Glial cells promote dendritic development in rat sympathetic neurons in vitro

Abstract

Many types of glial-neuronal interactions occur during the development of the nervous system. To determine how such interactions might affect the development of autonomic ganglia, we compared the morphology of embryonic rat sympathetic neurons grown in the absence and in the presence of ganglionic nonneuronal cells in serum-free medium. Dye injections, electron microscopy, and immunocytochemistry were used to distinguish axons from dendrites. In cultures without nonneuronal cells, most (greater than 80%) sympathetic neurons extended only a single axonal process, and this unipolar state persisted for at least 8 weeks. Coculture with ganglionic nonneuronal cells caused sympathetic neurons to become multipolar and to extend multiple (range 1-17) dendrites. Morphometric measurements made after 1 month of coculture indicated that the amount of dendritic growth that occurred in vitro (mean number of dendrites/cell = 7.5; total dendritic length = 1,050 micron) was similar to that normally occurring during a comparable period in situ. In contrast to its prominent effects on dendritic growth, coculture did not cause changes in the number of axons/neuron or in the uptake of neurotransmitter. Cultures with ganglionic nonneuronal cells were immunostained for antigens present on the surfaces of fibroblasts (Thy-1.1, fibronectin) and of glia of the peripheral nervous system (laminin). Fewer than 1% of the nonneuronal cells displayed immunoreactivity for fibroblastic antigens; in contrast, greater than or equal to 99% reacted with antibody to laminin. Moreover, reconstitution experiments revealed that purified populations of laminin-positive Schwann cells promoted dendritic growth. Fibroblasts and heart cells lacked this activity. These data indicate that glia selectively promote dendritic development in sympathetic neurons maintained in serum-free medium.

NGF induces neonatal rat sensory neurons to extend dendrites in culture after removal of satellite cells

“…The mechanism by which the satellite cells operate has not been determined. Interestingly, this satellite cell influence on sensory neurons is opposite to the influence of glial cells on neurons that normally extend dendrites in vivo (Tropea et al, 1988;Johnson et al, 1989;Clendening and Hume, 1990); in these latter studies, the presence of glial cells induces dendrite outgrowth. Therefore, with respect to dendrites, these results suggest that, in culture, glial cells influence neurons to acquire properties that they would normally have in vivo.…”

“…To test whether these effects of NGF on process outgrowth were specific for the initiation of dendrites and not axons, we filled individual neurons with Lucifer yellow and measured the number of axons emerging from the soma after 1,2, and 3 weeks in culture. We classified thin processes of constant caliber that could be followed for several hundred microns as axons, whereas dendrites were classified as thick, tapered processes that ended locally (Bruckenstein and Higgins, 1988a,b;Tropea et al, 1988) (see Tables 1, 2). The results from these experiments indicate that the number of axons emerging from the somata did not increase significantly from week 1 to week 3 in culture, independent of the presence of NGF.…”

“…Recent studies have indicated that the initiation of dendrites is, in part, governed by mechanisms intrinsic to neurons (Dotti et al, 1988;Black and Baas, 1989). In addition, there is ample evidence that extrinsic factors influence neuronal polarity and dendritic arborization (Mudge, 1984;Bruckenstein and Higgins, 1988a,b;Purves et al, 1988;Snider, 1988;Tropea et al, 1988;Chamak and Prochiantz, 1989;Johnson et al, 1989;Lein and Higgins, 1989;Clendening and Hume, 1990;&hilling et al, 1991).…”

Aberrant development of motor axons and neuromuscular synapses in erbB2-deficient mice

“…Although synapses were formed in the intercostal muscle, normal junctional folding was not observed in the mutants. Schwann cells have been shown to affect terminal arborization (32) and axon caliber (22) in vitro. The absence of Schwann cells in erbB2-deficient embryos may contribute to these axonal and synaptic defects.…”

The Novel GTPase Rit Differentially Regulates Axonal and Dendritic Growth

“…The most significant difference is that in contrast to hippocampal neurons, sympathetic neurons derived from embryonic rat superior cervical ganglia extend only a single axonal process during the first 24 h in culture, and when these neurons are grown in serum-free medium in the absence of non-neuronal cells, this polarity is maintained for up to 3 months in culture (Bruckenstein and Higgins, 1988). Dendritic growth in sympathetic neurons requires extrinsic cues: coculture with glial cells (Tropea et al, 1988;Lein et al, 2002) or exposure to BMPs in the presence of NGF (Lein et al, 1995) triggers these neurons to form multiple dendrites in addition to a single axon. Thus, to determine whether Rit signaling represents a divergent or convergent mechanism for regulating axonal versus dendritic growth modes in diverse neuronal cell types, we first determined whether Rit is expressed endogenously in sympathetic neurons and then analyzed the effects of manipulating Rit activation on axonal and dendritic growth in sympathetic neurons.…”