L'Episcopo Francesca, Tirolo Cataldo, Testa Nunzio, Caniglia Salvatore, Morale Maria Concetta, Serapide Maria Francesca, Pluchino Stefano, Marchetti Bianca
Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Neuropharmacology Section, Troina, Enna, Italy.
Stem Cells. 2014 Aug;32(8):2147-63. doi: 10.1002/stem.1708.
Wnt/β-catenin signaling is required for specification and neurogenesis of midbrain dopaminergic (mDA) neurons, the pivotal neuronal population that degenerates in Parkinson's disease (PD), and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Wnt/β-catenin signaling plays a vital role in adult neurogenesis but whether it might engage DA neurogenesis/neurorepair in the affected PD brain is yet unresolved. Recently, the adult midbrain aqueduct periventricular regions (Aq-PVRs) were shown to harbor multipotent clonogenic neural stem/progenitor cells (mNPCs) with DA potential in vitro, but restrictive mechanisms in vivo are believed to limit their DA regenerative capacity. Using in vitro mNPC culture systems we herein demonstrate that aging is one most critical factor restricting mNPC neurogenic potential via dysregulation of Wnt/β-catenin signaling. Coculture paradigms between young/aged (Y/A) mNPCs and Y/A astrocytes identified glial age and a decline of glial-derived factors including Wnts as key determinants of impaired neurogenic potential, whereas Wnt activation regimens efficiently reversed the diminished proliferative, neuronal, and DA differentiation potential of A-mNPCs. Next, in vivo studies in wild (Wt) and transgenic β-catenin reporter mice uncovered Wnt/β-catenin signaling activation and remarkable astrocyte remodeling of Aq-PVR in response to MPTP-induced DA neuron death. Spatio-temporal analyses unveiled β-catenin signaling in predopaminergic (Nurr1(+)/TH(-)) and imperiled or rescuing DAT(+) neurons during MPTP-induced DA neuron injury and self-repair. Aging inhibited Wnt signaling, whereas β-catenin activation in situ with a specific GSK-3β antagonist promoted a significant degree of DA neurorestoration associated with reversal of motor deficit, with implications for neurorestorative approaches in PD.
Wnt/β-连环蛋白信号通路对于中脑多巴胺能（mDA）神经元的特化和神经发生至关重要，mDA神经元是帕金森病（PD）中退化的关键神经元群体，在PD的1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）小鼠模型中也是如此。Wnt/β-连环蛋白信号通路在成体神经发生中起着至关重要的作用，但它是否参与受影响的PD大脑中的多巴胺能神经发生/神经修复尚未得到解决。最近，研究表明成年中脑导水管周围区域（Aq-PVRs）在体外含有具有多巴胺能潜力的多能克隆神经干细胞/祖细胞（mNPCs），但体内的限制机制被认为限制了它们的多巴胺能再生能力。我们在此使用体外mNPC培养系统证明，衰老通过Wnt/β-连环蛋白信号通路失调成为限制mNPC神经发生潜力的最关键因素之一。年轻/老年（Y/A）mNPCs与Y/A星形胶质细胞之间的共培养模式确定了胶质细胞年龄以及包括Wnts在内的胶质细胞衍生因子的减少是神经发生潜力受损的关键决定因素，而Wnt激活方案有效地逆转了老年mNPCs增殖、神经元和多巴胺能分化潜力的降低。接下来，在野生（Wt）和转基因β-连环蛋白报告基因小鼠中的体内研究发现，Wnt/β-连环蛋白信号通路激活以及Aq-PVR中显著的星形胶质细胞重塑以应对MPTP诱导的多巴胺能神经元死亡。时空分析揭示了在MPTP诱导的多巴胺能神经元损伤和自我修复过程中，前多巴胺能（Nurr1(+)/TH(-)）以及受损或恢复的多巴胺转运体（DAT(+)）神经元中的β-连环蛋白信号通路。衰老抑制Wnt信号通路，而用特异性GSK-3β拮抗剂原位激活β-连环蛋白可促进与运动功能障碍逆转相关的显著程度的多巴胺能神经修复，这对PD的神经修复方法具有重要意义。
