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Stem Cells: What And Why?

Blastocyst, labeled in English


Stem cells are a topic that definitely causes tons of arguments based on a misunderstanding of what they are and what they are capable of. In my previous article Church and Scientific Advancement I wrote a fairly short description of what an embryonic stem cell is and where they come from.As I wrote, embryonic stem cells are derived from blastocysts that are basically left over after an in vitro fertilization. These blastocysts have never been inside a human body after their fertilization in a test tube. Interestingly, pregnancy does not really begin medically until the blastocyst is implanted in the wall of the uterus so the Christian opposition to stem cell research is questionable at best. Embryonic stem cells are isolated from the inner cell mass of the blastocyst before they flatten into a disk and form the three germ layers familiar to all biologists as the endoderm, ectoderm and mesoderm. For you biology majors and actual biologist reading this, before you complain I am specifically considering triploblastic animals and not diploblastic ones and yes I will address your favorite worms the Planarians.

Diagram of stem cell division and differentiation.

Division And Differentiation

Now that we understand how stem cells are isolated let’s examine why they are important and for that we will start from the inner cell mass separating into the three germ layers I mentioned above. Each of the three germ layers forms a ‘set’ of  systems in the growing human. For example from the ectoderm we get the central nervous system, the eye’s lens, the ganglia and nerves, pigment cells, head connective tissues, the epidermis, hair, and mammary glands. Each stem cell in the ectoderm undergoes a process of differentiation as it makes it’s ‘choice’ of what final cell it will become. This happens in each stem cell in both of the other two layers. While differentiation is a fascinating topic stem cells also de-differentiate but unfortunately in complex mammals [like us] de-differentiation is a really high risk of cancer which really is cell differentiation gone wild [that would be a great DVD, Cells Gone Wild: To Hot For TV].

As is clearly seen, embryonic stem cells are a great tool for medical research and an added benefit is that stem cells are practically immortal when living in a culture inside a petri dish. One of the interesting aspects of stem cells I want to discuss is regeneration. Regeneration is wound healing on a huge scale. Time for me to bring out the fairly well known human regeneration of blood from hematopoietic stem cells that are located in bone marrow. We have all lost blood from cuts or injuries at sometime during our lives and some of us have even donated blood a time or two. The blood we lost or gave away is regenerated. Some anemias are caused by missing, not enough or non-functioning hematopoietic cells.

Time for me to pull out the biologist’s favorite worm the Planarian as an excellent example of regeneration. The Planarian when cut will regenerate a full animal from each part. Doesn’t make a difference where it is cut or if the cut is horizontal or vertical. You can make multiple cuts, say into 6 pieces and each piece will grow into a full worm. This regeneration is caused by stem cells but in Planarian world they are known as neoblasts. Too bad we can’t use their stem cells in a human but the potential for medical research is clearly seen. Another familiar example is the common starfish.

Unlike Planaria, a common Newt will regenerate limbs and other body parts but not a full body. For example you can cut a limb off as close to the torso as you like or even down near the ‘wrist’ or ‘elbow’ and about two months later you will find a fully regenerated limb with all the nerves, blood vessels and muscle. That would be an impressive trick for a human. Humans can regenerate a liver, pretty much totally. Humans can regenerate bone but muscle regeneration is problematic. Nerve regeneration and circulatory system regeneration isn’t even worth mentioning. Humans can’t regenerate a lost limb and that seems to be why god doesn’t heal amputees. This is one reason there is so much to learn from stem cell research and a shame that the Church looks down upon it.

Some of you really smart readers, if you read this blog you are smart, might have noticed as the animal gets more complex [planarian, newt, human] regeneration becomes progressively less. As far as limbs we started out with planaria that can regenerate a full body from a part, then we visited newts and their limb regeneration and now we come to humans and our inability to regenerate limbs. There are three main reasons for our inability to regenerate limbs. One I spoke about earlier and that is the risk of cancer associated with de-differentiation. The other reasons are a possible loss of the genetic programming necessary and a lack of enough stem cells to do the job. The last reason is without question a deal breaker but both of the first two reasons definitely share in the problem. As far as limb regeneration in higher animals go [in this case a complex appendage] and the only example among mammals is the annual regeneration of deer antlers.

Yearly and at quite a brisk pace of 1-2 cm. per day deer antlers regenerate and add an extra point to their structure [has to happen fast since the antlers are what get them girls].  Antlers regenerate from two bony bumps on the deer skull called pedicles which are permanent fixtures on the foreheads of all male deer after they reach sexual maturity. The antlers are bone but they are covered during regeneration by a very vascular layer of skin called velvet. That is why there is medical interest in deer antlers especially since in the class of mammalia this is a unique occurrence.

After reading the above one can easily see the potential for what may very well be life saving medical applications as well as applications that could definitely enhance ones quality of life. I would think regenerating a lost limb like a newt does would definitely increase the quality of life for someone that has lost an arm in an industrial accident. It’s a shame that as a whole the church would like to stop stem cell research because they feel a ball of 50-150 cells that has never been inside a human body and has been fertilized in a test tube and has less cells total then the neurons in the brains of

  • Brain Of An Ant – 10000
  • Brain Of A Honeybee – 850000
  • Brain Of A fruit fly – 250000
  • Brain Of A cockroach – 1000000
  • Brain Of A Dog – 160000000
  • Brain Of A Cat – 300000000
  • Brain Of A Human – 100000000000
  • Just like god created fish and animals before man, it seems in this case the Church would rather protect a blastocyst with 0.5-1.0% the cells of an ant brain? This is what they claim has a soul even though it was fertilized in a test tube by a man [or woman] wearing a lab coat?

    [tweetmeme source=”noreligionblog” only_single=false https://noreligionblog.wordpress.com/2010/02/28/stem-cells-what-and-why%5D



    3 Responses

    1. Unfortunately those of us reading this agree with you. Wish we could find a cure for religious stupidity.

    2. I don’t think theists ever tried to quantify life, be it 1 cell or 1,000 cells. But as to whether or not conception is conception if it doesn’t occur in the human body that’s more philosophical, I suppose.

      As for my own definition, I’m not sure that a 1 year old human can survive on it’s own any more than a zygote, so is the 1 year old really living? And why can they put animals down to relieve their suffering but people can’t euthanasize someone who specifically asks to be taken out of their misery.

      Whether or not God exists is really irrelevant in all of these situations to me. :-/

      • The only reason it does matter is that because of the belief in god and the resulting religion, we have these ridiculous stumbling blocks to otherwise good science.

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