Guinea pig spermatozoa adhesion to an immobilized fibronectin matrix alters their physiology and increases their survival

Isthmus is the region of the oviduct considered a reservoir for spermatozoa, where they are retained and released synchronously with ovulation. Integrins mediate this interaction, and it is suggested that they regulate the viability and capacitation of spermatozoa. Spermatozoa retained in the oviductal epithelial cells show specific characteristics: normal morphology, intact acrosome and plasma membrane, no DNA fragmentation, and low levels of intracellular Ca2+, and protein phosphorylation at Tyr. This work aimed to define spermatozoa's ability to adhere to an immobilized fibronectin matrix and its effects on their viability and capacitation. We found that guinea pig spermatozoa showed a high affinity for adhering to an immobilized fibronectin matrix but not to those made up of type 1 collagen or laminin. This interaction was mediated by integrins that recognize the RGD domain. Spermatozoa adhered to an immobilized fibronectin matrix were maintained in a state of low capacitation: low levels of intracellular concentration of Ca2+, protein phosphorylation in Tyr, and F-actin. Also, spermatozoa kept their plasma membrane and acrosome intact, flagellum beating and showed low activation of caspases 3/7. The spermatozoa adhered to the immobilized fibronectin matrix, gradually detached, forming rosettes and did not undergo a spontaneous acrosomal reaction but were capable of experiencing a progesterone-induced acrosomal reaction. In conclusion, the adhesion of spermatozoa to an immobilized fibronectin matrix alters the physiology of the spermatozoa, keeping them in a steady state of capacitation, increasing their viability in a similar way to what was reported for spermatozoa adhered to oviductal epithelial cells.