Figure 4

Influence of cytokines on pericyte expression of β1 integrins. (A) Pericytes were cultured on collagen I in the presence of different cytokines as described in Methods. After 2 days of culture, pericyte expression of the α1, α2, α5, α6, and β1 integrin subunits was analyzed by flow cytometry, and the expression level is shown as the percentage change relative to control conditions (no cytokine). All points represent the mean ± SEM of four experiments. Note that tumor necrosis factor (TNF)-α promoted a switch in integrins, downregulating α1 while strongly upregulating α2 integrin, and this effect was exactly the opposite to that seen when pericytes differentiated (DMEM + FBS; DF condition). In addition, several factors, including transforming growth factor (TGF)-β1 and TNF-α increased α5 integrin expression (** P<0.01). (B) Histogram flow-cytometry plots illustrating the contrasting influence of TNF-α and DF on pericyte expression levels of α1 and α2 integrin subunits. Note that TNF-α increased the α2:α1 ratio, whereas DF had the opposite effect.