Use of fetal intestinal isografts from normal and transgenic mice to study the programming of positional information along the duodenal-to-colonic axis.

The four principal cellular constituents of the mouse intestinal epithelium are all derived from a multipotent stem cell functionally anchored near the base of its crypts. Differentiation of enterocytes, enteroendocrine, and goblet cells occurs during an orderly upward migration from monoclonal crypts supplied by a single active stem cell to adjacent polyclonal small intestinal villi or to their colonic homologs, the surface epithelial cuffs. Paneth cells differentiate as they descend to the base of crypts. This epithelium undergoes rapid and perpetual renewal yet is able to maintain cephalocaudal (duodenal-to-colonic) differences in the differentiation programs of its four cell types from the time of its initial cytodifferentiation in late fetal life (embryonic (E) days 16-17). Rat liver fatty acid-binding protein/human growth hormone transgenes (Fabpl/hGH) have been used as novel phenotypic markers to describe the biological properties of gut stem cells and the differentiation programs of their enterocytic and enteroendocrine lineages. To determine whether the multipotent stem cell is able to retain a "positional" address in the absence of luminal signals, we prepared isografts from the proximal small intestine or distal small intestine and colon of E15-E16 Fabpl/hGH transgenic mice and their normal littermates and implanted them into the subcutaneous tissues of young, adult male CBY/B6 nude mice. Immunocytochemical and histochemical studies indicate that appropriate position-specific differences in the differentiation programs of each of the four principal cell lineages are present along the cephalocaudal and crypt-to-villus (or crypt-to-epithelial cuff) axes of isografts harvested 4-6 weeks after implantation. This suggests that the gut stem cell can be characterized not only by its multipotency and enormous capacity for self-renewal but also by its ability to be programmed (? imprinted) with positional information. Transgene expression is reduced in a number of enteroendocrine subpopulations in small intestinal and colonic isografts compared to the intact gut. Moreover, the decision to express the Fabpl/hGH transgene appears to be coordinated between adjacent crypts as evidenced by (i) the presence of multicrypt patches of wholly reporter (hGH)-positive or reporter-negative cells in the intact colon and in colonic isografts and (ii) by the presence of coherent bands of reporter-positive or -negative cells that emanate from adjacent monophenotypic crypts and extend to the apical extrusion zone of distal small intestinal villi.(ABSTRACT TRUNCATED AT 400 WORDS)