comet assay from frozen tissue?

I am trying to prepare comet assay from frozen cardiac muscle tissue. However, this tissue was not cryopreserved but stored at -80.  Is it possible to get some results in comet assay? I have problem with obtaining the cells from that tissue, also. Homogenization  results in cells damage and collagenase method doesn`t work. Could you, please help me. What other techniques can be used for DNA damage detection in frozen tissue???