Isolation, characterization, and genetic profiling of subpopulations of olfactory ensheathing cells from the olfactory bulb

Abstract

Olfactory ensheathing cells (OECs) play a crucial role during neurogenesis of primary olfactory neurons. Transplantation of OECs is considered as a promising new therapy for central nervous system repair. Nevertheless, OECs are constituted of distinct subpopulations and their role during neurogenesis is not clearly understood. In particular, OECs from the olfactory bulb (OB) constitute a heterogeneous, but not yet isolated and characterized, population of cells. In our study, flow cytometry analyses of primary OB cultures, based on cell surface expression of low-affinity nerve growth factor receptor (p75), reveal the presence of two distinct populations of OECs. Indeed, some of them express a high level of p75 (P75High) and the other a low level of p75 (P75Low). Effects of OB microenvironment were assessed, and we were able to show that fibroblasts mediate the induction of these two populations through the secretion of soluble factors. To characterize P75High and P75Low OECs, cells were sorted based on their differential expression of p75. Microarray analyses revealed that P75High OECs overexpress genes implicated in modulation of extracellular matrix and cell sorting, whereas P75Low OECs overexpress genes involved in regulation of the inflammatory response and axonal guidance. These results permit, for the first time, to isolate the two distinct subpopulations of OECs from OB, and suggest their specific role during neurogenesis.

Potential of Olfactory Ensheathing Cells from Different Sources for Spinal Cord Repair

“…First, deprivation of microenvironment induces a loss of the two distinct subpopulations of OECs present in primary OB cultures, leading to a decrease in the recovery of the treated animals [21]. Secondly the rate of OECs is around 70% in primary OB cultures which might not be a limiting factor for functional and anatomical recovery in our SCI model.…”

“…Following transplantation in lesioned spinal cord, OECs were shown to enhance axonal regrowth, regulate astrocyte reactivity, increase angiogenesis and modulate glial scar leading to functional recovery in various models of SCI in rodents [15]–[19]. However, OECs are constituted of several subpopulations and the role of each of them following transplantation in injured spinal cord is not well described [20], [21]. Specifically, OECs can be obtained from two different regions: olfactory mucosa (OM) and olfactory bulbs (OB) and it appears that OECs obtained from OM (OM-OECs) and OB (OB-OECs) have not the same properties and effects after transplantation in vivo [22], [23].…”

“…Specifically, OECs can be obtained from two different regions: olfactory mucosa (OM) and olfactory bulbs (OB) and it appears that OECs obtained from OM (OM-OECs) and OB (OB-OECs) have not the same properties and effects after transplantation in vivo [22], [23]. Moreover, culture conditions, in particular the presence of microenvironment, can greatly influence OECs behaviors in vitro and in vivo [21], [24]. OM-OECs are closely associated with primary olfactory neurons and fibroblasts, whereas OB -OECs are in contact with fibroblasts and astrocytes both in vitro and in vivo [25]–[28].…”

Olfactory ensheathing cells from the nasal mucosa and olfactory bulb have distinct membrane properties

“…OECs from the OB segregate into distinct phenotypic populations when maintained in vitro (Hayat et al, ). Some are spindle‐shaped and Schwann cell‐like, whereas others maintain a flattened astrocyte‐like morphology, and these cell types display differences in their expression of glial markers (Honore et al, ). OECs within the OB and OM have distinct gene expression profiles (Guerout et al, ), but it is currently unclear whether these genetically and spatially separate populations mediate common physiological mechanisms that ensure normal homeostasis and continual neuronal turnover.…”

Calcium-induced calcium release and gap junctions mediate large-scale calcium waves in olfactory ensheathing cells in situ

“…OECs in the ONL o are considered to promote growth of axons of olfactory receptor neurons, while OECs in the ONL i guide axons to their respective glomerulus according to the type of olfactory receptor protein expressed [41]. In a recent differential study on OECs sorted by fluorescence-activated cell sorting, this assumption was supported; P75-positive OECs overexpress genes involved in supporting axon growth, whereas OECs with low P75-immunoreactivity overexpress genes involved in axon guidance [44]. We showed that OECs subpopulations also differ in their Ca 2+ signalling properties.…”