Osteoblasts and osteoclasts express PEDF, VEGF-A isoforms, and VEGF receptors: possible mediators of angiogenesis and matrix remodeling in the bone
Section snippets
Materials and methods
Northern blot analysis. RNA was extracted from tissues at various stages of embryonic and postnatal Balb/C mice using the Nucleospin RNA kit (Clontech). Five micrograms of RNA was electrophoresed in formaldehyde gels, transblotted, and UV cross-linked onto nitrocellulose membranes. Blots were hybridization for 1 h with 32P-labeled full-length human PEDF cDNA or a 32P-labeled β-actin probe as an internal RNA control. Unbound probes were washed off 2 × 15 min using 2× SSC, RT, 2 × 30 min using 2×
PEDF is expressed in mouse tissues during embryological and postnatal development
In mouse, the PEDF gene is transcribed as a 1.5 kb transcript. To detect whether PEDF was expressed throughout mouse development we carried out a Northern blot analysis using RNA prepared from different ages of embryo and postnatal mice. As shown in Fig. 1, a 1.5 kb PEDF RNA was detected from the earliest ages examined and the amount of PEDF increased during development as compared with the actin control.
PEDF transcripts are detected in bone matrix
To identify specific structures in the developing embryo that expressed the PEDF transcript,
Discussion
Angiogenesis is a tightly regulated process in which the actions of proangiogenic factors are counterbalanced by the actions of anti-angiogenic factors. During bone development, as in many other tissues, VEGF-A appears to be the major proangiogenic factor required to induce new vessel growth [1]. The identity of a major anti-angiogenic factor that can counteract the activity of VEGF in bone has not previously been described. In other tissues, PEDF is thought to be the major factor balancing the
Acknowledgements
We thank Dr. Mark Horowtiz of the Yale Core Center for Musculoskeletal Disorders (supported by NIH Grant AR46032) for osteoblast and osteoclast cultures, Steve Viviano and Adrienne LaRue (YALE), and Nuria Lara and Sam Apricio (UMKC) for excellent technical assistance. This work was supported by grants from the NIH and the David Woods Kemper Memorial Foundation.
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