Good question.
Some people seem [ahem] "overly eager" to involve human embryos in their experiments.
Great, once again, the embryonic stem cell researchers have replicated work already done on adult stem cells. In this case, we know that there are bone marrow cells that migrate to and repair damaged retinas and are exploring the chemoattractants that enable this migration and repair.The work is early, and like Lanza's, still in animal models, but it's ahead of the embryonic work.
http://www.iovs.org/cgi/content/abstract/47/4/1646
Do a pubmed search
http://www.ncbi.nlm.nih.gov/
on "retina adult stem cells."
http://www.ncbi.nlm.nih.gov/entrez/utils/fref.fcgi?itool=Abstract-def&PrId=3051&uid=16565405&db=pubmed&url=http://www.iovs.org/cgi/pmidlookup?view=long&pmid=16565405
CONCLUSIONS: Damaged RPE secretes cytokines that have been shown to serve as chemoattractants for BM-derived stem cells (BMSCs). Retina-committed stem cells appear to reside in the BM and can be mobilized into the PB by G-CSF and FL. These stem cells may have the potential to serve as an endogenous source for tissue regeneration after RPE damage.
and
http://www.ncbi.nlm.nih.gov/entrez/utils/fref.fcgi?itool=Abstract-def&PrId=3048&uid=16563378&db=pubmed&url=http://linkinghub.elsevier.com/retrieve/pii/S0014-4835(06)00075-3
This study demonstrates that proliferation of a quiescent cell population with retinal stem/progenitor cell characteristics can be reactivated in vivo upon GF injections and suggests that, in adult mammals, the CB is a non-permissive environment for cell migration and neurogenesis.
There's much more on the retinal stem cells, just from this year.
Most retinal pigmentation happens postnatally, so the eye is one of the best chances for learning to recruit and activate appropriate stem cells. (We're already investigating transplanting corneas from non-embryonic stem cells.)
Gotta go slow, though.
One of the fantastic experiences I had in med school was to watch a patient's eyes "Snow" as the white blood cells in them - in reaction to a brain tumor - fell like snow when he sat up.
Here's some stem cell info you wanted...