Culture of porcine stromal-vascular cells in serum-free medium: Differential action of various hormonal agents on adipose conversion

We developed a strictly controlled serum-free culture system and tested the effects of adipogenic and antiadipogenic agents on the proliferation and(o r) adipose conversion of porcine stromal-vascular cells. To avoid any inter ference with serum components, stromal-vascular cells were isolated, plated , and grown in absence of serum. In these culture conditions, a very limite d growth phase and the absence of cell confluence were observed. However, w hen compared with continuous culture in serum-containing medium, the serum- free conditions were significantly more adipogenic as assessed by increased lipid content and increased enzymatic activities for lipoprotein lipase, g lycerol 3-phosphate dehydrogenase, and malic enzyme. In serum-free medium, physiological concentrations of insulin or IGF-I were sufficient to signifi cantly increase the percentage of lipid-containing cells, whereas triiodoth yronine (T-3) and GH had no effect. Insulin, IGF-I, and, more moderately, T -3 also accelerated the lipid filling in the lipid-containing cells. In the presence of insulin, stimulation by T-3 or hydrocortisone alone had no eff ect on glycerol 3-phosphate dehydrogenase activity, whereas their concomita nt addition significantly increased it. Chronic exposure to tumor necrosis factor-alpha dose-dependently stimulated cell proliferation but clearly inh ibited differentiation. Epidermal growth factor, another known antiadipogen ic agent, also significantly increased the proliferation of stromal-vascula r cells, but, surprisingly, this was not correlated with inhibition of adip ocyte differentiation. Indeed, epidermal growth factor treatment did not de crease lipid filling and significantly improved lipoprotein lipase and mali c enzyme activities. Taken together, the results obtained in these strictly controlled serum-free culture conditions point out functions for insulin, IGF-I, hydrocortisone, and T-3 during early and(or) later steps of porcine adipose conversion. In addition, this study reports a positive activity of epidermal growth factor on porcine adipocyte differentiation that is in cle ar contrast with previous works performed with rodent cells.