title: Parathyroid hormone stimulates proliferation of chondroprogenitor cells in vitro.
abstract: Mandibular condylar explants of newborn ICR mice were maintained as serum-free organ culture systems and were used to study the effects of 0.1-10.0U/ml parathyroid hormone (PTH) on the morphology of the organ and the ultrastructure of the chondroprogenitor cells. Parameters of proliferation such as 3H-thymidine autoradiography and incorporation into the explants were also studied. The chondroprogenitoric zone gradually increased with increasing dosages of the hormone up to a maximum of 5-fold of the control with 5.0 U/ml PTH. Autoradiographic studies showed a 3-fold increase in the number of 3H-thymidine-labeled cells in the chondroprogenitoric zone of PTH-treated explants. This was matched by a dose-dependent stimulation of 3H-thymidine incorporation, reaching maximal values at 5.0 U/ml PHT. At this concentration, the stimulated incorporation of 3H-thymidine was found to be dependent on the Ca2+ concentration of the medium. Chondroprogenitor cells located adjacent to the chondroblastic zone tended to pile up and aggregate in "syncytium"-like clusters, establishing intercellular gap junctions. All PTH-treated chondroprogenitor cells demonstrated large deposits of glycogen and highly elaborated stacks of their Golgi systems; the latter were associated with large numbers of vesicular elements. On the other hand, the chondroblastic zone was significantly reduced in size. Hence, it seems that PTH possesses a rather intense mitogenic effect upon chondroprogenitor cells and might possibly interfere with their normal pattern of differentiation into mature cartilage cells.
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002356:Cartilage / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D008335:Mandibular Condyle / Q000187:drug effects / Q000254:growth & development; D051379:Mice; D008813:Mice, Inbred ICR; D009924:Organ Culture Techniques; D010281:Parathyroid Hormone / Q000494:pharmacology*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism
chemical_list: D010281:Parathyroid Hormone; D013936:Thymidine