Abstract
Olfactory ensheathing cells (OECs) are heterogeneous in morphology, antigenic profiles and functions, and these OEC subpopulations have shown different outcomes following OEC transplantation for central nervous system (CNS) injuries. Morphologically, OECs are divided into two subpopulations, process-bearing (Schwann cells-like) and flattened (astrocytes-like) OECs, which could switch between each other and are affected by extracellular and intracellular factors. However, neither the relationship between the morphology and function of OECs nor their molecular mechanisms have been clarified. In the present study, we first investigated morphological and functional differences of OECs under different cytokine exposure conditions. It demonstrated that OECs mainly displayed a process-bearing shape under pro-inflammatory conditions (lipopolysaccharide, LPS), while they displayed a flattened shape under anti-inflammatory conditions [interleukin-4 (IL-4) and transforming growth factor-β1 (TGF-β1)]. The morphological changes were partially reversible and the Rho-associated coiled-coil-containing protein kinase (ROCK)/F-actin pathway was involved. Functionally, process-bearing OECs under pro-inflammatory conditions showed increased cellular metabolic activity and a higher migratory rate when compared with flattened OECs under anti-inflammatory conditions and significantly promoted neurite outgrowth and extension. Remarkably, the morphological shift towards process-bearing OECs induced by ROCK inhibitor Y27632 enhanced the neurite outgrowth-promoting property of OECs. Furthermore, as the downstream of the ROCK pathway, transcriptional co-activator Yes-associated protein (YAP) mediated morphological shift and enhanced the neurite outgrowth-promoting property of OECs through upregulating the expression of the neural adhesion molecule L1-CAM. Our data provided evidence that OECs with specific shapes correspond to specific functional phenotypes and opened new insights into the potential combination of OECs and small-molecule ROCK inhibitors for the regeneration of CNS injuries.
Highlights
In the olfactory system, olfactory ensheathing cells (OECs), known as olfactory ensheathing glia or olfactory Schwann cells, project from the olfactory epithelium (OE) to the olfactory bulb (OB) in the central nervous system (CNS) and envelop several olfactory receptor neuron (ORN) axons (Kott et al, 1994; Su and He, 2010)
According to the criteria of process-bearing and flattened Olfactory ensheathing cells (OECs) (Huang et al, 2008), we first analyzed the effects of pro-inflammatory (LPS) and anti-inflammatory (IL-4 and transforming growth factor-β1 (TGF-β1)) conditions on the cell morphology of OEC using low-density OECs cultured on PDL-coated plates by time-lapse images
OEC transplantation is intensively regarded as a promising therapeutic strategy for CNS injuries and neurodegenerative diseases
Summary
Olfactory ensheathing cells (OECs), known as olfactory ensheathing glia or olfactory Schwann cells, project from the olfactory epithelium (OE) to the olfactory bulb (OB) in the central nervous system (CNS) and envelop several olfactory receptor neuron (ORN) axons (Kott et al, 1994; Su and He, 2010). One previous study showed that p75NTR-positive OECs were more effective in promoting neurite regrowth when co-cultured with adult rat retinal ganglion cells (RGCs; Kumar et al, 2005). It appears that morphological plasticity and differential expressions of markers by OECs are more likely a reflection of their functional plasticity. To be in line with this notion, several studies demonstrated that morphological phenotypes of OECs exhibited different migratory properties (Huang et al, 2008, 2011a; Wang and Huang, 2012) All these studies make it clear that OECs are a single but malleable phenotype with extensive morphological and functional plasticity depending on the environmental stimuli (Vincent et al, 2005; Huang et al, 2008)
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