HoloTransferrin but Not ApoTransferrin Prevents Schwann Cell De-Differentiation in Culture

Abstract

Schwann cells (SCs) in culture, without the presence of axons, become de-differentiated, reaching a condition similar to that of their precursor cells. The cytoplasmic accumulation of transferrin (Tf) in the myelinated peripheral nerve has been reported and data in the literature support a role for apoTf in myelination in the CNS. In the present report, we used SC cultures to evaluate the capacity of apoTf and holoTf to prevent cell de-differentiation promoted by fetal calf serum deprivation. SCs incubated in a serum-free medium showed a decrease in the expression of myelin basic protein (MBP) and P₀, markers of mature myelin-forming SCs, together with an increase in the levels of p75NTR and glial fibrillary acidic protein, markers of immature SCs. Treatment with holoTf prevented the decrease in expression of MBP and P₀ and the increase in p75NTR. ApoTf was unable to prevent these changes except when iron was added to the cultures. These results suggest a role for holoTf in the regulation of myelin formation by SCs.

Iron Homeostasis in Peripheral Nervous System, Still a Black Box?

“…After axotomy, a similar phenomenon occurs also in regenerating motor neurons, which showed a strong increase of TfR1 expression and iron uptake (53). SC dedifferentiation is also dependent on iron availability as demonstrated by the capacity of holo-Tf, but not of apo-Tf, to prevent a decrease in the expression of myelin basic protein (MBP) and myelin protein zero (MPZ) and the increase in immature SC markers (p75 NTR and glial fibrillary acidic protein) following serum deprivation (124). More recently, the same group showed that also Fe 3 + is able to stimulate the differentiation of cultured SCs (123).…”

DMT1 as a candidate for non‐transferrin‐bound iron uptake in the peripheral nervous system

“…We have previously demonstrated that iron, both as ferric ammonium citrate (FAC) and hTf, prevents SC dedifferentiation promoted by serum withdrawal through an increase in cAMP and CREB phosphorylation levels; this was shown to be an essential step in the expression of myelin proteins and a key element in SC maturation . The observations made on cultured SC after iron treatment raised the question of how iron elicits its prodifferentiating effect in the absence of Tf.…”

“…The pellet was resuspended in DMEM+10% FCS and the cells were seeded and kept for 24 H on polylysine‐coated coverslips placed in multiwells (50,000 cells per well) or directly in polylysine‐coated multiwells at a density of approximately 1.5 × 10 6 cells, for immunocytochemical studies or Western blot analysis, respectively. As previously described, culture purity obtained by this method was 95% .…”

“…Our group has previously demonstrated that cultured Schwann cells (SC) incubated in serum‐free medium become dedifferentiated and acquire a phenotype similar to SC precursors and non‐myelin‐forming SC. Holotransferrin (hTf) prevents the dedifferentiation promoted by serum deprivation, while apotransferrin (aTf) is unable to block this effect . We have also shown that, upon treatment of SC with iron, either as NTBI or as TBI, intracellular signals towards differentiation become activated or stabilized through cAMP release, PKA activation, and CREB phosphorylation .…”

Evaluation of recombinant human transferrin (DeltaFerrinTM) as an iron chelator in serum-free media for mammalian cell culture

“…The development and routine use of serum-free media (SFM) is a high priority for cell culture from a scientific point of view where components in traditional sera may complicate research (Salis et al 2002). Industrially, SFM is very important from a regulatory view to reduce or eliminate the use of animal-derived components (Castle and Robertson 1999) thus avoiding contamination with viruses, mycoplasma or prions and for better control of batch-to-batch variation and downstream processing (Chu and Robinson 2001).…”