Liver fibrosis represents the body’s response to chronic liver injury and appears to be similar mechanistically to the fibrogenic response in other organs. The result of hepatic fibrogenesis is cirrhosis, which results in many serious and life-threatening complications. The fibrogenic process is complicated, yet integrated and tightly regulated. The pathobiology of fibrogenesis includes elements of increased production of extracellular matrix proteins, tissue contraction, and ultimately, disruption of normal tissue structure architecture. It has been well established over the last 2 decades that a key cellular effector of this process in the liver is the hepatic stellate cell. Hepatic stellate cells exhibit a unique characteristic in that after injury in that they become activated and transform into myofibroblasts. This myofibroblastic transition is characterized not only by increased production of extracellular matrix (resulting in fibrosis), but also the programmed expression of multiple different smooth muscle specific proteins, such as the smooth muscle isoform of actin (smooth muscle actin - also Acta2), the smooth muscle isoform of heavy chain myosin, and others. Our hypothesis is that the myofibroblast (i.e., smooth muscle) transition, through the actin cytoskeleton, is critical in hepatic fibrogenesis; therefore, manipulation of this program in stellate cells and has the ability to inhibit extracellular matrix production and fibrosis both at the cellular level and in the liver during injury. This proposal seeks to break new ground toward a deeper understanding of the molecular basis for the myofibroblast transition during stellate cell activation after liver injury. We have found that the family of transcription factors, including myocardin and myocardin related transcription factor, are upregulated during the myofibroblast transition, and are critical regulators of the smooth muscle protein program typical of activated stellate cells (myofibroblasts). We present novel preliminary data revealing that the miR-143/145 complex, important in smooth muscle programming, is important in this process. Therefore, the goals of this proposal are (1) to study multiple aspects of miR-143/145 molecular regulation and the functional effects of miR-143/145 depletion in stellate cells and in whole liver after injury and (2) to investigate the biological effects of myocardin, a key transcriptional regulator of the smooth muscle program, in stellate cells, in vitro and in vivo. Because myofibroblasts are ubiquitous to many forms of parenchymal organ wound healing, the proposed studies have substantial implications for wound healing biology not only in the liver, but also in other organ systems. The proposed studies are highly innovative because we will elucidate basic mechanisms underlying the stellate cell to myofibroblast transformation and thus the fibrogenic cascade. As such, targeted approaches to interrupt this pathway will have a significant impa...