Random sequence phosphorothioate oligonucleotides evoke dramatic phenotypic alterations in cardiac myocyte cultures

Cardiac myocytes displayed modest and uncoordinated contractile activity regardless of whether they are cultured in the presence or absence of unmodified random sequence oligonucleotides (oligos), as expected. Much to our surprise, however, when cardiac myocytes were cultured in the presence of random sequence phosphorothioate (PS) oligos, they reorganized into cablelike aggregates and displayed surging and coordinated contractile activity. Consistent with these observations, photobleaching experiments revealed that gap junction conductivity between affected cardiac myocytes was enhanced fourfold relative to control cultures. Furthermore, whereas atrial natriuretic factor (ANF) gene expression was induced in control cultures relative to intact hearts, this aberrant expression was selectively repressed in response to PS oligos. As PS oligos appear to mitigate deleterious effects that result from the proteolytic dispersal or culturing of cardiac myocytes or both, we suggest that these may useful cell culture reagents. It is interesting to contemplate whether cardiac myocytes might also be responsive to PS oligos within intact hearts, as this issue has potential clinical significance.