Facilitating islet transplantation using a three-step approach with mesenchymal stem cells, encapsulation, and pulsed focused ultrasound

Abstract

Background The aim of this study was to examine the effect of a three-step approach that utilizes the application of adipose tissue-derived mesenchymal stem cells (AD-MSCs), encapsulation, and pulsed focused ultrasound (pFUS) to help the engraftment and function of transplanted islets. Methods In step 1, islets were co-cultured with AD-MSCs to form a coating of AD-MSCs on islets: here, AD-MSCs had a cytoprotective effect on islets; in step 2, islets coated with AD-MSCs were conformally encapsulated in a thin layer of alginate using a co-axial air-flow method: here, the capsule enabled AD-MSCs to be in close proximity to islets; in step 3, encapsulated islets coated with AD-MSCs were treated with pFUS: here, pFUS enhanced the secretion of insulin from islets as well as stimulated the cytoprotective effect of AD-MSCs. Results Our approach was shown to prevent islet death and preserve islet functionality in vitro. When 175 syngeneic encapsulated islets coated with AD-MSCs were transplanted beneath the kidney capsule of diabetic mice, and then followed every 3 days with pFUS treatment until day 12 post-transplantation, we saw a significant improvement in islet function with diabetic animals re-establishing glycemic control over the course of our study (i.e., 30 days). In addition, our approach was able to enhance islet engraftment by facilitating their revascularization and reducing inflammation. Conclusions This study demonstrates that our clinically translatable three-step approach is able to improve the function and viability of transplanted islets.

Localized drug delivery graphene bioscaffolds for cotransplantation of islets and mesenchymal stem cells

“…The cultured AD-MSCs were enzymatically detached from culture plates upon reaching 70 to 80% confluence using 0.25% trypsin solution to obtain a single-cell suspension and resuspended in complete medium. AD-MSCs were then counted on a hemocytometer under a bright-field microscope and cocultured with AD-MSCs for 24 hours in a 1:100 ratio according to our previously published protocol ( 71 ). Bioscaffolds were sterilized by soaking them in 70% ethanol for 0.5 hours after which time they were rinsed three times in sterilized PBS.…”

“…In vitro interaction of our bioscaffolds with islets ± AD-MSCs All assays were carried out on islets alone or islet:AD-MSC units, i.e., islets cocultured with AD-MSCs for 24 hours in a 1:100 ratio according to our previously published protocol (71), manually picked under a microscope, and seeded directly into bioscaffolds (20 islets or 20 islet:AD-MSC units) or into a 96-well plate. For all in vitro experiments, isolated islets were individually counted and manually picked up under a microscope to achieve a density of 20 islets per well [20 islets in 200 l of complete medium: RPMI 1640 medium (Gibco, USA)] supplemented with 10% fetal bovine serum (FBS; Invitrogen, USA) and penicillin (50 U/ml)/streptomycin (50 g/ml) (P/S; Invitrogen, USA) were added into 96-well nonadherent tissue culture plates.…”

“…The study was conducted on a diabetic mouse model (C57BL/6, male, 6 to 8 weeks old, Charles River Laboratories, USA). To induce diabetes, each mouse received an intraperitoneal injection of STZ at the dose of 180 mg/kg; this technique is a wellestablished model for inducing diabetes in rodents and hence for studying islet transplantation (24,71,(74)(75)(76)(77) given that STZ selectively causes destruction of insulin-producing  cells within pancreatic islets (78). Tail vein blood was collected to measure blood glucose concentrations with a portable glucose meter (Bayer Contour Glucose Meter, USA) for the next 5 days.…”

Mouse models and human islet transplantation sites for intravital imaging

“…In the endogenous pancreas, a well vascularized environment also allows for efficient dissemination of insulin released from the islets ( 10 ), with numerous studies demonstrating transplant restoration of euglycemia in several diabetic immunodeficient mouse models ( 58 – 60 ). With sufficient vascularization, transplanted islet grafts are stable and can survive for over a month within the host animals ( 61 , 62 ), with the current longest reported time of survival being over 300 days ( 60 ).…”

Effect of Flow Rate Modulation on Alginate Emulsification in Multistage Microfluidics

“…Emulsification is a technology used to protect valuable therapeutic molecules [1,2], living cells [3], or even secretory tissues/islets [4][5][6] in sealed capsules that can release these contents at controlled rates under the influences of specific conditions. This technology dampens or even prevents rapid degradation [7], facilitates immuno-isolation [8], and inactivates target materials until the product reaches the intended spatial location [1,2].…”