stem cells

• Some believe that the embryo has the status of a human being as it has the potential to become one. they see Embryonic stem cell research as EQUIVALENT to murder.
• Some object to extracting stem cells from an embryo to make replacement body cells is treating the embryo as just a source of spare parts.
• Claims of the benefits of embryonic stem cell research are over-rated as there are few (if any) examples of success in medical applications
• Adult stem cell treatment is established, have produced some results and there are fewer ethical issues involved. Thus adult stem cell research may be able to make greater advances if more money and resources were channeled into it instead of embryonic stem cell research.
• Current harmless applications may lead to abuse in the future. Once human status is denied to embryos, this precedent may extend to other categories of human beings such as the disabled or the elderly
• Possibility of unforeseen consequences in treated patients such as possible risks of tumor formation, immunological reactions, unexpected behavior of the cells, and unknown long-term health effects.
• As embryonic stem cell research is expensive, funds can be channeled to treat other more treatable diseases.

  For donors of eggs, embryos or tissues, there are issues of informed consent, understanding of research aims and privacy.
• Embryos are not equivalent to human life:

  Embryos are not conscious, cannot feel and cannot survive outside the womb.
• Blastocysts are a cluster of human cells that have not differentiated into distinct organ tissue, making cells of the inner cell mass no more "human" than a skin cell. Some believe life only begins when the heartbeat develops (during the fifth week of pregnancy) or when the brain begins developing (at 54 days after conception).
• Embryonic stem cells can potentially treat a wide range of diseases as they have the potential to grow indefinitely in a laboratory environment and can differentiate into almost all types of bodily tissue.
• It is unethical not to use established protocols on embryonic stem cell research to further embryonic stem cell research to help relieve human suffering.
• There is legislation on the period when ES cells can be extracted. eg: Current UK legislation does not allow use of embryos that are more than 14 days old. In fact, ES cells are obtained earlier from blastocyst (between 3-8 days after fertilization).
• More than a third of zygotes do not normally implant in the uterus.

  Thus, far more embryos are lost due to chance than are proposed to be used for embryonic stem cell research.
• Surplus embryos created via in vitro fertility treatments are destroyed, or stored long past their viable storage life. These can be used for creating new stem cell lines for research which would otherwise be destroyed
• Since iPSCs can be obtained directly from adult tissues, it does not generate or destroy any human embryos.
• Adult tissue (e.g. skin cells) required to make iPSCs can be easily obtained from donor without risk to the donor
• unlike ES cells extracted from human embryos, iPSCs derived from a patient's own cells, generating patient-specific cells, which will not be rejected by the immune system upon transplantation.

  Hence, no need to use immunosuppressant drugs after transplantation, dont need look for a suitable donor for transplantation, allows the generation of pluripotent stem cell lines from patients with inherited diseases
• Low efficiency: rate at which somatic cells were reprogrammed into iPSCs in was 0.01-0.1%.
• Genetic modification of adult somatic cells to obtain iPSCs may cause cancer by overexpression of proto oncogenes or switching off of tumour suppressor genes.
• addiontional reproductive technology,

  generation of sex cells (sperm and eggs) for treating infertility.
• features:

  1. undifferentiated and unspecialised cells
  2. can undergo extensive proliferation and self-renewal
  3. able to differentiate to produce specialised cells , upon receiving appropriate molecular signals
• symmetrical division: pdc 2 identical daughter stem cells: ensures constant pool of stem cells

  asymmetrical division: pdc 1 identical daughter stem cells: ensures constant pool of stem cells

  pdc 1 progenitor daughter cell: replace a population of specialised cells in a specific tissue that died
• is there a difference between stem & specialised cell?

  no. characteristics arise from difference in gene expression
• progenitor cell: can only differentiate, but not renew
• why can stem cells self-renew?

  stem cells can express telomerase gene, lengthening telomeres of chromosome, preventing chromosome from reaching critical length, preventing apoptosis
• totipotent: can differentiate into all cell types that make up an ENTIRE organism, including extraembryonic tissue
• pluripotent: can differentiate into all cell types that make up an organism, excluding extraembryonic tissue
• multipotent: can develop into only a limited & related range of cell types & tissues in an organism
• embryonic stem cells vs adult stem cells

  1. diff ability: E pluripotent, A multipotent
  2. role in body
  3. sources: E: donated IVF embryos that are unused A: bone marrow
  4. advantage in research & therapy development:

  • E: pluripotency, strong ability to self-renew in lab & divide more rapidly than ASC -> constant supply
  • A: avoid immue rejection / less ethical considerations