Spatial transcriptomic alterations of the dorsal horn in dogs with neuropathic pain

This study investigated how astrocytes and microglia in the dorsal horn of Cavalier King Charles Spaniels (CKCS) with syringomyelia (SM) differ at the molecular level when dogs exhibit neuropathic pain (NeP) versus when they do not. As the authors state, this work provides a basis for further understanding of the changes seen in pain processes in SM.

Using NanoString GeoMx spatial transcriptomics, the authors analyzed gene expression in specific glial-rich regions to understand the mechanisms driving chronic pain.

Link to open access paper by Remler Pedersen et al

The key findings of this work are fascinating and reveal some detail about the role of microglia and astrocytes in chronic pain – specifically in dogs.

Microglia show the strongest transcriptional changes. Dogs with SM and neuropathic pain had:

• Upregulation of inflammatory and cytokine-related genes

• Upregulation of signaling pathways known to promote microglial activation and neuroinflammation.

• Downregulation of immune-regulatory genes suggesting a dysregulated or exhausted microglial immune phenotype.

Microglia in painful SM dogs are shifted toward a dysfunctional inflammatory state—reduced immune homeostasis alongside increased cytokine signaling—which may drive neuropathic pain.

Astrocytes show mixed reactive profiles. Astrocyte-rich areas showed:

• Some upregulated reactive genes showing markers of astrocyte reactivity, inflammation, and itch circuitry

• But many reactive/structural genes were downregulated

  
  

  indicating altered or heterogeneous reactivity states

Pathway analyses suggested:

• Compared with healthy controls, astrocytes in painful SM dogs showed:

  • Upregulation of apoptosis and complement pathways

  • Downregulation of metabolic/homeostatic pathways

Astrocytes do remodel in SM with pain, but changes are less dramatic than microglia and heterogeneous—suggesting multiple astrocyte states rather than a uniform “reactive astrocyte” signature.

There were minimal differences between painful SM dogs and healthy controls in microglia

Only two microglial-associated genes were different:

• UBB (housekeeping gene) ↓

• GLUL (glutamate–glutamine pathway) ↓

This suggests:

• The major microglial dysfunction is specific to the presence of SM, not only to pain.

A specific signalling pathways called the PI3K-AKT signaling emerges as a central candidate pathway. Across analyses, the authors highlight:

• PI3K‑AKT pathway upregulation in microglia

  → previously implicated in chronic pain, neuroinflammation, microglial activation, and neurodegeneration

  → may be a driver of the neuropathic pain phenotype in CKCS with SM.

In conclusion

• Neuropathic pain in dogs with syringomyelia is associated with substantial microglial transcriptional dysregulation and more modest, state-dependent astrocytic alterations.

• Upregulation of PI3K-AKT and cytokine/signal transduction pathways suggests maladaptive microglial activation.

• Downregulation of immune homeostasis pathways may indicate impaired or exhausted microglial regulation.

• The findings align with known mechanisms in rodent chronic pain models, supporting CKCS with SM as a valuable spontaneous model for neuropathic pain research.

So how did they perform this research I hear you say?! For the technical details, you can find those in the manuscript.

Thirteen euthanized Cavalier King Charles Spaniels (CKCSs) were included. Dogs were divided into:

• Group I: Syringomyelia (SM) with neuropathic pain (n=8)

• Group II: SM without pain (n=2)

• Group III: Controls without SM or pain (n=3)

All dogs received physical and neurological exams, MRI, and postmortem histopathology. Owners completed structured questionnaires to identify clinical signs of neuropathic pain. Some dogs had been treated with analgesics.

Spinal cord segments C1–C8 were removed within 90 minutes of euthanasia. Tissue was formalin‑fixed, paraffin-embedded (FFPE), and sectioned into 5 μm transverse sections for further processing. Tissue samples underwent a variety of analyses including NanoString GeoMx Digital Spatial Profiling (detail in paper).

It's great to see that the field of SM research is advancing and we congratulate the authors on this interesting research!