Netrin-1 marshals mitochondrial movement, morphology, and metabolism in myelin

Identifying mRNAs Residing in Myelinating Oligodendrocyte Processes as a Basis for Understanding Internode Autonomy

In elaborating and maintaining myelin sheaths on multiple axons/segments, oligodendrocytes distribute translation of some proteins, including myelin basic protein (MBP), to sites of myelin sheath assembly, or MSAS. As mRNAs located at these sites are selectively trapped in myelin vesicles during tissue homogenization, we performed a screen to identify some of these mRNAs. To confirm locations, we used real-time quantitative polymerase chain reaction (RT-qPCR), to measure mRNA levels in myelin (M) and ‘non-myelin’ pellet (P) fractions, and found that five (LPAR1, TRP53INP2, TRAK2, TPPP, and SH3GL3) of thirteen mRNAs were highly enriched in myelin (M/P), suggesting residences in MSAS. Because expression by other cell-types will increase p-values, some MSAS mRNAs might be missed. To identify non-oligodendrocyte expression, we turned to several on-line resources. Although neurons express TRP53INP2, TRAK2 and TPPP mRNAs, these expressions did not invalidate recognitions as MSAS mRNAs. However, neuronal expression likely prevented recognition of KIF1A and MAPK8IP1 mRNAs as MSAS residents and ependymal cell expression likely prevented APOD mRNA assignment to MSAS. Complementary in situ hybridization (ISH) is recommended to confirm residences of mRNAs in MSAS. As both proteins and lipids are synthesized in MSAS, understanding myelination should not only include efforts to identify proteins synthesized in MSAS, but also the lipids.

Bone Marrow Mesenchymal Stem Cells (BMSCs) Expressing Netrin-1 Alleviates Spinal Cord Injury (SCI)-Induced Inflammation

Spinal cord injury (SCI) is a common central nervous system (CNS) injury. Bone marrow mesenchymal stem cells (BMSCs) transplantation is a potential treatment for traumatic SCI. However, the role and mechanism of BMSCs with high expression of Netrin-1 on the repair and inflammation of spinal cord injury cells remains unclear. Our study intends to assess the effect of BMSCs with high Netrin-1 level on the repair of SCI cells. BMSCs or Netrin-1 transfected BMSCs were co-cultured with mechanically injured nerve cells followed by analysis of the differentiation of BMSCs by light microscope, apoptosis activity, expression of TLR-4 and NF-κB, and the TNF-α and IL-1β content in cell supernatant by ELISA. BMSCs with high Netrin-1 expression promoted the proliferation of BMSCs, inhibited apoptosis, and promoted the differentiation of nerve cells along with increased ALK activity, and the expression of GFAP and BDNF. Co-culture with BMSCs or BMSCs with high Netrin-1 expression increased mechanically damaged nerve cell proliferation, decreased apoptosis, downregulated TLR-4 and NF-κB (P < 0.05) with more significant changes after co-culture with BMSCs with high Netrin-1 expression. In conclusion, Netrin-1 can promote BMSCs proliferation and differentiation, and inhibit apoptosis. By inhibiting inflammation, it can promote damaged nerve cell proliferation and repair.