Albumin regulates Runx2 and alpha1 (I) collagen mRNA expression in osteoblastic cells: comparison with insulin-like growth factor-I.
Albumin has been shown to be expressed in osteoblastic cells. The role of albumin in osteoblastic cells was investigated. Osteoblastic MC3T3-E1 cells with subconfluent monolayers were cultured for 24 or 48 h in a medium without fetal bovine serum (FBS) in the presence or absence of albumin (0.5 or 1.0 mg/ml of medium) or insulin-like growth factor-I (IGF-I; 10(-9) or 10(-8) M). The number of osteoblastic cells was significantly increased by culture for 48 h in the presence of albumin (0.5 or 1.0 mg/ml) or IGF-I (10(-9) or 10(-8) M). The effect of albumin (0.5 or 1.0 mg/ml) in increasing the cell number was not significantly modulated in the presence of IGF-I (10(-9) or 10(-8) M). Protein content in osteoblastic cells was significantly increased by culture with albumin (1.0 mg/ml). This effect was not significantly altered in the presence of IGF-I (10(-9) or 10(-8) M). Alkaline phosphatase activity was significantly decreased by culture with albumin (0.5 or 1.0 mg/ ml), while it was significantly increased in the presence of IGF-I (10(-9) or 10(-8) M). The effect of IGF-I in increasing the enzyme activity was not significantly altered in the presence of albumin (0.5 or 1.0 mg/ ml). The effect of albumin (0.5 mg/ ml) plus IGF-I (10(-9) M) in increasing the cell number was completely prevented in the presence of PD98059, suggesting that the effect of albumin or IGF-I is partly mediated through mitogen-activated protein (MAP) kinase cascade. The expression of Runx2 (type 1) mRNA using transcription-polymerase chain reaction (RT-PCR) analysis in osteoblastic cells was significantly decreased by culture for 24 or 48 h with albumin (0.5 or 1.0 mg/ml) or IGF-I (10(-9) M). alpha1 (I) collagen mRNA expression in osteoblastic cells was significantly increased by culture for 24 h with albumin (0.5 or 1.0 mg/ml) or IGF-I (10(-9) M). Albumin (0.5, 1.0, or 2.0 mg/ml) did not have a significant effect on osteoclast-like cell formation induced by culture with parathyroid hormone (PTH; 10(-7) M) in mouse marrow culture. This study demonstrates that albumin has a role in the regulation of Runx2 or alpha1 (I) collagen mRNA expression, which may be mediated through intracellular signaling pathway, in osteoblastic cells.
Ishida
Koichi
K
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Yamaguchi
Masayoshi
M
D016475:3T3 Cells; D000135:Acid Phosphatase / Q000378:metabolism; D000418:Albumins / Q000494:pharmacology*; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002452:Cell Count; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics* / Q000378:metabolism; D000090602:Collagen Type I, alpha 1 Chain; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071681:Tartrate-Resistant Acid Phosphatase
D000418:Albumins; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D050659:Core Binding Factor Alpha 1 Subunit; D005419:Flavonoids; D007527:Isoenzymes; D010281:Parathyroid Hormone; D012333:RNA, Messenger; C493716:Runx2 protein, mouse; D007334:Insulin-Like Growth Factor I; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one