Significance of the peri-insular extracellular matrix for islet isolation from the pancreas of rat, dog, pig, and man

Abstract

The presence and distribution in the peri-insular region of extracellular matrix, and in particular basement membrane, was investigated in a comparative study comprising pancreata of rat, dog, pig, and man. Basement membrane markers, collagen type-IV and laminin, were determined immunohistochemically. Additional information pertaining to the structural relationships between endocrine and exocrine pancreas, in particular cell-to-cell and cell-to-matrix contacts, was obtained by electron microscopy. In pig, very little peri-insular capsule is present, and the structural integration of the porcine islet in the exocrine pancreas almost exclusively depends on cell-to-cell adhesion. In the canine pancreas, the islets are almost completely encapsulated with very little direct exocrine-to-endocrine cell-to-cell contact. In rat and man, the situation is intermediate with a tendency towards predominance of cell-to-matrix adhesion. The intra-insular adhesion mechanisms depend largely on cell-to-cell adhesion in all four species. The ultrastructural results suggest that collagenase preparations employed in islet isolation procedures should be of high purity as to preserve the protease-sensitive intra-islet cell-to-cell adhesion. Under these conditions, however, the endocrine-to-exocrine cell-to-cell contacts will be conserved also, resulting in an exocrine-tissue contamination of the islets of Langerhans. Consequently, additional steps for the effective removal of exocrine tissue and the purification of islets are required.

Distinct Distribution of Laminin and Its Integrin Receptors in the Pancreas

“…Our results show that major ECM proteins are absent extracellularly between islet cells, as are nidogen-1 and fibulin-1 and -2. Similarly, a range of collagen isoforms-fibronectin, vitronectin, and elastin-were not detected between islet cells (van Deijnen et al 1992;Meyer et al 1997). These studies provide molecular evidence to support a previous electron microscopic study (Like et al 1978) that a BM structure is not found around islet cells.…”

Blood vessels of human islets of Langerhans are surrounded by a double basement membrane

“…Some findings have indicated that in the human pancreas, endocrine cells are separated from exocrine cells by reticulin fibres [15] and the endocrine-exocrine interface in different species variably appears to contain collagens I, IV, V and VI, as well as Lm [16][17][18]. Electron microscopy detected [19] a typical BM facing the endocrine cell at the endocrine-exocrine interface as a peri-islet BM, but the same study failed to detect BM inside human islets. Recent studies have provided evidence of the unique cytoarchitecture of human pancreatic islets when compared with that of rodents [20,21].…”

Large scale isolation, growth, and function of porcine neonatal islet cells.

“…Unfortunately, despite many reports on the isolation of adult porcine islets, factors such as age, breed, and quality of organs adversely affect the final yield (18,19), and, once isolated, adult porcine islets are fragile and difficult to maintain in tissue culture (17,20,21). The fragility of these islets significantly decreases yields of islet cells particularly when culture procedures are used to reduce graft immunogenicity or when low temperature storage is used to combine isolates from multiple donors.…”