title: Rat growth plate chondrocytes express low levels of 25-hydroxy-1alpha-hydroxylase.
abstract: Long standing disturbances of Vitamin D-metabolism as well as null-mutant animals for 25-hydroxy-1alpha-hydroxylase results in disorganised growth plates. Cultured chondrocytes were shown to be target for the hydroxylated Vitamin D-metabolites 1alpha,25(OH)(2)D(3) and 24,25(OH)(2)D(3). Because studies on production of these metabolites were inconclusive in in vitro systems, the expression of the Vitamin D-system was examined in rat growth plate chondrocytes in vitro as well as ex vivo. Gene expression for 25-hydroxy-1alpha-hydroxylase, 25-hydroxy-24-hydroxylase as well as Vitamin D-receptor and collagen II and X were analysed on mRNA level by RT-PCR and quantitative real-time PCR, on protein level by western blotting and by immunohistochemistry in isolated growth plate chondrocytes or intact growth plates. Compared to UMR or CaCo(2) cells and renal homogenates cultured growth plate chondrocytes expressed low levels of 25-hydroxy-1alpha-hydroxylase mRNA and 25-hydroxy-24-hydroxylase mRNA. The expression of both was modulated by 25(OH)D(3), but 1alpha,25(OH)(2)D(3) affected only 25-hydroxy-24-hydroxylase. These data were confirmed by Western blotting. Immunohistochemistry demonstrated predominant staining for 25-hydroxy-1alpha-hydroxylase in chondrocyte nodules and cells embedded in matrix in vitro. Ex vivo, 25-hydroxy-1alpha-hydroxylase was detected predominantly in late proliferative and hypertrophic zone of the growth plate. In conclusion, growth plate chondrocytes express the key components for a paracrine/autocrine Vitamin D-system.
authors.affiliation: Division of Pediatric Nephrology, Department of Pediatrics, University of Heidelberg, Im Neuenheimer Feld 150, 69120 Heidelberg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hügel
authors.forename: Lutz
authors.initials: L
authors.lastname: Weber
authors.forename: Jörg
authors.initials: J
authors.lastname: Reichrath
authors.forename: Otto
authors.initials: O
authors.lastname: Mehls
authors.forename: Günter
authors.initials: G
authors.lastname: Klaus
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019902:Chondrocytes / Q000201:enzymology*; D006132:Growth Plate / Q000201:enzymology*; D007150:Immunohistochemistry; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013250:Steroid Hydroxylases / Q000378:metabolism*
chemical_list: D013250:Steroid Hydroxylases