OP0085 ALTERED EXPRESSION OF NEUROTROPHINS AND THEIR RECEPTORS IN THE SKIN OF PATIENT WITH COMPLEX REGIONAL PAIN SYNDROME (CRPS)
Authors: S. Stroeve, S. Dudli, I. Kolm, I. Heggli, N. Herger, S. Catanzaro, A. Schweizer, M. Calcagni, O. Distler, F. Brunner, A. Juengel
Journal: Annals of the Rheumatic Diseases (2021)

Background: Complex regional pain syndrome (CRPS) is a rare painful condition that usually appears after trauma or surgery of the extremities. Symptoms include pain, sensory, sudomotor and vasomotor disturbances, trophic changes and impaired motor function. The course varies from mild to chronic disease with a high impact on daily functioning and quality of life. In skin tissue, sustained inflammatory, fibrotic processes together with reduced epidermal nerve fibers are reported. Neurotrophins and their receptors are mediators in cell-to-cell communication and key mediators of pain signaling Objectives: The aim of this study was to identify differential expression of neurotrophins and their receptors in the skin and skin fibroblasts of patients with CRPS Methods: Healthy controls (HC) and patients with acute CRPS with symptoms for less than 6 months fulfilling the Budapest criteria were recruited. Pain scores were evaluated by numeric rating scale (0=no pain, 100=maximal) and body perception was assessed using the Bath Body Perception Disturbance Scale (BBPDS) (0=no perception disturbance, 57=maximal perception disturbance). Skin biopsies of the affected and/or non-affected side were taken. Immunohistochemistry on formalin-fixed, paraffin-embedded skin tissue slides was used to show NT3 expression in skin tissues. Blinded analysis was done by an experienced dermato-pathologist determined staining graduated by 0= none, 1= sparse, 2=moderate, 3= dense. Skin fibroblast were isolated from skin biopsies by outgrowth cultures (CRPS, affected side, n=6 and HC, n=5). Cells (passage 3-6) were starved and subsequently stimulated with TNFα (10 ng/ml) or TGFβ (10 ng/ml) for 24 h to mimic active disease and total RNA was isolated by miRNeasy kit. Gene expression of neurotrophins (NGF, BDNF, and NT3) and neurotrophin receptors (NGFR, TrkA, TrkB and TrkC) was measured by quantitative real time PCR and quantified using the ΔΔCq method with GAPDH as a reference gene. ELISA was used to analyze NT3 protein expression in cell culture supernatants. Results: In 5 of 9 patients with CRPS immunohistological staining of NT3 showed an higher expression (from low to moderate) in the affected side versus the non-affected side. In 4 of 9 patients the expression of NT3 was high in the non-affected side (moderate/dense) and stayed high in the affected side. Of interest, the patients with increasing expression of NT3 in the affected side showed increased pain scores (max pain 80+/-10.95, n=5 versus 48.16+/-18.16, n=4, p=0.059 and changed body perception 26.8+/-8.68 n=5 versus 6.5+/-3.91, n=4, p=0.016). Isolated skin fibroblasts from the affected side of patients with CRPS compared to healthy skin fibroblasts showed higher basal gene expression of NT3 (log 2 fold-change= 1.9 +/- 0.4 , p= 0.005 ) and NGFR (log 2 fold-change= 3.6 +/- 2.1, p=0.014 ). TNFα stimulated CRPS skin fibroblasts showed higher expression for NT3 (log 2 fold-change= 2.1 +/- 1.2, p=0.002) compared to HC. TGFb stimulated skin fibroblasts of patients with CRPS showed higher expression of NT3 (log 2 fold-change= 1.4+/-0.8 , p=0.019 ), NGFR (log 2 fold-change= 2.6 +/- 1.8, p=0.036 ) and TrkC (log 2 fold-change= 2.3 +/- 1.8, p=0.032 ) compared to HC. On protein level, NT3 showed a tendency of upregulation in unstimulated fibroblasts from CRPS patients comparing to HC (CRPS mean= 8.0 +/- 2.2 pg/ml, HC mean= 6.3 +/- 1.8 pg/ml, p=0.25 ). After TNFα stimulation, protein level of NT3 was significantly higher in CRPS skin fibroblasts (CRPS mean= 10.6 +/- 2.4 pg/ml, HC mean= 4.8 +/- 1.3 pg/ml, p=0.004 ). Conclusion: These data indicate a new role of skin fibroblasts in CRPS. Differential basal and stimulated expression of NT3, the receptor for NT3 (TrkC) and NGFR, the common receptor for all neurotrophins, indicates deregulated communication of fibroblasts with the sensory nerve fibers in CRPS. This might contribute to the dysregulated healing process and sustained pain. Disclosure of Interests: Sanne Stroeve: None declared, Stefan Dudli: None declared, Isabel Kolm: None declared, Irina Heggli: None declared, Nick Herger: None declared, Sabrina Catanzaro: None declared, Andreas Schweizer: None declared, Maurizio Calcagni Speakers bureau: Arthrex, Consultant of: Medartis, Arthrex, SilkBiomaterials, Grant/research support from: Medartis, Oliver Distler: None declared, Florian Brunner: None declared, Astrid Juengel: None declared