Co-expression of 1α-hydroxylase and vitamin D receptor in human articular chondrocytes

BMC Musculoskeletal Disorders

Research Article

Inigo Zubiaurre-Martinez¹  Yngve Figenschau²  Ann Kristin Hansen³ 

[1] Bone and joint research group, Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway;Department of Laboratory Medicine, University Hospital of North Norway, Tromsø, Norway;Endocrinology Research Group, Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway;Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway;Department of Orthopaedic Surgery, University Hospital of North Norway, Tromsø, Norway;Bone and joint research group, Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway;

关键词: Vitamin D;    1α,25(OH)D;    25(OH)D;    VDR;    CYP27B1;    Chondrocyte;    Cartilage;    Osteoarthritis;    Pellet culture;    Static suspension culture;   

DOI  :  10.1186/s12891-017-1791-y

 received in 2017-04-09, accepted in 2017-10-30,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundThe aim was to investigate whether resident chondrocytes in human articular cartilage and in subculture express vitamin D receptor (VDR) and the enzyme that hydroxylates the prohormone 25(OH)D3 to the active hormone 1α,25(OH)2D3, namely 1α-hydroxylase (CYP27B1). Any putative effects of vitamin D on chondrocytes were also explored.MethodsCartilage from human osteoarthritic knee joints, cultured chondrocytes and cells grown in 3D spheroids were examined for the expression of VDR and 1α-hydroxylase by PCR, Western blots and immunolabelling. Receptor engagement was judged by visualizing nuclear translocation. The effects of 25(OH)D3 and 1α,25(OH)2D3 on chondrocyte functions were assessed in proliferation-, chondrogenesis- and cartilage signature-gene expression assays. The capability of chondrocytes to hydroxylate 25(OH)D3 was determined by measuring the concentration of metabolites. Finally, a putative regulation of receptor and enzyme expression by 1α,25(OH)2D3 or interleukin (IL)-1β, was investigated by Western blot.ResultsGene expression was positive for VDR in freshly isolated cells from native cartilage, cells subcultured in monolayers and in spheroids, whereas protein expression, otherwise judged low, was apparent in monolayers. Nuclear translocation of VDR occurred upon 1α,25(OH)2D3 treatment. Transcripts for 1α-hydroxylase were detected in freshly isolated cells, cultured cells and spheroids. Western blots and immunolabelling detected 1α-hydroxylase protein in all materials, while staining of tissue appeared confined to cells at the superficial layer. A dose-dependent 1α,25(OH)2D3 production was measured when the enzyme substrate was supplied to cell cultures. Western blots revealed that the VDR, but not 1α-hydroxylase, was induced by IL-1β treatment in adherent cells. Proliferation in monolayers was enhanced by both 25(OH)D3 and 1α,25(OH)2D3, and both compounds had negative effects on chondrogenesis and cartilage-matrix genes.ConclusionsVDR expression in resident cartilage chondrocytes, generally considered differentiated cells, is elusive. A similar pattern applies for redifferentiated chondrocytes in spheroid cultures, whereas dedifferentiated cells, established in monolayers, stably express VDR. Both 25(OH)D3 and 1α,25(OH)2D3 are able to potentiate cell proliferation but have a negative impact in proteoglycan synthesis. Chondrocytes express 1α-hydroxylase and may contribute to the production of 1α,25(OH)2D3 into the joint environment. Effects of vitamin D could be unfavourable in the context of cartilage matrix synthesis.

【 授权许可】

CC BY   
© The Author(s). 2017