1 Department of Medicine, University of Texas Health San Antonio , San Antonio, Texas.
2 Stem Cells Research Center and Department of Pathology, Guizhou Medical University , Guiyang, Guizhou, China .
Stem Cells Dev. 2018 Jul 15;27(14):995-1005. doi: 10.1089/scd.2018.0030. Epub 2018 Apr 23.
Glial cell line-derived neurotrophic factor (GDNF) exhibits potent neuroprotective properties in preclinical models of Parkinson's disease (PD), but challenges in GDNF delivery have been reported from clinical trials. To address this barrier, we developed a hematopoietic stem cell transplantation-based macrophage-mediated GDNF therapy platform. Here, we introduced a regulatable lentiviral vector (LV-MSP-Tet-Off-hGDNF) to allow the expression of human GDNF (hGDNF) to be adjusted or stopped by oral administration of doxycycline (Dox). C57BL/6J mice were lethally irradiated with head protection and then transplanted with syngeneic bone marrow cells transduced with either the hGDNF-expressing vector or a corresponding GFP-expressing vector, LV-MSP-Tet-Off-GFP. Suppression of vector gene expression was achieved through administration of Dox in drinking water. To create a toxin-induced Parkinsonian model, mice were injected in two cycles with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) to yield nigral cell/striatal dopamine loss and behavioral deficits. During the presence of Dox in the drinking water, plasma GDNF was at a basal level, whereas during the absence of Dox, plasma GDNF was significantly elevated, indicating reliable regulation of therapeutic gene expression. Midbrain GDNF levels were altered in parallel, although these did not return completely to basal levels during the periods of Dox withdrawal. Motor activities of the MPTP-Tet-off-hGDNF group were comparable to those of the Tet-off-GFP (subject to no MPTP treatment) group, but substantially better than those of the MPTP-Tet-off-GFP group. Interestingly, the improvement in motor activities was sustained during the Dox-withdrawn periods in MPTP-Tet-off-hGDNF animals. Neuroprotection by therapeutic GDNF expression was further evidenced by significant amelioration of nigral tyrosine hydroxylase loss after both the first and second MPTP treatment cycles. These data suggest that neurotrophic factor expression can be upregulated to achieve efficacy or downregulated in case of off-target effects or adverse events, a feature that may eventually increase the acceptance of this potentially neuroprotective/disease-modifying PD therapy.
胶质细胞源性神经营养因子（GDNF）在帕金森病（PD）的临床前模型中表现出强大的神经保护特性，但临床试验中也报告了 GDNF 传递的挑战。为了解决这一障碍，我们开发了一种基于造血干细胞移植的巨噬细胞介导的 GDNF 治疗平台。在这里，我们引入了一种可调节的慢病毒载体（LV-MSP-Tet-Off-hGDNF），允许通过口服强力霉素（Dox）来调节或停止人 GDNF（hGDNF）的表达。C57BL/6J 小鼠头部受到致死性照射，然后移植用表达 hGDNF 的载体或相应的 GFP 表达载体 LV-MSP-Tet-Off-GFP 转导的同源骨髓细胞。通过在饮用水中给予 Dox 来实现载体基因表达的抑制。为了建立毒素诱导的帕金森病模型，小鼠分两个周期接受 MPTP（1-甲基-4-苯基-1,2,3,6-四氢吡啶）注射，导致黑质细胞/纹状体多巴胺丢失和行为缺陷。在饮用水中存在 Dox 的情况下，血浆 GDNF 处于基础水平，而在没有 Dox 的情况下，血浆 GDNF 显著升高，表明治疗性基因表达的可靠调节。中脑 GDNF 水平也发生了变化，尽管在 Dox 停药期间并未完全恢复到基础水平。MPTP-Tet-off-hGDNF 组的运动活动与 Tet-off-GFP（未接受 MPTP 治疗）组相当，但明显优于 MPTP-Tet-off-GFP 组。有趣的是，在 MPTP-Tet-off-hGDNF 动物的 Dox 停药期间，运动活动的改善得以维持。通过第一和第二 MPTP 治疗周期后黑质酪氨酸羟化酶丢失的显著改善，进一步证明了治疗性 GDNF 表达的神经保护作用。这些数据表明，神经营养因子表达可以上调以实现疗效，或者在出现脱靶效应或不良反应的情况下下调，这一特征最终可能会增加这种潜在的神经保护/疾病修饰 PD 治疗的接受度。
