Quantifying the Effects of Different Neutral Proteases on Human Islet Integrity

Area of Science:

• Endocrinology
• Pancreatic Islet Biology
• Protease Biochemistry

Background:

• Efficient isolation of pancreatic islets is crucial for transplantation and research.
• Collagenase, neutral protease (cNP), and thermolysin (TL) are commonly used for islet digestion.
• Clostripain (CP) has recently been identified as a potential contributor to human islet release.

Purpose of the Study:

• To prospectively evaluate the impact of cNP, TL, and CP on human islet integrity.
• To compare the dose-dependent effects of these proteases on islet yield, viability, mitochondrial function, and insulin content.

Main Methods:

• Human islets from 10 organ donors were isolated and precultured.
• Islets were incubated with varying concentrations (1×, 5×, 10×) of cNP, TL, or CP.
• Post-incubation, islet yield, integrity, DNA release, viability, mitochondrial function, and insulin content were assessed.

Main Results:

• cNP and TL at 5× activity significantly reduced islet yield and induced fragmentation.
• Islet viability decreased with 1× cNP, 5× TL, or 10× CP.
• Mitochondrial function was impaired by 1× cNP and 5× TL, but not by CP.
• Intracellular insulin was lost with 1× cNP and TL, but only at 10× CP.

Conclusions:

• cNP and TL exhibit similar toxicity to islet integrity.
• CP demonstrates a higher toxicity threshold compared to cNP and TL.
• CP may serve as a supplementary protease to reduce cNP or TL concentrations, optimizing human islet isolation.