Lorraine Iacovitti

Dopaminergic Neurons Derived from Human Induced Pluripotent Stem Cells Survive and Integrate into 6-OHDA-Lesioned Rats

Cell replacement therapy could be an important treatment strategy for Parkinsons disease (PD), which is caused by the degeneration of dopamine neurons in the midbrain (mDA). The success of this approach greatly relies on the discovery of an abundant source of cells capable of mDAergic function in the brain. With the paucity of available human fetal tissue, efforts have increasingly focused on renewable stem cells. Human induced pluripotent stem (hiPS) cells offer great promise in this regard. If hiPS cells can be differentiated into authentic mDA neuron, hiPS could provide a potential autologous source of transplant tissue when generated from PD patients, a clear advantage over human embryonic stem (hES) cells. Here, we report that mDA neurons can be derived from a commercially available hiPS cell line, IMR90 clone 4, using a modified hES differentiation protocol established in our lab. These cells express all the markers (Lmx1a, Aldh1a1, TH, TrkB), follow the same mDA lineage pathway as H9 hES cells, and have similar expression levels of DA and DOPAC. Moreover, when hiPS mDA progenitor cells are transplanted into 6-OHDA-lesioned PD rats, they survive long term and many develop into bona fide mDA neurons. Despite their differentiation and integration into the brain, many Nestin+ tumor-like cells remain at the site of the graft. Our data suggest that as with hES cells, selecting the appropriate population of mDA lineage cells and eliminating actively dividing hiPS cells before transplantation will be critical for the future success of hiPS cell replacement therapy in PD patients.

A protocol for the differentiation of human embryonic stem cells into dopaminergic neurons using only chemically defined human additives: Studies in vitro and in vivo

Our ability to use human embryonic stem (hES) cells in cell replacement therapy for Parkinsons disease depends on the discovery of ways to simply and reliably differentiate a dopaminergic (DA) phenotype in these cells. Although several protocols exist for the differentiation of DA traits in hES, they involve the prolonged use of complex media with undefined components, cell conditioned media and/or co-culture with various cells, usually of animal origin. In this study, several well-characterized (H9, BG01) and several new uncharacterized (HUES7, HUES8) hES cell lines were studied for their capacity to differentiate into DA neurons in culture using a novel rapid protocol which uses only chemically-defined human-derived media additives and substrata. Within 3 weeks, cells from all 4 cell lines progressed from the undifferentiated state to beta-tubulin III positive cells expressing DA markers in vitro. Moreover, transplantation of these cells into the striata of 6-hydroxydopamine-treated rats at the neuronal progenitor stage resulted in the appearance of differentiated DA traits in vivo 2-3 weeks later.

Circumventricular Organs: A Novel Site of Neural Stem Cells in the Adult Brain

Neurogenesis in the adult mammalian nervous system is now well established in the subventricular zone of the anterolateral ventricle and subgranular zone of the hippocampus. In these regions, neurons are thought to arise from neural stem cells, identified by their expression of specific intermediate filament proteins (nestin, vimentin, GFAP) and transcription factors (Sox2). In the present study, we show that in adult rat and mouse, the circumventricular organs (CVOs) are rich in nestin+, GFAP+, vimentin+ cells which express Sox2 and the cell cycle-regulating protein Ki67. In culture, these cells proliferate as neurospheres and express neuronal (doublecortin+, beta-tubulin III+) and glial (S100beta+, GFAP+, RIP+) phenotypic traits. Further, our in vivo studies using bromodeoxyuridine show that CVO cells proliferate and undergo constitutive neurogenesis and gliogenesis. These findings suggest that CVOs may constitute a heretofore unknown source of stem/progenitor cells, capable of giving rise to new neurons and/or glia in the adult brain.

Neural Stem Cells Spontaneously Express Dopaminergic Traits after Transplantation into the Intact or 6-Hydroxydopamine-Lesioned Rat

The ability to differentiate neural stem cells (NSCs) into dopamine neurons is fundamental to their role in cell replacement therapies for neurodegenerative disorders such as Parkinsons disease. We show here that when a clonal line (C17.2) of undifferentiated NSCs is transplanted into the intact or 6-hydroxydopamine-lesioned striatum, cells withdraw from the cell cycle (BrdU(-)), migrate extensively in the host striatum, and express markers associated with neuronal (beta-tubulin III(+), NSE(+), NeuN(+)) but not glial (GFAP(-), MBP(-), A2B5(-)) differentiation. Importantly, by 2-5 weeks postgrafting, in the majority of these transplants, nearly all engrafted cells express the dopamine-synthesizing enzymes tyrosine hydroxylase and aromatic L-amino decarboxylase, sometimes resulting in changes in motor behavior. In contrast, no NSCs stain for dopamine-beta-hydroxylase, choline acetyltransferase, glutamic acid decarboxylase, or serotonin. We conclude that, following transplantation into the intact or 6-hydroxydopamine-lesioned rat, the adult brain contains intrinsic cues sufficient to direct the specific expression of dopaminergic traits in immature multipotential neural stem cells.

Melatonin rescues dopamine neurons from cell death in tissue culture models of oxidative stress

Dopamine (DA) neurons are uniquely vulnerable to damage and disease. Their loss in humans is associated with diseases of the aged, most notably, Parkinsons Disease (PD). There is now a great deal of evidence to suggest that the destruction of DA neurons in PD involves the accumulation of harmful oxygen free radicals. Since the antioxidant hormone, melatonin, is one of the most potent endogenous scavengers of these toxic radicals, we tested its ability to rescue DA neurons from damage/death in several laboratory models associated with oxidative stress. In the first model, cells were grown in low density on serum-free media. Under these conditions, nearly all cells died, presumably due to the lack of essential growth factors. Treatment with 250 microM melatonin rescued nearly all dying cells (100% tau+ neurons), including tyrosine hydroxylase immunopositive DA neurons, for at least 7 days following growth factor deprivation. This effect was dose and time dependent and was mimicked by other antioxidants such as 2-iodomelatonin and vitamin E. Similarly, in the second model of oxidative stress, 250 microM melatonn produced a near total recovery from the usual 50% loss of DA neurons caused by neurotoxic injury from 2.5 microM 1-methyl-4-phenylpyridine (MPP+). These results indicate that melatonin possesses the remarkable ability to rescue DA neurons from cell death in several experimental paradigms associated with oxidative stress.

Brain-derived neurotrophic factor works coordinately with partner molecules to initiate tyrosine hydroxylase expression in striatal neurons

Previous studies demonstrated that the cooperative interaction of acidic fibroblast growth factor (aFGF) and a partner molecule could induce the novel expression of the catecholamine (CA) biosynthetic enzyme, tyrosine hydroxylase (TH) in striatal neurons [Du and Iacovitti, J. Neurosci., in press; Du et al., J. Neurosci., 14 (1994) 7688-7694; Iacovitti et al., submitted]. The present study demonstrates that in addition to aFGF, brain-derived neurotrophic factor (BDNF) is also capable of moderate levels of TH induction (30% TH+ striatal neurons) when administered at high concentrations (100 ng/ml). As with aFGF, BDNFs activity depended on its coupling to an appropriate partner molecule; the most potent of which were 10 microM dopamine (DA) and 50 microM mazindol. BDNF + DA-induced TH expression was first evident after at 12 h; peaked by 18 h and declined by 4 days in culture. Cyclohexamide eliminated nearly all and alpha-amanitin reduced by half the TH induction elicited by DA and BDNF; indicating that both de novo transcription and translation were required for increased expression. In contrast with aFGF and BDNF, other putative dopamine differentiation factors, such as glial-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF), were able to elicit barely detectable (10%) levels of TH induction, regardless of the partner molecule used. These studies suggest that aFGF and/or BDNF may work coordinately with partner molecules to initiate TH expression; while a number of factors including, CNTF and GDNF, may be involved in its subsequent modulation.

Changes in host blood factors and brain glia accompanying the functional recovery after systemic administration of bone marrow stem cells in ischemic stroke rats.

In this study, we examined the effects of systemic administration of rat or human bone marrow stromal stem cells (MSC) at early and later times following middle cerebral artery occlusion (MCAO) on blood cytokines/growth factors, brain glia, and motor behavior in rats. Rats were tail vein injected with rat (r) and human (h) MSCs at 1 or 7 days post-MCAO. In some rats (N = 4) MSCs isolated from transgenic GFP rats were used to track the migration of cells peripherally and centrally at 2.5 and 28 days. Motor behavior was assessed using the modified Neurological Severity Score/climbing test at various time points before and after MCAO and transplantation. Prior to sacrifice at 1, 7, or 28 days post-MCAO, blood serum was collected for cytokine array analysis. Brains were analyzed for markers of activated microglia (CD11) and reactive astrocytes (GFAP). Administration of either allogeneic (rMSCs) or xenogeneic (hMSCs) stem cells produced a significant recovery of motor behavior after MCAO, with cells delivered at 1 day having greater effect than those at 7 days. Correlated with recovery was an amplification in activated microglia, reactive astrocytes, and new blood vessels in the infarct region, resulting in greater preservation in brain integrity. Concomitantly, expression of blood cytokines/chemokines (IL-13, MMP2, MIP) and growth factors/receptors (VEGF, neuropilin, EPOR, TROY, NGFR, RAGE) were modified following MSC administration. Because only rare GFP-labeled MSCs were observed in the brain, these effects did not depend on the central incorporation of stem cells. The early systemic administration of allogeneic or xenogeneic MSCs soon after experimental stroke produces a structural/functional recovery in the brain which is correlated with an increase in activated brain glia and changes in circulating cytokines and growth factors. Stem cells therefore induce an important neuroprotective and/or regenerative response in the host organism.

The Role of Lmx1a in the Differentiation of Human Embryonic Stem Cells into Midbrain Dopamine Neurons in Culture and After Transplantation into a Parkinson's Disease Model

Recent studies have provided important insight into the homeoprotein LIM homeobox transcription factor 1α (Lmx1a) and its role in the commitment of cells to a midbrain dopamine (mDA) fate in the developing mouse. We show here that Lmx1a also plays a pivotal role in the mDA differentiation of human embryonic stem (hES) cells. Thus, as indicated by small interfering RNA experiments, the transient early expression of Lmx1a is necessary for the coordinated expression of all other dopamine (DA)‐specific phenotypic traits as hES cells move from multipotent human neural progenitor cells (hNPs) to more restricted precursor cells in vitro. Moreover, only Lmx1a‐specified hNPs have the potential to differentiate into bona fide mDA neurons after transplantation into the 6‐hydroxydopamine‐treated rat striatum. In contrast, cortical human neuronal precursor cells (HNPCs) and mouse subventricular zone cells do not express Lmx1a or become mDA neurons even when placed in an environment that fosters their DA differentiation in vitro or in vivo. These findings suggest that Lmx1a may be critical to the development of mDA neurons from hES cells and that, along with other key early DA markers (i.e., Aldh1a1), may prove to be extremely useful for the selection of appropriately staged and suitably mDA‐specified hES cells for cell replacement in Parkinsons disease. STEM CELLS 2009;27:220–229

Cholinergic neurons of the chick ciliary ganglia express adrenergic traits in vivo and in vitro

In this study, we sought to determine whether neurons of the chick embryo ciliary ganglia (CG), a parasympathetic cholinergic ganglia, can express catecholaminergic (CA) traits. To accomplish this, we used immunocytochemical techniques to examine the presence of the CA enzymes tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) in CGs removed from chick embryo at day 8 of development (E8). Few neurons containing TH but not PNMT were found in the E8 CG. To examine whether CG neurons express CA enzymes in vitro, CGs removed from E8 chick embryo were dissociated and kept in culture for 3 to 12 days. In 50% of the culture dishes, some neurons contain TH or PNMT after 5 days in vitro. In an equal proportion of culture plates, CG neurons did not express the enzymes. To determine whether the proportion of CG neurons expressing TH or PNMT is increased by tissue influences, ganglion cells were co-cultured with notochord. In 90% of the co-culture experiments, most neurons present in the culture dishes stained with TH or PNMT after 5 days in vitro. To test for the presence of aromatic L-amino acid decarboxylase (AADC), another CA enzyme, cultures of CGs and CGs plus notochord were incubated with levodopa and processed for the detection of CA histofluorescence. Dopamine histofluorescence was present in all neurons after 3 days in vitro irrespective of the presence of notochord, suggesting that the expressions of TH and PNMT and that of AADC are differentially regulated. This study, therefore, demonstrates that cholinergic neurons of the CG contain CA enzymes in vivo and in vitro and that the proportion of neurons expressing CA traits during development in vitro can be increased by environmental cues such as those released by the notochord.

Expression of tyrosine hydroxylase in newly differentiated neurons from a human cell line (hNT).

PREVIOUS studies have demonstrated that the synergistic interaction of acidic fibroblast growth factor (aFGF) and a number of co-activator molecules (dopamine, TPA, IBMX/forskolin) can induce the novel expression of the catecholamine biosynthetic enzyme tyrosine hydroxylase (TH) in non-TH-expressing neurons. To date, TH gene induction has been achieved only in cultures of primary brain neurons. In the present study, we investigated whether TH expression could similarly be induced in a cell line derived from human teratocarcinoma cells. Treatment with aFGF and its co-activators resulted in the prolonged expression of TH in newly differentiating human neurons (hNT) but not in their undifferentiated precursors (NT2). These findings suggest that hNTs may serve as a continual source of TH-expressing neurons for cell transplantation and developmental studies.