Hepatic Regeneration—Revisiting the Myth of Prometheus

Interaction of silicon-based quantum dots with gibel carp liver: oxidative and structural modifications

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO2 QDs after 1, 3, and 7 days from their administration.QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection.Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO2 QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S-transferase activity was noted, while glutathione reductase remained unaltered.Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner.

Depletion of activated hepatic stellate cell correlates with severe liver damage and abnormal liver regeneration in acetaminophen-induced liver injury

Hepatic stellate cells (HSCs) are important part of the local 'stem cell niche' for hepatic progenitor cells (HPCs) and hepatocytes. However, it is unclear as to whether the products of activated HSCs are required to attenuate hepatocyte injury, enhance liver regeneration, or both. In this study, we performed 'loss of function' studies by depleting activated HSCs with gliotoxin. It was demonstrated that a significantly severe liver damage and declined survival rate were correlated with depletion of activated HSCs. Furthermore, diminishing HSC activation resulted in a 3-fold increase in hepatocyte apoptosis and a 66% decrease in the number of proliferating hepatocytes. This was accompanied by a dramatic decrease in the expression levels of five genes known to be up-regulated during hepatocyte replication. In particular, it was found that depletion of activated HSCs inhibited oval cell reaction that was confirmed by decreased numbers of Pank-positive cells around the portal tracts and lowered gene expression level of cytokeratin 19 (CK19) in gliotoxin-treated liver. These data provide clear evidence that the activated HSCs are involved in both hepatocyte death and proliferation of hepatocytes and HPCs in acetaminophen (APAP)-induced acute liver injury.

Identification of differentially expressed genes during proliferative response of the liver induced by follistatin

The liver mass is controlled strictly and maintained constant in normal and pathological situations. An exception is observed after an administration of follistatin, which induces proliferation in intact liver. In the present study, we identified genes differentially expressed in proliferating liver caused by overexpression of follistatin-288. Adenovirus vector encoding follistatin-288 (Ad-FS) or green fluorescent protein was injected intraperitoneally in rats. Changes in the liver weight, expression of follistatin and nuclear bromodeoxyuridine labeling were measured. Samples taken on day 5 and day 7 were used to prepare RNA for microarray analysis. The expression of the genes was confirmed by quantitative reverse transcriptase PCR. After the injection of Ad-FS follistatin mRNA peaked on day 3, which was followed by progressive increase in the protein expression. A peak in bromodeoxyuridine labeling was observed on day 7. Microarray data from day 5 and day 7 samples showed that follistatin modified the expression of 907 genes, of which 575 were overexpressed and 332 were downregulated taking into consideration a two fold change reference compared to control rats. In particular, significant increases and time related changes in gene expression after the Ad-FS injection were found in nine genes including growth differentiation factor 15 and fibroblast growth factor 21. This study confirmed that follistatin induced proliferation in intact liver, and identified candidate genes involved in follistatin-induced liver cell growth.

Isolation and analysis of a novel gene over-expressed during liver regeneration

AIM: To isolate and analyze a novel gene over-expressed during liver regeneration.

METHODS: Total RNA of regenerating liver was extracted from liver tissue after 0-4-36-36-36 hr short interval successive partial hepatectomy (SISPH). Reverse transcription-polymerase chain reaction was used to synthesize double strand cDNA, after the tissue was digested by proteinase K and Sfi A/B. The double-strand cDNA was ligated to λTriplEx2. λphage packaging reaction was performed and E. coli XL1-Blue was infected for titering and amplifying. One expressed sequence tag was probed by Dig and phage in situ hybridization was carried out to isolate positive clones. Positive recombinant λTriplEx2 was converted to the corresponding pTriplEx2, and bioinformatics was used to analyze full-length cDNA.

RESULTS: We isolated a novel full-length cDNA during liver regeneration following SISPH.

CONCLUSION: We have succeeded in cloning a novel gene, based on bioinformatics. We postulate that this gene may function in complicated network in liver regeneration. On the one hand, it may exert initiation of liver regeneration via regulating nitric oxide synthesis. On the other hand, it may protect damaged residue lobus following SISPH.

Cloning and analysizing the up-regulated expression of transthyretin-related gene (LR1) in rat liver regeneration following short interval successive partial hepatectomy

AIM: Cloning and analysizing the up-regulated expression of transthyretin-related gene following short interval successive partial hepatectomy (SISPH) to elucidate the mechanism of differentiation, division, dedifferentiation and redifferentiation in rat liver regeneration (LR).

METHODS: Lobus external sinister and lobus centralis sinister, lobus centralis, lobus dexter, lobus candatus were removed one by one from rat liver at four different time points 4, 36, 36 and 36 hr (total time: 4 hr, 40 hr, 76 hr, 112 hr) respectively. Suppression subtractive hybridization (SSH) was carried out by using normal rat liver tissue as driver and the tissue following short interval successive partial hepatectomy (SISPH) as tester to construct a highly efficient forward-subtractive cDNA library. After screening, an interested EST fragment was selected by SSH and primers were designed according to the sequence of the EST to clone the full-length cDNA fragment using RACE (rapid amplification of cDNA end). Homologous detection was performed between the full-lenth cDNA and Genbank.

RESULTS: Forward suppression subtractive hybridization (FSSH) library between 0 h and 112 h following SISPH was constructed and an up-regulated full-length cDNA (named LR1), which was related with the transthyretin gene, was cloned by rapid amplification of cDNA end. It was suggested that the gene is involved in the cellular dedifferentiation in LR following SISPH.

CONCLUSION: Some genes were up-regulated in 112 h following SISPH in rat. LR₁ is one of these up-regulated expression genes which may play an important role in rat LR.