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. 2010 Apr 5;30(11):2799–2810. doi: 10.1128/MCB.00157-10

FIG. 4.

FIG. 4.

Primary costal chondrocytes and ATDC5 cells with reduced calpain activity exhibited impaired cell growth, reduced mRNA expression of the cyclin D1 gene and early differentiation markers of cells of the chondrocyte lineage. (A) Expression of Capn4 and cyclin D1 mRNA was significantly reduced in Capn4-null primary chondrocytes. (B) Expression of markers for chondrocyte differentiation was reduced in Capn4-null chondrocytes. Relative levels of expression of Capn4, Col.10, PPR, and MMP13 RNA were determined using real-time qPCR. PPR, PTH/PTHrP receptor. (C) Cell growth of ATDC5 cells treated with a chemical calpain inhibitor, ALLM, showed reduced cell growth. (D) Reduced calpain activity reduced cyclin D1 mRNA expression in ATDC5 cells treated with ALLM. (E) Reduced calpain activity showed reduced expression of early chondrocyte differentiation markers, Col.10 and PPR, in ATDC5 cells treated with ALLM. (F) Transient expression of Capn4 siRNA impaired cell growth in ATDC5 cells. (G) Transient expression of Capn4 siRNA showed significantly reduced cyclin D1 mRNA expression. (H) Expression of early chondrocyte differentiation markers, Col.10 and PPR, was reduced in ATDC5 cells transiently expressing Capn4 siRNA. *, P < 0.05; **, P < 0.005; and ***, P < 0.001.