Prolonged culture of HOS 58 human osteosarcoma cells with 1,25-(OH)2-D3, TGF-beta, and dexamethasone reveals physiological regulation of alkaline phosphatase, dissociated osteocalcin gene expression, and protein synthesis and lack of mineralization.
Cultured rodent osteoblastic cells reiterate the phenotypic differentiation and maturation of osteoblasts seen in vivo. As previously shown, the human osteosarcoma cell line HOS 58 represents a differentiated stage of osteoblast development. The potential of HOS 58 for still further in vitro differentiation suggests the line can serve as a model of osteoblast maturation. Using this cell line, we have investigated the influence of 1,25-(OH)2-D3 (D3), TGF-beta and Dexamethasone (Dex) on proliferation and on the protein and mRNA levels of alkaline phosphatase (AP), procollagen 1 (Col 1), and osteocalcin (Oc), as well as mineralization during 28 days in culture. AP mRNA and protein were highly expressed throughout the culture period with further increase of protein AP activity at constant gene expression levels. A differentiation inhibiting effect of either TGF-beta or Dex was seen. Col 1 was investigated without the use of ascorbic acid and showed only minor changes during culture time or stimulation. The gene expression for Oc increased continually whereas protein synthesis peaked at confluence and decreased thereafter. TGF-beta and Dex treatments decreased Oc mRNA and protein levels. Stimulation by D3 was maximal at day 7 with a decrease thereafter. HOS 58 cells showed no mineralization capacity when stimulated with different agents, as measured by energy-dispersive X-ray microanalysis. This was not due to absence of Cbfa1 expression. In conclusion, the HOS 58 osteosarcoma cell line represents a differentiated cell line with highly expressed and physiologically regulated AP expression during further differentiation in culture. We observed a dissociation between osteocalcin gene expression and protein secretion which may contribute to the lack of mineralization in this cell line.
Siggelkow
Heide
H
Department for Gastroenterology and Endocrinology, Georg-August-University, Göttingen, Germany. hsiggel@med.uni-goettingen.de
Schenck
Michael
M
Rohde
Manfred
M
Viereck
Volker
V
Tauber
Simone
S
Atkinson
Michael J
MJ
Hüfner
Michael
M
D000328:Adult; D000469:Alkaline Phosphatase / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D002113:Calcification, Physiologic; D002117:Calcitriol / Q000494:pharmacology*; D024042:Collagen Type I / Q000235:genetics* / Q000378:metabolism; D050657:Core Binding Factor alpha Subunits; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008297:Male; D051379:Mice; D008855:Microscopy, Electron, Scanning; D015675:Osteocalcin / Q000235:genetics* / Q000378:metabolism; D012516:Osteosarcoma / Q000188:drug therapy* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D024042:Collagen Type I; D050657:Core Binding Factor alpha Subunits; D017931:DNA Primers; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C406688:core binding factor alpha; D015675:Osteocalcin; D003907:Dexamethasone; D000469:Alkaline Phosphatase; D002117:Calcitriol