The influence of type I collagen on the growth and differentiation of the human colonic adenocarcinoma cell line HT-29 in vitro

Characterization of a spontaneously polarizing HT-29 cell line, HT-29/cl.f8

A cloned cell line that spontaneously polarizes in standard glucose-containing media was derived from a single cell of the adenocarcinoma cell line HT-29. The cloned line, designated HT-29/cl.f8, has remained stable over 2 yr in culture, maintained high transepithelial resistance (300 ohm cm(2) or higher), and correctly sorted influenza virus and vesicular stomatitis virus to apical or basolateral domains, respectively. The newly cloned cells also displayed apical microvilli, tight junctions, and desmosomes, the morphological characteristics of mature epithelia. The cloned HT-29/cl.f8 cells function as epithelial enterocytes as shown by the apical expression of intestinal alkaline phosphatase, the expression of vimentin and cytokeratin, and lack of expression of mucin. We propose that the newly cloned HT-29/cl.f8 cells offer a viable alternative for studies of enterocyte function that will readily yield interpretable data not complicated by cell alterations due to the presence of drugs or chemicals that induce differentiation.

Do cell culture conditions influence the carrier-mediated transport of peptides in Caco-2 cell monolayers?

Despite the fact that different laboratories have reported large differences in permeability for actively transported substrates, Caco-2 cell monolayers are widely used as in vitro model to study small intestinal drug transport. Therefore, we investigated the effect of cell culture conditions, such as time in culture, membrane support, seeding density and supplements to the medium, on the morphology, the formation of tight junctions, as well as the expression of two peptide transporters (PepT1, HPT1) and the efflux pump, P-glycoprotein (Pgp), in Caco-2 cell monolayers. Tight junction formation was assessed by transepithelial electrical resistance measurements; multi-cell layer formation by confocal laser scanning microscopy, the expression of transporters by RT-PCR and the permeability of the PepT1 substrate, cephradine. Both morphology and the expression of carrier-mediated transporters, varied strongly as a function of culture conditions. An increase of differentiation, as documented by tight, homogeneous cell monolayer formation displaying a strong expression of all carrier-mediated transporters, was found up to 3 weeks post seeding. One week later, multi-layer structures were observed and the expression of Pgp decreased. Polyester and polyethylene terephthalate membrane supports decreased the paracellular transport rates substantially, while collagen-coating of PC inserts showed no influence on the morphology and even increased carrier-mediated transporter expression. An average seeding density of 6x10(4) cells/cm(2) seemed to be most favorable, since lower seeding densities led to thin monolayers with altered tight junctions and higher seeding densities to the formation of multilayers. In summary, the expression of carrier-mediated transporters was strongly affected by the culture conditions. The full differentiation was reached after 21 days on collagen-coated polycarbonate inserts at an initial seeding density of 6x10(4) cells/cm(2).

Basal nutrition promotes human intestinal epithelial (Caco-2) proliferation, brush border enzyme activity, and motility

OBJECTIVES

Provision of nutrients to the apical membrane of intestinal epithelial cells by the enteral route is critical for normal gut mucosal function and for the sheet migration required for mucosal healing. The present work attempts to determine whether supplemental nutrient delivery to the basal epithelial surface is important for intestinal epithelial biology. Since attempts to regulate intestinal epithelial cell biology by manipulation of parenteral nutrition solutions have met with some success, we hypothesized that basally delivered nutrients might also be important for intestinal epithelial biology.

DESIGN

To test this hypothesis, we compared 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-mu semipermeable membranes with culture medium beneath the monolayers as well as above them. Proliferation was assessed by serial hematocytometric counts over 13-day period. Doubling times were calculated by logarithmic transformation of cell counts 48 hrs 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.

SETTING

Laboratory for gastrointestinal mucosal biology.

SUBJECTS

A well-differentiated subclone of cells derived from the established human Caco-2 colonic epithelial cell line.

MEASUREMENTS AND MAIN RESULTS

Basal nutrient delivery promoted Caco-2 proliferation, brush border enzyme activity, monolayer expansion, and cell motility. Proliferation was actually increased by 694 +/- 9.89% (n = 90, p < .0001) in cells nourished apically and basally compared with a 314 +/- 3.31% increase (n = 90, p < .0001) in those cells receiving only apical nutrition. The addition of basal nutrient delivery to the cell culture system augmented both alkaline phosphatase and dipeptidyl dipeptidase specific activity by 116 +/- 5.4% and 256 +/- 14.0%, respectively (p < .0001, n = 6 for each group). The effects of basal nutrient delivery were maintained after mitomycin blockade of proliferation for both alkaline phosphatase (392 +/- 89.8% of control, n = 3, p < .0005) and dipeptidyl dipeptidase (374 +/- 79.1% of control, n = 3, p < .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 +/- 8.8% and proliferation-blocked cell motility also increased by 76.5 +/- 1.56% (p < .0005, n = 12 for each) compared with apical nutrient delivery only.

CONCLUSIONS

These results suggest 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.

Growth factor regulation of proliferation in primary cultures of small intestinal epithelium

Although the intestinal epithelium is one of the most rapidly renewing tissues, little is known about the major growth factors that control the rate of cell replacement and migration. Recently, a primary culture model has been described for the developing rat small intestinal epithelium, which permits epithelial growth while maintaining interactions with associated stromal cells, thereby possessing several contextual advantages over established cell lines (Evans et al., 1992). We have used this model to begin to determine the factors that may be involved in controlling intestinal epithelial cell proliferation. Under the conditions examined, no single growth factor promoted exclusive proliferation of epithelial cells; stromal cell proliferation was also apparent. The most potent stimulators of epithelial proliferation were insulin and insulin-like growth factor 1 (IGF-1). These factors also appeared to inhibit migration of the epithelial cells. 5-10 ng/ml EGF, 5-20 ng/ml TGF alpha, and 10-20 ng/ml PDGF also slightly increased epithelial cell numbers. Cell proliferation was inhibited by 0.1 ng/ml TGF beta-1. In Dulbecco's modified Eagle's medium (DMEM) containing 0.25 IU/ml insulin, glucose levels of 2-3 g/liter permitted epithelial growth with limited expansion of the stromal cell population. Higher levels of glucose further stimulated the nonepithelial cell types. Transferrin was also a potent stimulator of both cell types.