Cellular Mechanism of D3 Dopamine-Induced Adult Progenitor/Stem Cell Proliferation in Association with Functional Recovery of Mptp-Induced Parkionsonism Mice Model (I)

Neurogenesis provides an alternative therapeutic manner to treat several neurodegenerative diseases or psychiatric disorders. This cell-based therapy has been profoundly tested in various disease animal models and practically applied in limited non-neural human diseases. In central nervous system, brain transplantation has originally been applied in Parkinson’s disease, however, due to the ethical issue of embryonic tissues and progress of post-operational recovery, the advance of this technique has been severely hampered. In recent years, drug-induced neurogenesis in adult brain has been identified and animal studies proved these new-born neurons could functionally recover the symptoms of pathological disease. For instance, dopamine agonist could promote proliferation of neural stem/progenitor cells in the subventricular zone (SVZ) hence recover the MPTP- or 6-OHDA-induced motor dysfunction. These findings implicate the great potentiality to use drug as non-invasive enhancer to promote in vivo neurogenesis consequently to treat CNS diseases. The current project aims to investigate the ability and mechanism of dopamine D3 (D3R) agonist on neurogenesis in SVZ, due to heavily expressed of D3R in type-C (transit amplifying) SVZ cells. To evaluate its potential application, we will use MPTP-induced Parkinsonism mice model as testing platform to examine if D3R agonist-induced neurogenesis and/or differentiation would rescue the (1) olfaction (early symptom) and (2) motor function of PD. To achieve these purposes, we will first produce and validate MPTP-induced PD animal model in these aspects via various biochemical, anatomical and behavioral tests and compare with D3KO mice. Afterwards, via systemic BrdU injection, we will monitor the progress of new-born cells, identify their phenotype(s) and correlate with functional recovery. Various neural markers, bioassays and functional tests will be applied to obtain a complete profile of adult brain neurogenesis and its functional implication in designated brain area. In order to understand the cellular mechanism of D3R-triggered cell proliferation, we will isolate the progenitor/stem cells from SVZ and cultured in neurospheres. In the cultured condition, we will investigate which cellular pathway(s) and nuclear signal(s) would be activated by D3R to regulate the cell cycle, assisted by flow cytometry analysis and Cdc/Cdk bioassays. To confirm the effect and mechanism of D3R on neural proliferation, neurospheres prepared from SVZ of D3R KO mice as well as PC-12 over-expressed hD3R will be used as positive and negative cell controls. The neuroprotective property of D3R will also be assessed via tests on its therapeutic efficacy against MPP+-induced oxidative damage and/or apoptosis. Further, the effect of MPTP and D3R on neurogenesis in RMS route and olfactory bulb will also be evaluated, in addition to test the impact on olfactory function. In summary, it is expected the study of dopamine D3R ligands on neurogenesis would allow us to gain the research progress in the following aspects: (1) evaluate the ability of D3R activation on progenitor/stem cell proliferation and/or migration, differentiation in the SVZ in naïve and MPTP-treated mice, (2) cellular mechanism of D3R-induced cell proliferation and cell cycle regulation, (3) assess the neuroprotective ability of D3R against MPP+ toxicity in cultured SVZ neurosphere and PC-12/hD3 cells and (4) if MPTP would alter olfactory function and neurogenesis in the olfactory bulb and RMS and reverse by the treatment of D3R agonist.

Project ID:PC9811-0007
External Project ID:NSC98-2321-B182-006