LONG-TERM FUNCTION OF PORCINE ISLETS AND SINGLE CELLS EMBEDDED IN BARIUM-ALGINATE MATRIX

The influence of alginate-embedding on the maintenance of functioning and morphological integrity in long-term culture of isolated porcine i slets and islet cells was studied. Free-floating islets and islet cell s served for control. Function was tested after the 1st, 2nd and 4th w eek. Basal and glucose-stimulated insulin secretion of embedded islets decreased slightly, but significantly after the first week (from 4.39 +/-0.64 to 2.87+/-0.47 at normal and from 11.96+/-1.44 to 4.76+/-0.78 muU pro 24h pro islet at elevated glucose concentration, p < 0.05 and < 0.01, resp.) and remained unchanged thereafter. Glucose-stimulation resulted in significant increases in insulin secretion at all three te stings (p < 0.001, < 0.01 and < 0.01). Single cells in alginate matrix had even more stable insulin secretion throughout the whole cultivati on with significant increases to glucose challenge (p < 0.01, < 0.01 a nd < 0.05). In contrast, insulin secretion of free-floating islet cell s decreased from 5.70+/-1.19 to 2.04+/-0.64 and to 1.05+/-0.33 at basa l conditions (p < 0.01 and < 0.05) and from 11.39+/-1.87 to 2.76+/-0.7 6 and to 2.15+/-0.71 muU pro 24 h pro islet under stimulation (p < 0.0 1 and not sign.). In addition, the secretory response to glucose chall enge was significant only at the first testing (p < 0.05). Non-embedde d islets could be tested only at the first week since after this time they dissociated to single cells. Embedded islets and single cells sho wed intact morphology after four weeks with trypan blue (TPB) positivi ty of less than 5 %. The proportion of TBP positive free islet cells w as < 5 % at start but increased to 30% by the end of the culture perio d. Accordingly, alginate matrix proved to be a suitable environment fo r isolated porcine islets and single cells to maintain their function and morphological integrity.