F.A. van Assche

English

HRČAK - Portal of Croatian Scientific and Professional Journals

93IZ STRU^NIH DRU[TAVAFROM PROFESSIONAL SOCIETIESTHE USE OF STEM CELLS*UPORABA MATI^NIH STANICAView of the European Boardand College of Obstetrics and Gynaecology1. Definition of stem cellsStem cells are cells that can replicate and form one ormore differentiated cell types.1.1. Progenitor stem cells; resulting in the differentia-tion of a single cell type (ex. spermatogonial cells result-ing in spermatozoa).1.2. Multipotent stem cells; resulting in several celltypes constituting a specific tissue or organ (ex. skin stemcells, haematopoietic stem cells, neural stem cells).1.3. Pluripotent stem cells; resulting in all differentcell types in vitro. However, they are not able on theirown to form a whole embryo.Cells isolated from primordial germ cells in the foetusare embryonic germ cells. Cells isolated from the innercell mass at a blastocyst-stage of the embryo are embry-onic stem cells.1.4. Totipotent stem cells; having still the ability to giverise to a whole embryo. In humans this ability is pre-served until the 8 cell stage.Characteristics of the different stem cells.Progenitor and multipotent stem cells are presentthroughout life. However they are more abundant in thefoetus than in the adult (see haematopoietic cells in thecord blood). It is thought that pluripotent stem cells arenot present after the embryonic stage of development.However it has recently been found that thyroid cellsfrom fetal or embryonic origin were present in the thy-roid of a women with thyroiditis, years after pregnancy.2. Source of stem cells2.1. Stem cells of adult origin.Progenitor and multipotent stem cells are present inadults.Somatic stem cells can generate for example liver, pan-creas, bone, cartilage, neural system cells.Haematopoietic stem cells are present in the blood,originating from the bone marrow after stimulation.2.2. Stem cells of fetal origin.– Haematopoietic stem cells are present in umbilicalcord blood.– Multipotent and pluripotent stem cells can be obtain-ed from the fetus after termination of pregnancy.2.3. Stem cells of embryonic origin.Pluripotent embryonic stem cells can be obtained froman embryo at the blastocyst stage. The embryo can beproduced by in vitro fertilisation or by transfer of an adultnucleus to an enucleated oocyte (somatic cell nucleartransfer).3. Human embryonic development3.1. At two or three days after fertilisation, an embryoconsists of identical cells which are totipotent. That is tosay that each could give rise to an embryo on its ownproducing for example identical twins or quadruplets.They are totally unspecialised and have the capacity todifferentiate into any of the cells which will constitutethe fetus as well as the placenta and membranes aroundthe fetus.3.2. At four or five days after fertilisation (morulastage), the embryo is still made up of unspecialised em-bryonic cells, but these cells can no longer give rise toan embryo on their own.3.3. At five to seven days after fertilisation (blasto-cyst stage), a hollow appears in the centre of the morula,and the cells constituting the embryo start to be differen-tiated into inner and outer cells:– The outer cells will constitute the tissues around thefetus (trophoblast), including the placenta.– The inner cells (20 to 30 cells) will give rise to thefetus itself as well as to some of the surroundingtissues. If these inner cells (embryoblast) are isolat-ed and grown in the presence of certain chemicalsubstances (growth factors), pluripotent embryonicstem cells can be derived. These embryonic stemcells are pluripotent, not totipotent since they can-——————————————* Uredni{tvo je od Europskog odbora i kole|a za opstetriciju i ginekologiju (EBCOG) primilo nacrt dokumenta »The Use of StemCells« (Uporaba mati~nih stanica), kojeg je sastavila radna grupa u sastavu: prof. F. A. Van Assche, prof. W. Holzgreve, lord N. Pateli prof. S. Mancuso. Dokument }e biti raspravljen u Pragu na 17. Europskom kongresu ginekologije i opstetricije. Dokument je odzna~enja, jer i embrionalne stanice spadaju u mati~ne stanice, s mogu}no{}u genetskog in`injerstva i terapijske uporabe u budu}nosti.O eventualnim promjenama dokumenta }emo izvijestiti u sljede}em broju ~asopisa.Gynaecol Perinatol 2002;11(2):93–9594Gynaecol Perinatol 2002;11(2):93–95 Iz stru~nih dru{tavanot develop into an embryo on their own. If they aretransferred to a uterus, they would neither implantnor develop into an embryo.4. Research on animals4.1. Embryonic stem cells.For the last two decades research on embryonic stemcells has been performed in vitro. Embryonic stem cellsneed differentiation in vitro before they can be used fortherapeutic purpose. Some success has been demonstrat-ed in the treatment of traumatic spine injury and myo-cardial injury.4.2. Recently it has been shown that so called »adult«stem cells have more malleability than previously be-lieved. Mouse neural stem cells can, in specific conditionsof culture, form cells of other organs (blood, muscle,intestine, liver, heart). Moreover marrow stromal cellshave been shown to generate astrocytes and myocytes.5. The therapeutic use of human stem cells5.1. Neural stem cells.Clinical trials in patients with Parkinsons disease havebeen performed. Transplantation of neural cells derivedfrom the human fetus has been used and shows a thera-peutic effect. This procedure is still experimental; fiveto six aborted fetuses are necessary to provide enoughneural tissue to treat one patient with Parkinsons dis-ease. Proliferation in culture of these neural cells is nec-essary to provide a large amount of cells, needed for trans-plantation.5.2. Haematopoietic stem cells.Adult haematopoietic stem cells can be derived frombone marrow of donors, or from the patients themselves(before chemotherapy). They can also be obtained fromthe peripheral blood, after treatment to induce the pas-sage of stem cells from the bone marrow into the bloodcirculation.Haematopoietic stem cells of fetal origin are obtainedfrom the cord blood.These cells are preserved in cord blood banks.They are collected immediately after birth of thenewborn and before the delivery of the placenta,without interfering with the usual procedure of cordclamping.Currently an international network of banks for stemcells from cord blood for allogenic transplantations isdeveloped. Also targeted transplantations are performedwhere cord blood is used for first degree relatives, andeven autologous banking is propagated to be used like aspecial form of »private life« insurance.5.3. Perspectives for the future.Production of specific cell lines for therapeutic trans-plantation is considered as an important step to cure con-genital or acquired lesions in human tissues; often re-ferred to as »regenerative medicine«. Results of cell ther-apy in animals are promising, but as yet not applicablefor clinical use.Embryonic or fetal stem cells are less rejected com-pared to adult stem cells. Tissues derived from allogenichuman stem cells will have the problem of rejection.This can be avoided by the use of autologous stemcells from adult tissue (or in principle autologous cordblood). It is also possible to create an embryo with ge-netic characteristics of the receptor, using somatic cellnuclear transfer (therapeutic cloning).6. Ethical considerations6.1. The philosophical and religious views on the useof embryonic stem cells in therapeutic research have beenwell documented in the Unesco document of the Divi-sion of Human Sciences, Philosophy and the Ethics ofScience and Technology (Bio 7/00/GT – 1/2, April 2001).6.2. There has been an intense debate about the moralstatus of the human embryo, which has not lead to a gen-eral European consensus. There are two major approachesto formulate the value of human life: first, absolute dig-nity, respect and protection to all human life; second,relative dignity, respect and protection to human life,differing and depending on the development, environ-ment and interests.6.3. The human embryo possesses dignity and de-serves respect and protection. This respect and protec-tion are not absolute, but gradual, as accepted by a largemajority, since it is agreed that spare embryos, not re-trieved for reproduction, may be destroyed.6.4. Human embryonic cells have the potential of treat-ing congenital and acquired diseases in the human (re-generative medicine). Research on human embryonicstem cells may be necessary if this treatment in the hu-man is to succeed.6.5. Stem cells isolated from the blastocyst no longerby themselves have the ability to develop into a humanbeing. However these cells should be handled respect-fully like any human tissue.6.6. The moral principles that apply to the use of spareembryos resulting from infertility treatments are differ-ent from those embryos created specially for research orfor therapeutic use by somatic nuclear transfer method-ology (therapeutic cloning).6.7. It is necessary that any research on human em-bryos, embryonic tissues and human stem cells shouldbe approved by Research Ethics Committees.7. E.B.C.O.G. recommendation7.1. The use of adult stem cells should be treated inthe same way as any other tissue (organs and blood) do-nation, based on respect for the integrity of the humanbody and the free and informed consent of the donor.7.2. The use of haematopoietic stem cells from the cordblood after birth of the newborn requires informed con-sent regarding possible uses of cells by the donor (wom-an or couple).95Gynaecol Perinatol 2002;11(2):93–95 Iz stru~nih dru{tava7.3. The use of fetal stem cells requires free and in-formed consent from the woman or couple. The condi-tions of legal abortion should not be changed for thepurpose of obtaining fetal tissues. When termination ofpregnancy is carried out, the timing and method usedmight not be influenced by the need to retrieve fetal tis-sue.7.4. In some European countries the creation of »spareembryos« is permitted. When decided that spare embryoswill be destroyed it is accepted that after thawing furtherin vitro culture is performed, to produce blastocysts toretrieve embryonic stem cells for research.Free and in-formed consent from the woman or couple is requiredwhen these spare embryos are used for obtaining embry-onic stem cells.7.5. In most European countries the creation of em-bryos for research is not permitted; it is assumed thatthis is in major conflict with the priority of human digni-ty. If somatic cell nuclear transfer proves effective for»regenerative medicine«, it may be acceptable in the fu-ture that embryos are created for this purpose, under strictregulations.7.6 Reproductive cloning shows severe ethical prob-lems regarding human dignity. Furthermore given thehigh risk of abnormalities, the scientific objections tohuman cloning are currently overwhelming. Thereforereproductive cloning in the human should be forbidden.7.7. Research on stem cells should include researchon adult stem cells, embryonic, fetal and cord blood stemcells.7.8. The use of stem cells needs strict regulations.Prof. F. A. van AsscheVIJESTINEWS6th WORLD CONGRESS OF PERINATAL MEDICINEOsaka, Japan, September 13–16, 2003Informations: 6th WCPM Technical Secretariat, c/o Japan Convention Services, Inc., 13F., Sumimoto Seimei MidosujiBldg., 4-14-3 Nishitemma, Kita-ku, Osaka 530-0047, Japan.Fax: +816 63112130; E-mail: wcpm@convention.co.jp; URL http://www2.convention.co.jp/wcpm6.

THE USE OF STEM CELLS

Abstract

Similar works

Full text

Available Versions

HRČAK - Portal of Croatian Scientific and Professional Journals

Hrčak - Portal of scientific journals of Croatia