Hyperexpression of Inflammatory Genes in Placental Tissue in Patients with Hemoglobin SC Disease

Introduction: Pregnant women with sickle cell disease (SCD) are at higher risk of obstetrical complications, such as preeclampsia and preterm delivery. The placental circulation is susceptible to vaso-occlusion, which may contribute to fibrosis, necrosis and infarction of the placental villi. Restricted uteroplacental circulation is associated with low birth weight and fetal growth restriction. The mechanisms by which SCD affects placental physiology are largely unknown, and the chronic inflammatory state may be involved in this pathological process. The aim of this study was to evaluate the expression of mediators of inflammatory response in the placenta of pregnant women with SCD.

Methods: This is an ongoing case control study that has recruited 4 pregnant patients with hemoglobin SC disease and 4 healthy control pregnant women paired for gestational age and route of delivery. Placental tissue was collected for total RNA extraction and synthesis of cDNA. Samples were run on a qPCR Array (Inflammatory Response and Autoimmunity RT² Profiler, Qiagen), which includes 84 genes. Gene expression levels were normalized to housekeeping genes (ACTB, B2M, and RPLP0), and will be further validated by RT-qPCR.

Results: Two patients underwent cesarean delivery and one patient delivered preterm. The analysis of placental gene expression showed that 16 genes were upregulated. The top 5 most upregulated genes were CCL24 (18.1 fold), TLR9 (8.6 fold), inducible nitric oxide synthase NOS2 (6.8 fold), IL17A (5.4 fold), and CCL16 (4.8 fold). Upregulated genes also included other chemokines and their receptors (CCL21, CCL22, CXCL3, and CCR7), interleukins (IL1RAP, IL5, and IL9), another toll-like receptor (TLR3), transcription factor BCL6, CD40 ligand (CD40LG), and kininogen 1 (KNG1). Interestingly, the two genes found to be downregulated were CRP (C reactive protein) and IFNG (interferon gamma).

Conclusion: This is the first study of differential gene expression in placenta of patients with SCD. Despite patients with hemoglobin SC disease being clinically less severe than homozygous sickle cell anemia, we have found that placental tissue in this subset of patients displays increased expression of several genes involved in inflammatory response. Our data support local inflammatory changes in the placenta of these patients that might explain the development of complications in SCD pregnancies. Although the association between obstetric complications and SCD has been long described, our data should contribute to better define the mechanisms affecting the placental physiology that lead to complications, such as preeclampsia.