COLLAGEN CHANGES IN RAT CERVIX IN PREGNANCY POLARIZED-LIGHT MICROSCOPIC AND ELECTRON-MICROSCOPIC STUDIES

The structural arrangement of collagen fibers in cervical ripening was studied in normal pregnant rats by picrosirlus red staining and polar ized light microscopy, The macromolecular arrangement of collagen fibe rs in the cervices of nonpregnant controls and in firm and rigid cervi ces of rats in early pregnancy (1-10 days of gestation) were optically anisotropic and had birefringence and a positive sign of elongation w hen examined by polarized tight microscopy. The findings indicated tha t the structure of these collagen fibers was assembled from well-packe d parallel collagen molecules. The direction of fibrous formation was arranged with regularity. In contrast, most of the collagen fibers in the soft cervices were optically Isotropic, The fibers were fragmented and had a structure with discontinuous birefringence. Disarray and di sorientation of the collagen fibers was found in the soft cervices. Th ese collagen fibers changed their direction of formation. The disorgan ization of these collagen fibers might have a major impact on weakenin g the tensile strength of the cervix. Thus, we conclude that the proce sses of rearrangement of collagen fibers might be an important process in the cervical ripening. Electron microscopic studies suggest that i n the focal hydrolytic processes of collagen and other matrix componen ts degradation by lysosomal and phagosomal vesicles were associated wi th atrophic smooth muscle cells and fibroblasts of the cervices. Hydro lases released from lysosomes from these apoptotic cells may presumabl y be one of the processes In the remodeling of collagen structure.