Mco
A
Can Humans Live Forever?
Amit Anand, Antony Holmes, Michael Li
Introduction
Telomeres
Can Humans Live Forever?
Human beings do not live forever because the human body
cannot maintain itself indefinitely. We either grow old or we get
diseased.
The Pessimist
Human cells do not have the
ability to divide indefinitely due to
shortening telomeres.
The Optimist
Our knowledge of telomeres
and telomerase allows us to
manipulate them.
Ageing is currently an inevitable consequence of living and a lot of
research has been done into prolonging youth or even stopping
ageing completely.
Sometimes the cells and organs
in the body fail.
Stems cells could be made to
differentiate into any type of
cell in the body as
replacements.
Diseases interfere with the body’s major functions and may lead
to death.
We focus on some of the problems associated with ageing and
diseases from the point of view of what is happening at the cell
level and try to address what has been done to help cells function
correctly.
There may be defects on a
genetic level.
Gene Therapy allows
intervention at the genetic
level.
Telomeres are the ends
of the chromosome.
Limit on cell division
For the human body to maintain its functionality,
cells must continually divide.
Healthy cells can only divide around 100 times and
this is a serious limitation if you want to live forever.
As each cell divides, the length of the telomere
sequence decreases.
Keep the telomere length constant and the cell can
undergo an incredible number of extra divisions.
“Human beings do not live forever
because the human body cannot
maintain itself indefinitely.”
Telomere is extended by
telomerase.
Stem Cells
When things go wrong
It is unavoidable that some cells of the human body will
become dysfunctional through disease or through faults in
cell division.
Skeletal muscle stem cells being
inserted in damaged cardiac
muscle to repair it.
“Well If my telomeres are decreasing
with every cell division then there is
no way I can live forever?”
Stem cells are cells which can be converted into any type
of cell. On division they can either become stem cells
again or develop into cells with specialized functions, such
as muscle cell, red blood cell, or a nerve cell.
There are a few upcoming
techniques by which your genes
can be changed. In-vitro cell
division capacity was increased to
600+.
There are two types: embryonic stem cells and adult stem
cells. Work is being done to use stem cells to replace
dysfunctional cells and organs. This suggests the potential
to replace parts of the body as they wear out.
(Clontech Infinity line of Telomerase immortalized cells)
This is the part of the DNA
the polymerase can now
replicate.
Gene Therapy
Intervention
If we can intervene and correct errors in our genes
then it becomes possible to eradicate diseases and
defects.
Genes encode instructions that are transcribed into
RNA and finally translated into proteins to carry out
some function. If the gene is damaged it may cause
the wrong protein to be formed so the cell does not
function properly.
Chinese State Food and Drug Administration
(SFDA) approved on Jan. 20 the recombined
human p53 adenovirus injection
The chromosome shortens with
each division because the last
RNA primer of the lagging strand
cannot be replaced.
So how does it work?
We can insert correct genes to replace faulty
ones. A carrier molecule called a vector is used to
deliver the gene. Normally this is in the form of a
virus which has been modified to insert specific
genes into its host’s DNA.
We can selectively switch certain genes on or off
to regulate the function of the cell if it is not
possible to correct functionality.
It is also possible to introduce DNA directly into
the cell but this is less effective and requires a lot
of DNA. There are a only a few cell types which
respond properly to this method.
Children with Progeria have telomeres that
are much shorter than in normal cells and
show signs of early ageing: baldness,
prominent scalp veins and eyes, small jaw,
heart disease and artery disease.
Conclusion
Obstacles
At present, human beings are a long way from immortality but we are slowly
removing the obstacles that prevent us from living forever.
The techniques outlined are just a few of the many efforts that will contribute to
increasing human life expectancy.