AMPLITUDE-DEPENDENT MODULATION OF BRUSH-BORDER ENZYMES AND PROLIFERATION BY CYCLIC STRAIN IN HUMAN INTESTINAL CACO-2 MONOLAYERS

Little is known about the effects of repetitive deformation during per istaltic distension and contraction or repetitive villus shortening on the proliferation and differentiation of the intestinal epithelium. W e sought to characterize the effects of repetitive deformation of a ph ysiologically relevant magnitude and frequency on the proliferation an d differentiation of human intestinal epithelial Caco-2 cells, a commo n cell culture model for intestinal epithelial biology. Human intestin al epithelial Caco-2 cells were cultured on collagen-coated membranes deformed by -20 kPa vacuum at 10 cycles/minute. producing an average 1 0% strain on the adherent cells. Proliferation was assessed by cell co unting and H-3-thymidine incorporation. Alkaline phosphatase and dipep tidyl dipeptidase specific activity were measured in cell lysates, Sin ce cells at the membrane periphery experience higher strain than cells in the center, the topography of brush border enzyme histochemical an d immunohistochemical staining was analyzed for strain-dependence. Cyc lic strain stimulated proliferation compared to static cells. Prolifer ation was highest in the membrane periphery where strain was maximal. Strain also modulated differentiation independently of its mitogenic e ffects, selectively stimulating dipeptidyl dipeptidase while inhibitin g alkaline phosphatase. Strain-associated enzyme changes were also max imal in areas of greatest strain. The PKC inhibitors staurosporine and calphostin C ablated strain mitogenic effects while intracellular PKC activity was increased by strain. The strain-associated brush border enzyme changes were attenuated but not blocked by PKC inhibition. Thus , strain of a physiologically relevant frequency and magnitude promote s proliferation and modulates the differentiation of a well-differenti ated human intestinal epithelial cell fine in an amplitude-dependent f ashion. PKC may be involved in coupling strain to increased proliferat ion. (C) 1996 Wiley-Liss, Inc.