But what actually is stem cell therapy? What are the stem cells?
In layman’s language, stem cells are a type of cells from which potentially all other types of body cell can be derived. They keep dividing and renewing themselves without becoming a specific cell type. Even though stem cells are unspecialized type of cells, they can give rise to all types of specialized cells for example cardiac cells, neural cells, kidney cells and so on which lose the capacity to divide or proliferate. The ‘adult stem cells’ have been identified that exists in our body tissues and circulate in blood. In labs, adult stem cells generally give rise to the type of cell from where they are derived. Now-a-days stem cells are isolated and enriched from tissues and grown in culture dishes in laboratories for the research purposes.
Source: grosovsky.wikispaces.umb.edu
However, initially young embryos were considered to be the sole source of stem cells, called “embryonic stem cells”. In fact an organism’s whole body has been derived from one stem cell that is zygote. After an egg, a female gamete, gets fertilized by a male gamete, a sperm, it forms a zygote which gives rise to the complete organism after several cell divisions and differentiation. The research leading to clinical use of embryonic stem cells has been banned in many countries due to obvious ethical concerns.
Source:www.abpischools.org.uk
The embryonic stem cells derived from early embryo possess the capacity to keep renewing themselves without becoming any specialized type of cells in laboratory as opposed to the adult stem cells, which lose this potential after few division cycles. This could be the limitation of the adult stem cells and may handicap their use in the clinical application.
Before going further to see how scientists found answers to these limitations, let’s see how did scientists thought that stem cells could potentially exit in the adult tissues as well? The concept of their existence in somatic tissue, other than gonads where male and female gametes are produced, came from the fact that to keep the body healthy and repair it from time to time one would require a pool of cells with potential to renew themselves and form different types of cells and tissues in body. The scientists started looking for ‘stem cells like cells’ in the blood and other tissues. Using different stem cells markers, now such cells have been identified in many tissues. In fact, the bone marrow derived stem cells or “hematopoietic stem cells” are the major source of adult stem cells that are actually being utilized to treat some blood disorders.
Source: stemcells.nih.gov
Indeed, unabated growth of cancer and remission of cancers after treatment has been identified to be due to the presence of “cancer stem cells” which are found to be hard to kill by radiotherapy or chemotherapy and bounce back after the treatment regimen is over.
Now let’s come back to our original question about stem cell therapy.
Addressing the road block for isolating adult stem cells and maintaining their “stem-ness” and to coax them to the lineage that one wants, Dr Yamanak, a Nobal Prize Winner of 2012 for physiology or Medicine, identified that normal somatic cells can be induced to become stem cells by modulating a set of at least four transcription factors. Transcription factors are specialized proteins that are formed in cells to regulate the expression of other proteins. These stem cells are called induced pluripotent stem cells (iPS cells).
The iPS cells have ability to divide regularly and can be transformed into any cell type or tissue as regulated by specific set of transcription factors. This discovery removed both the limitations of adult stem cells and has obvious clinical implications. Scientists have successfully tried to coaxed iPS cells from one tissue to transform into another cell type. For example stem cells derived from skin fibroblasts were made into cardiomayocytes by regulating a set of key transcription factors.
Source: stemcells.uct.ac.za
The technological feasibility to make the iPS cells and potentially transform them into organ of choice is complete. Scientists now believe that it will be possible to use the patient’s cells to make iPS cells and transform them into specialized tissue as may be needed. This will also ensure that tissue thus formed may not be rejected by the patient’s immune system.
It appears that stem cell therapy is certainly not a perturbed dream but a potential cure for many diseases and will be a paradigm shift, if not already, in the health care sector.
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