Fig. 1

Effect of in vivo caveolin-1 inactivation on morphology and apoptosis of murine nucleus pulposus cells. a Hematoxylin and eosin–stained nucleus pulposus (NP) sections of wild-type (WT) and caveolin-1 (Cav-1)-null mice at 1.5, 3, and 6 months of age. Typical large, vacuolated notochordal cells (NCs) are present in the NP of WT mice, whereas smaller, nonvacuolated chondrocyte-like cells (CLCs) are present in the NP of caveolin-1-null mice. b The intervertebral disc (IVD) of a 1.5-month-old WT mouse stained with a terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling (TUNEL) assay shows only some brown apoptotic cell nuclei, whereas the IVD of a 1.5-month-old caveolin-1-null mouse shows many positive nuclei. NP cell numbers are significantly lower in caveolin-1-null mice than in WT mice at 1.5 and 6 months of age. The proportion of apoptotic cell nuclei (TUNEL ratio) is significantly higher in the NP of caveolin-1-null mice than in the NP of WT mice at every tested age. *p < 0.05, **p < 0.01, ***p < 0.001. n = 4–9 per age group and condition (WT or caveolin-1-null mice)