Canonical and noncanonical TGF-β signaling regulate fibrous tissue differentiation in the axial skeleton

Abstract

Previously, we showed that embryonic deletion of TGF-β type 2 receptor in mouse sclerotome resulted in defects in fibrous connective tissues in the spine. Here we investigated how TGF-β regulates expression of fibrous markers: Scleraxis, Fibromodulin and Adamtsl2. We showed that TGF-β stimulated expression of Scleraxis mRNA by 2 h and Fibromodulin and Adamtsl2 mRNAs by 8 h of treatment. Regulation of Scleraxis by TGF-β did not require new protein synthesis; however, protein synthesis was required for expression of Fibromodulin and Adamtsl2 indicating the necessity of an intermediate. We subsequently showed Scleraxis was a potential intermediate for TGF-β-regulated expression of Fibromodulin and Adamtsl2. The canonical effector Smad3 was not necessary for TGF-β-mediated regulation of Scleraxis. Smad3 was necessary for regulation of Fibromodulin and Adamtsl2, but not sufficient to super-induce expression with TGF-β treatment. Next, the role of several noncanonical TGF-β pathways were tested. We found that ERK1/2 was activated by TGF-β and required to regulate expression of Scleraxis, Fibromodulin, and Adamtsl2. Based on these results, we propose a model in which TGF-β regulates Scleraxis via ERK1/2 and then Scleraxis and Smad3 cooperate to regulate Fibromodulin and Adamtsl2. These results define a novel signaling mechanism for TGFβ-mediated fibrous differentiation in sclerotome.

The extracellular matrix glycoprotein ADAMTSL2 is increased in heart failure and inhibits TGFβ signalling in cardiac fibroblasts

“…Treatment with active, recombinant TGFβ increased endogenous ADAMTSL2 expression in CFBs, indicating that ADAMTSL2 is part of a negative feedback loop, in which TGFβ increases its own inhibitor. Indeed, ADAMTSL2 expression was recently shown to be controlled by TGFβ during fibrous tissue differentiation in the sclerotome 41 , supporting this theory. However, the molecular mechanisms underlying the reduction in TGFβ production and activity by ADAMTSL2 remain to be elucidated.…”

HBV induces liver fibrosis via the TGF‑β1/miR‑21‑5p pathway

“…As expected, TGF-β1 has a strong association with HBV replication and HBV related liver diseases (10,11). TGF-β1 has been demonstrated to serve important roles in HBV induces liver fibrosis via the TGF-β1/miR-21-5p pathway WENTING LI 1,2* , XIAOLAN YU 2,3* , XILIU CHEN 4* , ZHENG WANG 5 , MING YIN 2,6 , ZONGHAO ZHAO 1,2 and CHUANWU ZHU 7 hepatic stellate cell (HSC) activation, which is a key event in liver fibrosis (11,12). Accumulating evidence suggested that HBV infection may promote TGF-β1 production by hepatocytes, which in turn activates HSCs and accelerates liver fibrosis (13)(14)(15).…”

“…Over the past decades, accumulative studies have focused on the cascades of the TGF-β1 pathway, which takes part in multiple biological progresses, including cell activation (6), tissue differentiation (7), fibrosis (8) and cancer progression (9). As expected, TGF-β1 has a strong association with HBV replication and HBV related liver diseases (10,11).…”

TGFβ signaling is required for sclerotome resegmentation during development of the spinal column in Gallus gallus

“…TGFβ signals as a dimer that binds to a heterotetrametric receptor complex on the cell membrane that consists of two TGFβ type 1 receptors, TGFβR1, and two TGFβ type two receptors, TGFβR2. Activation of the receptor complex stimulates the phosphorylation of the well characterized downstream effectors Smad 2/3, or various “non-canonical” downstream effectors including ERK 1/2, AKT, and p38 (Hata and Chen, 2016, Chen et al, 2019, Zhang, 2009, Clayton et al, 2020). TGFβ regulates the expression of markers for fibrous tissues, including AF, ligament, and tendon, in cultured sclerotome through Smad-dependent and non-canonical signaling pathways (Clayton et al, 2020, Sohn et al, 2010, Ban et al, 2019, Cox et al, 2014).…”

“…Activation of the receptor complex stimulates the phosphorylation of the well characterized downstream effectors Smad 2/3, or various “non-canonical” downstream effectors including ERK 1/2, AKT, and p38 (Hata and Chen, 2016, Chen et al, 2019, Zhang, 2009, Clayton et al, 2020). TGFβ regulates the expression of markers for fibrous tissues, including AF, ligament, and tendon, in cultured sclerotome through Smad-dependent and non-canonical signaling pathways (Clayton et al, 2020, Sohn et al, 2010, Ban et al, 2019, Cox et al, 2014). Deletion of Tgfbr2 in mouse sclerotome in vivo (Col2aCre; Tgfbr2 LoxP/LoxP ) results in failure of the AF and other fibrous tissues to form correctly (Baffi et al, 2004, Pryce et al, 2009).…”