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Title: INSULIN-LIKE PEPTIDES STIMULATE MIDGUT STEM CELL PROLIFERATION OF LEPIDOPTERAN LARVAE IN VITRO

Author
item GOTO, SHINTARO - KOBE, UNIV. JAPAN
item LOEB, MARCIA
item TAKEDA, MAKIO - KOBE, UNIV. OF JAPAN

Submitted to: In Vitro Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2003
Publication Date: 8/15/2003
Citation: Goto, S., Loeb, M.J., Takeda, M. 2003. Insulin-like peptides stimulate midgut stem cell proliferation of lepidopteran larvae in vitro. In Vitro Biology.

Interpretive Summary:

Technical Abstract: The mechanisms that control the growth rate of internal tissues during postembryonic development are poorly understood in insects. The midgut is the largest organ in lepidopteran larvae, and histologically studied well compared to other tissues. It has been known that the cell mass increases during the molting period, but the factors remodeling the midgut were difficult to study until an in vitro system for growing midgut cells was established. Using the in vitro system, some factors that promote midgut differentiation were isolated from the conditioned medium. However no purified peptide factors that promote midgut cell Proliferation have yet been reported. Since an insulin-like immunohistochemical reaction was observed in the molting midgut, it was expected that an insulin-like peptide might promote cell proliferation in the midgut. Bombyxin is an insulin-like peptide in lepidopteran insects. To clarify the function of bombyxin and the other insulin-like peptides in midgut stem cell proliferation, these peptides were added to the culturemedium of midgut stem cells and the number of the cells were counted. Insulin, IGF-1, IGF-2 and bombyxin stimulated proliferation of midgut stem cells in vitro.The most effective was bombyxin; it induced a maximum effect at 10-12M. The highest number of cells was observed 3 days after the addition of bombyxin. A single addition of bombyxin could not sustain the maximum effect thereafter, but a second addition made 3 days after the first addition maintained the effect. The data suggest that the decline of the observed effect was not due to the loss of sensitivity by the cultured cells but that the growth factor initially added to the culture soon became inactivated.