Prolonged cultured human hepatocytes as an in vitro experimental system for the evaluation of potency and duration of activity of RNA therapeutics: Demonstration of prolonged duration of gene silencing effects of a GalNAc-conjugated human hypoxanthine phosphoribosyl transferase (HPRT1) siRNA

The Coming Age of Antisense Oligos for the Treatment of Hepatic Ischemia/Reperfusion (IRI) and Other Liver Disorders: Role of Oxidative Stress and Potential Antioxidant Effect

Imbalances in the redox state of the liver arise during metabolic processes, inflammatory injuries, and proliferative liver disorders. Acute exposure to intracellular reactive oxygen species (ROS) results from high levels of oxidative stress (OxS) that occur in response to hepatic ischemia/reperfusion injury (IRI) and metabolic diseases of the liver. Antisense oligonucleotides (ASOs) are an emerging class of gene expression modulators that target RNA molecules by Watson-Crick binding specificity, leading to RNA degradation, splicing modulation, and/or translation interference. Here, we review ASO inhibitor/activator strategies to modulate transcription and translation that control the expression of enzymes, transcription factors, and intracellular sensors of DNA damage. Several small-interfering RNA (siRNA) drugs with N-acetyl galactosamine moieties for the liver have recently been approved. Preclinical studies using short-activating RNAs (saRNAs), phosphorodiamidate morpholino oligomers (PMOs), and locked nucleic acids (LNAs) are at the forefront of proof-in-concept therapeutics. Future research targeting intracellular OxS-related pathways in the liver may help realize the promise of precision medicine, revolutionizing the customary approach to caring for and treating individuals afflicted with liver-specific conditions.

Mechanistic, Functional, and Clinical Aspects of Pro-inflammatory Cytokine Mediated Regulation of ADME Gene Expression in 3D Human Liver Spheroids

During systemic inflammation, pro-inflammatory cytokines alter metabolism and transport of drugs affecting the clinical outcome. We used an in vivo like human 3D liver spheroid model to study the effects and mechanisms of pro-inflammatory cytokines on the expression of 9 different genes encoding enzymes responsible for the metabolism of > 90% of clinically used drugs. Treatment of spheroids with pathophysiologically relevant concentrations of IL-1β, IL-6, or TNFα resulted in a pronounced decrease in mRNA expression of CYP3A4 and UGT2B10 within 5 hours. The reduction of CYP1A2, CYP2C9, CYP2C19, and CYP2D6 mRNA expression was less pronounced, whereas the pro-inflammatory cytokines caused increased CYP2E1, and UGT1A3 mRNA expression. The cytokines did not influence expression of key nuclear proteins, nor the activities of specific kinases involved in the regulation of genes encoding drug metabolizing enzymes. However, ruxolitinib, a JAK1/2 inhibitor, inhibited the IL-6 dependent increase in CYP2E1 and the decrease in CYP3A4 and UGT2B10 mRNA expression. We evaluated the effect of TNFα in hepatocytes in 2D plates and found a rapid decrease in drug-metabolizing enzyme mRNA both in the absence or presence of the cytokines. Taken together, these data suggest that pro-inflammatory cytokines regulate multiple gene- and cytokine-specific events seen in in vivo and in 3D but not in 2D liver models. We propose that the 3D spheroid system is suitable for the prediction of drug metabolism under conditions of inflammation and constitutes a versatile system for short- and long-term preclinical and mechanistic studies of cytokine-induced changes in drug metabolism.

The therapeutic prospects of N-acetylgalactosamine-siRNA conjugates

RNA interference has become increasingly used for genetic therapy following the rapid development of oligonucleotide drugs. Significant progress has been made in its delivery system and implementation in the treatment of target organs. After a brief introduction of RNA interference technology and siRNA, the efficiency and stability of GalNAc-siRNA conjugates are highlighted since several oligonucleotide drugs of GalNAc have been approved for clinical use in recent years. The structure and features of GalNAc-siRNA conjugates are studied and the clinical efficiency and limitations of oligonucleotide-based drugs are summarized and investigated. Furthermore, another delivery system, lipid nanoparticles, that confer many advantages, is concluded, includ-ing stability and mass production, compared with GalNAc-siRNA conjugates. Importantly, developing new approaches for the use of oligonucleotide drugs brings hope to genetic therapy.

Pre-Clinical and Clinical Applications of Small Interfering RNAs (siRNA) and Co-Delivery Systems for Pancreatic Cancer Therapy

Pancreatic cancer (PC) is one of the leading causes of death and is the fourth most malignant tumor in men. The epigenetic and genetic alterations appear to be responsible for development of PC. Small interfering RNA (siRNA) is a powerful genetic tool that can bind to its target and reduce expression level of a specific gene. The various critical genes involved in PC progression can be effectively targeted using diverse siRNAs. Moreover, siRNAs can enhance efficacy of chemotherapy and radiotherapy in inhibiting PC progression. However, siRNAs suffer from different off target effects and their degradation by enzymes in serum can diminish their potential in gene silencing. Loading siRNAs on nanoparticles can effectively protect them against degradation and can inhibit off target actions by facilitating targeted delivery. This can lead to enhanced efficacy of siRNAs in PC therapy. Moreover, different kinds of nanoparticles such as polymeric nanoparticles, lipid nanoparticles and metal nanostructures have been applied for optimal delivery of siRNAs that are discussed in this article. This review also reveals that how naked siRNAs and their delivery systems can be exploited in treatment of PC and as siRNAs are currently being applied in clinical trials, significant progress can be made by translating the current findings into the clinical settings.

Messenger RNA Expression of Albumin, Transferrin, Transthyretin, Asialoglycoprotein Receptor, Cytochrome P450 Isoform, Uptake Transporter, and Efflux Transporter Genes as a Function of Culture Duration in Prolonged Cultured Cryopreserved Human Hepatocytes as Collagen-Matrigel Sandwich Cultures: Evidence for Redifferentiation upon Prolonged Culturing

Hepatic gene expression as a function of culture duration was evaluated in prolonged cultured human hepatocytes. Human hepatocytes from seven donors were maintained as near-confluent collagen-Matrigelsandwich cultures, with messenger RNA expression for genes responsible for key hepatic functions quantified by real-time polymerase chain reaction at culture durations of 0 (day of plating), 2, 7, 9, 16, 23, 26, 29, 36, and 43 days. Key hepatocyte genes were evaluated, including the differentiation markers albumin, transferrin, and transthyretin; the hepatocyte-specific asialoglycoprotein receptor 1 cytochrome P450 isoforms CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A7; uptake transporter isoforms SLC10A1, SLC22A1, SLC22A7, SLCO1B1, SLCO1B3, and SLCO2B1; efflux transporter isoforms ATP binding cassette (ABC)B1, ABCB11, ABCC2, ABCC3, ABCC4, and ABCG2; and the nonspecific housekeeping gene hypoxanthine ribosyl transferase 1 (HPRT1). The well established dedifferentiation phenomenon was observed on day 2, with substantial (>80%) decreases in gene expression in day 2 cultures observed for all genes evaluated except HPRT1 and efflux transporters ABCB1, ABCC2, ABCC3 (<50% decrease in expression), ABCC4 (>400% increase in expression), and ABCG2 (no decrease in expression). All genes with a >80% decrease in expression were found to have increased levels of expression on day 7, with peak expression observed on either day 7 or day 9, followed by a gradual decrease in expression up to the longest duration evaluated of 43 days. Our results provide evidence that cultured human hepatocytes undergo redifferentiation upon prolonged culturing. SIGNIFICANCE STATEMENT: This study reports that although human hepatocytes underwent dedifferentiation upon 2 days of culture, prolonged culturing resulted in redifferentiation based on gene expression of differentiation markers, uptake and efflux transporters, and cytochrome P450 isoforms. The observed redifferentiation suggests that prolonged (>7 days) culturing of human hepatocyte cultures may represent an experimental approach to overcome the initial dedifferentiation process, resulting in "stabilized" hepatocytes that can be applied toward the evaluation of drug properties requiring an extended period of treatment and evaluation.