COL1A1 and Hepatic fibrosis: However, another report showed that activation of VDR did not improve the manifestation of preexisting pathology despite inhibiting the development of hepatic fibrosis by inhibiting collagen type I alpha 1 chain (COL1A1), tissue inhibitor of metalloproteinase (TIMP1) and α-SMA (Abramovitch et al., 2014).