Modifications in the Histology and Immunolocalization of Alpha 1 Integrins in the Cervix of Pregnant Rats in Preparation for Parturition

Dystocia, or difficult labor, is one of the primary indications for cesarean sections and complications with cervical softening contribute significantly to the number suffering with dystocia. The cervix must change shape, size, and histological properties to serve as the birthing canal, and these cervical changes associated with late pregnancy are influenced by the hormone relaxin. In the current study histological changes were demonstrated in the cervical connective tissue, collagen fibers became more loosely dispersed, especially near the lumen and adjacent to smooth muscle, in the intact controls and ovariectomized rats treated with progesterone, estrogen, and relaxin (OPER) when compared to ovariectomized rats treated with progesterone and estrogen (OPE). In the epithelial tissue, cell density and the number of vacuoles and luminal involutions increased with relaxin. The sites of cell surface receptors, the ± 1 integrins were also isolated via immunocytochemistry. The control rats displayed ± 1 integrins either at the basement membrane or all along the surface of epithelial cells. OPER-treatment resulted in ± 1 integrins at the basement membrane alone or to the apical surface as well, with the latter being similar to the OPE groups. The ± 1 integrins are capable of binding to collagen Type IV and laminin, constituents of basement membranes. The ± 1 integrins may provide a role in the attachment of the luminal epithelium to the connective tissue of the cervical stroma. The integrin sites may be a response to fluctuating levels of collagen fragments found in the cervical secretions within the lumen. Significant numbers of ± 1 integrins were found in the connective tissue to facilitate the interactions of fibroblasts and collagen. It is proposed ± 1 integrins are necessary in the rat cervix for proper cervical softening