title: Retinoic acid and the transcription factor MafB act together and differentially to regulate aggrecan and matrix metalloproteinase gene expression in neonatal chondrocytes.
abstract: Vitamin A (VA) and its active form, retinoic acid (RA), are regulators of skeletal development and chondrogenesis. MafB, a transcription factor, has been identified as an important mediator in monocyte and osteoclast differentiation. However, the presence and function of MafB in chondrocytes is not clear. In this study, MafB gene expression was regulated by both the VA status of the mother (VA-marginal, adequate, and supplemented diets) and by direct oral supplementation of the neonates with VARA (VA mixed with 10% RA). Expression was highest in neonates of VA-supplemented versus VA-marginal dams (P < 0.05), and in VARA-treated versus placebo-treated neonates across all diet groups (P < 0.05). To examine cellular changes, primary chondrocytes derived from neonatal rat ribs were cultured in the presence of RA for up to 48 h. MafB mRNA exhibited a time- and dose-dependent increase in response to RA, while the induction of MafB mRNA was attenuated by BMS-493, a pan-RAR inverse agonist, implicating RAR signaling in the regulation of MafB. The genetic knockdown of MafB in chondrocytes using siRNA (MafB(SI) chondrocytes) abrogated the RA-induced increase in MafB expression. MafB(SI) chondrocytes expressed higher levels of aggrecan mRNA. Additionally, the increased matrix metalloproteinase (MMP)3 and MMP13 gene expression due to RA was attenuated in MafB(SI) chondrocytes, while total extracellular matrix staining was increased. These results support a role for MafB as a regulator of chondrocyte gene expression and matrix formation via control of aggrecan, MMP3 and MMP13 expression, and indicate an important role for RA in the regulation of MafB.
authors.affiliation: Department of Nutritional Sciences, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhang
authors.forename: A Catharine
authors.initials: AC
authors.lastname: Ross
mesh_terms: D053674:Aggrecans / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D020219:Chondrogenesis / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006801:Humans; D051258:MafB Transcription Factor / Q000235:genetics / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism*; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism*; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D014212:Tretinoin / Q000008:administration & dosage / Q000378:metabolism
chemical_list: D053674:Aggrecans; D051258:MafB Transcription Factor; C490405:Mafb protein, rat; D015513:Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014212:Tretinoin; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3