Experimental Micro Encapsulation of Pancreatic Islets with Air-driven Droplet Generator and Alginate

Koo, Sun Kyung; Kim, Song Cheol; Wee, Yu Mee; Kim, Jin Hee; Kim, Yang Hee; Jung, Eun Jung; Jang, Sung Ho; Choi, Monica Young; Park, Youn Hee; Park, Kwan Tae; Lim, Dong Gyun; Han, Duck Jong

Abstract

PURPOSE: Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of type 1 diabetes mellitus without immunosuppression. This is based on the principle that foreign cells are protected from the host immune system by an artificial membrane. The aim of this study is to establish an ideal condition of microencapsulation by using an air-driven droplet generator and alginate in vitro.
METHODS
Islets were prepared from Sprague Dawley rat and semi SPF-micro pig. Alginate concentrations were changed from 1.5% to 3.0%, and inflow rate of alginate was varied from 10 mL/hr to 40 mL/hr. CO2 flow rate was regulated from 2.0 L/min to 4.0 L/min. Viability was checked by dithizone and FDA/PI staining. Secretory function was tested with glucose challenge and insulin stimulation index was investigated.
RESULTS
The optimal conditions for islet encapsulation were revealed with alginate inflow rate of 10 mL/hr, CO2 flow rate of 2.0 L/min in concentration of 2% alginate. In concentration of 2.5% alginate, alginate inflow rate of 20 mL/hr, CO2 flow rate 3.0 L/min was ideal, and alginate inflow rate of 40 mL/hr, CO2 flow rate of 4.0 L/min showed good conditions of microcapsules in concentration of 3% alginate. Viability of encapsulated islets was higher than 90% in both rat and porcine. In terms of insulin secretion, encapsulated islets secreted insulin in response to glucose in static culture medium. However there was no normal response to low and high glucose challenge with stimulation index of less than 2.0.
CONCLUSION
Microencapsulation of islets in rat and pig was successful with air-driven droplet generator and alginate in vitro. Further studies about biocompatibility and glucose control in vivo should be followed to be a useful tool for treatment of diabetes mellitus patients in clinical setting.