Influence of central glia on spiral ganglion neuron neurite growth

Abstract

Spiral ganglion neurons (SGNs) extend processes that interact with Schwann cells (SCs) and with oligodendrocytes (OLs) and astrocytes (ACs). We investigated the ability of these glial cells to support SGN neurite growth. In the presence of cultured ACs, OLs and SCs, SGN neurites tended to follow SCs and OLs and cross-over ACs. Most neurites initially followed the type of glial cell on which the neuronal cell body was found. To determine the influence of homogeneous populations of glia on neurite growth, SG explants were plated on cultured SCs, ACs or OLs. The number of neurites/explant extending onto SCs (463.89±16.25) was significantly greater than the number extending onto ACs (111.38±38.73) or OLs (6.75±2.21), indicating that populations of central glia inhibit SGN neurite growth. Treatment with cell-permeant cpt-cAMP or forskolin (FSK) each significantly increased the number of neurites on OLs (133.54±25.59 and 292.25±83.57, respectively). cpt-cAMP and FSK each also increased the number of neurites on ACs (213.19± 36.06 and 208.64±59.25, respectively), however the difference was not significant compared with control. The neurites on ACs and OLs failed to grow radially in a well-fasciculated pattern as on SCs. In explants plated on the borders of cultured OL-SC or AC-SC groups, more neurites extended onto SCs compared with OLs and ACs. Conditioned media from OL or AC cultures did not reduce neurite length, implying that the inhibition of neurite growth by central glia is not due to soluble factors. Taken together, these results demonstrate that homogeneous populations of central glia inhibit SGN neurite growth.

Effects of ROCK inhibitor Y27632 and EGFR inhibitor PD168393 on human neural precursors co-cultured with rat auditory brainstem explant

“…Recently Jeon et al (2011) showed that SGNs explant neurites are inhibited by central glia in vitro and that this effect is not attributed to glia-secreted factors like semaphorins (Pasterkamp and Verhaagen, 2006) or glial cell surface proteins like ephrins (Sandvig et al, 2004), but rather extracellular matrix (ECM) proteins such as CSPGs. CSPG-induced growth inhibition as well as inhibition posed by many other central nervous system (CNS)-derived inhibitory substrates has been shown to signal via ROCK and EGFR pathways (Snow et al, 1994;Lingor et al, 2007; He and Koprivica, 2012).…”

Photopolymerized microfeatures for directed spiral ganglion neurite and Schwann cell growth

“…For CGN cultures, cerebellar cortices were collected from P3–5 rat pups, stripped of arachnoid membranes, and treated with 0.05% trypsin for 12 min at 37°C followed by gentle trituration. Astrocyte (AC) cultures were prepared and maintained from postnatal cerebral cortex according to the modification of a previously described method [37,38]. All neurons were plated on polymer substrates coated with poly-L-ornithine (100 μg/ml) and laminin (20 μg/ml).…”

“…CGN cultures were maintained in Neurobasal-A medium with B-27, 20 μM KCl and NGF 50 ng/ml. AC cultures were maintained as previously described[37]. Cultures were maintained in a humidified incubator with 6.5% CO 2 and fixed with 4% paraformaldehyde after 48 hr.…”

Hearing Loss After Activation of Hearing Preservation Cochlear Implants Might Be Related to Afferent Cochlear Innervation Injury

“…Organotypic cochlear explant cultures including the organ of Corti (OOC) and spiral ganglion were prepared from post natal day 5 (P5) rat pups 15,16 . P5 rat cochleae of both sexes were dissected in ice-cold PBS.…”