title: Expression of human endogenous retrovirus HERV-K18 is associated with clinical severity in osteoarthritis patients.
abstract: OBJECTIVE
  The aim of this study was to evaluate the involvement of human endogenous retrovirus K18 (HERV-K18) in osteoarthritis (OA), by genotyping the HERV-K18 env locus in OA patients and controls, and analysing HERV-K18 RNA expression and its association with OA risk and clinical variables.
  
  
  METHODS
  We recruited 558 patients with symptomatic OA and 600 controls. We performed the genotyping by TaqMan assays and the analysis of expression by quantitative real-time polymerase chain reaction (qRT-PCR). Scores on the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC), the Lequesne index, and the Stanford Health Assessment Questionnaire (HAQ) were analysed with regard to the expression levels of HERV-K18.
  
  
  RESULTS
  The 18.3 haplotype tended towards an association with OA risk and concordantly this haplotype was associated with a higher HERV-K18 expression (p = 0.05). We found statistically significant differences when we compared the scores on the WOMAC, the Lequesne index for knee and hip, and the HAQ between OA patients with higher expression [normalization ratio (NR) > 10] and OA patients without HERV-K18 expression (p = 0.0003, 0.0005, 0.002, and 0.05, respectively), and also when the comparison was made between OA patients with higher expression (NR > 10) and OA patients with low expression of HERV-K18 (NR = 1) for the WOMAC and the Lequesne index for knee and hip (p = 0.002, 0.013, and 0.006, respectively).
  
  
  CONCLUSIONS
  We found an association between health status measurement systems and severity index for OA and the levels of expression of HERV-K18. These results suggest the possible involvement of HERV-K18 in the aetiopathogenesis of the disease.
authors.affiliation: Multiple Sclerosis Unit, San Carlos Clinic Hospital (IdISSC) , Madrid , Spain.
authors.forename: M
authors.initials: M
authors.lastname: Garcia-Montojo
authors.forename: J
authors.initials: J
authors.lastname: Varade
authors.forename: E
authors.initials: E
authors.lastname: Villafuertes
authors.forename: B
authors.initials: B
authors.lastname: de La Hera
authors.forename: J
authors.initials: J
authors.lastname: Hoyas-Fernandez
authors.forename: M I
authors.initials: MI
authors.lastname: Domínguez-Mozo
authors.forename: L
authors.initials: L
authors.lastname: Rodriguez-Rodriguez
authors.forename: P
authors.initials: P
authors.lastname: Tornero-Esteban
authors.forename: A
authors.initials: A
authors.lastname: Arias-Leal
authors.forename: L
authors.initials: L
authors.lastname: León
authors.forename: J R
authors.initials: JR
authors.lastname: Lamas
authors.forename: R
authors.initials: R
authors.lastname: Alvarez-Lafuente
authors.forename: E
authors.initials: E
authors.lastname: Urcelay
authors.forename: B
authors.initials: B
authors.lastname: Fernandez-Gutierrez
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D005838:Genotype; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000378:metabolism*; D012720:Severity of Illness Index; D013030:Spain / Q000453:epidemiology; D018089:Superantigens / Q000235:genetics* / Q000378:metabolism; D011795:Surveys and Questionnaires
chemical_list: C107453:ERVK-18 protein, human; D008565:Membrane Proteins; D018089:Superantigens; D012313:RNA