Jiang H, Soprano D R, Li S W, Soprano K J, Penner J D, Gyda M, Kochhar D M
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Int J Dev Biol. 1995 Aug;39(4):617-27.
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.
子宫内的小鼠胚胎中视黄酸（RA）过量会导致软骨形成减少和严重的肢体骨骼畸形。由于在用致畸剂量的RA处理胚胎后，肢体芽细胞中会特异性诱导出一种RA受体——RAR-β2，我们研究了该受体是否通过调节软骨形成过程在致畸作用中发挥作用。在小鼠肢体芽间充质细胞的微团培养中，我们发现通过向培养基中添加特定的寡脱氧核苷酸来下调RAR-β2以及其他几种RAR异构体可刺激软骨形成：软骨结节数量、硫酸化蛋白聚糖和IIB型胶原的合成均呈剂量依赖性增加。然而，只有反义RAR-β2探针能有效阻止外源性RA对这些细胞软骨形成的强烈抑制作用。数据表明，RAR-RA复合物在正常发育中肢体骨骼的位置依赖性模式形成中发挥作用，特别是RAR-β2可防止间充质细胞表现出其软骨形成倾向。我们的结果进一步支持了这样的观点，即RA依赖性的RAR-β2水平升高在RA诱导的致畸作用中起独特作用。
