Spatial imaging analysis of cutaneous nerve-myeloid cell interactions in chronic complex regional pain syndrome

Complex regional pain syndrome (CRPS) involves disproportionate chronic pain alongside sensory, autonomic, motor, and trophic disturbances. The pathophysiology of CRPS remains unclear, but evidence indicates that cutaneous neuroimmune dysregulation contributes to symptom onset and maintenance. We conducted a high-parameter imaging mass cytometry and targeted immunofluorescence study of skin biopsies from 18 CRPS patients and 18 healthy controls using a panel of heavy metal isotope-conjugated antibodies to assess nerve fibre, immune cell, and vascular markers in situ. Quantitative data analysis revealed a reduction in proliferating keratinocytes, increased human leukocyte antigen-DR + (HLA-DR + ) Langerhans cell (LC) abundance, and increased HLA-DR + LC physiological interactions with intraepidermal nerve fibres in patients with CRPS. Langerhans cells also showed sexual dimorphism, being higher in CRPS-affected skin in women compared with men. HLA-DR + CD206 - dermal dendritic cells (DC) and CD68 + CXCR3 + pro-inflammatory macrophages were increased in CRPS-affected skin. Nerve fibre and blood vessel densities were unchanged. However, intraepidermal nerve fibre density decreased in proportion to temperature asymmetry between disease-affected and contralateral unaffected limbs, being lowest in patients with a cool CRPS-affected limb. These findings highlight significant decreases in epidermal keratinocyte proliferation, increases in LC abundance and nerve fibre interactions, especially the HLA-DR + subset, and increases in dermal DC cells in CRPS-affected skin, supporting a role for neuroimmune dysfunction and autoimmunity in CRPS pathophysiology.