Microglia: The Bodyguard and the Hunter of the Adult Neurogenic Niche

Rewiring of Memory Circuits: Connecting Adult Newborn Neurons With the Help of Microglia

“…These steps are regulated by a tightly controlled program that encompasses intrinsic (i.e., signaling cascades and transcription factors), as well as extrinsic factors. Among these later ones stand out circulating hormones and peptides (such as cortisol, growth factors, or inflammatory mediators), extracellular matrix composition, and neighboring cells that compose the cellular niche: adult neurons, astrocytes, blood vessels and microglia ( Sierra et al, 2010 ; Ming and Song, 2011 ; Valero et al, 2012 , 2016 , 2017 ; Aimone et al, 2014 ). In this review we will specifically focus on how microglia modulates the formation of adult-born GCs exerting their functions on the different steps of the neurogenic cascade, especially on the integration of the new neurons to the hippocampal circuitry ( Figure 1 ).…”

“…that have been suggested to affect proliferation, differentiation, and survival of newborn cells. Importantly, changes in microglia induced by neuroinflammation, aging, and pathology may contribute to the reduction in hippocampal adult neurogenesis and to the concomitant defects in memory function ( Valero et al, 2012 , 2016 , 2017 ; Sierra et al, 2014 ). However, there are few data about the possible involvement of microglia on the integration of adult generated GCs into hippocampal circuits.…”

Lifestyle Shapes the Dialogue between Environment, Microglia, and Adult Neurogenesis

“…39−41 The net production of newly integrated neurons depends on the rates of proliferation of rNSCs and ANPs, survival of newborn cells, and neuronal differentiation (including morphological and synaptic maturation), which are regulated by a multifactorial process that encloses interconnected hierarchical levels, from gene expression to behavior. 42 These processes are regulated by multiple intracellular signaling cascades, such as Wnt/β-catenin or CREB (cAMP response element-binding) signaling; 43 cellular elements of the neurogenic niche, such as the activity of surrounding mature neurons, 44 blood vessels, 45 astrocytes, 46 and microglia; 47,48 and lifestyle factors that include diet, physical activity, stress, social interaction, and sexual activity. 49 ■ MICROGLIA Microglial cells are the only resident immune cell of the CNS and its population is maintained by self-renewal without the participation of cells from the peripheral immune system.…”

Can we talk about microglia without neurons? A discussion of microglial cell autonomous properties in culture

“…Interestingly, microglial cells are able to self-renew independently of circulating monocytes or bone marrow hematopoietic stem cells (Ajami et al, 2007 ; Elmore et al, 2014 ), and show a specific molecular signature (Butovsky et al, 2014 ). Moreover, during the last decade microglial cells have been demonstrated to be involved in normal brain development and function while maintaining a, previously assumed, “resting” state (Pont-Lezica et al, 2011 ; Tremblay et al, 2011 ; Valero et al, 2012 ). Thus, microglial cells cannot be considered just as macrophages.…”