Delivering Naked siRNA by Direct Injection

This blog has featured methods for delivering siRNA in vivo by intrathecal injections. These methds all highlight conjugation with novel cationic lipid based carriers like i-Fect ™. Here we highlight delivery by direct injection:

Dr. Matthew Farrer and his team, including researchers from Alnylam, have successfully demontrated the delivery of naked siRNA by direct injection. In this study, they delivered chemically modified murine and human alpha-synuclein (SNCA) siRNAs to the hippocampus by direct injection resulting in silencing of gene expression.

To learn more access:

In vivo silencing of alpha-synuclein using naked siRNA Jada Lewis, Heather Melrose, David Bumcrot, Andrew Hope, Cynthia Zehr, Sarah Lincoln, Adam Braithwaite, Zhen He, Sina Ogholikhan, Kelly Hinkle, Caroline Kent, Ivanka Toudjarska, Klaus Charisse, Ravi Braich, Rajendra K. Pandey, Michael Heckman, Demetrius M Maraganore, Julia Crook, Matthew J Farrer. Molecular Neurodegeneration 2008, 3:19 (1 November 2008).

ACIC3 Receptors Knockdown in vivo

Researchers using siRNA complexed with our i-Fect ™ transfection regent have successfully knocked down ASIC3 Receptors in vivo. This publication joins the growing parade (starting with Luo et al, 2005) that refererence successuful modulation of receptors involved in pain using siRNA complexes.

These studies all share animal behavior studies showing a marked change in response to pain stimuli after treatment.

In this study, Dr. Eric Lingueglia and his team found Peripheral ASIC3 channels are thus essential sensors of acidic pain and integrators of molecular signals produced during inflammation where they contribute to primary hyperalgesia.

Emmanuel Deval, Jacques Noël, Nadège Lay, Abdelkrim Alloui, Sylvie Diochot, Valérie Friend, Martine Jodar, Michel Lazdunski and Eric Lingueglia. ASIC3, a sensor of acidic and primary inflammatory pain. The EMBO Journal advance online publication 16 October 2008; doi: 10.1038/emboj.2008.213

Cy3-labelled siRNA no. 1121 and its corresponding scramble (no. 1121S; GCTCACACTACGCAGAGAT) synthesized by MWG Biotech (Germany) were injected in rats by intrathecal bolus to the lumbar region of the spinal cord once a day for 3 days before the induction of inflammation with CFA. Each 10-ml injection corresponded to 2 mg of siRNA complexed with i-Fect siRNA transfection reagent (Neuromics) at a ratio of 1:4 (w:v) (Luo et al, 2005), following the supplier’s suggested protocol. siRNA uptake in lumbar DRGswas monitored by fluorescence microscopy on cryostat sections 24 h after a single intrathecal injection.

Here’s a synopsis of results:
Inflammation was produced by CFA injection, which led to primary heat hyperalgesia, and this hyperalgesia was drastically reduced by the ASIC3 blocker APETx2 injected subcutaneously, which only access cutaneous nociceptors. It was also drastically reduced when, before triggering the inflammation state, intrathecalinjections of an siRNA against ASIC3 had induced a knockdown of ASIC3 expression in lumbar DRGs.

siRNA-mediated gene silencing

Dr. Josephine Lai (Professor of Pharmacology, University of Arizona) is a pioneer in developing experimental designs and methods for delivering siRNA to the CNS for gene expression analysis.She and her team have documented these in the publication:


Modulating Sensory Systems Using RNAi(pdf - 187Kb)© 2007 Lai


For researchers desiring to effectively deliver siRNA to the CNS for gene expression analysis of specific receptors, this publication offers proven methods. These include:

• The Choice of siRNA


• Choosing and Optimizing Transfection Reagents for siRNA Delivery to the Nervous System
  
• Delivery Systems-Microinjection and Infusion (using mini-osmotic pumps)
  
• Validation

We will continue to track advances by Dr. Lai and team.

Transfecting Sympathetic Neurons

GDNF and Ret are important to the growth, maintenance and survival of Neurons. The GDNF ligands act via activation of Ret. Every step towards understanding the intricacies of this pathway, brings researchers closer towards unlocking the code for Neurodegenerative Disease therapies.

siRNA is an important tool for studying the Neurotrophic pathways as researchers can use it to modulate the expression of related receptors. The tricky part is getting sufficient siRNA into neurons to do the appropriate studies of how modulating targeted genes results in changes in protein expression.

Here Drs. Cynthia Tsui and Brian Pierchala have published results from there studies of C2AP and Cbl-3/Cbl-c and Ret Transduction. One of the keys to this study was using siRNA to silence CD2AP and Cbl-3 expression. By turning these off they were able to identify a critical checkpoint in the Ret pathway.

Cynthia C. Tsui and Brian A. Pierchala CD2AP and Cbl-3/Cbl-c Constitute a Critical Checkpoint in the Regulation of Ret Signal TransductionJ. Neurosci., Aug 2008; 28: 8789 - 8800 ; doi:10.1523/JNEUROSCI.2738-08.2008.

...Control, CD2AP, and Cbl-3 siRNAs (Applied Biosystems/Ambion) were transfected into 4 DIV sympathetic neurons using the i-Fect ™ reagent according to the manufacturer’s instructions (Neuromics). Transfection efficiency was determined by the cotransfection of a fluorescently labeled nontargeting, control siRNA (siGLO RISC-free siRNA; Dharmacon RNA Technologies). Immunoblotting of the targeted proteins determined that the maximal knockdown of protein expression was observed 72 h after siRNA transfection. Greater than 90% of SCG neurons were transfected, as ascertained by the level of intracellular fluorescence of the siGLO siRNA.

Down Regulating the Smad and Neuro-regeneration

The inventors down regulated Smad 2/3 (an inhibitor of neuro-regeneration) in vivo via delivery of siRNA to the spinal cord using catheters.

Inhibiting smad signaling promotes neuron regeneration.
Inventors: Fan Wang, Zhigang He
USPTO Application #: 20080031911
Inhibition of Smad2/3 Signaling Promotes Axonal Regeneration after Spinal Injury in Rats-Gene Expression Knockdown in vivo!
One hour after the spinal cord is lesioned, the rats in the SB-505124 group receive a bolus injection of SB-505124 (30 mg/kg) in 0.9% saline administered via a tail vein. The treatment is repeated every 24 hours on days 1 through 7 post-lesion. Vehicle only control rats undergo the same treatment but are injected with an equal volume of 0.09% saline in a tail vein. At the same treatment time points as the SB-505124 group, the Smad2/3 siRNA group and corresponding controls receive 10 .mu.l rat Smad2/3 siRNA (Dharmacon, Lafayette, Colo.), mismatch siRNA, or transfection reagent only delivered to the spinal cord via the catheters. The siRNA (or mismatch siRNA control) complexes are prepared immediately prior to administration by mixing the RNA solution (200 .mu.M in annealing buffer) with a transfection reagent, i-Fect ™ . (Neuromics, Edina, Minn.), in a ratio of 1:4 (w:v). At this ratio, the final concentration of RNA as an RNA/lipid complex is 2 .mu.g in 10 .mu.l.

siRNA and Diabetes

I'll be keeping my eyes on this and post updates.

Quark Pharmaceuticals Announces First Patient Dosing by Pfizer in Phase II Trial of RNAi Therapy in Diabetic M
Clinical Program Leverages Quark's RNAi Technology FREMONT, Calif., July 30 /PRNewswire/ -- Quark Pharmaceuticals, Inc., a development-stage pharmaceutical company discovering and developing novel RNA interference (RNAi)-based therapeutics,...

Improving 27mer DsiRNA Performance

The DsiRNA story marches forward with yet another important publication. We will give you an opportunity to upload the fulltext article at the end of this posting.

Dr. Mark Behlke, Dr John Rossi and team have been gaining deeper understanding of the Mechanism of Dicer-substrate small-interfering RNA (DsiRNA) processing. This understanding is leading to better and better designs of the RNA duplexes. These designs or chemical modifications are necessary steps in the drug design and development process.

This publication looks at design from the perspective of:

Nuclease Stability
Pharmacokinectics
immune response

I believe this is an important publication for researchers wanting to better understand:

The mechanisms behind successful delivery of DsiRNA for gene expression studies.
Variations in potency.

upload article: oligo-18-p187-2008-collingwood-dsirna-modifications1