Description: ABSTRACT Fibrosis and cancer represent two major complications of chronic liver disease. MicroRNAs have been implicated in the development of fibrosis and cancer, thus constituting potential therapeutic targets. Here, we investigated the role of miR-21, a microRNA that has been implicated in the development of fibrosis in multiple organs and also been suggested to act as “oncomir”. Accordingly, miR-21 was the microRNA that showed the strongest upregulation in activated hepatic stellate cells (HSC) in multiple models of fibrogenesis, with an 8- to 24-fold induction compared to quiescent HSC. However, miR-21 antisense inhibition did not suppress the activation of murine or human HSC in culture or in liver slices. Moreover, antisense inhibition or genetic deletion of miR-21 in two independently generated knockout mice did not alter HSC activation or liver fibrosis in models of toxic and biliary liver injury. Despite a strong upregulation of miR-21 in injury-associated hepatocellular carcinoma and in cholangiocarcinoma, miR-21 deletion or antisense inhibition did not reduce the development of liver tumors. As inhibition of the most upregulated microRNA did not affect HSC activation, liver fibrosis and fibrosis-associated liver cancer, we additionally tested the role of microRNAs in HSC by HSC-specific Dicer deletion. Although Dicer deletion decreased microRNA expression in HSC and altered the expression of select genes, it only exerted negligible effects on HSC activation and liver fibrosis. In conclusion, genetic and pharmacologic manipulation of miR-21 does not inhibit the development of liver fibrosis and liver cancer. Moreover, suppression of microRNA synthesis does not significantly affect HSC phenotype and activation. This article is protected by copyright. All rights reserved.

Description: Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pools and vulnerability to hydrological change. Use of non-peatland-specific models could lead to bias in modeling studies of peatland-rich regions. Here, seven ecosystem models were used to simulate CO2 fluxes at three wetland sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor, sphagnum-dominated bog, over periods between 1999 and 2007. Models consistently overestimated mean annual gross ecosystem production (GEP) and ecosystem respiration (ER) at all three sites. Monthly flux residuals (simulated – observed) were correlated with measured water table for GEP and ER at the two fen sites, but were not consistently correlated with water table at the bog site. Models that inhibited soil respiration under saturated conditions had less mean bias than models that did not. Modeled diurnal cycles agreed well with eddy covariance measurements at fen sites, but overestimated fluxes at the bog site. Eddy covariance GEP and ER at fens were higher during dry periods than during wet periods, while models predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP did not depend on water table, while simulated GEP was higher during wet periods. Carbon cycle modeling in peatland-rich regions could be improved by incorporating wetland-specific hydrology and by inhibiting GEP and ER under saturated conditions. Bogs and fens likely require distinct plant and soil parameterizations in ecosystem models due to differences in nutrients, peat properties, and plant communities.