Stem cell: a cell capable of 1) tissue plasticity - make different cell types 2) infinite self renewal through asymmetric division

Transcription

1 Stem cell: a cell capable of 1) tissue plasticity - make different cell types 2) infinite self renewal through asymmetric division stem cell stem cell skin muscle nerve

2 Properties of STEM cells Plasticity Self renewal

3 STEM CELLS 1. Source 2. Cloning 3. Plasticity

4 CLASSIC EXAMPLES of STEM CELLS Embryonic stem cells (ESC) Bone marrow derived stem cells

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16 Blastocyst ICM = embryonic stem cells ICM Fluid-filled cavity termed blastocoele Two regions identifiable - outer trophoblast - inner cell mass (ICM) Blastocyst implants in uterine wall Trophoblast

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19 Origin of vertebrate stem cells

20 USES of EMBRYONIC STEM CELLS 1. Source of different types of human cells for Transplantation: for Cell Therapy or Tissue Engineering (organs). Merit and ethics are controversial 2. Cloning: 3. Somatic nuclear transfer (therapeutic cloning):

21 USES of EMBRYONIC STEM CELLS 1. Source of different types of human cells for transplantation: for Cell Therapy or Tissue Engineering. Merit and ethics are controversial 2. Cloning: to make genetically identical new individuals Achieved for animals unlikely for humans. 3. Somatic nuclear transfer (therapeutic cloning): to generate autologous cells for transplantation Avoids problems of immune rejection of non-self

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23 CLONING 1962 John Gurdon in the UK took (diploid) nucleus from tissue of adult frog and implanted this into an unfertilised egg that had the nucleus removed. The special influence of the maternal cytoplasm caused the differentiated adult nucleus to give rise to a complete new frog FIRST EXAMPLE OF ADULT CLONING. Shows mature nucleus has capacity to revert to equivalent ESC Over 30 years later Dolly the sheep was cloned in Scotland. Then cattle, pigs, cats pets humans?? ISSUES Ethics (especially for humans) Genes vs environment Status/quality of aged DNA Role of maternal cytoplasmic factors and mtdna f

24 USES of EMBRYONIC STEM CELLS 1. Source of different types of human cells for transplantation: for Cell Therapy or Tissue Engineering. Merit and ethics are controversial 2. Cloning: to make genetically identical new individuals Achieved for animals unlikely for humans. 3. Somatic nuclear transfer (therapeutic cloning): to generate autologous cells for transplantation Avoids problems of immune rejection of non-self

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26 ADULT STEM CELLS Bone marrow derived stem cell classic source

27 Stem Cell (HSC) Haematopoiesis

28 ES cells embryo EG cells Somatic Stem cells adult

29 Multiple paths to new cell identities

30 Fluorescent Activated Cell Sorting (FACS) to isolate stem cells based on many cell surface markers Sca1, CD34 etc

31 Stem cells can be derived from tissues throughout development ES Cells Blastocyst ES cells Embryo/Fetal Germ cells Fetal tissues Umbilical Cord Umbilical cord blood (UCB) Supporting tissues (MSC) UBC Post-Natal Tissues Bone marrow (HSC) Blood vessels (ESC) Interstitial connective tissue (MSC) Other tissues

32 STEM CELLS 1. Source 2. Cloning 3.Plasticity

33 Myogenic Stem Cells Satellite cell Terry Partridge

34 Sources of myoblasts within skeletal muscle 2 multipotential/stem cell 3 myonucleus 1 satellite cell myofibre (only part is shown) myoblasts myotubes

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36 Plasticity Resident C/T cells skeletal cardiac pluripotent STEM cells (multi) progenitor cells Vascular endothelial smooth muscle ( ) pericytes? Myofibroblasts ( ) Ectopic cells (chickens) Thymus (myoid cells) Neural Dermis (multi) ( ) Circulating bone-marrow *(multi) *

37 Healthy donor bone-marrow derived stem cells to repopulate diseased host tissues 3. Correction or replacement of DONOR bone marrow stem cells 2. Separation of HOST specific stem cell type Inject healthy donor stem cells derived from another person. These circulating donor stem cells may repopulate any damaged host tissue e.g heart Issues of immune rejection of foreign. Issues of immune rejection of foreign cells can be reduced by using closely matched donor and host cells.

38 Possibilities to explain presence of bone-marrow derived (donor) nucleus (cell) within a (host) cell or tissue. Illustrated for muscle Bone-marrow stem cell 1 2 Conversion A Conversion B (1) Muscle precursor cell with limited proliferation (2) Ideal scenario = Muscle Stem cell with capacity to form many (cardio)myoblasts Asymmetric Cell division

39 Bone-marrow stem cell 1 Conversion A (1) Muscle precursor cell with limited proliferation 2 X Conversion B (2) Muscle Stem cell Asymetric Cell division capacity to form many (cardio)myoblasts 3 Fusion C (3) Fusion of 2 cells + Stem cell Hybrid stem-muscle cell with 2 or more nuclei The stem cell has NOT become a muscle cell

40 Autograft of genetically corrected stem cells: delivered through the circulation 3. Correction or replacement of defective gene in host stem cell 2. Separation of specific type of host stem cell 4. Infusion of host s corrected stem cells to replace or supplement defective host cells 1. Remove patient s bone-marrow Use of own cells avoids immune problems and rejection

41 Two studies show that few of the bone-marrow derived nuclei located within muscle cells actually express muscle-specific genes: indicating fusion without lineage conversion Beth McNally (normal male) bone marrow (b/m) reconstitution of female sarcoglycan (SG) deficient host mice: The rare male b/m-derived nuclei within some myofibres and heart muscle cells, showed NO expression of SG Lapidos KA et al (2004) Anton Wernig male/gfp b/m reconstitution of female mdx (dystrophin deficient) mice: ~80% of male b/m myonuclei showed NO expression of skeletal muscle specific genes Wernig G et al (2005) 3 labels: Y-probe, GFP, dystrophin

42 1 Donor nucleus (Y-FISH) without dystrophin expression WERNIG G et al (2005) 1, 2: SERIAL SECTIONS

43 Current interest in blood vessel derived circulating STEM CELLS: mesangioblasts. Sampaolesi M. Cossu J (2006). Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs. Nature Nov 15. Major problems in data interpretation due to lack of fundamental controls Dogs injected with immunosuppressants alone (without stem cells) were not included. Yet. Cyclosporine alone reduces severity of muscular dystrophy Precise source of stem cells? Poor correlation between increased dystrophin immunostaining (derived from the circulating stem cells) and improved muscle function. Potential issues with digital imaging and image enhancement Confounded by high biological variation Causes major confusion and distress for families of boys with DMD who are seeking a cure/treatment Davies K, Grounds MD (2006) Treating muscular dystrophy with stem cells? Cell. Dec 29. Grounds MD, Davies K (2007) The allure of stem cell therapy for muscular dystrophy. Neuromuscular Disorders March.

44 KEY issues for research INDUCERS to recruit/convert stem cells into specific lineages: critical effects of environment (Plasticity) EXPANSION of cell numbers (proliferation and stem cell renewal) Stem cell isolation/identification

45 Properties of STEM cells Plasticity Self renewal