Modified Spared Nerve Injury Surgery Model of Neuropathic Pain in Mice
January 25th, 2022
The modified surgery is a simplified method for mouse or rat spared nerve injury model that requires only one ligation and one cut to injure both common peroneal and sural nerves.
To cut and ligate a common peroneal and sural nerves with intact tibial nerve, defined as SNIt, has much less motor deficit with a shorter learning curve. The modified mouse SNIt surgery procedure was developed to ligate the common peroneal and sural nerves together with only one nerve ligation and one nerve cutting, which results in shortened procedure time. To begin, place the mouse in a right lateral position.
Keep the left leg up with knee flexion, and secure it with adhesive tape. Remove the hair around the thigh and knee area with an electric shaver and hair removal cream. After placing the mouse on a new sterile surgery towel, disinfect the skin with 2%chlorhexidine and 70%alcohol.
Secure it with adhesive tape. Cut a one centimeter incision starting at one third of the horizontal line, crossing the knee with an approximately 30 degree angle from the vertical line with a scalpel. Two white lines can be visualized under the biceps femoris muscle after separating skin incision with the medial cephalad thick line above the femur and lateral caudal thin line above sciatic nerve.
Blunt dissect the biceps femoris muscle along the caudal white line using curved micro forceps and micro scissors to expose the sciatic nerve. Differentiate the three branches from the sciatic nerve at the superior edge of the gastrocnemius muscle. The tibial nerve has the biggest diameter passing under the gastrocnemius muscle, whereas the sural nerves are lateral and smallest in diameter.
The common peroneal nerve runs above the gastrocnemius muscle. Depending on how the biceps femoris muscle is dissected and opened, visualize the common peroneal nerve as lateral or medial to the tibial nerve. Then separate the common peroneal and the sural nerves from the neighboring tissues using curved micro forceps.
Ligate the common peroneal and sural nerves together with a 6/0 suture. Both nerves run above the gastrocnemius muscle, but the tibial nerve passes under the gastrocnemius muscle. Observe the limb for contraction following the tight ligature.
Cut nerve at a distal part within two to four millimeters of the ligation with a pair of micro scissors. Ensure that the tibial nerve remains untouched during the whole procedure. Close the muscular layer with a 6/0 silk suture and close the skin incision with wound clips.
The results show that the modified approach took almost half the amount of procedure time to perform SNlt compared with the control of the traditional approach. No difference in Von Frey assessment was observed in the two groups at baseline. The traditional method and the modified method induced similar mechanical hypersensitivity on the ipsilateral side from postoperative day one to postoperative day 14.
The percentage response between traditional and modified methods showed similar mechanical hypersensitivity on the ipsilateral side from baseline. Easy and rapid exposure of the sciatic nerve, accurate identification of the common peroneal, tibial, and sural nerves, cutting and ligation of the common peroneal and sural nerves are the three critical steps in this protocol. The method was successfully developed to mimic peripheral nerve injury cardio symptoms and randomized to study the molecular and cellular mechanism of neuropathic pain.
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Overview
This study presents a modified surgical technique for inducing spared nerve injury in mice, combining the common peroneal and sural nerve ligation into a single procedure. This approach reduces the complexity and time required for the surgery, allowing for easier assessment of neuropathic pain mechanisms.
Key Study Components
Area of Science
- Neuroscience
- Surgical methods
- Neuropathic pain models
Background
- Traditional nerve injury models often involve complex procedures.
- The need for simplified protocols to study neuropathic pain is critical.
- Comparative analyses of surgical methods can lead to improved animal welfare and efficiency.
- A focus on reducing learning curves for researchers is essential.
Purpose of Study
- To simplify the surgical approach for nerve injury in rodents.
- To reduce operation time without compromising the efficacy of injury.
- To enable more accessible studies on the molecular and cellular mechanisms of neuropathic pain.
Methods Used
- The study utilized a mouse model for conducting the modified surgery.
- Involved ligation of both the common peroneal and sural nerves while preserving the tibial nerve.
- The procedure is characterized by a one-ligation, one-cut technique.
- Key surgical steps included positioning, disinfection, incision, isolation, and ligation of the nerves.
- Performed evaluations through postoperative assessments comparing traditional methods.
Main Results
- The modified surgery significantly reduced procedure time by almost half compared to traditional methods.
- No differences in mechanical hypersensitivity were noted between the modified and traditional methods at baseline and after surgery.
- Both methods induced similar responses in terms of neuropathic pain assessment over the studied duration.
- Streamlined exposure and identification of critical nerve structures were highlighted as significant advancements.
Conclusions
- This modified surgical technique demonstrates a valuable approach for studying peripheral nerve injury and associated pain mechanisms.
- The simplification of surgical methods has implications for enhancing procedural efficacy in research.
- Facilitating accurate surgical outcomes contributes to better understanding of neuropathic pain syndromes.
Frequently Asked Questions
Executive Industry Relevance
This modified SNIt surgery model streamlines neuropathic pain research by reducing procedural complexity and time while preserving model fidelity. The approach supports target validation and mechanistic de-risking in preclinical discovery by enabling reproducible, scalable induction of peripheral nerve injury with minimal motor confounding. It enhances translational continuity from early discovery through preclinical validation by providing a disease-relevant system for evaluating analgesic candidates.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses in peripheral neuropathic pain pathways with reduced motor deficit confounding.
- Operational Value: Shortens learning curve and procedure time, increasing throughput for target validation studies.
- Predictive Value: Supports biological de-risking by modeling sensory-specific nerve injury relevant to human neuropathic pain conditions.
Screening & Assay Development
- Scientific Value: Produces consistent mechanical hypersensitivity readouts suitable for assay standardization and compound screening.
- Operational Value: Facilitates reproducible preparation of validated biological systems for downstream analgesic evaluation.
- Scalability: Streamlined surgery enables platform reuse across multiple screening campaigns.
Translational & Preclinical Research
- Scientific Value: Maintains disease relevance through sensory-specific nerve injury that mirrors certain human neuropathic pain etiologies.
- Operational Value: Ensures continuity from discovery to preclinical validation via standardized injury induction.
- Risk Mitigation: Supports predictive confidence in lead identification by reducing procedural variability.
Pipeline & Workflow Integration
The method integrates into the discovery continuum from target validation through lead identification to preclinical efficacy testing by providing a reliable neuropathic pain model.
- Discovery Biology: Supports hypothesis testing and pathway clarification in peripheral neuropathic pain mechanisms.
- Screening: Enables assay readiness through consistent mechanical hypersensitivity outputs.
- Analytics: Provides quantitative dependent variable measurements (Von Frey thresholds) for comparing analgesic effects.
- Translational Research: Connects to preclinical continuity via reproducible, scalable injury model.
- Enterprise Reuse: Positions the technique as a reusable capability for neuropathic pain programs rather than a single-use procedure.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation through mechanistically relevant nerve injury model.
- Operational Value: Standardization, reproducibility, and reduced procedure time enhance laboratory efficiency.
- Strategic Value: Better go/no-go decisions through reduced biological noise and improved data quality.
- Portfolio Impact: Risk-adjusted prioritization of analgesic candidates based on reliable preclinical pain models.
Implementation Considerations
- Requires expertise in rodent microsurgery and peripheral nerve identification.
- Necessitates microsurgical instruments, sutures, and postoperative pain assessment tools (e.g., Von Frey filaments).
- Demands cross-team standardization of surgical technique and postoperative monitoring protocols.
- Involves adaptation considerations for different mouse strains or ages affecting nerve accessibility.
- Practical limitation: Success depends on precise nerve isolation to avoid tibial nerve damage, which could introduce motor confounding.
