OBJECTIVEThis study explored the dynamic expression of the E3 ubiquitin-protein ligase gene, Arkadia, in response to carbon tetrachloride (CCl4)-induced liver fibrosis in a mouse model and investigated the differential expression that occurs following treatment with the anti-fibrotic bone morphogenetic protein-7 (BMP-7).

METHODSThirty healthy male imprinting control region (ICR) mice were randomly assigned to three groups: normal (control; n = 6), CCl4-induced model group (model; n = 18), and CCl4-induced model with BMP-7 treatment group (treatment; n = 6). The model group was further divided into three subgroups (n = 6 each) for analysis at 4, 8 and 12 weeks after fibrosis induction. Liver fibrosis was induced by hypodermic injections of 60% CCl4 /peanut oil (5 mL/kg) to the hind legs of mice two-times per week in alternating legs for a period of 12 weeks. At week 9, the treatment group of CCl4-induced mice were given an intraperitoneal injection of BMP-7 (300 pg/g) simultaneously with that day's hypodermic injection of 60% CCl4 /peanut oil, and then every other day for a period of four weeks. The pathological changes in liver tissues were observed after staining with hematoxylin-eosin (HE) and Masson's trichrome. Messenger RNA (mRNA) and protein expression of Arkadia in liver were evaluated using reverse transcription-polymerase chain reaction and immunohistochemistry and Western blotting, respectively.

RESULTSMouse models of liver fibrosis were successfully established by CCl4 exposure. Arkadia, Smad7 and TGF-beta1 mRNA levels were up-regulated in the model group in a time-dependent manner (vs. control group), and BMP-7 treatment led to significant down-regulation of the CCl4-induced expression of the three genes (vs. control group: F = 812.80, 451.46, and 998.96, respectively; P less than 0.01). At week 12, the mRNA levels of Arkadia, Smad7, and TGF-b1 were significantly lower in the BMP-7 treatment group than in the model group (t = 12.108, 18.737, and 16.364, respectively; P less than 0.01). Arkadia, Smad7, and TGF-b1 protein staining was weak in the portal area of control liver tissue. In contrast, the model group showed significantly stronger staining for all three proteins in the portal area and in the cytoplasm of liver cells. The staining of Arkadia, Smad7, and TGF-b1 proteins was significantly lower in the treatment group (vs. control group: F = 8.399, 609.690, and 900.561, respectively; P < 0.01). At week 12, the protein levels of Arkadia, Smad7, and TGF-b1 were significantly lower in the treatment group than in the model group (t = 23.438, 11.667, and 42.889, respectively; P < 0.01).

CONCLUSIONArkadia expression gradually increased along with the development of liver fibrosis but was suppressed by treatment with the anti-fibrotic factor, BMP-7.