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

Properties of STEM cells Plasticity Self renewal

STEM CELLS 1.Source 2.Cloning 3.Plasticity

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

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

Origin of vertebrate stem cells

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):

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

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 Movies like Boys from Brazil and Jurassic park Variation on this is THERAPEUTIC CLONING (NOT make a new adult). Perhaps a better name to avoid ethical issues is somatic nuclear transfer.

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

ADULT STEM CELLS Bone marrow derived stem cell classic source

Haematopoiesis Stem Cell (HSC)

adult embryo ES cells EG cells Somatic Stem cells

Multiple paths to new cell identities

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

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

STEM CELLS 1.Source 2.Cloning 3.Plasticity

Myogenic Stem Cells Satellite cell Terry Partridge

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

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

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

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

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

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

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

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.

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

Properties of STEM cells Plasticity Self renewal