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Published on: March 24, 2017
Disturbed Spatial WNT Activation-A Potential Driver of the Reticularized Skin Phenotype in Systemic Sclerosis
Sara Chenguiti Fakhouri1, Honglin Zhu2, Yi-Nan Li3
1Department of Internal Medicine 3 - Rheumatology and Clinical Immunology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg and Uniklinikum Erlangen, Erlangen, Germany, and Deutsches Zentrum Immuntherapie (DZI), FAU Erlangen-Nürnberg and Uniklinikum Erlangen, Erlangen, Germany.
Objective:
Little is known on the mechanisms necessary to maintain the physiologic adult human skin integrity. This study aims to quantitatively describe anatomic changes in systemic sclerosis (SSc)-skin compared with controls and investigate the underlying mechanisms.
Methods:
Skin morphology was histologically assessed in 23 patients with SSc, 18 controls, and 15 patients with hypertrophic scars. Spatial WNT/β-catenin-activation was analyzed by RNAscope and immunofluorescence staining. Enrichment of reticular marker genes in predefined fibroblast subpopulations was done using Gene Ontology (GO) enrichment and gene set enrichment analysis.
Results:
SSc skin showed a decrease in number (P < 0.0001/P = 0.0004), area (P < 0.0001), and height (P < 0.0001) of papillae compared with controls and hypertrophic scars, respectively. The expression of papillary/reticular marker genes shifted toward a reticular expression profile in SSc. On the level of previously defined fibroblast populations, the increase of reticular marker genes was particularly pronounced in the PI16+ and SFRP4+ populations (P < 0.0001, respectively). Mechanistically, the expression of the WNT/β-catenin target AXIN2 and the number of fibroblasts with nuclear β-catenin-staining-pattern increased in the papillary compared with the reticular dermis in healthy skin. This polarization was lost in SSc with a two-fold increase in β-catenin-positive fibroblasts and AXIN2-expressing fibroblasts throughout the dermis (P = 0.0095). Enrichment of genes related to WNT/β-catenin-regulation was found in the PI16+ population that also relocates from the reticular to the papillary dermis in SSc.
Conclusion:
We demonstrate an association of the "reticularized" skin phenotype in SSc with a profound loss of physiologic spatial WNT/β-catenin-activation. Rescuing the spatial WNT/β-catenin-activation might help restore the physiologic skin organization in future therapeutic approaches of fibrosing disorders.
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