Stem cells and regenerative medicine
Stem cells can in principle develop into any specialised cell of the body, so they promise to replace tissue a patient has lost, and more effective bone marrow transplants are linked to blood-forming stem cells taking hold in the recipient. Rejection, vascularization and the risk of tumours stood between the laboratory work and treatment, which as of 2012 was mostly at the preclinical stage. Taking cells from embryos raises ethical questions on which secular and religious traditions take different positions, and the technology has its place in the future of healthcare beside personalised cancer medicine and vaccination.
What stem cells are
Stem cells are pluripotent cells, able to function in more than one way, that under the right conditions develop into any specialised cell in the human body. A fertilised egg divides into eight identical embryonic stem cells, each of which can become a different specialised cell, such as a red or white blood cell, because stem cells contain the genes needed to become any cell. Those genes can be switched on or off by factors in the surrounding environment, and the specialised cells then multiply to form a tissue or organ. The umbilical cord holds huge concentrations of stem cells because the growing embryo needs to develop tissues and organs.
In theory, a patient with a dysfunctional liver need not wait for a donor, because an injection of stem cells into the failing liver would make new specialised liver cells. But many factors can be fatal, such as rejection and incorrect vascularization, the production of new blood vessels from other blood vessels to feed a new tissue.
Haematopoietic stem cells and bone marrow transplantation
Patients who receive bone marrow transplants often rely on donors who are genetically different but not incompatible. If the donor bone marrow is incompatible with the patient's body, cells within the marrow recognise the body as non-native and begin to attack it. The ideal is for signals inside the body to activate the haematopoietic stem cells so that they begin producing new, healthy blood cells in sufficient quantities. The process by which haematopoietic stem cells resume differentiation after transplantation is called engraftment. Engraftment is linked to more effective bone marrow transplants. Facilitating cells promote engraftment. In research reported in 2009, facilitating cells enhanced the clonogenicity of haematopoietic stem cells, increased multipotent progenitors and prevented haematopoietic stem cell death, and these effects required direct cell-to-cell contact between the two kinds of cell. The results suggest that facilitating cells promote the proliferation of haematopoietic stem cells and progenitor cells, both precursors of many of the blood cell types in the human body. The findings may offer new hope for patients who need bone marrow transplants by enhancing engraftment.
Making muscle cells from stem cells
Early experiments in 2005 that looked at patients with a muscle disorder made muscle cells from stem cells collected from a donor's umbilical cord. The nucleus of the donor's stem cell was replaced with the patient's nucleus, which turned the stem cell into a mesenchymal precursor, an intermediate stem cell that can be made into a muscle, fat, cartilage or bone cell. Tissue-specific stimulation then produced a muscle cell. The cells were co-cultured with mouse feeder cells, which then had to be removed, because a human recipient would not recognise the mouse cells and would reject them. A fluorescent tag confirmed that muscle cells had been made, because it connected only with the muscle cell's unique surface antigens. Each surface antigen has a different shape, like a jigsaw piece that needs the matching shape to fit into it. After washing, only the muscle cells kept their tags, and they could be seen under a special microscope. Fluorescent tagging also checked that every stem cell had been converted to a mesenchymal precursor, because unconverted cells could proliferate and form a tumour, and if injected into a patient they could become cancerous. The experiments made muscle cells for use in humans, but more work was needed to make the cells safe by stopping rejection, and a way was still needed to make the new cells part of the patient's main tissue.
Preventing rejection and achieving vascularization
As of 2012, biomaterials science was used in stem cell technology to minimise rejection and to make the new cells vascularize. Angiogenesis is the process that starts vascularization by producing the first blood vessels, which helps make the scaffolding needed to keep the cells working as one with the body. Materials science can also help stop rejection of newly implanted cells by encasing them in a synthetic semi-permeable membrane. The cells can secrete their products through the membrane, and the membrane keeps the body's immune cells from attacking them.
Induced pluripotent stem cells
In 2006 work in a mouse found that normal specialised cells could be made into cells almost identical to stem cells, called induced pluripotent stem cells. They are created by a virus that gives the specialised cells almost the same characteristics as a stem cell, but the virus can also cause a tumour, which can lead to cancer. As of 2012, induced pluripotent stem cells were at the preclinical stage, tested on animals, and slowly progressing to clinical testing in humans.
Progress towards treatment
As of 2012, stem cell research was mostly at the preclinical stage, with bone, blood vessel and ligament engineering. No treatment had yet cured a patient without dangerous side effects, but progress and discoveries continued.
In 2010 over one million litres of blood were collected from donors in the UK for transfusion, and with every needle costing £1.50 on top of paying the staff who take the blood, the cost ran to millions. In 2011, however, scientists in Edinburgh grew red blood cells from stem cells in vitro on a small scale. If this can be done on a larger scale, blood could be made to order.
Scientists in 2012 predicted that stem cells could influence the treatment of conditions such as Parkinson's disease, Alzheimer's disease, diabetes, heart disease, stroke, cancer and burns.
Ethical positions
Stem cell technology raises many ethical issues. Non-religious views hold that an embryo is a living organism and therefore entitled to some protection, so the cells taken from it are entitled to their own protection and cannot be taken from that embryo for someone else to use. Strict rules and regulations govern cloning a human being using stem cells, because any resulting cloned person may become confused and distressed by the method of their creation.
Some religious perspectives regard taking cells from another being as theft. Many Jewish followers believe that the world is incomplete and needs human interference to work, and that one of the commandments is to heal in any way possible, so they consider using stem cells right. In the 1960s many Catholics strongly believed that taking and transplanting organs is a mutilation of the human body that goes against the belief "first do no harm", but by 2012 they regarded giving up an organ for another person as charity and goodwill. This may mean that in future they may agree with the use of embryonic stem cells, but as of 2012 they were undecided.
Islamic law holds that the embryo is not a person, so extracting embryonic stem cells does not violate any rule of the Qur'an, but only the couple who created the embryo have the right to use its cells. Embryos can be cloned for therapeutic uses, and the Islamic Institute allows embryos to be taken for research, so stem cells can be taken from an embryo and used for research but cannot be transplanted into other patients.
Stem cells beside personalised cancer medicine and vaccines
Stem cell technology holds a key, although arguably not an exclusive, position in the future of healthcare, alongside personalised cancer medicine and vaccine development. Personalised cancer medicine raises fewer ethical issues than stem cells, but as of 2012 it was more expensive than stem cells and could be afforded only in modernised countries. As of 2012 it was at the same level of development as stem cell technology. Vaccines are much cheaper than both, and as of 2012 the new vaccines against malaria and typhoid were further developed than either.
Stem cells, personalised cancer medicine and vaccines can together tackle three of the major causes of morbidity and mortality in the world. The three serve different purposes. Vaccination stops a patient having a disease in the first place, a patient who did develop cancer would need personalised cancer medicine, and a patient who survived it but lacked particular specialised cells, as after losing a limb in a car accident, would need stem cell technology. Because of these different purposes, all three are held to deserve a place in the future of healthcare.