologous Fat Grafting

For more than a century, clinicians have attempted to utilise fat for the treatment of tissue deficiencies and contour abnormalities. Autologous fat transplantation for soft-tissue augmentation has become increasingly popular in recent years. The popularity of tumescent liposuction has brought renewed interest and accessibility of fat for transplantation. Newer techniques and approaches to augmentation have provided more predictable and reproducible results. Fat augmentation has become an effective, safe and reliable method for restoring volume and correcting the atrophy that accompanies senescence. In this review, the authors have described their approach to fat transplantation.

Grading lipoaspirate: is there an optimal density for fat grafting?

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-1α, 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.

Micro-computed tomography evaluation of human fat grafts in nude mice

BACKGROUND

Although autologous fat grafting has revolutionized the field of soft tissue reconstruction and augmentation, long-term maintenance of fat grafts is unpredictable. Recent studies have reported survival rates of fat grafts to vary anywhere between 10% and 80% over time. The present study evaluated the long-term viability of human fat grafts in a murine model using a novel imaging technique allowing for in vivo volumetric analysis.

METHODS

Human fat grafts were prepared from lipoaspirate samples using the Coleman technique. Fat was injected subcutaneously into the scalp of 10 adult Crl:NU-Foxn1(nu) CD-1 male mice. Micro-computed tomography (CT) was performed immediately following injection and then weekly thereafter. Fat volume was rendered by reconstructing a three-dimensional (3D) surface through cubic-spline interpolation. Specimens were also harvested at various time points and sections were prepared and stained with hematoxylin and eosin (H&E), for macrophages using CD68 and for the cannabinoid receptor 1 (CB1). Finally, samples were explanted at 8- and 12-week time points to validate calculated micro-CT volumes.

RESULTS

Weekly CT scanning demonstrated progressive volume loss over the time course. However, volumetric analysis at the 8- and 12-week time points stabilized, showing an average of 62.2% and 60.9% survival, respectively. Gross analysis showed the fat graft to be healthy and vascularized. H&E analysis and staining for CD68 showed minimal inflammatory reaction with viable adipocytes. Immunohistochemical staining with anti-human CB1 antibodies confirmed human origin of the adipocytes.

CONCLUSIONS

Studies assessing the fate of autologous fat grafts in animals have focused on nonimaging modalities, including histological and biochemical analyses, which require euthanasia of the animals. In this study, we have demonstrated the ability to employ micro-CT for 3D reconstruction and volumetric analysis of human fat grafts in a mouse model. Importantly, this model provides a platform for subsequent study of fat manipulation and soft tissue engineering.

Perineural fat grafting in the treatment of painful end-neuromas of the upper limb: a pilot study

The purpose of this study was to evaluate the effectiveness and middle-term durability of the results achieved with perineural fat grafting of painful neuromas of the upper limb. We retrospectively analysed eight patients, affected by eight neuromas, treated by neuroma excision and fat grafting around the proximal nerve stump. Clinical parameters, the disabilities of the arm shoulder and hand score, and the visual analogue scale were recorded at 2, 6 and 12 months after surgery. A reduction of 23.2% was observed in the mean disabilities of the arm shoulder and hand scores at 12 months. The spontaneous baseline visual analogue scale score showed a mean improvement of 22% at 12 months, although not this was not statistically significant. Perineural fat grafting is a quick and useful procedure and could represent a useful primary operation in the treatment of pain syndromes of neuropatic origin.

The effect of hyaluronan hydrogel on fat graft survival

BACKGROUND

Autologous fat transplantation is a common technique for soft tissue augmentation in aesthetic and reconstructive surgery; however, the degree of fat graft take can be unpredictable. Hyaluronan has been shown to be a promising cell carrier in adipose tissue engineering.

OBJECTIVES

The authors investigate the effect of a hyaluronan hydrogel on fat graft survival, angiogenesis, and volume maintenance in a rat model.

METHODS

Fat was harvested from the groins of 27 rats, processed, and injected beneath the animals' dorsums to form 2 grafts: 1 containing fat alone and 1 containing fat and hyaluronan hydrogel in a 1:1 mix (fat-HA). The grafts were scanned in vivo under high-resolution computed tomography at baseline and prior to euthanasia at 4, 12, and 20 weeks to measure total fat-HA graft volume as well as the volume of the fat component alone. Histological studies were performed after sacrifice to evaluate fat necrosis and blood vessel density.

RESULTS

All grafts were clinically viable. Overall, fat necrosis was significantly reduced in the fat-HA grafts compared with the grafts containing fat alone (P < .001). This difference was most profound at 4 weeks (P = .008) but did not reach statistical significance at 12 and 20 weeks. At 12 weeks, blood vessel density in the fat-HA grafts was significantly greater than in the grafts containing fat alone (P = .016), but this did not reach statistical significance at 4 or 20 weeks. At 20 weeks, the fat component of the fat-HA graft had significantly less volume loss than the fat-alone graft (P = .008).

CONCLUSIONS

When mixed with fat, hyaluronan hydrogel can improve early fat graft survival and may enhance vascularity and prolong volume maintenance.

Perineural fat grafting in the treatment of painful neuromas

Treatment of painful neuromas of the upper limb has been largely debated. The current surgical treatments spare from simple neuroma excision to proximal nerve stump relocation (into muscles, veins, and bones). Perineural fat grafting consists of neuroma excision and the creation of an autologous adipose graft wrapped around the proximal nerve stump. This technique should be prescribed to those patients suffering from terminal neuromas or neuromas in which functional reconstruction is contraindicated. The effectiveness of this technique could be addressed both to the mechanical and biological properties of the fat graft. On one hand the graft creates a gliding layer and a protective barrier, thus allowing longitudinal excursion and protection against mechanical solicitations. On the other hand the autologous adipose tissue brings neoangiogenesis, modulates the inflammatory response, and avoids scar adherences. A retrospective analysis was performed on 7 neuromas in 7 patients, treated with perineural fat grafting from June 2009 to February 2010. Pain and limb functionality were measured, respectively, with a visual acuity scale and the "Disabilities of the Arm, Shoulder, and Hand score," preoperatively and 1 year after surgery. A mean pain reduction of 23% was recorded, without relevant complications. Improvements in limb functionality were also observed through the measurement of the Disabilities of the Arm, Shoulder, and Hand score, which improved to 18%. We believe that this technique represents a valuable and versatile option in the treatment of painful neuromas of the upper limb that could be hereafter performed for pain syndromes of neuropatic origin.

Autologous stem cells for personalised medicine

Increasing understanding of stem cell biology, the ability to reprogramme differentiated cells to a pluripotent state and evidence of multipotency in certain adult somatic stem cells has opened the door to exciting therapeutic advances as well as a great deal of regulatory and ethical issues. Benefits will come from the possibility of modelling human diseases and develop individualised therapies, and from their use in transplantation and bioengineering. The use of autologous stem cells is highly desirable, as it avoids the problem of tissue rejection, and also reduces ethical and regulatory issues. Identification of the most appropriate cell sources for different potential applications, development of appropriate clinical grade methodologies and large scale well controlled clinical trials will be essential to assess safety and value of cell based therapies, which have been generating much hope, but are by and large not yet close to becoming standard clinical practice. We briefly discuss stem cells in the context of tissue repair and regenerative medicine, with a focus on individualised clinical approaches, and give examples of sources of autologous cells with potential for clinical intervention.

Adipose stem cell-based soft tissue regeneration

INTRODUCTION

Since their isolation and characterization nearly a decade ago, adipose-derived stem cells (ASCs) have become one of the most popular adult stem cell populations for research in soft tissue engineering and regenerative medicine applications. Compared with other stem cell sources, ASCs offer several advantages including an abundant autologous source, minor invasive harvesting (liposuction), significant proliferative capacity in culture and multi-lineage potential. Numerous preclinical studies have been pursued, with early clinical data appearing in the literature.

AREAS COVERED

Autologous fat grafting has gained tremendous momentum in clinical practice over the past several years due to its potential applications in trauma and reconstructive surgery. This review focuses on the published clinical and pre-clinical (i.e., animal) data to date using ASCs for soft tissue reconstruction, with particular attention to experimental models and methodologies. Future directions for rendering soft tissue reconstructive therapies more effective are discussed.

EXPERT OPINION

Although standardization of ASC harvesting and processing techniques, as well as long-term results of existing clinical studies, remains to be addressed, the known biological properties of ASCs suggest a potential role in enhancing fat graft retention and facilitating minimally invasive reconstructive treatments. While clinical applications are being reported, well controlled clinical studies are needed to demonstrate safety and efficacy.

Human fat grafting alleviates radiation skin damage in a murine model

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 depilated. The dorsal skin was then distracted away from the body and irradiated (45 Gy). Four weeks after irradiation, 1.5-cc fat or sham grafts were placed in the dorsal subcutaneous space. Gross results were analyzed photometrically. The animals were euthanized at 4 and 8 weeks after fat or sham grafting and their dorsal skin was processed for histologic analysis.

RESULTS

Hyperpigmentation and ulceration were grossly improved in fat-grafted mice compared with sham-grafted controls. This improvement manifested histologically in a number of ways. For example, epidermal thickness measurements demonstrated decreased thickness in fat-grafted animals at both time points (20.6 ± 1.5 μm versus 55.2 ± 5.6 μm, p = 0.004; 17.6 ± 1.1 μm versus 36.3 ± 6.1 μm, p = 0.039). Picrosirius red staining demonstrated a diminished scar index in fat-treated animals at both time points as well (0.54 ± 0.05 versus 0.74 ± 0.07, p = 0.034; and 0.55 ± 0.06 versus 0.93 ± 0.07, p = 0.001).

CONCLUSION

Fat grafting attenuates inflammation in acute radiodermatitis and slows the progression of fibrosis in chronic radiodermatitis.

Fat grafting accelerates revascularisation and decreases fibrosis following thermal injury

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°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.