title: Dynamic Compression Effects on Immature Nucleus Pulposus: a Study Using a Novel Intelligent and Mechanically Active Bioreactor.
abstract: BACKGROUND
  Previous cell culture and animal in vivo studies indicate the obvious effects of mechanical compression on disc cell biology. However, the effects of dynamic compression magnitude, frequency and duration on the immature nucleus pulposus (NP) from an organ-cultured disc are not well understood.
  
  
  OBJECTIVE
  To investigate the effects of a relatively wide range of compressive magnitudes, frequencies and durations on cell apoptosis and matrix composition within the immature NP using an intelligent and mechanically active bioreactor.
  
  
  METHODS
  Discs from the immature porcine were cultured in a mechanically active bioreactor for 7 days. The discs in various compressive magnitude groups (0.1, 0.2, 0.4, 0.8 and 1.3 MPa at a frequency of 1.0 Hz for 2 hours), frequency groups (0.1, 0.5, 1.0, 3.0 and 5.0 Hz at a magnitude of 0.4 MPa for 2 hours) and duration groups (1, 2, 4 and 8 hours at a magnitude of 0.4 MPa and frequency of 1.0 Hz) experienced dynamic compression once per day. Discs cultured without compression were used as controls. Immature NP samples were analyzed using the TUNEL assay, histological staining, glycosaminoglycan (GAG) content measurement, real-time PCR and collagen II immunohistochemical staining.
  
  
  RESULTS
  In the 1.3 MPa, 5.0 Hz and 8 hour groups, the immature NP showed a significantly increase in apoptotic cells, a catabolic gene expression profile with down-regulated matrix molecules and up-regulated matrix degradation enzymes, and decreased GAG content and collagen II deposition. In the other compressive magnitude, frequency and duration groups, the immature NP showed a healthier status regarding NP cell apoptosis, gene expression profile and matrix production.
  
  
  CONCLUSIONS
  Cell apoptosis and matrix composition within the immature NP were compressive magnitude-, frequency- and duration-dependent. The relatively high compressive magnitude or frequency and long compressive duration are not helpful for maintaining the healthy status of an immature NP.
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Pei
authors.initials: P
authors.lastname: Li
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Yibo
authors.initials: Y
authors.lastname: Gan
authors.affiliation: 2. Department of Orthopedic Surgery, Chongqing Three Gorges Central Hospital, Chongqing, 404000, China;
authors.forename: Haoming
authors.initials: H
authors.lastname: Wang
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Chengmin
authors.initials: C
authors.lastname: Zhang
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Liyuan
authors.initials: L
authors.lastname: Wang
authors.affiliation: 3. Department of Orthopedic Surgery, Xinqiao Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Yuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Lei
authors.initials: L
authors.lastname: Song
authors.affiliation: 4. Department of Orthopedic Surgery, No. 181 Hospital of PLA, Guilin, Guangxi, 541002, China.
authors.forename: Songtao
authors.initials: S
authors.lastname: Li
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Sukai
authors.initials: S
authors.lastname: Li
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Yangbin
authors.initials: Y
authors.lastname: Ou
authors.affiliation: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D000818:Animals; D017209:Apoptosis; D001696:Biomechanical Phenomena; D019149:Bioreactors; D003094:Collagen / Q000378:metabolism; D019245:Compressive Strength; D004867:Equipment Design; D015870:Gene Expression; D006025:Glycosaminoglycans / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology* / Q000254:growth & development / Q000502:physiology*; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D009924:Organ Culture Techniques / Q000295:instrumentation / Q000379:methods*; D013314:Stress, Mechanical; D034421:Sus scrofa
chemical_list: D006025:Glycosaminoglycans; D003094:Collagen; D019278:Matrix Metalloproteinase 3
keywords: bioreactor; dynamic compression.; immature; intervertebral disc degeneration; nucleus pulposus; organ culture