Optimisation and validation of immunohistochemical axonal markers for morphological and functional characterisation of equine peripheral nerves.
Authors: Almuhanna Abdulaziz H, Cahalan Stephen D, Lane Annette, Goodwin David, Perkins Justin, Piercy Richard J
Journal: Equine veterinary journal
Summary
# Editorial Summary Peripheral nerve disorders in horses present significant diagnostic and therapeutic challenges, yet our ability to understand their underlying pathology has been constrained by the lack of robust methods for identifying specific axonal populations within affected nerves. Almuhanna and colleagues optimised and validated a panel of immunohistochemical markers using fluorescence confocal microscopy to functionally characterise different axon types (myelinated motor, myelinated sensory, unmyelinated sympathetic and unmyelinated peptidergic) across three functionally distinct equine peripheral nerves (recurrent laryngeal, phrenic and plantar digital) using both formalin-fixed paraffin-embedded and frozen tissue samples with varying antigen retrieval protocols. The team successfully demonstrated that specific antibody combinations enabled reliable identification of cholinergic motor fibres, adrenergic sympathetic axons and neuropeptide-containing sensory fibres in cadaver material, whilst notably failing to specifically label parasympathetic fibres in any preparation examined. These validated protocols now provide equine clinicians and researchers with standardised tools for morphologically characterising neuropathies at different disease stages, potentially enabling earlier identification of axonal degeneration patterns and more targeted therapeutic interventions in conditions ranging from laryngeal paralysis to digital neuropathies. Future application of these markers to diseased tissue samples should clarify which specific axonal populations are preferentially affected in common equine neuropathies, ultimately improving diagnostic accuracy and informing evidence-based management strategies.
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Practical Takeaways
- •This methodology provides veterinarians with standardised tools to characterise specific axonal involvement in equine neuropathies, improving diagnostic accuracy and understanding of disease mechanisms
- •The technique can help differentiate motor, sensory, and autonomic nerve damage patterns, which may inform prognosis and treatment decisions for conditions affecting the laryngeal, phrenic, and digital nerves
- •Future application of this validated antibody panel could enable earlier detection of pathological changes in peripheral nerve disorders before clinical signs become severe
Key Findings
- •Immunohistochemical antibody panels can successfully identify myelinated motor, myelinated sensory, unmyelinated sympathetic, and unmyelinated peptidergic axons in equine peripheral nerves using FFPE tissue with optimised antigen retrieval
- •Recurrent laryngeal and phrenic nerves contain myelinated cholinergic motor fibres and mixed sensory/sympathetic components, while plantar digital nerves lack myelinated motor fibres and are primarily sensory
- •Parasympathetic fibre labelling was unsuccessful across all nerves and tissue processing methods examined
- •Validated antibody markers enable morphological and functional characterisation of equine nerves to support future neuropathology research