Figure 1.

Phenotypic characterization of synovial fluid MSCs. After exclusion of doublets (a) and debris (b), mesenchymal stem cells (MSCs) were identified through a Boolean gating strategy according to their strong reactivity for CD13, CD44, CD73, CD90, and CD105 and intermediate to high levels of CD271 (e-f), in the absence of CD34 (f). Monocytes were defined on the basis of their relatively higher light scatter properties and CD13 and CD45 bright expression, whereas lymphocytes were identified through low scatter properties and strong CD45 reactivity. In panel (g), the automated population separator (APS) graphic representation of the Infinicyt software is shown with the three cell populations phenotypically separated by principal component analysis (PCA). I: lymphocytes; II: monocytes; III: MSCs.