title: Extracellular calcium and parathyroid hormone-related peptide signaling modulate the pace of growth plate chondrocyte differentiation.
abstract: An adequate supply of Ca2+ is critical for normal growth plate development. Previous studies suggest that changes in extracellular [Ca2+] ([Ca2+]e) modulate the function of chondrocytes with high [Ca2+]e promoting cell differentiation. In contrast, signal transduction by the PTH/PTHrP type I receptor (PTH1R) slows down chondrocyte differentiation. This study addressed whether changes in [Ca2+]e modulate the differentiation of mouse growth plate chondrocytes by interacting with PTHrP/PTH1Rs. Raising [Ca2+]e from 0.5-3.0 mM dose-dependently promoted the development of mouse growth plate chondrocytes as indicated by decreases in proteoglycan accumulation and in the expression of early differentiation marker genes and by increases in mineral deposition and in the expression of markers of terminal differentiation. The effects of high [Ca2+]e on gene expression and matrix synthesis were blunted by incubating cells with PTHrP and vice versa. High [Ca2+]e also suppressed the expression of PTH1Rs. Chronic stimulation of PTHrP/PTH1R signaling by adenoviral expression of constitutively active human PTH1Rs (223hPTH1Rs) reduced the effects of high [Ca2+]e on proteoglycan synthesis and gene expression. Similar results were seen when we treated cells with forskolin or 8-bromo-cAMP. Taken together, these data support the idea that the pace of chondrocyte differentiation depends on a balance of interactions between PTHrP/PTH1R and extracellular Ca2+ signaling and that high [Ca2+]e promote cell differentiation potentially by reducing the availability of PTH1Rs and the level of cAMP-dependent signal transduction.
authors.affiliation: Endocrine Research Unit, Department of Veterans Affairs Medical Center, University of California, San Francisco, California 94121, USA.
authors.forename: Luis
authors.initials: L
authors.lastname: Rodriguez
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Cheng
authors.forename: Tsui-Hua
authors.initials: TH
authors.lastname: Chen
authors.forename: Chialing
authors.initials: C
authors.lastname: Tu
authors.forename: Wenhan
authors.initials: W
authors.lastname: Chang
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology*; D000242:Cyclic AMP / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D018014:Gene Transfer Techniques; D006132:Growth Plate / Q000166:cytology*; D006801:Humans; D051379:Mice; D009994:Osmolar Concentration; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism* / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C473449:PTH1R protein, human; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone; C054296:parathyroid hormone-related protein (1-34); D000242:Cyclic AMP; D002118:Calcium