Using Stem Cells in Animal Models of Parkinson's Disease

帕金森病(PD)的一种有希望的新疗法包括用来自移植的胎儿中脑组织的黑质纹状体神经元替换退化的黑质纹状体神经元。尽管这种方法经常在大鼠和猴子身上产生显著的功能恢复，但在帕金森病患者的临床试验中，结果并不那么一致。有争议的是，在人类胚胎移植中，一些关键因素相对无法标准化，包括被移植细胞的年龄、类型、数量和完整性。因此，为移植寻找更可靠的多巴胺(DA)组织来源变得越来越重要。一个方向是寻找一系列容易获得、特征良好的不断自我更新的干细胞或前体细胞，这些干细胞或前体细胞具有分化为DA神经元的能力，理想情况下是自发的，不需要太多的操作，从而提供取之不尽、用之不竭的替代组织来源。为此，我们的初步发现表明，C17.2细胞的胚胎小鼠神经干细胞(NSCs)移植到帕金森病大鼠的大脑中时，可以完全分化为神经元，在大多数情况下，神经元可以表达DA特征。此外，在使用成人骨髓干细胞(MSCs)进行的初步研究中，我们发现近100%的MSCs在与特定分化因子孵育1-2小时后就会转化为具有加工能力的β-微管蛋白III神经元样细胞。如果这些细胞在体内也表现出与神经干细胞相同的能力，对适当的DA分化信号做出反应，患者就可以为帕金森病患者的自体移植提供自己的干细胞来源。使用NSC和MSC干细胞模型和多学科方法，我们对这项建议的具体目标有三个：1)确定促进在培养中生长的干细胞中稳定出现有丝分裂后分化的DA表型的条件；2)确定促进移植干细胞中DA表型分化的因素；3)确定移植干细胞中的DA表型是否稳定和持久，以及它是否能够在帕金森病大鼠模型中产生运动障碍的功能恢复。这项研究计划的最终目标是更全面地了解调节干细胞中DA特征分化的细胞和分子过程，并将这些知识应用于帕金森氏病的移植治疗策略。

One promising new therapy for Parkinson's Disease (PD) involves the replacement of degenerated nigrostriatal neurons with those derived from transplanted fetal mesencephalic tissue. Although this approach has often yielded remarkable recovery of function in rats and monkeys, results in clinical trials with PD patients have been less consistent. At issue, is the relative inability to standardize a number of critical factors in human fetal transplants, including the age, type, number and integrity of cells being grafted. Consequently, finding more reliable sources of dopaminergic (DA) tissue for transplantation has become increasingly important. One direction has been to search for a line of readily available, well-characterized continually self-renewing stem or precursor cells that possess the capacity to differentiate, ideally spontaneously and with the need for little manipulation, into DA neurons, thus providing an inexhaustible and uniform source of replacement tissue. Towards this end, our preliminary findings demonstrate that grafts of embryonic mouse neural stem cells (NSCs) of the C17.2 cell can differentiate exclusively into neurons, which in a majority of cases, can express DA traits when cells are transplanted into the brain of a Parkinsonian rat. In addition, in preliminary studies using stem cells from adult human bone marrow (MSCs), we have found that nearly 100 percent of MSCs will convert into process- bearing, beta-tubulin III+ neuronal-like cells after only 1-2 hours of incubation with specific differentiation factors. If these cells also exhibit the same capacity as NSCs to respond to appropriate DA differentiation cues in vivo, patients could provide their own source of stem cells for autologous grafts in PD. Using NSC and MSC stem cell models and a multidisciplinary approach, our specific goals for this proposal are threefold: 1) Identify the conditions that promote the stable appearance of a postmitotic differentiated DA phenotype in stem cells grown in culture; 2) Identify those factors which promote the differentiation of a DA phenotype in transplanted stem cells and 3) Determine whether the DA phenotype in transplanted stem cells is stable and long lasting, and whether, it can produce functional recovery of motor deficits in a rat model of PD. The ultimate goal of this research program is a fuller understanding of the cellular and molecular processes regulating the differentiation of DA traits in stem cells and apply that knowledge to transplantation strategies for the treatment of Parkinson's Disease.