![Glucose-induced beta-cell insulin secretion. (A): KATP-dependent insulin secretion pathway. (B): Insulin biphasic secretion kinetics. Adapted with permission from [6].](https://www.researchgate.net/publication/329833417/figure/fig1/AS:706262643789824@1545397544287/Glucose-induced-beta-cell-insulin-secretion-A-KATP-dependent-insulin-secretion_Q320.jpg)
![Microfluidic islet array for high content and high resolution assay. (A): Microfluidic islet array and design. (B) Islet loading optimization. (C) Fluorescence imaging of calcium influx and mitochondrial potentials change in response to glucose or KCI and heat-maps of calcium influx and mitochondrial potentials changes. Adapted with permission from [25].](https://www.researchgate.net/publication/329833417/figure/fig2/AS:706262643781633@1545397544354/Microfluidic-islet-array-for-high-content-and-high-resolution-assay-A-Microfluidic_Q320.jpg)
![Microfluidic encapsulated islet array for high content and high resolution assay. (A) Design principle and dimension for the three-layer array. (B) Hydrodynamic trapping computer simulation. (C) Oxygen modulation. Adapted with permission from [26].](https://www.researchgate.net/publication/329833417/figure/fig3/AS:706262643789825@1545397544445/Microfluidic-encapsulated-islet-array-for-high-content-and-high-resolution-assay-A_Q320.jpg)
![Hypoxia impaired intracellular calcium signaling and mitochondrial potentials of encapsulated human islets in response to glucose. (A) Representative traces of calcium influx of encapsulated human islets in response to 25mM glucose. (B) Representative traces of mitochondrial potential changes of encapsulated human islets in response to 25mM glucose. Adapted with permission from [26].](https://www.researchgate.net/publication/329833417/figure/fig4/AS:706262643789826@1545397544593/Hypoxia-impaired-intracellular-calcium-signaling-and-mitochondrial-potentials-of_Q320.jpg)
![The surface tension driven pumpless microfluidic for islets. (A) Working principle of the surface tension driven flow delivery, schematic of the pumpless device, and device dimension. (B) Computer simulation of flow rat in the microchannel. Adapted with permission from [27].](https://www.researchgate.net/publication/329833417/figure/fig5/AS:706262643789827@1545397544618/The-surface-tension-driven-pumpless-microfluidic-for-islets-A-Working-principle-of-the_Q320.jpg)
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Application of Microfluidic Biochips for Human Islet Transplantation
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... A common theme among these phenomena concerns metabolic stress (e.g., islet isolation, insulin resistance, etc.), and the authors propose several ways to tackle this, highlighting an interesting and relatively unexplored pathway involving osteocalcin. On the other hand, Holzer et al. [9] provide a concise discussion on the potential of microfluidic devices as tools to study the physiology and pathophysiology of human islets, as well as their individual cells. In this review, the authors elaborate on basic principles for device design and fabrication. ...
strong>Editorial Islet Transplantation: How Much Have We Advanced and How to Keep Moving Forward? Braulio A. Marfil-Garza 1, Tatsuya Kin 1, 2, * 1. Clinical Islet Transplant Program, University of Alberta, Edmonton, Alberta, Canada; E-Mails: marfilga@ualberta.ca ; tkin@ualberta.ca 2. Alberta Islet Distribution Program, Clinical Islet Laboratory, Edmonton, Alberta, Canada * Correspondence: Tatsuya Kin ; E-Mail: tkin@ualberta.ca Academic Editor: Haval Shirwan Special Issue : Current Advancement of Islet Cell Transplantation in the Treatment of Diabetes Mellitus OBM Transplantation 2022, volume 6, issue 4doi:10.21926/obm.transplant.2204171 Received: December 11, 2022 Accepted: December 18, 2022 Published: December 20, 2022
... The β cell replacement therapy in the form of either pancreas or allogeneic islet transplantation has shown to be a safe alternative treatment, offering more precise control over blood glucose, reducing incidents of unaware hypoglycemia, and improving quality of life in T1D patients [6••]. Although it is still considered experimental by the Food and Drug Administration (FDA), islet transplantation has many advantages over whole pancreas transplantation for T1D, since it involves only a minor surgical procedure with much lower morbidity and mortality rates [7][8][9]. The transplanted islets can physiologically regulate insulin and glucagon secretion in response to instantaneous blood glucose changes, which provides superior glycemic control compared to insulin injection in a patient with frequent hypoglycemia unawareness. ...
Purpose of Review
Over the years, microfluidics has become a mature technology, providing as an excellent platform for islet study. This review covers recent advances and developments of microfluidic systems for evaluating and preserving islet function for cell-based therapy in type 1 diabetes (T1D), as well as selected articles published over the past 3 years.
Recent Findings
Novel microfluidic devices integrated with advanced imaging and biosensor technologies allow live-cell monitoring of multiple metabolic components, which are highly involved in islet function but previously directly undetectable in classic procedures. Additionally, considerable progress in the development of microfluidic systems for studying aggregated pseudo-islets and encapsulated islets show great potential of using microfluidics for biomanufacturing of islet biologics for cell replacement therapy in T1D.
Summary
Although still in the proof-of-concept stage, microfluidic technology has shown numerous advantages over traditional methodology on multi-parameter characterization of not only isolated pancreatic islets but also new emerging islet-like cell biologics for basic, translational, and clinical applications.
Chronic disorders such as diabetes mellitus are associated with multiple organ dysfunction, including retinopathy, neuropathy, nephropathy, peripheral vascular disease, and vascular disease. Lifelong subcutaneous insulin injections are currently the only treatment option for patients with Type 1 diabetes mellitus, and it poses numerous challenges. Since the breakthrough achieved from the Edmonton protocol in the year 2000, there has been important research to investigate whether islet cell transplantation can achieve long-term normoglycemia in patients without the need for insulin. The use of biopolymeric scaffold to enclose islet cells has also been explored to improve survivability and viability of islet cells. This review paper summarizes the latest research in using biopolymeric scaffolds in islet transplantation and how microfluidic devices can assist.
The long-term management type-1 diabetes (T1D) is currently achieved through lifelong exogenous insulin injections. Although there is no cure for T1D, transplantation of pancreatic islet of Langerhans has the potential...
We present a novel pumpless microfluidic array driven by surface tension for studying the physiology of pancreatic islets of Langerhans. Efficient fluid flow in the array is achieved by surface tension-generated pressure as a result of inlet and outlet size differences. Flow properties are characterized in numerical simulation and further confirmed by experimental measurements. Using this device, we perform a set of biological assays, which include real-time fluorescent imaging and insulin secretion kinetics for both mouse and human islets. Our results demonstrate that this system not only drastically simplifies previously published experimental protocols for islet study by eliminating the need for external pumps/tubing and reducing the volume of solution consumption, but it also achieves a higher analytical spatiotemporal resolution due to efficient flow exchanges and the extremely small volume of solutions required. Overall, the microfluidic platform presented can be used as a potential powerful tool for understanding islet physiology, antidiabetic drug development, and islet transplantation.
Objective:
Impaired awareness of hypoglycemia (IAH) and severe hypoglycemic events (SHEs) cause substantial morbidity and mortality in patients with type 1 diabetes (T1D). Current therapies are effective in preventing SHEs in 50-80% of patients with IAH and SHEs, leaving a substantial number of patients at risk. We evaluated the effectiveness and safety of a standardized human pancreatic islet product in subjects in whom IAH and SHEs persisted despite medical treatment.
Research design and methods:
This multicenter, single-arm, phase 3 study of the investigational product purified human pancreatic islets (PHPI) was conducted at eight centers in North America. Forty-eight adults with T1D for >5 years, absent stimulated C-peptide, and documented IAH and SHEs despite expert care were enrolled. Each received immunosuppression and one or more transplants of PHPI, manufactured on-site under good manufacturing practice conditions using a common batch record and standardized lot release criteria and test methods. The primary end point was the achievement of HbA1c <7.0% (53 mmol/mol) at day 365 and freedom from SHEs from day 28 to day 365 after the first transplant.
Results:
The primary end point was successfully met by 87.5% of subjects at 1 year, and by 71% at 2 years. The median HbA1c level was 5.6% (38 mmol/mol) at both 1 and 2 years. Hypoglycemia awareness was restored, with highly significant improvements in Clarke and HYPO scores (P > 0.0001). No study-related deaths or disabilities occurred. Five of the enrollees (10.4%) experienced bleeds requiring transfusions (corresponding to 5 of 75 procedures), and two enrollees (4.1%) had infections attributed to immunosuppression. Glomerular filtration rate decreased significantly on immunosuppression, and donor-specific antibodies developed in two patients.
Conclusions:
Transplanted PHPI provided glycemic control, restoration of hypoglycemia awareness, and protection from SHEs in subjects with intractable IAH and SHEs. Safety events occurred related to the infusion procedure and immunosuppression, including bleeding and decreased renal function. Islet transplantation should be considered for patients with T1D and IAH in whom other, less invasive current treatments have been ineffective in preventing SHEs.
This report summarizes a 5-year phase 1/2 allogeneic islet transplantation clinical trial conducted at the University of Illinois at Chicago (UIC). Ten patients were enrolled in this single center, open label, and prospective trial in which patients received 1-3 transplants. The first four subjects underwent islet transplantation with the Edmonton immunosuppressive regimen and the remaining six subjects received the UIC immunosuppressive protocol (Edmonton plus etanercept and exenatide). All 10 patients achieved insulin independence after 1-3 transplants. At 5 years of follow-up, 6 of the initial 10 patients were free of exogenous insulin. During the follow-up period, 7 of the 10 patients maintained positive C-peptide levels and a composite hypoglycemic score of 0. Most patients maintained HbA1c levels <6.0 % (42.1 mmol/mol) and a significantly improved β-score. In conclusion, this study demonstrated long-term islet graft function without using T cell depleting induction, with an encouraging outcome that includes 60 % of patients remaining insulin independent after 5 years of initial transplantation.
To describe trends of primary efficacy and safety outcomes of islet transplantation in type 1 diabetes recipients with severe hypoglycemia from the Collaborative Islet Transplant Registry (CITR) from 1999 to 2010.
A total of 677 islet transplant-alone or islet-after-kidney recipients with type 1 diabetes in the CITR were analyzed for five primary efficacy outcomes and overall safety to identify any differences by early (1999-2002), mid (2003-2006), or recent (2007-2010) transplant era based on annual follow-up to 5 years.
Insulin independence at 3 years after transplant improved from 27% in the early era (1999-2002, n = 214) to 37% in the mid (2003-2006, n = 255) and to 44% in the most recent era (2007-2010, n = 208; P = 0.006 for years-by-era; P = 0.01 for era alone). C-peptide ≥0.3 ng/mL, indicative of islet graft function, was retained longer in the most recent era (P < 0.001). Reduction of HbA(1c) and resolution of severe hypoglycemia exhibited enduring long-term effects. Fasting blood glucose stabilization also showed improvements in the most recent era. There were also modest reductions in the occurrence of adverse events. The islet reinfusion rate was lower: 48% by 1 year in 2007-2010 vs. 60-65% in 1999-2006 (P < 0.01). Recipients that ever achieved insulin-independence experienced longer duration of islet graft function (P < 0.001).
The CITR shows improvement in primary efficacy and safety outcomes of islet transplantation in recipients who received transplants in 2007-2010 compared with those in 1999-2006, with fewer islet infusions and adverse events per recipient.
We describe and characterize a pumping mechanism that leverages the momentum present in small droplets ejected from a micro-nozzle to drive flow in an open microfluidic device. This approach allows driving flow in a microfluidic device in a regime that offers unique features different to those achievable with typical passive pumping or syringe-pump driven flow. Two flow regimes with specific flow characteristics are described: inertia enhanced passive pumping, in which fluid exchange times in the channel are significantly reduced, and inertia actuated flow, in which it is possible to initiate flow in an empty channel or against natural pressure gradients. Momentum is leveraged to create rapid fluid exchanges, instantaneous flow reversal, filling and mixing inside the microfluidic device.
Dielectric spectroscopy could potentially be a powerful tool to monitor isolated human pancreatic islets for applications in diabetes therapy and research. Isolated intact human islets provide the most relevant means to understand the cellular and molecular mechanisms associated with diabetes. The advantages of dielectric spectroscopy for continuous islet monitoring are that it is a non-invasive, inexpensive and real-time technique. We have previously assessed the dielectric response of human islet samples during stimulation and differentiation. Because of the complex geometry of islets, analytical solutions are not sufficiently representative to provide a pertinent model of islet dielectric response. Here, we present a finite element dielectric model of a single intact islet that takes into account the tight packing of islet cells and intercellular junctions. The simulation yielded dielectric spectra characteristic of cell aggregates, similar to those produced with islets. In addition, the simulation showed that both exocytosis, such as what occurs during insulin secretion, and differential gap junction expression have significant effects on islet dielectric response. Since the progression of diabetes has some connections with dysfunctional islet gap junctions and insulin secretion, the ability to monitor these islet features with dielectric spectroscopy would benefit diabetes research.
In this study, we present a novel microfluidic array for high resolution imaging of individual pancreatic islets. The device is based on hydrodynamic trapping principles and enables real-time analysis of islet cellular responses to insulin secretagogues. This device has significant advantages over our previously published perifusion chamber device including significantly increased analytical power and assay sensitivity, as well as improved spatiotemporal resolution. The islet array, with live-cell multiparametric imaging intergration, provides a better tool to understand the physiological and pathophysiological changes of pancreatic islets through the analysis of single islet responses. This platform demonstrates the feasibility of array-based islet cellular analysis and opens up new modality to conduct informative and quantitive evaluation of islets and cell-based screening for new diabetes treatments.
In this report, we present a novel microfluidic islet array based on a hydrodynamic trapping principle. The lab-on-a-chip studies with live-cell multiparametric imaging allow understanding of physiological and pathophysiological changes of microencapsulated islets under hypoxic conditions. Using this microfluidic array and imaging analysis techniques, we demonstrate that hypoxia impairs the function of microencapsulated islets at single islet level, showing a heterogeneous pattern reflected in intracellular calcium signaling, mitochondrial energetic, and redox activity. Our approach demonstrates an improvement over conventional hypoxia chambers that is able to rapidly equilibrate to true hypoxia levels through the integration of dynamic oxygenation. This work demonstrates the feasibility of array-based cellular analysis and opens up new modality to conduct informative analysis and cell-based screening for microencapsulated pancreatic islets.
Background:
In the absence of a reliable islet potency assay, nude mice (NM) transplantation is the criterion standard to assess islet quality for clinical transplantation. There are factors other than islet quality that affect the transplant outcome.
Methods:
Here, we analyzed the transplant outcomes in 335 NM receiving islets from human (n=103), porcine (n=205), and nonhuman primate (NHP; n=27) donors. The islets (750, 1000, and 2000 islet equivalents [IEQ]) were transplanted under the kidney capsule of streptozotocin-induced diabetic NM.
Results:
The proportion of mice that achieved normoglycemia was significantly higher in the group implanted with 2000 IEQ of human, porcine, or NHP islets (75% normoglycemic) versus groups that were implanted with 750 IEQ (7% normoglycemic) and 1000 IEQ (30% normoglycemic). In this study, we observed that the purity of porcine islet preparations (P≤0.001), islet pellet size in porcine preparations (P≤ 0.01), and mice recipient body weight for human islet preparations (P=0.013) were independently associated with successful transplant outcome. NHP islets of 1000 IEQ were sufficient to achieve normoglycemic condition (83%). An islet mass of 2000 IEQ, high islet purity, increased recipient body weight, and high islet pellet volume increased the likelihood of successful reversal of diabetes in transplanted mice. Also, higher insulin secretory status of islets at basal stimulus was associated with a reduced mouse cure rate. The cumulative incidence of graft failure was significantly greater in human islets (56.12%) compared with porcine islets (35.57%; P≤0.001).
Conclusion:
Factors affecting NM bioassay were identified (islet mass, islet purity, pellet size, in vitro insulin secretory capability, and mouse recipient body weight) and should be considered when evaluating islet function.