Human genetics and preclinical studies have identified key contributions of TREM2 to several neurodegenerative conditions, inspiring efforts to modulate TREM2 therapeutically. Here, we characterize the activities of three TREM2 agonist antibodies in multiple mixed-sex mouse models of Alzheimer's disease (AD) pathology and remyelination. Receptor activation and downstream signaling are explored in vitro, and active dose ranges are determined in vivo based on pharmacodynamic responses from microglia. For mice bearing amyloid-β (Aβ) pathology (PS2APP) or combined Aβ and tau pathology (TauPS2APP), chronic TREM2 agonist antibody treatment had limited impact on microglia engagement with pathology, overall pathology burden, or downstream neuronal damage. For mice with demyelinating injuries triggered acutely with lysolecithin, TREM2 agonist antibodies unexpectedly disrupted injury resolution. Likewise, TREM2 agonist antibodies limited myelin recovery for mice experiencing chronic demyelination from cuprizone. We highlight the contributions of dose timing and frequency across models. These results introduce important considerations for future TREM2-targeting approaches.
Copyright © 2024 the authors.

Heterozygous mutations in the granulin (GRN) gene are a leading cause of frontotemporal lobar degeneration with TDP-43 aggregates (FTLD-TDP). Polymorphisms in TMEM106B have been associated with disease risk in GRN mutation carriers and protective TMEM106B variants associated with reduced levels of TMEM106B, suggesting that lowering TMEM106B might be therapeutic in the context of FTLD. Here, we tested the impact of full deletion and partial reduction of TMEM106B in mouse and iPSC-derived human cell models of GRN deficiency. TMEM106B deletion did not reverse transcriptomic or proteomic profiles in GRN-deficient microglia, with a few exceptions in immune signaling markers. Neither homozygous nor heterozygous Tmem106b deletion normalized disease-associated phenotypes in Grn -/-mice. Furthermore, Tmem106b reduction by antisense oligonucleotide (ASO) was poorly tolerated in Grn -/-mice. These data provide novel insight into TMEM106B and GRN function in microglia cells but do not support lowering TMEM106B levels as a viable therapeutic strategy for treating FTD-GRN.
© 2023 The Authors.

Human pluripotent stem cell (hPSC)-derived tissues can be used to model diseases in cell types that are challenging to harvest and study at-scale, such as neutrophils. Neutrophil dysregulation, specifically neutrophil extracellular trap (NET) formation, plays a critical role in the prognosis and progression of multiple diseases, including COVID-19. While hPSCs can generate limitless neutrophils (iNeutrophils) to study these processes, current differentiation protocols generate heterogeneous cultures of granulocytes and precursors. Here, we describe a method to improve iNeutrophil differentiations through the deletion of GATA1. GATA1 knockout (KO) iNeutrophils are nearly identical to primary neutrophils in form and function. Unlike wild-type iNeutrophils, GATA1 KO iNeutrophils generate NETs in response to the physiologic stimulant lipopolysaccharide, suggesting they are a more accurate model when performing NET inhibitor screens. Furthermore, through deletion of CYBB, we demonstrate that GATA1 KO iNeutrophils are a powerful tool in determining involvement of a given protein in NET formation.
© 2023 The Authors.

Antisense oligonucleotide (ASO) therapeutics are being investigated for a broad range of neurological diseases. While ASOs have been effective in the clinic, improving productive ASO internalization into target cells remains a key area of focus in the field. Here, we investigated how the delivery of ASO-loaded lipid nanoparticles (LNPs) affects ASO activity, subcellular trafficking, and distribution in the brain. We show that ASO-LNPs increase ASO activity up to 100-fold in cultured primary brain cells as compared to non-encapsulated ASO. However, in contrast to the widespread ASO uptake and activity observed following free ASO delivery in vivo, LNP-delivered ASOs did not downregulate mRNA levels throughout the brain after intracerebroventricular injection. This lack of activity was likely due to ASO accumulation in cells lining the ventricles and blood vessels. Furthermore, we reveal a formulation-dependent activation of the immune system post dosing, suggesting that LNP encapsulation cannot mask cellular ASO backbone-mediated toxicities. Together, these data provide insights into how LNP encapsulation affects ASO distribution as well as activity in the brain, and a foundation that enables future optimization of brain-targeting ASO-LNPs.
© 2023 The Authors.

Cancer cells accumulate epigenetic modifications that allow escape from intrinsic and extrinsic surveillance mechanisms. In the case of acute myeloid leukemias (AML) and myelodysplastic syndromes, agents that disrupt chromatin structure, namely hypomethylating agents (HMAs), have shown tremendous promise as an alternate, milder treatment option for older, clinically non-fit patients. HMAs reprogram the epigenetic landscape in tumor cells through the reversal of DNA hypermethylation. Therapeutic effects resulting from these epigenetic changes are incredibly effective, sometimes resulting in complete remissions, but are frequently lost due to primary or acquired resistance. In this study, we describe syngeneic murine leukemias that are responsive to the HMA 5-azacytidine (5-Aza), as determined by augmented expression of a transduced luciferase reporter. We also found that 5-Aza treatment re-established immune-related transcript expression, suppressed leukemic burden and extended survival in leukemia-challenged mice. The effects of 5-Aza treatment were short-lived, and analysis of the immune microenvironment reveals possible mechanisms of resistance, such as simultaneous increase in immune checkpoint protein expression. This represents a model system that is highly responsive to HMAs and recapitulates major therapeutic outcomes observed in human leukemia (relapse) and may serve as a pre-clinical tool for studying acquired resistance and novel treatment combinations.