Supplementation of sericin is effective in maintenance of islet survival and function under serum-free culture

Abstract

Diabetes is a chronic syndrome due to an insufficiency of insulin production or to insulin tolerance of the target tissue. Islet of Langerhans is the only tissue that produces insulin, the hormone reducing blood glucose level. Therefore islet transplantation is an extremely promising treatment for severe diabetes. Practical islet transplantations have been performed worldwide, including in Japan. However, isolated islets must be transplanted within several hours because their functions and viability reduce as time passes and a suitable islet-culture method for clinical treatment has not been established. Islets are usually cultured in FBS- supplemented medium but the use of FBS has several problems such as batch-to-batch variations and infection from several different pathogens. Therefore the development of a serum-free medium for islets culture is eagerly sought. In the present study, we examined the possibility of sericin as a supplement for islet culture. Rat islets were cultured in RPMI mediums containing sericin, FBS, or no supplement, and the concentration of rat insulin in their supernatants were then measured by ELISA. In the absence of a supplement, half the islets felt apart during culture, while 75% of islets cultured with sericin remained morphologically intact in the presence of sericin. Islets cultured with sericin maintained steady insulin production, while those cultured without supplement rapidly ceased insulin production.