PTH stimulated growth and decreased Col-X deposition are phosphotidylinositol-3,4,5 triphosphate kinase and mitogen activating protein kinase dependent in avian sterna.
Type X collagen (Col-X) deposition is a marker of terminal differentiation during chondrogenesis, in addition to appositional growth and apoptosis. The parathyroid hormone/parathyroid hormone related peptide (PTH/PTHrP) receptor, or PPR, is a G-Protein coupled receptor (GPCR), which activates several downstream pathways, moderating chondrocyte differentiation, including suppression of Col-X deposition. An Avian sterna model was used to analyze the PPR GPCR downstream kinase role in growth rate and extracellular matrix (ECM) including Col-II, IX, and X. Phosphatidylinositol kinase (PI3K), mitogen activating protein kinase (MAPK) and protein kinase A (PKA) were inhibited with specific established inhibitors LY294002, PD98059, and H89, respectively to test the hypothesis that they could reverse/inhibit the PTH/PTHrP pathway. Excised E14 chick sterna were PTH treated with or without an inhibitor and compared to controls. Sternal length was measured every 24 hr. Cultured sterna were immuno-stained using specific antibodies for Col-II, IX, or X and examined via confocal microscopy. Increased growth in PTH-treated sterna was MAPK, PI3K, and PKA dose dependent, suggesting growth was regulated through multiple pathways. Col-X deposition was rescued in PTH-treated sterna in the presence of PI3K or MAPK inhibitors, but not with the PKA inhibitor. All three inhibitors moderately disrupted Col-II and Col-IX deposition. These results suggest that PTH can activate multiple pathways during chondrocyte differentiation.
Harrington
Erik Kern
EK
Department of Biomedical Sciences, Texas A&M Health Sciences Center, Dallas, 75246, USA.
Coon
David J
DJ
Kern
Matthew F
MF
Svoboda
Kathy K H
KK
D000818:Animals; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects; D002642:Chick Embryo; D002645:Chickens; D019902:Chondrocytes / Q000187:drug effects / Q000201:enzymology*; D024043:Collagen Type II / Q000378:metabolism; D024081:Collagen Type IX / Q000378:metabolism; D024121:Collagen Type X / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism*; D015398:Signal Transduction; D013249:Sternum / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D013997:Time Factors; D046509:Tissue Culture Techniques
D024043:Collagen Type II; D024081:Collagen Type IX; D024121:Collagen Type X; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D018016:Receptors, Parathyroid Hormone; C025076:parathyroid hormone (1-34), bovine