Summary: Fetal placental macrophages reflect the state of fetal brain microglia, the resident immune cells critical for brain development. Maternal immune activation—driven by infections, obesity, metabolic inflammation, environmental exposures, or stress—can alter microglial programming in utero and increase the risk of neurodevelopmental disorders in offspring.
New research from Massachusetts General Hospital used mouse models to compare placental macrophages (Hofbauer cells) and fetal brain microglia at single-cell resolution and following maternal diet‑induced obesity. The study found shared transcriptional signatures between these two cell types and revealed notable sex differences: male fetuses showed a stronger adverse response to maternal obesity than females. These results suggest that placental macrophages available at birth could serve as accessible biomarkers of fetal brain immune programming and help identify infants at higher risk for later neurodevelopmental problems.
Key facts
- Placental macrophages (Hofbauer cells) and fetal brain microglia share developmental origins and similar gene-expression programs.
- Maternal immune activation—including metabolic inflammation from obesity—alters microglial and placental macrophage transcriptional profiles, potentially affecting neurodevelopment.
- Male fetuses appear more susceptible than females to the transcriptional and inflammatory effects of maternal obesity.
The study, published in Cell Reports and led by investigators at Massachusetts General Hospital, used lineage tracing and single-cell RNA sequencing (scRNA-seq) in a mouse model of maternal diet‑induced obesity. Lineage tracing confirmed a shared yolk-sac origin for fetal brain macrophages (microglia) and placental Hofbauer cells. scRNA-seq identified overlapping transcriptional programs under normal conditions and common alterations in response to maternal obesity.
Under maternal diet‑induced obesity, both fetal microglia and Hofbauer cells displayed dysregulated gene expression and increased neuroinflammatory signaling. The degree of dysregulation was greater in male placental macrophages and microglia, highlighting sex-specific vulnerability to maternal metabolic inflammation. When the investigators compared mouse data with published human datasets, they observed conserved gene-expression patterns in placental macrophages between species, suggesting potential clinical relevance.
Senior author Andrea Edlow, MD MSc, an associate professor of Obstetrics, Gynecology, and Reproductive Biology and Maternal‑Fetal Medicine specialist at Massachusetts General Hospital, emphasized the clinical potential: if Hofbauer cells can act as surrogate biomarkers for fetal microglial programming, clinicians could identify newborns at elevated risk from in utero immune‑activating exposures and consider targeted monitoring or early interventions during critical developmental windows.
Examples of immune‑activating exposures examined include bacterial and viral infections, metabolic inflammation due to obesity or diabetes, environmental toxins, and maternal stress. By focusing on placenta-derived cells that are readily accessible at birth, this approach could enable noninvasive screening for altered neuroimmune programming without directly sampling the fetal brain.
Funding: This research was supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development, the Robert and Donna Landreth Family Foundation, and the Charles Lafitte Foundation.
About this neurodevelopment research news
Author: McKenzie Ridings
Source: Mass General
Contact: McKenzie Ridings – Mass General
Image: Image credited to Neuroscience News
Original Research: Open access. “Hofbauer cells and fetal brain microglia share transcriptional profiles and responses to maternal diet-induced obesity” by Andrea Edlow et al., Cell Reports.
Abstract
Hofbauer cells and fetal brain microglia share transcriptional profiles and responses to maternal diet-induced obesity
Highlights
- Microglia and fetal placental macrophages (Hofbauer cells) originate from the yolk sac and share developmental lineage.
- Single-cell RNA sequencing reveals shared transcriptional programs and parallel responses to maternal obesity in both cell types.
- There are sex differences in how maternal obesity impacts Hofbauer cells and fetal microglia, with male cells showing greater dysregulation.
- Hofbauer cells collected at birth may serve as biomarkers reflecting the impact of maternal exposures on fetal brain microglial programming.
Summary
Maternal immune activation is linked to adverse neurodevelopmental outcomes in offspring, often mediated by in utero programming of microglia. Because microglia are inaccessible during development, identifying noninvasive biomarkers that mirror fetal brain microglial states could enable early screening and intervention.
Using lineage tracing and single-cell transcriptomics in a mouse model of maternal diet‑induced obesity, the investigators demonstrated overlapping ontogeny and transcriptional responses between fetal brain macrophages and placental Hofbauer cells. Cross‑species comparisons with human datasets revealed conserved placental macrophage signatures, supporting translational potential.
The study identified common gene‑expression changes and neuroinflammatory signals in both microglia and Hofbauer cells induced by maternal obesity, and it revealed sex-specific differences in these responses. The authors propose that placental Hofbauer cells, being easily accessible at birth, could provide a practical window into fetal brain immune programming and help identify infants at heightened risk for neurodevelopmental disorders, paving the way for potential early interventions.