Stem cells are our very own foundation. They’re the origins of every cell type in our bodies. We need stem cells to rejuvenate, but as we age and decline, so too does our stem cells.
Our bodies contain numerous different cell types. In the location of each of those types are stem cell niches – pools of stem cells ready to work when they’re needed.
Stem cells are our foundation. They’re the origins of our bones and our muscles, our eyes and our ears, our brains and our hearts, and much, much more. Stem cell niches are populations of stem cells in specific locations, throughout the body. Within these stem cells niches are micro-environments that regulates their differentiated progenies — how they participate in tissue generation, maintenance and repair.
There are many different types of stem cells coming from all the various parts of our bodies, and they’re formed at different stages in our lives. From our humble beginnings as a totipotent zygote, we develop into a blastocycst and start producing embryonic stem cells for our fetal development. During this time, we begin to produce a myriad of tissue-specific stem cells or ‘adult stem cells‘, and these remain in our bodies throughout our lives. Over the course of our lifetime, stem cells remain in a non-specific state until they’re needed. They have a remarkable ability for self-renewal after they’re used by the body, and as a result they don’t get depleted. Below is an illustration of this and how they specialize into specific cells when needed, with respect to their niche.
However, as is the recurring theme in this blog, our bodies decline as we age; and so too does our stem cells. Preserving our stem cell populations is vital for maintaining tissue homeostasis as we become older. Aging causes several different detrimental dysfunctions which increasingly deteriorates our health. As we age, stem cells loose their proper functionality, ultimately leading to senescence, loss of regenerative capacity or cell death. One of the more famous examples of this is the phenotypic change in our hair follicles; grey hair. The population of melanocyte stem cells in our hair follicles gets depleted as we age, thus our bodies are unable to replenish our pigment cells responsible for giving our hair its colour.
So what can we do to maintain our stem cell populations and their functionality?
A concept that has shown promise during the last decade is something called ‘Parabiosis’. This procedure consists of joining two organisms together by sharing each others blood circulation. The key player in parabiosis is a protein called GDF11, which declines as we age. The exact relationship between GDF11 and aging is unclear. Despite promising results shown in animal models, parabiosis remains a controversial issue, as it’s been demonstrated to cause both positive and negative effects on stem cell aging.
A more interesting cell-based therapeutic approach is induced pluripotent stem cells (iPSCs) that can be derived from your own somatic cells. By reprogramming your somatic cells into iPSCs, they can be used for regenerative medicine in a variety of ways (e.g. autologous therapies). This approach completely circumvents the controversy surrounding the use of embryonic stem cells. Additionally, as this approach is patient-specific, the chances of immune rejection are almost completely eliminated. The only drawback of this method, with regards to modelling aging, is that these reprogrammed cells no longer exhibit age-associated features (e.g. cellular senescence, telomere shortening).
So far I’ve covered many of the amazing advances in our understanding of aging and its related diseases. There is the potential of including a simple supplementation (NAD+) to your daily routine. There are promising prospects of using simple compounds to remove the build-up of senescent cells in our bodies, and lastly, there are many promising stem cell therapies. All with incredible potential to markedly improve our health and increase our lifespan. As such, there’s an ever increasing likelihood of you and I living longer and in better health than our predecessors.
Imagine what the future holds.
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