Protocol
sdASO in vivo protocol
Protocol for self-delivering antisense oligonucleotides in animal models
Self-delivering antisense oligonucleotides (sdASO) are used in animal models.
Protocol overview
The sdASO in vivo application is a five-step process:
- 01Prepare sdASO formulation in appropriate buffer
- 02Select appropriate administration route
- 03Administer to study animals at calculated dosage
- 04Monitor and collect samples at optimal timepoints
- 05Analyze target knockdown in tissues of interest
This protocol can be adapted for different animal models, administration routes, and study endpoints based on the specific research needs.
Key advantages
- No specialized delivery required: Unlike traditional ASOs or siRNAs, sdASO products do not require complex formulations or conjugation for in vivo efficacy
- Multiple administration routes: Tissue uptake has been reported after intravenous, subcutaneous, intraperitoneal and intrathecal injection (the studies are on the publications page)
- Broad tissue distribution: Accumulates in multiple organs and tissues
Administration routes and anatomic sites
Each route pictured above, with its anatomic site:
- Intravenous, IV: Lateral tail vein. Needle tip positioned within a lateral tail vein and directed proximally.
- Intraperitoneal, IP: Right lower abdominal quadrant. Needle tip placed in the peritoneal cavity through the right lower abdominal quadrant, away from the midline.
- Subcutaneous, SC: Dorsolateral flank. Needle tip positioned beneath intact skin within the subcutaneous tissue plane.
- Intramuscular, IM: Proximal quadriceps muscle. Needle tip positioned in the proximal quadriceps, clear of the posterior sciatic region.
- Intrathecal injection, IT: Lower lumbar L5-L6 interspace. Needle enters through the L5-L6 interspace, immediately cranial to the iliac crest, with the tip in the subarachnoid space.
- Intrathecal catheter, IT: Lumbar catheter and dorsal port. A lumbar intrathecal catheter advances cranially within the subarachnoid space and connects to a dorsal access port.
Materials and reagents
Required items
- AUM BioTech sdASO (lyophilized or stock solution)
- Sterile formulation buffer (PBS, saline, or specialized buffer)
- Administration equipment:
- Sterile syringes and needles (appropriate gauge for selected route)
- Alcohol swabs
- Restrainers (if needed for proper animal handling)
- Animal subjects (appropriate for study design)
- Sample collection materials:
- Surgical tools (for tissue collection at endpoint)
- Blood collection tubes/needles (if performing PK or monitoring)
- RNase-free collection tubes
- RNA preservation reagent
- Liquid nitrogen (for snap freezing samples)
- Analysis materials:
- RNA extraction kit
- qRT-PCR reagents or other RNA analysis tools
- Protein extraction buffers (if analyzing protein knockdown)
- Western blot or ELISA reagents (if applicable)
Detailed protocol
Step 1: Animal preparation
Prepare animals according to institutional guidelines and study requirements.
- Ensure animals have acclimated to facility conditions for at least 5-7 days prior to study initiation.
- Record baseline measurements (weight, behavior, clinical parameters) before administering sdASO.
- Group animals appropriately based on study design (treatment groups, controls, etc.).
- Fast animals if required by the administration protocol (typically not necessary for most routes).
Note: All animal studies should be conducted in accordance with institutional animal care guidelines and with proper ethical approvals. Ensure that personnel are properly trained in animal handling and administration techniques.
Step 2: sdASO formulation preparation
Prepare sdASO formulation at the appropriate concentration for the selected administration route and dosage.
- Resuspend lyophilized sdASO in sterile PBS, saline, or appropriate buffer to the desired concentration.
- The concentration follows from the target dose and the administration volume. The dosing table below gives the dose for the mouse, and the administration step gives the volume for the intravenous, subcutaneous, intraperitoneal and intrathecal routes.
- Calculate the required volume based on animal weight and the target dose. Testing a dose range of 3-30 mg/kg in mice is recommended. Lower and higher doses may be needed, depending on the administration route and on how long activity has to be sustained. The dosing table below adds a starting dose and a maximum for the mouse.
- Filter sterilize the solution through a 0.22 μm filter if possible.
- Prepare formulations fresh on the day of administration when possible, or store at 4°C for no more than 24 hours.
Important: Avoid multiple freeze-thaw cycles of sdASO formulations. For studies requiring multiple dosing days, prepare fresh formulations each day or store aliquots at -20°C and thaw only once before use.
Step 3: sdASO administration
Administer the sdASO formulation using the appropriate route for the target tissue and research objectives.
- Intravenous (IV) administration: For broader systemic distribution, inject into the tail vein (mice) or appropriate vein according to species. Use a maximum volume of 5-8 mL/kg and inject slowly (over 20-30 seconds).
- Subcutaneous (SC) administration: Inject into the loose skin of the neck or flank. Maximum recommended volume is 10 mL/kg for mice.
- Intraperitoneal (IP) administration: Inject into the peritoneal cavity after proper restraint. Maximum recommended volume is 10 mL/kg for mice.
- Intrathecal (IT) administration: For CNS targeting, inject directly into the intrathecal space. This requires specialized training and typically uses volumes of 5-10 μL in mice.
- Other routes: sdASO can also be administered via local injection to specific tissues (e.g., intramuscular, intraocular, intracerebral) depending on research needs.
Route selection tip: Route selection should be based on the target tissue. IV administration typically yields good distribution to highly perfused tissues (liver, kidney, heart), while SC provides more sustained release. For CNS applications, intrathecal administration puts the oligonucleotide into the cerebrospinal fluid and so bypasses the blood-brain barrier rather than crossing it.
Step 4: Monitoring and sample collection
Monitor animals post-administration and collect samples at appropriate timepoints.
- Monitor animals for any adverse reactions immediately after administration and at regular intervals throughout the study.
- Collect blood samples at predetermined timepoints if pharmacokinetic analysis is part of the study.
- For terminal timepoints, collect target tissues according to the study design. When knockdown is maximal varies with the target, the tissue, the dose and the administration route. Collect at more than one timepoint rather than at a single harvest.
- Process each tissue appropriately:
- For RNA analysis: Either snap freeze in liquid nitrogen or preserve in RNA stabilization reagent
- For protein analysis: Snap freeze or prepare fresh lysates as appropriate
- For histological analysis: Fix in appropriate fixative (e.g., 4% paraformaldehyde)
Note: The kinetics of knockdown vary by tissue and target. Multiple timepoints are recommended for initial studies to establish optimal analysis timepoints.
Step 5: Target knockdown analysis
Analyze collected samples to evaluate the efficacy of sdASO-mediated target knockdown.
- Extract RNA from tissue samples using an appropriate RNA isolation method. Maintain RNase-free conditions to ensure sample quality.
- Perform qRT-PCR to quantify target RNA levels relative to untreated controls and normalized to appropriate housekeeping genes.
- For protein targets, extract proteins and perform Western blot, ELISA, or other appropriate protein quantification methods.
- Analyze functional endpoints relevant to the study (e.g., behavioral assessments, physiological measurements, biochemical parameters).
- If using fluorescently labeled sdASO, tissue distribution can be visualized using fluorescence microscopy on frozen sections.
Analysis tip: It is strongly recommended to include both dose escalation and time course components in pilot studies to determine the optimal dose and timepoint for the specific target and tissue. Knockdown efficacy depends on the target, tissue, dose, and administration route.
Reference guidelines
The tables below provide guidelines for dosing and administration routes:
| Animal model | Typical dose range | Starting dose | Maximum recommended dose |
|---|---|---|---|
| Mouse | 3-30 mg/kg | 5 mg/kg | 50 mg/kg |
| Administration route | Target tissues | Advantages | Considerations |
|---|---|---|---|
| Intravenous (IV) | Liver, kidney, spleen, lung, heart | Rapid distribution, high liver uptake | Requires skilled technique, limited CNS distribution |
| Subcutaneous (SC) | Systemic with prolonged exposure | Easy administration, sustained release | Slower onset than IV, may require higher doses |
| Intraperitoneal (IP) | Liver, kidney, intestine, peritoneal tissues | Relatively easy administration | Variable absorption, potential for incorrect administration |
| Intrathecal (IT) | CNS (brain, spinal cord) | Direct CNS access, bypasses BBB | Technically challenging, specialized training required |
| Intramuscular (IM) | Muscle tissue | Local targeting of muscle tissue | Limited distribution beyond injection site |
Dosing notes
- The doses provided are general guidelines; optimal doses may vary depending on the specific sdASO, target, and application.
- For initial studies, a dose-response approach across the guidance range (3-30 mg/kg in mice) is recommended to determine the optimal dose for the target.
- For long-term studies, repeated dosing may be necessary.
Tips and troubleshooting
Optimization tips and best practices
Pilot studies
Begin with small pilot studies incorporating both dose escalation and time course components. This will help establish optimal dosing, administration routes, and sampling timepoints before proceeding to larger studies.
Multiple controls
Include proper controls: untreated animals, vehicle-only, non-targeting/scrambled sdASO, and positive controls (if available). This comprehensive control strategy helps differentiate specific knockdown effects from non-specific responses. The non-targeting group is where an innate immune response to the chemistry would show, so read it rather than assume the chemistry is silent.
Tissue collection
Process tissues immediately after collection to preserve RNA quality. Either snap-freeze in liquid nitrogen or place in RNA stabilization solution within minutes of collection. Avoid repeated freeze-thaw cycles of tissue samples.
Multi-level analysis
Analyze knockdown at multiple levels: mRNA (qRT-PCR), protein (Western blot, IHC, or ELISA), and functional outcomes. This comprehensive assessment provides a complete picture of target modulation efficacy.
Troubleshooting common issues
Low or variable knockdown efficiency
Increase dose: If knockdown is lower than expected, consider increasing the dose. A dose-response study across the guidance range (3-30 mg/kg) can help determine the optimal dose.
Optimize administration route: Different routes provide varying distribution patterns. Consider switching routes if target tissues show inadequate exposure.
Extend time course: Peak knockdown may occur later than anticipated. Collect samples at multiple timepoints after administration (e.g., 24, 48, 72, and 96 hours) to identify peak knockdown.
Check tissue collection and processing: Ensure tissues are collected and processed properly to maintain RNA quality. Degraded RNA can lead to inaccurate measurements.
Consider multiple doses: For some targets or tissues, multiple administrations may provide better knockdown than a single dose.
Adverse reactions or toxicity
Reduce dose: If toxicity is observed, reduce the dose or consider alternative administration routes.
Slow injection rate: For IV administration, injecting too rapidly can cause acute reactions. Ensure injections are performed slowly and steadily.
Check formulation: Ensure the buffer is appropriate (pH 7.2-7.4) and free of endotoxins or other contaminants.
Monitor liver and kidney function: ASOs can sometimes affect liver enzymes or kidney function. Consider monitoring these parameters, especially at higher doses.
Distinguish target-mediated effects: Some adverse effects may be due to successful target knockdown rather than toxicity of the oligonucleotide itself. Include non-targeting controls to differentiate these possibilities.
Poor tissue distribution
Consider fluorescent labeling: Fluorescently labeled sdASO can help visualize tissue distribution and cellular uptake.
Change administration route: Different routes lead to different distribution patterns. IV typically provides good distribution to liver, kidney, and other highly perfused organs. For CNS targets, IT administration may be necessary.
Increase dose or frequency: Higher doses or multiple administrations may improve distribution to less accessible tissues.
Special considerations for CNS: The blood-brain barrier limits distribution to CNS tissues from systemic administration. For CNS targets, consider intrathecal, intracerebroventricular, or intracerebral administration.
Storage and additional information
Storage conditions
- Store lyophilized sdASO at -20°C upon receipt.
- Reconstituted stock solutions should be stored in single-use aliquots at -20°C.
- Avoid repeated freeze-thaw cycles, as they may affect sdASO stability and efficacy.
- Formulated sdASO solutions for in vivo administration should be prepared fresh when possible. If storage is necessary, keep at 4°C for no more than 24 hours.
Additional considerations
- Duration of effect: How long knockdown holds depends on the target and the tissue, and it is read on a time course in the study's own tissue rather than taken from a typical figure.
- Species considerations: While the basic principles apply across species, doses may need adjustment for larger animals.
- Biodistribution: sdASO distribution varies by tissue. Which tissues it reached is read in the study's own animals: a fluorescently labelled sdASO can be imaged on frozen sections, as the analysis step describes.
Note
All animal studies should be conducted in accordance with institutional animal care guidelines and with proper ethical approvals.
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