Oil Droplet in Apoptotic Uniocular Adipocyte: A Double-Edged Sword in Determining Macrophage Phenotype and its Implications on Fat Grafting.

backgroundFat grafting procedure is increasingly popular. However, unstable retention rate hindered its further application. Research primarily focuses on the revascularization of grafted fat.

methodsThe membrane mature adipocyte aggregate cultures method was used to culture uniocular adipocytes in vitro. Staurosporine was used to induce apoptosis in uniocular adipocytes, multi-ocular adipocytes, and adipose-derived stem cells (ASCs). The apoptotic uniocular adipocytes were examined by scanning electron microscopy, and methanol was used to stimulate fusion of apoptotic adipocytes. Immunofluorescence staining and Western blotting were used to identify macrophage phenotypes after co-culture with apoptotic uniocular adipocytes and fused oil droplets.

resultsUniocular adipocytes maintained their morphology even after apoptosis induction, while multi-ocular adipocytes and ASCs cracked and released cellular components. Methanol induced fusion of apoptotic uniocular adipocytes, and the fused large oil droplets attracted multiple cell debris, as indicated by DAPI/PI staining. Co-culture with apoptotic uniocular adipocytes induced the M2 polarization, whereas co-culture with fused oil droplets induced M1 polarization.

conclusionsThis study demonstrated that the surface tension of uniocular adipocytes preserves basic cellular morphology and promotes M2 polarization. In contrast, in unstable culture environment (e.g., methanol exposure), surface tension causes fusion of apoptotic adipocytes, leading to M1 polarization. These findings provide new insights into the morphological changes of apoptotic adipocytes during fat grafting, which could potentially influence the outcome of fat grafting. 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 https://link.springer.com/journal/00266 .