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Role of the ERK1/2 pathway in osmolarity effects on nucleus pulposus cell apoptosis in a disc perfusion culture
Author(s) -
Li Pei,
Gan Yibo,
Wang Haoming,
Xu Yuan,
Li Songtao,
Song Lei,
Zhang Chengmin,
Ou Yangbin,
Wang Liyuan,
Zhou Qiang
Publication year - 2017
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.23249
Subject(s) - nucleus , apoptosis , osmotic concentration , microbiology and biotechnology , perfusion , cell culture , biology , chemistry , medicine , endocrinology , biochemistry , genetics
Osmolarity fluctuations are inevitable within the nucleus pulposus (NP). However, the effects of osmolarity on NP cell apoptosis within the organ‐cultured disc remain unclear. The objective of this study was to investigate effects of different osmolarity levels (hypo‐, iso‐, and hyper‐) and osmolarity modes (constant and cyclic) on NP cell apoptosis in a disc perfusion culture and to study the role of the ERK1/2 pathway in this regulatory process. Porcine discs were cultured for 7 days in different osmotic medium, including constant hypo‐, iso‐, and hyper‐osmolarity (330, 430, and 550 mOsm/L, respectively) and cyclic‐osmolarity (430 mOsm/L for 8 h, followed by 550 mOsm/L for 16 h). The role of the ERK1/2 pathway was investigated by using the pharmacological inhibitor U0126. NP cell apoptosis was analyzed by TUNEL staining, caspase‐3 activity, gene expression of Bcl‐2, Bax and caspase‐3 and protein expression of cleaved caspase‐3, and cleaved PARP. Our results showed that NP cell apoptosis was increased in hypo‐ and hyper‐osmolarity cultures compared to iso‐ or cyclic‐osmolarity culture, whereas the level of apoptosis in the iso‐osmolarity culture was lower than that in the cyclic‐osmolarity culture. When the ERK1/2 pathway was inhibited in the iso‐ and cyclic‐osmolarity cultures, the level of NP cell apoptosis was significantly increased. In conclusion, the effects of osmolarity on NP cell apoptosis depend on the osmolarity level (hypo‐, iso‐, or hyper‐) and osmolarity mode (constant or cyclic). Futhermore, inhibition of the ERK1/2 pathway promotes NP cell apoptosis in this process. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:86–92, 2017.