Abstract
The endocannabinoid system has been implicated in the modulation of adult neurogenesis. Here, we describe the effect of type 1 cannabinoid receptor (CB1R) activation on self-renewal, proliferation and neuronal differentiation in mouse neonatal subventricular zone (SVZ) stem/progenitor cell cultures. Expression of CB1R was detected in SVZ-derived immature cells (Nestin-positive), neurons and astrocytes. Stimulation of the CB1R by (R)-(+)-Methanandamide (R-m-AEA) increased self-renewal of SVZ cells, as assessed by counting the number of secondary neurospheres and the number of Sox2+/+ cell pairs, an effect blocked by Notch pathway inhibition. Moreover, R-m-AEA treatment for 48 h, increased proliferation as assessed by BrdU incorporation assay, an effect mediated by activation of MAPK-ERK and AKT pathways. Surprisingly, stimulation of CB1R by R-m-AEA also promoted neuronal differentiation (without affecting glial differentiation), at 7 days, as shown by counting the number of NeuN-positive neurons in the cultures. Moreover, by monitoring intracellular calcium concentrations ([Ca2+]i) in single cells following KCl and histamine stimuli, a method that allows the functional evaluation of neuronal differentiation, we observed an increase in neuronal-like cells. This proneurogenic effect was blocked when SVZ cells were co-incubated with R-m-AEA and the CB1R antagonist AM 251, for 7 days, thus indicating that this effect involves CB1R activation. In accordance with an effect on neuronal differentiation and maturation, R-m-AEA also increased neurite growth, as evaluated by quantifying and measuring the number of MAP2-positive processes. Taken together, these results demonstrate that CB1R activation induces proliferation, self-renewal and neuronal differentiation from mouse neonatal SVZ cell cultures.
Highlights
In the adult brain, the subventricular zone (SVZ) is endowed with neural stem cells that give rise to highly proliferating progenitor cells, able to differentiate into neurons and glial cells [1,2]
CB1R was detected in immature nestinpositive SVZ cells adhered on poly-D-lysine coverslips (Fig. 1B) and in Glial fibrillary acidic protein (GFAP)-positive astrocytes indicating that its expression is maintained in astrocytes (Fig. 1C, c1)
The role of endocannabinoids in the regulation of neurogenesis has been the subject of several recent studies; most of these studies address the effects of endocannabinoids on hippocampal neurogenesis with emphasis on proliferation
Summary
The SVZ is endowed with neural stem cells that give rise to highly proliferating progenitor cells, able to differentiate into neurons and glial cells [1,2]. Newly generated cells migrate out of the SVZ towards the damaged areas upon several brain injuries and neurodegenerative diseases [7,8]. These proliferative and multipotent cells may represent a potential source of neurons and glia for brain repair, through the recruitment from the endogenous niches or through transplantation strategies [9,10]. Deciphering the molecular mechanisms controlling these events will contribute to the development of new strategies to treat brain diseases
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