The effect of anticardiolipin IgG on extravillous trophoblast differentiation

Abstract

Objective: The role of the antiphospholipid antibody syndrome (APS) as being strongly associated with recurrent pregnancy loss is well established. Proposed theories on mechanism include placental microthromboses and infarction, which are not universally found on histological examination. The hypothesis to be tested is that extravillous trophoblast (EVT) differentiation is impaired in women with APS versus a fertile parous control group.Design, Materials and Methods: Blood was taken from women with recurrent miscarriages and APS with anticardiolipin (aCL) IgG >20 IU/L and was subjected to affinity purification to extract the immunoglobulin (Ig) G fraction. IgG was also purified from an APS negative multiparous control group. Primary EVT was isolated from term placentae by enzyme digestion of chorionic strips and cultured with the aCL from affected women and an equivalent total IgG from controls, then stained using immunohistochemistry with cytokeratin 7. Trophoblast differentiation was measured by counting multinucleate giant cell formation.Results: There was significant inhibition of extravillous trophoblast differentiation (p<0.0001) with the APS patients, but not the control women. This was demonstrated from 50μg/ml of anticardiolipin IgG and was maximal at 48 hour cell culture.Conclusion: Patient derived, affinity purified aCL caused inhibition of trophoblast differentiation in our in vitro model of primary extravillous trophoblast differentiation. aCL may contribute to pregnancy loss by inhibiting EVT biology at the time of early implantation and placentation. Objective: The role of the antiphospholipid antibody syndrome (APS) as being strongly associated with recurrent pregnancy loss is well established. Proposed theories on mechanism include placental microthromboses and infarction, which are not universally found on histological examination. The hypothesis to be tested is that extravillous trophoblast (EVT) differentiation is impaired in women with APS versus a fertile parous control group. Design, Materials and Methods: Blood was taken from women with recurrent miscarriages and APS with anticardiolipin (aCL) IgG >20 IU/L and was subjected to affinity purification to extract the immunoglobulin (Ig) G fraction. IgG was also purified from an APS negative multiparous control group. Primary EVT was isolated from term placentae by enzyme digestion of chorionic strips and cultured with the aCL from affected women and an equivalent total IgG from controls, then stained using immunohistochemistry with cytokeratin 7. Trophoblast differentiation was measured by counting multinucleate giant cell formation. Results: There was significant inhibition of extravillous trophoblast differentiation (p<0.0001) with the APS patients, but not the control women. This was demonstrated from 50μg/ml of anticardiolipin IgG and was maximal at 48 hour cell culture. Conclusion: Patient derived, affinity purified aCL caused inhibition of trophoblast differentiation in our in vitro model of primary extravillous trophoblast differentiation. aCL may contribute to pregnancy loss by inhibiting EVT biology at the time of early implantation and placentation.