Mutual inhibitory interaction between M1 macrophages and Schwann cells in the myelin sheath of auditory nerves

Abstract

Objectives

To explore the interaction between the M1 macrophages and Schwann cells (SCs) in auditory nerve myelin.

Methods

We conducted co-culture experiments using SCs from the auditory nerve myelin and induced M1 macrophages from 6-week-old C57BL/6 mice. The co-cultured group was set up as an experimental group, while the control groups were assigned as separated cultures of SCs and macrophages alone. The cultured cells were evaluated by cell number and morphology; further, the functions of the cells were detected by the secretion of Brain-Derived Neurotrophic Factor (BDNF) and phagocytic ability.

Results

SCs from the auditory nerve were purified and cultured, showing exponential growth. The BDNF secretion value of SCs was 0.444 ± 0.031 ng/ml. M1 polarization of mouse bone marrow macrophages was successfully induced, and the absorbance value of the macrophages phagocytosis was 0.144 ± 0.003. The co-cultured model presented significant shortening of the spindle-shaped bipolar protrusions of SCs, and the SCs number in co-cultured group was reduced by about 50 % compared with the SCs in control group. the secretion of BDNF value in the co-cultured group was reduced to 0.02 ± 0.007 ng/ml (P < 0.001). In addition, the absorbance value of M1 macrophages phagocytosis in the co-cultured group was significantly reduced to 0.104 ± 0.001 (P < 0.001).

Conclusion

Both M1 macrophages and SCs in auditory nerve myelin were significantly damaged in the co-cultured group.