Pro-Fibrotic Phenotype in a Patient with Segmental Stiff Skin Syndrome via TGF-β Signaling Overactivation

Abstract

Transforming growth factor β (TGF-β) superfamily signaling pathways are ubiquitous and essential for several cellular and physiological processes. The overexpression of TGF-β results in excessive fibrosis in multiple human disorders. Among them, stiff skin syndrome (SSS) is an ultrarare and untreatable condition characterized by the progressive thickening and hardening of the dermis, and acquired joint limitations. SSS is distinct in a widespread form, caused by recurrent germline variants of FBN1 encoding a key molecule of the TGF-β signaling, and a segmental form with unknown molecular basis. Here, we report a 12-year-old female with segmental SSS, affecting the right upper limb with acquired thickening of the dermis evident at the magnetic resonance imaging, and progressive limitation of the elbow and shoulder. To better explore the molecular and cellular mechanisms that drive segmental SSS, several functional studies on patient’s fibroblasts were employed. We hypothesized an impairment of TGF-β signaling and, consequently, a dysregulation of the associated downstream signaling. Lesional fibroblast studies showed a higher phosphorylation level of extracellular signal-regulated kinase 1/2 (ERK1/2), increased levels of nuclear factor-kB (NFkB), and a nuclear accumulation of phosphorylated Smad2 via Western blot and microscopy analyses. Quantitative PCR expression analysis of genes encoding key extracellular matrix proteins revealed increased levels of COL1A1, COL3A1, AGT, LTBP and ITGB1, while zymography assay reported a reduced metalloproteinase 2 enzymatic activity. In vitro exposure of patient’s fibroblasts to losartan led to the partial restoration of normal transforming growth factor β (TGF-β) marker protein levels. Taken together, these data demonstrate that in our patient, segmental SSS is characterized by the overactivation of multiple TGF-β signaling pathways, which likely results in altered extracellular matrix composition and fibroblast homeostasis. Our results for the first time reported that aberrant TGF-β signaling may drive the pathogenesis of segmental SSS and might open the way to novel therapeutic approaches.

Classification and rising medication therapy in stiff skin syndrome: A case report and literature review

“…In our case, pathogenic mutations of FBN1 were undetected from peripheral blood. However, interestingly, even in patients of classic SSS without FBN1 germline or chimeric mutations, aberrant expression of FBN1 gene, increased expression levels of FBN1 transcript, and hyperactivation of the TGF‐β signaling pathway, were still observed, which results in abnormal extracellular matrix composition and excessive fibrosis 26 . In a word, abnormalities of TGF‐β signaling pathway and fibrosis constitute the common features of mechanisms in classic SSS, which opened a way to the potential drugs regulating the TGF‐β signaling pathway and reducing fibrosis.…”

Segmental stiff skin syndrome (SSS): Clinical case and a brief review

“…1,9 One known cause of widespread SSS is a mutation in the gene that encodes fibrillin-1 (FBN1), a change that alters transforming growth factor signalling and leads to fibrosis. 10,11 However, reported cases of segmental SSS failed to identify this mutation in the peripheral blood DNA. 6,12 It is possible that segmental SSS, and even some cases of diffuse SSS, may be caused by mosaic activation of fibrosing genes.…”

Transcriptome Analysis Reveals Altered Expression of Genes Involved in Hypoxia, Inflammation and Immune Regulation in Pdcd10-Depleted Mouse Endothelial Cells

“…After 48 h, cells were lysed in 1x D-PBS, 0.025% NP-40 and protease- and phospho-inhibitors (Roche, Pasadena, CA, USA). Total cell lysates were analyzed by 10% SDS-PAGE page electrophoresis, transferred to nitrocellulose membrane and blotted with anti-Pdcd10 (Proteintech Cat#10294-2-AP, RRID: AB_2162153) and anti-β-Actin (Santa Cruz Biotechnology Cat#sc-47778 HRP, RRID:AB_2714189) [ 14 , 15 , 16 ] antibodies. The specificity of the anti-Pdcd10 antibody was determined through Pdcd10 silencing by comparing the control and silenced cell line.…”