miR-199a-3p suppresses neuroinflammation by directly targeting MyD88 in a mouse model of bone cancer pain

Aims: Pain is a profoundly debilitating symptom in cancer patients, leading to disability, immobility, and a
marked decline in their quality of life. This study aimed to investigate the potential roles of miR-199a-3p in a
murine model of bone cancer pain induced by tumor cell implantation in the medullary cavity of the femur.
Materials and methods: We assessed pain-related behaviors, including the paw withdrawal mechanical threshold
(PWMT) and the number of spontaneous flinches (NSF). To investigate miRNA expression and its targets in
astrocytes, we employed a combination of RNA-seq analysis, qRT-PCR, Western blotting, EdU, TUNEL, ChIP,
ELISA, and luciferase reporter assays in mice (C3H/HeJ) with bone cancer pain and control groups.
Key findings: On days 10, 14, 21, and 28 post-surgery, we observed significant differences in PWTL, PWMT, and
NSF when compared to the sham group (P <0.001). qRT-PCR assays and miRNA sequencing results confirmed
reduced miR-199a-3p expression in astrocytes of mice with bone cancer pain. Gain- and loss-of-function experiments
demonstrated that miR-199a-3p suppressed astrocyte activation and the expression of inflammatory
cytokines. In vitro investigations revealed that miR-199a-3p mimics reduced the levels of inflammatory factors in
astrocytes and MyD88/NF-κB proteins. Furthermore, treatment with a miR-199a-3p agonist resulted in reduced
expression of MyD88, TAK1, p-p65, and inflammatory mediators, along with decreased astrocyte activation in
the spinal cord.
Significance: Collectively, these findings demonstrate that upregulation of miR-199a-3p may offer a therapeutic
avenue for mitigating bone cancer pain in mice by suppressing neuroinflammation and inhibiting the MyD88/
NF-κB signaling pathway.