Comparison of the viability of cryopreserved fat tissue in accordance with the thawing temperature

Exosomes Derived from Human Adipose-Derived Stem Cells Cannot Distinctively Promote Graft Survival in Cryopreservation Fat Grafting

BACKGROUND

Cryopreserved fat has limited clinical applications due to its rapid absorption, high degree of fibrosis, and risk of complications after grafting. Many studies have verified that Adipose-derived mesenchymal stem cell-derived exosomes (ADSC-Exos) can improve fresh fat graft survival. This study assessed whether ADSC-Exos could improve the survival of cryopreserved fat grafts.

METHODS

Exosomes were isolated from human ADSCs were subcutaneously engrafted with adipose tissues stored under different conditions (fresh; cryopreserved for 1 month) into the backs of BALB/c nude mice (n = 24), and exosomes or PBS were administered weekly. Grafts were harvested at 1, 2, 4, and 8 weeks, and fat retention rate, histologic, and immunohistochemical analyses were conducted.

RESULTS

At 1, 2, and 4 weeks after the transfer, cryopreserved fat grafts in groups of exosome-treated showed better fat integrity, fewer oil cysts, and reduced fibrosis. Further investigations of macrophage infiltration and neovascularization revealed that those exosomes increased the number of M2 macrophages at 2 and 4 weeks (p<0.05), but had limited impact on vascularization (p>0.05). It's important to note that no significant differences (p>0.05) were observed between the two groups in both histological and immunohistochemical evaluations at 8 weeks post-transplantation.

CONCLUSIONS

This study suggests that ADSC-Exos could improve the survival of cryopreserved fat grafts in the short term (within 4 weeks), but the overall improvement was poor (after 8 weeks). This suggests that the utility of using ADSC-Exos to treat cryopreserved adipose tissue grafts is limited.

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 .

Viability of Fat Cells in Frozen Fat Tissue in Relation to Thawing Technique

Damage of frozen fat, which will be used for retransplantation, is inevitable. Reuse of frozen fat requires a thawing process. No standardized method has yet been established for thawing frozen fat.

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 .

Effect of Diameter and Fenestration Area of the Liposuction Cannula on the Viability of the Adipocytes

BACKGROUND

Loss of volume is perhaps the most frustrating problem of fat grafting. The process of fat grafting depends on different variables such as harvesting, processing, and injection techniques. Results between studies that evaluate the effect of the cannula size on fat graft survival have been controversial. However, the role of the fenestration area of the cannula has not been described.

METHODS

Four custom-made cannulas with a single fenestration were used for this study. Cannulas vary in diameter and area of the fenestration. Healthy patients seeking primary liposuction of the abdomen for aesthetic reasons were included. Lipoaspiration was performed in a clockwise pattern, and the order of the cannulas was rotated. Negative pressure was maintained at 0.8 atm at all times. Ten ml of fat, obtained from the suction tube, was poured into 20-ml conical centrifugal tubes for further processing. One gram of lipoaspirate was extracted from each sample, and acridine orange stain was added. Adipocytes were extracted, extended in a frotis, and observed by a histologist (masked fashion) under fluorescence microscopy. Viability was reported in percentages per sample.

RESULTS

The overall viability was 64.75% ± 18.58. The viability of the obtained samples ranged from 66.51± 20.66 % to 62.83 ± 18.1. In further analysis, comparing the viability according to the shaft diameter and fenestration area, there was no significant difference among groups.

CONCLUSIONS

Neither the diameter of the cannula nor the size of the fenestrations are determining factors to affect the viability of the adipocytes.

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 .

Frozen Fat Grafts Maintain Vascular Endothelial Growth Factor Expression and Mediate Angiogenesis During Adipose-Derived Stem Cell Enrichment for Soft Tissue Augmentation

BACKGROUND

Fresh fat grafts are commonly used in both esthetic and reconstructive surgeries, but the graft resorption rate varies. Cryopreservation of unused fat for later touch-up is one option to resolve this variation. In our previous studies, we found that fat cryopreservation may be a practical strategy for storing fat tissue. To explore the cryopreservation method, we evaluated the role of vascular endothelial growth factor (VEGF) in human frozen fat grafts.

METHODS

The concentration of VEGF in human frozen fat grafts subjected to different preservation times was determined using Western blotting and enzyme-linked immunosorbent assay. The angiogenic effect of frozen fat grafts was evaluated using a chorioallantoic membrane assay. Furthermore, the impact of adding human adipose-derived stem cells (hADSCs) or different concentrations of avastin (bevacizumab) to frozen fat grafts on angiogenesis was assessed. The viability of frozen fat grafts with or without hADSCs was evaluated using a nude mouse implantation study. Explanted fat tissues were examined on days 1, 4, 7, 14, 28, and 90, and morphological and histological analyses, immunohistochemistry, and enzyme-linked immunosorbent assay (VEGF concentration) were carried out.

RESULTS

No significant difference in VEGF concentration between fresh and frozen fat was observed with respect to preservation duration. In the chorioallantoic membrane assay, frozen fat grafts with hADSCs displayed significantly enhanced angiogenesis. Avastin was found to decrease angiogenesis in frozen fat grafts. However, in the nude mouse implantation study, frozen fat grafts displayed VEGF maintenance, with the highest concentration observed on day 7. Adding hADSCs to the graft further increased the VEGF concentration and CD31 expression. Fat graft viability was found to be higher in the frozen fat grafts containing hADSCs than in grafts without hADSCs.

CONCLUSIONS

Human fat grafts can maintain VEGF expression under frozen conditions for at least 12 months. The addition of hADSCs to the frozen fat graft could further enhance angiogenesis, VEGF expression, and fat cell viability.

Cryopreservation of Human Adipose Tissues and Adipose-Derived Stem Cells with DMSO and/or Trehalose: A Systematic Review

Adipose tissue senescence is implicated as a major player in obesity- and ageing-related disorders. There is a growing body of research studying relevant mechanisms in age-related diseases, as well as the use of adipose-derived stem cells in regenerative medicine. The cell banking of tissue by utilising cryopreservation would allow for much greater flexibility of use. Dimethyl sulfoxide (DMSO) is the most commonly used cryopreservative agent but is toxic to cells. Trehalose is a sugar synthesised by lower organisms to withstand extreme cold and drought that has been trialled as a cryopreservative agent. To examine the efficacy of trehalose in the cryopreservation of human adipose tissue, we conducted a systematic review of studies that used trehalose for the cryopreservation of human adipose tissues and adipose-derived stem cells. Thirteen articles, including fourteen studies, were included in the final review. All seven studies that examined DMSO and trehalose showed that they could be combined effectively to cryopreserve adipocytes. Although studies that compared nonpermeable trehalose with DMSO found trehalose to be inferior, studies that devised methods to deliver nonpermeable trehalose into the cell found it comparable to DMSO. Trehalose is only comparable to DMSO when methods are devised to introduce it into the cell. There is some evidence to support using trehalose instead of using no cryopreservative agent.

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.

Comparisons between fresh and cryopreserved fat injections in facial lipofilling

Background

Autologous fat is considered an ideal filler material, and the use of cryopreserved fat grafts is promising in terms of flexibility and efficiency. Therefore, cryopreserved fat grafts have become more common in recent years; however, their complications require further consideration.

Methods

We evaluated 53 patients who underwent facial lipofilling at our institution to confirm the clinical usefulness and safety of cryopreserved fat. Fresh fat injections with or without cryopreserved fat were administered. At one or more sites, 22 patients had a single fresh fat injection, four patients had two or more fresh fat injections, 16 patients had one fresh fat injection followed by one cryopreserved fat injection, six patients had one fresh fat injection followed by two cryopreserved fat injections, and five patients had two fresh fat injections and one or more cryopreserved fat injections.

Results

In total, 281 sets of injection procedures were performed at various sites, of which 170 involved one fresh fat injection, 89 involved one fresh fat injection and one cryopreserved fat injection, and 11 involved one fresh fat injection and two cryopreserved fat injections. One patient experienced self-resolving inflammation as a complication after the second injection in the right cheek. No statistically significant differences were found between the fresh and cryopreserved fat injections.

Conclusion

We suggest that cryopreserved fat is a useful and safe resource for multiple fat injections, with advantages including aseptic fat handling and the delicacy of the technique.

Serial Injections of Cryopreserved Fat at -196°C for Tissue Rejuvenation, Scar Treatment, and Volume Augmentation

Background:

Fat grafting has become popular since the first report of structural fat grafting in 2001. Fat grafting is effective not only for volume augmentation but also for tissue revitalization. However, fat harvesting is necessary before fat grafting can be performed. Therefore, the performance of serial fat injections is very challenging when treating such patients.

Methods:

From August 2015 to March 2017, we investigated 219 patients who underwent fat grafting using the fat that had already been cryopreserved at −196°C.

Results:

Follow-up ranged from 3 months to 2 years. No complications occurred, and all outcomes were satisfactory. Three representative cases were also reviewed.

Conclusions:

The cryopreserved fat at −196°C could be served as a useful method for serial fat grafting for clinical use; however, further research involving longer follow-up and pathological findings are needed.

The Relationship of a Combination of Human Adipose Tissue-Derived Stem Cells and Frozen Fat with the Survival Rate of Transplanted Fat

Background

The survival rate of grafted fat is difficult to predict, and repeated procedures are frequently required. In this study, the effects of the freezing period of harvested adipose tissue and the addition of human adipose tissue-derived stem cells (ASCs) on the process of fat absorption were studied.

Methods

Adipose tissue was obtained from patients who underwent a lipoaspirated fat graft. The fat tissue was cryopreserved at -20℃ in a domestic refrigerator. A total of 40 nude mice were used. The mice in the experimental group received three different subcutaneous injections in the back: an injection of fresh fat and ASCs, an injection of fat that had been frozen for one month and ASCs, and an injection of fat that had been frozen for two months and ASCs. The control mice received fat grafts without ASCs. The mice were sacrificed at four or eight weeks after the procedure, and the grafted fat tissues were harvested. The extracted fat was evaluated using photographic analysis, volume measurements, and histological examination.

Results

In the control group, the fat resorption rates four weeks after transplantation in the grafts of fresh fat, fat that had been frozen for one month, and fat that had been frozen for two months were 21.14%, 22.46%, and 42.56%, respectively. In the experimental group, the corresponding resorption rates were 6.68%, 13.0%, and 33.9%, respectively.

Conclusions

ASCs can increase the fat graft survival rate. The use of ASCs in fat grafting can reduce the need for repeated fat grafts and provide good long term results.