regeneration

Regeneration

I am usually very positive about our experiences with Madeleine's treatment. I'm so very proud of my daughter. She is beautiful. She is capable. She is smart and charming. She is caring and empathetic. She is sweet and kind. She is friendly. And she is really really cute.

I love her little leg. I love it because it is part of her. Because she is affectionate toward it. Because her little heal looks just as it did prior to surgery.

I wish she had a foot. I don't admit this readily because it is morbid and unnecessary. I want to have moved on and I guess in a sense I have. But in my heart of hearts I wish that my little girl did not have to go through this life with a different form than others.

Last night I was thinking how great it would be if Madeleine could regrow her fibula bone. Her leg would slowly become longer and her little foot would sprout out the end and be completely functional.

In nature some creatures can do this: worms, starfish, salamanders (see below). I'm sorry to my readers who have children with upcoming surgeries. I message to you: Your child will amaze you. They will inspire people everywhere. They will exceed your expectations. I know this because that is how my daughter is. However, I still wish she had her foot. sometimes.

Newts and Salamanders
These amphibians
can regenerate a missing tail, legs, even eyes. This remarkable ability is
particularly pronounced in the larval stage. For this reason, larval salamanders
are favorites for doing research on regeneration. For example, cutting the tail
off a larval salamander initiates the following sequence of events:
A layer
of epidermal cells grows over and covers the stump.
A mass of
undifferentiated cells — called the blastema — develops just beneath.
Muscle
and cartilage form in the regrowing tail.
The notochord
and spinal cord grow out into the regrowing tail.
After a few weeks, a new,
fully-functional and anatomically-correct tail is complete.
The MechanismFor
years, it has been unclear as to whether this regeneration depends on
a
population of pluripotent
stem cells that have resided in the animal body prepared for such an event
(as occurs in the hydra) or
the dedifferentiation of specialized cells, e.g.
muscle and cartilage cells, in the stump.
The answer appears to be both.
Stem cells in the spinal cord migrate into the regrowing tail and
differentiate into several cell types, including muscle and cartilage. Although
the stem cells are ectoderm,
they are able to develop into mesoderm.
Muscle cells in the stump migrate into the blastema while
reentering the cell
cycle to produce thousands of descendants;
dedifferentiate as they do
so; that is, they lose the characteristic proteins, etc. of muscle
cells.
Even though there is as yet no sign of a tail, its final pattern is
established during this process for if the blastema is removed and transplanted
elsewhere, it will continue the process of regenerating a tail.
Finally the
cells of the blastema differentiate into all the cell types — nerve, muscle,
cartilage, skin — used to build the regenerated tail.
Mammals
Don't we
wish that we had the same powers of regeneration that salamanders do: able to
regenerate a severed spinal cord or grow a new heart!
But unfortunately, we
cannot. We can regenerate some skin and a large amount of liver. But that's
about it.
Just why we are so limited is not known (but is the subject of
intense research). Much of the excitement of research on stem
cells is because of the hope that they may provide a means of regrowing
damaged or lost tissues or even organs.
Genetic Control of RegenerationA
number of genes have been found to implicated in regeneration. One of the most
potent of these is Wnt.
Injection of agents (e.g. antisensense
RNA molecules) that interfere with the Wnt/β-catenin
pathway
blocks limb regeneration in salamanders and
promotes head
formation in regenerating
planarians, while
injection of agents that enhance the Wnt/β-catenin
pathway
enable chicks (that, like mammals, are normally incapable of
regenerating limbs) to regenerate a wing;
cause a regenerating planarian to
form a tail where a head should go.