Size Matters: The Impact of Lipoaspirate Processing Technique on Adipocyte Cell Size in Autologous Fat Grafting

PURPOSE: Autologous fat grafting (AFG) is a minimally invasive procedure in which a patient's own adipose tissue is transferred to a targeted area for volume retention. While commonly used in breast reconstruction, there is significant variation in fat graft volume retention. Our previous study demonstrated differences in volume retention based on lipoaspirate processing techniques, with standard decantation resulting in worse volume retention compared to active wash and filtration (AWF) or low-pressure (LP) decantation. However, specific factors affecting volume retention remain unclear, with adipocyte cell diameter being a potential influence, as smaller cells may be less prone to shearing. This study aims to evaluate adipocyte cell size in AFG using these three techniques. METHODS: A prospective, blinded, randomized clinical trial was conducted at our institution from March 2021 to July 2023 (ClinicalTrials.gov identifier: NCT04891510). Patients were randomized to receive either standard decantation, AWF, or LP decantation. Approximately 10 cc of lipoaspirate was collected, fixed overnight in 10% formalin, dehydrated with 70% ethanol, and embedded in paraffin. Hematoxylin and eosin (H&E) slides were sectioned for microscopy, and cell diameter was measured using Zeiss software by two independent investigators. ANOVA was used to compare adipocyte diameter between groups, and linear regression assessed the correlation between adipocyte size and volume retention. RESULTS: Forty-four patients were enrolled in the trial: 17 (38.6%) patients received standard decantation, 16 (36.4%) received AWF, and 11 (25.0%) received LP decantation. Groups did not differ significantly in age or body mass index (p > 0.05). There was no significant difference in average cell size across standard decantation, AWF, and LP decantation (88.1 microns vs. 90.1 microns vs. 90.1 microns; p > 0.05). However, the distribution of cell sizes varied by technique. The AWF method resulted in a skew toward smaller cell sizes, while both standard and LP decantation techniques exhibited a normal distribution around the mean. Simple linear regression analysis revealed no significant correlation between adipocyte size and volume retention. CONCLUSIONS: Our findings suggest that larger adipocyte cells may be filtered out with the AWF technique, indicating that lipoaspirate processing techniques may be used to select for different adipocyte cell sizes. Although our data did not show a correlation between adipocyte size and volume retention, further research is needed to explore the relationship between the adipocyte microenvironment and fat graft retention.