A Comparison of Cross Sectional Surface Area Densities Between Adult and Juvenile Porcine Islets of Langerhans*

The object of this study was to evaluate differences in islet diameters, their distribution and both cross sectional surface areas and densities of insulin containing islets between adult and juvenile porcine pancreata using a computerised image analysis system (Improvision®). Five adult (A) (2 - 3 yrs) and 5 juvenile (J) (< 12 mths) Large White pancreata were assessed. Biopsies were taken from 5 different regions (posterior lobe, duodenal lobe, along with the head, body and tail regions of the splenic lobe) of the pancreas and tissue sections stained for insulin. In both A and J pancreata islet numbers increased with decreasing islet diameter, showing a skewed distribution. There was no statistical significance between the cross sectional surface area within A (mean 5.04 × 10³ µm²) or J (mean 5.99 × 10³ µm²) pancreata. Assuming islets are spherical, extrapolation from πr² showed that the mean diameter for A was 80 µm and 87 µm in J. These compared with A 77 µm and 86 µm diameters using conventional microscopic techniques. The percentage islet volume density relative to exocrine tissue, derived from the principle of Delesse (Area density = volume density), did not significantly differ between each of the 5 areas studied, either in A or J. The percentage islet volume densities did show a significant difference between A (mean 1.83%) (P = 0.001) but not between J pancreata (mean 2.13%). In conclusion poor islet yields can be attributed to differences in islet volume density of islets within porcine pancreata. These results also suggest that the posterior and duodenal lobes should be used along with the splenic lobe in order to improve porcine islet yields. Furthermore, the current practise of reporting porcine islet yields and the isolation index relative to 15 µm (IEQs) needs to be redefined, based on the assumption that the average size of an adult porcine islet is 80 µm.

Key words

Islet Transplantation - Swine - Pancreas - Islets of Langerhans