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Tag: Epigenetic Alterations

The Link Between Cellular Senescence and Cellular Reprogramming – Article by Steve Hill

The Link Between Cellular Senescence and Cellular Reprogramming – Article by Steve Hill

Steve Hill


Editor’s Note: In this article, Steve Hill discusses the link between Cellular Senescence and Cellular Reprogramming.  This article was originally published by the Life Extension Advocacy Foundation (LEAF).

            ~ Kenneth Alum, Director of  Publication, U.S. Transhumanist Party, January 8, 2018

The reprogramming of cells is a well-established technique in medicine and has been for over a decade now. It allows the en masse creation of patient-matched cells and is the basis for multiple current therapies.

Cellular Senescence and Cellular Reprogramming share mechanisms

Induced pluripotent stem cells (also known as iPS cells or iPSCs) can be created directly from adult cells. The iPSC technology was pioneered by Shinya Yamanaka, who demonstrated in 2006 that the introduction of four specific genes encoding transcription factors could convert adult cells into pluripotent stem cells[1]. These factors are Oct4, Sox2, Klf4, and c-Myc (OSKM), or as many call them, the Yamanaka factors.

Today, we have a new paper that discusses how induced pluripotency and cellular senescence, two of several possible cellular states, share similarities[2]. It is likely no surprise that the two states are closely related and that some of the mechanisms for one process are shared by the other. It appears that certain key signaling molecules are important in determining both cell fate and senescence.

Controlling cell behavior in living animals

As our understanding of guiding cell fate grows rapidly by the passing year, it has huge implications for therapies that seek to control cellular activities and encourage certain types of cells to be created. Research is now starting to move beyond the petri dish and to where cells are being programmed in situ in living animals.

In 2013, the Hallmarks of Aging proposed that epigenetic changes are a primary reason we age, but, at the time, the evidence in living animals was lacking[3]. All this changed in late 2015 when researchers induced pluripotency in living animals using the OSKM reprogramming factors, in much the same way as iPSC technology creates on-demand cell types outside the body. In this case, they only very briefly induced OSKM so that the aging markers in cells were reset but not long enough to cause the cells to revert to a developmental state.

The results of this first attempt to reprogram cells in living animals resulted in the cells of the mice becoming functionally younger in many ways and increased their healthy lifespan[4]. These results lend yet more support for the hypothesis that epigenetic alterations are one of the reasons we age and that reversing those changes is a path to maintaining health and tissue function as we age. A number of research teams are now exploring cellular reprogramming in living animals with a view to translating this to humans. We discussed the findings of this paper during our monthly Journal Club here.

Conclusion

This paper may be of interest to those wishing to delve deeper into the world of cell fate and understand the connection between cellular senescence and induced pluripotency. This builds on the knowledge we already have, and it is not difficult to imagine a time in the near future when we will have a very high level of control over our cells via reprogramming techniques.

If the hypothesis of epigenetic alterations being one of the causes of aging turns out to be correct, then that would be a real game changer. We are likely not too far off from determining if this is the case or not, and we may have the answer in the next few years, given the current pace of progress.

Literature

[1] Takahashi, K., & Yamanaka, S. (2006). Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. cell, 126(4), 663-676.

[2] Mosteiro, L., Pantoja, C., Martino, A., & Serrano, M. (2017). Senescence promotes in vivo reprogramming through p16INK4a and IL‐6. Aging cell.

[3] López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G. (2013). The hallmarks of aging. Cell, 153(6), 1194-1217.

[4] Ocampo, A., Reddy, P., Martinez-Redondo, P., Platero-Luengo, A., Hatanaka, F., Hishida, T., … & Araoka, T. (2016). In vivo amelioration of age-associated hallmarks by partial reprogramming. Cell, 167(7), 1719-1733.

About Steve Hill

As a scientific writer and a devoted advocate of healthy longevity technologies, Steve has provided the community with multiple educational articles, interviews, and podcasts, helping the general public to better understand aging and the means to modify its dynamics. His materials can be found at H+ Magazine, Longevity Reporter, Psychology Today, and Singularity Weblog. He is a co-author of the book Aging Prevention for All – a guide for the general public exploring evidence-based means to extend healthy life (in press).

About LIFE EXTENSION ADVOCACY FOUNDATION (LEAF)

In 2014, the Life Extension Advocacy Foundation was established as a 501(c)(3) non-profit organization dedicated to promoting increased healthy human lifespan through fiscally sponsoring longevity research projects and raising awareness regarding the societal benefits of life extension. In 2015 they launched Lifespan.io, the first nonprofit crowdfunding platform focused on the biomedical research of aging.

They believe that this will enable the general public to influence the pace of research directly. To date they have successfully supported four research projects aimed at investigating different processes of aging and developing therapies to treat age-related diseases.

The LEAF team organizes educational events, takes part in different public and scientific conferences, and actively engages with the public on social media in order to help disseminate this crucial information. They initiate public dialogue aimed at regulatory improvement in the fields related to rejuvenation biotechnology.

Hallmarks of Aging: Epigenetic Alterations – Article by Steve Hill

Hallmarks of Aging: Epigenetic Alterations – Article by Steve Hill

Steve Hill


Editor’s Note: In this article, Mr. Steve Hill discusses one of the hallmarks of aging – in this case, Epigenetic Alterations. It is part of a paper published in 2013. It divides aging into a number of distinct categories (“hallmarks”) of damage to explain how the aging process works and how it causes age-related diseases [1]. This article was originally published by the Life Extension Advocacy Foundation (LEAF).

                        ~ Kenneth Alum, Director of Publication, U.S. Transhumanist Party, October 18, 2017

What are epigenetic alterations?

The DNA in every one of our cells is identical, with only small variations, so why do our various organs and tissues look so different, and how do cells know what to become?

DNA is modified by the addition of epigenetic information that changes the pattern of gene expression in a cell, suppressing or enhancing the expression of certain genes in a cell as the situation demands. This is how a cell in the liver knows that it needs to develop into a liver cell; the epigenetic instructions make sure that it is given the right orders to become the correct cell type.

At a basic level, these epigenetic instructions make sure that the genes needed to develop into a liver cell are turned on, while the instructions specific to other types of cells are turned off. Imagine if a heart cell was given the wrong instructions and became a bone cell!

How epigenetic alterations accumulate

The aging process can cause alterations to our epigenome, which can lead to alterations in gene expression that can potentially change and ultimately compromise cell function. As an example, epigenetic alterations of the immune system can harm activation and suppress immune cells, thus causing our immune system to fail and leaving us vulnerable to pathogens.

Inflammation is implicated in epigenetic alterations, and studies show that caloric restriction slows the rate of these epigenetic changes [2]. Metabolism and epigenetic alterations are closely linked with inflammation, facilitating a feedback loop leading to ever-worsening epigenetic alterations. Alterations to gene expression patterns are an important driver of the aging process. These alterations involve changes to DNA methylation patterns, histone modification, transcriptional alterations (variance in gene expression) and remodeling of chromatin (a DNA support structure that assists or impedes its transcription).

In the cell, gene expression is activated by hypomethylation (a loss of methylation) or silenced by hypermethylation (an increase of methylation) at a gene location. The aging process causes changes that reduce or increase methylation at different gene locations throughout the body. For example, some tumour suppressor genes become hypermethylated during aging, meaning that they cease functioning, which increases the risk of cancer [3]. Post-translational modifications of histones regulate gene expression by organizing the genome into active euchromatin regions, where DNA is accessible for transcription, or inactive heterochromatin regions, where DNA is compacted and less accessible for transcription. The aging process causes changes to these regions, which changes gene expression.

The aging process also causes an increase in transcriptional noise, which is the primary cause of variance in the gene expression happening between cells [4]. Researchers compared young and old tissues from several species and identified age-related transcriptional changes in the genes encoding key components of inflammatory, mitochondrial, and lysosomal degradation pathways [5].

 Finally, chromatin remodeling alters chromatin from a condensed state to a transcriptionally accessible state, allowing transcription factors and other DNA binding proteins to access DNA and control gene expression.

Conclusion

If we can find ways to reset age-related epigenetic alterations, we can potentially improve cell function, thus improving tissue and organ health.

One potential approach is the use of reprogramming factors, which reset cells to a developmental state, thus reverting epigenetic changes. We have been doing this for over a decade to create induced pluripotent stem cells, and recent work has seen a therapy based on that technique applied to living animals to reset their epigenetic alterations [6]. This reversed a number of age-related changes, and work is now proceeding with the goal of translating this to humans.

Epigenetic alterations might be considered like a program in a computer, but in this case, it is the cell, not a computer, being given instructions. Ultimately, damage causes changes that contribute to the cell moving from an efficient “program” of youth to a dysfunctional one of old age. If we can reset that program, we can potentially address this hallmark of aging, and a number of researchers are working on that right now.

 

Literature

[1] López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G. (2013). The hallmarks of aging. Cell, 153(6), 1194-1217.

[2] Maegawa, S., Lu, Y., Tahara, T., Lee, J. T., Madzo, J., Liang, S., … & Issa, J. P. J. (2017). Caloric restriction delays age-related methylation drift. Nature Communications, 8.
[3] Maegawa, S., Hinkal, G., Kim, H. S., Shen, L., Zhang, L., Zhang, J., … & Issa, J. P. J. (2010). Widespread and tissue specific age-related DNA methylation changes in mice. Genome research, 20(3), 332-340.

[4] Bahar, R., Hartmann, C. H., Rodriguez, K. A., Denny, A. D., Busuttil, R. A., Dollé, M. E., … & Vijg, J. (2006). Increased cell-to-cell variation in gene expression in ageing mouse heart. Nature, 441(7096), 1011-1014.

[5] De Magalhães, J. P., Curado, J., & Church, G. M. (2009). Meta-analysis of age-related gene expression profiles identifies common signatures of aging. Bioinformatics, 25(7), 875-881.

[6] Ocampo, A., Reddy, P., Martinez-Redondo, P., Platero-Luengo, A., Hatanaka, F., Hishida, T., … & Araoka, T. (2016). In Vivo Amelioration of Age-Associated Hallmarks by Partial Reprogramming. Cell, 167(7), 1719-1733.

 

About Steve Hill

As a scientific writer and a devoted advocate of healthy longevity technologies, Steve has provided the community with multiple educational articles, interviews, and podcasts, helping the general public to better understand aging and the means to modify its dynamics. His materials can be found at H+ Magazine, Longevity Reporter, Psychology Today, and Singularity Weblog. He is a co-author of the book Aging Prevention for All – a guide for the general public exploring evidence-based means to extend healthy life (in press).

About LIFE EXTENSION ADVOCACY FOUNDATION (LEAF)

In 2014, the Life Extension Advocacy Foundation was established as a 501(c)(3) non-profit organization dedicated to promoting increased healthy human lifespan through fiscally sponsoring longevity research projects and raising awareness regarding the societal benefits of life extension. In 2015 they launched Lifespan.io, the first nonprofit crowdfunding platform focused on the biomedical research of aging.

They believe that this will enable the general public to influence the pace of research directly. To date they have successfully supported four research projects aimed at investigating different processes of aging and developing therapies to treat age-related diseases.

The LEAF team organizes educational events, takes part in different public and scientific conferences, and actively engages with the public on social media in order to help disseminate this crucial information. They initiate public dialogue aimed at regulatory improvement in the fields related to rejuvenation biotechnology.