Stem Cells
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(Created page with '=Stem Cells= *Stem cells have two features: self renewal and differentiation. *Early experiments in which we though HSCs could dediff into other tissue types were actually misiā¦')
(Created page with '=Stem Cells= *Stem cells have two features: self renewal and differentiation. *Early experiments in which we though HSCs could dediff into other tissue types were actually misiā¦')
Current revision as of 17:47, 2 December 2011
[edit] Stem Cells
- Stem cells have two features: self renewal and differentiation.
- Early experiments in which we though HSCs could dediff into other tissue types were actually misinterpretations of HSC fusion with endogenous cells of other types.
- We are sill trying to use HSCs to fix non-heme disease states though, and there is some reality.
- One major limitation to using HSCs is the inability to expand the population ex-vivo.
- Sources of ESCs include "left-overs" from fertility treatment and SCNT.
- The blastocyst is the center of ethical discussions on embryonic stem cell use; how much moral status does a blastocyst have?
- SCNT: remove donor oocyte nucleus, place another nucleus in the oocyte, trick oocyte into feeling fertilized; develops into embryo.
- Therapeutic cloning is SCNT with pt's own donated nucleus into an oocyte (unlikely to be from the donor).
- Reproductive cloning is the same as therapeutic but you implant it in an organism.
- Not allowed in humans anywhere!
- Not allowed in any animals in some states.
- Reasons reproductive cloning isn't allowed in humans:
- Most implants die soon after implantation.
- Many offspring have developmental abnormalities.
- Human cloning could then be performed simply for organ harvest.
- Therapeutic and reproductive cloning are regulated only at the state level.
- Most states have no law at all.
- Indiana does not allow therapeutic cloning or reproductive cloning (in any animal).
- Bush (2001) allowed use of 60 existing embryonic cell lines.
- Obama (2009) allowed production of new embryonic cell lines:
- from well informed, freely consenting fertility-therapy donors
- with private funds
- iPSCs can self renew and can differentiate.
- iPSCs don't require a blastocyst stage and therefore avoid many ethical concerns.
- One study has shown that Sickle Cell Disease could be fixed in a mouse by gene-correcting autologous iPSCs and reimplanting.
- iPSCs are awesome because:
- immunologically match their pt
- can be repaired
- can be repeatedly differentiated into many different types of tissue
- avoid blastocyst stage and therefore ethical issues
- iPSCs aren't perfect because:
- produced via C-myc which is an oncogene and therefore have a risk of oncogenesis
- produced via retroviral insertion of transcription factors and therefore have a risk of insertional mutagenesis
- still need lots of work to figure out how to purposefully differentiate them into specific tissue types
- We are starting to figure out how to induce iPSCs without c-myc.
- We are starting to figure out how to induce iPSCs only as pluripotent as needed:
- to get to the HSC stage, only, instead of going all the way "back" to the fully potent iPSC.
- means lower risk in teratomas in the pt.