Methods used to study intestinal nutrient transport: past and present

Intestinal tissue engineering: from regenerative medicine to model systems

BACKGROUND

Tissue engineering is a rapidly emerging field that combines the established disciplines of engineering, biology, and medicine with the goal of fabricating viable tissues and organs. Although initially targeted for applications in regenerative medicine, a novel application of this technology has been to generate experimental model systems for studying biological mechanisms and testing the efficacy of potential therapies.

METHODS

Review and analysis of the literature.

RESULTS AND CONCLUSION

We present the limitations of existing models and provide examples of how tissue engineering has allowed for the generation of new models that may overcome these limitations.

Glutamine and KGF each regulate extracellular thiol/disulfide redox and enhance proliferation in Caco-2 cells

Glutamine (Gln) and keratinocyte growth factor (KGF) each stimulate intestinal epithelial cell growth, but regulatory mechanisms are not well understood. We determined whether Gln and KGF alter intra- and extracellular thiol/disulfide redox pools in Caco-2 cells cultured in oxidizing or reducing cell medium and whether such redox variations are a determinant of proliferative responses to these agents. Cells were cultured over a physiological range of oxidizing to reducing extracellular thiol/disulfide redox (Eh) conditions, obtained by varying cysteine (Cys) and cystine (CySS) concentrations in cell medium. Cell proliferation was determined by 5-bromo-2-deoxyuridine (BrdU) incorporation. Gln (10 mmol/l) or KGF (10 microg/l) did not alter BrdU incorporation at reducing Eh (-131 to -150 mV), but significantly increased incorporation at more oxidizing Eh (Gln at 0 to -109 mV; KGF at -46 to -80 mV). Cellular glutathione/glutathione disulfide (GSH/GSSG) Eh was unaffected by Gln, KGF, or variations in extracellular Cys/CySS Eh. Control cells largely maintained extracellular Eh at initial values after 24 h (-36 to -136 mV). However, extracellular Eh shifted toward a narrow physiological range with Gln and KGF treatment (Gln -56 to -88 mV and KGF -76 to -92 mV, respectively; P < 0.05 vs. control). The results indicate that thiol/disulfide redox state in the extracellular milieu is an important determinant of Caco-2 cell proliferation induced by Gln and KGF, that this control is independent of intracellular GSH redox status, and that both Gln and KGF enhance the capability of Caco-2 cells to modulate extremes of extracellular redox.