Immunolocalization of the angiogenetic factor pleiotrophin (PTN) in the growth plate of mice

The aim of this study was to find out whether and where the angiogenic agen t pleiotrophin (PTN) occurs within the growth plate. We investigated paraff in-embedded tissue sections of ten male mice with an antibody directed agai nst the recombinant PTN. Immunostaining for PTN was positive within the cyt oplasm and the pericellular matrix of osteoblasts which lined the longitudi nal mineralized septae of the epiphyseal plate. Within the zone of hypertro phic chondrocytes, immunolabelling for PTN was positive in the pericellular matrix of hypertrophic chondrocytes and within the opened lacunae of the a poptotic hypertrophic chondrocytes. The resting zone and the proliferation zone were PTN negative. The results of our study suggest that the known ang iogenetic peptide PTN plays a role in the process of angiogenesis in the gr owth plate.