Dr. Jean Paul Chadarevian and Joia K. Capocchi attend 2024 Keystone Symposia on Neurodegeneration in Santa Fe, NM where Jean Paul presented, “Therapeutic potential of human microglia transplantation in a chimeric model of CSF1R-related leukoencephalopathy“.

Dr. Blurton-Jones (Examining the therapeutic potentical of microglial transplantation in chimeric models of AD and FTD) and Dr. Davtyan (Human Monocytes remain transcrptionally and functionally distinct from microglia despite long-term brain engraftment) presented at the International Society of Molecular Neurodegeneration 2024 conference on aging, immunity, and peripheral factors in neurodegenerative disease in Seoul, Korea.

Examining the Diverse Pathological Consequences of Microglial Absence 

Our understanding of microglia, the principal immune cells of the central nervous system (CNS), continues to evolve as new models and approaches shift our perception of these intriguing cells. Previously envisioned as passive guardians of the brain, microglia have since been shown to play critical roles in development, neuroplasticity, and neurological disease.To further understand the role of microglia in AD and the impact of microglial absence on the aging brain, my thesis studies utilized ‘FIRE mice’, a genetic model that lacks microglia. FIRE mice harbor a homozygous deletion within the Fms intronic regulatory element (FIRE) super-enhancer, leading to a loss of CSF1R expression and congenital absence of microglia.  To examine the role of microglia in AD pathogenesis, I crossed FIRE mice with 5xfAD mice that develop robust beta-amyloid plaque pathology. Remarkably, I found that absence of microglia promotes the development of cerebral amyloid angiopathy (CAA), brain calcification, and cerebral hemorrhages in AD mice. Importantly, transplantation of wildtype microglia prevents each of these pathological changes. To determine whether microglia absence alone can also induce pathological changes within the aging brain, I further examined 9-10 month-old FIRE mice in comparison to wildtype littermates and explored the impact of postnatal microglial transplantation, demonstrating that prolonged absence of microglia leads to the development of astrogliosis, calcification, and seizures, mimicking many of the pathological features of a rare human primary microgliopathy.  Taken together, my thesis studies have revealed important roles for microglia in protecting the brain against age- and disease-related development of vascular, and white matter pathologies. These findings not only deepen our understanding of microglia’s roles in neurodegenerative diseases, but also provide initial evidence to support microglial transplantation as a viable therapeutic approach for a variety of neurodegenerative diseases.

The Blurton-Jones Lab attends ADPD 2024 in Lisbon, Portugal with three talks and two presentations. Congratulations to our speakers and graduate student, Alina Lahian, on her poster presentation!

Engineering human induced pluripotent stem cells to enable microglial replacement therapy in the central nervous system

Immune cell therapies (ICT) are becoming more mature options for a  variety of diseases. As the resident immune cell of the brain, microglia stand out as the ideal candidate for ICT approaches in the central nervous system. Combining recent advances in gene editing and iPSC-microglia (iMG) differentiation, we sought to investigate whether microglia could be harnessed to provide widespread delivery of therapeutic cells and proteins to the brain. Collectively our studies have revealed three principal findings: 1) iPSC-microglia can be widely engrafted into a recipient adult brain via an inhibitor-resistant protocol; 2) transplantation of CRISPR-corrected iPSC-microglia can prevent and even reverse neuropathologies in a mouse model of ALSP, a rare neurodegenerative disease caused by loss of microglia; and 3) iPSC-microglia can be genetically-engineered ex vivo to effectively deliver therapeutic proteins locally or CNS-wide in response to neuropathologies such as amyloid plaques. Together these findings suggest that patient-derived microglia could offer a promising new platform for the development of future immune cell therapies in the CNS.

CRISPR generation of CSF1R-G795A human microglia for robust microglia replacement in a chimeric mouse model

Chimeric mouse models have recently been developed to study human microglia in vivo. However, the widespread engraftment of donor microglia within the adult brain has been challenging. Here, we present a protocol to introduce the G795A point mutation using CRISPR-Cas9 into the CSF1R locus of human pluripotent stem cells. We also describe an optimized microglial differentiation technique for transplantation into newborn or adult recipients. We then detail pharmacological paradigms to achieve widespread and near-complete engraftment of human microglia. For complete details on the use and execution of this protocol, please refer to Chadarevian et al. (2023).