Tsk2/+ Mice Demonstrate Increased TWEAK/FN14 and TGF-β Pathways During Early Dermal Fibrosis

Background/Objectives: Our prior work demonstrated that a non-synonymous mutation in procollagen type III (Col3a1) at residue 33 (C33S) was responsible for the skin fibrosis seen in the Tsk2/+ mouse. We previously showed increased expression of the TWEAK receptor/fibroblast growth factor–inducible 14 (FN14) in Tsk2/+ skin and systemic sclerosis (SSc) skin; however, the role of TWEAK in Tsk2/+ had not been assessed. Methods: Primary dermal fibroblasts from Tsk2/+ and WT mice were examined for differential gene expression at different ages. Wild-type and C33S-mutated COL3A1-expressing plasmids were transfected into Col3a1KO fibroblasts and treated with FN14 or TGF-β inhibitors. Results: Tsk2/+ mice had increased FN14 protein compared to their respective non-diseased counterparts and had increased mRNA expression of a panel of transcripts associated with a fibrotic signature (Icam1, Irak2, and Tweak). COL3A1-KO cells transfected with a COL3A1Tsk2-expressing plasmid displayed significantly higher levels of this fibrotic signature compared to COL3A1WT-expressing plasmid. FN14 and TGFBR1 inhibitors significantly reduced the fibrotic signature compared to untreated Tsk2/+ cells. Conclusions: The upregulation of FN14 in Tsk2/+ mouse skin and primary dermal fibroblasts suggests that this pathway may be crucial to fibrosis development. Inhibition of both FN14 and TGFBRI reduces the fibrotic signature in both Col3a1Tsk2 transfections, suggesting a similarity between the Tsk2/+ model and SSc and confirming that the Tsk2/+ mouse model is suitable for studying the initiating events of SSc fibrosis.