Lithium Reversibly Inhibits Schwann Cell Proliferation and Differentiation Without Inducing Myelin Loss

Abstract

This study was undertaken to examine the bioactivity, specificity and reversibility of lithium’s action on the growth, survival, proliferation and differentiation of cultured Schwann cells (SCs). In isolated SCs, lithium promoted a state of cell cycle arrest that featured extensive cell enlargement and c-Jun downregulation in the absence of increased expression of myelin-associated markers. In addition, lithium effectively prevented mitogen-induced S-phase entry without impairing cell viability. When lithium was administered together with differentiating concentrations of cAMP analogs, a dramatic inhibition of the expression of the master regulator of myelination Krox-20 was observed. Likewise, lithium antagonized the cAMP-dependent expression of various myelin markers such as protein zero, periaxin and galactocerebroside and allowed SCs to maintain high levels of expression of immature SC markers even in the presence of high levels of cAMP and low levels of c-Jun. Most importantly, the inhibitory action of lithium on SC proliferation and differentiation was shown to be dose dependent, specific and reversible upon removal of lithium compounds. In SC-neuron cultures, lithium suppressed myelin sheath formation while preserving axonal integrity, SC-axon contact and basal lamina formation. Lithium was unique in its ability to prevent the onset of myelination without promoting myelin degradation or SC dedifferentiation. To conclude, our results underscored an unexpected antagonistic action of lithium on SC mitogenesis and myelin gene expression. We suggest that lithium represents an attractive pharmacological agent to safely and reversibly suppress the onset of SC proliferation, differentiation and myelination while maintaining the integrity of pre-existing myelinated fibers.

Phenotypic and Functional Characteristics of Human Schwann Cells as Revealed by Cell-Based Assays and RNA-SEQ

“…SCs were prepared from the sciatic nerves of three months-old male Fisher rats by a modification of a previously reported method, as described recently in [17]. The sciatic nerves of 4 animals were processed together to obtain a large enough population of SCs for cryopreservation at early passage.…”

“…Purified embryonic rat DRG neurons (dissociated, day 15) were established essentially as described previously in [17]. Briefly, the DRG bodies were dissected out from the embryos and enzymatically dissociated with 0.25% trypsin (37°C, 45 min).…”

Heregulin Activity Assays for Residual Testing of Cell Therapy Products

“…ErbB3 (~ 200 kDa), Akt (~ 70 kDa) and ERK1/2 (~ 44/42 kDa) are resolved very clearly by SDS-PAGE and can be detected on the same Western blot membrane using validated, highly selective total and phospho-specific antibody combinations that do not cross-react with other antigens. Expanded adult rat SCs (normal, established from nerve-derived primary cells) were chosen for the stimulation experiments because consistent responses to soluble β1-heregulin were expected [ 12 , 19 , 20 ]. Adult rat SCs constitutively express ErbB2 and ErbB3, which dimerize to form a functional heregulin co-receptor (Fig.…”

“…1 ), and are highly responsive to β1-heregulin with the induction of proliferation (Fig. 2 c), [ 11 , 12 , 20 ]. The responses of adult rat SCs to β1-heregulin are rapid, potent and specific to ErbB2/3 activation (Fig.…”

Inhibition of RhoA-Subfamily GTPases Suppresses Schwann Cell Proliferation Through Regulating AKT Pathway Rather Than ROCK Pathway

“…Since SCs are important glial cells in peripheral nerve and they have attractive application prospects in cell transplantation for the therapy of nervous system injury, the biology and application of SCs have been attracting a great deal of attention (Belin et al, 2017 ). Recent decades, lots of publications focused on the study of SC proliferation (Atanasoski et al, 2004 ; Deng et al, 2017 ; Pan et al, 2017 ; Piñero et al, 2017 ). As molecular switches that control the organization and dynamics of the actin cytoskeleton, Rho GTPases are considered to be key regulators of proliferation of various cells (Hu et al, 2014 ; Wang et al, 2014 ).…”