wound healing model #3

Traumatic Optic Nerve Injury Model

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Model Introduction

Traumatic Optic Neuropathy (TON) refers to a group of serious blinding diseases caused by direct or indirect trauma leading to ischemia, edema, inflammation, transection, or atrophy of the optic nerve. The incidence of this disease in patients with craniocerebral injury is approximately 0.5%–5%. The prognosis is generally poor, often leaving permanent visual impairment, and it remains a significant cause of disability resulting from traumatic brain injury (TBI).

Currently, there is a lack of effective clinical treatments for TON. Therefore, establishing stable and reliable animal models and conducting intervention studies are of great significance for exploring the pathogenesis of optic nerve injury and developing potential therapeutic strategies.

Research Applications

Animal models of traumatic optic nerve injury are primarily used for:

  • Investigating pathological changes following optic nerve injury.
  • Analyzing the mechanisms of Retinal Ganglion Cell (RGC) degeneration.
  • Exploring mechanisms of axonal regeneration and neural repair.
  • Evaluating neuroprotective and regenerative therapeutic strategies.
  • Studying inflammatory responses and ischemic injury in the optic nerve.

Commonly used experimental animals include rats, rabbits, cats, and dogs, with rats being the most widely utilized. Rats possess a dark retinal pigment layer, making the retina easy to identify and less prone to damage during dissection, which facilitates retinal flat-mount observations. Consequently, they are the most preferred experimental animals.

Key Points of Experimental Design

I. Optic Nerve Transection Model

Modeling Method

  • Anesthetize the rat (commonly using chloral hydrate or pentobarbital).
  • Incise the bulbar conjunctiva under an operating microscope.
  • Dissect the lateral rectus muscle and retract the eyeball.
  • Expose the optic nerve and transect it at the retrobulbar level.

Characteristics Pros:

  • Easy to unify injury standards.
  • Simple model establishment.
  • Facilitates controlled comparative studies.

Cons:

  • Results in complete injury.
  • Not conducive to studying neural repair/regrowth.

II. Optic Nerve Crush (Clamp) Model

This model is widely used in experimental research and closely mimics clinical optic nerve contusion.

Modeling Method

  • Anesthetize and stabilize the animal.
  • Incise the bulbar conjunctiva and dissect the lateral rectus muscle.
  • Expose the optic nerve.
  • Clamp the optic nerve approximately 2 mm behind the globe.

Common Parameter Examples:

  • 60 g clamping force for 30 s.
  • 50 g clamping force for 10 s.

Common Instruments

  • Hemostatic forceps.
  • Vascular forceps.
  • Aneurysm clips.
  • Nerve injury clamps.
  • Jeweler’s forceps.

Characteristics Pros:

  • Simple operation.
  • No craniotomy required.
  • Maintains the integrity of the optic nerve sheath.
  • High animal survival rate.

Cons:

  • Lack of unified standards for clamping force and duration.
  • Degree of injury is highly dependent on the operator’s technique.

III. Optic Nerve Impact Model

This is an indirect injury model, which closely resembles clinical scenarios.

1. Closed Impact Model Indirect optic nerve injury is produced by an acceleration impact device striking the head of a fixed animal. Characteristics:

  • Aligns with clinical injury mechanisms.
  • Relatively low success rate.
  • Higher animal mortality.

2. Open Impact Model Modeling Steps

  • Anesthetize the rat.
  • Expose the supraorbital margin.
  • Remove a portion of the orbital wall bone plate.
  • Insert the impact tube into the orbit.
  • Utilize a hydraulic cranial brain injury (FPI) device to generate impact.

Model Characteristics Pros:

  • Controllable degree of injury.
  • Good reproducibility.
  • Similar to clinical indirect injury.

Cons:

  • Complex surgical procedure.
  • High equipment requirements.

IV. Optic Nerve Traction (Stretch) Model

Modeling Method

  • Incise the bulbar conjunctiva after anesthesia.
  • Dissect the retrobulbar tissue.
  • Pull the eyeball outward toward the anterior orbital bony margin.
  • Return to the normal position.

Traction directions can be categorized as:

  • Parallel to the optic canal.
  • Perpendicular to the optic canal.

Characteristics Pros:

  • Degree of injury can be accurately quantified.
  • Good clinical relevance.

Cons:

  • Complex operation.
  • Not conducive to large-scale experiments.

Key Detection Indicators

1. Histological Changes

  • Optic nerve edema.
  • Sparsity of nerve fibers.
  • Axonal degeneration.
  • Reduction of Retinal Ganglion Cells (RGCs).

Visual Function Testing 2. Flash Visual Evoked Potential (F-VEP) Post-injury manifestations include:

  • Prolonged latency.
  • Reduced amplitude.
  • Changes become more pronounced with increasing injury severity.

3. Observation of Neural Regeneration

  • Formation of nascent axons.
  • Changes in astrocytes.
  • Alterations in retinal structure.

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