A Multiparametric Assessment of Human Islets Predicts Transplant Outcomes in Diabetic Mice

Abstract

Prior to transplantation into individuals with type 1 diabetes, in vitro assays are used to evaluate the quality, function and survival of isolated human islets. In addition to the assessments of these parameters in islet, they can be evaluated by multiparametric morphological scoring (0-10 points) and grading (A, B, C, D, and F) based on islet characteristics (shape, border, integrity, single cells, and diameter). However, correlation between the multiparametric assessment and transplantation outcome has not been fully elucidated. In this study, 55 human islet isolations were scored using this multiparametric assessment. The results were correlated with outcomes after transplantation into immunodeficient diabetic mice. In addition, the multiparametric assessment was compared with oxygen consumption rate of isolated islets as a potential prediction factor for successful transplantations. All islet batches were assessed and found to score: 9 points (n = 18, Grade A), 8 points (n = 19, Grade B), and 7 points (n = 18, Grade B). Islets that scored 9 (Grade A), scored 8 (Grade B) and scored 7 (Grade B) were transplanted into NOD/SCID mice and reversed diabetes in 81.2%, 59.4%, and 33.3% of animals, respectively (P < 0.0001). Islet scoring and grading correlated well with glycemic control post-transplantation (P < 0.0001) and reversal rate of diabetes (P < 0.05). Notably, islet scoring and grading showed stronger correlation with transplantation outcome compared to oxygen consumption rate. Taken together, a multiparametric assessment of isolated human islets was highly predictive of transplantation outcome in diabetic mice.

Keywords: islet transplantation; morphological grade; human islets; immunodeficient diabetic mouse; morphological score; type 1 diabetes.

Figure 1.

Representative images of isolated human islets displaying typical morphologic features. Images are from the dataset of the current study. Islets were scored for shape (three-dimensional), border (two-dimensional), integrity, single cells, and diameter. Each individual parameter was scored from 0 to 2 point(s). No islets scored 0 in any parameter. Islets were stained with iDTZ solution. Scale bar, 100 μm. See Table 1 for additional details.

Figure 2.

Distribution of islet morphological scores and grades. (A) Distribution of the scores of individual parameters (n = 55 islet batches in each parameter). (B) Distribution of the total scores and grades (n = 55 islet batches).

Figure 3.

Islet morphological scores positively correlate with islet transplantation outcomes. (A) Correlation of islet morphological scores (7–9 points) to AUC_0-28; n = 62 mice transplanted with islets graded 7 points, n = 70 mice transplanted with islets graded 8 points, and n = 70 mice transplanted with islets graded 9 points. (B) Cumulative curves of diabetes reversal derived from blood glucose levels from diabetic animals transplanted with islets from the indicated scored islet groups. ** P < 0.01, **** P < 0.0001. Student’s t-test and Log-Rank test (Prob>ChiSq) were used to determine significance in Fig. 3A, B, respectively.

Figure 4.

Islet morphological grade is effective at predicating islet transplantation outcome compared to OCR. (A) Correlation of islet morphological grade (Grade A vs. Grade B) to AUC_0-28; n = 70 mice transplanted with Grade A and n = 132 mice transplanted in Grade B islets. (B) Correlation of OCR-SI (<1.24 vs. >1.24) to AUC_0-28; n = 36 mice transplanted with islets having an OCR <1.24 and n = 145 mice transplanted with islets having an OCR >1.24. (C) Cumulative curves of diabetes reversal according to the morphological grade. (D) Cumulative curves of diabetes reversal according to the OCR-SI. *** P < 0.001, **** P < 0.0001. Student-t test and Log-Rank test (Prob>ChiSq) were used to calculate significance in Figures 4A, B, and Figures 4C, D, respectively.

Figure 5.

Individual parameters in the islet morphological score positively correlate with transplantation outcome. Post-transplant glycemic control values of mice (AUC_0-28) were plotted according to the individual parameters (shape, border, integrity, single cells, and diameter). Boxplots demonstrate data distribution, interquartile range, and median. The Student’s t-test was used to determine significance. *P < 0.05, ***P < 0.001.