EFFECTS OF BETA-1-INTEGRIN ANTISENSE PHOSPHOROTHIOATE-MODIFIED OLIGONUCLEOTIDE ON MYOBLAST BEHAVIOR IN-VITRO

Myoblasts gene-engineered in vitro and then injected in vivo are safe, efficient options for gene therapy. While isolation of satellite cell s is routinely achieved, their proliferation potential in vitro remain s a limiting factor for cell transplantation under clinical conditions . We have studied the role of reversible inhibition of gene expression by antisense oligonucleotides on the proliferation of the myogenic ce lls. Addition of antisense oligonucleotides to myoblast cultures has b een used to inhibit specifically the expression of the beta 1-integrin subunit gene. Here we show that the effects of multiple pulses of a p hosphorothioate oligodeoxinucleotide antisense on the attachment to su bstrata and on the proliferation of myoblasts are dose-dependent. The addition of antisense to rat myoblasts caused rounding up of the cells and most of the cells became detached after several days in culture. A single pulse did not show any consistent effect, while in the presen ce of continuously administered antisense, the relative numbers of myo blasts in the treated muscle culture increased. We have no evidence of inhibition of myoblast fusion under these conditions. On the other ha nd, [H-3]-TdR incorporation, total DNA and total number of cells decre ased in antisense-treated cultures thus demonstrating an inhibitory ef fect of the phosphorothioate oligonucleotides on DNA synthesis. These side-effects could be overcome by substituting the phosphorothioate by unmodified oligonucleotides, so decreasing the half-life of the antis ense, but also its toxicity. The overall results suggest a potential r ole of integrin antisense strategy in modulating the potential of myob lasts to proliferate.