Objective:  Leukocytes arriving to choriodecidua during labor are capable to secrete cytokines and collagenases that may play a role in extracellular matrix degradation leading to the rupture of amniochorion. The aim of this work was to study the role of amniochorion in the active recruitment of leukocytes through production of specific chemokines during labor.

Methods:  Amniochorion explants were obtained from women at term with spontaneous labor (n = 4) and subjected to cesarean section without labor (n = 4). Explant cultures were carried out during 24 hr and a homogenate including the culture media was made after this period. Cell free extracts were tested in Boyden chambers for chemotaxis using leukocytes from maternal blood obtained from women with (n = 2) and without labor (n = 2). Attracted cells were analyzed by flow cytometry for count and immunophenotype. Chemokines were identified in the extracts using a commercial chemiarray.

Results:  All tested amniochorion extracts induced chemotaxis for leukocytes; however, those from labor tissues induced a higher chemotactic activity than the correspondent non-in-labor tissues (= 0.003). Chemotactic effect was higher over leukocytes from labor women (= 0.001). More than 80% of the attracted cells were polymorphonuclear cells in all cases. IL-8 was the main chemokine found in all extracts; however its concentration was increased in extracts from labor.

Conclusions:  Fetal membranes induced chemotaxis for leukocytes and this condition is enhanced by the presence of labor. Amniochorion under active labor secretes IL-8 which induces a preferential chemotaxis for polymorphonuclears. Infiltration of these cells in choriodecidua during labor may play a role in the amniochorion degradation associated to rupture.