ACTA1 and colitis: Our comparison of the cellular sites of procollagen α1(I)-GFP expression and α-SMA or vimentin immunoreactive cells indicates that in response to DSS or TNBS colitis, vimentin positive cells are by far the most abundant cell types exhibiting activation of procollagen α1(I)-GFP in mucosa, submucosa, serosa and, muscularis layers.