Engineering Islets for Improved Performance by Optimized Reaggregation in a Micromold

Harnessing Human Pluripotent Stem Cell-Derived Pancreatic In Vitro Models for High-Throughput Toxicity Testing and Diabetes Drug Discovery

The long-standing goals in diabetes research are to improve β-cell survival, functionality and increase β-cell mass. Current strategies to manage diabetes progression are still not ideal for sustained maintenance of normoglycemia, thereby increasing demand for the development of novel drugs. Available pancreatic cell lines, cadaveric islets, and their culture methods and formats, either 2D or 3D, allow for multiple avenues of experimental design to address diverse aims in the research setting. More specifically, these pancreatic cells have been employed in toxicity testing, diabetes drug screens, and with careful curation, can be optimized for use in efficient high-throughput screenings (HTS). This has since spearheaded the understanding of disease progression and related mechanisms, as well as the discovery of potential drug candidates which could be the cornerstone for diabetes treatment. This book chapter will touch on the pros and cons of the most widely used pancreatic cells, including the more recent human pluripotent stem cell-derived pancreatic cells, and HTS strategies (cell models, design, readouts) that can be used for the purpose of toxicity testing and diabetes drug discovery.

A predictive computational platform for optimizing the design of bioartificial pancreas devices

The delivery of encapsulated islets or stem cell-derived insulin-producing cells (i.e., bioartificial pancreas devices) may achieve a functional cure for type 1 diabetes, but their efficacy is limited by mass transport constraints. Modeling such constraints is thus desirable, but previous efforts invoke simplifications which limit the utility of their insights. Herein, we present a computational platform for investigating the therapeutic capacity of generic and user-programmable bioartificial pancreas devices, which accounts for highly influential stochastic properties including the size distribution and random localization of the cells. We first apply the platform in a study which finds that endogenous islet size distribution variance significantly influences device potency. Then we pursue optimizations, determining ideal device structures and estimates of the curative cell dose. Finally, we propose a new, device-specific islet equivalence conversion table, and develop a surrogate machine learning model, hosted on a web application, to rapidly produce these coefficients for user-defined devices.

PEGDA microencapsulated allogeneic islets reverse canine diabetes without immunosuppression

Background

Protection of islets without systemic immunosuppression has been a long-sought goal in the islet transplant field. We conducted a pilot biocompatibility/safety study in healthy dogs followed by a dose-finding efficacy study in diabetic dogs using polyethylene glycol diacrylate (PEGDA) microencapsulated allogeneic canine islets.

Methods

Prior to the transplants, characterization of the canine islets included the calculations determining the average cell number/islet equivalent. Following measurements of purity, insulin secretion, and insulin, DNA and ATP content, the islets were encapsulated and transplanted interperitoneally into dogs via a catheter, which predominantly attached to the omentum. In the healthy dogs, half of the microspheres injected contained canine islets, the other half of the omentum received empty PEGDA microspheres.

Results

In the biocompatibility study, healthy dogs received increasing doses of cells up to 1.7 M cells/kg body weight, yet no hypoglycemic events were recorded and the dogs presented with no adverse events. At necropsy the microspheres were identified and described as clear with attachment to the omentum. Several of the blood chemistry values that were abnormal prior to the transplants normalized after the transplant. The same observation was made for the diabetic dogs that received higher doses of canine islets. In all diabetic dogs, the insulin required to attempt to control blood glucose was cut by 50–100% after the transplant, down to no required insulin for the course of the 60-day study. The dogs had no adverse events and behavioral monitoring suggested normal activity after recovery from the transplant.

Conclusions and implications

The study provides evidence that PEGDA microencapsulated canine islets reversed the signs of diabetes without immunosuppression and led to states of insulin-independence or significantly lowered insulin requirements in the recipients.

Cryopreservation and post-thaw characterization of dissociated human islet cells

The objective of this study is to optimize the cryopreservation of dissociated islet cells and obtain functional cells that can be used in single-cell transcriptome studies on the pathology and treatment of diabetes. Using an iterative graded freezing approach we obtained viable cells after cooling in 10% dimethyl sulfoxide and 6% hydroxyethyl starch at 1°C/min to -40°C, storage in liquid nitrogen, rapid thaw, and removal of cryoprotectants by serial dilution. The expression of epithelial cell adhesion molecule declined immediately after thaw, but recovered after overnight incubation, while that of an endocrine cell marker (HPi2) remained high after cryopreservation. Patch-clamp electrophysiology revealed differences in channel activities and exocytosis of various islet cell types; however, exocytotic responses, and the biophysical properties of voltage-gated Na+ and Ca2+ channels, are sustained after cryopreservation. Single-cell RNA sequencing indicates that overall transcriptome and crucial exocytosis genes are comparable between fresh and cryopreserved dispersed human islet cells. Thus, we report an optimized procedure for cryopreserving dispersed islet cells that maintained their membrane integrity, along with their molecular and functional phenotypes. Our findings will not only provide a ready source of cells for investigating cellular mechanisms in diabetes but also for bio-engineering pseudo-islets and islet sheets for modeling studies and potential transplant applications.

Comprehensive Development in Organ-On-A-Chip Technology

The expeditious advancement in the organ on chip technology provided a phase change to the conventional in vitro tests used to evaluate absorption, distribution, metabolism, excretion (ADME) studies and toxicity assessments. The demand for an accurate predictive model for assessing toxicity and reducing the potential risk factors became the prime area of any drug delivery process. Researchers around the globe are welcoming the incorporation of organ-on-a-chips for ADME and toxicity evaluation. Organ-on-a-chip (OOC) is an interdisciplinary technology that evolved as a contemporary in vitro model for the pharmacokinetics and pharmacodynamics (PK-PD) studies of a proposed drug candidate in the pre-clinical phases of drug development. The OOC provides a platform that mimics the physiological functions occurring in the human body. The precise flow control systems and the rapid sample processing makes OOC more advanced than the conventional two-dimensional (2D) culture systems. The integration of various organs as in the multi organs-on-a-chip provides more significant ideas about the time and dose dependant effects occurring in the body when a new drug molecule is administered as part of the pre-clinical times. This review outlines the comprehensive development in the organ-on-a-chip technology, various OOC models and its drug development applications, toxicity evaluation and efficacy studies.

Fabrication of functional rat pseudo-islets after cryopreservation of pancreatic islets or dispersed islet cells

Dispersed single cells from pancreatic islets can configure the three-dimensional islet-like architecture (pseudo-islets) with insulin secretion potential and controllable size through their aggregation property. The present study was designed to investigate whether cryopreservation of islets or islet cells can contribute to the efficient pseudo-islet fabrication in the rat model. In control group (CT), islet single cells were prepared by trypsin digestion of 50-400-µm ø fresh control islets, and then cultured for 3 days in the U-bottom microwell to fabricate pseudo-islets. In vitrification-warming group (VW), islet single cells were prepared from postwarm islets cryopreserved by vitrification on nylon mesh device, and then cultured for 3 days. In freezing group (FR), islet single cells originated from fresh islets were subjected to a conventional Bicell® freezing, and postthaw cells were cultured for 3 days. To generate 1 islet equivalent pseudo-islets (150 µm ø) by the sphere culture, 1250 CT cells, 1250 VW cells, and 1500 FR cells were seeded to each microwell. The viability of the pseudo-islets was comparable among the three groups (93.9%-96.9%). Furthermore, the insulin secretion assay showed that those pseudo-islets responded sufficiently to the high glucose stimulation. Immunostaining for insulin and glucagon showed that the endocrine cell arrangement of those pseudo-islets is similar to that of native and isolated islets. These islets/pseudo-islets had the β-cells in core and the α-cells in mantle, which was typical characteristic of the rodent islets. However, some clusters of α-cells were observed inside the FR pseudo-islets. Interestingly, the VW pseudo-islets had significantly fewer α-cells than the CT or FR pseudo-islets. These results suggest that the sphere culture of islet cells is useful tool to generate the pseudo-islets with the customized size and normal functionality, even after islet cryopreservation.

A 3D culture platform enables development of zinc-binding prodrugs for targeted proliferation of β cells

Advances in treating β cell loss include islet replacement therapies or increasing cell proliferation rate in type 1 and type 2 diabetes, respectively. We propose developing multiple proliferation-inducing prodrugs that target high concentration of zinc ions in β cells. Unfortunately, typical two-dimensional (2D) cell cultures do not mimic in vivo conditions, displaying a markedly lowered zinc content, while 3D culture systems are laborious and expensive. Therefore, we developed the Disque Platform (DP)-a high-fidelity culture system where stem cell-derived β cells are reaggregated into thin, 3D discs within 2D 96-well plates. We validated the DP against standard 2D and 3D cultures and interrogated our zinc-activated prodrugs, which release their cargo upon zinc chelation-so preferentially in β cells. Through developing a reliable screening platform that bridges the advantages of 2D and 3D culture systems, we identified an effective hit that exhibits 2.4-fold increase in β cell proliferation compared to harmine.

From infection to healing: The use of plant viruses in bioactive hydrogels

Plant viruses show great diversity in shape and size, but each species forms unique nucleoprotein particles that are symmetrical and monodisperse. The genetically programed structure of plant viruses allows them to be modified by genetic engineering, bioconjugation, or encapsulation to form virus nanoparticles (VNPs) that are suitable for a broad range of applications. Plant VNPs can be used to present foreign proteins or epitopes, to construct inorganic hybrid materials, or to carry molecular cargos, allowing their utilization as imaging reagents, immunomodulators, therapeutics, nanoreactors, and biosensors. The medical applications of plant viruses benefit from their inability to infect and replicate in human cells. The structural properties of plant viruses also make them useful as components of hydrogels for tissue engineering. Hydrogels are three-dimensional networks composed of hydrophilic polymers that can absorb large amounts of water. They are used as supports for tissue regeneration, as reservoirs for controlled drug release, and are found in contact lenses, many wound healing materials, and hygiene products. They are also useful in ecological applications such as wastewater treatment. Hydrogel-based matrices are structurally similar to the native extracellular matrix (ECM) and provide a scaffold for the attachment of cells. To fully replicate the functions of the ECM it is necessary to augment hydrogels with biological cues that regulate cellular interactions. This can be achieved by incorporating functionalized VNPs displaying ligands that influence the mechanical characteristics of hydrogels and their biological properties, promoting the survival, proliferation, migration, and differentiation of embedded cells. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

In vivo-mimicking microfluidic perfusion culture of pancreatic islet spheroids

Native pancreatic islets interact with neighboring cells by establishing three-dimensional (3D) structures, and are surrounded by perfusion at an interstitial flow level. However, flow effects are generally ignored in islet culture models, although cell perfusion is known to improve the cell microenvironment and to mimic in vivo physiology better than static culture systems. Here, we have developed functional islet spheroids using a microfluidic chip that mimics interstitial flow conditions with reduced shear cell damage. Dynamic culture, compared to static culture, enhanced islet health and maintenance of islet endothelial cells, reconstituting the main component of islet extracellular matrix within spheroids. Optimized flow condition allowed localization of secreted soluble factors near spheroids, facilitating diffusion-mediated paracrine interactions within islets, and enabled long-term maintenance of islet morphology and function for a month. The proposed model can aid islet preconditioning before transplantation and has potential applications as an in vitro model for diabetic drug testing.

Microencapsulated islet-like microtissues with toroid geometry for enhanced cellular viability

Transplantation of immuno-isolated islets is a promising strategy to restore insulin-secreting function in patients with Type 1 diabetes. However, the clinical translation of this treatment approach remains elusive due to the loss of islet viability resulting from hypoxia at the avascular transplantation site. To address this challenge, we designed non-spherical islet-like microtissues and investigated the effect of their geometries on cellular viability. Insulin-secreting microtissues with different shapes were fabricated by assembly of monodispersed rat insulinoma beta cells on micromolded nonadhesive hydrogels. Our study quantitatively demonstrated that toroid microtissues exhibited enhanced cellular viability and metabolic activity compared to rod and spheroid microtissues with the same volume. At a similar level of cellular viability, toroid geometry facilitated efficient packing of more cells into each microtissue than rod and spheroid geometries. In addition, toroid microtissues maintained the characteristic glucose-responsive insulin secretion of rat insulinoma beta cells. Furthermore, toroid microtissues preserved their geometry and structural integrity following their microencapsulation in immuno-isolatory alginate hydrogel. Our study suggests that adopting toroid geometry in designing therapeutic microtissues potentially reduces mass loss of cellular grafts and thereby may improve the performance of transplanted islets towards a clinically viable cure for Type 1 diabetes. STATEMENT OF SIGNIFICANCE: Transplantation of therapeutic cells is a promising strategy for the treatment of a wide range of hormone or protein-deficiency diseases. However, the clinical application of this approach is hindered by the loss of cell viability and function at the avascular transplantation site. To address this challenge, we fabricated hydrogel-encapsulated islet-like microtissues with non-spheroidal geometry and optimal surface-to-volume ratio. This study demonstrated that the viability of therapeutic cells can be significantly increased solely by redesigning the microtissue configuration without requiring any additional biochemical or operational accessories. This study suggests that the adoption of toroid geometry provides a possible avenue to improve the long-term survival of transplanted therapeutic cells and expedite the translation of cell-based therapy towards clinical application.

Integrated Microphysiological Systems: Transferable Organ Models and Recirculating Flow

Studying and understanding of tissue and disease mechanisms largely depend on the availability of suitable and representative biological model systems. These model systems should be carefully engineered and faithfully reproduce the biological system of interest to understand physiological effects, pharmacokinetics, and toxicity to better identify new drug compounds. By relying on microfluidics, microphysiological systems (MPSs) enable the precise control of culturing conditions and connections of advanced in vitro 3D organ models that better reproduce in vivo environments. This review focuses on transferable in vitro organ models and integrated MPSs that host these transferable biological units and enable interactions between different tissue types. Interchangeable and transferrable in vitro organ models allow for independent quality control of the biological model before system assembly and building MPS assays on demand. Due to the complexity and different maturation times of individual in vitro tissues, off-chip production and quality control entail improved stability and reproducibility of the systems and results, which is important for large-scale adoption of the technology. Lastly, the technical and biological challenges and open issues for realizing and implementing integrated MPSs with transferable in vitro organ models are discussed.

Stem-cell based organ-on-a-chip models for diabetes research

Diabetes mellitus (DM) ranks among the severest global health concerns of the 21st century. It encompasses a group of chronic disorders characterized by a dysregulated glucose metabolism, which arises as a consequence of progressive autoimmune destruction of pancreatic beta-cells (type 1 DM), or as a result of beta-cell dysfunction combined with systemic insulin resistance (type 2 DM). Human cohort studies have provided evidence of genetic and environmental contributions to DM; yet, these studies are mostly restricted to investigating statistical correlations between DM and certain risk factors. Mechanistic studies, on the other hand, aimed at re-creating the clinical picture of human DM in animal models. A translation to human biology is, however, often inadequate owing to significant differences between animal and human physiology, including the species-specific glucose regulation. Thus, there is an urgent need for the development of advanced human in vitro models with the potential to identify novel treatment options for DM. This review provides an overview of the technological advances in research on DM-relevant stem cells and their integration into microphysiological environments as provided by the organ-on-a-chip technology.

Integration of mesenchymal stem cells into islet cell spheroids improves long-term viability, but not islet function

Pancreatic islets, especially the large islets (> 150µm in diameter) have poor survival rates in culture. Co-culturing with mesenchymal stem cells (MSCs) has been shown to improve islet survival and function. However, most co-culture studies have been comprised of MSC surrounding islets in the media. The purpose of this study was to determine whether islet survival and function was improved when the 2 populations of cells were intermingled with each other in a defined geometry. Hybrid spheroids containing 25, 50 or 75 or 90% islets cells with appropriate numbers of MSCs were created along with spheroids comprised of only islet cells or only MSCs. Spheroids were tested for yield, viability, diameter, cellular composition, and glucose-stimulated insulin secretion. The 25% islet/75% MSC group created the fewest spheroids, with the poorest survival and insulin secretion and the largest diameter. The remaining groups were highly viable with average diameters under 80µm at formation. However, the hybrid spheroid groups preferred to cluster in islet-only spheroids. The 50, 75 and 90% islet cell groups had excellent long-term survival with 90-95% viability at 2 weeks in culture, compared with the islet only group that were below 80% viability. The glucose-stimulated insulin secretion was not statistically different for the 50, 75, or 90 groups when exposed to 2.4, 16.8, or 22.4 mM glucose. Only the spheroids with 25% islet cells had a statistically lower levels of insulin release, and the 100% had statistically higher levels at 22.4 mM glucose and in response to secretagogue. Thus, imbedded co-culture improved long-term viability, but failed to enhance glucose-stimulated insulin secretion in vitro.

Improved yield of canine islet isolation from deceased donors

BACKGROUND

Canine diabetes is a strikingly prevalent and growing disease, and yet the standard treatment of a twice-daily insulin injection is both cumbersome to pet owners and only moderately effective. Islet transplantation has been performed with repeated success in canine research models, but has unfortunately not been made available to companion animals. Standard protocols for islet isolation, developed primarily for human islet transplantation, include beating-heart organ donation, vascular perfusion of preservation solutions, specialized equipment. Unfortunately, these processes are prohibitively complex and expensive for veterinary use. The aim of the study was to develop a simplified approach for isolating canine islets that is compatible with the financial and logistical restrictions inherent to veterinary medicine for the purpose of translating islet transplantation to a clinical treatment for canine diabetes.

RESULTS

Here, we describe simplified strategies for isolating quality islets from deceased canine donors without vascular preservation and with up to 90 min of cold ischemia time. An average of more than 1500 islet equivalents per kg of donor bodyweight was obtained with a purity of 70% (N = 6 animals). Islets were 95% viable and responsive to glucose stimulation for a week. We found that processing only the body and tail of the pancreas increased isolation efficiency without sacrificing islet total yield. Islet yield per gram of tissue increased from 773 to 1868 islet equivalents when the head of the pancreas was discarded (N = 3/group).

CONCLUSIONS

In summary, this study resulted in the development of an efficient and readily accessible method for obtaining viable and functional canine islets from deceased donors. These strategies provide an ethical means for obtaining donor islets.

Long-term cryopreservation of reaggregated pancreatic islets resulting in successful transplantation in rats

Preservation of pancreatic islets for long-term storage of islets used for transplantation or research has long been a goal. Unfortunately, few studies on long-term islet cryopreservation (1 month and longer) have reported positive outcomes in terms of islet yield, survival and function. In general, single cells have been shown to tolerate the cryopreservation procedure better than tissues/multicellular structures like islets. Thus, we optimized a method to cryopreserve single islet cells and, after thawing, reaggregated them into islet spheroids. Cryopreserved (CP) single human islet cells formed spheroids efficiently within 3-5 days after thawing. Approximately 79% of islet cells were recovered following the single-cell cryopreservation protocol. Viability after long-term cryopreservation (4 weeks or more) was significantly higher in the CP islet cell spheroids (97.4 ± 0.4%) compared to CP native islets (14.6 ± 0.4%). Moreover, CP islet cell spheroids had excellent viability even after weeks in culture (88.5 ± 1.6%). Metabolic activity was 4-5 times higher in CP islet cell spheroids than CP native islets at 24 and 48 h after thawing. Diabetic rats transplanted with CP islet cell spheroids were normoglycemic for 10 months, identical to diabetic rats transplanted with fresh islets. However, the animals receiving fresh islets required a higher volume of transplanted tissue to achieve normoglycemia compared to those transplanted with CP islet cell spheroids. By cryopreserving single cells instead of intact islets, we achieved highly viable and functional islets after thawing that required lower tissue volumes to reverse diabetes in rats.

Engineering islet for improved performance by optimized reaggregation in alginate gel beads

After islet isolation, diffusion has become the main mechanism to transport oxygen and nutrients into the core of islets. However, diffusion has limitations, by which nutrients cannot effectively reach the core of large islets and can eventually cause core cell death and islet loss. This problem can be resolved by dispersing islets into single islet cells, but single islet cells do not exhibit insulin release function in in vitro culture. In this study, we intended to establish a new islet engineering approach by forming islet cell clusters to improve islet survival and function. Therefore, alginate gels were used to encapsulate islet cells to form artificial islets after dispersion of islets into single cells. The shape of the islet cell clusters was similar to native islets, and the size of the islet cell clusters was limited to a maximum diameter of 100 μm. By limiting the diameter of this engineered islet cell cluster, cell viability was nearly 100%, a significant improvement over natural islets. Importantly, islet cell clusters express the genes of islets, including Isl-1, Gcg, and insulin-1, and insulin secretion ability was maintained in vitro.

An Automated Multiplexed Hepatotoxicity and CYP Induction Assay Using HepaRG Cells in 2D and 3D

Drug-induced liver injury (DILI) and drug-drug interactions (DDIs) are concerns when developing safe and efficacious compounds. We have developed an automated multiplex assay to detect hepatotoxicity (i.e., ATP depletion) and metabolism (i.e., cytochrome P450 1A [CYP1A] and cytochrome P450 3A4 [CYP3A4] enzyme activity) in two-dimensional (2D) and three-dimensional (3D) cell cultures. HepaRG cells were cultured in our proprietary micromold plates and produced spheroids. HepaRG cells, in 2D or 3D, expressed liver-specific proteins throughout the culture period, although 3D cultures consistently exhibited higher albumin secretion and CYP1A/CYP3A4 enzyme activity than 2D cultures. Once the spheroid hepatic quality was assessed, 2D and 3D HepaRGs were challenged to a panel of DILI- and CYP-inducing compounds for 7 days. The 3D HepaRG model had a 70% sensitivity to liver toxins at 7 days, while the 2D model had a 60% sensitivity. In both the 2D and 3D HepaRG models, 83% of compounds were predicted to be CYP inducers after 7 days of compound exposure. Combined, our results demonstrate that an automated multiplexed liver spheroid system is a promising cell-based method to evaluate DILI and DDI for early-stage drug discovery.

Hyaluronic Acid/Collagen Hydrogel as an Alternative to Alginate for Long-Term Immunoprotected Islet Transplantation<sup/>

Alginate has long been the material of choice for immunoprotection of islets due to its low cost and ability to easily form microspheres. Unfortunately, this seaweed-derived material is notoriously prone to fibrotic overgrowth in vivo, resulting in premature graft failure. The purpose of this study was to test an alternative, hyaluronic acid (HA-COL), for in vitro function, viability, and allogeneic islet transplant outcomes in diabetic rats. In vitro studies indicated that the HA-COL gel had diffusion characteristics that would allow small molecules such as glucose and insulin to enter and exit the gel, whereas larger molecules (70 and 500 kDa dextrans) were impeded from diffusing past the gel edge in 24 h. Islets encapsulated in HA-COL hydrogel showed significantly improved in vitro viability over unencapsulated islets and retained their morphology and glucose sensitivity for 28 days. When unencapsulated allogeneic islet transplants were administered to the omentum of outbred rats, they initially were normoglycemic, but by 11 days returned to hyperglycemia. Immunohistological examination of the grafts and surrounding tissue indicated strong graft rejection. By comparison, when using the same outbred strain of rats, allogeneic transplantation of islets within the HA-COL gel reversed long-term diabetes and prevented graft rejection in all animals. Animals were sacrificed at 40, 52, 64, and 80 weeks for evaluation, and all were non-diabetic at sacrifice. Explanted grafts revealed viable islets in the transplant site as well as intact hydrogel, with little or no evidence of fibrotic overgrowth or cellular rejection. The results of these studies demonstrate great potential for HA-COL hydrogel as an alternative to sodium alginate for long-term immunoprotected islet transplantation.

Arum Palaestinum with isovanillin, linolenic acid and β-sitosterol inhibits prostate cancer spheroids and reduces the growth rate of prostate tumors in mice

BACKGROUND

Arum palaestinum is a plant commonly found in the Middle East that is ingested as an herbal remedy to fight cancer. However, no studies have examined the direct effect of the plant/plant extract on tumor growth in an animal model.

METHODS

Verified prostate cancer cells were plated as 3D spheroids to determine the effect of extract from boiled Arum Palaestinum Boiss roots. In addition, male NU/NU mice (8 weeks old) with xenograft tumors derived from the prostate cancer cell line were treated daily with 1000 mg/kg body weight gavage of the suspension GZ17. The tumor growth was measured repeatedly with calipers and the excised tumors were weighed at the termination of the 3 week study. Control mice (10 mice in each group) received vehicle in the same manner and volume.

RESULTS

The number of live prostate cancer cells declined in a dose/dependent manner with a 24 h exposure to the extract at doses of 0.015 to 6.25 mg/mL. A fortified version of the extract (referred to as GZ17) that contained higher levels of isovanillin, linolenic acid and β-sitosterol had a stronger effect on the cell death rate, shifting the percentage of dead cells from 30 % to 55 % at the highest dose while the vehicle control had no effect on cell numbers. When GZ17 was applied to non-cancer tissue, in this case, human islets, there was no cell death at doses that were toxic to treated cancer cells. Preliminary toxicity studies were conducted on rats using an up-down design, with no signs of toxic effect at the highest dose. NU/NU mice with xenograft prostate tumors treated with GZ17 had a dramatic inhibition of tumor progression, while tumors in the control group grew steadily through the 3 weeks. The rate of tumor volume increase was 73 mm(3)/day for the vehicle group and 24 mm(3)/day for the GZ17 treated mice. While there was a trend towards lower excised tumor weight at study termination in the GZ17 treatment group, there was no statistical difference.

CONCLUSIONS

Fortified Arum palaestinum Boiss caused a reduction in live cells within prostate cancer spheroids and blocked tumor growth in xenografted prostate tumors in mice without signs of toxicity.

Development of large-scale size-controlled adult pancreatic progenitor cell clusters by an inkjet-printing technique

The generation of transplantable β-cells from pancreatic progenitor cells (PPCs) could serve as an ideal cell-based therapy for diabetes. Because the transplant efficiency depends on the size of islet-like clusters, it becomes one of the key research topics to produce PPCs with controlled cluster sizes in a scalable manner. In this study, we used inkjet printing to pattern biogenic nanoparticles, i.e., mutant tobacco mosaic virus (TMV), with different spot sizes to support the formation of multicellular clusters by PPCs. We successfully achieved TMV particle patterns with variable features and sizes by adjusting the surface wettability and printing speed. The spot sizes of cell-adhesive TMV mutant arrays were in the range of 50-150 μm diameter. Mouse PPCs were seeded on the TMV-RGD (arginine-glycine-aspartate)-patterned polystyrene (PS) substrate, which consists of areas that either favor (TMV-RGD) or prohibit (bare PS) cell adhesion. The PPCs stably attached, proliferated on top of the TMV-RGD support, thus resulting in the formation of uniform and confluent PPC clusters. Furthermore, the aggregated PPCs also maintained their multipotency and were positive for E-cadherin, indicating that the formation of cell-cell junctions is critical for enhanced cell-cell contact.

Controlled aggregation of primary human pancreatic islet cells leads to glucose-responsive pseudoislets comparable to native islets

Clinical islet transplantation is a promising treatment for patients with type 1 diabetes. However, pancreatic islets vary in size and shape affecting their survival and function after transplantation because of mass transport limitations. To reduce diffusion restrictions and improve islet cell survival, the generation of islets with optimal dimensions by dispersion followed by reassembly of islet cells, can help limit the length of diffusion pathways. This study describes a microwell platform that supports the controlled and reproducible production of three-dimensional pancreatic cell clusters of human donor islets. We observed that primary human islet cell aggregates with a diameter of 100-150 μm consisting of about 1000 cells best resembled intact pancreatic islets as they showed low apoptotic cell death (<2%), comparable glucose-responsiveness and increasing PDX1, MAFA and INSULIN gene expression with increasing aggregate size. The re-associated human islet cells showed an a-typical core shell configuration with beta cells predominantly on the outside unlike human islets, which became more randomized after implantation similar to native human islets. After transplantation of these islet cell aggregates under the kidney capsule of immunodeficient mice, human C-peptide was detected in the serum indicating that beta cells retained their endocrine function similar to human islets. The agarose microwell platform was shown to be an easy and very reproducible method to aggregate pancreatic islet cells with high accuracy providing a reliable tool to study cell-cell interactions between insuloma and/or primary islet cells.

Assessment of re-aggregated human pancreatic islets for secondary drug screening

BACKGROUND AND PURPOSE

Insulin secretion from isolated pancreatic islets is a pivotal assay in developing novel insulin secretagogues, given its good correlation with in vivo efficacy. Because the supply of human islets is limited, this assay is typically run with rodent islets, which do not address species differences and are low-throughput, because of the size matching or volume normalization required. Here we have evaluated the suitability of human re-aggregated islets for this assay.

EXPERIMENTAL APPROACH

We generated re-aggregated human islets of a consistent size, using micromolds and compared their responses with those of native human and rat islets, to known secretagogues and inhibitors of insulin release.

KEY RESULTS

Insulin secretion from rat islets, human islets and human re-aggregated cell clusters was concentration-dependently increased by glucose. The calcium channel agonist, Bay K 8644, stimulated insulin secretion in native rat islets and human re-aggregated islets, but not native human islets. Glibenclamide and tolbutamide were more effective and potent in re-aggregated human clusters compared with the other two preparations. Rat islets outperformed both human preparations of islets in response to caffeine, carbachol and glucagon-like peptide-1. Re-aggregated human islet clusters were more sensitive to somatostatin, diazoxide and sodium azide, but rodent islets were more sensitive to nifedipine.

CONCLUSIONS AND IMPLICATIONS

Human re-aggregated clusters of islet cells, of a constant size were more responsive to all compounds tested than native human islets. Importantly, the assay variability was less in the re-aggregated cluster preparations, which suggests that such re-aggregated cells could be useful for drug development.

The preservation of islet with alginate encapsulation in the process of transportation

Restoration of insulin secretion by transplantation of isolated islets is a treatment for type Ι diabetes mellitus. One of the major issues with clinical treatment of islet transplantation is how to maintain islet viability during transportation from the donor to the patient. We developed a method that uses alginate encapsulation to protect islets from mechanical damage during shipment. We tested several variables for their impact on islet viability during transportation and used the significant variable to build a response surface methodology (RSM) model by the Box-Behnken design method. This type of model is a mathematical and statistical technique that we used to optimize the conditions for islet viability during shipment. In this study, the factors that significantly affected islet survival rate were incubation time, serum concentration, and preservation time. Then, an empirical model was built to optimize conditions of the islets for shipping according to the responses of the effect factors with RSM. This model can be used to predict the islet survival rate and can serve as a guide for optimizing the transportation method of islets and increasing the success rate of the transplant procedure.

Improved physiological properties of gravity-enforced reassembled rat and human pancreatic pseudo-islets

Previously we demonstrated the superiority of small islets vs large islets in terms of function and survival after transplantation, and we generated reaggregated rat islets (pseudo-islets) of standardized small dimensions by the hanging-drop culture method (HDCM). The aim of this study was to generate human pseudo-islets by HDCM and to evaluate and compare the physiological properties of rat and human pseudo-islets. Isolated rat and human islets were dissociated into single cells and incubated for 6-14 days by HDCM. Newly formed pseudo-islets were analysed for dimensions, morphology, glucose-stimulated insulin secretion (GSIS) and total insulin content. The morphology of reaggregated human islets was similar to that of native islets, while rat pseudo-islets had a reduced content of α and δ cells. GSIS of small rat and human pseudo-islets (250 cells) was increased up to 4.0-fold (p < 0.01) and 2.5-fold (p < 0.001), respectively, when compared to their native counterparts. Human pseudo-islets showed a more pronounced first-phase insulin secretion as compared to intact islets. GSIS was inversely correlated to islet size, and small islets (250 cells) contained up to six-fold more insulin/cell than large islets (1500 cells). Tissue loss with this new technology could be reduced to 49.2 ± 1.5% in rat islets, as compared to the starting amount. With HDCM, pseudo-islets of standardized size with similar cellular composition and improved biological function can be generated, which compensates for tissue loss during production. Transplantation of small pseudo-islets may represent an attractive strategy to improve graft survival and function, due to better oxygen and nutrient supply during the phase of revascularization. Copyright © 2014 John Wiley & Sons, Ltd.

Microchip-based engineering of super-pancreatic islets supported by adipose-derived stem cells

Type 1 diabetes mellitus (T1DM) is a chronic disorder characterized by targeted autoimmune-mediated destruction of the β cells of Langerhans within pancreatic islets. Currently, islet transplantation is the only curative therapy; however, donor shortages and cellular damage during the isolation process critically limit the use of this approach. Here, we describe a method for creating viable and functionally potent islets for successful transplantation by co-culturing single primary islet cells with adipose-derived stem cells (ADSCs) in concave microwells. We observed that the ADSCs segregated from the islet cells, eventually yielding purified islet spheroids in the three-dimensional environment. Thereafter, the ADSC-exposed islet spheroids showed significantly different ultrastructural morphologies, higher viability, and enhanced insulin secretion compared to mono-cultured islet spheroids. This suggests that ADSCs may have a significant potential to protect islet cells from damage during culture, and may be employed to improve islet cell survival and function prior to transplantation. In vivo experiments involving xenotransplantation of microfiber-encapsulated spheroids into a mouse model of diabetes revealed that co-culture-transplanted mice maintained their blood glucose levels longer than mono-culture-transplanted mice, and required less islet mass to reverse diabetes. This method for culturing islet spheroids could potentially help overcome the cell shortages that have limited clinical applications and could possibly be developed into a bioartificial pancreas.