Modulation of limb bud chondrogenesis by retinoic acid and retinoic acid receptors.
An excess of retinoic acid (RA) in the mouse embryo in utero produces hypochondrogenesis and severe limb bone deformities. Since one of the RA receptors--RAR-beta 2, is specifically induced in the limb bud cells upon treatment of embryos with teratogenic doses of RA, we investigated if this receptor played a role in teratogenesis by regulating the process of chondrogenesis. In micromass cultures of mouse limb bud mesenchymal cells, we found that a downregulation of RAR-beta 2 as well as several other RAR isoforms by supplementation of the culture medium with specific oligodeoxynucleotides stimulated chondrogenesis: cartilage nodule number, sulfated proteoglycans, and synthesis of collagen type IIB were all enhanced in a dose-dependent manner. However, only the antisense RAR-beta 2 probe efficiently prevented the strong inhibitory effects of exogenous RA on chondrogenesis in these cells. The data suggest that the RAR-RA complexes play a role in position-dependent patterning of the limb skeleton in normal development and that, in particular, RAR-beta 2 serves to prevent the mesenchymal cells from expressing their chondrogenic bias. Our results further strengthen the argument that RA-dependent elevation in RAR-beta 2 levels plays a unique role in RA-induced teratogenesis.
Jiang
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H
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Soprano
D R
DR
Li
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Soprano
K J
KJ
Penner
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JD
Gyda
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Kochhar
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D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects / Q000196:embryology*; D002454:Cell Differentiation / Q000187:drug effects; D003094:Collagen / Q000096:biosynthesis; D017931:DNA Primers; D015536:Down-Regulation; D018878:Limb Buds / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D009924:Organ Culture Techniques; D016133:Polymerase Chain Reaction; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis*; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D013431:Sulfates / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis; D014212:Tretinoin / Q000494:pharmacology*; D014617:Vacuoles / Q000648:ultrastructure; D000097768:Retinoic Acid Receptor gamma
D003094:Collagen; D017931:DNA Primers; D016376:Oligonucleotides, Antisense; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D013431:Sulfates; D014157:Transcription Factors; D014212:Tretinoin; D000097768:Retinoic Acid Receptor gamma; C000607072:Rara protein, mouse; C082925:retinoic acid receptor beta