Fig. 2. Cell autonomous upregulation of Hh signaling in the absence of PTHrP accelerates chondrocyte hypertrophy.

(A) Skeletal preparation of embryos at E14.5. Alizarin Red stains mineralized cartilage and bone tissues; Alcian Blue stains unmineralized cartilage. A higher magnification view of the forelimb is shown in the lower panel. S, scapula; H, humerus; R, radius; U, ulna. (B) Serial sections of distal humerus were stained with Safranin O and hybridized with indicated ³⁵S labeled riboprobes. The boxed articular and columnar chondrocytes regions are shown at higher magnification in the panels below. Columnar chondrocytes are indicated by yellow brackets and arrows. Both Ptch1^c/−;Col2a1-Cre and PTHrP^−/−;Ptch1^c/−;Col2a1-Cre mutants show strong upregulation of Gli1 and Hip1, downstream target genes of Hh signaling, in the perichondrium and synovial joint. The Col2a1-expressing region (white line) is reduced and the Col10a1-expressing domain (yellow line) is closer to the joint in the PTHrP^−/−;Ptch1^c/−;Col2a1-Cre mutant.