Issadore, D. A. | Search bioRxiv

bioRxiv2025

Microglia modulate concussion biomarkers and cognitive recovery in male mice

There is a critical unmet need for concussion biomarkers that predict cognitive recovery. Existing TBI biomarkers largely capture acute cellular damage rather than the multicellular repair processes that determine long-term outcome, and whether microglia causally shape divergent trajectories remains unclear. Here, we used PLX5622 to deplete microglia and other CSF1R-dependent myeloid cells in a male mouse model comparing concussion alone to concussion preconditioned by prior subconcussive impacts. Microglial depletion had no effect on cognitive outcome after concussion alone, but introduced a significant novel object recognition deficit specifically when concussion was preconditioned, revealing a history-dependent role for microglia in recovery. To identify the molecular substrates of this divergence, we profiled brain-derived GluA1/2+ extracellular vesicle (EV) miRNAs and single-nuclei transcriptomes from the injured brain. Diagnostic and injury-history EV miRNA biomarkers discriminated between concussion subtypes in microglia-intact animals but lost this discriminative power after depletion, indicating that these neuron-enriched biomarkers are influenced by microglia-dependent biology rather than injury alone. snRNA-seq further revealed that microglial depletion selectively induced transcriptional programs related to oligodendrocyte maturation after unconditioned concussion, a candidate substrate for this microglia-dependence. Finally, we identified a serum EV miRNA panel that estimated cognitive recovery across injury conditions. Together, these findings identify a history-dependent role for microglia in concussion outcome and characterize brain-derived EVs as a potentially promising tool for surveilling the neuroinflammatory processes influencing recovery.

bioengineering↗

bioRxiv2024

High-throughput single-cell, single-mitochondrial DNA assay using hydrogel droplet microfluidics

There is growing interest in understanding the biological implications of single cell heterogeneity and intracellular heteroplasmy of mtDNA, but current methodologies for single-cell mtDNA analysis limit the scale of analysis to small cell populations. Although droplet microfluidics have increased the throughput of single-cell genomic, RNA, and protein analysis, their application to sub-cellular organelle analysis has remained a largely unsolved challenge. Here, we introduce an agarose-based droplet microfluidic approach for single-cell, single-mtDNA analysis, which allows simultaneous processing of hundreds of individual mtDNA molecules within >10,000 individual cells. Our microfluidic chip encapsulates individual cells in agarose beads, designed to have a sufficiently dense hydrogel network to retain mtDNA after lysis and provide a robust scaffold for subsequent multi-step processing and analysis. To mitigate the impact of the high viscosity of agarose required for mtDNA retention on the throughput of microfluidics, we developed a parallelized device, successfully achieving ~95% mtDNA retention from single cells within our microbeads at >700,000 drops/minute. To demonstrate utility, we analyzed specific regions of the single mtDNA using a multiplexed rolling circle amplification (RCA) assay. We demonstrated compatibility with both microscopy, for digital counting of individual RCA products, and flow cytometry for higher throughput analysis.

bioengineering↗