Basic Stem Cell Math

Posted on by Paul Turek, MD

Guess how many human diseases are curable with stem cell therapy. Let’s make it easier. First, eliminate the unvalidated claims made by unlicensed stem cell treatments around the world that purport to cure everything under the sun. Then, remove bone marrow transplantation used for years to treat cancer. And the answer is….none. All that hype and yet no cures. Is stem cell technology failing us?

Be Careful What You Ask For

One of the most disappointing moments in recent memory is the unfolding of the first FDA-approved human embryonic stem cell trial in America. The goal was to mend and restore the broken backs of spinal cord injured patients. After enrolling only a couple of subjects into the trial, Geron Corp. closed their stem cell shop in late 2011. Was this problem too hard for stem cells to solve?
Maybe. In my view, it was simply too tall an order to be delivered by such a young science. Think about it: let’s magically repair something as complex as a spinal cord by painting it with a fancy stem cell cocktail.
Why not start a little simpler? Why try to solve complex calculus with little more than a geometry background?  Instead of going for the grand slam of mending hearts after attacks or restoring brains after strokes or trying to construct entire tissues and organs in dishes, why not start with base hit, or even a bunt?

Lower Hanging Fruit

Many of us believe that making sperm or eggs from stem cells is relatively hanging fruit in stem cell science. Altering the properties, behavior or function of a single cell type certainly appears to be a more basic “ask” of the technology than the Frankensian task of recreating an entire organ from scratch.
As examples, look what’s been accomplished over the past 3 years with stem cells in the field of reproductive medicine:

  1. Going from A to B and almost to C. Two types of human stem cells, embryonic and adult-derived, have been driven down the pathway toward sperm. A complete, mature sperm has not yet been produced, but some predict that it is not far off, maybe a couple of years away.
  2. Going from B to C. In mice, stem cells from the testicle (gonocytes) have been matured into fertile sperm. In turn, the mice derived from those sperm are fertile.
  3. Going from B to A. The testis stem cells of adult humans and mice have been transformed into embryonic-like stem cells in a dish.
  4. Going from A to D. In mice, embryonic and adult stem cells have been matured into functional eggs and fertile offspring have been created from those eggs.

Point is, scientists can now push and pull and prod and pester stem individual cells in all kinds of directions, and all the way to eggs and sperm and back. Yup, research in reproductive stem cells is moving fast. In fact, it is clear to me as an observer and participant in this field that the work needed to make artificial sperm or eggs for humans is more evolutionary than revolutionary at this point. Forget new math, this is old school science. In the words of the ionian Greek philosopher Pythagoras: “There is geometry in the humming of the string.”