In Vitro Studies of Squalene‐Gusperimus Nanoparticles in Islet‐Containing Alginate Microcapsules to Regulate the Immune Response in the Immediate Posttransplant Period

Abstract

Grafting of microencapsulated pancreatic islets has been proposed as an alternative to exogenous insulin for the treatment of type 1 diabetes mellitus. Microencapsulated islets are protected from direct contact with immune cells and larger immune‐active molecules such as immunoglobulins. Unfortunately, many islet cells in the microcapsules are lost in the immediate period after transplantation due to an early host immune response limiting long‐term function of the graft. Gusperimus has shown to reduce the inflammatory responses to grafted encapsulated islets, but it cannot be appropriately used because it is easily hydrolyzed leading to loss of activity. To temporarily modulate the inflammatory response directly after implantation and stabilize gusperimus, squalene‐gusperimus nanoparticles (Sq‐GusNPs) are developed and incorporated in human islets‐containing alginate‐based microcapsules. A prolonged and continuous release of gusperimus is achieved. This offers an anti‐inflammatory microenvironment in the vicinity of the microcapsules and a reduction of cytokine secretion by lipopolysaccharides‐activated human macrophages. Release of gusperimus from Sq‐GusNPs does not affect the in vitro viability or function of human pancreatic islets. The data illustrate that incorporation of Sq‐GusNPs in alginate microcapsules offers an opportunity to temporarily modulate the immediate immune response after the grafting procedure of encapsulated islets cells and reduce loss of islet cells.

Species-dependent impact of immunosuppressive squalene-gusperimus nanoparticles and adipose-derived stem cells on isolated human and rat pancreatic islets

“…Recently, we developed Sq-GusNPs, a technology for reducing inflammatory responses in the immediate period post-transplantation that involves nanoencapsulation and temporary, controlled release of the anti-inflammatory agent gusperimus in the vicinity of the graft. 20 , 21 Here, we investigate whether immunosuppression with Sq-GusNPs in the presence or absence of ASCs can contribute to reduced release of cytokines in the islets or reduce initiation of cell-death processes.…”

“…Cell viability was determined using the alamarBlue TM reagent as previously reported. 20 Briefly, the reagent was diluted in culture medium (10% v/v). After treatment, ASCs or islets were washed with PBS and incubated for four hours with 0.5 mL of the diluted reagent.…”

“…Especially the immediate posttransplant period is an extremely delicate period in which more than 60% of the islets have been reported to die due to enhanced sensitivity to inflammatory stress. 20 This enhanced sensitivity is caused by a combination of disruption of the interactions between the islets and the peri-insular extracellular matrix as well as interruption of direct vascular access during the isolation process leading to low nutrient supply, high oxidative and hypoxic stress, and significant loss of insulin-producing cells posttransplant. 14 To lower this loss we presented in a previous study a new controlled release system to modulate immunity in the immediate period after implantation.…”

“… 14 To lower this loss we presented in a previous study a new controlled release system to modulate immunity in the immediate period after implantation. 20 This involves squalene-gusperimus nanoparticles (Sq-GusNPs), a nanoparticulate system designed to encapsulate the immunosuppressive drug gusperimus to enhance the efficacy of this powerful anti-inflammatory drug. 21 …”

“…Additionally, Sq-GusNPs have been shown to maintain the viability and function of human pancreatic islets under inflammatory conditions without cytotoxic effects. 20 Here, we co-cultured pancreatic islets with ASCs in the presence and absence of IFN-γ, IL-1β, and TNF-α. This was done to gain insight into how islets and ASCs mutually influence each other in the presence or absence of an immunosuppressive agent under inflammatory or basal conditions.…”