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

2. Division and differentiation
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).
© 2016 Paul Billiet ODWS

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Blood stem cell differentiation
© 2016 Paul Billiet ODWS

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. Blood cell differentiation
© 2016 Paul Billiet ODWS

17. 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

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

19. Applications: Stargardt’s disease (SMD)
Juvenile macular degeneration
© 2016 Paul Billiet ODWS

20. 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

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

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

23. Printing a kidney
TED Talk (16:54min)
© 2016 Paul Billiet ODWS