Background/Purpose: Systemic sclerosis (SSc) is characterized by the excessive deposition of collagen and other connective tissue components in skin and multiple internal organs.  Although transforming growth factor β (TGF-β) has been shown to play a crucial role in the development of tissue fibrosis in SSc, recently, other factors such as excessive oxidative stress have been implicated in the pathogenesis of the disease. Oxidative stress is caused by cellular overproduction of ROS (reactive oxidative species). NOX4 is one of seven NADPH isoforms which plays a crucial role in the generation of ROS. Numerous recent studies have described an important role of microRNAs (miRNA) in the pathogenesis of the fibrotic process in various fibrotic diseases including renal, pulmonary, and liver fibrosis as well as in SSc. The purpose of these studies was to induce overexpression of NOX4 in normal human dermal fibroblasts and to examine the effect of increased NOX4 levels on the expression of various miRNA that participate in the regulation of tissue fibrosis.

Methods: Two different cell lines of normal human dermal fibroblasts were isolated from skin biopsies, and were expanded in monolayer cultures to approximately 70% of confluence and then they were transiently transfected with either a NOX4 protein expression construct (pCI-NOX4) to induce in NOX4 expression or with the vector control pCI. The effects of NOX4 overexpression on global gene expression levels and on the expression of relevant miRNA were examined employing microarrays using Human gene 1.0 ST array Affymetrix gene chips.

 

Results: Induced NOX4 expression did not cause apparent morphological changes or cytotoxicity. Remarkable changes in the expression levels of numerous transcripts associated with the phenotypic activation of fibroblasts into myofibroblasts were observed. Also, NOX4 overexpression caused significant changes in the levels of several relevant miRNAs. It was of substantial interest that the predicted gene targets for these miRNA included highly relevant genes such as those encoding members of the TGF-β pathway, as well as genes encoding numerous ECM proteins, and several crucial regulatory/transcription factor genes including Fli1, Gli3, and Hif1A.

Conclusion: Induced NOX4 expression resulted in remarkable changes in the levels of expression of numerous transcripts associated with the phenotypic activation of myofibroblasts as well as changes in the levels of several miRNAs that exert important regulatory effects on various genes that participate in the fibrotic process. These observations provide strong support to the notion that targeting NOX4 expression may be a novel therapeutic approach for SSc and other systemic fibrotic disorders.

---

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/effect-of-nox4-overexpression-on-the-levels-of-micro-rnas-relevant-to-systemic-sclerosis-fibrotic-process/