The SENS Research Foundation has divided aging damage into seven categories each with a solution in order to treat or prevent age-related diseases. We have summarized all of these aging damages below as well as the current state of progress for each. It is important to note that SENS is slightly different in layout to the hallmarks of aging which we normally talk about at LEAF.
Indeed we consider these approaches to be compatible in their aims and thus we support them both.
RepleniSENS: Cell loss and tissue atrophy
Over time our cells are damaged from various sources including trauma, environmental exposure to toxins, oxidative stress and other stressors. Sometimes the damaged cells are repaired, but sometimes they are destroyed, become dysfunctional and cease dividing (senescent) or are so damaged they destroy themselves (apoptosis) to protect the body. Some of these lost cells have to be replaced by pools of tissue-specific specialized stem cells but over time these reserves run low leading to increasingly less effective repair over time.
Over the course of decades, long lived tissues like brain, heart and skeletal muscles gradually lose cells and as replacement dwindles their function becomes compromised. This leads to loss of muscle strength, poor injury recovery known and muscle wastage known as Sarcopenia and is one reason why older people are frail. The brain also loses neurons which leads to cognitive decline and dementia as well as the loss of fine muscle movements and ultimately Parkinson’s disease. The immune system also suffers, with the thymus gradually shrinking and losing the ability to produce immune cells, leaving you vulnerable to diseases.
Where are we now?
Thankfully this is already a well advanced field. SENS has not needed to get involved in this area as it is well funded and moving along very rapidly. Only this month we have seen Hematopoietic stem cells produced for the first time and research in this field is moving forward at a furious rate. It will be plausible in the near future that we will be able to produce every cell type within the body to replace age related losses. This will allow us to replenish the immune system, repair the damage caused by neurodegenerative diseases such as Alzheimer’s and Parkinson’s, and repair organs in the not too distant future.
OncoSENS: Cancerous cells
Two types of damage accumulate in our genes as we age: mutations and epimutations. Mutations are the result of direct damage to the DNA itself and epimutations is damage to the scaffolding of DNA that controls gene expression, somewhat like a lens. Both forms of damage lead to abnormal gene expression which causes the cell to malfunction. The most common form of cell malfunction is uncontrolled growth better known as cancer.
Cancer uses two pathways to uncontrolled growth: hijacking telomerase and using the Alternative Lengthening of Telomeres (ALT) mechanism. Both allow cancer to maintain its telomeres and thus remain immortal, and growing out of control. Therapies that can inhibit these pathways could be combined and are therefore a potential way for us to defeat all cancers.
Where are we now?
ALT therapies are progressing following a successful fundraiser on Lifespan.io last year raising an amazing 72k. SENS has been developing a high throughput assay for ALT allowing cost effective candidate evaluation for drugs that can inhibit or destroy cancer cells using ALT. Within the next year a company based on ALT should be possible.
Telomerase inhibiting therapies are being developed by a number organizations and companies so the SENS Research Foundation does not need to get involved with this. Therapies that inhibit telomerase in cancer cells are already in clinical trials and are well funded.
MitoSENS: Mitochondrial mutations
The mitochondria are the power plants of the cell, converting nutrients from food into energy known as ATP, a form of energy that powers cellular function. Unlike the rest of the cell, mitochondria have their own DNA known as mtDNA which is outside of the cell nucleus where the rest of our genes are kept. The problem is, as mitochondria produce ATP they also generate waste products as a byproduct, in this case highly reactive molecules called free radicals. Free radicals can strike and damage parts of the cell including the mtDNA due to their close proximity to the source of free radicals are very vulnerable to these damaging strikes. A strike can delete sections of mtDNA leaving the mitochondria unable to produce ATP. Even worse, these damaged mutant mitochondria enter an abnormal metabolic state to remain alive, this state produces little energy and generates large amounts of waste that the cell cannot dispose off. Ironically the cell even preserves these damaged mitochondria instead of disposing of them and sends healthy ones to be recycled instead, this means that mutant mitochondria and their progeny can rapidly take over an entire cell. This leads to cells with damaged mitochondria that dump waste into the circulation causing system wide levels of oxidative stress to rise and driving the aging process.
The solution to this problem is to move the mtDNA to the cell nucleus where it will have a far greater level of protection from free radical strikes. Indeed evolution has already started doing this in our cells and has already moved around 1000 mitochondrial genes to the nucleus. SENS Research Foundation is proposing to accelerate the process nature has started.
Where are we now?
The SENS Research Foundation successfully fundraised for the MitoSENS project on Lifespan.io back in 2015. They then followed up with a publication in the prestigious Nucleic Acids Research journal showing their results in September 2016. Thanks to the support of the community the MitoSENS project succeeded in migrating not one but two mitochondrial genes to the cell nucleus, a world first. Since then progress has been rapid and they have now almost migrated 4 of the 13 mitochondrial genes. They are currently refining the process into a standardized therapy.
ApoptoSENS: Death-resistant cells
Our cells have a built-in safety device that causes cells that are dysfunctional and damaged to destroy themselves in a process known as apoptosis and are disposed of by the immune system. However as we age cells increasingly fail to dispose of themselves in this manner and they enter a state known as senescence. Senescent cells do not replicate or support the tissue they are a part of, instead they send out pro-inflammatory signals that poison their healthy neighbors causing them to also become senescent. The same pro-inflammatory signals block stem cell activity and prevent them from repairing tissue. As we age more of these cells build up leading to increasingly poor tissue repair and regeneration.
The solution to this problem is to remove senescent cells periodically in order to help maintain tissue repair and maintenance. Therapies that remove senescent cells are known as senolytics and have been big news for the last year or so.
Where are we now?
There has been a huge level of interest in senescent cell removal therapies in the last year or two and a number of companies are currently developing senolytics. Unity Biotechnology is taking the first generation of senolytics into human clinical trials this year after being successfully funded by Amazon’s Jeff Bezos and a number of other big investors. However the heat is on as other companies are following up close behind with potentially more sophisticated approaches for removing senescent cells such as plasmid based solutions from Oisin Biotechnologies and a synthetic biology approach from CellAge who successfully fundraised on Lifespan.io last year.
The SENS Research Foundation is also working on a joint project with the Buck Institute for Research on Aging on senescent cells this year with particular focus on senescent cells in the immune system.
GlycoSENS: Extracellular matrix stiffening
Much of the structural features of the body are made of proteins that are created early in life, these structures are either not replaced or recycled, or if they are they are at a very slow rate over decades. The health of these structural components relies on the proteins making them up retaining their proper structure. These proteins are responsible for the elasticity of tissue such as in the skin and blood vessel walls as well as the transparency of the lens of the eye. Unfortunately, blood sugar and other molecules react with these structural proteins and bond with them creating fused crosslinks. Crosslinks bind neighboring proteins together impairing their movement and function. In the case of the artery wall crosslinked collagen prevents the artery from flexing in time with the pulse leading to hypertension and a rise of blood pressure. This loss of flexibility increases over time meaning the full force of blood being pumped around the body goes directly into the organs damaging them instead of being absorbed by the blood vessel walls. In time this leads to organ damage and an increase in the risk of stroke.
The SENS Research Foundation proposes to find ways to break down these crosslinks to restore movement to the structural proteins and thus reversing the consequences of their formation. There are a number of types of crosslinks that accumulate in the body but the focus is on glucosepane which is a very long lasting crosslink that the body can only break down very slowly if at all.
Where are we now?
The problem for many years was obtaining enough glucosepane to be able to test therapies on. Thanks to the funding by the SENS Research Foundation progress at Yale University now allows the cheap production of glucosepane on demand, this means that researchers can now test directly on it and find antibodies and enzymes to dissolve the accumulated crosslinks. Yale already has some antibodies against glucosepane, it is anticipated that by the end of the year monoclonal antibodies will be available and there is strong evidence for bacteria with enzymes that can break it glucosepane.
AmyloSENS: Extracellular aggregates
Misfolded proteins produced in the cell are normally broken down and recycled within the cell, however as we age more and more misfolded proteins accumulate forming sticky aggregates. These misshapen proteins are not fit for purpose and they impair cell or tissue function with their presence. This extracellular junk is known as amyloid and comes in a number of types. Amyloids contribute to Alzheimer’s, Parkinson’s, ALS and other similar disease in the brain as well as contributing to islet amyloid in type 2 diabetes and senile cardiac amyloidosis.
The solution is to remove these aggregates from the brain and other areas of the body using specialized antibodies that target them and remove them from the tissue. This could help to prevent or reverse the various amyloid-based diseases mentioned above.
Where are we now?
The work SENS Research Foundation funded at UT Houston in Sudhir Paul’s lab is now in the hands of his company Covalent Biosciences, hopefully we will hear some news from them in the near future.
Fortunately a number of alternatives are in development such as the GAIM system which has been funded by the Michael J Fox Foundation and appears capable of clearing multiple types of amyloids included those associated with Alzheimer’s, Parkinson’s and amyloidosis. The AdPROM protein targeting system also holds promise for selectively degrading target amyloids and other undruggable proteins to treat age-related diseases.
LysoSENS: Intracellular aggregates
In time the proteins and other components of our cells become damaged through the wear and tear of normal metabolism. Cells have a number of systems for breaking down unwanted materials, the lysosome is one of them. The lysosome can be considered to be a kind of cellular garbage disposal unit which contains powerful enzymes for breaking down unwanted materials. However, sometimes materials are fused together so well that not even the lysosome can break them down. This leaves the unwanted material sitting there and over time more and more of this material accumulates until it starts to interfere with the lysosome’s function. This is a problem for cells that have to last for a lifetime, such as heart cells and nerve cells and as more and more of these cells become dysfunctional due to the lysosome malfunctioning, age-related diseases are the result.
For example, in heart disease the macrophages are responsible for clearing away toxic byproducts of cholesterol to protect our arteries. The macrophages swallow these toxic materials and send them to the lysosome for disposal and recycling. However, over time their lysosomes become engorged with toxic materials they cannot break down which eventually kills them or immobilizes them leaving them embedded and dysfunctional in the artery wall. In time the numbers of these dysfunctional macrophages increase and form the plaques associated with atherosclerosis. Ultimately the plaques build up, the injury swells and eventually bursts causing blood blots triggering heart attacks and strokes.
The solution to this problem proposed by the SENS Research Foundation is to identify new enzymes able to digest these insoluble wastes and supply macrophages and other cells with them so they can break it down.
Where are we now?
Ichor therapeutics is taking SENS Research Foundation based technology to market for macular degeneration with a therapy that removes a Vitamin A derivative that accumulates in the eye and causes blindness. Ichor has successfully conducted a seed round and is now doing a 15 million dollar series A round. Less than a year away from human clinical trials.
Conclusion
There is much to be optimistic about and the ideas proposed by SENS over a decade ago and widely criticized are now being eagerly explored by researchers as it becomes ever more apparent that the aging processes are amenable to intervention. What was mocked just over a decade ago is now becoming an accepted approach to treating age-related diseases as the result continue to mount up in support of a repair based approach to aging. However we still lack complete knowledge on several age-related damages to progress to clinical trials in humans. This is why supporting fundamental studies on the main mechanisms of aging should remain the number one priority for our community.