Basal nutrition promotes human intestinal epithelial (Caco-2) proliferation, brush border enzyme activity, and motility
Perdikis, D.A.; Basson, M.D.
Critical Care Medicine 25(1): 159-165
1997
ISSN/ISBN: 0090-3493 PMID: 8989193 Document Number: 476744
This study examined the hypothesis that basally delivered nutrients might be important for intestinal epithelial biology by comparing the brush border enzyme activity, proliferation and motility of human intestinal epithelial (Caco-2) cells cultured on a type I collagen substrate either on cell culture dishes with culture medium above the apical side of the cell monolayer or in culture inserts on 0.45- micro semipermeable membranes with culture medium beneath the monolayers as well as above them. Proliferation was assessed by serial haematocytometric counts over a 13-day period. Doubling times were calculated by logarithmic transformation of cell counts 48 h apart. The specific activity of the brush border enzymes, dipeptidyl dipeptidase and alkaline phosphatase, was assayed by the digestion of synthetic chromogenic substrates in protein-matched aliquots of cell lysates. Sheet migration was quantitated by the expansion of Caco-2 monolayers across collagen. Motility was dissociated from the proliferative component of monolayer expansion by blocking proliferation with mitomycin C. Basal nutrient delivery promoted Caco-2 proliferation, brush border enzyme activity, monolayer expansion and cell motility. Proliferation increased by 694+or-9.9% (n=90, P<0.0001) in cells nourished apically and basally compared with a 314+or-3.3% increase (n=90, P<0.0001) in those cells receiving only apical nutrition. The addition of basal nutrient delivery to the cell culture system augmented alkaline phosphatase and dipeptidyl dipeptidase specific activity by 116+or-5.4 and 256+or-14.0%, respectively (P<0.0001, n=6 for each group). The effects of basal nutrient delivery were maintained after mitomycin blockade of proliferation for alkaline phosphatase (392+or-89.8% of control, n=3, P<0.0005) and dipeptidyl dipeptidase (374+or-79.1% of control, n=3, P<0.005), suggesting that the increased digestive enzyme-specific activity reflected differentiation rather than indirect effects of slowing of proliferation. Epithelial sheet migration increased by 389+or-8.8% and proliferation-blocked cell motility increased by 76.5+or-1.6% (P<0.0005, n=12 for each) compared with apical nutrient delivery only. It was concluded that although apical nutrition may be critical for intestinal epithelial cell biology, nutrient delivery to the basal surface of intestinal epithelial cell membranes may also promote intestinal epithelial differentiation, proliferation and mucosal healing.