GENERATION OF NEOMUCOSA IN-VIVO BY TRANSPLANTATION OF DISSOCIATED RATPOSTNATAL SMALL-INTESTINAL EPITHELIUM

A novel method to study the generation of rat small intestinal mucosa, by transplantation of disaggregated postnatal rat small intestinal ep ithelium is described. Cellular aggregates, comprised of epithelium wi th attached proliferative cells and closely associated stromal tissue, were isolated from postnatal rat small intestine by enzymatic digesti on, then grafted immediately to the subcutaneous plane of adult recipi ents. On graft retrieval after 14 days, 39% of cellular transplants to nude mice, and 84% of cellular transplants to inbred rats had develop ed into small intestine-like structures. These structures were compris ed of a circumferential layer of epithelium surrounding a central muci n filled lumen. This neomucosal layer exhibited well formed crypts and villi, and contained all epithelial stem cell lineages i.e. absorptiv e enterocytes, goblet cells, Paneth's cells and entero-endocrine cells . Proliferative activity within this neomucosa was confined to crypt r egions as in normal postnatal small intestine. Developmental maturatio n within the regenerated neomucosa was demonstrated by organotypic mor phogenesis, i.e. formation of mature crypts and villi, and progressive cytodifferentiation with increased numbers of goblet cells, entero-en docrine cells and Paneth's cells. Altered patterns of brush border enz yme expression further confirmed a temporal progression of development within neomucosal enterocytes. It is concluded that after ''extensive '' mucosal disaggregation, postnatal small intestinal epithelial proge nitor cells retain the capacity for organotypic regeneration of neomuc osa when transplanted to ectopic sites in adult recipients. These smal l aggregates of epithelium and stroma are capable of generating the to pographical signals necessary for the three dimensional regeneration o f this tissue. Furthermore, the multipotent generative potential of th e stem cells within these cellular aggregates is maintained with produ ction of all progeny.