Graduate Student Sanford Burnham Prebys Medical Discovery Institute San Diego, California, United States
Abstract: Perinatal hypoxic-ischemic injury (HII) is the most common cause of neurologic disability in children. HII initiates a molecular cascade that results in widespread neurodegeneration, characterized not only by neuron death, but also impaired glial function, neuroinflammation, neural network disruption, vascular reorganization, & glial scarring. The penumbra of the infarct is characterized by injured but salvageable cells. If the penumbra is rescued, inter-neuronal communication not only within the penumbra but from one brain region to the other as fibres de passage are preserved; if not, they are axotomized. We’ve published that the penumbra (though not the necrotic core, where the cells are already dead) can be rescued by transplanted human neural stem cells (hNSCs) that migrate to the penumbra, promoting histological, MRI, & functional improvements. Though great progress has been made in using single cell ‘omics to characterize normal mammalian brain development, little, if any, work has been published using the same techniques to characterize the injured developing brain spatially at a single-cell level. We are comparing the brains of intact rat pups with age-matched pups that have been subjected to HII & have subsequently received: no treatment (HII-only), hNSC transplantation, or hNSC-conditioned media. The infarcts of these rats are being characterized using single-nuclei RNA-sequencing (snRNAseq) as well as spatial transcriptomics & proteomics. We are also characterizing the axons within & passing through the penumbra, identifying molecular mechanisms by which neural networks are preserved. Data-to-date suggest that trans-penumbral neural connections may be preserved by promoting endogenous astrocytes to shift their fate from reactive to trophic (reminiscent of their fetal cerebrogenic phenotype). Our snRNAseq data suggest – unexpectedly – that astrocytes, not solely neurons, are impacted by HII. Both snRNAseq & spatial analysis are being used to build a novel library of HII-associated molecules – both with & without rescue from hNSCs. We have begun identifying the cytoarchitectural topography & ‘omics profile that hNSCs induce to promote trophic astrocyte resurgence & inhibit reactive astrogliosis & microgliosis, consequently promoting neural network integrity in an injured brain.
