Integrins and reproductive physiology: Expression and modulation in fertilization, embryogenesis, and implantation

Objective: To review the available information regarding the role of integrins in reproductive physiology and to discuss their potential clinical implications. Design: Studies that specifically relate to the expression and modulation of integrins in fertilization, embryogenesis, and implantation were identified through the literature and Medline searches. Result(s): Integrins are a class of adhesion molecules that participate in cell-to-cell and cell-to-substratum interactions and are present on essentially all human cells. All mammalian eggs express integrins at their surface, and the integrin α₆β₁ serves as a sperm receptor that mediates sperm-egg binding. In addition, certain integrin moieties appear to be regulated within the cycling endometrium. Specifically, the expression of β₁ integrins in the early proliferative phase is restricted to the glandular epithelium, whereas stromal cells also express β₁ integrins in the midsecretory phase. The expression of β₁ integrins increases at the time of implantation and remains elevated in the decidua during early pregnancy. A disruption of integrin expression is associated with certain types of infertility in women. The apical surface of the mural trophectoderm does indeed possess functional integrins, and trophoblast interactions with extracellular matrix proteins largely depend on the integrin family of adhesion receptors. Conclusion(s): Integrins play particularly important roles in both fertilization and embryogenesis, including the process of implantation.