Fig 1: Accelerated chondrogenesis in SHIP-1 KO PaS MSCs. PaS MSC pellets differentiated in vitro for 21 days using the Mouse StemXVivo Chondrogenic Base Media and Supplement were fixed, paraffin embedded, sectioned and IHC-stained. (a and b) Sections from WT (a) and SHIP-1 KO (b) PaS MSC pellets were stained with an antibody against the early chondrogenic lineage marker Col II. Bound antibody was visualized in bright red with a NorthernLights 557-conjugated anti-sheep secondary antibody. (c and d) Sections from WT (c) and SHIP-1 KO (d) PaS MSC pellets were stained with a bright red eFluor570-conjugated antibody against the hypertrophic chondrocyte lineage marker Col X. (e and f) Sequential sections from the same WT cell pellet as in (c) and from the same SHIP-1 KO cell pellet as in (d) were subjected to H&E staining. Magnification: ×200 (a–d); ×400 (e and f). Scale bar = 50 µm. (g) Left panel, the difference in cell sizes between WT and SHIP-1 KO PaS MSCs after chondrogenic induction was quantified by using the NIH ImageJ program and indicated as ImageJ Area Units. Middle and right panels, gene expression levels of Col2a1 and Col10a1 were evaluated by quantitative real-time PCR. GAPDH expression was assessed as an internal reference for quantification. Gene expression levels were expressed as relative fold increase over the internal control. Student's t test was performed and p < .05 is considered significant. Col II, collagen type II; Col X, collagen type X; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; H&E, hematoxylin and eosin; IHC, immunohistochemical; MSC, mesenchymal stem cell; PCR, polymerase chain reaction; SHIP-1, SH2-containing inositol-5'-phosphatase-1; WT, wild-type [Color figure can be viewed at wileyonlinelibrary.com]