Scientists at the University of Michigan Medical School have found neural crest stem cells - primitive cells that generate the peripheral nervous system - in the gut of adult laboratory rats. The U-M discovery upsets the widely held belief that neural crest stem cells disappear in animals before birth, once the peripheral nervous system develops.

'We do not know what these neural crest stem cells are doing in the gut or whether they persist into adult life in humans, as they do in rats,' says Sean J. Morrison, Ph.D., a Howard Hughes Medical Institute assistant investigator and a U-M Medical School assistant professor of internal medicine and of cell and developmental biology. 'The importance of the study is that it provides the first evidence that stem cells persist in the adult peripheral nervous system. Our results will lead to additional research, which could lead to new ways of using stem cells to promote peripheral nervous system repair after injury or disease.'

To demonstrate that they were true stem cells with the ability to self-renew and form new peripheral nervous system cells, individual neural crest stem cells taken from rat gut at Day 14 of embryonic development were cultured and single cells from rats that were 15-to-110 days old were used. Whether from embryonic or adult rat gut, individual neural crest stem cells gave rise to thousands of neurons, glia and smooth muscle cells. Even though activity declined with age, stem cells could still be isolated from the oldest rat in the study, which was 110 days old.

One of the most intriguing findings of the U-M study was the discovery that neural crest stem cells have the power to control their own developmental destiny. Neural crest stem cells from rats were transplanted into developing peripheral nerves in chick embryos. Stem cells from rats at identical stages of embryonic development (Day 14) were used, but some of the stem cells were isolated from embryonic rat gut and others from the sciatic nerve. Sciatic nerve neural crest stem cells developed into glial cells, while stem cells from the gut became neurons likely differing in their responsiveness to environmental signals that stimulate neural development.

pobo@umich.edu

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