Pathomorphologic and immunohistochemical study on the devastation of rat embryos by antiphospholipid antibody positive serum

Problem: While relying on previous publications, our aim was to examine the morphologic changes, induced in early rat embryos by intra-uterine exposure to the low-molecular weight fraction of boiled human serum containing antiphospholipid antibodies (APLA) that had been obtained from women with antiphospholipid syndrome (APS). Method of study: Human APLA-positive sera were pooled, boiled, centrifuged and separated by ultrafiltration. The molecular weight fraction lower than 30 kDa was used for the experiments. One hundred and fifty microlitres was injected into one uterine horn of 12 pregnant rats, 5 or 6 days after fertilization, while similarly prepared normal human serum or saline were injected into the contralateral horn. The rats were subsequently sacrificed. Serial sections, obtained from all uterine horns, were stained histologically and immunohistochemically. Normal embryos developed in the control uterine horns, while embryos in the experimental horns were destroyed rapidly. Results: Signs of apoptosis appeared 2 hr following the injection, and 4hr later all the embryonic cells were apoptotically destroyed. There was only partial damage to cytotrophoblasts and intermediate trophoblasts. Conclusion: These findings support the existence of a novel factor in the APLA-positive serum, causing a detrimental effect to the conceptus, without any relation to the antiphospholipid antibodies.