Pathways of liver fibrosis are controlled by connective tissue growth factor (CCN2). In this study, CCN2 was identified as a target of miR-199a-5p, which was principally expressed in quiescent mouse hepatic stellate cells (HSCs) and directly suppressed production of CCN2. Up-regulated CCN2 expression in fibrotic mouse livers or in activated primary mouse HSCs was associated with miR-199a-5p down-regulation. MiR-199a-5p in quiescent mouse HSCs inhibited the activity of a wild-type CCN2 3′ untranslated region (3′-UTR) but not of a mutant CCN2 3′-UTR lacking the miR-199a-5p-binding site. In activated mouse HSCs, CCN2, α-smooth muscle actin, and collagen 1(α1) were suppressed by a miR-199a-5p mimic, whereas in quiescent mouse HSCs, the inhibited CCN2 3′-UTR activity was blocked by a miR-199a-5p antagomir. CCN2 3′-UTR activity in human HSCs was reduced by a miR-199a-5p mimic. MiR-199a-5p was present at higher levels in exosomes from quiescent versus activated HSCs. MiR-199a-5p–containing exosomes were shuttled from quiescent mouse HSCs to activated mouse HSCs in which CCN2 3′-UTR activity was then suppressed. Exosomes from quiescent HSCs caused miR-199a-5p–dependent inhibition of CCN2, α-smooth muscle actin, or collagen 1(α1) in activated HSCs in vitro and bound to activated HSCs in vivo. Thus, CCN2 suppression by miR-199a-5p accounts, in part, for low-level fibrogenic gene expression in quiescent HSCs and causes dampened gene expression in activated HSCs after horizontal transfer of miR-199a-5p in exosomes from quiescent HSCs.
Chen, L., Chen, R., Velazquez, V. M., & Brigstock, D. R. (2016). Fibrogenic Signaling Is Suppressed in Hepatic Stellate Cells through Targeting of Connective Tissue Growth Factor (CCN2) by Cellular or Exosomal MicroRNA-199a-5p. American Journal of Pathology, 186(11), 2921–2933. https://doi.org/10.1016/j.ajpath.2016.07.011