title: Chondrocyte p21(WAF1/CIP1) expression is increased by dexamethasone but does not contribute to dexamethasone-induced growth retardation in vivo.
abstract: It has been shown that cell cycle genes play an important role in the coordination of chondrocyte proliferation and differentiation. The inhibitory effects of glucocorticoids (GCs) on chondrocyte proliferation are consistent with GCs disrupting cell cycle progression and promoting cell cycle exit. Cyclin-dependent kinase inhibitors (CDKIs) force cells to exit the cell cycle and differentiate, and studies have shown that expression of the CDKI p21(CIP1/WAF1) is increased in terminally differentiated cells. In this study, p21 mRNA and protein expression was increased during chondrocyte differentiation and after exposure to dexamethasone (Dex, 10(-6 )M) in murine chondrogenic ATDC5 cells. In 4-week-old mice lacking a functional p21 gene, Dex caused a reduction in body weight compared to saline control null mice, but this was consistent with the reduction in body weight observed in Dex-treated wild-type littermates. In addition, p21 ablation had no effect on the reduction in width of the growth plate or reduced mineral apposition rate in Dex-treated mice. However, an alteration in growth rate and epiphyseal structure is evident when comparing p21(-/-) and wild-type mice. These findings suggest that p21 does not directly contribute to GC-induced growth retardation in vivo but is involved in the maintenance of the growth plate.
authors.affiliation: Bone Biology Group, Division of Developmental Biology, The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Edinburgh, Midlothian, EH25 9PS, UK.
authors.forename: H C
authors.initials: HC
authors.lastname: Owen
authors.forename: S F
authors.initials: SF
authors.lastname: Ahmed
authors.forename: C
authors.initials: C
authors.lastname: Farquharson
mesh_terms: D000818:Animals; D001835:Body Weight; D015519:Bone Density / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D003907:Dexamethasone / Q000009:adverse effects / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D005938:Glucocorticoids / Q000009:adverse effects / Q000494:pharmacology*; D006130:Growth Disorders / Q000139:chemically induced / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D005938:Glucocorticoids; D003907:Dexamethasone