Table 1 |.

Comparison of current approaches to producing new β-cells

	Stem cell differentiation	Replication	In vivo reprogramming	Ex vivo reprogramming	Xenografts	Human pancreas
Stage of development	Phase I/II clinical	Proof-of-concept with human islets	Proof-of concept in animal models	Proof-of-concept With human cells	Proof-of-concept with pig cells	Concept developmet in animal models
Advantages	Unlimited supply, Standardized productin	No transplantation necessary	No transplantation necessary	Relatively simple Production process	Unlimitedsupply, lower cost	Unlimited supply
Tumour risk	Moderate (teratoma)	High	Unknown, potentially high	Moderate	Low	Low
Patient specificity	Possible with iPS cells	Yes	Yes	Possible with patient cells	No	Possible with iPScells
Issues	Complex production process	Targeted delivery required	Targeted delivery required	Stability of cell product	Targeted delivery required	Feasibility unknown, ethical concerns