The effect of prostaglandins on the lysosomal function in the cervix uteri

Local or systemic prostaglandin (PG) administration leads to the known softening and dilatation of the cervix uteri. Lysosomal enzymes are involved in connective tissue degradation. The question arises whether the effect of PG on the cervix uteri is mediated by lysosomes. Five pregnant women (volunteers after informed consent) in the first trimester received 500 micrograms of PGE2-derivative (Nalador) i.m. at 12 and 8 h before termination by curettage. Five pregnant women without PG-treatment served as controls. Small biopsies were obtained from the endocervical canal and were immediately immersed in cold 2.5% glutaraldehyde and after further preparations examined under a Zeiss electron microscope 9S-2. A second portion of tissue was sliced and prepared for histochemical analysis of the acid phosphatase on lysosomes. Examination of the ultrastructure of the cervix uteri showed vesicles in the extracellular matrix. These were surrounded by a single membrane and contained either fine granular material of myelin-like whorls of membranes. These vesicles lay between collagen fibers, showed the reaction product of acid phosphatase and were often surrounded by an electron-lucent halo. We conclude that these matrix vesicles were "matrix lysosomes" extruded from the cervical myo-fibrocytes into the extracellular space as a result of the PG-E2-administration. Here they are not under cellular control and can initiate the proteolytic degradation of connective tissue. This might be the crucial step in cervical dilatation which, on ultrastructural examination, can be seen as decreasing electron density of the extracellular ground substance near the matrix lysosomes. The relationship between PGE2 and collagenase production is generally accepted. If one believes that lysosomal cathepsin D and cathepsin B act synergistically with collagenase, it can be assumed that PGE2 is involved in a lysosomal degradation of the connective tissue. The morphological sign of this occurrence is the release of matrix lysosomes by PGE2 as described in the present study. Extracellular lysosomes and their physiological significance in cervical function are discussed in detail.