Cyclin‑dependent kinase inhibitor p21 does not impact embryonic endochondral ossification in mice.
Endochondral ossification at the growth plate is regulated by a number of factors and hormones. The cyclin‑dependent kinase inhibitor p21 has been identified as a cell cycle regulator and its expression has been reported to be essential for endochondral ossification in vitro. However, to the best of our knowledge, the function of p21 in endochondral ossification has not been evaluated in vivo. Therefore, the aim of this study was to investigate the function of p21 in embryonic endochondral ossification in vivo. Wild‑type (WT) and p21 knockout (KO) pregnant heterozygous mice were sacrificed on embryonic days E13.5, E15.5 and E18.5. Sagittal histological sections of the forearms of the embryos were collected and stained with Safranin O and 5‑bromo‑2'‑deoxyuridine (BrdU). Additionally, the expression levels of cyclin D1, type II collagen, type X collagen, Sox9, and p16 were examined using immunohistochemistry, and the expression levels of p27 were examined using immunofluorescence. Safranin O staining revealed no structural change between the cartilage tissues of the WT and p21KO mice at any time point. Type II collagen was expressed ubiquitously, while type X collagen was only expressed in the hypertrophic zone of the cartilage tissues. No differences in the levels of Sox9 expression were observed between the two groups at any time point. The levels of cyclin D1 expression and BrdU uptake were higher in the E13.5 cartilage tissue compared with those observed in the embryonic cartilage tissue at subsequent time points. Expression of p16 and p27 was ubiquitous throughout the tissue sections. These results indicate that p21 may not be essential for embryonic endochondral ossification in articular cartilage of mice and that other signaling networks may compensate for p21 deletion.
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Nobuaki
N
Chinzei
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Shinya
S
Hayashi
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Shingo
S
Hashimoto
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Noriyuki
N
Kanzaki
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Kenjiro
K
Iwasa
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Shuhei
S
Sakata
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Shinsuke
S
Kihara
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Takaaki
T
Fujishiro
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Ryosuke
R
Kuroda
Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Hyogo 650‑0017, Japan.
Masahiro
M
Kurosaka
D000818:Animals; D002356:Cartilage / Q000196:embryology* / Q000378:metabolism*; D049109:Cell Proliferation; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D051379:Mice; D018345:Mice, Knockout; D010012:Osteogenesis / Q000235:genetics*; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism
D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016326:Extracellular Matrix Proteins; D055758:SOX9 Transcription Factor; D050760:Cyclin-Dependent Kinase Inhibitor p27