Stem Cell Basics – Replacement Organs

Your Own Stem Cells Could Grow a Replacement Organ. All About Stem Cells.

Stem cells likely foretell the death knell of the transplant industry. The ability to grow new tissue from one’s own stem cells is already in use and will burgeon into a huge new medical area. Furthermore, no embryonic stem cells are used, so that controversy is completely avoided. Recently, researchers at Cincinnati Children’s Hospital have made fully functional tiny humanstem_cells_home stomachs. There is also significant progress with livers, kidneys, and other assorted organs and tissues. These stem cells are forming complex structures that would certainly be suitable for grafting and one day, no doubt, suitable for replacement parts. There are, needless to say, numerous technical details to be worked out (like getting arteries and nerves to grow into the replacement organ), but few doubt this is a significant part of medicine’s future.

Stem cells appear to already have made headway into the cosmetics industry. I just couldn’t resist the image. The product apparently uses stem cells from plants! Though the logic of this isn’t exactly clear, just imagine the possibilities. Be careful where you spray it.

The new procedures use adult stem cells, normally taken from the same adult that is going to get the replacement tissue. These stem cells are also not the controversial embryonic type, so various ethical issues are also completely avoided. Embryonic stem cells were never going to work well anyway. Any organ or tissue made from different DNA from the recipient would tend to be rejected like transplanted organs today. Well, not quite as strong an immune rejection but still quite strong. The recipient would have to take immunosuppressive drugs, which have their own serious consequences. (Organs or tissue made from a person’s own true stem cells would work. These are found in the umbilical cord, which can be frozen and saved for later use.) Since adult stems cells are taken from the person that will ultimately receive the tissue or organ, there is no rejection issue. The immune system won’t reject locally grown stuff.

What are adult stem cells? A newly conceived fetus is a ‘totipotent’ stem cell. That means just what it seems like – you can make anything out of it. That initial cell divides and divides into more totipotent cells, but within a short time, these cells start to specialize (called differentiate) into the various cells that will make up the baby.

But not completely. Some only differentiate a bit, but can still make a variety of cells. The cells are called ‘pluripotent’, and although down the pecking order from totipotent, they are still quite powerful. They can replicate into copies of themselves, and they can differentiate down into a variety of other cells. These pluripotent cells can still be found in the adult body. They aren’t numerous, but they are there, and if isolated, they can be gotten to reproduce and with further trickery, gotten to differentiate into the desired organ or tissue.

Only totipotent and pluripotent are considered to be true ‘stem’ cells, but the pecking order extends on downward. The pluripotent cells differentiate into multipotent cells, then oligopotent, producing just a few types. These lessor cells can still replicate, so they are sort of ‘junior stem cells’. Their official name is progenitor cells. The end-of-the-line cells cannot replicate or differentiate at all. Your skin, at least the part you can see, is in this state.

The stem cells can vary their rate of renewal. In normal times, they will regenerate new tissue at a regular rate, but if there is a need, say a wound, they can move at a much faster pace.

All the body’s tissues that are routinely replaced use the stem cell hierarchy. This includes the liver, the skin, the stomach, the intestines, and many other items. For instance, the skin you can see is at the final step in the replacement chain. It can’t replicate and it is fully differentiated. New skin is getting created underneath by stem cells (or possibly the junior versions). The stem cells that are creating the new skin stay put, as far as possible out of harms way, replicating themselves as needed. It is good that they are well protected. If they get damaged, there is the possibility of producing damaged daughter cells. Most cancers have this sort of origin. Since the stem cells are well preserved, the replacement tissue is almost as good as new, but not quite. We do age.

The miniature stomachs reported above are a good indication of the potential power of this sort of work. A stem cell, properly triggered, not only knows how to grow stomach tissue, but also how to form the hollow 3-D structure. How cool is that?




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