Various computational algorithms predicted that miR-29 can target multiple genes including ECM components such as collagen, fibrillin, elastin and also TGF- regulated genes, including TGF- activated kinase 1/MAP3K7 binding protein 1 (TAB1)[17],[18]. and Western Blotting. The GNAQ functional effect of miR-29a on dermal fibroblasts was assessed in collagen gel assay. In addition, HeLa cells were transfected with 3UTR of TAB1 plasmid cloned downstream of firefly luciferase gene to assess TAB1 activity. HC fibroblasts and HeLa cells were also transfected with Target protectors in order to block the endogenous miR-29a activity. == Results == We found that TAB1 is a novel target gene of miR-29a, also regulating downstream TIMP-1 production. TAB1 is involved in TGF- signal transduction, a key cytokine triggering TIMP-1 production. To confirm that TAB1 is abona fidetarget gene of miR-29a, we used a TAB1 3UTR luciferase assay and Target protector system. We showed that miR-29a not only reduced TIMP-1 secretion via TAB1 repression, but also increased functional MMP-1 production resulting in collagen degradation. Blocking TAB1 activity by pharmacological inhibition or TAB1 knockdown resulted in TIMP-1 reduction, confirming TAB1-dependent TIMP-1 regulation. Enhanced expression of miR-29a was able to reverse the profibrotic phenotype of SSc fibroblasts via downregulation of collagen and TIMP-1. == Conclusions == miR-29a repressed TAB1-mediated TIMP-1 production in dermal fibroblasts, demonstrating that miR-29a may be a therapeutic target in SSc. == Introduction == Systemic sclerosis (SSc) is an autoimmune disease characterized by increased production of collagen and other profibrotic factors, including tissue inhibitors of metalloproteinases (TIMPs). TIMPs and matrix metalloproteinases (MMPs) are responsible for maintaining the balance between production and degradation of extracellular matrix proteins (ECM). Fibroblasts play an essential role during pathological remodelling of ECM by excessive deposition of collagen and TIMP-1[1]. A previous study showed that TIMP-1 is increased in SSc sera and is excessively produced by fibroblasts isolated from the involved skin lesions of SSc patients[2],[3]. We have also demonstrated that monocytes from SSc patients produce more TIMP-1 following TLRs stimulation, thereby contributing to fibrosis development[4],[5]. In animal models, the serum level of TIMP-1 correlates with dexamethasone-induced liver fibrosis in rats. Likewise, TIMP-1 strongly promotes liver fibrosis development in CCL4-treated TIMP-1 transgenic mice[6],[7]. Furthermore, adenoviral overexpression of human recombinant TIMP-1 in murine fibroblasts increased their proliferation and differentiation toward pathogenic myofibroblast phenotype, which demonstrates an additional role of TIMP-1 beyond the inhibition of MMPs activity[8]. Recently, it has been shown that the fibrotic remodelling process is associated with an altered pattern of miRNAs expression. Micro RNAs (miRs) are small, noncoding (consisting of 19 to 22 nucleotides) RNAs that mostly bind to 3UTRs of target mRNAs leading to gene silencing. Thus, miRs act as a fine-tuner of gene expression that negatively regulate between 25 and 60 percent of human protein-coding genes[9]. Furthermore, expression of miRs can be altered under conditions of Norepinephrine hydrochloride pathophysiological stress or disease, allowing miRs to be important biomarkers and attractive candidates for therapeutic manipulation[10],[11]. Recent studies have shown that miRs are involved in pathological fibrosis in many organs including lung, heart, kidney and skin[12][14]. In particular, it has been demonstrated that the family of miR-29 is a key regulator of skin fibrosis[15],[16]. The miR-29 family consists of three members (miR29-a, -b, -c) which bind to an identical seed sequence of transcript, therefore allowing the targeting of the same genes[12]. Various computational algorithms predicted that miR-29 can target multiple genes including ECM components such Norepinephrine hydrochloride as collagen, fibrillin, elastin and also TGF- Norepinephrine hydrochloride regulated genes, including TGF- activated kinase 1/MAP3K7 binding protein 1 (TAB1)[17],[18]. Several of these genes have been already validated inin vitroandin vivoapproaches[17]. In particular, type 1 collagen was shown to be a direct target gene of miR-29a[15],[19]. It was demonstrated that miR-29a downregulated collagen expression in dermal fibroblasts, which resulted in inhibition of ECM deposition. Furthermore, miR-29a was strongly reduced in SSc fibroblasts compared to healthy controls suggesting an important role of this microRNA as a biomarker of fibrogenesis[15]. TGF- is thought to play a pivotal role in SSc pathogenesis via induction of profibrotic molecules including.