Wnt5a, produced in mechanically stimulated PDL cells via MEK (1/2) and/or PI3K pathways, promotes neurite elongation

[Speaker] Kaori Takahashi:1
[Co-author] Takashi Yoshida:1, Minoru Wakamori:1
1:Div. Mol. Pharmacol. Cell Biophys., Dept. Oral Biol., Grad Sch. Dent., Tohoku Univ. , Japan

The periodontal ligaments (PDLs), located at the interface between tooth and alveolar bones, are responsible for tooth planting and pressure absorbing actions. The Ruffini's corpuscles, one of the mechanoreceptors, located in the PDLs play a pivotal role in pressure sensing to identify various food properties and adjust occlusal force. Recent studies have shown that branches of Ruffini's corpuscles are not formed without mechanical stimulation in the rat PDL (Shi et al., 2005), and that PDL cells produce neurotrophic factors, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), and the axon guidance protein, Wnt5a (Zhang et al., 2016). Although in the central nerves systems, neurotrophic factors differentiate the neurons and Wnt5a regulates the axsonal elongation, there is no report to assess the regulatory mechanisms of local axonal structure by mechanically stimulated PDL cells. To elucidate the regulatory mechanism, we measured the amounts of neurotrophic factors and axon guidance proteins produced by the mechanically stimulated PDL cells.
We have established primary PDL cell lines derived from rat (rPDL). The RT-PCR analysis confirmed the expression of NGF, BDNF, neurotrophin-4 (NT-4) and Wnt5a in the rPDL cells. The rPDL cells were seeded on silicon chamber, and loaded with periodic mechanical stimulation (0.5Hz, 15% expansion). The qPCR analysis revealed that the expression level of Wnt5a mRNA in rPDL cells was increased in a stimulation-period dependent manner, while that of neurotrophic factors was not changed. LY294002, a PI3K inhibitor, and U0126, a MEK (1/2) inhibitor, diminished the increase of Wnt5a mRNA expression level in the rPDL cells loaded with mechanical stimulation. To analyze biological function of released Wnt5a, the culture media for the primary mouse trigeminal ganglion (mTG) neurons were replaced with the supernatant media of the rPDL cells with or without mechanical stimulation. The supernatant media of the mechanically stimulated rPDL cells enhanced the neurite elongation in the mTG neurons and this effect was suppressed by anti-Wnt5a antibody.
These results suggest that the mechanical stimulation to the PDL cells produces Wnt5a via MEK (1/2) and/or PI3K pathways and the Wnt5a secreted from PDL cells elongates the axon.

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