Improving Fat Graft Retention with Micro/Nanobubbles in Vivo

Abstract

PURPOSE: Fat grafting is one of the most popular procedures in plastic and reconstructive surgery.1 However, retention rates of transplanted fat remain variable, often rendering unpredictable outcomes in the long term. Inadequate tissue oxygenation during the transplant process is thought to play a major role in this variability.2 To that end, we sought to examine the implementation of oxygenated micro/nanobubbles (MNBs) during transplantation of lipoaspirate as a means of maintaining adequate tissue oxygenation and improving graft survival. MNBs are small gas bubbles (<100 µm) that are stable for hours and can be saturated with high amounts of oxygen.3 Furthermore, their negative charge and irregular surface characteristics make them an ideal agent for separation and decontamination of charged particulate matter.4 We hypothesize that MNBs will enhance lipoaspirate survival and establish themselves as an important adjunctive step to be incorporated into current fat grafting techniques. METHODS: Twelve 6-week-old Fox Chase SCID beige mice were used as hosts for transplanted human lipoaspirate. Lipoaspirate samples harvested from healthy human donors were washed with either an oxygenated MNB or saline solution prior to injection into the dorsum of the mice. To assess graft viability, explants were harvested at 4-, 8-, and 12-week intervals. Following harvest, grafts were weighed, and volumes were obtained using gas pycnometry. Immunohistochemistry was completed utilizing antibodies directed toward CD31, Perilipin, and CA-9 as surrogates for angiogenesis, adipogenesis, and hypoxia, respectively. Quantitative analysis of IHC images was performed via ImageJ. RESULTS: The grafts that were washed in the MNB solution were significantly greater by mass as early as 4 weeks (P < 0.01). Likewise, an analysis of variance (ANOVA) showed that MNB-washed explants had greater volumes across all time points (P < 0.05). While CD31 staining showed that vessel density was equivocal at each interval between experimental and control groups, perilipin staining showed significantly greater intensity in the MNB group at both 4 and 8 weeks. Moreover, CA-9 staining intensity in the MNB group was notably lower by 12 weeks compared with that in the control group. CONCLUSIONS: The utilization of MNBs, as a source of oxygen, in the wash step prior to transplant may be beneficial for improving graft survival. MNB-washed grafts displayed greater volumes and masses over 12 weeks compared with their control-group saline-washed counterpart. Furthermore, as evidenced by the surrogate markers in the IHC analysis, lipoaspirate samples subjected to the MNB-wash demonstrated improved de novo adipogenesis and less hypoxia. Taken together, these preliminary data reveal promising translatable implications for oxygenated MNBs in the future of fat grafting paradigms. REFERENCES: 1. Simonacci F, Bertozzi N, et al. Procedure, applications, and outcomes of autologous fat grafting. Ann Med Surg (Lond). 2017;20:49–60. 2. Khouri RK, Jr., Khouri RE, et al. Diffusion and perfusion: the keys to fat grafting. Plast Reconstr Surg Glob Open. 2014;2(9):e220. 3. Matsuki N, Ichiba S, et al. Blood oxygenation using microbubble suspensions. Eur Biophys J. 2012;41(6):571–578. 4. Sayadi LR, Ziegler ME, et al. Topical oxygen therapy & micro/nanobubbles: a new modality for tissue oxygen delivery. Int Wound J. 2018;15(3):363–374.