Amnion as a surrogate tissue reporter of the effects of maternal preeclampsia on the fetus.

BACKGROUND: Preeclampsia, traditionally characterized by high blood pressure and proteinuria, is a common pregnancy complication, which affects 2-8 % of all pregnancies. Although children born to women with preeclampsia have a higher risk of hypertension in later life, the mechanism of this increased risk is unknown. DNA methylation is an epigenetic modification that has been studied as a mediator of cellular memory of adverse exposures in utero. Since each cell type in the body has a unique DNA profile, cell subtype composition is a major confounding factor in studies of tissues with heterogeneous cell types. The best way to avoid this confounding effect is by using purified cell types. However, using purified cell types in large cohort translational studies is difficult. The amnion, the inner layer of the fetal membranes of the placenta, is derived from the epiblast and consists of two cell types, which are easy to isolate from the delivered placenta. In this study, we demonstrate the value of using amnion samples for DNA methylation studies, revealing distinctive patterns between fetuses exposed to proteinuria or hypertension and fetuses from normal pregnancies. RESULTS: We performed a genome-wide DNA methylation analysis, HpaII tiny fragment Enrichment by Ligation-mediated PCR (HELP)-tagging, on 62 amnion samples from the placentas of uncomplicated, normal pregnancies and from those with complications of preeclampsia or hypertension. Using a regression model approach, we found 123, 85, and 99 loci with high-confidence hypertension-associated, proteinuria-associated, and hypertension- and proteinuria-associated DNA methylation changes, respectively. A gene ontology analysis showed DNA methylation changes to be selecting genes with different biological processes in exposure status. We also found that these differentially methylated regions overlap loci previously reported as differentially methylated regions in preeclampsia. CONCLUSIONS: Our findings support prior observations that preeclampsia is associated with changes of DNA methylation near genes that have previously been found to be dysregulated in preeclampsia. We propose that amniotic membranes represent a valuable surrogate fetal tissue on which to perform epigenome-wide association studies of adverse intrauterine conditions.

The clinical and molecular significance of C4d staining patterns in renal allografts.

BACKGROUND: We investigated the clinical and molecular significance of minimal peritubular capillary (PTC) and isolated glomerular C4d+ staining using microarrays. METHODS: Two hundred fifty-five clinically indicated transplant biopsies were included in the analyses. C4d staining was performed on paraffin sections using a polyclonal rabbit anti-C4d antibody. Gene expression profiles in a subset of patients were studied using Affymetrix HuGene 1.0ST arrays. RESULTS: Immunohistochemistry for C4d of 255 biopsies showed 51% C4d negative, 4% minimal PTC C4d+, 15% focal or diffuse PTC C4d+, and 31% isolated glomerular C4d+ biopsies. Patients with minimal and focal/diffuse PTC C4d+ staining had higher frequency of donor-specific anti-HLA antibodies (DSA) (67% and 82%) and antibody mediated rejection (AMR) (66% and 89%) when compared with C4d-negative biopsies (25% and 19%, respectively) (P<0.001). The glomerulitis, interstitial inflammation, and peritubular capillaritis scores were also significantly higher in minimal (0.88, 1.25, and 1.5) and focal/diffuse PTC C4d+ biopsies (0.65, 1.41, and 1.5), compared with C4d-negative biopsies (0.25, 079, and 0.34), respectively. There were no differences in the DSA frequency, AMR rate, or Banff scores between isolated glomerular C4d+ and C4d-negative patients. Although both minimal and focal/diffuse C4d+ biopsies showed increased expression of genes related to the immune response, interferon-gamma and rejection-induced, cytotoxic T cell and constitutive macrophage-associated pathogenesis-based transcripts, there was no activation of immune-response-related genes in isolated glomerular C4d+ biopsies. CONCLUSION: Minimal PTC C4d+ staining but not isolated glomerular C4d+ staining is associated with AMR, circulating DSAs and immune-response-related gene activation.