Deconstructing age reprogramming

A new and simple procedure was applied to detect bisphenol A (BPA) based on a BPA aptamer and its complementarystrand (Comp. Str.). An electrode was modified with a mixture of carboxylated multiwalled carbon nanotubes and chitosan.The Comp. Str. was immobilized on a modified-glassy carbon electrode (GCE) surface via covalent binding. After theincubation of the aptamer with the electrode surface, it could interact with the Comp. Str. In the presence of BPA, itsaptamer will interact with the analyte, resulting in some changes in the configuration and leading to separation from theelectrode surface. Due to the attached ferrocene (Fc) group on the 50 head of the aptamer, the redox current of Fc hasreduced. This aptasensor can sense the level of BPA in the linear range of 0.2–2 nM, with a limit of detection of 0.38 nMand a sensitivity of 24.51 lA/nM. The proposed aptasensor showed great reliability and selectivity. The acceptable selectivity is due to the specificity of BPA binding to its aptamer. The serum sample was used as a real sample; the aptasensorwas able to effectively recover the spiked BPA amounts. It can on-site monitor the BPA in serum samples withacceptable recoveries.

Induced Pluripotent Stem (iPS) Cells in Dentistry: A Review

iPS cells are derived from somatic cells via transduction and expression of selective transcription factors. Both viral-integrating (like retroviral) and non-integrating (like, mRNA or protein-based) techniques are available for the production of iPS cells. In the field of dentistry, iPS cells have been derived from stem cells of apical papilla, dental pulp stem cells, and stem cells from exfoliated deciduous teeth, gingival and periodontal ligament fibroblasts, and buccal mucosa fibroblasts. iPS cells have the potential to differentiate into all derivatives of the 3 primary germ layers i.e. ectoderm, endoderm, and mesoderm. They are autogeneically accessible, and can produce patient-specific or disease-specific cell lines without the issue of ethical controversy. They have been successfully tested to produce mesenchymal stem cells-like cells, neural crest-like cells, ameloblasts-like cells, odontoblasts-like cells, and osteoprogenitor cells. These cells can aid in regeneration of periodontal ligament, alveolar bone, cementum, dentin-pulp complex, as well as possible Biotooth formation. However certain key issues like, epigenetic memory of iPS cells, viral-transduction, tumorgenesis and teratoma formation need to be overcome, before they can be successfully used in clinical practice. The article discusses the sources, pros and cons, and current applications of iPS cells in dentistry with an emphasis on encountered challenges and their solutions.

Increases in iPS Transcription Factor (Oct4, Sox2, c-Myc, and Klf4) Gene Expression after Modified Electroconvulsive Therapy

OBJECTIVE: Electroconvulsive therapy (ECT) is a reasonable option for intractable depression or schizophrenia, but a mechanism of action has not been established. One credible hypothesis is related to neural plasticity. Three genes (Oct4, Sox2, c-Myc) involved in the induction of induced pluripotent stem (iPS) cells are Wnt-target genes, which constitute a key gene group involved in neural plasticity through the TCF family. Klf4 is the other gene among Yamanaka's four transcription factors, and increases in its expression are induced by stimulation of the canonical Wnt pathway. METHODS: We compared the peripheral blood gene expression of the four iPS genes (Oct4, Sox2, c-Myc, and Klf4) before and after modified ECT (specifically ECT with general anesthesia) of patients with intractable depression (n=6) or schizophrenia (n=6). Using Thymatron ten times the total bilateral electrical stimulation was evoked. RESULTS: Both assessments of the symptoms demonstrated significant improvement after mECT stimulation. Expression of all four genes was confirmed to increase after initial stimulation. The gene expression levels after treatment were significantly different from the initial gene expression in all twelve cases at the following treatment stages: at the 3rd mECT for Oct4; at the 6th and 10th mECT for Sox2; and at the 3rd, 6th and 10th mECT for c-Myc. CONCLUSION: These significant differences were not present after correction for multiple testing; however, our data have the potential to explain the molecular mechanisms of mECT from a unique perspective. Further studie should be conducted to clarify the pathophysiological involvement of iPS-inducing genes in ECT.

Stem Cells Cloning and Therapeutic Potential.

Stem cells have huge potential to transform current manner in which medicine is practiced. Rather than treating diseased cells with medicines and antibiotics, stem cells can just replace the diseased cells with healthy cells. But it will take time before this research gets translated to the clinic. At present, various types of stem cells like human embryonic stem (hES) cells, induced pluripotent stem (iPS) cells, fetal stem cells, adult tissue-specific stem cells (HSCs, MSCs, etc.), very small embryonic-like stem cells (VSELs) and related technologies like therapeutic cloning are subject to extensive research. Clinicians appear to be in a hurry to apply the stem cells to their patients and there is a huge industry banking stem cells for future autologus use. However, the scientifc community is still not sure which is the best stem cell candidate for regenerative medicine. The chapter provides an update on various fronts and also discusses whether there exists a need to bank stem cells for future use. The author is puzzled by realizing as to what needs to be repaired/ regenerated-the stem cells or their microenvironment ‘niche’!

Nuclear reprogramming and epigenetic rejuvenation.

William Harvey’s motto Ex ovo omnia (‘All from the egg’) on the frontispiece of his treatise On the generation of living creatures (1651) was well chosen and extraordinarily prescient. Centuries later, the egg was shown to have a striking capacity for bringing forth life – life produced by experimental manipulation, ‘animal cloning’, outside the normal physiology of fertilization (Gurdon and Byrne 2005). Cloning through somatic cell nuclear transfer (SCNT) showed that the restriction of developmental potential during cellular differentiation is the result of epigenetic changes in gene expression rather than through loss of DNA – although certain lineages, such as B- and T-cells, are known to undergo programmed DNA rearrangements (Hochedlinger and Jaenisch 2002). It is the reversal of these epigenetic changes during ‘reprogramming’ of the specialized adult nucleus within the reconstructed embryo that results in its re-acquisition of developmental potential and the consequent recapitulation of development, ultimately giving rise to a cloned newborn. A commonly held defi nition is that nuclear reprogramming by SCNT is the process by which a specialized nucleus reacquires developmental potential (Singh 1999). However, nuclear reprogramming is much more than this. It is a manylayered process. Intimately associated with developmental reprogramming of the specialized adult nucleus to an earlier, embryonic, totipotent state is age reprogramming; the ageing ‘clock’ of the transferred nucleus is reset back to zero; an old cell can give rise to newborn clone (Wilmut et al. 1997). This begs the question of whether age reprogramming can be separated from developmental reprogramming. Being able to reprogramme the ageing clock in isolation, while maintaining the differentiated state of a cell, would essentially mean that the cell is made young again: rejuvenated. Clearly, should this be achieved, the consequences would be profound (fi gure 1). Nuclear reprogramming observed in ‘classical’ animal cloning (where adult cells are reprogrammed to an embryonic state after SCNT) has recently been recapitulated in vitro by the generation of embryonic-like induced pluripotent stem cells (iPS cells; Takashi and Yamanaka 2006). Induction of iPS cells allows the process of epigenetic rejuvenation of adult cells to embryonic cells, as seen after SCNT, to be studied in a well-defi ned system (Surani and McClaren 2006). However, certain features of the rejuvenation seen in classical cloning are likely to differ from that seen in iPS cell generation. For one, telomeres, whose shortening is seen as a key characteristic of ageing cells, are ‘rejuvenated’ by telomerase during iPS cell induction from old somatic cells (Marion et al. 2009). This mechanism is unlikely to be the major mechanism for ‘rejuvenating’ telomeres in eggs after SCNT. During the early cleavage divisions, telomeres are lengthened by a telomere sister-chromatid exchange recombination mechanism that is peculiar to this stage of development and is under the sole control of the maternal cytoplasm, as it is unaffected by the absence of a paternal chromosomal complement (Liu et al. 2009). Thus, the mechanism(s) and pathway(s) of rejuvenation that result from SCNT, which have yet to be uncovered, are likely to be different from those operating during the generation of iPS cells. Notwithstanding these differences, SCNT or introduction of ‘reprogramming factors’ into somatic cells both appear to direct developmental reprogramming and age reprogramming seamlessly: age reprogramming does not take place without de-differentiation into embryonic cells (developmental reprogramming). But can these intimately associated aspects of nuclear reprogramming be disentangled? While it seems hardly possible, recent work indicates that age reprogramming might indeed be separable from developmental reprogramming. Differentiation of myelomonocytic progenitors into macrophages involves an exit from the cell cycle.