Differentiation of encapsulated human pluripotent stem cells into insulin‐producing cells.

Abstract

Human islet transplantation can provide glycaemic control in diabetic recipients without the need for exogenous insulin. However, there are two major factors limiting its application. Firstly, there is the recipient’s need to adhere to life-long immunosuppression, something that carries serious side effects. Secondly, the limited availability of donor tissue restricts the option to individuals most in need. Differentiating human pluripotent stem cells offers a potentially limitless supply of transplantable material. This tissue would still be rejected by the host’s immune system without the use of immunosuppression. Isolating the tissue from the host’s immune system is a technique which has been trialled to overcome the need for immunosuppression. The varying methods many researchers are approaching this challenge are outlined in Chapter 1 and include alginate microspheres, alginate-nylon threads and silicone membranes. The disadvantages and strategies to overcome these barriers are discussed. Limited islet availability can be overcome by differentiating human pluripotent stem cells into insulin-producing cells. Chapter 3 details the differentiation of human embryonic stem cells differentiated while encapsulated in alginate microspheres. The gene profiles of the cells differentiated while encapsulated were not statistically different from the cells differentiated on a 2D matrix. These cells were differentiated for 9 days, at which point they expressed the key pancreatic marker PDX1. In chapter 4 the encapsulated cells which had been put through the 9 day differentiation protocol were then transplanted into STZ (Streptozotocin) treated NOD SCID mice. The weight, BGL (Blood Glucose Level) and serum c-peptide level were checked regularly for 3 months. At the three month time point, there were detectable levels of human C-peptide in the serum of the mouse. However, there was no correction of hyperglycaemia. Finally, induced pluripotent stem cells from a person with Type 1 diabetes were encapsulated and differentiated. These cells showed the same gene profiles as the encapsulated human embryonic stem cells differentiated over 9 days.