Stem cells

what is regenerative medicine?

• the branch of medicine concerned with replacing, engineering or regenerating human cells, tissues or organs to achieve normal function.

where do embryonic stem cells for research come from?

• pluripotent stem cells for research and medicine can be isolated from so called ‘spare-embryos’. these are produced in fertility clinics that carry out in vitro fertilisation, where the ovum is fertilised outside the body.

• women undergoing this treatment are given drugs to make them super ovulate, producing more eggs than are needed for infertility treatment

• many of the embryos end up being placed in women’s wombs in the hope of enabling infertile couples to have children but any additional embryos could be a source of embryonic stem cells

what are the use of using stem cells in this way?

• even if scientists manage to get the stem cells to develop into the right sort of tissue, the tissue might end up being rejected by the immune system of the person given the transplant

explain the steps of theraputic cloning?

• the patient needing a transplant would have one of their diploid cells removed - this could simply be a cell from the base of a hair or any other suitable tissue

• this cell, or its nucleus, would then be fused with an ovum from which the haploid nucleus has been known as somatic cell nuclear transfer ( a somatic cell is any diploid body cell)

• the cell could then be stimulated to divide by mitosis in the same way as the cell that gave this to Dolly the cloned sheep. If all went to plan, after about 5 fays a blastocyst would develop

• stem cells could then be isolated from this and encouraged to develop into tissues

• this procedure results in cell lines and perhaps eventually organs for transplantation which are genetically identical to the patient from whom the original diploid cell was taken.

How can adult stem cells be used? Pros and cons?

• adult stem cells have been used for a long time in bone marrow transplants for treatment of leukaemia and related cancers.

• the adult stem cells move into the patient’s bone marrow and produce healthy body cells.

• researchers report success in trials for stem cell treatments being developed for a range of degenerative conditions using patients own stem cells.

  • includes injection of stem cells into stroke patients’ brains to replace damaged neurons and the injection of stem cells into the joints of patients with arthritis to repair damaged cartilage

• its also been used to produce for transplantation. to treat patients with burns, the patients skin stem cells from an unburned area have been cultured.

  • the cells multiply forming a sheet of cells that cover the bottom of the culture flask.

  • these cells can be transplanted to the burned area of the patients giving a skin surface,

  • although because the adult stem cells cant differentiate, the layer of skin cells don’t contain structures such as sweat glands

cons:

• the isolation and culturing of stem cells is difficult and costly, so the culturing of stem cells lines for use would be a more practical option

• these stem cells are likely to be less valuable for research and for the development of new treatments than pluripotent stem cells which can only be derived from human embryos.

pros:

• if whole organs are one day grown from stem cells ( very long way off) it has been estimated that perhaps only 20 stem cell lines would be needed to provide transplants

What are iPSCs?

• induced pluripotent stem cells. Takahashi and Yamanaka ( Japanese researchers) and other research groups have since produced human iPSCs that resemble the human embryonic stem cells. I t would overcome the problems of cell rejection and address ethical concerns with the use of embryonic stem cells.

• iPSCs has shown to be effective for a range of diseases including sickle cell anaemia, Parkinson’s disease, haemophilia and ischaemic heart disease

What are the roles of the HFEA?

• stands for the Human Fertilisation and Embryology Authority

• regulates research on human embryos

• Until 2001, UK law only allowed the use of human embryos where the HFEA considered their use to be necessary or desirable:

  • to promote advances in the treatment of infertility

  • to increase knowledge about the causes of congenital disease

  • to increase knowledge about the causes of miscarriage

  • to develop more effective methods of contraception

  • to develop methods for detecting gene or chromosome abnormalities in embryos before implantation

a stem cell is a cell that can divide ( by mitosis) an unlimited number of times

• each new cell ( produced when a stem cell divides) has the potential to remain a stem cell or to develop into a specialised cells such as a blood cell or a muscle cell ( by a process known as differentiation)

• this ability of stem cells to differentiate into more specialised cell types is known as potency

two main types of potency

• totipotency - totipotent stem cells are stem cells that can differentiate into any cell type found in an embryo, as well as extra - embryonic cells ( the cells that make up the placenta and umbilical cord)

  • the zygote formed when a sperm cell fertilises an egg cell is totipotent, as are the embryonic cells up to the 16 - cell stage of human embryo development

• pluripotency - pluripotent stem cells are embryonic stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into cells forming the placenta and umbilical cord

stem cells are also found in some adult tissues but they are much less potent than embryonic stem cells (i.e. they can only specialise into certain types of cells)

• for example, intestinal stem cells specialise into intestinal epithelial cells to replace those that are constantly being lost

this form of potency is known as multipotency - multipotent stem cells are adult stem cells that have lost some of the potency associated with embryonic stem cells and are no longer pluripotent

plants also contain stem cell in areas of growth, such as their shoots and roots