title: Phenotypic characterization of epiphycan-deficient and epiphycan/biglycan double-deficient mice.
abstract: OBJECTIVE
  To characterize the in vivo role epiphycan (Epn) has in cartilage development and/or maintenance.
  
  
  METHODS
  Epn-deficient mice were generated by disrupting the Epn gene in mouse embryonic stem cells. Epn/biglycan (Bgn) double-deficient mice were produced by crossing Epn-deficient mice with Bgn-deficient mice. Whole knee joint histological sections were stained using van Gieson or Fast green/Safranin-O to analyze collagen or proteoglycan content, respectively. Microarray analysis was performed to detect gene expression changes within knee joints.
  
  
  RESULTS
  Epn-deficient and Epn/Bgn double-deficient mice appeared normal at birth. No significant difference in body weight or femur length was detected in any animal at 1 month of age. However, 9-month Epn/Bgn double-deficient mice were significantly lighter and had shorter femurs than wild type mice, regardless of gender. Male Epn-deficient mice also had significantly shorter femurs than wild type mice at 9 months. Most of the deficient animals developed osteoarthritis (OA) with age; the onset of OA was observed earliest in Epn/Bgn double-deficient mice. Message RNA isolated from Epn/Bgn double-deficient knee joints displayed increased matrix protein expression compared with wild type mice, including other small leucine-rich proteoglycan (SLRP) members such as asporin, fibromodulin and lumican.
  
  
  CONCLUSIONS
  Similar to other previously studied SLRPs, EPN plays an important role in maintaining joint integrity. However, the severity of the OA phenotype in the Epn/Bgn double-deficient mouse suggests a synergy between these two proteins. These data are the first to show a genetic interaction involving class I and class III SLRPs in vivo.
authors.affiliation: Texas A&M University System Health Science Center, Albert B Alkek Institute of Biosciences and Technology, Center for Extracellular Matrix Biology, Houston, TX 77030, USA.
authors.forename: S
authors.initials: S
authors.lastname: Nuka
authors.forename: W
authors.initials: W
authors.lastname: Zhou
authors.forename: S P
authors.initials: SP
authors.lastname: Henry
authors.forename: C M
authors.initials: CM
authors.lastname: Gendron
authors.forename: J B
authors.initials: JB
authors.lastname: Schultz
authors.forename: T
authors.initials: T
authors.lastname: Shinomura
authors.forename: J
authors.initials: J
authors.lastname: Johnson
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: D R
authors.initials: DR
authors.lastname: Keene
authors.forename: R
authors.initials: R
authors.lastname: Ramírez-Solis
authors.forename: R R
authors.initials: RR
authors.lastname: Behringer
authors.forename: M F
authors.initials: MF
authors.lastname: Young
authors.forename: M
authors.initials: M
authors.lastname: Höök
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D001835:Body Weight; D003094:Collagen / Q000032:analysis; D005269:Femur / Q000033:anatomy & histology; D007150:Immunohistochemistry; D007719:Knee Joint / Q000737:chemistry* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D046228:Microarray Analysis; D020370:Osteoarthritis, Knee / Q000235:genetics / Q000503:physiopathology*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011509:Proteoglycans / Q000032:analysis* / Q000172:deficiency* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D011509:Proteoglycans; D012333:RNA, Messenger; D003094:Collagen