Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is closely associated with the chondrocyte nucleus in human articular cartilage

Hunziker, E B; Kapfinger, E; Martin, J; Buckwalter, J; Morales, T I (2008). Insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is closely associated with the chondrocyte nucleus in human articular cartilage. Osteoarthritis and cartilage, 16(2), pp. 185-94. Amsterdam: Elsevier 10.1016/j.joca.2007.06.008

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OBJECTIVE: Insulin-like growth factor-I (IGF-I) is critically involved in the control of cartilage matrix metabolism. It is well known that IGF-binding protein-3 (IGFBP-3) is increased during osteoarthritis (OA), but its function(s) is not known. In other cells, IGFBP-3 can regulate IGF-I action in the extracellular environment and can also act independently inside the cell; this includes transcriptional gene control in the nucleus. These studies were undertaken to localize IGFBP-3 in human articular cartilage, particularly within cells. DESIGN: Cartilage was dissected from human femoral heads derived from arthroplasty for OA, and OA grade assessed by histology. Tissue slices were further characterized by extraction and assay of IGFBPs by IGF ligand blot (LB) and by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry (IHC) for IGF-I and IGFBP-3 was performed on cartilage from donors with mild, moderate and severe OA. Indirect fluorescence and immunogold-labeling IHC studies were included. RESULTS: LBs of chondrocyte lysates showed a strong signal for IGFBP-3. IHC of femoral cartilage sections at all OA stages showed IGF-I and IGFBP-3 matrix stain particularly in the top zones, and closely associated with most cells. A prominent perinuclear/nuclear IGFBP-3 signal was seen. Controls using non-immune sera or antigen-blocked antibody showed negative or strongly reduced stain. In frozen sections of human ankle cartilage, immunofluorescent IGFBP-3 stain co-localized with the nuclear 4',6-diamidino-2-phenyl indole (DAPI) stain in greater than 90% of the cells. Immunogold IHC of thin sections and transmission electron immunogold microscopy of ultra-thin sections showed distinct intra-nuclear staining. CONCLUSIONS: IGFBP-3 in human cartilage is located in the matrix and within chondrocytes in the cytoplasm and nuclei. This new finding indicates that the range of IGFBP-3 actions in articular cartilage is likely to include IGF-independent roles and opens the door to studies of its nuclear actions, including the possible regulation of hormone receptors or transcriptional complexes to control gene action.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Pre-clinic Human Medicine > BioMedical Research (DBMR) > DBMR Forschung Mu35 > Center of Regenerative Medicine for Skeletal Tissues [discontinued] 04 Faculty of Medicine > Pre-clinic Human Medicine > BioMedical Research (DBMR) > DBMR Forschung Mu35 > Center of Regenerative Medicine for Skeletal Tissues [discontinued]
UniBE Contributor:	Hunziker, Ernst Bruno
ISSN:	1063-4584
ISBN:	17693100
Publisher:	Elsevier
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 15:06
Last Modified:	05 Dec 2022 14:20
Publisher DOI:	10.1016/j.joca.2007.06.008
PubMed ID:	17693100
Web of Science ID:	000253638500004
URI:	https://boris.unibe.ch/id/eprint/28538 (FactScience: 121234)