title: A study in vivo of the effects of a static compressive load on the proximal tibial physis in rabbits.
abstract: BACKGROUND
  The effect of compression on the physis is generally defined by the Hueter-Volkmann principle, in which decreased linear growth of the physis results from increased compression. This investigation examined whether mechanically induced compression of rabbit physes causes changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13).
  
  
  METHODS
  Static compressive loads (10 N or 30 N) were applied for two or six weeks across one hind limb proximal tibial physis of thirteen-week-old female New Zealand White rabbits (n = 18). The contralateral hind limb in all rabbits underwent sham surgery with no load to serve as an internal control. Harvested physes were divided into portions for histological, immunohistochemical, and quantitative reverse transcription-polymerase chain reaction analysis. Gene expression was statistically analyzed by means of comparisons between loaded samples and unloaded shams with use of analysis of variance and a Tukey post hoc test.
  
  
  RESULTS
  Compared with unloaded shams, physes loaded at 10 N or 30 N for two weeks and at 10 N for six weeks showed histological changes in cells and matrices. Physes loaded at 30 N for six weeks were decreased in thickness and had structurally disorganized chondrocyte columns, a decreased extracellular matrix, and less intense type-II and X collagen immunohistochemical staining. Quantitative reverse transcription-polymerase chain reaction analysis of loaded samples compared with unloaded shams yielded a significantly (p ≤ 0.05) decreased gene expression of aggrecan and type-II and X collagen and no significant (p > 0.05) changes in the matrix metalloprotease-13 gene expression with increasing load.
  
  
  CONCLUSIONS
  Compressed rabbit physes generate biochemical changes in collagens, proteoglycan, and cellular and tissue matrix architecture. Changes potentially weaken overall physeal strength, consistent with the Hueter-Volkmann principle, and lend understanding of the causes of pathological conditions of the physis.
authors.affiliation: Department of Orthopaedic Surgery, Summa Health System, Akron, OH 44310, USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Bries
authors.forename: Dennis S
authors.initials: DS
authors.lastname: Weiner
authors.forename: Robin
authors.initials: R
authors.lastname: Jacquet
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Adamczyk
authors.forename: Melanie A
authors.initials: MA
authors.lastname: Morscher
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lowder
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Askew
authors.forename: Richard P
authors.initials: RP
authors.lastname: Steiner
authors.forename: Walter I
authors.initials: WI
authors.lastname: Horne
authors.forename: William J
authors.initials: WJ
authors.lastname: Landis
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D053674:Aggrecans / Q000235:genetics / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006132:Growth Plate / Q000254:growth & development* / Q000378:metabolism; D006614:Hindlimb; D007150:Immunohistochemistry; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013977:Tibia / Q000254:growth & development* / Q000378:metabolism
chemical_list: D000199:Actins; D053674:Aggrecans; D003094:Collagen; D053509:Matrix Metalloproteinase 13