PIWIL4 and rheumatoid arthritis: Transcripts for PIWIL2 and PIWIL4 were expressed similarly in RA and OA synovial tissues (mean PIWIL2 dCt±SEM in RA 5.3±0.7 and in OA 5.5±0.3; mean PIWIL4 dCt±SEM in RA 3.6±0.5 and in OA 2.9±0.3, Fig 1A1), while mRNA for PIWIL1 and PIWIL3 were not detectable.