A Coculture Model of Intrahepatic Islet Transplantation: Activation of Kupffer Cells by Islets and Acinar Tissue

Abstract

Clinical and experimental studies of intrahepatic islet transplantation have allowed histological and systemic observations to be made, but the location of the transplanted islets makes it difficult to assess direct effects on the cells of the liver. An in vitro coculture model of Kupffer cells with islets or pancreatic acinar tissue is described, using porcine tissue and measuring the secretion of thromboxane B, prostaglandin E, 6-keto-prostaglandin F, and prostaglandin F as an indicator of Kupffer cell stimulation. The results have demonstrated activation of Kupffer cells in the presence of acinar or islet tissue, both when the cells were in direct contact and when separated by a membrane. This indicated that the stimulation was due to a soluble factor or factors, and was confirmed by the culture of Kupffer cells with acinar conditioned medium. The degree of stimulation was much greater with acinar tissue than with islets. In subsequent experiments, aprotinin, an enzyme activation inhibitor, was added to the cocultures in an attempt to reduce Kupffer cell activation. This had no effect, possibly due to the fact that the endogenous pancreatic enzymes may already be activated during digestion of the pancreas. Aprotinin alone caused an increase in secretion of eicosanoids from Kupffer cells. The high response to acinar tissue is of particular relevance to islet autotransplantation in which unpurified pancreatic digest is often transplanted. The clinical effectiveness of aprotinin in the light of these results is discussed. In conclusion, although unable to mimic the complex situation following intrahepatic islet transplantation, the coculture model described here allows the opportunity to assess the events relating to specific cell types, and will provide the scope to undertake more detailed studies on the mechanisms involved. The same model could be applied to the coculture of pancreatic tissue with hepatocytes to determine any effects on the normal function of hepatocytes.

Composite Islet-Kidneys From Single Baboon Donors Cure Diabetes Across Fully Allogenic Barriers

“…Because the liver is far more vascular than the renal capsule, in the allogeneic setting nonvascularized tissues are more likely to survive, at least temporarily, in the liver versus the renal capsule. However, unlike the space beneath the renal capsule, the liver contains large numbers of Kupffer cells capable of phagocytosing allogeneic islets (23,24). Thus, in the allogeneic setting, non-vascularized pancreatic islets are lost due to (i) anoxia when transplanted under the renal capsule, or (ii) phagocytosis in the liver, that are both enhanced by the allogeneic cellular responses.…”

Evidence of Functional Impairment of Syngeneically Transplanted Mouse Pancreatic Islets Retrieved from the Liver

“…An allogeneic setting might provide further site-specific challenges for transplanted islets. Thus, islet activation of resident liver macrophages with production of cytokines and free radicals, e.g., nitric oxide is known to be toxic to islet ␤-cells, may contribute to islet cell death and dysfunction at this implantation site (35)(36)(37)(38)(39).…”

Inflammation-mediated dysfunction and apoptosis in pancreatic islet transplantation: implications for intrahepatic grafts

“…However, the mechanism of Kupffer cell activation following PIT is not yet fully understood. In vitro experiments suggest that the pancreatic islets may directly stimulate the Kupffer cells by some yet-unidentified, soluble factor [78]. A final pathway by which Kupffer cells become activated may exist via activation of the sinusoidal endothelium.…”