nautil.us | What impact will your work have on aging research?
I’m studying whether we can separate the process of functional
reprogramming of cells from the process of aging reprogramming of cells.
Typically these two processes happen at the same time. My hypothesis is
that we can induce cellular rejuvenation without changing the function
of the cells. If we can manage to do this, we could start thinking about
a way to stall aging.
What is the difference between functional and aging reprogramming?
The function of a skin cell is to express certain proteins, keratins
for example that protect the skin. The function of a liver cell is to
metabolize. Those are cell-specific functions. Reprogramming that
function means that you no longer have a liver cell. You now have
another cell, which has a totally different function. Age, on the other
hand, is just the degree of usefulness of that cell, and it’s mostly an
epigenetic process. A young keratinocyte cell is younger than an older
keratinocyte but it is still a keratinocyte. The amazing thing is that
if you take an aged cell that is fully committed to a certain function,
and you transplant its nucleus into an immature egg cell called an
oocyte, then you revert its function to a pluripotent, embryonic one,
which means it can become any other cell of the body—and you also revert
the age of that cell to the youngest age possible. It’s mind-blowing to
me.
This could be a paradigm shift in the way we approach aging.
How can you make a pluripotent cell in the lab?
Historically, the way pluripotency was induced from non-pluripotent
cells was by doing the procedure I’ve just described: so-called “somatic
cell nuclear transfer.” You take a non-pluripotent cell, let’s say a
liver cell or a fibroblast or any other cell. You isolate its nucleus
and transplant it into an egg, an oocyte, which was previously deprived
of its own nucleus. This produces what is known as a reconstituted
embryo, in which the cytoplasm is the original egg’s cytoplasm, and the
nucleus is the nucleus of the cell that you isolated. The egg has this
amazing ability to reprogram the nucleus to an embryonic-like state.
Since embryonic cells are naturally endowed with a pluripotency program,
if you then take that embryo and put it in culture, you can establish
pluripotent stem cell lines. Shinya Yamanaka, a Japanese researcher that
got a Nobel prize for his work three years ago, demonstrated another
technique, called induced pluripotent stem cells, or iPS. He showed that
if you simply boost the expression of four particular transcription
factors inside a non-pluripotent cell for a few weeks, you also could
create an embryonic-like program. The factors also somehow wipe off the
epigenetic memory of the cell, making them younger.
How close are we to using pluripotency induction in therapies?
iPS in mice was described in 2006, and in humans in 2007, so it’s
been already 10 or 11 years. The first clinical trials using iPSCs are
just about to get to early phase I and phase II. There has been a lot of
hope and promise but it’s been a little slow. The reason being that
when it comes to clinical applications, you have to consider a number of
complications. You need to know how to make the cells very efficiently,
and then they need to be safe. There will be more clinical trials
coming up based off iPSs. For example, I am collaborating with an
iPS-based platform for the cure of a skin disease called epidermolysis
bullosa. We’re trying to move this to the pre-clinical stage over the
next few years, and then if we pass that, we will potentially start
moving into a phase I clinical trial. Things are moving forward pretty
fast now.
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