Establishment of a high-content compatible platform to assess effects of monocyte-derived factors on neural stem cell proliferation and differentiation.

During neuroinflammation, monocytes that infiltrate the central nervous system (CNS) may contribute to regenerative processes depending on their activation status. However, the extent and mechanisms of monocyte-induced CNS repair in patients with neuroinflammatory diseases remain largely unknown, partly due to the lack of a fully human assay platform that can recapitulate monocyte-neural stem cell interactions within the CNS microenvironment. We therefore developed a human model system to assess the impact of monocytic factors on neural stem cells, establishing a high-content compatible assay for screening monocyte-induced neural stem cell proliferation and differentiation. The model combined monocytes isolated from healthy donors and human embryonic stem cell derived neural stem cells and integrated both cell-intrinsic and -extrinsic properties. We identified CNS-mimicking culture media options that induced a monocytic phenotype resembling CNS infiltrating monocytes, while allowing adequate monocyte survival. Monocyte-induced proliferation, gliogenic fate and neurogenic fate of neural stem cells were affected by the conditions of monocytic priming and basal neural stem cell culture as extrinsic factors as well as the neural stem cell passage number as an intrinsic neural stem cell property. We developed a high-content compatible human in vitro assay for the integrated analysis of monocyte-derived factors on CNS repair.

Chi3l3 induces oligodendrogenesis in an experimental model of autoimmune neuroinflammation.

In demyelinating diseases including multiple sclerosis (MS), neural stem cells (NSCs) can replace damaged oligodendrocytes if the local microenvironment supports the required differentiation process. Although chitinase-like proteins (CLPs) form part of this microenvironment, their function in this differentiation process is unknown. Here, we demonstrate that murine Chitinase 3-like-3 (Chi3l3/Ym1), human Chi3L1 and Chit1 induce oligodendrogenesis. In mice, Chi3l3 is highly expressed in the subventricular zone, a stem cell niche of the adult brain, and in inflammatory brain lesions during experimental autoimmune encephalomyelitis (EAE). We find that silencing Chi3l3 increases severity of EAE. We present evidence that in NSCs Chi3l3 activates the epidermal growth factor receptor (EGFR), thereby inducing Pyk2-and Erk1/2- dependent expression of a pro-oligodendrogenic transcription factor signature. Our results implicate CLP-EGFR-Pyk2-MEK-ERK as a key intrinsic pathway controlling oligodendrogenesis.