Cloning Human Organs
Other People Are Reading
-
Cloned Organs vs. Donor Organs
-
Organ donation saves countless lives each year. However, the aftercare required lasts the rest of the recipient's life, compromises the immune system and can damage other healthy organs. This is because, while the donor's and recipient's blood types and Rh factors may match, their genetic differences trigger a powerful immune response on the cellular level. To keep the recipient's body from rejecting the new organ, the patient must take steroids and other immunosuppressive drugs. If a transplant recipient could receive an organ from a biochemically "perfect" match, it wouldn't trigger an immune response, thus eliminating the need for immunosuppressants.
Science still has only a partial understanding of the expression of one's genetic profile on the cellular level. Even if researchers could enumerate the entire set of cellular characteristics that trigger an immune response, medical technology is decades away from producing an effective and cost-effective way to permanently eliminate these characteristics from every cell in a hundred-million-celled organ.
Therefore, many in the biotechnology industry see cloned organs (literally, organs grown from the patient's own stem cells) as the most expedient approach toward solving the autoimmune problem in organ transplantation. A cloned organ would presumably be genetically and phenotypically indistinguishable from the existing, damaged organ. Thus it would possess none of the as-yet-undiscovered cellular immune response triggers.
How Could Stem Cells be Used to "Grow" an Organ?
-
At conception, all humans begin as a single cell: a fusion of the egg's and sperm's chromosomes. This cell divides rapidly ("cleavage") until it forms a hollow sphere of identical, undifferentiated cells. The cells receive different levels of chemical signals based on their orientation in the sphere, causing them to begin developing differently. As the embryo develops, the chemical signals sent to certain cells become more and more specific, leading them to grow into highly specialized tissues, which eventually develop into specific organs (e.g. heart, lungs, nervous system).
The original, undifferentiated cells formed during cleavage are known as "stem cells." Scientists believe that stem cells have the potential to develop into virtually any kind of specialized tissue provided they receive nutrients, protection and the proper regimen of chemical signals.
In a hypothetical organ cloning model, therefore, scientists would extract stem cells from a patient, using either saved umbilical cord tissue, modified adipose tissue (body fat) or possibly basal cells. In the laboratory, the cells would be transplanted onto a sparse matrix of microscopically thin fibers immersed in a nutrient-rich solution. Scientists would then treat the stem cells with a battery of chemical and physical stimuli to mimic the body's natural signals for differentiation. Once the stem cells developed into specific organ cells, they would be transplanted onto that same organ in a host organism. With no immune response triggered, these cloned cells would grow on the original organ until they became a mature, separate organ. However, as the cloned organ grew, doctors might need to perform a bypass or other vascular microsurgery to connect its blood vessels directly to the main arteries and vein. After reaching maturity, the cloned organ would be transplanted into the patient.
-
Where Would the Organ be Grown?
-
Individual cells can grow in a Petri dish. A cloned organ, however, would require the blood pressure, hormones and other homeostatic regulations that only a fully functioning body can provide. Therefore, the recipient's body would provide the best host organism in which to transplant the organ for growth. However, time might be a factor, or the patient might not be healthy enough for multiple surgeries. Therefore, scientists are currently exploring the possibility of growing cloned organs in genetically modified or immune-suppressed mammals such as pigs.
-
