ATRA Signaling Regulates the Expression of COL9A1 through BMP2‐WNT4‐RUNX1 Pathway in Antler Chondrocytes

Abstract

Although all-trans retinoic acid (ATRA) is involved in the regulation of cartilage growth and development, its regulatory mechanisms remain unknown. Here, we showed that ATRA could induce the expression of COL9A1 in antler chondrocytes. Silencing of cellular retinoic acid binding protein 2 (CRABP2) could impede the ATRA-induced upregulation of COL9A1, whereas overexpression of CRABP2 presented the opposite effect. RARα agonist Am80 induced the expression of COL9A1, whereas treatment with RARα antagonist Ro 41-5253 or RXRα small-interfering RNA (siRNA) caused an obvious blockage of ATRA on COL9A1. In antler chondrocytes, CYP26A1 and CYP26B1 weakened the sensitivity of ATRA to COL9A1. Simultaneously, Bone morphogenetic protein 2 (BMP2) and WNT4 mediated the regulation of ATRA on COL9A1 expression. Knockdown of WNT4 could abrogate the inhibitory effect of BMP2 overexpression on COL9A1. Conversely, constitutive expression of WNT4 reversed the upregulation of COL9A1 elicited by BMP2 siRNA. Together these data indicated that WNT4 might act downstream of BMP2 to mediate the effect of ATRA on COL9A1 expression. Further analysis evidenced that attenuation of runt-related transcription factor 1 (RUNX1) could prevent the stimulation of ATRA on COL9A1 expression, while exogenous rRUNX1 further enhanced this effectiveness. Moreover, RUNX1 might serve as an intermediate to mediate the regulation of BMP2 and WNT4 on COL9A1 expression. Collectively, ATRA signaling might regulate the expression of COL9A1 through BMP2-WNT4-RUNX1 pathway.

Lens-regulated retinoic acid signalling controls expansion of the developing eye

“…In chick prehypertrophic chondrocytes, retinoic acid binds to RAREs in the promotor region of the collagen X gene to directly activate transcription (Cohen et al, 2006). In contrast, retinoic acid-induced stimulation of COL9A1 expression in deer antler chondrocytes occurs indirectly through activation of a BMP2-WNT4-RUNX1 pathway (Zhang et al, 2017). Consistent with an indirect mode of action, expression of BMP7 and WNT2B also is downregulated in the peripheral retina of lens-removed eyes (Fig.…”

The roles of Runx1 in skeletal development and osteoarthritis: A concise review

“…However, the molecular mechanisms of Runx1 are not yet fully understood. Research has shown that all-trans retinoic acid (ATRA) can regulate cartilage development by the BMP2-WNT4-Runx1 pathway [ 107 , 108 ], but whether this pathway contributes to the recovery of OA remains unknown. Additionally, previous studies have shown that PTH, which acts as a promoter of chondrogenic differentiation [ 116 ], can regulate many signaling molecules, such as protein kinase C (PKC), mitogen-activated protein kinases (MAPK), and Wnt signaling.…”

“…Protein phosphatase 5 (PP5) can downregulate Runx1 and Runx2 by phosphorylating peroxisome proliferator-activated receptor γ (PPARγ) Ser-112 and reducing the transcriptional activity of PPARγ, thus decreasing the expression of ACAN, Col2a1, Col10a1, OPN, and OCN [ 106 ]. Furthermore, it was found that all-trans retinoic acid (ATRA), which is vital for chondrocyte proliferation and differentiation, can regulate cartilage development by the BMP2-WNT4-Runx1 pathway [ 107 , 108 ]. Moreover, in chondrocytes of antler cartilage, insulin-like growth factor 1 (IGF1) was discovered to promote the proliferation activity of chondrocytes through insulin receptor substrate 1 (IRS1) and IRS2, whose downstream targets were Runx1 [ 109 ] ( Figure 4 b).…”

Retinoic acid increases the effect of bone morphogenetic protein type 2 on osteogenic differentiation of human adipose-derived stem cells

“…Conversely, Sheng, et al 35 (2010) proposed that RA enhances the interaction between phosphorylated Smad1 and its ubiquitin E3 ligases, resulting in phosphorylated Smad1 ubiquitination and proteasomal degradation, suggesting a mechanism through which RA suppresses BMP/Smad signaling. Zhang, et al 36 (2017) demonstrated that RA signaling regulates COL9A1 expression through the BMP2-WNT4-RUNX1 pathway. These different results may be occur because the BMP signaling pathway is cell type-specific and cell context-dependent, given that Yang, et al 33 (2012) studied 143B osteosarcoma cells, Adams, et al 34 (2003) evaluated chondrocytes from embryonic chick sterna, Liu, et al 11 (2014) employed 3-T3-L1 preadipocytes, Sheng, et al 35 (2010) evaluated P19C6 cells, a subclone of mouse embryonic carcinoma, and Zhang, et al 36 (2017) studied antler chondrocytes.…”