Microarray cluster analysis of irradiated growth plate zones following laser microdissection

Int J Radiat Oncol Biol Phys. 2009 Jul 1;74(3):949-56. doi: 10.1016/j.ijrobp.2008.10.009.


Purpose: Genes and pathways involved in early growth plate chondrocyte recovery after fractionated irradiation were sought as potential targets for selective radiorecovery modulation.

Materials and methods: Three groups of six 5-week male Sprague-Dawley rats underwent fractionated irradiation to the right tibiae over 5 days, totaling 17.5 Gy, and then were killed at 7, 11, and 16 days after the first radiotherapy fraction. The growth plates were collected from the proximal tibiae bilaterally and subsequently underwent laser microdissection to separate reserve, perichondral, proliferative, and hypertrophic zones. Differential gene expression was analyzed between irradiated right and nonirradiated left tibia using RAE230 2.0 GeneChip microarray, compared between zones and time points and subjected to functional pathway cluster analysis with real-time polymerase chain reaction to confirm selected results.

Results: Each zone had a number of pathways showing enrichment after the pattern of hypothesized importance to growth plate recovery, yet few met the strictest criteria. The proliferative and hypertrophic zones showed both the greatest number of genes with a 10-fold right/left change at 7 days after initiation of irradiation and enrichment of the most functional pathways involved in bone, cartilage, matrix, or skeletal development. Six genes confirmed by real-time polymerase chain reaction to have early upregulation included insulin-like growth factor 2, procollagen type I alpha 2, matrix metallopeptidase 9, parathyroid hormone receptor 1, fibromodulin, and aggrecan 1.

Conclusions: Nine overlapping pathways in the proliferative and hypertrophic zones (skeletal development, ossification, bone remodeling, cartilage development, extracellular matrix structural constituent, proteinaceous extracellular matrix, collagen, extracellular matrix, and extracellular matrix part) may play key roles in early growth plate radiorecovery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aggrecans / genetics
  • Aggrecans / metabolism
  • Animals
  • Collagen Type I / genetics
  • Collagen Type I / metabolism
  • Dose Fractionation, Radiation
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / metabolism
  • Fibromodulin
  • Gene Expression Profiling
  • Growth Plate / metabolism
  • Growth Plate / pathology
  • Growth Plate / radiation effects*
  • Hypertrophy / genetics
  • Hypertrophy / metabolism
  • Insulin-Like Growth Factor II / genetics
  • Insulin-Like Growth Factor II / metabolism
  • Laser Therapy
  • Male
  • Matrix Metalloproteinase 9 / genetics
  • Matrix Metalloproteinase 9 / metabolism
  • Microdissection / methods
  • Oligonucleotide Array Sequence Analysis / methods
  • Polymerase Chain Reaction / methods
  • Proteoglycans / genetics
  • Proteoglycans / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Parathyroid Hormone, Type 1 / genetics
  • Receptor, Parathyroid Hormone, Type 1 / metabolism
  • Tibia / radiation effects
  • Up-Regulation


  • Aggrecans
  • Collagen Type I
  • Extracellular Matrix Proteins
  • Fmod protein, rat
  • Proteoglycans
  • Receptor, Parathyroid Hormone, Type 1
  • Fibromodulin
  • Insulin-Like Growth Factor II
  • Matrix Metalloproteinase 9