Epithelio-mesenchymal interactions in the developing mouse pancreas: Morphogenesis of the adult architecture

Background/Purpose: The mammalian pancreas is thought to develop through a complex interaction between the budding epithelium and the surrounding mese nchyme. The exact nature of this interaction is unclear. Most of what is kn own to date of these interactions comes from a series of organ culture expe riments done in the late 1960s. Nevertheless, these important experiments m ay have been confounded by less-defined culture media and organ dissection techniques, because the results are not reproducible in our hands. The auth ors undertook a study to reexplore these basic epithelio-mesenchymal intera ctions. Methods: Using previously described organ dissection and culture techniques the authors examined the basic interactions between the embryonic pancreat ic epithelium and its mesenchyme with histological and immunohistological t echniques. Results: The authors found that, contrary to previous reports, the earliest pancreatic anlage did not possess the intrinsic signaling necessary to sup port normal growth and differentiation in vitro. Intimate contact between t he epithelium and the mesenchyme may be necessary until E11.5 for normal gr owth and differentiation. The age of the mesenchyme seemed to correlate wit h the degree of acinar differentiation, and proximity of mesenchyme was imp ortant for acinar differentiation. Conclusions: Previous investigations into the basic epitheliomesenchymal in teractions in the developing mammalian pancreas may have had confounding fa ctors. Extrinsic signals seem necessary for complete pancreatic differentia tion, and mesenchymal factors appear important for acinar differentiation. Copyright (C) 1999 by W.B. Saunders Company.