No abstract

Throughout the lifespan, microglia, the primary innate immune cells of the brain, fulfill a plethora of homeostatic as well as active immune defense functions, and their aginginduced dysfunctionality is now considered as a key trigger of aging-related brain disorders. Recent evidence suggests that both organism's sex and age critically impact the functional state of microglia but in vivo determinants of such state(s) remain unclear. Therefore, we analyzed in vivo the sex-specific functional states of microglia in young adult, middle aged and old wild type mice by means of multicolor two-photon imaging, using the microglial Ca 2+ signaling and directed process motility as main readouts. Our data revealed the sex-specific differences in microglial Ca 2+ signaling at all ages tested, beginning with young adults. Furthermore, for both sexes it showed that during the lifespan the functional state of microglia changes at least twice. Already at middle age the cells are found in the reactive or immune alerted state, characterized by heightened Ca 2+ signaling but normal process motility whereas old mice harbor senescent microglia with decreased Ca 2+ signaling, and faster but disorganized directed movement of microglial processes. The 6-12 months long caloric restriction (70% of ad libitum food intake) counteracted these aging-induced changes shifting many but not all functional properties of microglia toward a younger phenotype. The improvement of Ca 2+ signaling was more pronounced in males. Importantly, even short-term (6-week-long) caloric restriction beginning at old age strongly improved microglial process motility and induced a significant albeit weaker improvement of microglial Ca 2+ signaling. Together, these data provide first sex-specific in vivo characterization of functional properties of microglia along the lifespan and identify caloric restriction as a potent, cost-effective, and clinically relevant tool for rejuvenation of microglia.

Progenitor cells expressing proteoglycan NG2 (also known as oligodendrocyte precursor cells or polydendrocytes) are widespread in the grey and white matter of the CNS; they comprise 8-9% of the total cell population in adult white matter, and 2-3% of total cells in adult grey matter. NG2 cells have a complex stellate morphology, with highly branched processes that may extend more than 100 lm around the cell body. NG2 cells express a complex set of voltage-gated channels, AMPA ⁄ kainate and ⁄ or c-aminobutyric acid (GABA) A receptors, and receive glutamatergic and ⁄ or GABAergic synaptic input from neurons. In every region of the brain NG2 cells are found as proliferative cells, and the fraction of actively cycling NG2 cells is quite high in young as well as in adult animals. During development NG2 cells either differentiate into myelinating oligodendrocytes (and possibly also few astrocytes and neurons) or persist in the brain parenchyma as NG2 cells. This review highlights new findings related to the morphological and electrophysiological changes of NG2 cells, and the fate of synaptic input between neurons and NG2 cells during proliferation and differentiation of these cells in the neonatal and adult nervous system of rodents.

Background The social distancing and suspension of on-campus learning, imposed by the COVID-19 pandemic, are likely to influence medical training for months if not years. Thus, there is a need for digital replacement for classroom teaching, especially for hands-on courses, during which social distancing is hardly possible. Here, we investigated students’ learning experience with a newly designed digital training course in neurophysiology, with intercalated teaching blocks in either asynchronous (unsupervised online lectures and e-labs) or synchronous (online seminars, supervised by instructors) formats. Methods The accompanying anonymized prospective study included 146 student participants. At the beginning and the end of the course, students were invited to answer anonymous online questionnaires with 18 and 25 items, respectively. We conducted both qualitative analyses of students’ survey responses and statistical analyses of the results of cohort-specific summative examinations. The summative assessment results were compared both between 4 current cohorts and with the respective historical cohorts. Results Despite having little prior experience with e-learning (4.5 on the 1-7 scale), students adapted remarkably well to this online format. They appreciated its higher flexibility, time efficiency, student-oriented nature (especially when using inverted classroom settings), tolerance towards the individual learning style and family circumstances, and valued the ability to work through lectures and e-labs at their own learning speed. The major complaints concerned diminished social contacts with instructors and fellow students, the inability to ask questions as they occur, and the lack of sufficient technical expertise. The students valued the newly developed e-labs, especially the implementation of interactive preparative measures (PreLabs) and the intuitive lab design offered by the chosen software (Lt Platform from AD Instruments). The summative examinations at the end of the course documented the quality of knowledge transfer, which was comparable to that of previous classically instructed cohorts. Conclusion Despite the missing personal contact between the faculty and the students, inherent to online teaching, the all-digital training course described here proofed to be of good educational value and, in case the pandemic continues, is worse considering for the future. Some of the described building blocks, like digital lectures or interactive PreLabs, may survive the pandemics to enrich the medical education toolbox in the future.

Schwann cells (SCs) are myelinating cells of the PNS. Although SCs are known to express different channels and receptors on their surface, little is known about the activation and function of these proteins. Ionotropic glutamate receptors are thought to play an essential role during development of SC lineage and during peripheral nerve injury, so we sought to study their functional properties. We established a novel preparation of living peripheral nerve slices with preserved cellular architecture and used a patch-clamp technique to study AMPA-receptor (AMPAR)-mediated currents in SCs for the first time. We found that the majority of SCs in the nerves dissected from embryonic and neonatal mice of both sexes respond to the application of glutamate with inward current mediated by Ca-permeable AMPARs. Using stationary fluctuation analysis (SFA), we demonstrate that single-channel conductance of AMPARs in SCs is 8-11 pS, which is comparable to that in neurons. We further show that, when SCs become myelinating, they downregulate functional AMPARs. This study is the first to demonstrate AMPAR-mediated conductance in SCs of vertebrates, to investigate elementary properties of AMPARs in these cells, and to provide detailed electrophysiological and morphological characterization of SCs at different stages of development. We provide several important conceptual and technical advances in research on the PNS. We pioneer the first description of AMPA receptor (AMPAR)-mediated currents in the PNS glia of vertebrates and provide new insights into the properties of AMPAR channels in peripheral glia; for example, their Ca permeability and single-channel conductance. We describe for the first time the electrophysiological and morphological properties of Schwann cells (SCs) at different stages of development and show that functional AMPARs are expressed only in developing, not mature, SCs. Finally, we introduce a preparation of peripheral nerve slices for patch-clamp recordings. This preparation opens new possibilities for studying the physiology of SCs in animal models and in surgical human samples.