| The saltatory conduction of axon signals depends on the structure of myelin. Myelin was formed by mature oligodendrocyte which extended their protrusions around the axon for dozens of layers. It also plays important roles in the maintenance and protection of axonal integrity. Myelin is critical for nervous system to function and behave normally.Mature oligodendrocyte is developed from Oligodendrocyte Precursor Cells (OPC). OPC must experience proliferation, migration and differentiation in the embryonic development before they become mature and ensheath/myelinating the axons. The first wave of OPC originates from subventricular zone (SVZ) in the encephalon and precursor motor neuron (pMN) zone in the spinal cord. Then they migrate extensively and distribute all around the central nervous system (CNS) in a short and specific period. OPC are highly motivated cells either in vivo or in vitro. Enormous numbers of factors are identified affecting OPC migration, yet the migration pathway and molecular mechanisms remain poorly defined. There are many diseases related with myelin dysfunction which including traumatic injury, demyelination disease, Alzheimer's disease etc. The common character of these diseases is myelin damage. To treat these diseases, both decreasing on-going damage and increasing recovery are needed. Previous studies showed there were automatically recovery mechanisms in patients which called remyelination. In the process of remyelination, OPC repeated the migration, differentiation and myelination steps in development. Migration is the first step to accomplish in order to recover myelin structure. Obviously promoting OPC migration will accelerate the process of remyelination. From above it can be concluded that studying the migration character of OPC would be meaningful in either physiology or pathology perspective.Methylprednisolone (Mep) is clinical drug for treating spinal cord injury (SCI) and multiple sclerosis (MS). Mep is a chemically composed analog of glucocorticoid and act as immune mediator. Mep can protect the nervous system from immune attacking and decrease myelin damage by inhibiting immune response and inflammation. It is highly possible that Mep play other roles in the disease recovery. It would be meaningful to study the effects of Mep on oligodendrocyte such as migration.This study shows for the first time that Mep can promote OPC migration in a glucocorticoid receptor (GR) and ERK1/2 dependent manner.The results are as following:1. Establish the OPC in vitro culture system. The cells is characterized the same as reported. Classically they are bipolar, immunostaining NG2+ and A2B5+. They are able to differentiate into O4+,01+ or MBP+ oligodendrocyte linage cells.2. Mep promotes OPC migration. Using transwell model the Mep significantly promotes OPC migration in the concentration of 100nM and 1 u M. In matrigel migration assay, cell number that migrate out of aggregations significantly increases after treating with 1μM Mep.3. The proliferation rate of OPC is not affected by Mep. BrdU incorporation assay shows that after incorporating BrdU for 4 hours, the BrdU positive rate is about 30% either in or out of the presence of Mep.4. OPC express glucocorticoid receptor. Glucocorticoid receptor can be detected through RT-PCR, Western-blot or cell immunostaining methods.5. The promotion effect of Mep on OPC is GR dependent. The glucocorticoid antagonist Ru38486 can block the promotion effect of Mep on OPC migration in transwell assay. Corticosterone, the nature ligand of GR, has the similar potential to promote OPC migration like Mep.6. The promotion effect of Mep on OPC migration is regulated by ERK pathway. Western blot shows Mep can activates ERK1/2 for longer than 4 hours. The antagonist of ERK pathway PD98059 blocked the effect of Mep. But the antagonist of JNK does not function. |
PDF Full Text Request