The research, published recently in the prestigious journal Nature Communications, addresses the intricate mechanisms by which microglia, the brain’s resident immune cells, modulate neurogenesis in the adult hippocampus. This brain region is critically involved in learning and memory formation, and the authors’ findings spotlight how immune surveillance and signaling by microglia can directly influence the creation and integration of new neurons into existing neural circuits.

Yu (Agnes) Luo, PhD, the study’s corresponding author and a professor and vice chair for research at the Department of Molecular and Cellular Biosciences, emphasizes the vital importance of understanding adult neurogenesis not only for our fundamental grasp of brain function but also for its implications in neurodegenerative diseases and mood disorders. “Adult neurogenesis is fundamental for maintaining cognitive flexibility, mood regulation, and memory consolidation,” Luo explains. “Elucidating the cellular crosstalk that facilitates this process could lead to breakthroughs in therapies aimed at combating cognitive decline and neurological diseases.”

The debate over adult neurogenesis has been contentious, with early skepticism regarding whether new neurons are generated in the adult human brain at all. It was not until a seminal 2025 study published in the journal Science that definitive evidence demonstrated ongoing neurogenesis within the hippocampus in adult humans. Building on this foundational knowledge, Luo’s laboratory sought to untangle the regulatory factors that enable or inhibit this process.

Central to their discoveries is the identification of microglia as dynamic regulators of neurogenesis. These cells, historically viewed largely as immune sentinels responding to injury or disease, are now recognized for their nuanced roles in maintaining neural homeostasis. The study reveals that the activation state of microglia critically determines their impact on neural stem cells — either promoting or suppressing the generation of newborn neurons depending on microglial signaling pathways.

One of the study’s most significant innovations lies in deciphering the role of transforming growth factor-beta (TGF-beta) signaling within microglia. Activated microglia devoid of TGF-beta signaling were found to foster neurogenesis via a sophisticated molecular conversation with neural stem cells. This bidirectional communication, described technically as microglia-neural stem cell signaling crosstalk, orchestrates the balance between immune function and neural regeneration, suggesting potential targets for rejuvenating the aging brain.

Though the current investigations were conducted in animal models to manipulate and observe cellular interactions within controlled environments, efforts are underway to translate these insights into human biology. Luo is collaborating with Ziyuan Guo, PhD, from the Department of Pediatrics at the College of Medicine, whose expertise lies in engineering human central nervous system organoids that integrate microglia, serving as sophisticated platforms for studying human neurodevelopment and neurodegeneration in vitro.

The project further benefited from cutting-edge single-cell RNA sequencing techniques, executed in partnership with Krishna Roskin, PhD, at Cincinnati Children’s Hospital. This technology allowed the team to map gene expression profiles at an unprecedented resolution, illuminating specific cellular signaling networks at work within the neurogenic niche. Such granular data deepens our understanding of the cellular diversity and molecular dialogues underpinning brain plasticity.

Longer-term, this research holds promise for revolutionary therapies aiming to harness adult neurogenesis for cognitive rejuvenation, particularly in the context of aging and Alzheimer’s disease. Joshua Peter, a lead author and former graduate student of the Luo lab, articulates this vision: “By understanding and potentially enhancing neurogenesis, we hope to mitigate cognitive decline and promote healthier brain aging, opening new therapeutic windows for Alzheimer’s and related disorders.”

The technology prowess gained through this research has also equipped emerging scientists like Peter and Kierra Ware, another Luo lab alumnus, with valuable expertise in translational neurobiology and biomedical research, ensuring a pipeline of innovators committed to pushing the frontiers of neuroscience.

Collaboration across institutions and disciplines bolsters the robustness of these findings. Contributors include Shane Liddelow from NYU Grossman School of Medicine, experts from the UChicago Medicine and NorthShore University HealthSystem partnership, as well as researchers from the German Center for Neurodegenerative Diseases. This international and interdisciplinary teamwork underscores the global effort to unveil the mysteries of the adult brain’s regenerative potential.

Taken together, these discoveries affirm the profound plasticity of the adult brain and redefine the roles of immune cells beyond mere defense—positioning them as key architects in neural regeneration. As research advances, the modulation of microglia signaling pathways stands as a promising frontier, potentially leading to innovative treatments that will transform the management of cognitive impairment and neurodegeneration.

Subject of Research: Animals
Article Title: Immune cells regulate adult hippocampal neurogenesis via TGF-beta signaling pathways
News Publication Date: 9-Feb-2026
Web References: https://link.mediaoutreach.meltwater.com/ls/click?upn=u001.Y87PxWj8gU0RPezaehlkQRumQp8DAV-2BIv5WY6NyDcQqHN8Z-2BdpeZskdMyt8HlyJw0QkquyffdCOBWlJdDryvEg-3D-3DXBNn_3u918C8n0AVqyOWIFY55-2FDiESquxCTmQYlctRdeNLb0NLrGGlSyBNqKdXsxFShdPePkdbvrsJ0pQpH1-2FRvZ2L95YGU6QKpJgQfrPVXO647nQC99gwtVEOZ-2FGItgrDTgSauOD-2FrgqIijCJX6XZlugVfwPREO8eBEE01y7TCf-2Fh7S3Z3bQC2KsBt8lFSGTB6z3HB789O9BMXX3-2BGCmi-2FTuesenNNNUtHrZ-2B6WuYJxxa7-2FugONrzt4VpjS2cJn-2BA5WzLhiXSe6vnfjzZ0mFcPxaDfoVQ0GhyDc9BkLOSdIWgBJuSfNcIUhr9Im6E7Lg-2BDGhAuTLltP3MWigsDpSXpo939xbBR2ldOvxxJsb10xFoLBMcRuHNFjLZCq9warBI1UfcaaanviprEqgl1pMAcsi1Q-3D-3D
References: Nature Communications, 9-Feb-2026
Keywords: Adult neurogenesis, Hippocampal neurogenesis, Immune system, Microglia, TGF-beta signaling, Neural stem cells, Brain plasticity, Alzheimer’s disease, Cognition, Neurodegenerative diseases, Neurons, Brain development

The development of the human medial ganglionic eminence—an embryonic structure giving rise to GABAergic interneurons—is notably influenced by its intricate cellular environment. Previous research largely overlooked the role of microglia, typically associated with immune surveillance, in this context. This new research overturns traditional views, demonstrating that human microglia are far more integral to neural progenitor dynamics than previously understood.

Using neuroimmune human MGE organoids (MGEOs) combined with microglial transplantation, the study meticulously mapped the expression patterns of IGF1 and its receptor IGF1R. They found that microglia uniquely express IGF1, while the neural progenitor radial glia within the MGEOs exhibit high levels of IGF1R, setting the stage for direct signaling interactions. Immunohistochemical analyses confirmed this spatial distribution, reinforcing the hypothesis that microglia-derived IGF1 acts as a paracrine factor promoting progenitor cell proliferation in these developing cortical regions.

The researchers employed an elegant set of functional experiments to elucidate IGF1’s role. MGEOs, cultured either with or without induced microglia, were treated with recombinant human IGF1 protein or IGF1-neutralizing antibodies. Remarkably, IGF1 supplementation rescued progenitor proliferation in organoids devoid of microglia, while neutralizing the factor abolished the proliferative effects typically conferred by microglial transplantation. These results unambiguously pinpointed IGF1 as the critical mediator by which microglia foster interneuron progenitor expansion.

Delving deeper, the team generated IGF1 knockout microglia using CRISPR-Cas9 technology applied to human embryonic stem cells. Transplantation of these IGF1-deficient microglia failed to stimulate MGE progenitor proliferation in MGEOs, a defect that recombinant IGF1 treatment could completely rescue. This genetic validation underscored the indispensable nature of microglial IGF1 in regulating human MGE neurogenesis, providing a robust mechanistic framework.

Interestingly, the study observed that IGF1 knockout did not impact the microglial population’s density, morphology, or distribution within the organoids, indicating that the proliferative effects are due to IGF1’s signaling, rather than microglial presence or migration. Complementary experiments involving IGF1 receptor inhibition—using small molecule inhibitors such as GSK4529 and picropodophyllin—abolished the microglia-induced proliferation, confirming that IGF1 acts through its canonical receptor pathway during this developmental window.

Extending the investigation to cortical organoids, the research team further demonstrated that microglia and microglia-derived IGF1 enhance proliferation among cortical neural progenitor populations marked by PAX6 expression. This finding suggests that microglial IGF1 is a generalizable modulator of neural progenitor proliferation beyond the MGE, potentially influencing diverse neuronal lineages and brain regions during prenatal development.

A fascinating aspect of this study lies in its comparative and evolutionary insights. While IGF1 expression by microglia is well documented in specific mouse brain regions, such as axon tract-associated microglia, the researchers found no detectable IGF1 in the microglia localized to the mouse MGE. Moreover, conditional IGF1 knockout in mouse microglia during embryogenesis did not affect MGE proliferation, highlighting a striking species-specific difference. These observations reinforce the concept that human microglia have evolved unique roles in modulating the developmental dynamics of interneuron progenitors through IGF1 signaling.

This species specificity has profound implications for translational neuroscience and the modeling of human neurodevelopmental disorders. The reliance on rodent systems to infer human brain development may overlook critical pathways such as microglial IGF1 regulation uncovered here. Therefore, human-specific models, such as neuroimmune organoids, prove indispensable for unraveling the nuances of fetal brain maturation and the origins of inhibitory neuron circuitry.

The study also raises intriguing questions about the intersection of immune cells and neural development, placing microglia at the nexus of neuroimmune crosstalk. Given that dysfunctional GABAergic interneuron populations underlie numerous neuropsychiatric conditions, including schizophrenia and autism spectrum disorders, understanding microglial contributions offers promising avenues for therapeutic intervention.

Technically, the use of MGEOs integrated with induced microglia, CRISPR-Cas9 gene editing, and rigorous immunohistochemical quantifications allowed the research team to dissect cellular interactions with unparalleled precision. Their approach provided compelling evidence that IGF1-mediated microglial support is essential in human interneuronal progenitor proliferation, a cornerstone for balanced excitatory-inhibitory dynamics in the cortex.

The identification of IGF1 as a secreted factor by microglia that directly influences radial glial proliferation advances our molecular understanding of human neurogenesis and implicates the neuroimmune axis as a key player. The discovery that microglial IGF1 effects are absent in mice contextualizes the evolutionary divergence in brain development paradigms and underscores the importance of human-specific experimental systems in neurobiology.

In conclusion, this landmark study establishes microglial IGF1 signaling as a pivotal regulator of GABAergic neurogenesis in the prenatal human brain. By revealing a species-specific neuroimmune mechanism, it challenges pre-existing dogma and paves the way for reimagining the cellular choreography underlying brain assembly. The implications for developmental neuroscience, disease modeling, and regenerative medicine are profound, exemplifying how fundamental research can illuminate the complex biology of human brain formation.

Subject of Research: Microglial regulation of neurogenesis in the prenatal human medial ganglionic eminence via IGF1 signaling.

Article Title: Microglia regulate GABAergic neurogenesis in prenatal human brain through IGF1.

Article References:
Yu, D., Jain, S., Wangzhou, A. et al. Microglia regulate GABAergic neurogenesis in prenatal human brain through IGF1. Nature (2025). https://doi.org/10.1038/s41586-025-09362-8

Image Credits: AI Generated