In recent years, there
has been significant attention from both the scientific community and the
public on stem cells, mainly due to their potential in medical applications
like tissue and organ transplantation, as well as in treating diseases such as
diabetes, Alzheimer's, and Parkinson's. However, the use of stem cells often
involves ethical concerns related to the destruction of human embryos and the
possibility of human cloning. This has sparked heated debates in both ethical
and political spheres, leading to limitations on further research.
To address these
concerns, induced pluripotent stem cells (iPS) were developed with the hope of
retaining the medical benefits of stem cells while alleviating ethical
criticisms. Stem cells emerge during the blastocyst stage of mammalian embryo
development, which is similar to the blastula stage in other animals. Embryonic
stem cells are versatile cells that can divide and differentiate into any of
the body's three germ layers (endoderm, mesoderm, ectoderm) and subsequently
form specialized cells of various types. Additionally, there are adult stem
cells, primarily found in bone marrow and umbilical cord blood, which play a
role in repairing and replenishing adult tissues and cells.
In 1998, James Thomson
made a significant breakthrough at the University of Wisconsin-Madison by
successfully isolating human embryonic stem cells. However, this achievement
was met with considerable controversy due to the source of these cells. The
ethical concerns surrounding embryonic stem cells were somewhat mitigated in
2006 when Shinya Yamanaka, at Kyoto University in Japan, reprogrammed adult
mouse fibroblasts (skin cells) to generate induced pluripotent stem cells
(iPS). Yamanaka further advanced his research in 2007 by successfully producing
iPS from human adult skin cells, a milestone later replicated by Thomson in the
same year.
During this process,
multiple transcription factors, which are proteins responsible for regulating
the flow of genetic information from DNA to messenger RNA, are introduced into
the skin cells. Yamanaka's groundbreaking work earned him a share of the Nobel
Prize in 2012.
Despite initial
excitement over the medical potential of iPS, enthusiasm has been tempered due
to differences between embryonic stem cells and iPS, as well as concerns about
the potential for iPS to induce cancers. As of now, iPS have not been approved
for clinical use in the United States.
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| Genetically reprogrammed adult cells, known as induced pluripotent stem cells, act as disease models and hold promise for treating various conditions like Alzheimer’s disease, spinal cord injuries, diabetes, burns, and osteoarthritis through cell-based therapies. |
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