Expression of proinflammatory cytokines and growth factors at the injured growth plate cartilage in young rats

Fiona H. Zhou, Bruce K. Foster, Guy Sander, Cory J. Xian

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

Growth plate, a cartilage-like tissue responsible for bone lengthening in children, has limited abilities to regenerate. After injury, a bony repair often occurs at the injury site, which may lead to growth arrest or angulation of the involved long bone. Our previous study has demonstrated inflammatory, fibrogenic, and osteogenic responses at the injured growth plate; however, the underlying mechanisms remain unclear. In this study, mRNA expression patterns of pro-inflammatory cytokines, growth factors, transcription factors, and matrix proteins were examined by quantitative RT-PCR over a 35-day time period after a drill-hole injury at the proximal tibial growth plate of young rats. During the initial inflammatory phase, IL-1β expression peaked at 8-16 h, and TNF-α and TGF-β1 levels peaked on day 1. During the subsequent fibrogenic response, expression of growth factors FGF-2 and PDGF-B was up-regulated on day 3 whereas levels of collagen-2a and transcription factor Sox9 remained unchanged. In the osteogenic and bone remodeling stages, levels of TNF-α, FGF-2, and TGF-β1 rose again during days 25-35, and IGF-I and bone matrix protein osteocalcin elevated from days 7 to 35. The positive changes in expression of IL-1β, TNF-α, TGF-β1, and IGF-I suggest their possible roles in the early acute inflammatory event and later in the formation and remodeling of the bone bridge. The up-regulation of FGF-2 and PDGF-B, coinciding with mesenchymal cell infiltration, suggests their possible involvement in the intermediate fibrogenic response. The lack of up-regulation of Col-2a and Sox9 refutes the involvement of endochondral ossification but confirms a direct bone formation response during bone bridge formation at the injured growth plate.

Original languageEnglish
Pages (from-to)1307-1315
Number of pages9
JournalBone
Volume35
Issue number6
DOIs
Publication statusPublished - Dec 2004

Keywords

  • Bone bridge
  • Growth factors
  • Growth plate
  • Injury
  • Proinflammatory cytokines

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Histology

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