Mitochondria-associated endoplasmic reticulum membrane (MAM)-associated calpains system in preeclampsia

Preeclampsia (PE) is a multisystem disorder characterized primarily by hypertension and proteinuria after 20 weeks of gestation, significantly impacting maternal and fetal health. The etiology remains unclear, but it is primarily attributed to placental dysfunction leading to systemic vascular endothelial damage and inflammatory responses. Mitochondria-associated endoplasmic reticulum membranes (MAMs) influence mitochondrial and endoplasmic reticulum (ER) function by regulating calcium homeostasis, autophagy, and apoptosis. In PE, mitochondrial dysfunction and ER stress have been widely observed. However, detailed investigations into the specific mechanisms and roles of MAMs in PE remain limited. Thus, this study aimed to investigate how MAM-associated biomarkers affect PE.

The study involved 31 women with early-onset PE, 30 with late-onset PE, and 54 healthy controls matched for gestational age. Placental morphology and MAM structure in both PE and control tissues were assessed using Hematoxylin-Eosin (HE) staining and electron microscopy (EM). Bioinformatics analysis of Gene Expression Omnibus (GEO) datasets (GSE190971, GSE24129) identified MAMs-related genes (MAMs-RGs) and candidate biomarkers through weighted gene co-expression network analysis (WGCNA), machine learning algorithms (Least absolute shrinkage and selection operator, Support Vector Machine Recursive Feature Elimination), and functional enrichment. Real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) was used to validate biomarker expression in PE placentas. Calpain-1, calpain-2, and calpastatin expression levels were evaluated using Immunofluorescence and Western blotting techniques.

The results showed early-onset PE (EOPE) had higher abnormal pregnancy history, fetal growth restriction, systolic/diastolic ratio, and lower placental growth factor than late-onset PE (LOPE) and controls. Both PE types had fewer placental villi, but EOPE showed more severe ultrastructural changes in mitochondria-associated membranes. Bioinformatics identified CAST as potential MAM biomarkers, and its expression was significantly downregulated in PE samples (P < 0.01). Immunofluorescence and Western blotting showed calpain-1 and calpastatin were decreased in EOPE, while calpain-2 was reduced in both PE types, with calpain-1 increased in LOPE.

EOPE is characterized by placental dysfunction, with increased MAM contact observed in PE placentas.The calpain-calpastatin system may be involved in placental dysfunction in PE, with calpain-2 downregulation observed in both PE subtypes and calpain-1 dysregulation differing between EOPE and LOPE. These changes are accompanied by increased MAM contacts in PE placentas, suggesting a potential link between MAM structural abnormalities and calpain system dysregulation, with calpain-2 levels potentially associated with disease severity.