Mizoguchi et al. [11] utilized single-cell RNA sequencing to classify three SF subsets in a study involving 26 osteoarthritis (OA) patients and 16 RA patients: cluster of differentiation 34 (D34)-Thy-1 cell surface antigen Gene (THY1, or CD90)- for the lining layer, CD34-THY1+ for the deep sublining layer, and CD34+ for both layers. The gene discussed is CD34; the disease is osteoarthritis.