Microglial Calcium Signaling as Sensor of Neuronal Activity

Microglia are an integral part of the brain´s cellular network and have emerged to be crucial regulators of neuronal homeostasis and development as well of brain wiring. Recent evidence indicates that microglial processes extend towards neuronal axons and dendrites, monitoring and regulating neuronal activities and affecting the final formation of neuronal circuits. Some physical interactions of microglia with synapses, as the developmental pruning of afferent inputs, are dependent on neural activity. In this context, one option would be that microglia directly detect neurotransmitter spillover from synapses during neurotransmission. This communication pathway is already established for astrocytes which sense neurotransmitter release via a large repertory of neurotransmitter receptors and transporters that enable them to detect and control the activity of the surrounding neuronal network. Microglia are equipped with a plethora of classical neurotransmitter receptors, as for purines or GABA. The majority of them are G protein-coupled receptors which activation elicits cytosolic Ca2+ elevations. The functional expression of neurotransmitter receptors, as GABAB, was previously demonstrated by live-cell Ca2+ imaging, on sub-populations of freshly isolated microglia or neonatal and adult primary cultured. In this study, two novel microglia Ca2+ indicator mouse models were used to detect microglial Ca2+ level changes in response to neuronal activity in situ. In these mice, the expression of a genetically encoded calcium indicator (GCaMP6m) is driven by endogenous Csf1r gene expression and therefore independent of Cre recombinase activity or viruses, enabling the opportunity to monitor Ca2+ level changes in microglia from neonatal and adult hippocampal brain slices. In the present thesis, I demonstrate that electrical stimulation of the Schaffer collateral pathway results in microglial Ca2+ responses in early postnatal, but not adult hippocampus. Preceding the microglial responses, a similar wave-like propagation of Ca2+ responses was present also in astrocytes, and both were dependent on neuronal activity as evidenced by their sensitivity to tetrodotoxin. Blocking the astrocytic glutamate uptake or the GABA transport, as well as antagonizing GABAB receptors, abolished the stimulation-induced microglial responses. These data therefore suggest that the neuronal activity-induced glutamate uptake and release of GABA by astrocytes triggers the activation of GABAB receptors in microglia. This novel neuron, astrocyte and microglia communication pathway is confined to postnatal brain and might then critically modulate microglial activity in developing neuronal networks

New Preloaded System for Renal and Visceral Arteries in Fenestrated Endografting

Aim/Background: The New Preloaded System (NPS) for renal/visceral arteries (TVVs) is an emerging technology in fenestrated endografting (FEVAR) that allows TVVs cannulation and stenting through the same access of the endograft main body. However, only few preliminary experiences are currently available in the literature. The aim of this study is to report the outcomes of NPS-FEVAR in juxta/para-renal (J/P-AAAs) and thoracoabdominal (TAAAs) aneurysms repair. Methods: This is a prospective (NCT05224219), single-center/observational study of patients submitted to NPS-FEVAR for J/PAAAs and TAAAs between 2019 and 2022 (July). Definitions and outcomes were evaluated according to the current SVS-reporting standard. Technical success (TS) and TS preloaded related, spinal cord ischemia (SCI), and 30-day mortality were assessed as early endpoints. Survival, freedom from reinterventions (FFRs), and freedom from TTVs-instability (FFTVVs-instability) were analyzed during follow-up. Results: Among 157 F/B-EVAR cases, 74 (47%) NPS-FEVAR were planned and enrolled in the study [48 (65%) J/P-AAAs; 26 (35%) TAAAs]. The main indication for NPS-FEVAR was the presence of a hostile iliac axis (54%-73%) or the necessity of expeditious pelvic/lower-limb reperfusion for SCI prevention in TAAAs (20%-27%). Overall, 292 TVVs were accommodated by 289 fenestrations and 3 branches; 188 of 289 (65%) fenestrations were preloaded. NPS-FEVAR configuration was from "below" and "from below to above" in 28 (38%) and 46 (62%) cases, respectively. TS and TS preloaded system-related was 96% (71/74) and 99% (73/74), respectively. Target visceral vessels patency at the completion angiography was 99% (290/292). Failures were 2 renal arteries loss and 1 massive bleeding from a percutaneous closure system breakage. The latter patient developed postoperative multiorgans failure and died on the fifth postoperative day, causing only 30-day/in-hospital mortality (1.3%). One (1.3%) patient with a JAAA and preoperative bilateral occlusion of the hypogastric arteries suffered SCI. The median follow-up was 14 (IQR: 8) months. The estimated 3-year survival was 91% with no aneurysm-related mortality during follow-up. The estimated 3-year FFR and FFTVVs-instability were 85 and 92%, respectively. Conclusion: New preloaded system FEVAR is a safe and effective option in the treatment of J/PAAAs and TAAAs in the presence of hostile iliac access or to guarantee an expeditious pelvic/lower limb reperfusion, leading to satisfactory results in terms of TS, early and mid-term clinical outcomes. Clinical Impact New preloaded system for fenestrated and branched endografting allows to increase the feasibility of the advanced endovascular aortic repair in challenging iliac access, thoracoabdominal aneurysm repair and reduce difficulties in target visceral vessels cannulation

Neurofibromatosis 1 - Mutant microglia exhibit sexually-dimorphic cyclic AMP-dependent purinergic defects

As critical regulators of brain homeostasis, microglia are influenced by numerous factors, including sex and genetic mutations. To study the impact of these factors on microglia biology, we employed genetically engineered mice that model Neurofibromatosis type 1 (NF1), a disorder characterized by clinically relevant sexually dimorphic differences. While microglia phagocytic activity was reduced in both male and female heterozygous Nf1 mutant (Nf1+/-) mice, purinergic control of phagocytosis was only affected in male Nf1+/- mice. ATP-induced P2Y-mediated membrane currents and P2RY12-dependent laser lesion-induced accumulation of microglial processes were also only impaired in male, but not female Nf1+/-, microglia. These defects resulted from Nf1+/- male-specific defects in cyclic AMP regulation, rather than from changes in purinergic receptor expression. Cyclic AMP elevation by phosphodiesterase blockade restored the male Nf1+/- microglia defects in P2Y-dependent membrane currents and process motility. Taken together, these data establish a sex-by-genotype interaction important to microglia function in the adult mouse brain