title: Comparison of Neutral Proteases and Collagenase Class I as Essential Enzymes for Human Islet Isolation.
abstract: Efficient islet isolation requires synergistic interaction between collagenase class I (CI) and class II (CII). The CI degradation alters the ratio between CI and CII and is responsible for batch-to-batch variations. This study compares the role of neutral protease (NP) plus clostripain (CP) with CI as essential enzymes for human islet isolation.
  
  
  METHODS
  Human islets were isolated using 4 different enzyme mixtures composed of CII plus either intact (CI-115) or degraded CI (CI-100). Blends were administered either with or without NP/CP. Purified islets were cultured for 3 to 4 days before islet quality assessment.
  
  
  RESULTS
  Whereas using intact CI-115 without NP/CP did not significantly reduce islet yield (3429 ± 631 vs 3087 ± 970 islet equivalent/g, nonsignificant), administration of degraded CI-100 without NP/CP decreased islet yield from 3501 ± 580 to 1312 ± 244 islet equivalent/g (P < 0.01), doubled the amount of undigested tissue from 11.8 ± 1.6 to 24.4 ± 1.2% (P < 0.01) and triplicated the percentage of trapped islets from 7.7 ± 2.8 to 22.5 ± 3.6% (P < 0.05). Islet yield did not vary between supplemented CI-115 and CI-100, but was increased using CI-115 when NP/CP was omitted (P < 0.05). A trend toward higher viability and increased secretory insulin response was noted in both CI-100 and CI-115 when NP/CP was not added.
  
  
  CONCLUSIONS
  This study suggests that NP/CP can compensate reduced CI activity. Future attempts to optimize enzyme blends should consider the possibility to increase the proportion of collagenase CI to reduce the need for potentially harmful NPs.
authors: Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom.; Oxford Centre for Diabetes, Endocrinology and Metabolism, Oxford, United Kingdom.; Department of Immunology, Genetics and Pathology, University of Uppsala, Uppsala, Sweden.
authors: Heide
authors: H
authors: Brandhorst
authors: Serva Electrophoresis GmbH, Uetersen, Germany.
authors: Manfred
authors: M
authors: Kurfürst
authors: Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom.; Oxford Centre for Diabetes, Endocrinology and Metabolism, Oxford, United Kingdom.; Oxford NIHR Biomedical Research Centre, Oxford, United Kingdom.
authors: Paul R
authors: PR
authors: Johnson
authors: Department of Immunology, Genetics and Pathology, University of Uppsala, Uppsala, Sweden.
authors: Olle
authors: O
authors: Korsgren
authors: Nuffield Department of Surgical Sciences, University of Oxford, Oxford, United Kingdom.; Oxford Centre for Diabetes, Endocrinology and Metabolism, Oxford, United Kingdom.; Department of Immunology, Genetics and Pathology, University of Uppsala, Uppsala, Sweden.
authors: Daniel
authors: D
authors: Brandhorst