Open Accessp21 Cip1 expression is increased in ambient oxygen, compared to estimated physiological (5%) levels in rat muscle precursor cell culture
Author(s) -
Lees S. J.,
Childs T. E.,
Booth F. W.
Publication year - 2008
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.2008.00512.x
Subject(s) - cell culture , kinase , messenger rna , cell growth , in vivo , cell cycle , transcription factor , biology , gene expression , transcription (linguistics) , cyclin dependent kinase , microbiology and biotechnology , chemistry , cell , biochemistry , gene , genetics , linguistics , philosophy
. Objective : While it is common practice to culture cells in the presence of ambient oxygen (~21% O 2 ), O 2 level observed in the physiological environment is often much lower. Previous efforts to culture a variety of different stem cells, including muscle precursor cells (MPC), under O 2 conditions that better mimic in vivo conditions have resulted in enhanced proliferation. In the present study, we hypothesized that 20% O 2 in culture represents a sufficient stimulus to cause increased expression of two key negative regulators of the cell‐cycle Cip/Kip family of cyclin‐dependent kinase inhibitors, p21 Cip1 and p27 Kip1 , in MPCs. Materials and methods : MPCs were isolated from Fischer 344 × Brown Norway F 1 hybrid male rats and O 2 was adjusted in culture using a tri‐gas incubator. Results : 5‐Bromo‐2′‐deoxyuridine incorporation, cell number and nuclear proliferating cell nuclear antigen expression were all decreased after 48 h culture in 20% O 2 , compared to 5% O 2 . Twenty per cent O 2 had no effect on either p27 Kip1 promoter activity or protein expression. Although p21 Cip1 promoter activity remained unchanged between 5% and 20% O 2 , there were significant increases in both p21 Cip1 mRNA and protein expression. Furthermore, 20% O 2 caused an increase in p21 Cip1 mRNA stability and p53 transcription factor activity. Conclusion : These findings are considered important because they reveal p21 Cip1 as a critical regulatory protein that needs to be considered when interpreting proliferation data from MPCs studied in culture. In addition, O 2 ‐dependent regulation of MPC proliferation is relevant to conditions, including sarcopenia, heart failure, cancer and muscular dystrophy, where increased oxidative stress exists.