Endogenous parathyroid hormone-related peptide enhances proliferation and inhibits differentiation in the osteoblast-like cell line ROS 17/2.8.
To investigate potential effects of endogenous parathyroid hormone-related peptide (PTHrP) on osteoblast function, ROS 17/2.8 cells were transfected with full-length PTHrP cDNA in a sense or antisense orientation to alter PTHrP production. Compared with vector-transfected control cells, PTHrP-overproducing (sense-transfected) cells showed increased DNA synthesis ([(3)H]-thymidine incorporation) and increased growth (cell number). The extent of apoptosis was compared for the different clones using the terminal deoxynucleotide-mediated dUTP nick-end-labeling assay (TUNEL) and Hoechst staining. No differences in percentages of apoptotic cells were found under basal culture conditions or after 3 days of serum deprivation, which, itself, markedly increased numbers of apoptotic cells. The effect of PTHrP on osteoblast differentiation was assessed by examining two protein markers of differentiation, alkaline phosphatase, and bone morphogenetic protein (BMP)-2. Alkaline phosphatase activity was decreased in sense-transfected cells and increased in antisense-transfected cells, compared with cells transfected with empty vector. PTHrP-overproducing cells also showed decreased numbers of BMP-2-positive cells, whereas antisense-transfected cells showed no difference compared with vector control. The results indicate that: (a) endogenously produced PTHrP can increase growth of these osteoblastic cells by stimulating proliferation while not affecting apoptosis; and (b) the increased cell proliferation produced by PTHrP was accompanied by a reduction in activity or amount of two proteins normally expressed by differentiated osteoblasts.
Du
P
P
Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, TX 77555-0132, USA.
Ye
Y
Y
Seitz
P K
PK
Bi
L G
LG
Li
H
H
Wang
C
C
Simmons
D J
DJ
Cooper
C W
CW
D000469:Alkaline Phosphatase / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D001483:Base Sequence; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers; D004261:DNA Replication / Q000502:physiology; D020287:In Situ Nick-End Labeling; D010006:Osteoblasts / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D017931:DNA Primers; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D000469:Alkaline Phosphatase