COL3A1 and stroke disorder: Along this line of evidence, IL-18 after stroke is produced by microglia and contributes to fibrosis in the aged rat brain via STAT3 activation, leading to a large accumulation (237-fold over controls) of collagen III (Col3a1) transcripts that are normally expressed in adventitial fibroblasts (Matsui et al., 2013) (Table 2).