[blog]

[September 7, 2009]
The Placebo Effect: A very basic neurological process
S. Andrei Anghel

The placebo effect – the curious phenomenon in which a patient feels better and even gets better when he thinks he is receiving treatment but in fact is not – has received great attention by the scientific and medical communities and by the general public in the recent decades. After its discovery, experimental medical trials had to be redesigned to account for it, and a race began among scientists to elucidate how this extraordinary “treatment” works. Many of the following studies have focused on the placebo effect of relieving pain (1) and considerable data now indicates that this occurs through the endogenous opioid system (the same neurological circuit activated by painkillers such as morphine) (2,3).

In this month’s edition of Neuron, Eippert et al. (4) produce solid data supporting a role of the opioid system in the placebo effect. They do this through an elegant study in which patients were given an inert treatment for a mild burn, and half of them were further administered naloxone, a drug that blocks the opioid circuits in the brain. The authors then employed a combination of two state-of-the-art medical imaging techniques – functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) – to visualize which areas of the brain “light up” in the presence and absence of the naloxone.

Their results are groundbreaking: not only do they show a clear correlation between administration of naloxone and the decrease in placebo pain relief, but they identify some very “primitive” brain components – the amygdala, the hypothalamus and part of the brainstem – as part in the placebo effect circuitry. This comes as a great surprise: because the phenomenon is the result of voluntary expectation (the patient thinks he is receiving treatment) it would be more intuitive that it mainly involved the more “evolved” and human-specific parts of the cortex.

Given these new data, one cannot help wondering: if the placebo effect is so deeply rooted in one’s brain, does that mean it is somehow connected to more crucial brain functions? And when and more importantly why, did the placebo effect evolve? Like is often the case with science, this groundbreaking discovery seems to generate more questions than it answers.

1. V. De Pascalis, C. Chiaradia, E. Carotenuto, Pain 96, 393 (Apr, 2002).
2. P. Grevert, L. H. Albert, A. Goldstein, Pain 16, 129 (Jun, 1983).
3. J. D. Levine, N. C. Gordon, H. L. Fields, Lancet 2, 654 (Sep 23, 1978).
4. F. Eippert et al., Neuron 63, 533 (Aug 27, 2009).

[September 3, 2009]
Single Factor Reprogramming of Human Fetal Neural Stem Cells with Oct4: A Step Towards Translating iPSC Research to the Bedside
Katie Ransohoff

The ethically fraught field of embryonic stem cell research received much attention in late 2007 when induced plurpotent cells stem cells (iPSCs) were derived from somatic cells manipulated with the Yamanaka factors-- Oct3/4, Sox2, Klf4, c-Myc. These genes, which are highly expressed in embryonic stem cells, induce pluripotency and “embryonic stem cell-like” characteristics in human and mouse cells when overexpressed. Such cells hold promise for the field of regenerative medicine, and they dodge the controversy surrounding embryonic stem cells, since iPSCs can be derived from somatic cells, not embryos.  Furthermore, they have demonstrated therapeutic benefit similar to that of embryonic stem cells. However, iPSCs are not free from drawbacks, and use could be limited in humans if viral transgenes are used in the induction process. This is especially true for oncogenes c-Myc and KLF4; reactivation of these in the host genome can lead to tumor formation. This has led researchers to examine the precise mechanisms of the Yamanaka factors and seek out combinations of 1-2 factors that are equally efficacious but pose less risk of tumorigenicity. Kim et al. (1) demonstrated in Feburary of this year that exogenous Oct4 expression was sufficient to reprogram adult mouse neural stem cells into iPSCs with capacity to differentiate into cells of endodermal, ectodermal, and mesodermal lineage. In a Nature Letter, Kim et al. showed that ectopic expression of Oct4 is sufficient to induce pluripotency in human fetal neural stem cells. In vitro, neural stem cells were retrovirally infected with human Oct4 and KLF (two factor) or Oct4 alone (one factor). Eight days after infection, cells were replated on feeder layers, and 10 weeks later, colonies with neural rosettes were observed. Within 5-6 days, the rosette could be removed from the colony, and the rest of the human ES-cell-like colony could be replated and cultured, with an overall reprogramming efficiency of 0.004% in the single factor colony. To confirm that the Oct4 reprogramming was sufficient, epigenetic analysis showed that the levels of methylation of the Oct4 promoter in the reprogrammed cells and embryonic stem cells were similar. The reprogrammed cells retained normal karyotypes, suggesting that single-factor reprogramming is not only feasible, but also not harmful to cell differentiation capacity and phenotype. It is possible that reprogramming of these neural stem cells is possible with only a single factor because their genetic and epigenetic profile is similar to that of embryonic stem cells. Future work is necessary to examine whether non-viral manipulation of cells can induce pluripotency with enough efficiency to create therapeutic cell lines, and which cell sources are ideal reprogramming candidates.

1. J.B. Kim et al., Nature (Aug 28, 2009)

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