Insulin Secretion is Preserved in Canine Insulinoma Cells Maintained in Short-Term Culture
Canine insulinoma is a functional endocrine pancreatic tumor characterized by autonomous insulin secretion that is not inhibited by hypoglycemia. The highly functional nature of canine insulinoma suggests that this tumor could be useful model for investigating cellular and molecular aspects of insulin secretion. The study objectives were to develop techniques for isolation and culture of canine insulinoma cells and to assess the capacity for in vitro insulin secretion.
Tissue from three dogs undergoing pancreatic tumor resection was used to establish in vitro cultures of insulinoma cells. For cell isolation, tumor tissue was finely minced with a razor and passed through a steel mesh to further disrupt tissue. Disrupted tissue was collected by centrifugation, re-suspended into RPMI media (10% FBS), and plated in multiwell plastic plates. Cells were maintained in 95% air/5% CO2 at 37C with media changes every 3 days.
All tumors studied had a histological diagnosis of insulinoma. Light microscopy performed immediately after plating revealed the technique yielded a mixture of single cells and small clusters (2-20 cells). Cytospin preparations of cultured cells performed 1 and 10-weeks after isolation stained (+) for insulin. ELISA performed on culture media was (+) for insulin up to 10 weeks after establishment in culture. At 10-weeks, insulinoma cells showed an increase in insulin secretion after stimulation with 20 mM glucose.
In conclusion, canine insulinoma cells were successfully maintained in short term culture. Cultured insulinoma cells were functional as evidenced by cellular insulin content, secretion of insulin into the culture media, and preserved glucose responsiveness.