Yang-Ki Minn

In vitro and in vivo analyses of human embryonic stem cell‐derived dopamine neurons

Human embryonic stem (hES) cells, due to their capacity of multipotency and self‐renewal, may serve as a valuable experimental tool for human developmental biology and may provide an unlimited cell source for cell replacement therapy. The purpose of this study was to assess the developmental potential of hES cells to replace the selectively lost midbrain dopamine (DA) neurons in Parkinsons disease. Here, we report the development of an in vitro differentiation protocol to derive an enriched population of midbrain DA neurons from hES cells. Neural induction of hES cells co‐cultured with stromal cells, followed by expansion of the resulting neural precursor cells, efficiently generated DA neurons with concomitant expression of transcriptional factors related to midbrain DA development, such as Pax2, En1 (Engrailed‐1), Nurr1, and Lmx1b. Using our procedure, the majority of differentiated hES cells (> 95%) contained neuronal or neural precursor markers and a high percentage (> 40%) of TuJ1+ neurons was tyrosine hydroxylase (TH)+, while none of them expressed the undifferentiated ES cell marker, Oct 3/4. Furthermore, hES cell‐derived DA neurons demonstrated functionality in vitro, releasing DA in response to KCl‐induced depolarization and reuptake of DA. Finally, transplantation of hES‐derived DA neurons into the striatum of hemi‐parkinsonian rats failed to result in improvement of their behavioral deficits as determined by amphetamine‐induced rotation and step‐adjustment. Immunohistochemical analyses of grafted brains revealed that abundant hES‐derived cells (human nuclei+ cells) survived in the grafts, but none of them were TH+. Therefore, unlike those from mouse ES cells, hES cell‐derived DA neurons either do not survive or their DA phenotype is unstable when grafted into rodent brains.

Stroke after Burn

Background: Stroke is regarded as a possible complication of burn. Some author reported that stroke developed in 22% of burned patients. However, the true incidence and the clinical characteristics of stroke occurring after burn injury are unknown. Methods: We reviewed the medical records of patients who had been admitted to the Burn Center at the Hangang Sacred Heart Hospital between January 1997 and May 2005. Patients with mild burns who did not require admission to the hospital were excluded from the study. Stroke patients were selected. Results: A total of 13,468 patients were admitted due to burn injury during the above-mentioned period. Nine (0.07%) patients (5 men, 4 women; mean age, 55 years) developed stroke while being under treatment for their burn injuries. The median duration between the burn injury and stroke onset was 33 days (range, 2–307). The mean surface area of the burn wound was 21% (range, 3–50). Ischemic infarction was observed in 4 patients, intracerebral hemorrhage in 3 others, and multiple hemorrhagic infarction and subdural hematoma in 1 patient each. Seven out of the 9 patients revealed the presence of septic conditions that occurred subsequent to the burn. Conclusion: Stroke is a rare complication of a burn injury in the clinical setting. It develops in moderate burns (10–50% of the total body surface area) after some time. Prevention of infection/sepsis is important to alleviate the occurrence of a stroke in these patients.

Induction of apoptosis signal-regulating kinase 1 and oxidative stress mediate age-dependent vulnerability to 3-nitropropionic acid in the mouse striatum

The mitochondrial toxin, 3-nitropropionic acid (3-NP), produces age-dependent oxidative stress and selective striatal damage, which may simulate Huntingtons disease starting in middle age. Recent reports showed that apoptosis signal-regulating kinase 1 (Ask1) activated by oxidative stress triggers a cell death signaling pathway. 3-NP was injected to the striatum in C57BL/6J mice. We have confirmed that striatal lesion volume and DNA fragmentation were age-dependent after 3-NP treatment. In the non-injured striatum of the middle-aged group, the protein levels of Ask1 and its active form, phosphorylated Ask1 (pAsk1), were significantly higher than in the young group. Ask1 increased more in the 3-NP injured striatum of the middle-aged group than in the non-injured striatum, and subsequently the activity of pAsk1 was significantly higher than in the young group. However, middle-aged SOD1Tg mice showed significant reductions of Ask1 and pAsk1 in the injured and the non-injured striatum compared to the middle-aged group. In particular, apoptosis signal transduction and cell death were significantly inhibited by the reduction of Ask1 expression using siRNA. Present results suggest that age-related upregulation of Ask1 and oxidative stress may mediate age-dependent striatal vulnerability to 3-NP.

Significance of Silent Infarcts in Acute Ischemic Stroke Patients Aged 80 Years and Older

Background: The significance of silent infarcts (SIs) is unknown in very elderly patients with first-ever acute ischemic stroke. Methods: Fifty patients aged 80 years and older with first-ever acute ischemic stroke were studied. The conventional risk factors for stroke, the scores of age-related white matter changes, and the findings on echocardiography were compared between patients with and without SIs. Results: Thirty-eight patients (76%) had one or more SIs. The patients without SIs frequently had atrial fibrillation (50% vs. 13.2%, p = 0.014) or spontaneous echo contrast or thrombi on echocardiography (57.1% vs. 0%, p = 0.026) and showed lower scores on age-related white matter changes (0.5 ± 0.67 vs. 1.13 ± 0.58, p = 0.002) than did patients with SIs. There were no differences in other risk factors for stroke between the two groups. Conclusion: In patients aged 80 years and older, the absence of SIs with a first-ever acute ischemic stroke may suggest the presence of cardiac embolic sources or atrial fibrillation.

Noggin Over-Expressing Mouse Embryonic Fibroblasts and MS5 Stromal Cells Enhance Directed Differentiation of Dopaminergic Neurons from Human Embryonic Stem Cells

Directed methods for differentiating human embryonic stem cells (hESCs) into dopaminergic (DA) precursor cells using stromal cells co-culture systems are already well established. However, not all of the hESCs differentiate into DA precursors using these methods. HSF6, H1, H7, and H9 cells differentiate well into DA precursors, but CHA13 and CHA15 cells hardly differentiate. To overcome this problem, we modified the differentiation system to include a co-culturing step that exposes the cells to noggin early in the differentiation process. This was done using γ-irradiated noggin-overexpressing CF1-mouse embryonic fibroblasts (MEF-noggin) and MS5 stromal cells (MS5-noggin and MS5-sonic hedgehog). After directed differentiation, RT-PCR analyses revealed that engrailed-1 (En-1), Lmx1b, and Nurr1, which are midbrain DA markers, were expressed regardless of differentiation stage. Moreover, tyrosine hydroxylase (Th) and an A9 midbrain-specific DA marker (Girk2) were expressed during differentiation, whereas levels of Oct3/4, an undifferentiated marker, decreased. Immunocytochemical analyses revealed that protein levels of the neuronal markers TH and TuJ1 increased during the final differentiation stage. These results demonstrate that early noggin exposure may play a specific role in the directed differentiation of DA cells from human embryonic stem cells.

Lateral temporal atrophy in mild cognitive impairment

decline is a hallmark of Alzheimer’s disease (AD), describing both risks and benefits in terms of changes in function is a logical choice for such an exercise and requires understanding the temporal relationship of changes in cognition and function. The objective of this study was to co-vary the individual items with Disability Assessment in Dementia (DAD) with measures of cognition and time to identify the temporal order associated with disease progression. Methods: 337 subjects (196 AD, 70 mild cognitive impairment, 71 cognitively healthy volunteers) were enrolled at 40 study sites across the US and Europe during 2006 and 2007 for an 18-month non-interventional study (ELN-AIP-901), sponsored by Elan Pharmaceuticals and Wyeth Research. Recruitment criteria were similar to those used in the ADNI study. DAD was performed at baseline and at 6-months intervals. DAD item scale scores were co-varied with Mini-Mental State Examination (MMSE) score using survival analysis. Results: Using median MMSE survival, patients were unable to perform activities for all items of the sub-domains for finance, medication, and outings at higher scores than for items in other sub-domains. The specific activities ‘‘organize finance’’ and ‘‘adequately organize correspondence’’ exhibited the shortest MMSE survival, ie, ‘‘lost’’ earlier in the course of the disease. The inability to perform items in the sub-domains of personal hygiene, dressing, eating, and continence occurred at lowest MMSE survivals, ie, ‘‘lost’’ at the later stages of AD progression. Seven items ‘‘lost’’ late in the course of the disease, lowest median MMSE survival, were from 3 of the 10 sub-domains, specifically dressing (4 items), eating (2 items), and continence (1 item). Conclusions: Inability to perform instrumental functional activities occurred earlier in the course of the disease, as measured by MMSE score, than basic functional activities. DAD items exhibit a hierarchical loss progression associated with cognitive decline, by MMSE. These findings support the use of DAD items that correlate with AD progression as a method for characterizing benefit and risk.