P2X7 regulates collagen expression in HSIFs. Primary human small intestine fibroblasts (HSIFs) were treated with TGF-β1 5 ng/mL during 24 h and transiently transfected with a specific siRNA against P2X7 receptor. (A) Graph shows mRNA expression of P2X7 receptor in HSIFs treated with TGF-β1 and with the P2X7 receptor expression transiently silenced (n = 5). (B) Graphs show the expression of COL1A1, COL3, COL4, COL5A1, COL5A2, COL6A3, α-SMA, VIMENTIN, and TGF-β in HISFs treated with TGF-β1 and transfected with a specific siRNA against P2X7 receptor (n = 5). (C) Graph shows protein levels of P2X7 receptor in HSIFs treated with TGF-β1 and with the P2X7 receptor expression transiently silenced (n = 5). The data are expressed as fold induction in percentage. (D) Representative pictures after immunofluorescence staining of COL1A1 in HSIFs treated with TGF-β1 and with the P2X7 receptor expression transiently silenced. The length of the white scale bar represents 50 µm. In all cases, bars in graphs represent mean ± SEM. * p < 0.05, ** p < 0.01, and *** p < 0.001 vs. siCtrl HSIFs; # p < 0.05 and ## p < 0.01 vs. TGF-β1-treated HISFs.