Zagrean, A.-M. | bioRxiv Science

bioRxiv2026

A novel multicellular model of the adult mouse sinoatrial node retains spontaneous electrical activity and enables live investigation of the S100B-associated cell population

Approximately half of the adult sinoatrial node (SAN) consists of non-myocyte populations, indicating that cardiac pacemaking depends on interactions within a multicellular tissue rather than on pacemaker cardiomyocytes alone. Among these, an S100B-associated cell population has been implicated in pacemaker function, yet its identity and physiological roles remain poorly understood. These cells are rare and dispersed throughout the small, structurally complex SAN, making them difficult to observe repeatedly while preserving the native multicellular environment. Here, we established a dissociated multicellular culture of adult mouse SAN tissue on soft collagen-gelatin hydrogels that retains spontaneous electrical activity and permits longitudinal live imaging of S100B-associated cells. Using an S100B-EGFP+ reporter, we identified at least six reproducible morphological and behavioral phenotypes, including migration, proliferation, phagocytic behavior, and spontaneous self-organization into three-dimensional clusters. Cultures remained spontaneously electrically active for more than 10 days in vitro, with peak activity around day 10. This multicellular culture model bridges the gap between intact SAN preparations and isolated-cell cultures, allowing repeated observation of rare S100B-associated cells within a spontaneously active multicellular environment. HighlightsO_LIThe platform enables longitudinal live imaging of rare S100B-associated cells within an diverse multicellular SAN culture. C_LIO_LILive imaging reveals at least six reproducible morphological and behavioral phenotypes of S100B-associated cells. C_LIO_LIDissociated multicellular SAN cultures remain spontaneously electrically active for more than 10 days in vitro. C_LI

cell biology↗

bioRxiv2018

Chemicogenetic recruitment of specific interneurons suppresses seizure activity

Enhancing the brains endogenous inhibitory mechanisms represents an important strategy for suppressing epileptic discharges. Indeed, drugs that boost synaptic inhibition can disrupt epileptic seizure activity, although these drugs generate complex effects due to the broad nature of their action. Recently developed chemicogenetic techniques provide the opportunity to pharmacologically enhance endogenous inhibitory mechanisms in a more selective manner. Here we use chemicogenetics to assess the anti-epileptic potential of enhancing the synaptic output from three major interneuron populations in the hippocampus: parvalbumin (PV), somatostatin (SST) and vasoactive intestinal peptide (VIP) expressing interneurons. Targeted pre- and post-synaptic whole cell recordings in an in vitro hippocampal mouse model revealed that all three interneuron types increase their firing rate and synaptic output following chemicogenetic activation. However, the interneuron populations exhibited different anti-epileptic effects. Recruiting VIP interneurons resulted in a mixture of pro-epileptic and anti-epileptic effects. In contrast, recruiting SST or PV interneurons produced robust suppression of epileptiform activity. PV interneurons exhibited the strongest effect per cell, eliciting at least a five-fold greater reduction in epileptiform activity than the other cell types. Consistent with this, we found that chemicogenetic recruitment of PV interneurons was effective in an in vivo mouse model of hippocampal seizures. Following efficient delivery of the chemicogenetic tool, pharmacological enhancement of the PV interneuron population suppressed a range of seizure-related behaviours and prevented generalized seizures. Our findings therefore support the idea that selective chemicogenetic enhancement of synaptic inhibitory pathways offers potential as an anti-epileptic strategy.\n\nSignificance statementDrugs that enhance synaptic inhibition can be effective anticonvulsants but often cause complex effects due to their widespread action. Here we examined the anti-epileptic potential of recently developed chemicogenetic techniques, which offer a way to selectively enhance the synaptic output of distinct types of inhibitory neurons. A combination of in vitro and in vivo experimental models were used to investigate seizure activity in the mouse hippocampus. We find that chemicogenetically recruiting the parvalbumin-expressing population of inhibitory neurons produces the strongest anti-epileptic effect per cell, and that recruiting this cell population can suppress a range of epileptic behaviours in vivo. The data therefore support the idea that targeted chemicogenetic enhancement of synaptic inhibition offers promise for developing new treatments.

neuroscience↗