Differentiation of human osteoblastic cells in culture: modulation of proteases by extracellular matrix and tumor necrosis factor-alpha.
We have followed the synthesis and secretion of urokinase-type plasminogen activator (u-PA) and its inhibitor, PAI-1, and matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMP-1) during differentiation of a human osteoblastic cell line, HOS TE85, and the effect of TNF-alpha on this process. Our results show that the ratio of u-PA/PAI-1 associated with the cell-matrix components increases during differentiation of these cells over a 14-day period. Although TNF-alpha suppresses the induced increase in steady-state mRNA levels of u-PA and PAI-1 during maturation of extracellular matrix (ECM), the u-PA/PAI-1 ratio is altered in such a way that PA activity associated with the ECM is higher than control cells. The expression of MMP-1 is low and remains essentially invariant over a culture period of 14 days. TNF-alpha enhances MMP-1 transcription nearly 12-fold initially, after which mRNA levels drop off but remain significantly higher than the controls. Activities and steady-state mRNA levels of MMP-2 and MMP-9 increase nearly 15-fold during maturation of the ECM, but the level of TIMP-1 mRNA is not appreciably altered. The presence of TNF-alpha suppresses maturation-induced transcription of MMP-2, enhances TIMP-1 transcription, but has little effect on MMP-9 mRNA levels. The data show that chronic exposure to TNF-alpha alters the balance between u-PA/PAI-1 and MMPs/TIMP-1, which favors higher activity of proteinases. Accordingly, the presence of TNF-alpha in chronic inflammatory episodes would be expected to alter bone remodeling by inhibiting maturation of ECM and formation of bone.
Panagakos
F S
FS
Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 07103, USA.
Kumar
S
S
D002454:Cell Differentiation; D017077:Culture Media, Conditioned; D004790:Enzyme Induction / Q000187:drug effects; D005109:Extracellular Matrix / Q000502:physiology*; D018093:Gelatinases / Q000096:biosynthesis; D006023:Glycoproteins / Q000096:biosynthesis*; D006801:Humans; D008666:Metalloendopeptidases / Q000096:biosynthesis*; D009363:Neoplasm Proteins / Q000096:biosynthesis; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D012516:Osteosarcoma / Q000473:pathology; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D019714:Tissue Inhibitor of Metalloproteinases; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis*
D017077:Culture Media, Conditioned; D006023:Glycoproteins; D009363:Neoplasm Proteins; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D019714:Tissue Inhibitor of Metalloproteinases; D014409:Tumor Necrosis Factor-alpha; D014568:Urokinase-Type Plasminogen Activator; D018093:Gelatinases; D008666:Metalloendopeptidases