Concomitantly with the shrinkage of the stably present SLSFs, we observed the emergence of arthritis-specific Thy1+ SF subpopulations (Dkk3/Lrrc15+ and Birc5/Aqp1+), accompanied by expansion of Prg4high/Thy1-LSFs. The gene discussed is BIRC5; the disease is arthritic joint disease.