Contribution of myocardin in the hypoxia-induced phenotypic switching of rat pulmonary arterial smooth muscle cells.
BACKGROUND
Hypoxic exposure contributes to the phenotypic switching of smooth muscle cells (SMCs), while the mechanisms involved in this process is not yet fully elucidated. Myocardin as a co-actor of serum reaction factor plays a crucial role in differentiation of SMCs. This study was aimed to investigate the role of myocardin in hypoxia-induced phenotypic switching of rat pulmonary arterial SMCs (PASMCs).


METHODS
Primary PASMCs were cultured under normoxia and hypoxia (3%O(2), 48 h) respectively, and then the cell proliferation was assessed and the expression of SM22α, osteopontin (contractile and synthetic marker of SMCs, respectively), myocardin and platelet-derived growth factor-BB (PDGF-BB) were detected. After pGCSIL-GFP-shMYOCD lentviral vector was transduced to the PASMCs, the expression of myocardin and SM22α were examined. Moreover, myocardin expression in PASMCs treated with medium enriched with PDGF-BB and conditional medium (CM) from normoxia- and hypoxia-exposed PASMCs was assessed.


RESULTS
Exposing PASMCs to hypoxia led to an increased cell numbers and the up-regulation of proliferating cell nuclear antigen (PCNA), osteopontin and PDGF-BB; moreover, a significant down-regulation of SM22α and myocardin was identified. Further analysis revealed that knock-down of myocardin with pGCSIL-GFP-shMYOCD vector followed by a decreased SM22α in the PASMCs, and treatment of PASMCs with either exogenous PDGF-BB or hypoxic CM led to a marked decrease of myocardin.


CONCLUSIONS
Our findings suggest that the decrease of myocardin in PASMCs exposed to hypoxia is partly regulated by the increase of PDGF-BB, which contributes to the phenotypic switching of PASMCs in hypoxic condition.
Jie
Wei
W
Institute of Pathology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030, PR China.
Guo
Junli
J
Shen
Zhihua
Z
Wang
Xiaoyan
X
Zheng
Shaojiang
S
Wang
Guoping
G
Ao
Qilin
Q
D000818:Animals; D000077214:Becaplermin; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis*; D010641:Phenotype; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D011651:Pulmonary Artery / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000096:biosynthesis*; D000099251:Myocardin
D000077214:Becaplermin; D009687:Nuclear Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D015534:Trans-Activators; D000099251:Myocardin