Aggrecan is decreased and MMP13 increased in growth plates of Smad4-deficient mice. (A-D) Immunofluorescence of tibial growth plates demonstrates decreased protein levels of aggrecan in the Col2-Cre+/−;Smad4fl/fl (Cre+) growth plate (C,D) relative to the Cre− growth plate (A,B); whereas MMP13 immunofluorescence of tibial growth plates demonstrates increased MMP13 protein in Col2-Cre+/−;Smad4fl/fl (Cre+) growth plates (H, I), compared with Cre− growth plates (F,G). IgG- negative controls for aggrecan (E) and MMP13 (J). N=3; A-D: nuclei, blue; Aggrecan, green; F-I: nuclei, blue; MMP13, green; E,J: nucleui, blue; IgG, green.