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Pancreatic Islet Cell Transplantation: An Update
Abstract and Figures
Transplantation of pancreatic islets, as a therapeutic modality for type 1 diabetes mellitus (T1DM), at this stage of its development, is reserved for patients with severe glycemic variability, progressive diabetic complications, and life threatening hypoglycemia unawareness, regardless of intensive insulin management. It has not succeeded to become the method of choice for treating T1DM because of limited supply and suboptimal yields of procurement and isolation of islets, graft failure, and relatively high requirements, i.e., at least 10,000 functional Islet Equivalents per kg of patient weight, to achieve prolonged insulin independence and glucose stability. Efforts aimed at making islet transplantation a competitive alternative to exogenous insulin injections for treating T1DM have focused on improving the longevity and functionality of islet cells. In order to succeed, these efforts need to be complemented by others to optimize the rate and efficiency of encapsulation.
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... The allogeneic donor cell sources are limited for some endocrine diseases, such as diabetes ( Hatziavramidis et al., 2013 ), but recent progress in the stem cell research ( Pellegrini et al., 2016 ) can potentially eliminate the donor shortage barrier. Therefore, pluripotent stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are currently used in cell transplantation. ...
... Selective withdrawal has already found applications in the field of water quality control ( Fontane et al., 1981 ), igneous geology of volcanic eruptions ( Lister, 1989 ), and more recently, biomedical science ( Hatziavramidis et al., 2013 ). It is the draining of one of two immiscible fluids from two horizontally-stratified layers through a tube with its tip in the layer of the draining fluid, placed close to the fluid-fluid interface ( Psihogios et al., 2015 ). ...
The development of an efficient microencapsulation apparatus is a major challenge for islet transplantation. To that end, the flow generated by selective withdrawal in an apparatus for micro-encapsulation of pancreatic islets is studied through CFD simulations. Each islet enters individually a chamber containing a twolayer system in which is encapsulated by selective withdrawal. Optimal encapsulation occurs, when the perturbed interface is kept stable and transition to viscous entrainment is prevented. Simulations were validated with experimental data. Contrary to previous studies that simplify the problem by approximating the tubes as a doublet of a point mass source and sink, the model presented here employs a detailed geometry. Numerical results shed light on the dependence of the shape of the interface on flow, geometry and physical parameters. These observations can contribute to the design of encapsulation apparatuses considering polydispersity in size and the different shape of the islets.
... Insulin replacement therapy does not stop the autoimmune attack on b-cells and has limitations, including serious complications that lead to significant mobility and mortality (3). Transplantation of islet cells from healthy donors is an alternative therapy but suffers from drawbacks, including limited availability of islets cells and the requirement for lifelong immunosuppression (4). Ag-specific immunotherapy (ASI) has been the paradigmatic goal for treating T1D for several decades, as it strives to restore self-tolerance by targeting only the autoreactive T cells in the adaptive immune repertoire while leaving responses to foreign Ags intact (3,58). ...
Ag-specific immunotherapy to restore immune tolerance to self-antigens, without global immune suppression, is a long-standing goal in the treatment of autoimmune disorders such as type 1 diabetes (T1D). However, vaccination with autoantigens such as insulin or glutamic acid decarboxylase have largely failed in human T1D trials. Induction and maintenance of peripheral tolerance by vaccination requires efficient autoantigen presentation by APCs. In this study, we show that a lipophilic modification at the N-terminal end of CD4+ epitopes (lipo-peptides) dramatically improves peptide Ag presentation. We designed amphiphilic lipo-peptides to efficiently target APCs in the lymph nodes by binding and trafficking with endogenous albumin. Additionally, we show that lipophilic modification anchors the peptide into the membranes of APCs, enabling a bivalent cell-surface Ag presentation. The s.c. injected lipo-peptide accumulates in the APCs in the lymph node, enhances the potency and duration of peptide Ag presentation by APCs, and induces Ag-specific immune tolerance that controls both T cell- and B cell-mediated immunity. Immunization with an amphiphilic insulin B chain 9-23 peptide, an immunodominant CD4+ T cell epitope in NOD mice, significantly suppresses the activation of T cells, increases inhibitory cytokine production, induces regulatory T cells, and delays the onset and lowers the incidence of T1D. Importantly, treatment with a lipophilic β-cell peptide mixture delays progression to end-stage diabetes in acutely diabetic NOD mice, whereas the same doses of standard soluble peptides were not effective. Amphiphilic modification effectively enhances Ag presentation for peptide-based immune regulation of autoimmune diseases.
... Terapi DM tipe 2 dengan obat antidiabetik oral, terapi sensitifikasi dan suplai insulin eksogen (Piya et al., 2010;Hatziavramidis et al., 2013) masih memiliki keterbatasan. Misalnya penggunaan insulin eksogen pada pasien dapat menyebabkan episode hipoglikemia. ...
Diabetes mellitus type 2 is the most common type of diabetes. This study was conducted to determine the effect of Mesenchymal Stem Cell-Conditioned Medium (MSC-CM) in Homeostatic Model Assessment of β-cell function (HOMA-β) value, normal Langerhans cells, and Transcription Factor 7-Like 2 (TCF7L2) gene expression in type 2 diabetic rats model. As many as 27 male Sprague Dawley rats were divided into 3 study research groups: normal control (9 normal rats), diabetic control (9 type 2 diabetic rats, induced by 60 mg/kg BW Streptozotocin and 120 mg/kg BW Nicotinamide i.p.), and treatment (9 type 2 diabetic rats treatment with 0.1 ml/200g BW MSC-CM i.p.). On day 30 after therapy, the expression of TCF7L2 gene was performed with real time-quantitative PCR (RT-qPCR). The HOMA-β value were calculated based on Fasting Insulins (FINs) levels and Fasting Blood Glucose (FBG) levels data from other research team members. Based on results, MSC-CM increases the HOMA-β value and amount of normal Langerhans cells of treatment group that indicates amelioration effect of MSC-CM, but there was no significant difference in TCF7L2 gene expression level between diabetic control and treatment group.
... Coating of scaffold materials with proteins or other biomolecules reduces the chances of detection and triggering of the immune system (Campoccia et al. 2013). Encapsulation of construct by selectively permeable hollow fibers and sheets (Hatziavramidis et al. 2013) and immunocloaking using nanofilm to prevent antigen recognition by the immune system (Pareta et al. 2012) are the two commonly used methods to avoid immune responses. Overexpression of anti-inflammatory factors in stem cells using transfection and other techniques has increased the survival of cells in scaffolds (Holladay et al. 2011). ...
Tissue damage caused by disease or trauma necessitates a substitution of the damaged tissue through tissue engineering and regenerative medicine. It is a multidisciplinary research in the field of tissue engineering that deals with the synthesis of various kinds of human tissue equivalents, such as heart muscle, bone, cartilage, blood vessels, and nerves. It potentially leads to entire organ replacement by employing principles from the biology (molecular, cell biology, physiology, immunology, chemical) and engineering (electrical, materials science, mechanical) domains. The development of stem cells has opened a vast realm for regenerative medicines, tissue, and organs. Tissue engineering and regenerative medicines adopt the evaluation of biomaterial performance and behavior. The evaluation of properties also includes its drug delivery nature and biomimetic properties. The condemnatory hurdle in tissue engineering and regenerative medicine lies in understanding the interaction between the cells and engineered tissues, the influence of physical and chemical stimuli on cell growth, and cell function, migration, and differentiation. This chapter is a comprehensive discussion on interdisciplinary involvement in tissue engineering and regenerative medicines.
... The transplantation of pancreatic islets for the treatment of Type-1 diabetes is currently performed via perfusion of islet suspensions into the portal vein (Hatziavramidis, Karatzas, & Chrousos, 2013). During this procedure, many islets die, and patients often require several transplantations before they can become insulin independent (Paraskevas, Maysinger, Wang, Duguid, & Rosenberg, 2000). ...
Porous biodegradable scaffolds have many applications in bioengineering, ranging from cell culture and transplantation, to support structures, to induce blood vessel and tissue formation in vivo. While numerous strategies have been developed for the manufacture of porous scaffolds, it remains challenging to control the spatial organization of the pores. In this study, we introduce the use of the granular convection effect, also known as the muesli or brazil nut effect, to rapidly engineer particulate templates with a vertical size gradient. These templates can then be used to prepare scaffolds with pore size gradients. To demonstrate this approach, we prepared templates with particle size gradients, which were then infused with a prepolymer solution consisting of the pentaerythritol ethoxylate (polyol), sebacoyl chloride (acid chloride), and poly(caprolactone). Following curing, the template was dissolved to yield biodegradable polyester‐ether scaffolds with pore size gradients that could be tuned depending on the size range of the particulates used. The application of these scaffolds was demonstrated using pancreatic islets, which were loaded via centrifugation and retained within the scaffold's pores without a decrease in viability. The proposed strategy provides a facile approach to prepare templates with spatially organized pores that could potentially be used for cell transplantation, or guided tissue formation.
... Stochastic loading and islet separation, processing stress reduction, high yields and rates of individual encapsulation, and efficient polymerization are issues that must receive proper attention. A microencapsulation islet apparatus was recently designed aiming at efficiently encapsulating a high amount of islets within a reasonable period of time [99] (Fig. 2). ...
Type 1 diabetes mellitus (T1DM) is a disorder that decimates pancreatic β-cells which produce insulin. Direct pancreatic islet transplantation cannot serve as a widespread therapeutic modality owing to the need for lifelong immunosuppression and donor shortage. Therefore, several encapsulation techniques have been developed to enclose the islets in semipermeable vehicles that will allow oxygen and nutrient input as well as insulin, other metabolites and waste output, while accomplishing immunoisolation. Although encapsulation technology continues to face significant obstacles, recent advances in material science, stem cell biology and immunology potentially serve as pathways to success. This review summarizes the accomplishments of the past 5 years. The most-recently developed strategies for islet encapsulation are reviewed regarding type 1 diabetes mellitus treatment aiming at efficient insulin production and delivery.
... Type 2 diabetes mellitus (T2DM) comprises 90% of all causes of diabetes, which is a metabolic stress resulting from over-nutrition-and insufficient activity-induced insulin resistance and beta cell impairment [2,3]. The routine therapies for T2DM involve insulin sensitizers with exogenous insulin supply, but these drugs temporarily ameliorate hyperglycemia, and ultimately progressive beta cell dysfunction happens [4]. Type 1 diabetes (T1DM) comprises 10% of all causes of diabetes, which is an insulin-dependent autoimmune disorder characterized by the destruction of beta cells with serious short-term and long-term implications. ...
Type 2 diabetes mellitus is the most common type of diabetes. Though various types of therapy have been used to treat type 2 diabetes, there are still limitations found. This study was conducted to determine the effect of MSC-CM on pancreatic histopathology and the normal number of Langerhans cells in type 2 diabetic rats. This study was a pure experimental study with the Posttest Control Group design. A total of 27 male Sprague Dawley rats were divided into 3 groups: 9 healty rats as normal control (K (-)); 9 type 2 diabetic rats as diabetic control (K (+)), induced with 60 mg/kg BW STZ (ip) and 120 mg/kg BW NA (ip), and the treatment group (P) were 9 rats induced by type 2 diabetic and treated with 0.1 ml/200 g BW (i.p) every 3 days for 10 times. On the 30th day after treatment, the rats were sacrificed and the pancreatic tissue was taken for histopathology testing with Hematoxylin-Eosin staining. The results were analyzed with the Image J program. The results showed an improvement in the histopathological profile of the pancreas and there was an increase in the number of normal Langerhans islet cells in the treatment group given MSC-CM compared to the positive control group. Abstrak Diabetes mellitus tipe 2 merupakan jenis diabetes yang paling banyak terjadi. Berbagai macam terapi telah digunakan untuk menangani DM (Diabetes Mellitus) tipe 2, namun masih terdapat keterbatasan. Penelitian ini dilakukan untuk mengetahui pengaruh MT-SPM terhadap histopatologi pankreas dan jumlah sel normal Langerhans pada tikus model diabetes melitus tipe 2. Penelitian ini merupakan penelitian eksperimental murni dengan desain Posttest Control Group. Sebanyak 27 ekor tikus Sprague Dawley jantan dibagi menjadi 3 kelompok: kontrol normal (K(-)) yaitu 9 tikus sehat, kontrol diabetes (K(+)) yaitu 9 tikus yang diinduksi DM tipe 2 dengan 60 mg/kg BB STZ (i.p) dan 120 mg/kg BB NA (i.p), dan kelompok perlakuan (P) yaitu 9 tikus yang diinduksi DM tipe 2 dan diberi perlakuan dengan 0,1 ml/200 g BB (i.p) setiap 3 hari selama 10 kali. Pada hari ke-30 setelah perlakuan, tikus dikorbankan dan diambil jaringan pankreasnya untuk diuji histopatologi dengan pewarnaan Hematoksilin-Eosin. Hasil tersebut dianalisis dengan program Image J. Hasil penelitian menunjukkan terjadi perbaikan pada profil histopatologi pankreas dan terdapat peningkatan jumlah sel normal di islet Langerhans pada kelompok perlakuan yang diberi MT-SPM dibandingkan kelompok kontrol positif. Kata kunci: DM tipe 2, MT-SPM, histopatologi pankreas Diterima: 9 Agustus
The motion of biological particles is simulated in a two-dimensional hydrodynamic focusing domain. A computational model using the Arbitrary Lagrangian-Eulerian (ALE) method is presented and validated. Results shed light on the dependence of the motion of limited number of particles on their morphology and density.
Continuum models of two-phase flows of solids and liquids use constitutive assumptions to close the equations. A more fundamental approach is a molecular dynamic simulation of flowing big particles based on reliable macroscopic equations for both solid and liquid. We developed a package that simulates the unsteady two-dimensional solid-liquid two-phase flows using the Navier-Stokes equations for the liquid and Newton's equations of motion for the solid particles. The Navier-Stokes equations are solved using a finite-element formulation and Newton's equations of motion are solved using an explicit-implicit scheme. We show that the simplest fully explicit scheme to update the particle motion using Newton's equations is unstable. To correct this instability we propose and implement and Explicit-Implicit Scheme in which, at each time step, the positions of the particles are updated explicitly, the computational domain is remeshed, the solution at the previous time is mapped onto the new mesh, and finally the nonlinear Navier-Stokes equation and the implicitly discretized Newton's equations for particle velocities are solved on the new mesh iteratively. The numerical simulation reveals the effect of vortex shedding on the motion of the cylinders and reproduces the drafting, kissing, and tumbling scenario which is the dominant rearrangement mechanism in two-phase flow of solids and liquids in beds of spheres which are constrained to move in only two dimensions.
The initial step in successful islet transplantation is procurement of healthy donor islets. Given the limited number of donor pancreata selected for islet isolation and that islets from multiple donors are typically required to obtain insulin independence, it is critical to improve pancreas procurement rates and yield of islets for transplantation. Islets are delicate microorgans that are susceptible to apoptosis, hypoxia, and ischemia during isolation, culture, and the peritransplant period. Once the islets are engrafted, both prompt revascularization and protection from beta-cell death and graft rejection are key to secure long-term survival and function. To facilitate the engraftment of more robust islets suitable for combating the challenging isolation period and proinflammatory transplantation milieu, numerous approaches have been employed to prevent beta-cell dysfunction and death including immune modulation, prevention of apoptosis and hypoxia, as well as stimulation of growth factors, angiogenesis, and reinnervation. In addition to briefly discussing islet isolation procedures, procurement rates, and islet transplantation, the relevant literature pertaining to successful suboptimal islet transplantation is reviewed to provide insight into potential approaches to balance the limited supply of available donor islets.
A hydrodynamic analysis of a selective-withdrawal process suitable for the micro-encapsulation of pancreatic islets is presented. In the micro-encapsulation device, a feeding system located on the upper side of a water–oil interface dispenses individual cells or cell aggregates in a single file by hydrodynamic focusing, while a valveless, diffuser-nozzle micro-pump located on the lower side of the interface removes the encapsulated islets for further processing. The apparatus ensures the separate encapsulation of the individual islets by a structurally stable, semi-permeable, controlled thickness membrane. In the theoretical model, the feed nozzle is modeled as a point source and the removal nozzle is modeled as a point sink. Small and large deformations of the interface are considered by analytical and boundary element methods, and critical conditions for selective withdrawal are established. r
This paper describes hydrodynamic focusing inside a micromachined flow cytometer. Flow cytometry is a process whereby cells are analyzed and sorted based on hydrodynamic focusing phenomenon and specific cellular characteristics. In this study, the hydrodynamic focusing phenomenon is first modeled by employing potential flow theory. Then the flow field inside the flow cytometer is numerically simulated. The effect of the device geometry and relative sheath and sample flow rate on the focusing of the center flow is explored systematically. At last, a micromachine-based flow chamber is designed and fabricated on plastic substrates as a micro flow cytometer. Hydrodynamic focusing is verified with the use of microscopic visualization of water sheath flows and dye-containing sample flow. Experimental data indicate that the size of focused sample stream can be reduced to about 3 μm, which is applicable to cell sorting and counting.
This paper and the accompanying video segment show how the motions of sedimenting particles may be simulated by direct computations based on the Navier-Stokes equations and the particles equations of motion. Sedimenting and fluidized particles are confined by closely spaced walls to move essentially in two dimensions under forces determined by three-dimensional motions of the fluidizing liquids. Attention is confined to the case when there are only few particles, not more than four. The experiments and simulations give rise to deterministic dynamics, to equilibrium positions and steady flows, to Hopf bifurcation and wavy fall trajectories and to more chaotic motions. It is shown that long bodies always turn to put their broadside perpendicular to the stream. The same mechanism which causes long bodies to turn broadside-on causes spherical bodies, which come into contact by wake interactions, to tumble, giving rise to a flow induced anisotropy in which across stream arrangements are favored. The numerical simulation, unlike the experiments, is strictly two-dimensional, but many of the observed features of the experiments are predicted by the simulation. The video segment on which this paper is based is a stand alone document. The paper gives additional information which is not conveniently expressed in a video format.
The capillary instability of a liquid thread containing a regular array of spherical particles along the centreline is considered with reference to microencapsulation. The thread interface may be clean or occupied by an insoluble surfactant. The main goal of the analysis is to illustrate the effect of the particle spacing on the growth rate of axisymmetric perturbations and identify the structure of the most unstable modes. A normal-mode linear stability analysis based on Fourier expansions for Stokes flow reveals that, at small particle separations, the interfacial profiles are nearly pure sinusoidal waves whose growth rate is nearly equal to that of a pure thread devoid of particles. Higher harmonics suddenly enter the normal modes for moderate and large particle separations, elevating the growth rates and yielding a stability diagram that consists of a sequence of superposed pure-thread lobes. A complementary numerical stability analysis based on the boundary integral formulation for Stokes flow reveals the strong stabilizing effect of particles whose radius is comparable to the thread radius. Numerical simulations of the finite-amplitude motion based on the boundary integral method demonstrate that thread breakup leads to particles coated with annular layers of different thicknesses.
When fluid is withdrawn from a body of stratified fluid the surfaces of constant density are deformed towards the region of withdrawal. The equations describing the flow caused by withdrawal through a point sink in a two-layer unbounded system in which viscous forces dominate are formulated using the boundary-integral representation of Stokes flow. It is shown by dimensional and analytic arguments that surface tension between the layers is a necessary condition for the stability of an interfacial equilibrium in which only one fluid is withdrawn. The critical flow rate above which both fluids are withdrawn is determined numerically as a function of the capillary number. When the flow is supercritical a small adaptation of the numerical scheme allows the proportion of fluid withdrawn from each layer to be found. The various analyses and conclusions further our understanding of the physical processes that determine the compositional output of volcanic eruptions that tap an underlying stratified reservoir of magma.
A method has been defined to interfacially photopolymerize poly(ethylene glycol) diacrylates (PEG diacrylates) to form a crosslinked hydrogel membrane upon the surfaces of porcine islets of Langerhans to serve as an immune barrier for allo- and xenotransplantation. A sensitivity study of six key parameters in the interfacial photopolymerization process was performed to aid in determination of the optimal encapsulation conditions, leading to the most uniform hydrogel membranes and viable islets. The key parameters included the concentrations of the components of the initiation scheme, namely eosin Y, triethanolamine, and 1-vinyl 2-pyrrolidinone. Other parameters investigated included the duration and flux of laser irradiation and the PEG diacrylate molecular weight. Each parameter was doubled and halved from the standard conditions used in the encapsulation process while holding all the remaining parameters at the standard conditions. The effects of changing each parameter on islet viability, encapsulation efficiency, and gel thickness were quantified. Islet viability was sensitive to the duration of laser illumination, viability significantly increasing as the duration was reduced. Encapsulation efficiency was sensitive to the concentrations of eosin Y, triethanolamine, and 1-vinyl 2-pyrrolidinone, to the laser flux, and to the PEG diacrylate molecular weight. Increasing the concentration of eosin Y significantly improved the encapsulation efficiency, while decreasing the concentration of 1-vinyl 2-pyrrolidinone and increasing the concentration of triethanolamine had the greatest effects in significantly reducing the encapsulation efficiency. Gel thickness was sensitive to the concentrations of triethanolamine and 1-vinyl 2-pyrrolidinone, to the duration of laser illumination, and to the PEG diacrylate molecular weight. Increasing the PEG diacrylate molecular weight significantly increased the gel thickness, while decreasing the concentration of 1-vinyl 2-pyrrolidinone and increasing the concentration of triethanolamine had the greatest effects in significantly reducing the gel thickness. From this sensitivity study, conditions were determined to encapsulate porcine islets, resulting in greater than 90% islet viability and greater than 90% encapsulation efficiency. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 655–665, 1998
A non-linear vibration model for fluid–membrane coupling is developed for simulating the behaviour of valveless micropumps. The analytical solution for fluid–membrane coupling vibration has been approximated using the Galerkin and small parameter perturbation methods. Specifically, the vibration response of the membrane and the mean flux through a valveless membrane micropump are investigated in detail. The effects of the pressure loss coefficients of the diffuser and the coupling parameter on the mean flux are examined. An optimal working frequency range for the valveless membrane micropump is obtained. Numerical examples are presented to demonstrate the effectiveness of the present model for the designing of valveless micropumps.
The flow-directing properties of several micromachined diffuser elements with different lengths and opening angles for valve-less micropumps have been investigated. The experimental results are compared with analytical results. The diffuser elements are fabricated in silicon and glass using isotropic and anisotropic wet etching and anodic bonding. The lengths of the diffusers are from 1.45 to 3.95 mm and the half-elliptic neck cross sections are about 30 μm × 100 μm.