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We all sense the passage of time, don't we? But what exactly is aging? Is it simply the accumulation of years, or is there something more fundamental happening within our very cells?
Scientists have been grappling with this question for ages, leading to an array of ideas about how and why we age. You might have come across some of these approaches – perhaps strategies focused on diet, exercise, or even more radical interventions aimed at extending our lifespan (all the things Bryan Johnson does).
But what if we could tackle aging at a more fundamental level, right down to the cells themselves? Imagine our cells carrying not just the blueprint of our being (our DNA), but also a kind of cellular "age marker." What if we could learn to manipulate these markers? This is where the groundbreaking work of companies like NewLimit comes into play. They're taking a unique "reprogram approach," diving deep into the realm of epigenetics to understand and potentially reverse cellular aging. How exactly do they aim to achieve this? Let's delve into their fascinating strategy.
Epigenetics
So, we were just talking about how NewLimit is looking at our cells and their "age tags." But what exactly are these tags they're so interested in? Have you ever thought about how it's possible for you to have so many different kinds of cells – skin cells, brain cells, liver cells – when they all contain the exact same DNA, the same fundamental blueprint? It's kind of mind-blowing when you think about it, right?
Well, this is where something called epigenetics comes into the picture. Think of our DNA as a massive instruction manual. Every cell in your body has the same manual. But a skin cell doesn't need to read the instructions for being a liver cell, and vice versa. So, how do they know which parts of the manual to read and which parts to ignore?
That's where these "epigenetic tags" come in. Imagine little sticky notes or labels that sit on top of the DNA.
These modifications don't change the underlying DNA sequence itself, but they act like switches, telling a gene whether to be "on" or "off," or somewhere in between.
So, now that we have a basic idea of what epigenetics is – these "sticky notes" on our DNA that control gene activity – we can start to think about how this relates to aging.
Scientists have already figured out how to manipulate cell age and cell type, as illustrated in the below diagram. By adding a specific set of four proteins called transcription factors (OCT4, SOX2, KLF4, and MYC) to an old skin cell, they can essentially hit the "reset" button and turn it into a young embryonic stem cell. Think of it as not just making the cell younger, but also giving it the potential to become any cell type in the body.
The next diagram shows another interesting possibility: we can also change the type of a cell – say, turning an old skin cell into a neuron or a liver cell – by using a different cocktail of transcription factors (1-6). In this case, the cell's identity changes, but it remains old.
Now, here's where NewLimit's approach, and the concept of partial reprogramming, becomes really exciting, as shown in the below diagram.
Their goal isn't to completely rewind a cell all the way back to a stem cell. Instead, they're aiming to discover how to change the age of a cell – to make an old skin cell a young skin cell – without changing its fundamental identity. They want to find the right "recipe" of transcription factors (those "? TFs" in the diagram) that can rejuvenate the cell while it remains a skin cell. This "partial reprogramming" is like carefully turning back the clock on a cell without erasing its memory of what it's supposed to be.
Why is this partial approach so interesting? Well, completely reprogramming a cell back to a stem cell, while it makes it young, also erases its specialized function. A skin stem cell isn't doing the same job as a mature skin cell that protects our body. Partial reprogramming offers the potential to rejuvenate cells while keeping their essential functions intact.
So, the big question then becomes: how do you actually find these magic transcription factors that can partially reprogram a cell? That's where NewLimit's innovative "discovery engine" comes into play, which we can explore next.
Okay, so we've established that NewLimit is on the hunt for these "magic" transcription factors to partially reprogram cells. But how do they actually find them? That's where their clever "discovery engine" comes into play.
Think of it as a multi-stage search, where they start with a huge number of possibilities and gradually narrow it down. The image you provided outlines this process:
- In silico Screening: They begin with a massive number of hypotheses (permutations of TFs) – around . This is like casting a very wide net, using computer simulations to predict which transcription factors might have the desired effect.
- Ensemble Pooled Screening: Next, they move to ensemble pooled screening, reducing the number of hypotheses to . This involves testing groups of transcription factors together to see if they have any effect on cell age.
- Single Cell Pooled Screening: They then refine the search further with single-cell pooled screening, bringing the number of hypotheses down to . Here, they look at the effects of transcription factors on individual cells, giving them more precise data.
- Cell type-specific Functional Assays: After this, they move to cell type-specific functional assays, reducing the number of hypotheses to . This step involves testing the most promising transcription factors in specific cell types (like skin cells or liver cells) to see if they truly rejuvenate them while maintaining their function.
- Indication-specific Preclinical Models: Finally, they test the most promising candidates in preclinical models, further narrowing the field to . This is where they start to see if these factors can have an effect in more complex systems.
It's a bit like a funnel, starting with a huge number of ideas and gradually filtering them down to the most promising candidates. This multi-step approach allows NewLimit to systematically explore the vast landscape of transcription factors and identify the "recipes" that can effectively and safely partially reprogram cells.
So, NewLimit has this sophisticated engine to find the right combination of factors. Now, let's think about how they actually test these factors. The next image, "How can we discover reprogramming factors?", gives us a glimpse into their innovative approach compared to more traditional methods.
The traditional way of searching for these reprogramming factors is quite laborious. It involves testing thousands of individual combinations in separate test tubes. Imagine having one test tube for factor A, another for factor B, then one for A and B together, and so on. As you can see, with potentially millions of combinations of transcription factors, this approach becomes incredibly time-consuming and expensive. The image points out that the costs scale linearly with the number of combinations. Also, given that aging is most likely a function of multiple genes, you need to measure the activity (read-out) of multiple genes (instead of a single one).
NewLimit is taking a much more streamlined approach. They're using a technique that allows them to test many combinations of TFs simultaneously in a single culture dish. They create a "reprogramming factor pool" – a mix of different potential factors. Then, they can introduce this pool into cells in a single dish and use advanced sequencing techniques to read out the effects of many different combinations at once. The image indicates they can get around test gene activity of multiple genes for each combination of TFs from a single dish, allowing them to test thousands of hypotheses in parallel.
This high-throughput screening dramatically speeds up the discovery process. Instead of laboriously testing each combination one by one, they can analyze the effects of many different "recipes" of transcription factors simultaneously. This allows them to quickly identify promising candidates that can then be further investigated in the later stages of their discovery engine.
So, after NewLimit uses their high-throughput screening to identify promising combinations of transcription factors, the next crucial step is to figure out which of these combinations are actually working to rejuvenate the cells. The image you've now shared, "How NewLimit's partial reprogramming screens work," gives us a glimpse into this process.
They start with human T cells, which are immune cells. They have both young and old T cells in their experiments. Then, they introduce their "TF Pool" – that mix of potential reprogramming factors we talked about. To control when these factors are active, they use a "Transgenic drug inducible DNA barcoded" system. This allows them to turn the factors on and off at specific times, giving the cells a "Reprog Pulse" – a period where the reprogramming factors are active – followed by a "Reprog Chase," where they observe the effects.
The key here is the "Single cell multi-omics" analysis. This advanced technique allows them to look at many different aspects of individual cells after they've been exposed to the reprogramming factors. They can measure things like gene expression (which genes are turned on or off), protein levels, and even the overall state of the cell.
Finally, they use "In Silico demultiplex & phenotype" to analyze this massive amount of single-cell data. By using computational tools, they can figure out which combinations of transcription factors (remember those DNA barcodes?) led to the most significant changes in the cells, ideally making the old cells look and act more like young cells. This step helps them identify the specific "recipes" that are truly effective in partially reprogramming the cells.
It's a sophisticated process of controlled activation of potential factors, followed by detailed analysis at the single-cell level to pinpoint the winners. This allows them to move beyond just seeing if something happens to understanding how and why it happens at a very granular level.
Alright, so after NewLimit has identified transcription factor combinations that seem promising in making old cells look younger based on their multi-omics analysis, the next crucial question is: do these cells also act like young cells? As the next image aptly puts it, "Function is the final boss."
Just looking younger isn't enough; the cells need to regain the functional capabilities of youthful cells. This is where NewLimit puts these partially reprogrammed cells through a series of rigorous functional assays. The image outlines several examples of these tests:
- Proliferation (Acute stim.): Can the rejuvenated cells still divide and multiply like young cells when stimulated? This is a fundamental characteristic of youthful cells.
- Persistence (Chronic stim.): Can the cells maintain their function and survival over longer periods, similar to young cells facing chronic stimulation?
- Targeted Killing: In the case of immune cells like T cells (which they used in their initial screens), can the reprogrammed cells effectively target and eliminate threats, a key function of young, healthy immune cells?
- Antibody Response: For other immune cells like B cells, can they still produce antibodies effectively when challenged, a crucial aspect of a functional immune system?
- Stemness (Sorting): Do any of the reprogramming approaches induce a return to a more stem-like state within the specific cell type, which might be beneficial for regeneration?
These are just examples, and the specific functional assays NewLimit uses will depend on the type of cell they are trying to rejuvenate. The key takeaway is that they don't just rely on molecular markers that indicate a younger state; they rigorously test whether the cells can actually perform the jobs that young, healthy cells do.
This focus on function is critical because the ultimate goal isn't just to make cells look younger on a lab test, but to restore their youthful activity within the body, potentially leading to real benefits in terms of health and longevity.
TODO
NewLimit’s throughput (2023)
