Cryopreservation of human fat for soft tissue augmentation: viability requires use of cryoprotectant and controlled freezing and storage

The Effect of Various Temperatures on the Inflammatory Profile of Fat Graft Storage: An Experimental Study

Fat tissue has been widely used as a filler material during plastic surgery, but unpredictable fat retention remains a significant concern. Fat tissue is vulnerable to ischemia and hypoxia, but it always has waiting time before injection in the operation theater. Apart from transferring fat tissue as quickly as possible after harvesting, washing the aspirate with cool normal saline is often used. However, the mechanisms of cool temperature acting on adipose tissue have yet to be fully elucidated. Herein, this study aims to explore the effect of preservation at different temperatures on the inflammatory profile of adipose tissue. Inguinal adipose tissue of rats was collected and cultured in vitro under 4°C, 10°C, and room temperature for 2 hours. The proportion of damaged adipocytes and an array of cytokines were determined. We observed that the damage rate of the adipocyte membrane was slightly higher at room temperature, but there was no significant difference, while we noticed increased IL-6 and MCP-1 levels in adipose tissue at room temperature ( P ＜0.01). The 4°C and 10°C cool temperatures may offer protection against proinflammatory states during the adipose tissue preserved in vitro.

Characterization of Human Subcutaneous Adipose Tissue and Validation of the Banking Procedure for Autologous Transplantation

Adipose tissue (AT) is composed of a heterogeneous population which comprises both progenitor and differentiated cells. This heterogeneity allows a variety of roles for the AT, including regenerative functions. In fact, autologous AT is commonly used to repair soft tissue defects, and its cryopreservation could be a useful strategy to reduce the patient discomfort caused by multiple harvesting procedures. Our work aimed to characterize the cryopreserved AT and to validate its storage for up to three years for clinical applications. AT components (stromal vascular fraction-SVF and mature adipocytes) were isolated in fresh and cryopreserved samples using enzymatic digestion, and cell viability was assessed by immunofluorescence (IF) staining. Live, apoptotic and necrotic cells were quantified using cytometry by evaluating phosphatidylserine binding to fluorescent-labeled Annexin V. A multiparametric cytometry was also used to measure adipogenic (CD34+CD90+CD31-CD45-) and endothelial (CD34+CD31+CD45-) precursors and endothelial mature cells (CD34-CD31+CD45-). The maintenance of adipogenic abilities was evaluated using in vitro differentiation of SVF cultures and fluorescent lipid staining. We demonstrated that AT that is cryopreserved for up to three years maintains its differentiation potential and cellular composition. Given our results, a clinical study was started, and two patients had successful transplants without any complications using autologous cryopreserved AT.

How to maintain and transport equine adipose tissue for isolating mesenchymal stem cells?

BACKGROUND

Adipose tissue (AT) is one of the most important mesenchymal stem cell (MSC) sources because of its high quantities, availability and ease of collection. After being collected samples, they should be transported to a laboratory for stem cell (SC) isolation, culture and expansion for future clinical application. Usually, laboratories are distant from animal husbandry centers; therefore, it is necessary to provide suitable conditions for adipose tissue transportation, such that adipose-derived MSCs are minimally affected. In the current study, the impact of tissue maintenance under different conditions on MSCs derived from these tissues was evaluated. We aimed at finding suitable and practical transportation methods in which ASCs go through the slightest changes.

RESULTS

In the current study, after being collected, equine AT was randomized into eight groups: four samples were maintained in stem cell culture media at 25 ^οC and 4 ^οC for 6 and 12 hrs. as transportation via SC media groups. Three samples were frozen at three different temperatures (- 20, - 75 and - 196 ^οC) as cryopreserved groups; these samples were defrosted 1 week after cryopreservation. Fresh and unfrozen AT was evaluated as a control group. The tissue samples were then initiated into enzymatic digestion, isolation and the culturing of SCs. Cells at passage three were used to evaluate the ability to form colonies, proliferation rate, plotting of the cell growth curve, and viability rate. All experiments were performed in triplicate. Stem cell isolation was successful in all groups, although purification of SCs from the first series of cryopreservation at - 196 ^οC and two series of - 20 ^οC was unsuccessful. There was no significant difference between the surface area of colonies in all groups except for - 20 ^οC. The growth rate of transportation via stem cell media at 25 ^οC for 6 hrs. was similar to that of the control group. MTT analysis revealed a significant difference between 25 ^οC 12 hrs. Group and other experimental groups except for control, 4 ^οC 12 hrs. and - 196 ^οC group.

CONCLUSION

Data have shown freezing at - 75 ^οC, transportation via stem cell media at 4 ^οC for 12 hrs. and 25 ^οC for 6 hrs. are acceptable tissue preservation and transportation methods due to minor effects on MSCs features.

Sequential Grafting of Fresh and Cryopreserved Fat After Mechanical Processing is a Safe and Effective Facial Rejuvenation Strategy

BACKGROUND

The survival rate of fat transplants is variable and consequently multiple operations are often required to achieve satisfactory results. Fat cryopreservation technology is a good solution to this problem. At present, cryopreservation of fats needs to be added with cryopreservation agents, which brings unsafety and operational complexity to clinical applications. An efficient and safe strategy for fat cryopreservation must be developed.

METHODS

A retrospective study was performed of all patients who underwent facial fat grafting and agreed to have their fat tissue cryopreserved from January 2018 to May 2021. Fat samples were physically processed to obtain SVF-gel, which was cryopreserved at - 20 °C for up to 3 months and injected after thawing. Images acquired by pre- and post-operative 3D scanning of the temporal region were compared to evaluate the retention rate of transplanted cryopreserved SVF-gel.

RESULTS

No patients experienced serious complications after receiving cryopreserved fat transplantation. The retention rate of cryopreserved SVF-gel was 46.3 ± 7.7% at 3 months and 43.1 ± 7.2% at 6 months after transplantation. The swelling duration was significantly shorter after cryopreserved SVF-gel transplantation (5.5 ± 0.8 days) than after fresh fat transplantation (7.5 ± 0.7 days) (p < .031).

CONCLUSION

Injection of cryopreserved SVF-gel achieves good retention rate for facial rejuvenation and has few side effects. Cryopreservation of SVF-gel is a safe and effective strategy for serial fat grafting for facial rejuvenation.

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 .

Oral and Maxillofacial Autologous Fat Transplantation: History, Clinical Application Status and Research Progress

After more than a century of development, autologous fat transplantation (AFT), a repair method for soft tissue defects and deformities, has the advantages of being simple, rapid, effective and safe, and it is increasingly favoured by plastic surgeons. This article reviews the developmental history of AFT, analyses its clinical application status in the oral and maxillofacial regions, and provides a preliminary summary and discussion of the research progress related to AFT. The hope is that that this technique could be widely applied for oral and maxillofacial diseases as well as facial rejuvenation indications. LEVEL OF EVIDENCE III: 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 .

Human ESC-derived MSCs enhance fat engraftment by promoting adipocyte reaggregation, secreting CCL2 and mobilizing macrophages

Mesenchymal stem cells (MSCs) derived from somatic tissues have been used to promote lipotransfer, a common practice in cosmetic surgery. However, the effect of lipotransfer varies, and the mechanism of action remains vague. To address these questions, we differentiated human embryonic stem cells, a stable and unlimited source, into MSCs (EMSCs). Then we subcutaneously transplanted human fat aspirates together with EMSCs or PBS as a control into the back of nude mice. Within 24 h of transplantation, EMSCs promoted aggregation and encapsulation of injected fat tissues. Afterward, all grafts gradually shrank. However, EMSC-containing grafts were larger, heavier and had fewer dark areas on the surface than the control grafts. Histologically, more live adipocytes, vascular cells, and macrophages and less fibrosis were observed in EMSC-containing grafts than in the controls. Some EMSCs differentiated into vascular cells and adipocytes in the EMSC-containing grafts. RNA sequencing revealed that human RNA was shown to decline rapidly, while mouse RNA increased in the grafts; further, human genes related to extracellular matrix remodeling, adipogenesis, and chemokine (including CCL2) signaling were expressed at higher levels in the EMSC-containing grafts than they were in the controls. CCL2 knockout reduced macrophage migration towards EMSCs in vitro and early macrophage recruitment to the grafts and the pro-engraftment effect of EMSCs in vivo. Treating mice with a macrophage inhibitor abolished the EMSC effects and converted the grafts to heavy masses of cell debris. Together, these data demonstrate that EMSCs promote fat engraftment via enhanced tissue reconstitution and encapsulation of implanted tissues, which was followed by increased angiogenesis and adipocyte survival and reduced fibrosis, in which stimulated CCL2 signaling and mobilized macrophages play pivotal roles.

Overview of current adipose-derived stem cell (ADSCs) processing involved in therapeutic advancements: flow chart and regulation updates before and after COVID-19

Adipose-derived stem cells (ADSCs) have raised big interest in therapeutic applications in regenerative medicine and appear to fulfill the criteria for a successful cell therapy. Their low immunogenicity and their ability to self-renew, to differentiate into different tissue-specific progenitors, to migrate into damaged sites, and to act through autocrine and paracrine pathways have been altogether testified as the main mechanisms whereby cell repair and regeneration occur. The absence of standardization protocols in cell management within laboratories or facilities added to the new technologies improved at patient's bedside and the discrepancies in cell outcomes and engraftment increase the limitations on their widespread use by balancing their real benefit versus the patient safety and security. Also, comparisons across pooled patients are particularly difficult in the fact that multiple medical devices are used and there is absence of harmonized assessment assays despite meeting regulations agencies and efficient GMP protocols. Moreover, the emergence of the COVID-19 breakdown added to the complexity of implementing standardization. Cell- and tissue-based therapies are completely dependent on the biological manifestations and parameters associated to and induced by this virus where the scope is still unknown. The initial flow chart identified for stem cell therapies should be reformulated and updated to overcome patient infection and avoid significant variability, thus enabling more patient safety and therapeutic efficiency. The aim of this work is to highlight the major guidelines and differences in ADSC processing meeting the current good manufacturing practices (cGMP) and the cellular therapy-related policies. Specific insights on standardization of ADSCs proceeding at different check points are also presented as a setup for the cord blood and bone marrow.

Cryopreservation of lipoaspirates: in vitro measurement of the viability of adipose-derived stem cell and lipid peroxidation

As the storage time of the fat tissue passes by, lipid peroxidation and creation of by‐products may take place. The objective of this study was to evaluate the cell viability and functional changes of adipose‐derived stem cells (ADSCs) in the cryopreserved lipoaspirates at different temperatures in accordance with lipid peroxidation. Lipoaspirates acquired from liposuction were divided into four different temperature groups and stored at 4°C, −20°C, −80°C, and −196°C. After isolating ADSC from each sample, gross cell morphology and cell viability were compared with doubling time and colony‐forming unit (CFU) formation ability. Acid value, that is, thiobarbituric acid value was measured to assess lipid peroxidation. No viable ADSC was observed in −20°C and −196°C samples for past 1 week and a superior number of the live cells were detected in the 4°C group compared with the −80°C group. However, the persistence of cell division and CFU formation after 1 week was only observed in adipocytes stored at −80°C. Lipid peroxidation mainly occurred at 4°C and −20°C storage samples. If the lipoaspirates were planned to be cryopreserved, it is advised to store at −80°C. However, the number of actually functional ADSCs is very low. Furthermore, even in the cryopreserved status, continuous lipid peroxidation and by‐product creation took place, suggesting shorter preservation period as possible in the clinics.

An Update on Cryopreservation of Adipose Tissue

Currently, fat transplantation occurs immediately after harvesting procedures. Because low rates of fat graft take are well reported in the literature, many patients require multiple surgical procedures for fat graft harvest. These subsequent procedures lead to increased cost, donor-site morbidity, and patient discomfort in the long term. The ability to preserve our patients' own adipose aspirate would allow us to counteract these shortcomings and ultimately improve the clinical outcome after fat grafting. Unfortunately, there is no optimal and practical adipose tissue cryopreservation protocol for use by the plastic surgeon at the present time. Because of this dilemma, the senior author (L.L.Q.P.) has investigated this concept in an effort to create a protocol that is both technically sound and clinically achievable to allow for the long-term preservation of adipose tissue. In this article, the authors aim to outline this effort, review current clinical applications that have been reported in the literature, and detail exciting future perspectives in the use of preserved lipoaspirates for repeated fat grafting procedures or in the form of cell-based therapy engineered for reconstructive endeavors for their patients.

Isolation of Adipose-Derived Stem/Stromal Cells from Cryopreserved Fat Tissue and Transplantation into Rats with Spinal Cord Injury

Adipose tissue contains multipotent cells known as adipose-derived stem/stromal cells (ASCs), which have therapeutic potential for various diseases. Although the demand for adipose tissue for research use remains high, no adipose tissue bank exists. In this study, we attempted to isolate ASCs from cryopreserved adipose tissue with the aim of developing a banking system. ASCs were isolated from fresh and cryopreserved adipose tissue of rats and compared for proliferation (doubling time), differentiation capability (adipocytes), and cytokine (hepatocyte growth factor and vascular endothelial growth factor) secretion. Finally, ASCs (2.5 × 10⁶) were intravenously infused into rats with spinal cord injury, after which hindlimb motor function was evaluated. Isolation and culture of ASCs from cryopreserved adipose tissue were possible, and their characteristics were not significantly different from those of fresh tissue. Transplantation of ASCs derived from cryopreserved tissue significantly promoted restoration of hindlimb movement function in injured model rats. These results indicate that cryopreservation of adipose tissue may be an option for clinical application.

Adipose Derived-Mesenchymal Stem Cells Viability and Differentiating Features for Orthopaedic Reparative Applications: Banking of Adipose Tissue

Osteoarthritis is characterized by loss of articular cartilage also due to reduced chondrogenic activity of mesenchymal stem cells (MSCs) from patients. Adipose tissue is an attractive source of MSCs (ATD-MSCs), representing an effective tool for reparative medicine, particularly for treatment of osteoarthritis, due to their chondrogenic and osteogenic differentiation capability. The treatment of symptomatic knee arthritis with ATD-MSCs proved effective with a single infusion, but multiple infusions could be also more efficacious. Here we studied some crucial aspects of adipose tissue banking procedures, evaluating ATD-MSCs viability, and differentiation capability after cryopreservation, to guarantee the quality of the tissue for multiple infusions. We reported that the presence of local anesthetic during lipoaspiration negatively affects cell viability of cryopreserved adipose tissue and cell growth of ATD-MSCs in culture. We observed that DMSO guarantees a faster growth of ATD-MSCs in culture than trehalose. At last, ATD-MSCs derived from fresh and cryopreserved samples at -80°C and -196°C showed viability and differentiation ability comparable to fresh samples. These data indicate that cryopreservation of adipose tissue at -80°C and -196°C is equivalent and preserves the content of ATD-MSCs in Stromal Vascular Fraction (SVF), guaranteeing the differentiation ability of ATD-MSCs.

Update on cryopreservation of adipose tissue and adipose-derived stem cells

This article first discusses some fundamentals of cryobiology and challenges for cell and tissue cryopreservation. Then, the results of cryopreservation of adipose cells and tissues, including adipose-derived stem cells, in the last decade are reviewed. In addition, from the viewpoint of cryobiology, some desired future work in fat cryopreservation is proposed that would benefit the optimization, standardization, and better application of such techniques.

Microfat Grafting in Nasal Surgery

BACKGROUND

Injectable fillers are sometimes necessary to correct slight skin irregularities. However, there have been reports of necrosis after injection of alloplastic materials and heterogeneous transplants. On the other hand, the advantages of autogenous tissue grafts over those fillers are well established. Volumetric reshaping of the face with autologous tissue injection is a popular and reliable method with good long-term results. However, procedures performed on the fragile skin of the nose are prone to complications.

OBJECTIVES

The author conducted a study of injectable autologous microfat grafting to the nose in patients with secondary nasal deformities.

METHODS

During a 5-year period, 313 patients who had secondary nasal deformities with slight skin irregularities or severe nasal skin damage were treated with microfat grafting. At each patient's first injection session, excess harvested fat was cryopreserved for subsequent injection. To correct minor irregularities, 0.3 to 0.8 mL of microfat was injected during each session; for major irregularities or defects, 1 to 6 mL was required for each session.

RESULTS

One to 3 injections of microfat provided satisfactory results in all patients who had minor irregularities. For patients with multiple and severe irregularities, 3 to 6 injections were necessary and resulted in high patient satisfaction. In another group of patients, with severe traumatic skin damage, 6 to 16 injections were necessary for reconstruction. After repeated injections, each patient's skin damage was repaired.

CONCLUSIONS

Autologous microfat injection appears to be safe and effective for correcting slight irregularities of the nose.

LEVEL OF EVIDENCE

4.

The effect of lipoaspirates cryopreservation on adipose-derived stem cells

BACKGROUND

Autologous fat grafting has gained popularity, particularly with the discovery of adipose-derived stem cells (ADSC). The possibility of freezing lipoaspirates (LA) for later use has intriguing clinical potential. However, the effect of LA cryopreservation on ADSC is unclear.

OBJECTIVES

The authors explore the effect of LA cryopreservation on ADSC viability.

METHODS

Human LA (n = 8) were harvested using a standard technique. Lipoaspirate samples were either processed immediately as fresh LA (A) or stored at -20°C and then at -80°C for 30 days with (B) or without (C) freezing medium. Stromal vascular fraction (SVF) was separated from adipocytes and either cultured to obtain purified ADSC or processed for the isolation of 3 distinct ADSC subpopulations (CD90(+)/CD45(-), CD105(+)/CD45(-), and CD34(+)/CD31(-)). Apoptosis and necrosis were determined by an annexin V/propidium iodide assay and quantified by flow cytometry. The capability of ADSC for long-term proliferation and differentiation was also examined.

RESULTS

There were no significant differences in the apoptosis and necrosis of adipocytes, SVF, or ADSC between groups A and B. However, cell viability in SVF and ADSC was significantly compromised in group C as compared with group B (P < .01) due to higher ADSC apoptosis but not necrosis. The viable ADSC isolated from fresh or frozen LA were cultured for more than 20 passages and demonstrated similar patterns and speed of proliferation with strong capability to differentiate, evidenced by cell doubling time and positive staining with Oil Red O (Sigma-Aldrich, St Louis, Missouri) and alkaline phosphatase.

CONCLUSIONS

Lipoaspirates cryopreservation had a significant impact on ADSC apoptosis but not on ADSC necrosis, proliferation, or differentiations. Freezing medium provides significant protection against ADSC apoptosis.

Facial rejuvenation with staged injections of cryopreserved fat and tissue cocktail: clinical outcomes in the past 10 years

BACKGROUND

Facial rejuvenation by autologous fat transfer is common in aesthetic plastic surgery. The main drawback is progressive resorption, requiring repeated harvesting and microfat grafting.

OBJECTIVE

The authors present a method for cryopreservation of excess harvested fat and tissue to enable subsequent use of previously harvested excess material.

METHODS

Fat grafts were harvested using a 50-mL syringe and a 3- or 4-mm cannula. A tissue "cocktail" composed of dermis, fascia, and fat was prepared from excised scar tissue, tissue from abdominoplasty, or tissue from reduction mammaplasty. Cocktail specimens were placed in sterile tubes, immersed in a liquid nitrogen tank (-196°C), and stored at -80°C. At 3- to 6-month intervals, repeated cryopreserved fat graft injections were performed. Patients were evaluated by comparing preoperative and postoperative photographs.

RESULTS

Between 2000 and 2010, a total of 5199 cryopreserved fat or tissue injections were performed in 2439 consecutive patients (age range, 19-80 years). Nasolabial folds and lips were the most common injection sites. Clinical outcomes were satisfactory, and improved contour was achieved in most patients after repeated injections.

CONCLUSIONS

Cryopreservation of excess tissue for future injection is promising since repetitive injections are often required after resorption of microfat grafts. In our study, the survival of cryopreserved tissue cocktail or fat was comparable to that of fresh fat grafts and is therefore an effective adjuvant method for facial rejuvenation.

Cryopreservation of adipose tissue

The main obstacle to achieving favorable outcome of soft-tissue augmentation after autologous fat transplantation is unpredictable long-term results due to the high rate of absorption in the grafted site. At the present time, adipose aspirates can only be used for immediate autologous fat grafting during the same procedure in which liposuction is performed; therefore adipose aspirates obtained from the procedure are usually discarded. it has been a strong desire of both surgeons and patients to be able to preserve the adipose aspirates, if an optimal technique were available, for potential future applications. For the last several years, cryopreservation of adipose tissue has been studied extensively in the author's laboratory. Several findings from this exciting translational research will lead to develop a reliable method for long-term preservation of adipose tissue in the future. in addition, successful long-term preservation of adipose tissue may open a new era in adipose tissue related tissue regeneration.

Clinical grade adult stem cell banking

There has been a great deal of scientific interest recently generated by the potential therapeutic applications of adult stem cells in human care but there are several challenges regarding quality and safety in clinical applications and a number of these challenges relate to the processing and banking of these cells ex-vivo. As the number of clinical trials and the variety of adult cells used in regenerative therapy increases, safety remains a primary concern. This has inspired many nations to formulate guidelines and standards for the quality of stem cell collection, processing, testing, banking, packaging and distribution. Clinically applicable cryopreservation and banking of adult stem cells offers unique opportunities to advance the potential uses and widespread implementation of these cells in clinical applications. Most current cryopreservation protocols include animal serum proteins and potentially toxic cryoprotectant additives (CPAs) that prevent direct use of these cells in human therapeutic applications. Long term cryopreservation of adult stem cells under good manufacturing conditions using animal product free solutions is critical to the widespread clinical implementation of ex-vivo adult stem cell therapies. Furthermore, to avoid any potential cryoprotectant related complications, reduced CPA concentrations and efficient post-thaw washing to remove CPA are also desirable. The present review focuses on the current strategies and important aspects of adult stem cell banking for clinical applications. These include current good manufacturing practices (cGMPs), animal protein free freezing solutions, cryoprotectants, freezing & thawing protocols, viability assays, packaging and distribution. The importance and benefits of banking clinical grade adult stem cells are also discussed.

Cryopreservation of fat tissue and application in autologous fat graft: in vitro and in vivo study

BACKGROUND

Absorption of the autologous fat graft results in repeated harvesting procedures. The cost and complications increase with repeated procedures, but cryopreservation is one way to solve the problem. The aim of this study was to find an optimal temperature at which to store fat tissue with or without cryoprotective agents for long-term use.

METHODS

Fat tissues harvested by liposuction were stored in normal saline, frozen in the freezer following the preset program, and cryopreserved at -20, -80, and -196°C. The other group of fat tissues was stored in hydroxyethyl starch using the same frozen procedure. Two and 7 days after cryopreservation, viability tests were conducted. The fat tissues were injected into nude mice 2 and 4 weeks after cryopreservation. Three months later the fat grafts were harvested for histologic examination.

RESULTS

No significant differences in cell viability were found in either in vitro or in vivo experiments for the three preserving temperatures. The cryoprotective agent HES did not influence cell viability.

CONCLUSION

There were no differences in cell viability among the three temperatures and with the use of a cryoprotective agent. Cryopreservation for salvage management is a clinically practical method.

Adipose-derived stem cells for clinical applications: a review

The use of stem cells derived from adipose tissue as an autologous and self-replenishing source for a variety of differentiated cell phenotypes, provides a great deal of promise for reconstructive surgery. In this article, we review available literature encompassing methods of extraction of pluripotent adipose stem cells (ASCs) from lipoaspirate locations, their storage, options for culture, growth and differentiation, cryopreservation and its effect on stem cell survival and proliferation, and new technologies involving biomaterials and scaffolds. We will conclude by assessing potential avenues for developing this incredibly promising field.

Adipogenic differentiation of human adipose tissue-derived stem cells obtained from cryopreserved adipose aspirates

BACKGROUND

Although frozen adipose tissue is frequently used for soft tissue augmentation, the viability of frozen fat remains a controversy. The cryopreservation of adipose tissue is important for the future use of adipose-derived stem cells (ASCs) and adipocytes.

OBJECTIVE

To determine whether optimal cryopreservation techniques with regard to the addition of cryopreservative agents and preservation temperature is essential for the long-term storage of adipose tissue and whether ASCs from cryopreserved adipose aspirates are reliable for use in adipogenic differentiation.

MATERIALS AND METHODS

Adipose tissue was frozen directly or with cryoprotectant at -20 degrees C or -80 degrees C for 1 year. The viability of adipose aspirates and the differentiation of ASCs isolated from adipose tissue were evaluated.

RESULTS

The viability of adipose aspirates frozen with dimethyl sulfoxide at -80 degrees C was approximately 87% after 2 months of storage. Moreover, ASCs from adipose tissue stored with cryoprotectant survived successfully for 1 year and differentiated into adipocytes, although ASCs were not detected in the directly frozen adipose tissue.

CONCLUSION

Adipose tissue cryopreserved with cryoprotectant and stored at optimal temperature might prove to be a reliable source of human ASCs and adipocytes.

Current applications and safety of autologous fat grafts: a report of the ASPS fat graft task force

TASK FORCE STATEMENT: In 2007, the American Society of Plastic Surgeons formed a task force to conduct an assessment regarding the safety and efficacy of autologous fat grafting, specifically to the breast, and to make recommendations for future research. The task force formulated specific issues regarding fat grafting and then compiled them to focus on five broad-based questions: 1. What are the current and potential applications of fat grafting (specifically breast indications, and if data are available, other cosmetic and reconstructive applications)? 2. What risks and complications are associated with fat grafting? 3. How does technique affect outcomes, including safety and efficacy, of fat grafting? 4. What risk factors need to be considered for patient selection at this level of invasiveness? 5. What advancements in bench research/molecular biology potentially impact current or future methods of fat grafting? To answer these questions, the task force reviewed the scientific literature, critically appraised the information available, and developed evidence-based practice recommendations. Although the primary issue of interest was fat grafting to the breast, other aspects of fat grafting were evaluated.

Cryopreservation of autologous fat grafts harvested with the Coleman technique

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

The search for a useful method for the optimal cryopreservation of adipose aspirates: part II. In vivo study

PURPOSE

The previous in vitro study showed that trehalose, when used as a cryoprotective agent (CPA) in an optimal concentration, can provide adequate protection of adipose aspirates during cryopreservation.

OBJECTIVE

The authors evaluated the efficacy of trehalose in its optimal concentration for cryopreservation of human fat grafts in a well-established animal model.

METHODS

In this study (n = 20 in each group), adipose aspirates were harvested and processed from a female patient; the protocol for freezing and thawing of fat grafts was the same as the in vitro study. In the control group, 0.5 mL of fresh fat grafts was injected into the posterior scalp of a nude mouse. In the cryopreservation group 1, a combination of dimethyl sulfoxide (in 0.5M) and trehalose (in 0.2M) was injected as a CPA. In the cryopreservation group 2, only the optimal concentration of trehalose (in 0.35M) was administered as a CPA. In both cryopreservation groups, 0.5 mL of cryopreserved fat grafts was thawed and injected into the animal in the same manner as the control group. All animals in each group were observed for gross appearance of maintained fat grafts over their posterior scalps for up to eight weeks. The final volume and weight of maintained fat grafts and their histology were evaluated at the end of the study.

RESULTS

Group 2, compared with group 1, respectively, had equivalently maintained volume (38.2 +/- 10.1% versus 46.1 +/- 14.4%, ns) and weight (34.1 +/- 12.1% versus 38.9 +/- 14.7%, ns). However, the results from both cryopreservation groups were still inferior to those from the control group (both P < .05). Histologically, the basic structure of adipose tissue was maintained in all three groups.

CONCLUSION

Trehalose, serving as a CPA in its optimal concentration, appears to provide adequate protection of human fat grafts during cryopreservation in vivo. Such protection is similar to that provided by the combination of dimethyl sulfoxide and trehalose as a CPA. Because of its safety and effectiveness, trehalose can possibly be administered to patients for long-term preservation of their fat grafts.

Gluteal augmentation with cryopreserved fat

Gluteal augmentation with autologous fat is becoming a standard ancillary procedure for sculpting the buttock area. The high rate of resorption due to aggressive harvesting techniques or inadequate injection procedures often leads to repeated treatments. Currently, several techniques for storing fat by controlled freezing and thawing procedures can guarantee a high rate of cell viability, similar to that obtained with fresh tissue. This allows surgeons to compile fat tissue available for future repeat injections, decreasing additional costs and morbidity for patients. The authors describe a case of gluteal augmentation with cryopreserved fat in a 42-year-old man.

Culture effects of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on cryopreserved human adipose-derived stromal/stem cell proliferation and adipogenesis

Previous studies have demonstrated that EGF and bFGF maintain the stem cell properties of proliferating human adipose-derived stromal/stem cells (hASCs) in vitro. While the expansion and cryogenic preservation of isolated hASCs are routine, these manipulations can impact their proliferative and differentiation potential. This study examined cryogenically preserved hASCs (n = 4 donors), with respect to these functions, after culture with basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) at varying concentrations (0-10 ng/ml). Relative to the control, cells supplemented with EGF and bFGF significantly increased proliferation by up to three-fold over 7-8 days. Furthermore, cryopreserved hASCs expanded in the presence of EGF and bFGF displayed increased oil red O staining following adipogenic induction. This was accompanied by significantly increased levels of several adipogenesis-related mRNAs: aP2, C/EBPalpha, lipoprotein lipase (LPL), PPARgamma and PPARgamma co-activator-1 (PGC1). Adipocytes derived from EGF- and bFGF-cultured hASCs exhibited more robust functionality based on insulin-stimulated glucose uptake and atrial natriuretic peptide (ANP)-stimulated lipolysis. These findings indicate that bFGF and EGF can be used as culture supplements to optimize the proliferative capacity of cryopreserved human ASCs and their adipogenic differentiation potential.

Freezing adipose tissue grafts may damage their ability to integrate into the host

In this study, the effect of freezing on the morphology, viability, and VEGF synthesis of human adipose tissue grafts is examined. Currently, storage of adipose grafts involves freezing in simple saline solutions. However, the effect of freezing on the morphology and function of adipose tissue remains unclear. As a result, this study attempts to determine whether freezing adipose grafts should be considered prior to soft-tissue augmentation. In this study, the freezing of adipose grafts in saline for only 24 hr resulted in morphological changes in vivo and affected their ability to synthesize VEGF. The use of a simple cryopreservation medium containing sucrose appeared to maintain VEGF synthetic levels by the grafts and improved both their morphology and retention in vivo. However, the benefits of this cryopreservation medium were directly linked to storage time as long-term storage did not result in any noticeable benefit to graft retention. Finally, as an alternative to freezing, adipose grafts were combined with human adipose-derived stem cells (ASCs) to determine if their presence could enhance in vivo graft structure. The presence of ASCs did appear to improve graft structure in vivo over the short term and was also capable of improving tissue morphology when combined with grafts frozen in PBS. In conclusion, the successful use of adipose grafts may require a closer examination of the graft's storage conditions and time. Specifically, it now appears that the practice of freezing in saline may not be advisable if graft viability, activity, and structure are to be maintained in vivo.

Preserved proliferative capacity and multipotency of human adipose-derived stem cells after long-term cryopreservation

BACKGROUND

Human adipose-derived stem (stromal) cells are promising as a regenerative therapy tool for defective tissues of mesenchymal lineage, including fat, bone, and cartilage, and blood vessels. In potential future clinical applications, adipose-derived stem cell cryopreservation could be an indispensable fundamental technology, as has occurred in other fields involving cell-based therapies using hematopoietic stem cells and umbilical cord blood cells.

METHODS

The authors examined the proliferative capacity and multipotency of human adipose-derived stem cells isolated from lipoaspirates of 18 patients in total before and after a 6-month cryopreservation following their defined protocol. Proliferative capacity was quantified by measuring doubling time in cell culture, and multipotency was examined with differentiation assays for chondrogenic, osteogenic, and adipogenic lineages. In addition, expression profiles of cell surface markers were determined by flow cytometry and compared between fresh and cryopreserved adipose-derived stem cells.

RESULTS

Cryopreserved adipose-derived stem cells fully retained the potential for differentiation into adipocytes, osteoblasts, and chondrocytes and for proliferative capacity. Flow cytometric analyses revealed that surface marker expression profiles remained constant before and after storage.

CONCLUSIONS

Adipose-derived stem cells can be cryopreserved at least for up to 6 months under the present protocol without any loss of proliferative or differentiation potential. These results ensure the availability of autologous banked adipose-derived stem cells for clinical applications in the future.

Cryopreservation of human adipose tissues

Scientific studies on cryopreservation of adipose tissues have seldom been performed. The purpose of our present study is conducted both in vitro and in vivo to develop a novel cryopreservation method that can be used successfully for long-term preservation of human adipose tissues for possible future clinical application. In this study, samples of adipose aspirates were obtained from 36 adult white female patients after liposuction and collected from the middle layer after centrifugation. In the in vitro study, suitable cryoprotectant agents (CPAs) and their concentrations and possible combinations were selected from our preliminary experiment. A combination of dimethyl sulfoxide (Me(2)SO) and trehalose as CPA with the optimal concentration (0.5M Me(2)SO and 0.2M trehalose) was chosen and then used throughout the study. In addition, maximal recovery of adipose tissues was achieved after cryopreservation using slow cooling without seeding (1-2 degrees C/min to -30 degrees C, followed by plunging to -196 degrees C for storage) and fast warming (in 40 degrees C water bath, averaging 35 degrees C/min). Fresh adipose aspirates (Group 1), cryopreserved adipose aspirates without CPAs (Group 2), or cryopreserved adipose aspirates with CPAs (Group 3) were evaluated by integrated adipocyte counts and histology. In the in vivo study, fresh adipose aspirates (Group 1), cryopreserved adipose aspirates without CPAs (Group 2), or cryopreserved adipose aspirates with CPAs (Group 3) were injected into a nude mouse. The retained adipose aspirates (fat grafts) were harvested in each animal at 4 months and their weight, volume, and histology was assessed. In the in vitro study, significantly higher integrated viable adipocyte count (2.06+/-0.54 x 10(6)mL(-1) vs. 1.07+/-0.41 x 10(6)mL(-1), p<0.0011) of adipose aspirates was found in Group 3 compared with Group 2. Group 3 had only a marginally lower integrated viable adipocyte count compared with Group 1 (2.06+/-0.54 x 10(6)mL(-1) vs. 2.57+/-0.56 x 10(6)mL(-1), p=0.083). Histologically, more tissue shrinkage was evident in Group 2 compared with Group 3. In the in vivo study, various degrees of absorption of injected fat grafts were seen in all 3 groups. However, Group 3 had significantly more retained weight and volume of the injected fat grafts than Group 2 (both p<0.0001) but had significantly less retained weight and volume than Group 3 (weight, p=0.009178; volume, p=0.007836). Histologically, a large amount of tissue fibrosis was seen in Group 2, and reasonably well maintained fatty tissue with only a small amount of tissue fibrosis was seen in Group 3. The results from the present in vitro and in vivo studies, for the first time, demonstrate that our preferred cryopreservation method, the combination of 0.5M Me(2)SO and 0.2M trehalose as CPA in addition to the controlled slow cooling and fast rewarming protocol, appears to provide the maximum recovered results in cryopreservation of human adipose tissues and may become a real option after further refinements for cryopreservation of human adipose aspirates in a clinical setting.

Fat transplantation for treatment of the senescent face

For more than a century, clinicians have attempted to utilize fat for the treatment of tissue deficiencies and contour abnormalities. Autologous fat transplantation for soft tissue augmentation has become increasingly popular in recent years. This has occurred as a result of the present authors' comprehension that the aging face is not simply as a result of gravity-induced ptosis, but also as a result of volume loss secondary to the atrophy of tissues. 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 present authors describe their approach and technique of fat transplantation for the aging face.