title: Role of the ERK1/2 pathway in osmolarity effects on nucleus pulposus cell apoptosis in a disc perfusion culture.
abstract: 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.
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Yibo
authors.initials: Y
authors.lastname: Gan
authors.affiliation: Department of Orthopedic Surgery, Chongqing Three Gorges Central Hospital, Chongqing 404000, China.
authors.forename: Haoming
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Orthopedic Surgery, No. 181 Hospital of PLA, Guilin, Guangxi 541002, China.
authors.forename: Songtao
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Song
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Chengmin
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Yangbin
authors.initials: Y
authors.lastname: Ou
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Liyuan
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, GaoTanYan 29, Chongqing 400038, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D020935:MAP Kinase Signaling System; D008297:Male; D000070614:Nucleus Pulposus / Q000502:physiology*; D009994:Osmolar Concentration; D014176:Protein Biosynthesis; D013552:Swine; D046509:Tissue Culture Techniques
chemical_list: D053148:Caspase 3
keywords: ERK1/2; apoptosis; intervertebral disc; nucleus pulposus; osmolarity