Session Information
Title: Systemic Sclerosis, Fibrosing Syndromes and Raynaud's - Pathogenesis, Animal Models and Genetics II
Session Type: Abstract Submissions (ACR)
Background/Purpose
Transforming growth factor-beta stimulates collagen synthesis and myofibroblast differentiation, and is implicated as a key initiating factor in pathological tissue remodeling in scleroderma. However, the mechanism responsible for the persistence fibrotic response associated with scleroderma is not well understood. Recent studies provide evidence for activated innate immunity in patients with scleroderma. Many alternately spliced factors that govern normal embryonic and fetal development are currently recognized as being central to postnatal repair and injury responses. We hypothesized that tissue injury in scleroderma leads to generation and accumulation of alternately spliced extracellular matrix molecules such as tenascin C that are recognized by, and serve as endogenous ligands for TLR4 to drive persistent fibrosis.
Methods
Tissue expression of tenascin C was investigated in scleroderma skin biopsies by microarray, immunofluorescence and real-time qPCR. Tenascin C was assayed in 3-D human skin equivalents reconstituted with scleroderma fibroblasts and in scleroderma serum. Cellular responses elicited by tenascin C in human and mouse skin fibroblasts and in 3-D organotypic human skin equivalents were examined. The role of tenascin C in scleroderma skin and lung fibrosis was investigated using tenascin C-null mouse.
Results
Levels of an alternately spliced full-length tenascin C isoform (TN-FL) were markedly elevated in scleroderma serum and skin biopsies, as well as in fibrotic skin and lung tissues from mice. TN-FL mRNA level correlated with the skin score. The splicing factor serine/arginine-rich (SR)-rich splicing factor SRSF6, implicated in alternate splicing of tenascin C, was elevated in scleroderma skin biopsies as well as in scleroderma fibroblasts populating skin equivalents. Treatment with TGF-ß stimulated the expression of both SRSF6 and TN-FL. In vitro, TN-FL stimulated collagen synthesis and myofibroblasts differentiation, and induced dermal sclerosis in skin equivalents. All of these profibrotic responses were abolished by genetic or pharmacological disruption of TLR4 signaling. Importantly, tenascin C-null mice treated with bleomycin were protected from development of skin and lung fibrosis and loss of lung compliance.
Conclusion
Increased SRSF6-driven alternate splicing of tenascin C leads to aberrant TN-FL accumulation in scleroderma. TN-FL triggers TLR4-dependent fibroblasts activation, contributing to intractable skin and lung fibrogenesis. Disrupting the tenascin C-TLR4 signaling axis by preventing tenascin C accumulation through SRSF6 blockade, or by blocking TLR4 signaling using selective small molecule inhibitors, represent appealing novel strategies for attenuating progressive fibrosis as treatment for scleroderma.
Disclosure:
S. Bhattacharyya,
None;
W. Wang,
None;
L. Morales-Nebreda,
None;
K. Lakota,
None;
R. Lafyatis,
None;
M. E. Hinchcliff,
None;
G. S. Budinger,
None;
Z. Tamaki,
None;
J. Varga,
None.
ACR Meeting Abstracts - https://acrabstracts.org/abstract/essential-role-for-alternately-spliced-tenascin-c-and-tlr4-signaling-in-persistent-organ-fibrosis/