Neural stem and progenitor cells support and protect adult hippocampal function via vascular endothelial growth factor secretion.

Adult neural stem and progenitor cells (NSPCs) reside in the dentate gyrus (DG) of the hippocampus throughout the lifespan of most mammalian species. In addition to generating new neurons, NSPCs may alter their niche via secretion of growth factors and cytokines. We recently showed that adult DG NSPCs secrete vascular endothelial growth factor (VEGF), which is critical for maintaining adult neurogenesis. Here, we asked whether NSPC-derived VEGF alters hippocampal function independent of adult neurogenesis. We found that loss of NSPC-derived VEGF acutely impaired hippocampal memory, caused neuronal hyperexcitability and exacerbated excitotoxic injury. We also found that NSPCs generate substantial proportions of total DG VEGF and VEGF disperses broadly throughout the DG, both of which help explain how this anatomically-restricted cell population could modulate function broadly. These findings suggest that NSPCs actively support and protect DG function via secreted VEGF, thereby providing a non-neurogenic functional dimension to endogenous NSPCs.

Cyanobacterial blooms: A player in the freshwater environmental resistome with public health relevance?

Cyanobacterial harmful algal blooms (cyanoHABs) are an ecological concern because of large ecosystem-disrupting blooms and a global public health concern because of the cyanotoxins produced by certain bloom-forming species. Another threat to global public health is the dissemination of antibiotic resistance (AR) in freshwater environmental reservoirs from anthropogenic sources, such as wastewater discharge and urban and agricultural runoff. In this study, cyanobacteria are now hypothesized to play a role in the environmental resistome. A non-systematic literature review of studies using molecular techniques (such as PCR and metagenomic sequencing) was conducted to explore indirect and direct ways cyanobacteria might contribute to environmental AR. Results show cyanobacteria can host antibiotic resistance genes (ARGs) and might promote the spread of ARGs in bacteria due to the significant contribution of mobile genetic elements (MGEs) located in genera such as Microcystis. However, cyanobacteria may promote or inhibit the spread of ARGs in environmental freshwater bacteria due to other factors as well. The purpose of this review is to 1) consider the role of cyanobacteria as AR hosts, since cyanoHABs are historically considered to be a separate problem from AR, and 2) to identify the knowledge gap in understanding cyanobacteria as ARG reservoirs. Cyanobacterial blooms, as well as other biotic (e.g. interactions with protists or cyanophages) and abiotic factors, should be studied further using advanced methods such as shotgun metagenomic and long read sequencing to clarify the extent of their functional ARGs/MGEs and influences on environmental AR.