Fisher, E. S. | Search bioRxiv

bioRxiv2022

Single Cell Profiling of CD45+ Spinal Cord Cells Reveals Microglial and B Cell Heterogeneity and Crosstalk Following Spinal Cord Injury

It is well established that immune cells play crucial roles after spinal cord injury (SCI). However, our knowledge of the contributions of various immune cells to injury progression and repair is incomplete. These gaps in understanding hamper development of SCI therapeutics. In the current study, using single-cell RNA sequencing, and transcriptomic analysis, the populations of resident and circulating CD45+ immune cells present within the uninjured and injured mouse spinal cord were identified. In the uninjured and subacutely-injured (7 day) spinal cord, most CD45+ cells were microglia while in chronic SCI (60 day) B cells predominated. Examination of microglia and B cell clusters showed subtype-specific alterations after SCI, including the presence of both immature and mature B cells chronically. Analysis of the expression of signaling partners in B cells and microglia identified injury-related microglia-B-cell interactions. This sequencing resource establishes unidentified interactions revealing new mechanisms to target inflammatory responses for SCI repair.

neuroscience↗

bioRxiv2022

Adenosine A1R/A3R Agonist AST-004 Reduces Brain Infarction in Mouse and Rat Models of Acute Ischemic Stroke

Acute ischemic stroke (AIS) is the second leading cause of death globally. No Food and Drug Administration (FDA) approved therapies exist targeting cerebroprotection following stroke. Our group recently reported significant cerebroprotection with the adenosine A1/A3 receptor agonist, AST-004, in a transient stroke model in non-human primates (NHP) and in a preclinical mouse model of traumatic brain injury (TBI). However, the specific receptor pathway activated was only inferred based on in vitro binding studies. The current study investigated the underlying mechanism of AST-004 cerebroprotection in two independent models of AIS: permanent photothrombotic stroke in mice and transient middle cerebral artery occlusion (MCAO) in rats. AST-004 treatments across a range of doses were cerebroprotective and efficacy could be blocked by A3R antagonism, indicating a mechanism of action that does not require A1R agonism. The high affinity A3R agonist MRS5698 was also cerebroprotective following stroke, but not the A3R agonist Cl-IB-MECA under our experimental conditions. AST-004 efficacy was blocked by the astrocyte specific mitochondrial toxin fluoroacetate, confirming an underlying mechanism of cerebroprotection dependent on astrocyte mitochondrial metabolism. An increase in A3R mRNA levels following stroke suggested an intrinsic cerebroprotective response that was mediated by A3R signaling. Together, these studies confirm certain A3R agonists, such as AST-004, are promising new therapeutics for the treatment of AIS.

neuroscience↗