The p27 Pathway Modulates the Regulation of Skeletal Growth and Osteoblastic Bone Formation by Parathyroid Hormone-Related Peptide.
Parathyroid hormone-related peptide (PTHrP) 1-84 knock-in mice (Pthrp KI) develop skeletal growth retardation and defective osteoblastic bone formation. To further examine the mechanisms underlying this phenotype, microarray analyses of differential gene expression profiles were performed in long bone extracts from Pthrp KI mice and their wild-type (WT) littermates. We found that the expression levels of p27, p16, and p53 were significantly upregulated in Pthrp KI mice relative to WT littermates. To determine whether p27 was involved in the regulation by PTHrP of skeletal growth and development in vivo, we generated compound mutant mice, which were homozygous for both p27 deletion and the Pthrp KI mutation (p27(-/-) Pthrp KI). We then compared p27(-/-) Pthrp KI mice with p27(-/-), Pthrp KI, and WT littermates. Deletion of p27 in Pthrp KI mice resulted in a longer lifespan, increased body weight, and improvement in skeletal growth. At 2 weeks of age, skeletal parameters, including length of long bones, size of epiphyses, numbers of proliferating cell nuclear antigen (PCNA)-positive chondrocytes, bone mineral density, trabecular bone volume, osteoblast numbers, and alkaline phosphatase (ALP)-, type I collagen-, and osteocalcin-positive bone areas were increased in p27(-/-) mice and reduced in both Pthrp KI and p27(-/-) Pthrp KI mice compared with WT mice; however, these parameters were increased in p27(-/-) Pthrp KI mice compared with Pthrp KI mice. As well, protein expression levels of PTHR, IGF-1, and Bmi-1, and the numbers of total colony-forming unit fibroblastic (CFU-f) and ALP-positive CFU-f were similarly increased in p27(-/-) Pthrp KI mice compared with Pthrp KI mice. Our results demonstrate that deletion of p27 in Pthrp KI mice can partially rescue defects in skeletal growth and osteoblastic bone formation by enhancing endochondral bone formation and osteogenesis. These studies, therefore, indicate that the p27 pathway may function downstream in the action of PTHrP to regulate skeletal growth and development.
State Key Laboratory of Reproductive Medicine, The Research Center for Bone and Stem Cells, Department of Anatomy, Histology, and Embryology, Nanjing Medical University, Nanjing, People's Republic of China.
Min
M
Zhu
Department of Human Anatomy, Basic Medical College of Nanchang University, Nanchang, People's Republic of China.
Jing
J
Zhang
State Key Laboratory of Reproductive Medicine, The Research Center for Bone and Stem Cells, Department of Anatomy, Histology, and Embryology, Nanjing Medical University, Nanjing, People's Republic of China.
Zhan
Z
Dong
State Key Laboratory of Reproductive Medicine, The Research Center for Bone and Stem Cells, Department of Anatomy, Histology, and Embryology, Nanjing Medical University, Nanjing, People's Republic of China.
Ying
Y
Zhang
State Key Laboratory of Reproductive Medicine, The Research Center for Bone and Stem Cells, Department of Anatomy, Histology, and Embryology, Nanjing Medical University, Nanjing, People's Republic of China.
Rong
R
Wang
Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Canada.
Andrew
A
Karaplis
Calcium Research Laboratory, McGill University Health Centre and Department of Medicine, McGill University, Montreal, Canada.
David
D
Goltzman
State Key Laboratory of Reproductive Medicine, The Research Center for Bone and Stem Cells, Department of Anatomy, Histology, and Embryology, Nanjing Medical University, Nanjing, People's Republic of China.
Dengshun
D
Miao
D000818:Animals; D001835:Body Weight; D001846:Bone Development; D001854:Bone Marrow Cells / Q000166:cytology; D001862:Bone Resorption / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D055879:Gene Knock-In Techniques; D008136:Longevity; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009929:Organ Size; D010006:Osteoblasts / Q000378:metabolism*; D010010:Osteoclasts / Q000473:pathology; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism*; D015398:Signal Transduction
D044162:Parathyroid Hormone-Related Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27
OSTEOBLASTIC BONE FORMATION; PTHrP; SKELETAL GROWTH; p27