Stem cells can be found in almost every multicellular living organism on the planet.
It plays a crucial and irreplaceable part in our growth from embryonic development to adulthood.
Stem cells are classified as undifferentiated cells, one that has yet to evolve or be assigned to a specific function by the host body.
A stem cell would continue to divide, through the process of mitosis, until it eventually matures into a differentiated cell, which would either be committed as a building block for the hosts, or used in a regenerative function.
There are various terms are used to classify different types of human stem cells. However, the three most common ones are:
(i) Embryonic Stem Cells
Embryonic stem cells are ordinarily obtained from tissues harvested from the epithelial layer (blastoderm) and fluid-filled cavity (blastocoel) of the blastula during the blastocyst stage of a fetal development period, usually four to six days after fertilization. Primarily sourced from in vitro fertilized embryos.
(ii) Somatic Stem Cells
Somatic cells are harvested from adult human tissues with active regenerative cycles, such as skin, lining of the small intestine, blood vessels, liver, brain and bone marrow.
(iii) Induced Pluripotent Stem Cells (iPS cells)
iPS cells are created by reprogramming ordinary cells using RNA virus. These cells undergo gradual changes that strip them of their original cellular memories and eventually mimic the malleable characteristics of embryonic stem cells. iPS production remains an unstable process and regularly produces unforeseen attributes.
All three sources of stem cells offer differing growth and maturity characteristics, which influence their potential usage. However, embryonic stem cells are regarded as the superior of the three.
Scientists have been aware of stem cells and the potential it offers for almost four decades, but the first real breakthrough only came in 1998, when a team lead by Dr. James Thompson from the University of Wisconsin discovered a method to isolate and propagate the cells from human embryos. Despite the huge potential behind stem cell technology, Dr. Thompson’s breakthrough raises serious moral questions over the use of human embryos to harvest stem cells.
Difficult questions, such as the right of the embryo or of its legal status as a person - ordinarily heard in any debate involving the issue of abortion – became a hot topic of discussion. Does the potential benefit of this technology to humanity justifies the ‘farming’ and post-harvesting destruction of these embryos? The discovery of undifferentiated somatic stem cells, and more recently, iPS cells, have lessened the demand for embryonic stem cells, but it still remains the most sought after for its simpler properties and more expansive development potential.
But why is there such excitement over the stem cell technology?
The science of stem cell technology offers the opportunity to understand the biological and chemical mechanics of human development, which in turn will offer an understanding of how diseases develop and of the methods required to suppress them. It also presents an opportunity for the advancement of the still new field of regenerative medicine - for cell, tissues, limbs and organs.
Mastery of these stem cell technologies will revolutionize modern medicine. Diseases (such as cancer, Parkinson’s, multiple sclerosis), limbic defects (birth or accident) and damaged organs would all be curable. We can grow what is needed, and prevent what isn’t. Even Oscar Goldman's famous line, "We can rebuild him...we have the technology,"no longer seem as far-fetched.
Nevertheless, full mastery of stem cell technology remains decades away. Hurdles are aplenty, and there are huge gaps in our knowledge. But there have been some practical, life-saving even, application of stem cell technology. According to the National Marrow Donor Program, hematopoietic stem cells (blood forming cells) from the bone marrow and umbilical cord blood are used in an estimated 50,000 hematopoietic cell transplants annually worldwide to treat patients with life-threatening malignant and non-malignant diseases such as,
• Leukemias and lymphomas
• Severe aplastic anemia and other marrow failure states
• SCID and other inherited immune system disorders
• Hurler's syndrome and other inherited metabolic disorders
• Familial erythrophagocytic lymphohistiocytosis and other histiocytic disorders
Stem cell research has seen its potential for progress being curtailed drastically by a myriad of political, religious and ethical issues - and there is even opposition from within the medical community itself. In 2001, former President Bush limited federal funding of stem cell research to 21 non-embryonic stem cell lines - a limitation which was revoked by President Obama in 2009, expanding the cell lines for federally funded research. The debate does not appear to be reaching a conclusion anytime soon, and serves as yet another divisive political tool.