Immunohistochemical analysis of the fetal epiphysis and growth plate. The epiphyses were sectioned into the central and superficial zone, the proliferation and hypertrophic zone, and the ossification zone (a). The typical morphological characteristics of the different zones can be identified by hematoxylin eosin (HE) staining. Immunohistochemical staining for PEDF, MMP13, Col I, and Col II reveals a respective zone-specific pattern. No nonspecific staining was evident in negative controls incubated with isotype normal mouse IgG control. In the postnatal epiphyseal growth plate (b), PEDF is detectable in the proliferation zone, ossification zone, and osteoblastic lining. Correspondingly, MMP13 staining is positive in the hypertrophic zone and osteoblastic lining. Bars = 50 µm.