STEM CELLS Mesenchymal precursor cells http://www.mesoblast.com/ © 2016 Paul Billiet ODWS

Division and differentiation www.coloradospringsivf.com/img/progeny/5.jpg All cells reproduce by dividing Cells produced by mitosis are clones This is how unicellular organisms reproduce asexually Multicellular organisms are a bit different When the cells of an embryo divides, initially they are all the same Later the cells start to differentiate (specialise). www.scienceclarified.com/.../uesc_04_img0230.jpg © 2016 Paul Billiet ODWS

Differentiation and gene expression All the somatic cells (not gametes) of a multicellular organism contain the same genetic information But cells in different tissues perform different functions Cells in different tissues have quite different forms Therefore, some genes are expressed in a cell and not others. © 2016 Paul Billiet ODWS

Hox genes The genes that control development = Hox genes They are surprisingly similar for all animals The sequence in which they express create the differences in development. Hox genes of fruit fly and mouse © 2016 Paul Billiet ODWS

What causes differentiation? Cells differentiate according to their position in an embryo Growth factors are released by zones of cells called organisers The surrounding cells develop along a determined route Transferring cells from one place to another illustrates this. © 2016 Paul Billiet ODWS

Early experiments Displace organiser cells and the embryo will develop an organ in a different place from usual Or if a second organiser is added an additional organ will develop. Frog embryo with a second organiser graft to it © 2016 Paul Billiet ODWS

More complex animals lose this capacity In simple animals (e.g. sponges) the cells retain their capacity to regenerate into whole new sponge = Totipotent More complex animals lose this capacity Cells of the early embryo are capable of turning into several types of cell = Pluripotent Differentiated cells may not be able to do this. Sea Sponge © 2016 Paul Billiet ODWS

Stem cells Cells that can develop into any other cell are called stem cells A few still exist in the body of an adult E.g. bone marrow has blood stem cells E.g. umbilical cords have stem cells. Bone marrow stem cells © 2016 Paul Billiet ODWS

Blood stem cell differentiation © 2016 Paul Billiet ODWS

Making stem cells Stem cells could be used to replace tissues that are damaged or diseased E.g. cardiac muscle will not divide once it has differentiated Stem cells stimulated to grow into cardiac cells could replace the need for heart transplants The problem of tissue typing and tissue rejection still remains Implanted tissue could become cancerous. © 2016 Paul Billiet ODWS

Cloned stem cells If stem cells can be cloned from the cells of a patient they can be used to generated genetically identical tissues = Therapeutic cloning Mammalian cells need to be set back to zero in the cell cycle (Go). © 2016 Paul Billiet ODWS

Somatic cell nuclear transfer SCNT Dolly the sheep Oocytes harvested Nuclei removed Somatic cells from animal to be cloned fused with enucleate oocyte Electric shock sets the cell cycle to Go Nuclear genome cloned but… Mitochondrial genome comes from animal which donated the oocyte. Removing the nucleus from an oocyte © 2016 Paul Billiet ODWS

Problems for SCNT in therapeutic cloning Human oocytes are few and difficult to obtain A lot of oocytes needed to generate successful cell lines (304 oocytes from 14 macaques to produce 2 cell lines) Ethical problem of embryo destruction Early embryo cells are harvested to generate cloned tissues for transplants/grafts. © 2016 Paul Billiet ODWS

The answers? Fuse somatic cell with enucleated oocyte of another species of animal Umbilical cord stem cells Induced pluripotent stem cells (iPS) (Genetically modified somatic cells reprogrammed back to its undifferentiated state) but v expensive Umbilical cord © 2016 Paul Billiet ODWS

Application: Leukaemia Cancer of blood and bone marrow Affects leukocytes (white blood cells) Mutation of gene in the blood stem cells Deregulates cell cycle - cancerous Abnormal leukocytes block development of normal leukocytes. Nature Outlook “When blood goes bad” © 2016 Paul Billiet ODWS

Blood cell differentiation © 2016 Paul Billiet ODWS

Leukaemia: Stem cell treatment Determine patient’s tissue type (Human leukocyte antigen - HLA) Search donor register or siblings for a match Collect bone marrow cells from donor Total body irradiation kills patient’s immune system Patient maintained in a sterile environment Transfuse donor cells to patient Restore immune system. © 2016 Paul Billiet ODWS

Leukaemia: Problems Infections post transfusion Graft v host disease. © 2016 Paul Billiet ODWS

Applications: Stargardt’s disease (SMD) Juvenile macular degeneration © 2016 Paul Billiet ODWS http://www.laramyk.com/resources/education/occular-anatomy/major-ocular-structures/

Stargardt’s disease Inherited recessive autosomal allele Mutated protein in photoreceptor cells Result: Lipid rich deposits in the retinal pigment epithelium. Vision aware © 2016 Paul Billiet ODWS

Stargardt’s disease: Stem cell treatment Retinal pigment epithelia cells engineered Derived from human embryonic stem cells (hESC) 50 000 – 200 000 cells injected below retina Trials giving successful results IVF surplus embryos & Informed consent hESCs from genetically different donor. © 2016 Paul Billiet ODWS

Problems IVF surplus embryos & Informed consent hESCs from genetically different donor Eye is immunologically privileged. © 2016 Paul Billiet ODWS

Printing a kidney TED Talk (16:54min)http://www.ted.com/talks/anthony_atala_printing_a_human_kidney.html © 2016 Paul Billiet ODWS