Todorčević et al. BMC Genomics 2010, 11:39 http://www.biomedcentral.com/1471-2164/11/39 Page 7 of 17 Figure 6 Immune genes analyzed with real-time qPCR. In this and other panels data are shown as -ΔΔCt ± SE (n = 5). Significant difference from day 1 (t-test, p < 0.05) is indicated with *. TNFa - tumour necrosis factor alpha, TNF decoy - tumour necrosis factor decoy receptor, FLAP - 5-lipoxygenase-activating protein, JAK1 - janus kinase 1, PD-L1 - programmed cell death ligand 1, IL-13 a2 - interleukin 13, LECT2 - leukocyte cell- derived chemotaxin a2, C5 - complement component 5. stages of the culture. Decrease in gene expression of markers of osteo/chondrogenic, myogenic, immune and vasculature cell lineages (Fig. 5) and increase in adipo- genic markers indicate that the preadipocyte precursors, probably due to their active proliferation, become the preponderant cell type at confluence. Recent studies in mammals showed that tissue-resi- dent MSCs originate from the smooth-muscle-like peri- cytes [39,40], which are laid over junctions of endothelial cells in blood vessel walls [41]. Once liber- ated from the endothelial cell, pericyte is activated and can be considered a stem cell [42]. Characterisics of the WAT population of stem cells and early events in the determination phase are much less studied than the terminal differentiation phase of adipogenesis. The breakthrough in the understanding of elusive origins of the adipogenic MSCs was made only recently in a study of Tang et al. [9], which demonstrated that pericytes surrounding blood vessel walls in WAT are precursor cells of preadipocytes. Gradual attenuation of the vascu- lature specific genes glomulin and LIVE1 and increase of the pericytic marker TAGLN at days 7 and 9 support perivascular origin of salmon preadipocytes as well. Early PPARg expression could represent an additional