FIGURE 5.

Chondrocyte-specific bcl-x knock-out mice. A, RT-PCR of Bcl-xL expression. Bcl-xL expression was specifically reduced in chondrocytes. B, gross appearance of a chondrocyte-specific bcl-x-deficient mouse (cKO) and a normal littermate (LM) at 5 weeks of age (left panel). Total axial length (from the nose to the tail end) of cKO mice was significantly reduced in cKO mice, p < 0.05. The results are expressed as the means ± S.D. of three samples. C, representative x-ray images of hind limbs of LM and cKO mice at 5 weeks of age. The total bone length of the tibia as well as the growth plate length of cKO mice was shorter than that of their normal littermates. D, bone lengths of LM and cKO mice at 5 weeks of age. FL, femoral length; TL, tibial length. The results are expressed as the means ± S.D. of three samples. ^*, significantly different, p < 0.05. E, histological analysis of the growth plates of the proximal tibia at 5 weeks of age. In cKO mice, the hypertrophic layers, as evidenced by type X collagen staining, were shorter than those in LM mice. Although Bnip3 expression levels showed no difference between LM and cKO mice, the number of cleaved caspase-7-positive cells in the prehypertrophic and hypertrophic area was increased in cKO mice. HE, hematoxylin and eosin staining. HE(H) is the higher magnification of the rectangular areas in HE(L).