Follistatin allows efficient retroviral-mediated gene transfer into rat liver

Novel vectors and approaches for gene therapy in liver diseases

Gene therapy is becoming an increasingly valuable tool to treat many genetic diseases with no or limited treatment options. This is the case for hundreds of monogenic metabolic disorders of hepatic origin, for which liver transplantation remains the only cure. Furthermore, the liver contains 10-15% of the body's total blood volume, making it ideal for use as a factory to secrete proteins into the circulation. In recent decades, an expanding toolbox has become available for liver-directed gene delivery. Although viral vectors have long been the preferred approach to target hepatocytes, an increasing number of non-viral vectors are emerging as highly efficient vehicles for the delivery of genetic material. Herein, we review advances in gene delivery vectors targeting the liver and more specifically hepatocytes, covering strategies based on gene addition and gene editing, as well as the exciting results obtained with the use of RNA as a therapeutic molecule. Moreover, we will briefly summarise some of the limitations of current liver-directed gene therapy approaches and potential ways of overcoming them.

Beneficial effects of follistatin in hepatic ischemia-reperfusion injuries in rats

BACKGROUND

Ischemia-reperfusion injury has been demonstrated in a variety of clinical settings. The morbidity associated with liver transplantation and major hepatic resections is partly a result of ischemia-reperfusion injury. Follistatin, an activin-binding protein, binds to activins and subsequently blocks their action. It was reported that blockade of the action of activin with administration of follistatin accelerates recovery from ischemia renal injury. This study was conducted to investigate the involvement of the activin-follistatin system in hepatic ischemia-reperfusion injury.

METHODS

Total hepatic ischemia for 30 min was performed followed by reperfusion in a rat model. Rats were divided into two groups: a follistatin group and a control group. Follistatin (1 μg/body), which is an activin-binding protein, was administered at the time of reperfusion.

RESULTS

Though 80% of animals survived in the follistatin group, four of five animals died in the control group within 3 days after reperfusion (p<0.05). AST was significantly lower at 3 h after reperfusion in the follistatin group (p<0.05). LDH was also lower at 6 h after reperfusion in the follistatin group (p<0.05). Follistatin inhibited the mRNA expression of the βA subunit of activin. Moreover, the expression of IL-6, which is an inflammatory cytokine, was suppressed at 6 h after reperfusion in the follistatin group (p<0.05).

CONCLUSIONS

The present study demonstrated that treatment with follistatin reduced the expression of IL-6 and activin resulting in beneficial support for hepatic ischemia-reperfusion injuries.

Progress toward liver-based gene therapy

The liver is involved in the synthesis of serum proteins, regulation of metabolism and maintenance of homeostasis and provides a variety of opportunities for gene therapy. The enriched vasculature and blood circulation, fenestrated endothelium, abundant receptors on the plasma membranes of the liver cells, and effective transcription and translation machineries in the hepatocytes are some unique features that have been explored for delivery, and functional analysis, of genetic sequences in the liver. Both viral and non-viral methods have been developed for effective gene delivery and liver-based gene therapy. This review describes the fundamentals of gene delivery, and the preclinical and clinical progress that has been made toward gene therapy using the liver as a target.

EGF Receptor Activation Decreases Retroviral Gene Transfer through Protein Kinase C-δ

Although much progress has been made in the design of retrovirus vectors, the interactions of recombinant retrovirus with host cells remain largely elusive. The inability of recombinant retrovirus to transduce non-dividing cells prompted several studies to determine optimal cocktails of growth factors and/or extracellular matrix molecules to promote gene transfer to slowly diving cells and stem cells. In contrast to previous reports that growth factors increased gene transfer, we found that treatment of human epidermal keratinocytes and several cell lines with epidermal growth factor receptor (EGFR) ligands EGF, transforming growth factor-alpha, or heparin-binding-EGF decreased gene transfer. Conversely, treatment with an EGFR function-blocking antibody or inhibition of EGFR tyrosine phosphorylation enhanced gene transfer in a dose-dependent manner. In addition, blocking protein kinase C (PKC)-delta but not PKC-zeta, with chemical inhibitors or small interfering RNA reversed the effects of EGF and restored gene transfer, indicating that the effect of EGFR activation is mediated through PKC-delta. Lastly, cell cycle analysis showed that the effect of EGFR activation on retroviral gene transfer was independent of the cell cycle status of target cells. Our results implicate EGFR and PKC-delta in retroviral infection and may have implications for retrovirus gene transfer or design of antiretroviral therapies.

Early gene expression during natural spinal cord regeneration in the salamander Ambystoma mexicanum

In contrast to mammals, salamanders have a remarkable ability to regenerate their spinal cord and recover full movement and function after tail amputation. To identify genes that may be associated with this greater regenerative ability, we designed an oligonucleotide microarray and profiled early gene expression during natural spinal cord regeneration in Ambystoma mexicanum. We sampled tissue at five early time points after tail amputation and identified genes that registered significant changes in mRNA abundance during the first 7 days of regeneration. A list of 1036 statistically significant genes was identified. Additional statistical and fold change criteria were applied to identify a smaller list of 360 genes that were used to describe predominant expression patterns and gene functions. Our results show that a diverse injury response is activated in concert with extracellular matrix remodeling mechanisms during the early acute phase of natural spinal cord regeneration. We also report gene expression similarities and differences between our study and studies that have profiled gene expression after spinal cord injury in rat. Our study illustrates the utility of a salamander model for identifying genes and gene functions that may enhance regenerative ability in mammals.