A potent stimulator of small intestinal cell proliferation extracted by simple diffusion from intact irradiated intestine: in vitro studies.

The epithelium lining the small intestine is one of the most rapidly proliferating body tissues yet it rarely develops cancers. The proliferation, migration and differentiation of the stem cell progeny appears to be under very strict control. After 8 Gy gamma irradiation the murine epithelium contains surviving stem cells from which the epithelium rapidly and effectively regenerates, presumably in response to stimulatory signals, and then returns to steady state conditions after overshoots in proliferation. Here we describe the isolation and preliminary characterisation in vitro of a potent stimulatory extract obtained by diffusion from intact murine small intestine, post-irradiation. In addition to in vivo responses the extract stimulates intestinal epithelial lines very effectively, most notably the rat IEC 18 line where it can replace the serum requirement. The extent of the induced increase in proliferation could not be reproduced by any other single growth factor tested. Preliminary evidence suggests the extract contains either a potent stimulatory cocktail of factors or a novel intestinal growth factor(s).