Patient-Derived Hepatocyte-Like Cells Reveal Secretion Defects Caused by SERPING1 Variants in Hereditary Angioedema
Background: A hepatocyte model preserving patients’ genetic context
Hepatocyte-like cells (HLCs) generated from patient-derived stem cells reproduced protein secretion defects caused by SERPING1 variants in hereditary angioedema (HAE). The researchers also found that correcting the variants in cells from two patients restored gene expression and protein secretion, while introducing the same variants into healthy control cells produced defects. Published in Allergy, the study provides an experimental basis for comparing the effects of patient-specific variants in a human hepatocyte environment.
SERPING1 encodes C1 esterase inhibitor (C1INH), a plasma protease inhibitor. When C1INH is deficient or does not function properly, excessive kallikrein activity and bradykinin production increase vascular permeability and cause swelling. The liver’s role as the main source of circulating C1INH provided the rationale for this model.
Experiments that overexpress variant genes in existing cancer cell lines have difficulty preserving patients’ own gene-regulatory environment, and overexpression itself may exaggerate protein accumulation. The researchers therefore designed the study to retain each patient’s genetic background and compare cells before and after variant correction.
Key findings: Shared reduction in secretion, with differences among variants
The study included four patients with type 1 HAE and low C1INH concentrations, along with four healthy controls. The patients carried, respectively, a single-nucleotide substitution, a one-base duplication, a two-base deletion, or a large deletion encompassing exons 1–4. The researchers reprogrammed erythroid-lineage cells expanded from peripheral blood mononuclear cells into expanded potential stem cells (EPSCs). They then differentiated the cells into HLCs over about 20 days and confirmed hepatocyte functions, including albumin secretion and urea synthesis.
Analyses using quantitative reverse-transcription polymerase chain reaction (qRT-PCR), immunoblotting, immunofluorescence, and bulk RNA sequencing showed reduced C1INH secretion in HLCs from all patients. The intracellular patterns differed, however. HLCs from P1–P3 showed no marked C1INH accumulation, whereas those from P4, who carried the large deletion, showed intracellular accumulation alongside reduced hepatocyte maturation. The precise cause of the accumulation remains unknown.
Causal testing was limited to the variants in P1 and P2. After CRISPR/Cas9 gene editing corrected the variants in patient EPSCs, SERPING1 messenger RNA (mRNA) expression and C1INH secretion recovered in the differentiated HLCs. Conversely, introducing the same variants into healthy control EPSCs reduced SERPING1 mRNA in HLCs by about 50% compared with controls without the introduced variants and reproduced the secretion defect. This figure of about 50% describes a change in gene expression in cells; it should be distinguished from patients’ blood concentrations or a treatment effect.
Meaning and outlook: A basis for variant-function testing, with limitations
The findings point to the possibility that the same variant can act differently depending on genetic background. SERPING1 expression in cells corrected for the P1 variant did not reach the level in healthy controls. When the same variant was introduced into control cells, allelic expression and exon-skipping patterns also differed from those in the original patient cells. This observation suggests that a single variant may not explain all of a patient’s molecular characteristics; it does not establish the model’s ability to predict clinical severity.
The results provide a cell-level proof of concept for direct SERPING1 correction. The analysis used cell lines from four patients, and gene expression in HLCs differed from that in primary human hepatocytes. Systemic responses—including vascular endothelial responses, immune signaling, and kallikrein–kinin system activity—were outside the model. Before this approach could advance as a treatment strategy, its reproducibility across a broader range of variants, in vivo delivery efficiency, long-term safety, and scalability would need to be assessed.
The study’s methods and results are available in the full paper.
Hereditary angioedema (HAE) with C1 esterase inhibitor (C1INH) deficiency is caused by pathogenic SERPING1 mutations that disrupt production of the plasma protease inhibitor C1INH. However, the molecular mechanisms and consequences of patient-specific mutations remain poorly understood due to the lack of physiologically relevant human models. Here, we established a personalized, isogenic, stem-cell-derived hepatocyte platform to investigate the underlying mutation-specific mechanisms of HAE. Specifically, peripheral blood mononuclear cell (PBMC)-expanded erythroblasts from four representative HAE-C1INH-Type1 patients containing distinct point, insertion, deletion, or large fragment SERPING1 mutations were reprogrammed into expanded potential stem cells (EPSCs) and further differentiated into hepatocyte-like cells (HLCs). These HLCs exhibited appropriate transcriptional transitions, mature hepatic features, and C1INH secretion comparable to that observed in human plasma. All patient-derived HLCs demonstrated impaired C1INH secretion with mutation-specific differences in both SERPING1 transcription and intracellular accumulation. Moreover, to verify that the mutations directly drive the phenotype, we performed CRISPR/Cas9-mediated genome repair, which restored SERPING1 mRNA expression and C1INH secretion. Conversely, identical patient mutations installed into healthy EPSCs showed the same transcriptional and secretory defects, confirming sufficiency. Collectively, we have established a robust human hepatocyte model that accurately recapitulates key hepatocyte-specific aspects of HAE pathophysiology and provides a scalable foundation for investigation of future precision therapies.
The platform’s practical value lies in enabling comparisons of the defects a patient’s variant causes in hepatocytes. For example, researchers can analyze patient-derived HLCs alongside variant-corrected HLCs with the same genetic background to assess whether reduced SERPING1 expression and impaired C1INH secretion are linked to that variant. The platform may also be useful in experiments investigating whether candidate treatment strategies restore these measures.
The study did not demonstrate drug-screening performance or improvement in patients’ symptoms. The platform may support functional interpretation of uncertain variants and research into personalized treatments, but it does not replace current diagnosis based on C1INH concentration and function. Whether restored secretion in cells leads to clinical benefit remains a separate question requiring investigation.