Long Noncoding RNA H19 Mediates STAT3-Dependent Activation of Keratinocytes and Fibroblasts in Systemic Sclerosis...

Dermal systemic sclerosis (SSc) fibroblasts and their exosomes can activate keratinocytes in SSc, with long noncoding RNA (lncRNA) H19 highlighted as the most up-regulated RNA in their cargo compared with healthy controls (HCs). The role of H19 in SSc pathogenesis has never been investigated. Here we determine H19's role in the profibrotic activation of dermal fibroblasts and in their crosstalk with keratinocytes.

Skin biopsies were obtained from the forearms of patients with diffuse SSc (n = 20) or HCs (n = 8), and dermal fibroblasts were explanted. In situ hybridization was used to determine H19 expression in the skin, paired with immunohistochemistry of STAT3 and Collagen1. H19 and STAT3 expression were modulated by retroviral transduction and small interfering RNA. Gel contraction and Transwell coculture were employed for functional studies.

In SSc, high H19 expression in skin and explanted dermal fibroblasts compared with HCs showed moderate correlation to well-described profibrotic markers. Knockdown of H19 in SSc fibroblasts decreased profibrotic gene expression and cell contraction ability. H19 overexpression was sufficient to induce a profibrotic phenotype in HC fibroblasts. Mechanistically, transforming growth factor-β, interleukin-6, and interleukin-11 significantly increased H19 expression in HC fibroblasts (2.2-, 1.4-, and 3.5-fold, respectively) through activation of STAT3. Additionally, the STAT3 and STAT1 activation of keratinocytes induced by coculture with SSc fibroblasts was suppressed by H19 knockdown.

This study shows that lncRNA H19 is a key mediator of STAT3-induced changes in fibrotic activation of fibroblast and keratinocytes in SSc skin and could be considered a promising therapeutic target in tissue fibrosis.