Two approaches to construct mammalian expression vector of shRNA to reduce expression and replication of HBV in vitro

Inhibition of porcine reproductive and respiratory syndrome virus replication by RNA interference in MARC-145 cells

With the ultimate aim of producing an RNA interference-mediated transgenic pig that is resistant to porcine reproductive and respiratory syndrome virus (PRRSV), we have investigated the effect of RNA interference (RNAi) on silencing the expression of viral genes in the MARC-145 cell line. Twenty small interfering RNAs (siRNAs) were designed and screened for their ability to suppress the expression of the genes ORF1b, 5, 6, and 7 from the highly virulent isolate, PRRSV-JXwn06. Of these siRNAs, the four most effective were selected and four short hairpin RNA (shRNA) expression vectors (pGenesil-1-1b-135, pGenesil-1-1b-372, pGenesil-1-6-135, and pGenesil-1-6-169) targeting ORF1b and ORF6 were constructed and delivered into MARC-145 cells. These cells were then infected with JXwn06. All four vectors inhibited the PRRSV-specific cytopathic effect (CPE). The virus titers in cells transfected with pGenesil-1-1b-135, pGenesil-1-1b-372, pGenesil-1-6-135, and pGenesil-1-6-169 were lower than that of control cells by approximately 150-, 600-, 2.3- and 1.7-fold, respectively. In addition, the expression levels of ORF1 and ORF6 were reduced compared with controls. The unglycosylated membrane protein M, encoded by ORF6, was not detectable in cells transfected with shRNA expression vectors. These results verified that RNAi can effectively inhibit PRRSV-JXwn06 replication in cultured cells in vitro. The four shRNA expression vectors are an initial step in the production of transgenic pigs with PRRSV resistance.

A natural process of cirrhosis resolution and deceleration of liver regeneration after thioacetamide withdrawal in a rat model

Characteristics of thioacetamide (TAA)-induced liver cirrhosis in rat was observed for 120 days after TAA withdrawal as part of the radiobiological study of partial liver irradiation on TAA-induced cirrhotic rats. The natural process focused on cirrhosis and regeneration was recorded as a baseline condition for the interpretation of the outcome of the partial liver irradiation study. Cirrhosis in rats was successfully induced by drinking 0.03% TAA water orally for 29 weeks with a modeling rate of 96%. After establishment of the cirrhosis model, the rats were observed for 120 days upon TAA withdrawal to investigate the dynamic changes of cirrhosis and regeneration. The following characteristics were observed: (1) Histological changes; (2) Liver functions; (3) Cirrhosis: trichrome stain, quantification of hydroxyproline in hydrolysed liver tissue and TGF-β1; (4) Liver regeneration: liver index, hepatocyte mitotic index (MI), hepatocyte proliferation index (PI) by flow cytometry, PCNA labeling index (LI) by IHC and expression of PCNA mRNA; and (5) Growth factors: serum HGF, VEGF, TGF-α, and IL-6. After TAA withdrawal, gradual improvement in liver functions was noted with decreases of ALT, AST, and ALP, and increase of PA. The resolution of cirrhosis was evident by histological improvement with attenuation of collagen fiber and decrease of TGF-β1 IHC index, and also decrease of trichrome stain and hydroxyproline content. However, cirrhosis was still existed on 120 days after TAA withdrawal. Significant deceleration of liver regeneration was demonstrated with TAA withdrawal, evidenced by decrease of MI and PI, reduced expression of PCNA mRNA and PCNA LI. In conclusion, upon TAA withdrawal hepatic cirrhosis was continuously resolved, but persisted up to 120 days, and liver regeneration was significantly decelerated.