Small interfering RNAs based therapies for intracerebral hemorrhage: challenges and progress in drug delivery systems

Intracerebral hemorrhage(ICH)is a subtype of stroke associated with higher rates of mortality.Currently,no effective drug treatment is available for ICH.The molecular pathways following ICH are complicated and diverse.Nucleic acid therapeutics such as gene knockdown by small interfering RNAs(siRNAs)have been developed in recent years to modulate ICH’s destructive pathways and mitigate its outcomes.However,siRNAs delivery to the central nervous system is challenging and faces many roadblocks.Existing barriers to systemic delivery of siRNA limit the use of naked siRNA;therefore,siRNA-vectors developed to protect and deliver these therapies into the specific-target areas of the brain,or cell types seem quite promising.Efficient delivery of siRNA via nanoparticles emerged as a viable and effective alternative therapeutic tool for central nervous system-related diseases.This review discusses the obstacles to siRNA delivery,including the advantages and disadvantages of viral and nonviral vectors.Additionally,we provide a comprehensive overview of recent progress in nanotherapeutics areas,primarily focusing on the delivery system of siRNA for ICH treatment.

WHAT CAN WE LEARN FROM VIRUS IN DESIGNING NONVIRAL GENE VECTORS

Gene therapy has emerged as a potential new approach to treat genetic disorders by delivering therapeutic genes to target diseased tissues. However, its clinical use has been impeded by gene delivery systems. The viral vectors are very efficient in delivering and expressing their carried genes, but they have safety issues in clinical use. While nonviral vectors are much safer with very low risks after careful material design, but their gene transcription efficiency is too low to be clinically used. Thus, rational design of nonviral vectors mimicking the viral vectors would be a way to break this bottleneck. This review compares side-by-side how viral/nonviral gene vectors transcend these biological barriers in terms of blood circulation, cellular uptake, endosome escape, nucleus import and gene transcription.

MSC based gene delivery methods and strategies improve the therapeutic efficacy of neurological diseases

Mesenchymal stem cells(MSCs)are promising seed cells for neural regeneration therapy owing to their plasticity and accessibility.They possess several inherent characteristics advantageous for the transplantation-based treatment of neurological disorders,including neural differentiation,immunosuppression,neurotrophy,and safety.However,the therapeutic efficacy of MSCs alone remains unsatisfactory in most cases.To improve some of their abilities,many studies have employed genetic engineering to transfer key genes into MSCs.Both viral and nonviral methods can be used to overexpress therapeutic proteins that complement the inherent properties.However,to date,different modes of gene transfer have specific drawbacks and advantages.In addition,MSCs can be functionalized through targeted gene modification to facilitate neural repair by promoting neural differentiation,enhancing neurotrophic and neuroprotective functions,and increasing survival and homing abilities.The methods of gene transfer and selection of delivered genes still need to be optimized for improved therapeutic and targeting efficacies while minimizing the loss of MSC function.In this review,we focus on gene transport technologies for engineering MSCs and the application of strategies for selecting optimal delivery genes.Further,we describe the prospects and challenges of their application in animal models of different neurological lesions to broaden treatment alternatives for neurological diseases.

Antitumor and off-target effects of cholesterol-conjugated let-7a mimics in an orthotopic hepatocellular carcinoma xenograft nude mouse model

Objective: To explore the antitumor and potential off-target effects of systemically delivered cholesterol-conjugatedlet-7a mimics(Chol-let-7a) and control mimics(Chol-miRCtrl) on hepatocellular carcinomain vivo.Methods: The antitumor effects of two intravenous dosing regimens ofChol-let-7a on heptocellular carcinoma growth were compared using an orthotopic xenograft mouse model. Off-targets were analyzed with histopathological and ultrapathological features of heparenal tissue and cells in theChol-let-7a-, Chol-miRCtrl-, and saline-treated (blank) xenograft mice and normal control mice. Then,let-7a abundance in orthotopic tumors, corresponding paracancerous hepatic tissue, and normal liver tissue from healthy nude mice was examined by reverse transcription-polymerase chain reaction. The distribution ofChol-let-7a andChol-miRCtrl in vivo was examined by whole-animal imaging and frozen-sections observation. The experiments were approved by the Institutional Research Board of Peking Union Medical College Hospital.Results: Continuous treatment withChol-let-7a resulted in tumors that were 35.86% and 40.02% the size of those in theChol-miRCtrl and blank xenograft group (P < 0.01 andP < 0.01, respectively), while intermittent dosing withChol-let-7a resulted in tumors that were 65.42% and 56.66% the size of those in theChol-miRCtrl and the blank control group, respectively (P < 0.05 andP < 0.05). In addition, some histopathological and ultrapathological features were only observed after treatment with the two cholesterol-conjugated molecules, however mild with intermittent dosingChol-let-7a treatment, such as diffuse sinusoidal dilation and edema, primarily around the centrolobular vein in heptic tissues;mild hypercellularity with dilated capillary lumens in the renal tissue;and some organelle abnormalities found in heptic and renal cells. Furthermore, whole-animal imaging showed thatChol-let-7a andChol-miRCtrl were predominantly distributed in the liver, kidney, and bladder regions after injection, and that the concentration ofChol-let-7a andChol-miRCtrl in the kidney and the bladder decreased much slowly in the xenograft animals, especially in theChol-miRCtrl group. Finally, RT-PCR analysis showed thatlet-7a levels were significantly increased in Chol-let-7a-treated xenografts compared withChol-miRCtrl group (P=0.003) and blank xenograft group (P=0.001);however, the level was only equivalent to 50.6% and 40.7% of that in paracancerous hepatic tissue and hepatic tissue in normal mice, respectively.Conclusions: Chol-let-7a, administered either continuously or intermittently, showed effective antitumor efficacy.Chol-let-7a had some off-target effects, such as mild acute hepatitis-like inflammation and non-specific drug-induced kidney injury. The intermittent dosing regimen resulted in less damage than the continuous regimen, while maintaining relatively satisfactory antitumor efficacy, which could be useful for the investigation and possible clinical use of miRNA treatment regimens in the future.