Fig. 6. Hedgehog signaling accelerates chondrocyte hypertrophy in postnatal cartilage. (A) Skeletal preparations of P15 forelimb and hindlimb of the Ptch1^c/c;Col2a1-CreER and wild-type mouse. Unmineralized cartilage in the hand, shoulder and knee joints and the scapula was reduced in the mutant, as shown at high magnification. (Ba-d) Serial sections of distal femur of P12 mice were stained with Safranin O and used for immunohistochemistry to detect Col2a1 expression. There were more hypertrophic chondrocytes with reduced Col2a1 expression in the Ptch1^c/c;Col2a1-CreER mouse. (Be-j) Sections of proximal humeri from one-year-old mice were stained with Safranin O. Boxed regions in e and f are shown at higher magnifications in g,h. Cartilage lining was thinner in the Ptch1^c/c;Col2a1-CreER mouse (arrow). (i,j) Higher magnification of articular cartilage of the proximal humerus. Joint cartilage in the Ptch1^c/c;Col2a1-CreER mouse was significantly reduced (double-headed arrows). (Ca-d) Sections of proximal humeri from 14-month-old mice were stained with Safranin O. Boxed regions in a and b are shown at higher magnifications in c,d. Cartilage lining was thicker in the Smo^c/c;Col2a1-CreER mouse (arrow). (Ce,f) Higher magnification of articular cartilage of the proximal humerus. Joint cartilage in the Smo^c/c;Col2a1-CreER mouse was significantly thicker (double-headed arrows).