Image analysis and ultrastructural detection of DNA strand breaks in human endometrium by in situ end-labeling techniques

Changes of DNA fragmentation in human endometrial glandular cells throughout the menstrual cycle were studied via in situ end labeling of DNA strand breaks (ISEL techniques) using light microscopy (LM) and transmission electron microscopy (TEM). Moreover, image analysis for quantitative changes of DNA strand breaks was performed on a computer using the NIH Image program. Digoxigenin-labeled nucleotides were used; incorporation was demonstrated by immunoperoxidase staining on cryosections for LM and by immunogold staining on ultrathin sections of epoxy resin for TEM. This image analysis combined with ISEL/TEM techniques clearly demonstrated the increase of the labeling density for DNA strand breaks in the nuclei of the endometrial glandular cells at the late proliferative phase when the cells were still preserved morphologically (early proliferative phase: 23.4 +/- 9.1/mu m(2); late proliferative phase: 142.6 +/- 40.0/mu m(2)), and the most intense labeling density was seen in apoptotic bodies (325.4 +/- 166.1/mu m(2)). Therefore, the image analysis combined with ISEL/TEM techniques permits us to semi-quantify DNA strand breaks in nuclei, and it provides useful information as to the relation between the morphological changes of apoptotic cells and changes of the labeling density for DNA strand breaks in the nuclei.