Acyl-CoA:lysocardiolipin acyltransferase (Lycat): a potent pathogenic factor in antiphospholipid syndrome (APS)-related recurrent pregnancy failure

Abstract

To validate a novel model system to study the pathogenesis of recurrent miscarriages in APS patients. Experimental animal study. Elevated titers of antiphospholipid antibodies (aPL) have a close association with many obstetric disorders. Cadiolipin (CL), a major phospholipid of mitochondria, regulates membrane permeability and potential. Remodeling enzyme Lycat is required for both CL maturation and repair of damaged acyl chains. At present, APS animal models were generally created by immunization of exogenous antigens. This study presents the first genetic model in which elevated Lycat leads to a drastic rise of aPL, concomitant with a high rate of in utero fetal loss. Mice over-expressing Lycat were generated by BAC transgenesis (Tg). Fertility were compared between Tg and WT mice. Mutant implantation sites were sectioned for histology, anti-phospho-H3 IF, TUNEL and in situ hybridization. Altered global gene expression of the mutant conceptus was first tested by NextGENe RNA-seq technology, followed by Q-PCR. Serum aPL were tested by ELISA. At least 3 samples were included in each assay for each genotype. Unpaired student's t-test was performed between WT and Tg groups. All Tg female mice showed elevated aPL, whose levels are positively correlated to the severity of fetal loss. Pregnant Tg females produced fewer pups than the controls (Tg, 2.3±0.2, v.s. WT, 8.5±1.4; p<0.01). Degenerating conceptus revealed faulty extraembryonic structures involving trophoblast giant cells, chorion and amnion. As a result, the embryos developmentally arrested by E7.5. Absence of EOMES, Hand1, PL1 and Tpbp indicates defective trophoblast differentiation; while altered expression of Gas1 and Foxh1 suggests mis-instructed embryogenesis. Decreased synthesis of hemoglobins by decidual cells indicates severe oxygen starvation in the mutants. Pathogenic effects of elevated Lycat are multifold, in which oxygen homeostasis, trophoblast differentiation and embryo growth are all affected.