TREM2 Gene Induces Differentiation of Induced Pluripotent Stem Cells into Dopaminergic Neurons and Promotes Neuronal Repair Via TGF-β Activation in 6-Ohda-lesioned Mouse Model of Parkinson's Disease

Objective: Induced pluripotent stem cells (iPSCs) hold a promising potential for rescuing dopaminergic neurons in therapy for Parkinson's disease (PD). This study clarifies a TREM2-dependent mechanism explaining the function of iPSC differentiation in neuronal repair of PD. Methods: PD-related differentially expressed genes were screened by bioinformatics analyses and their expression was verified using RT-qPCR in nigral tissues of 6-OHDA-lesioned mice. Following ectopic expression and depletion experiments in iPSCs, cell differentiation into dopaminergic neurons as well as the expression of dopaminergic neuronal markers TH and DAT was measured. Stereotaxic injection of 6-OHDA was used to develop a mouse model of PD, which was injected with iPSC suspension overexpressing TREM2 to verify the effect of TREM2 on neuronal repair. Results: TREM2 was poorly expressed in the nigral tissues of 6-OHDA-lesioned mice. In the presence of TREM2 overexpression, the iPSCs showed increased expression of dopaminergic neuronal markers TH and DAT, which facilitated the differentiation of iPSCs into dopaminergic neurons. Mechanistic investigations indicated that TREM2 activated the TGF-beta pathway and induced iPSC differentiation into dopaminergic neurons. In vivo data showed that iPSCs overexpressing TREM2 enhanced neuronal repair in 6-OHDA-lesioned mice. Conclusion: This work identifies a mechanistic insight for TREM2-mediated TGF-beta activation in the regulation of neuronal repair in PD and suggests novel strategies for neurodegenerative disorders.