Journal of Neuroscience, Vol 15, 262-273, Copyright © 1995 by Society for Neuroscience
Transforming growth factor-beta 1 and forskolin modulate gap junctional communication and cellular phenotype of cultured Schwann cells
KJ Chandross, M Chanson, DC Spray and JA Kessler
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461.
Following peripheral nerve injury, Schwann cells undergo a series of
cellular alterations that are thought to assist the regenerative process.
Some of these changes are stimulated by the local release of cytokines and
mitogenic factors. To test the hypothesis that cytokine regulation of gap
junctional communication between cells helps to coordinate Schwann cell
responses, cultured rat Schwann cells, from sciatic nerve, were utilized to
study phasic changes induced by transforming growth factor-beta 1 (TGF beta
1), a cytokine released after nerve injury, or forskolin in combination
with bovine pituitary extract (F-BPE), known for its mitogenic effects in
vitro. In mitotically quiescent cultures, TGF beta 1 significantly
decreased both electrical and dye coupling mediated by gap junctions.
Single-channel analysis revealed that cultured Schwann cells expressed gap
junctions with two distinct channel sizes of about 26 pS and 44 pS. TGF
beta 1 treatment reduced coupling due to both populations of channels.
Exposure to TGF beta 1 had a minimal effect on proliferation but
significantly altered cellular morphology; cell bodies became flattened
with multipolar processes within 72 hr. Additionally, immunolabeling for
both low-affinity nerve growth factor receptor (L-NGFR) and glial
fibrillary acidic protein (GFAP) were reduced, suggesting increased
differentiation. In contrast, treatment with F-BPE significantly enhanced
both electrical and dye coupling and stimulated Schwann cell proliferation.
Additionally, cell bodies became more rounded with polarized, cytoplasmic
processes contiguously aligned with adjacent cells. F-BPE reduced
immunolabeling for L-NGFR but increased expression of both GFAP and the
major peripheral myelin protein, P0. These data indicate that TGF beta 1
and/or F-BPE induce phenotypic changes in Schwann cells, including the
coordinated regulation of proliferation and modulation of intercellular
communication via gap junctions. Such mechanisms may underlie phasic
responses that orchestrate recovery from nerve injury, indicating that
Schwann cell gap junctions may be critical for peripheral nerve function.