ABSTRACT NUMBER: ESOC2026A2029 MODELING ESAM-ASSOCIATED PERINATAL HEMORRHAGIC STROKE USING PATIENT-SPECIFIC IPSC-DERIVED ENDOTHELIAL CELLS

Abstract Background and aims Perinatal stroke comprises cerebrovascular events arising during fetal or neonatal life, often causing intracranial hemorrhage and long-term neurological deficits. Although multifactorial, rare monogenic variants affecting vascular integrity and blood–brain barrier (BBB) function are increasingly recognized. Biallelic loss-of-function mutations in ESAM, encoding an endothelial tight-junction protein, were recently identified as a novel cause of fetal intracranial hemorrhage. We aimed to establish a patient-specific in vitro BBB model to determine how ESAM deficiency alters endothelial function. Methods Dermal fibroblasts from two sisters with prenatal intraventricular hemorrhage carrying the homozygous ESAM c.287del (p.Pro96Leufs*33) variant were reprogrammed into human iPSCs using a Sendai virus system. Six lines were validated for pluripotency, genomic integrity, and variant presence. Patient-derived iPSCs were differentiated into endothelial cells (hiPSC-ECs) to model BBB function. Endothelial tube formation, permeability, and transendothelial electrical resistance (TEER) were assessed, alongside expression of ESAM and tight-junction proteins (claudin-5, ZO-1, occludin) by Western blotting and immunofluorescence. Results Patient-specific hiPSC lines retained pluripotency and genomic stability, and differentiated successfully into endothelial cells expressing canonical markers. ESAM-mutant hiPSC-ECs lacked ESAM protein and showed altered tight-junction protein profiles, impaired tube formation, increased permeability, and reduced TEER compared with controls. Conclusions This first patient-derived hiPSC-EC model of ESAM-associated perinatal hemorrhagic stroke enables mechanistic studies of endothelial dysfunction and provides a platform to explore targeted strategies for restoring BBB integrity. Conflict of interest Garcia-Martínez T: nothing to disclose. Gornatti DG: nothing to disclose. Bugalló A: nothing to disclose. Fortunato IC: nothing to disclose. Gomila S: nothing to disclose. Ortiz M: nothing to disclose. Otero-Rial N: nothing to disclose. Heine-Suñer D: nothing to disclose. Campos F: nothing to disclose. Vives-Bauzà C: nothing to disclose.