title: Effects of retinoic acid on the differentiation of chondrogenic progenitor cells, ATDC5.
abstract: Chondrocyte differentiation is a fundamental process during endochondral ossification. Retinoic acid (RA) has been shown to regulate this process, however, the mechanisms underlying RA regulation of chondrogenesis are not clearly understood. Chondroprogenitor cells, ATDC5 have been shown to be a useful in vitro model for examining the multiple step differentiation of chondrocytes. The present study investigated the mechanisms underlying RA regulation of chondrogenesis using ATDC5 cell culture. In this study, we show that RA suppresses the cell growth, cartilage nodule formation, accumulation of proteoglycan, alkaline phosphatase (ALPase) activity and mineralization and that RA dose dependently upregulates the levels of type X collagen and matrix metalloproteinase-13 (MMP-13) mRNA which are marker proteins of hypertrophic chondrocytes, in ATDC5 cells. The addition of protein synthesis inhibitor, cycloheximide (CHX), partially inhibits the induction of type X collagen and MMP-13 mRNA by RA. In this system, RA upregulates the mRNA level of Runx2/Cbfa1 (type II), a positive regulator for mineralization, and downregulates the mRNA of Indian hedgehog (Ihh), parathyroid hormone related protein (PTHrP), negative regulators for terminal differentiation. However, RA downregulates ALPase, bone gla protein (BGP) mRNAs and mineralization. These data indicate that RA stimulates cartilage differentiation, however, cell condensation and cartilage nodule formation may be candidates of primary importance in the terminal differentiation of chondrocytes.
authors.affiliation: Developmental Oral Health Science, Department of Orofacial Development and Function, Graduate School, Tokyo Medical and Dental University, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kirimoto
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Takagi
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ohya
authors.forename: Hitoyata
authors.initials: H
authors.lastname: Shimokawa
mesh_terms: D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors; D000818:Animals; D002356:Cartilage / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D019902:Chondrocytes / Q000187:drug effects*; D020219:Chondrogenesis / Q000187:drug effects*; D024121:Collagen Type X / Q000187:drug effects; D017364:Collagenases / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology*; D053823:Hedgehog Proteins; D053509:Matrix Metalloproteinase 13; D051379:Mice; D015675:Osteocalcin / Q000187:drug effects; D010012:Osteogenesis / Q000187:drug effects; D044162:Parathyroid Hormone-Related Protein / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013234:Stem Cells / Q000187:drug effects*; D015534:Trans-Activators / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D024121:Collagen Type X; D050659:Core Binding Factor Alpha 1 Subunit; D004791:Enzyme Inhibitors; D006133:Growth Substances; D053823:Hedgehog Proteins; D044162:Parathyroid Hormone-Related Protein; D011500:Protein Synthesis Inhibitors; C493716:Runx2 protein, mouse; D015534:Trans-Activators; D015675:Osteocalcin; D014212:Tretinoin; D003513:Cycloheximide; D000469:Alkaline Phosphatase; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse