Particles of Different Sizes Affect the Retention Pattern of the Fat Grafts in a Mouse Model.

backgroundAutologous fat grafting is an effective form of soft tissue regeneration. However, the optimal fat particle size and graft retention pattern need more research.

methodsThe mouse inguinal fat pad was harvested and cut into fat particles of different diameters: ≥ 5 mm, 3-4 mm, 2-3 mm, 1-2 mm and 1 mm (micro-fat). A volume of 0.2 ml fat was transplanted into another mouse dorsum. Volume and retention rate were measured at 1, 4, 8 and 12 weeks. Histology analysis was performed. Immunofluorescence staining was used to evaluate M1 and M2 macrophage infiltration and graft angiogenesis.

resultsFat retention was highest in the "> 5 mm" group and lowest in the "micro-fat" group. Large vacuoles were more common in larger-diametered fat particles. There was less collagen accumulation in the well-vascularized connective tissue in the "1-2 mm" group. The infiltrated nucleated cells peak at week 4 in groups of fat particles under 3 mm and at week 8 in in groups with fat particles above 3 mm. The number of M1 macrophages peaked at week 1 and then declined in all groups except for the "5 mm" group. The number of M2 macrophages peaked at week 4 and gradually decreased through 12 weeks in the groups below 3 mm, but increased through 12 weeks in the groups above 3 mm. Vascular intensity was similar to M2 macrophage prevalence.

conclusionsFat particles of different sizes may posses different retention patterns. Larger grafts have higher retention rate but worse quality. Meanwhile, smaller grafts have better quality with lower retention rate. 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 .