title: Matrix homeostasis within the immature annulus fibrosus depends on the frequency of dynamic compression: a study based on the self-developed mechanically active bioreactor.
abstract: Evidence suggests that mechanical load is related to structural destruction of disk annulus fibrosus (AF) either in adult disk degeneration or in child disk acute injury. Both biochemical and biomechanical properties are different between immature and mature disks. However, the effects of mechanical compression on immature AF are not fully clear. This study was to investigate the effects of a relatively wide range of dynamic compressive frequency on matrix homeostasis within the immature AF. Immature disks from pig (3-4 months) were randomly assigned into the control group (non-compression) and compression groups (0.1, 0.5, 1.0, 3.0 and 5.0 Hz). All disks were bioreactor-cultured for 7 days. AF matrix production was evaluated by histology, gene expression, glycosaminoglycan (GAG) content, hydroxyproline (HYP) content and immunohistochemistry. Generally, no obvious difference was found in HE staining between control group and compression groups. However, alcian blue staining indicated proteoglycan content in the 5.0-Hz group was decreased compared with the control group and other compression groups. Similarly, a catabolic remodeling gene expression profile with the down-regulated matrix genes (aggrecan, collagen I and collagen II) and tissue inhibitor of metalloproteinases (TIMP-1 and TIMP-3) and the up-regulated matrix catabolic enzymes (ADAMTS-4 and MMP-3) was found in the 5.0-Hz group. Further analysis indicated that GAG content, HYP content and aggrecan protein deposition were also decreased in the 5.0-Hz group. Hence, we concluded that matrix homeostasis within the immature AF was compressive frequency dependent, and the relatively higher frequency (5.0 Hz) is unfavorable for matrix production within the immature AF. These findings will contribute to further understanding of the relationship between mechanical compression and immature AF biosynthesis.
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Pei
authors: P
authors: Li
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Yibo
authors: Y
authors: Gan
authors: Department of Orthopedic Surgery, Xinqiao Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Yuan
authors: Y
authors: Xu
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Lei
authors: L
authors: Song
authors: Department of Orthopedic Surgery, Chongqing Three Gorges Central Hospital, Chongqing, 404000, China.
authors: Haoming
authors: H
authors: Wang
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Chengmin
authors: C
authors: Zhang
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Liyuan
authors: L
authors: Wang
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Chen
authors: C
authors: Zhao
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Lei
authors: L
authors: Luo
authors: Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China. zq_tlh@163.com.
authors: Qiang
authors: Q
authors: Zhou
mesh_terms: D000071121:ADAMTS4 Protein / Q000235:genetics; D000818:Animals; D000070616:Annulus Fibrosus / Q000166:cytology / Q000378:metabolism*; D019149:Bioreactors; D005786:Gene Expression Regulation; D006706:Homeostasis / Q000235:genetics; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D055595:Mechanical Phenomena; D013552:Swine; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics; D059467:Transcriptome
chemical_list: D019715:Tissue Inhibitor of Metalloproteinase-1; D019717:Tissue Inhibitor of Metalloproteinase-3; D019278:Matrix Metalloproteinase 3; D000071121:ADAMTS4 Protein
keywords: Annulus fibrosus; Compression; Frequency; Immature; Matrix homeostasis