Figure 4.

Alpl^−/− primary chondrocytes exhibit increased proteoglycan accumulation and diminished proliferation. (A,B) Primary rib chondrocytes isolated from Alpl^+/+ and Alpl^−/− mice were cultured with or without ascorbate to induce chondrocyte differentiation. TNAP enzyme activity was visualized by incubation of cells with a colorimetric substrate and quantified by densitometry. (C,D) Primary chondrocytes were cultured under chondrocyte differentiation conditions for 15 days then stained with Alcian Blue. Staining was quantified by densitometry. (E) Cells were stained with trypan blue and counted at indicated time points after plating to assay for proliferation (black line = Alpl^+/+; gray line = Alpl^−/−). ^*p < 0.05 between genotypes.