Oligodeoxynucleotide targeted to the alpha(v) gene inhibits alpha(v) integrin synthesis, impairs osteoclast function, and activates intracellular signals to apoptosis

The or, integrin subunit is highly expressed in osteoclasts where it dimerizes with beta(1) and beta(3) subunits to form receptors for vitronectin and bone sialoproteins. Inhibition of osteoclast adhesion and function has previously been achieved by alpha(v)beta(3) antibodies or Arg-Gly-Asp-containing peptides which have the disadvantages of blocking a single receptor type, or of being rather nonspecific, respectively. Here we show that alpha(v) integrin expression in rabbit osteoclasts can be inhibited by partially phosphorothioated antisense oligodeoxynucleotide (ODN) spanning the adenine-uracil-guarine (AUG) translational start site of the human/rabbit alpha(v) gene, a procedure which offers the advantage of affecting all the alpha(v) receptors with high efficiency, The alpha(v) antisense ODN caused a dose-dependent, substrate-specific reduction of osteoclast adhesion and bone resorption. Control ODNs, such as sense, inverted, and mismatch, were without effect, providing evidence of specificity of the antisense reagent. It is likely as a consequence of loss of substrate interaction, the antisense ODN induced osteoclast retraction and apoptosis, increase of the cyclin/cyclin-dependent kinase complex inhibitor p21(WAF1/CIP1), and inhibition of the cell survival gene, bcl-2. Although the expression of the cell death-promoting gene, bax, remained unchanged, a reduction of the bcl-2/bax ratio, known to underlie the intracellular signal to apoptosis, was observed. This finding led us to hypothesize that these changes could provide a link between reduction of alpha(v) synthesis and osteoclast programmed death. In conclusion, this study provides novel insights into the use of alpha(v) antisense ODN as an efficacious mechanism for blocking osteoclast function and underscores for the first time the involvement of integrins in bone cell apoptosis. In vivo studies may verify potential application of this ODN as alternative therapy for bone diseases.