title: Comparative analysis of processing methods in fat grafting.
abstract: BACKGROUND
  Centrifugation is a popular processing method, with an unclear mechanism of action. Hypotheses include fat concentration, reduced inflammatory response by removal of blood, and concentration of adipose-derived stem cells. The authors performed multiple experiments to determine the role of centrifugation and compared it with a different processing method (mesh/gauze technique).
  
  
  METHODS
  Lipoaspirate components were quantified after centrifugation at increasing speed to determine concentration efficacy. For comparison, the authors quantified the concentration efficacy of mesh/gauze. They also compared the number of adipose-derived stem cells isolated by either method. To determine the effects of each component, they compared fat alone to fat mixed with various spinoff components in a mouse model. They also compared centrifugation to mesh/gauze.
  
  
  RESULTS
  The adipocyte fraction remains constant above 5000 g, whereas 1200 g results in 91 percent concentrated fat. Mesh/gauze also results in 90 percent concentrated fat. The number of adipose-derived stem cells in 1 g of fat was 1603 ± 2020 and 1857 ± 1832 in the centrifuge and mesh/gauze groups, respectively (p = 0.86). Five "add-back" groups were created: fat plus oil, fat plus surgical tumescence, fat plus fresh tumescence, fat plus cell pellets and fresh tumescence, and fat plus cell pellets. The fat-only group had better retention than the groups mixed with tumescence, regardless of whether it was surgical, fresh, or had cell pellets. Oil did not affect grafts. Centrifugation at 1200 g was equivalent to mesh/gauze (0.73 ± 0.12 g and 0.72 ± 0.13 g, respectively).
  
  
  CONCLUSIONS
  Centrifugation improves graft retention by concentration of the adipocyte fraction. The concentration efficacy of mesh/gauze is equivalent to centrifugation at 1200 g, with equivalent in vivo outcomes.
authors.affiliation: Boston, Mass. From the Division of Plastic and Reconstructive Surgery, Massachusetts General Hospital.
authors.forename: Harry M
authors.initials: HM
authors.lastname: Salinas
authors.forename: G Felix
authors.initials: GF
authors.lastname: Broelsch
authors.forename: Justin R
authors.initials: JR
authors.lastname: Fernandes
authors.forename: Michael C
authors.initials: MC
authors.lastname: McCormack
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Meppelink
authors.forename: Mark A
authors.initials: MA
authors.lastname: Randolph
authors.forename: Amy S
authors.initials: AS
authors.lastname: Colwell
authors.forename: William G
authors.initials: WG
authors.lastname: Austen
mesh_terms: D017667:Adipocytes / Q000637:transplantation*; D000328:Adult; D000818:Animals; D002469:Cell Separation / Q000379:methods; D002498:Centrifugation / Q000379:methods*; D005260:Female; D006801:Humans; D051379:Mice; D008875:Middle Aged; D033581:Stem Cell Transplantation