Senescent cell clearance has been all the rage for the past two years or so; Lifespan.io has hosted the MMTP project, which focused on testing senolytics in mice, and this was later followed by CellAge’s project to design synthetic biology-based senolytics.
There are other companies that have joined the race to add senescent cell clearance to the standard toolkit of doctors, such as Unity Biotechnology and Oisin Biotechnologies.
Unity’s approach uses a drug-based approach to senolytics and is scheduled to enter human clinical trials in 2018. A number of other research teams are also developing drug-based approaches to removing senescent cells, and the competition looks set to be fierce in this area in the coming years.
Oisin’s approach makes use of suicide genes and hopefully will be tested in clinical trials not too far into the future, thanks to venture funding presently being collected. If this system can be made to work, it will allow very selective targeting of senescent cells by destroying only those giving off a target gene or genes. Thus, if a unique gene expression profile for senescent cells is determined, it would mean only those cells were destroyed, with less risk of off-target effects.
Oisin owes its existence to the SENS Research Foundation and the Methuselah Foundation, which provided the necessary seed funding. Kizoo Technology Ventures has also invested in Oisin.
In order to eliminate unwanted cross-links, the SENS approach proposes to develop AGE-breaking molecules that may indeed sever the linkages and return tissues to their original flexibility. Of course, in order to do so, crosslink molecules need to be available for research to attempt to combat them with drugs, and especially in the case of glucosepane, this has been a problem for years.
Glucosepane is a very complex molecule, and very little of it can be extracted from human bodies, and not even in its pure form. This has been greatly hampering the progress of research against glucosepane, but thankfully, this problem is now solved thanks to a collaboration between the Spiegel Lab at Yale University and the SENS Research Foundation, which financially supported the study. It is now possible to fully synthesize glucosepane, allowing for researchers to create it on demand and at a cost-effective price.
The Spiegel Lab’s scientists are now developing anti-glucosepane monoclonal antibodies to cleave unwanted cross-links. The collaboration between the Spiegel Lab and SRF dates all the way back to 2011, but it was in 2015 that the Lab announced its success and published a related paper in the journal Science.
Mitochondrial mutationsMitoSENS: How to solve this problem, and how far we’ve got
Cell nuclei are far less exposed to free-radical bombardment than mitochondria, which makes nuclear DNA less susceptible to mutations. For this reason, the cell nucleus would be a much better place for mitochondrial genes, and in fact, evolution has driven around 1000 of them there. Through a technique called allotopic expression, we could migrate the remaining genes to the nucleus and solve the problem of mitochondrial mutations.
Human-made allotopic expression was a mere theory until late 2016, when, thanks to the successful MitoSENS crowdfunding campaign on Lifespan.io, a proof of concept was finally completed. Dr. Matthew O’Connor and his team managed to achieve stable allotopic expression of two mitochondrial genes in cell culture, as reported in the open-access paper they published in the journal Nucleic Acids Research. As Aubrey de Grey himself explains in this video, of the 13 genes SRF is focusing on, it’s now managed to migrate almost four.
This had never been done before and is a huge step towards addressing this aspect of aging in humans. In the past few months, the MitoSENS team has presented its results around the world and worked on some problems encountered in the project.
Lysosomes are digestive organelles within cells that dispose of intracellular garbage—harmful byproducts that would otherwise harm cells. Enzymes within lysosomes can dispose of most of the waste that normally accumulates within cells, but some types of waste, collectively known as lipofuscin, turn out to be impossible to break down. As a result, this waste accumulates within the lysosomes, eventually making it harder for them to degrade even other types of waste; in a worst-case scenario, overloaded lysosomes can burst open and spread their toxic contents around.
This eventuality is especially problematic for cells that replicate little or not at all, such as heart and nerve cells—they’ve got all the time in the world to become swamped in waste, which eventually leads to age-related pathologies, such as heart disease and age-related macular degeneration.
LysoSENS: How to solve this problem, and how far we’ve got
As normal lysosomal enzymes cannot break down lipofuscin, a possible therapy could equip lysosomes with better enzymes that can do the job. The approach suggested by SRF originates with ERT—enzyme replacement therapy—for lysosomal storage diseases. This involves identifying enzymes capable of breaking down different types of intracellular junk, identifying genes that encode for these enzymes, and finally delivering the enzymes in different ways, depending on the tissues and cell types involved.
SRF funded a preliminary research project on lipofuscin clearance therapeutics at Rice University and another project relating to atherosclerosis and the clearance of 7-ketocholesterol (a lipofuscin subtype), which eventually spun into Human Rejuvenation Biotechnologies, an early-stage private startup funded by Jason Hope.
A LysoSENS-based approach is currently being pursued by Dr. Kelsey Moody, who used to work at SRF. Dr. Moody has been working on an ERT treatment for age-related macular degeneration. The treatment consists in providing cells of the macula (a region of the eye’s retina) with an enzyme capable of breaking down a type of intracellular waste known as A2E. The treatment, called LYSOCLEAR, is being worked on by Moody’s company Ichor Therapeutics, which earlier this year has announced a series A offering to start Phase I clinical trials of its product.