An Analysis of Adipocyte Differentiation in Vitro that Evaluates a Potency of Marbling Formation

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The accumulation of intramuscular fat in bovine has been an important factor in determining meat quality as a marbling. The elucidation of cells from bovine intramuscular adipose tissue developing mature adipocytes is a more fundamental problem to precisely understand the mechanisms of marbling formation. The research presented here was designed to establish the culture system of lipogenesis by adipocyte precursor cells isolated from bovine skeletal muscle, and to study the influence of growth factors on the adipose differentiation and determine whether the intramuscular fat quantity and distribution are estimated by the differentiation of adipocytes in cultures.The results presented in this study are as follows :(1) The culture system for adipocyte differentiation from adipocyte precursor cells derived from bovine intramuscular adipose tissue was established when the precursor cells were transferred in a mixture of MEX/Ham's 12 medium (1 : 1 by vol.) containing 100nM or 1uM dexamethas … More one, 170nM insulin, 10ug/ml transferrin and 1nM triiodothyronine after they became the confluent cultures in DMEX medium supplemented with 10% fetal bovine serum and 1.5% swine fetal extract.(2) Differentiation and maturation of intramuscular adipocytes were caused by the addition of both dexamethasone and insulin but not each of them.(3) Dexamethasone was indispensable to develop preadipocytes and induce mature adipocytes. Especially, the factor was more effective on the growth of adipoblasts and the differentiation of preadipocytes at a concentration of 100nM-1muM.On the other hand, insulin was more effective on the maturation of adipocytes from preadipocytes.(4) Developing ability into adipocytes from intramuscular adipocyte precursor cells in vitro was paralleled with the quantity and extension of marbling in bovine skeletal muscles.(5) The differentiation and maturation of adipocytes was recognized even in cultures of adipocyte precursor cells derived from longissimus muscle of 14 months old of Japanese Black steers.(6) The immunocytochemical characterization of intramuscular adipocytes developing in cultures corresponded with that of intramuscular adipose tissue in which the cells were positively reacted with anti-LPL antibody, anti-vimentin antibody and Factor VIII antibody. Less