Cell transplantation for endocrine disorders

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Hypoparathyroidism: State of the Art on Cell and Tissue Therapies

Hypoparathyroidism is an endocrine disorder characterized by low serum calcium levels, high serum phosphorus levels, and by inappropriate or absent secretion of the parathyroid hormone (PTH). The most common therapeutic strategy to treat this condition is hormone replacement therapy with calcium and vitamin D but, unfortunately, in the long term this treatment may not be sufficient to compensate for the loss of endocrine function. Glandular autotransplantation is considered the most effective technique in place of replacement therapy. Although it leads to excellent results in most cases, autotransplantation is not always possible. Allograft is a good way to treat patients who have not been able to undergo autograft, but this technique has limited success due to side effects related to tissue rejection. This therapy is supported by systemic immunosuppression, which leads to the onset of serious side effects in patients, with a risk of endocrine toxicity. Today, research on endocrine disorders is focused on discovering alternative graft therapies that can allow optimal results with the fewest possible side effects. In this review, we will make an update on the current state of the art about the cell and tissue therapy as treatment for hypoparathyroidism, to identify which type of therapeutic strategy could be valid for a future clinical use.

Applications of Biopolymers for Drugs and Probiotics Delivery

Research regarding the use of biopolymers has been of great interest to scientists, the medical community, and the industry especially in recent years. Initially used for food applications, the special properties extended their use to the pharmaceutical and medical industries. The practical applications of natural drug encapsulation materials have emerged as a result of the benefits of the use of biopolymers as edible coatings and films in the food industry. This review highlights the use of polysaccharides in the pharmaceutical industries and as encapsulation materials for controlled drug delivery systems including probiotics, focusing on their development, various applications, and benefits. The paper provides evidence in support of research studying the use of biopolymers in the development of new drug delivery systems, explores the challenges and limitations in integrating polymer-derived materials with product delivery optimization, and examines the host biological/metabolic parameters that can be used in the development of new applications.

An inverse-breathing encapsulation system for cell delivery

Cell encapsulation represents a promising therapeutic strategy for many hormone-deficient diseases such as type 1 diabetes (T1D). However, adequate oxygenation of the encapsulated cells remains a challenge, especially in the poorly oxygenated subcutaneous site. Here, we present an encapsulation system that generates oxygen (O2) for the cells from their own waste product, carbon dioxide (CO2), in a self-regulated (i.e., "inverse breathing") way. We leveraged a gas-solid (CO2-lithium peroxide) reaction that was completely separated from the aqueous cellular environment by a gas permeable membrane. O2 measurements and imaging validated CO2-responsive O2 release, which improved cell survival in hypoxic conditions. Simulation-guided optimization yielded a device that restored normoglycemia of immunocompetent diabetic mice for over 3 months. Furthermore, functional islets were observed in scaled-up device implants in minipigs retrieved after 2 months. This inverse breathing device provides a potential system to support long-term cell function in the clinically attractive subcutaneous site.

An Atmosphere-Breathing Refillable Biphasic Device for Cell Replacement Therapy

Cell replacement therapy is emerging as a promising treatment platform for many endocrine disorders and hormone deficiency diseases. The survival of cells within delivery devices is, however, often limited due to low oxygen levels in common transplantation sites. Additionally, replacing implanted devices at the end of the graft lifetime is often unfeasible and, where possible, generally requires invasive surgical procedures. Here, the design and testing of a modular transcutaneous biphasic (BP) cell delivery device that provides enhanced and unlimited oxygen supply by direct contact with the atmosphere is presented. Critically, the cell delivery unit is demountable from the fixed components of the device, allowing for surgery-free refilling of the therapeutic cells. Mass transfer studies show significantly improved performance of the BP device in comparison to subcutaneous controls. The device is also tested for islet encapsulation in an immunocompetent diabetes rodent model. Robust cell survival and diabetes correction is observed following a rat-to-mouse xenograft. Lastly, nonsurgical cell refilling is demonstrated in dogs. These studies show the feasibility of this novel device for cell replacement therapies.

Fresh tissue parathyroid allotransplantation with short-term immunosuppression: 1-year follow-up

BACKGROUND

Permanent hypoparathyroidism is a serious problem and requires medications indefinitely. Parathyroid allotransplantation (PA) with short-term immunosuppression is definitive choice but long-term results are not clear.

METHOD

We performed PA from two donors to two recipients. Both recipients were 39-year-old females. Donors were a 32-year-old female and a 36-year-old male, who both have chronic kidney disease. Routine tests, viral markers, and cross-matches were analyzed individually. The parathyroid glands were resected from the living donors, fragmented quickly in the operation room and injected into the left deltoid muscles of the two recipients.

RESULTS

Methylprednisolone was administered on post-PA day one and two. Recipients were discharged from the hospital without complications. Calcium and PTH levels were observed throughout 1 year. We did not observe any complications during the follow-up period. Medications ceased in post-transplantation week 1 for Case 1 and after 1 month for Case 2.

CONCLUSION

Fresh tissue PA with short-term immunosuppression appears to be a promising technique that is easy to perform, is cost-effective, has low risk of side effects and minimal complications with compatibility for HLA conditions. A longer follow-up period and more case studies are needed to determine the risks and benefits of this procedure for future cases.

Islet encapsulated implantable composite hollow fiber membrane based device: A bioartificial pancreas

Islets from xeno-sources and islet like clusters derived from autologus stem cells have emerged as alternatives to cadaveric pancreas used for treatment of type 1 diabetes. However, the immuno-isolation of these islets from the host immune system suffers from the issue of biocompatibility and hypoxia. To overcome the issues of immunobarrier biocompatibility, we developed a Polysulfone (Psf)/TPGS composite hollow fiber membrane (HFM) using a hollow fiber spinning pilot plant specially developed for this purpose. Important structural variables such as fiber material, dope composition, dimensions, surface characteristics etc., were precisely engineered and tuned for bioartificial pancreas application. The HFMs were characterized for their morphology, molecular diffusion, selectivity and protein absorption. The optimized Polysulfone(Psf)/TPGS composite HFMs, which contained TPGS, exhibited uniformed structure with low insulin adsorption and high permeability of insulin. The HFM was further studied for the encapsulation and in-vitro growth with porcine and differentiated islets isolated from human umbilical cord Wharton's jelly. To prove their efficacy under in-vivo conditions, the Polysulfone(Psf)/TPGS composite HFMs were encapsulated with either of these isolated cells (porcine islets or islet like cell clusters derived from mesenchymal stem cells isolated from human umbilical cord Wharton's jelly) and they were transplanted in experimental STZ induced diabetic mice. The results showed restoration of normoglycemia for 30days, indicating their ability to respond efficiently to high glucose without immune-rejection. Thus, these results indicate that Polysulfone (Psf)/TPGS composite HFMs can be used as an implantable, immune-competent bioartificial pancreas as a therapy for type 1 diabetes.

[Allogeneic parathyroid: 2-year follow-up]

BACKGROUND

Hypoparathyroidism is one of the most frequent complications of neck surgery. The treatment is currently medical; however this involves several complications secondary to high doses of calcium and vitamin D, thus making parathyroid allotransplantation a good management option.

MATERIAL AND METHODS

Patients with hypoparathyroidism were selected in the April-December period of 2011 in the general surgical clinic. They were between 16 and 65 years, and ingested high doses of calcium. The donors were patients with primary and secondary hyperparathyroidism, and the transplants were performed in relation to blood group and human leucocyte antigen.

RESULTS

Five parathyroid allografts were performed. All the patients had iatrogenic hypoparathyroidism, all women with a mean age of 49.8 years. The graft was implanted under local anaesthesia in the non-dominant forearm. Four of the patients are so far considered functional due to the increase in paratohormone, and demonstrating its function by scintigraphy with sestamibi. One of the patients showed no increase in paratohormone or imaging studies that demonstrate its functionality. After a two year follow up the graft remains functional but with with oral calcium intake at a lower dose than before transplantation. None of the patients had immunosuppression side effects.

CONCLUSIONS

In this study, allogeneic unrelated living parathyroid transplant with an immunosuppressive regimen of six months has proven to be a safe alternative treatment to improve quality of life by decreasing the excessive calcium intake and improving physical activity with adequate graft survival at 24 months follow up.

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.

Insulin-loaded hydroxyapatite combined with macrophage activity to deliver insulin for diabetes mellitus

InsHAP is engulfed by macrophages and the lysosome/endosome hybrid is broken down by osmosis, which facilitates delivery of insulin into the bloodstream.

Encapsulating non-human primate multipotent stromal cells in alginate via high voltage for cell-based therapies and cryopreservation

Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×10⁶ cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application.

Microfluidic conformal coating of non-spherical magnetic particles

We present the conformal coating of non-spherical magnetic particles in a co-laminar flow microfluidic system. Whereas in the previous reports spherical particles had been coated with thin films that formed spheres around the particles; in this article, we show the coating of non-spherical particles with coating layers that are approximately uniform in thickness. The novelty of our work is that while liquid-liquid interfacial tension tends to minimize the surface area of interfaces-for example, to form spherical droplets that encapsulate spherical particles-in our experiments, the thin film that coats non-spherical particles has a non-minimal interfacial area. We first make bullet-shaped magnetic microparticles using a stop-flow lithography method that was previously demonstrated. We then suspend the bullet-shaped microparticles in an aqueous solution and flow the particle suspension with a co-flow of a non-aqueous mixture. A magnetic field gradient from a permanent magnet pulls the microparticles in the transverse direction to the fluid flow, until the particles reach the interface between the immiscible fluids. We observe that upon crossing the oil-water interface, the microparticles become coated by a thin film of the aqueous fluid. When we increase the two-fluid interfacial tension by reducing surfactant concentration, we observe that the particles become trapped at the interface, and we use this observation to extract an approximate magnetic susceptibility of the manufactured non-spherical microparticles. Finally, using fluorescence imaging, we confirm the uniformity of the thin film coating along the entire curved surface of the bullet-shaped particles. To the best of our knowledge, this is the first demonstration of conformal coating of non-spherical particles using microfluidics.

Polymers in cell encapsulation from an enveloped cell perspective

In the past two decades, many polymers have been proposed for producing immunoprotective capsules. Examples include the natural polymers alginate, agarose, chitosan, cellulose, collagen, and xanthan and synthetic polymers poly(ethylene glycol), polyvinyl alcohol, polyurethane, poly(ether-sulfone), polypropylene, sodium polystyrene sulfate, and polyacrylate poly(acrylonitrile-sodium methallylsulfonate). The biocompatibility of these polymers is discussed in terms of tissue responses in both the host and matrix to accommodate the functional survival of the cells. Cells should grow and function in the polymer network as adequately as in their natural environment. This is critical when therapeutic cells from scarce cadaveric donors are considered, such as pancreatic islets. Additionally, the cell mass in capsules is discussed from the perspective of emerging new insights into the release of so-called danger-associated molecular pattern molecules by clumps of necrotic therapeutic cells. We conclude that despite two decades of intensive research, drawing conclusions about which polymer is most adequate for clinical application is still difficult. This is because of the lack of documentation on critical information, such as the composition of the polymer, the presence or absence of confounding factors that induce immune responses, toxicity to enveloped cells, and the permeability of the polymer network. Only alginate has been studied extensively and currently qualifies for application. This review also discusses critical issues that are not directly related to polymers and are not discussed in the other reviews in this issue, such as the functional performance of encapsulated cells in vivo. Physiological endocrine responses may indeed not be expected because of the many barriers that the metabolites encounter when traveling from the blood stream to the enveloped cells and back to circulation. However, despite these diffusion barriers, many studies have shown optimal regulation, allowing us to conclude that encapsulated grafts do not always follow nature's course but are still a possible solution for many endocrine disorders for which the minute-to-minute regulation of metabolites is mandatory.

Investigating design principles of micropatterned encapsulation systems containing high-density microtissue arrays

Immunoisolation is an important strategy to protect transplanted cells from rejection by the host immune system. Recently, microfabrication techniques have been used to create hydrogel membranes to encapsulate microtissue in an arrayed organization. The method illustrates a new macroencapsulation paradigm that may allow transplantation of a large number of cells with microscale spatial control, while maintaining an encapsulation device that is easily maneuverable and remaining integrated following transplantation. This study aims to investigate the design principles that relate to the translational application of micropatterned encapsulation membranes, namely, the control over the transplantation density/quantity of arrayed microtissues and the fidelity of pre-formed microtissues to micropatterns. Agarose hydrogel membranes with microwell patterns were used as a model encapsulation system to exemplify these principles. Our results show that high-density micropatterns can be generated in hydrogel membranes, which can potentially maximize the percentage volume of cellular content and thereby the transplantation efficiency of the encapsulation device. Direct seeding of microtissues demonstrates that microwell structures can efficiently position and organize pre-formed microtissues, suggesting the capability of micropatterned devices for manipulation of cellular transplants at multicellular or tissue levels. Detailed theoretical analysis was performed to provide insights into the relationship between micropatterns and the transplantation capacity of membrane-based encapsulation. Our study lays the ground for developing new macroencapsulation systems with microscale cellular/tissue patterns for regenerative transplantation.

Cell encapsulation via microtechnologies

The encapsulation of living cells in a variety of soft polymers or hydrogels is important, particularly, for the rehabilitation of functional tissues capable of repairing or replacing damaged organs. Cellular encapsulation segregates cells from the surrounding tissue to protect the implanted cell from the recipient's immune system after transplantation. Diverse hydrogel membranes have been popularly used as encapsulating materials and permit the diffusion of gas, nutrients, wastes and therapeutic products smoothly. This review describes a variety of methods that have been developed to achieve cellular encapsulation using microscale platform. Microtechnologies have been adopted to precisely control the encapsulated cell number, size and shape of a cell-laden polymer structure. We provide a brief overview of recent microtechnology-based cell encapsulation methods, with a detailed description of the relevant processes. Finally, we discuss the current challenges and future directions likely to be taken by cell microencapsulation approaches toward tissue engineering and cell therapy applications.

Polymerizable superoxide dismutase mimetic protects cells encapsulated in poly(ethylene glycol) hydrogels from reactive oxygen species-mediated damage

A polymerizable superoxide dismutase mimetic (SODm) was incorporated into poly(ethylene glycol) (PEG) hydrogels to protect encapsulated cells from superoxide-mediated damage. Superoxide and other small reactive oxygen species (ROS) can cause oxidative damage to donor tissue encapsulated within size exclusion barrier materials. To enzymatically breakdown ROS within biomaterial cell encapsulation systems, Mn(III) Tetrakis[1-(3-acryloxy-propyl)-4-pyridyl] porphyrin (MnTTPyP-acryl), a polymerizable manganese metalloporphyrin SOD mimetic, was photopolymerized with PEG diacrylate (PEGDA) to create functional gels. In unmodified PEG hydrogels, a significant reduction in metabolic activity was observed when encapsulated Min6 β-cells were challenged with chemically generated superoxide. Cells encapsulated within MnTPPyP-co-PEG hydrogels, however, demonstrated greatly improved metabolic activity following various superoxide challenges. Further, cells were encapsulated and cultured for 10 days within MnTPPyP-co-PEG hydrogels and challenged with superoxide on days 4, 6, and 8. At the conclusion of this study, cells in blank PEG hydrogels had no observable metabolic activity but when encapsulated in MnTPPyP-functionalized hydrogels, cells retained 60 ± 5% of the metabolic activity compared to untreated controls.

Immunoisolating semi-permeable membranes for cell encapsulation: focus on hydrogels

Cell-based medicine has recently emerged as a promising cure for patients suffering from various diseases and disorders that cannot be cured/treated using technologies currently available. Encapsulation within semi-permeable membranes offers transplanted cell protection from the surrounding host environment to achieve successful therapeutic function following in vivo implantation. Apart from the immunoisolation requirements, the encapsulating material must allow for cell survival and differentiation while maintaining its physico-mechanical properties throughout the required implantation period. Here we review the progress made in the development of cell encapsulation technologies from the mass transport side, highlighting the essential requirements of materials comprising immunoisolating membranes. The review will focus on hydrogels, the most common polymers used in cell encapsulation, and discuss the advantages of these materials and the challenges faced in the modification of their immunoisolating and permeability characteristics in order to optimize their function.

Design of a composite drug delivery system to prolong functionality of cell-based scaffolds

Cell encapsulation technology raises hopes in medicine and biotechnology. However, despite important advances in the field in the past three decades, several challenges associated with the biocompatibility are still remaining. In the present study, the effect of a temporary release of an anti-inflammatory agent on co-administered encapsulated allogeneic cells was investigated. The aim was to determine the biocompatibility and efficacy of the approach to prevent the inflammatory response. A composite delivery system comprised of alginate-poly-l-lysine-alginate (APA)-microencapsulated Epo-secreting myoblasts and dexamethasone (DXM)-releasing poly(lactic-co-glycolic acid) (PLGA) microspheres was implanted in the subcutaneous space of Balb/c mice for 45 days. The use of independently co-implanted DXM-loaded PLGA microspheres resulted in an improved functionality of the cell-based graft, evidenced by significantly higher hematocrit levels found in the cell-implanted groups by day 45, which was found to be more pronounced when higher cell-doses (100 μL) were employed. Moreover, no major host reaction was observed upon implantation of the systems, showing good biocompatibility and capability to partially avoid the inflammatory response, probably due to the immunosuppressive effects related to DXM. The findings of this study imply that DXM-loaded PLGA microspheres show promise as release systems to enhance biocompatibility and offer advantage in the development of long-lasting and effective implantable microencapsulated cells by generating a potential immunopriviledged local environment and an effective method to limit the structural ensheathing layer caused by inflammation.

Inducing local T cell apoptosis with anti-Fas-functionalized polymeric coatings fabricated via surface-initiated photopolymerizations

Cell encapsulation has long been investigated as a means to achieve transplant immunoprotection as it creates a physical barrier between allograft tissue and host immune cells. Encapsulation with passive barrier materials alone, however, is generally insufficient to protect donor tissue from rejection, because small cytotoxic molecules produced by activated T cells can diffuse readily into the capsule and mediate allograft death. As a means to provide bioactive protection for polymeric encapsulation devices, we investigated a functionalized polymeric coating that mimics a natural T cell regulation pathway. T cells are regulated in vivo via Fas, a well-known 'death receptor,' whereby effector cells express Fas ligand and elicit T cell apoptosis upon binding the Fas receptor on a T cell surface. Anti-Fas antibodies are capable of replicating this effect and induce T cell apoptosis in solution. Here, an iniferter-based living radical polymerization was utilized to fabricate surface-anchored polymer chains containing poly(ethylene glycol) with covalently incorporated pendant anti-Fas antibody. Using this reaction mechanism, we demonstrate fabrication conditions that yield surface densities in excess of 1.5 ng/cm(2) of incorporated therapeutic, as detected by ELISA. Additionally, we show that coatings containing anti-Fas antibody induced significant T cell apoptosis, 21+/-2% of cells, after 24h. Finally, the incorporation of a T cell adhesion ligand, intracellular adhesion molecule-1, along with anti-Fas antibody, yielded even higher levels of apoptosis, 34+/-1% of T cells, compared to either signal alone.

Cross-linked microcapsules formed from self-deactivating reactive polyelectrolytes

Poly(methyl vinyl ether-alt-maleic anhydride) (PMM(0)) was partially hydrolyzed in a 9/1 acetonitrile-d(3)/D(2)O mixture and then diluted with an aqueous buffer and coated onto poly-L-lysine (PLL)-coated calcium alginate capsules. The resulting 50% hydrolyzed polymer (PMM(50)) is bound to the surface-immobilized PLL through both electrostatic and covalent interactions, resulting in a shell-cross-linked hydrogel capsule that is resistant to chemical challenges. Further hydrolysis of PMM(50) in aqueous buffer was monitored by potentiometry and was found to proceed with a half-life time of about 2.5 min at 20 degrees C such that residual anhydride groups not consumed by cross-linking with PLL would be deactivated by hydrolysis within several minutes of shell formation, removing potential sites for undesired protein binding. Initial protein-binding tests involving incubation of the capsules in bovine serum albumin solutions for 24 h showed no indication of protein binding. The effects of coating temperature, PLL concentration and molecular weight, PMM(50) molecular weight, and multiple PLL-PMM(50) coatings on shell morphology and behavior were studied using confocal fluorescence microscopy as well as chemical challenges involving sodium citrate and sodium hydroxide. The resilience of the cross-linked shell improved with increasing concentrations of PLL and decreasing molecular weight of PMM(50), both of which resulted in more polyelectrolyte being bound to the capsule. The permeability of these covalently cross-linked capsules was studied using fluorescently labeled dextrans and was found to be comparable to standard calcium alginate-PLL-alginate (APA) capsules.

Modulation of single-walled carbon nanotube photoluminescence by hydrogel swelling

We demonstrate the use of hydrogel swelling as a mechanism to reversibly induce solvatochromic shifting in single-walled carbon nanotube (SWNT) near-infrared emission within a biocompatible hydrogel. The optical sensor reports the degree of the swelled state and glucose concentration when apo-glucose oxidase is used to cross-link the hydrogel. Photoluminescence emission maxima from dispersed nanotubes in a poly(vinyl alcohol) hydrogel shift as cross-linking is increased, with a maximum of -48 meV for the (6,5) nanotube. The Raman tangential mode also red shifts up to 17 cm(-1), indicative of nanotube lattice strain equivalent to an effective hydrostatic pressure of 3 GPa. While the electronic band gaps of SWNTs are known to either increase or decrease with uniaxial strain or lattice deformation depending on chiral vector, we show that the mechanism of detection is counterintuitively non-strain-dependent. Instead, the data are well-described by a model that accounts for changes in dielectric screening of the 1-D exciton, as the osmotic pressure forces conformational distortions in the PVA by rotating more polar groups to the nanotube surface. The model describes observed changes with hydration state and cross-linking density variation from 0 to 14%. Cross-linking with apo-glucose oxidase renders the hydrogel glucose responsive, and we demonstrate rapid and reversible detection of glucose from these systems after repeated cycling of 10 mM glucose. We also demonstrate detection and imaging in the near-infrared of implanted hydrogel sensors in a mouse tissue model, showing excellent signal-to-noise of 8.6 and contrast with integration times of 60 s.

SU-8-based immunoisolative microcontainer with nanoslots defined by nanoimprint lithography

Cells can secrete biotherapeutic molecules that can replace or restore host function. The transplantation of such cells is a promising therapeutic modality for the treatment of several diseases including type 1 diabetes mellitus. These cellular grafts are encapsulated in semipermeable and immunoisolative membranes to protect them from the host immune system, while allowing the transport of nutrients and small molecules that are required for cell survival and function. The authors report on SU-8-based biocompatible immunoisolative cuboid microcontainers for cell transplantation. Each microcontainer comprises a 300×300×250 or a 1100×1100×250 μm(3) SU-8 hollowed cuboid base that houses the cells and an optically transparent SU-8-based nanoporous lid that closes the device. The hollowed cuboid base was formed by conventional optical lithography to have 8 nl (200×200×200 μm(3)) encapsulation volume for cellular payload. The lid comprises a thick SU-8 slab with an array of cylindrical wells, whose bottom surface is sealed with a thin nanoporous SU-8 membrane. The nanoporous membrane was created from a 100 nm grating (width and spacing) initial silicon mold subjected to a repeated cycle of oxidation and wet etching to achieve a 20 nm wide and 200 nm pitch nano silicon grating. Nanoimprinting and oblique-angle metal deposition, followed by inductively coupled plasma etching were utilized to create 15 nm wide and 350-450 nm deep nanoslots in the thin SU-8 membrane. Isolated mouse islets were encapsulated in the hollowed cuboid base and the nanoporous lid was assembled on top. The penetration of large and small molecules into the microcontainer was observed with fluorescence.

Challenges and emerging technologies in the immunoisolation of cells and tissues

Protection of transplanted cells from the host immune system using immunoisolation technology will be important in realizing the full potential of cell-based therapeutics. Microencapsulation of cells and cell aggregates has been the most widely explored immunoisolation strategy, but widespread clinical application of this technology has been limited, in part, by inadequate transport of nutrients, deleterious innate inflammatory responses, and immune recognition of encapsulated cells via indirect antigen presentation pathways. To reduce mass transport limitations and decrease void volume, recent efforts have focused on developing conformal coatings of micron and submicron scale on individual cells or cell aggregates. Additionally, anti-inflammatory and immunomodulatory capabilities are being integrated into immunoisolation devices to generate bioactive barriers that locally modulate host responses to encapsulated cells. Continued exploration of emerging paradigms governed by the inherent challenges associated with immunoisolation will be critical to actualizing the clinical potential of cell-based therapeutics.

Cotransplanted hepatic stellate cells enhance vascularization of islet allografts

Islet transplantation is an alternative to whole pancreas transplantation in curative therapy of diabetics. The outcome of engraftment of islet, however, remains disappointing. Rapid and adequate islet revascularization is crucial for the survival and function of transplanted islets. In this study, hepatic stellate cells (HSC) were cotransplanted with islet allografts, achieving marked prolongation of islet allografts. This was associated with enhanced revascularization within islet grafts as determined by anti-CD31 antibody staining.

Allotransplantation of Cultured Parathyroid Progenitor Cells Without Immunosuppression: Clinical Results

BACKGROUND

Hypoparathyroidism is a well-known consequence of extensive thyroid and parathyroid surgery. Allotransplantation of cultured parathyroid cells can be considered as an alternative to vitamin D3 and calcium supplementation in treatment of hypoparathyroidism. We present the long-term allotransplant activity in 85 patients who had undergone cellular allotransplantation for surgical hypoparathyroidism. Also, a modified technique to prepare parathyroid explants is described for obtaining a new nonimmunogenic cell population.

METHODS

From March 1990 to December 2004, 85 patients underwent 116 allotransplantations of cultured parathyroid cells. Mean recipient age was 46.2+/-11.1 years. Donors were selected from patients undergoing parathyroidectomy for secondary and tertiary hyperparathyroidism.

RESULTS

After 6 weeks of cultivation and freezing, the parathyroid cells decreased their normal human leukocyte antigen (HLA) class I ABC expression and were free of HLA class II positive cells. The viability of cultured cells was 95.15+/-2.94%. Eighty-five patients underwent primary allotransplantation. Of these, 25 patients subsequently underwent a repeat procedure. In six cases, the parathyroid cells were obtained from the same donor and in 19 cases from a different donor. For all patients, the mean cellular allograft survival was 6.35+/-13.08 months. In 64 patients (55.1%), the allografts retained their endocrine function for more than 2 months.

CONCLUSIONS

The present study has shown that in some patients parathyroid cell allotransplantation may be considered a method of treatment for permanent hypoparathyroidism after thyroid surgery. Graft function and/or survival did not depend on the baseline viability or secretory activity of cultured cells used for transplantation.

Polymeric gene transfection on insulin-secreting cells: sulfonylurea receptor-mediation and transfection medium effect

PURPOSE

In vitro transfection of secreting cells is regarded as one strategy for improved cell engineering/ transplantation. Insulin-secreting insulinoma cell lines or pancreatic beta-cells could be genetically engineered using designed polymeric vectors which are safer than viral vectors. This study investigates the effects of the constituents in transfection media on polymeric transfection.

METHODS

Polyplexes conjugated with sulfonylurea (SU) were evaluated under different transfection conditions for gene transfection and their effects on cytotoxicity and insulin secretion. Several components in transfection media specifically associated with the insulin secretion pathway were amino acids, vitamins, Ca2+ and K+. The interactions of the polyplexes with insulin were monitored by surface charge and particle size to monitor how insulin as a protein influences transfection.

RESULTS

For an insulin-secreting cell line (RINm5F), polyplexes in Ca2+--containing KRH medium (Ca2+(+)KRH) enhanced transfection and did not cause damage to biological functions. When adding amino acids, vitamins, or K+ or depleting Ca2+ from Ca2+(+)KRH, poly(L-lysine)/DNA complexes showed a greater reduction in transfection than SU receptor (SUR)-targeting polyplexes (SU-polyplex). Positively charged polyplexes interacted with insulin, developing a negative surface charge, and these interactions may cause a decrease in transfection.

CONCLUSION

The findings suggest that in vitro and ex vivo polymeric transfection of insulin-secreting cells can be modulated and enhanced by adjusting the transfection conditions.

In vivo immune modulatory activity of hepatic stellate cells in mice

Accumulating data suggest that hepatic tolerance, initially demonstrated by spontaneous acceptance of liver allografts in many species, results from an immune regulatory activity occurring in the liver. However, the responsible cellular and molecular components have not been completely understood. We have recently described profound T cell inhibitory activity of hepatic stellate cells (HSCs) in vitro. In this study, we demonstrate in vivo evidence of immune modulatory activity of HSCs in mice using an islet transplantation model. Co-transplanted HSCs effectively protected islet allografts from rejection, forming a multi-layered capsule, which reduced allograft immunocyte infiltrates by enhancement of apoptotic death. The immune modulation by HSCs appeared to be a local effect, and regulated by inducible expression of B7-H1, an inhibitory molecule of B7 family. This may reflect an intrinsic mechanism of immune inhibition mediated by liver-derived tissue cells. In conclusion, these results may lead to better understanding of liver immunobiology and development of new strategies for treatment of liver diseases.

Improved phenotype of rat islets in a macrocapsule by co-encapsulation with cross-linked Hb

A number of rat islets were co-encapsulated in a diffusion chamber-type device, i.e., macrocapsule, with a thermoreversible polymeric extracellular matrix (ECM) and bioactive ingredient of cross-linked hemoglobin (Hb-C). The ECM was formed from an aqueous solution of N-isopropyl-acrylamide co-polymers with a small amount of acrylic acid, which exhibited unique sol-gel transition in a temperature range of 30-34 degrees C, without noticeable hysteresis. The incorporation of Hb-C in the islet macrocapsule showed a concentration-dependent effect on insulin secretion and viability of the entrapped islets. Insulin secretion stimulation by glucose and cell viability were more than doubled when compared with a control group (without Hb-C), at an optimum Hb-C concentration of 0.25 mM due to its unique oxygen transporting capacity. Furthermore, 0.25 mM Hb-C in the macrocapsule was able to support islet density up to 1000 islets/device in a 154 microl total volume without negative effects on islet functionality and viability. Hb-C incorporation is an effective strategy for a macrocapsule-type biohybrid artificial pancreas for Type-I diabetes treatment, which can be further developed to a rechargeable system by employing the thermoreversible ECM and designing a proper macrocapsule.

Ketoprofen controlled release from composite microcapsules for cell encapsulation: Effect on post-transplant acute inflammation

Cell encapsulation technology raises hopes in medicine and biotechnology. Encapsulated pancreatic islets is a promising approach for the final solution of Type 1 diabetes. Unfortunately, evidence of long-term encapsulated islet graft survival and functional competence lies behind expectancy. Failure was often ascribed to the lack of biocompatibility generating inflammatory response, or limited immunobarrier competence or hypoxia or finally, low beta-cell replication. In order to prevent severe inflammation at early stages after implantation, composite microcapsules were designed. Biodegradable microspheres containing ketoprofen were enveloped into the well established alginate/poly-L-ornithine/alginate capsules. Polyester microspheres were prepared, by solvent evaporation, and characterized for encapsulation efficiency, particle size and in vitro release. Biocompatibility and efficacy to prevent the inflammatory response were studied in vivo. Good encapsulation efficiency and the desired particle size were achieved. In vitro release studies evidenced a high burst effect probably due to a plasticizing effect of both water and ketoprofen. The composite systems showed good biocompatibility and capacity to completely avoid the inflammatory response and the pericapsular cell overgrowth. In conclusion, the inflammatory response in the immediate post-transplant period can be circumvented using multicompartment microcapsules releasing non-steroidal anti inflammatory drugs.

Therapeutic insulins and their large-scale manufacture

Biotechnological innovations over the past 25 years have underpinned the rapid development of a thriving biopharmaceutical sector. Therapeutic insulin remains one of the most commonly used products of pharmaceutical biotechnology and insulin-based products command annual global sales in excess of $4.5 billion. Innovations in its method of production and in particular the advent of engineered insulin analogues provide a fascinating insight into how scientific and technological advances have impacted upon the pharmaceutical biotechnology sector as a whole. Current insulin-based diabetes research is increasingly focused not on the insulin molecule per se, but upon areas such as the development of non-parenteral insulin delivery systems, as well as organ-/cell-based and gene therapy-based approaches to controlling the disease.

Prolonged Glucose Normalization of Streptozotocin-Induced Diabetic Mice by Transplantation of Rat Islets Coencapsulated with Crosslinked Hemoglobin

BACKGROUND

Facilitated oxygen transport by crosslinked hemoglobin (Hb-C) in islet microcapsules may promote transplanted graft function by improving islet functionality and viability.

METHODS

This study investigated the in vivo efficacy of Hb-C as an oxygen carrier on the functionality and viability of microencapsulated rat islets. Hb-C by poly(ethylene glycol) was introduced into rat islet microcapsules (alginate-poly[L-lysine]-alginate microcapsule), and 500 suboptimal encapsulated islets were xenotransplanted into each streptozotocin-induced diabetic BALB/c mouse. The graft efficacy over time was evaluated by measuring nonfasting blood glucose level, body weight, and glucose tolerance.

RESULTS

Mice that received Hb-C-containing microcapsules maintained normoglycemia for at least 8 weeks with normal glucose clearance, determined by intraperitoneal glucose tolerance test. However, the mice that received the conventional control islet microcapsule (without Hb-C) transplant showed graft failure in 4 weeks, exhibited by hyperglycemia, weight loss, and deteriorated glucose tolerance. Severe central necrosis of retrieved islets was observed for the control islet capsule graft after 8 weeks.

CONCLUSION

The present study revealed that the incorporation of Hb-C in islet microcapsules promotes graft function for a longer period of time than the conventional islet capsules. Therefore, Hb-C coencapsulation is a potential approach for prolonging graft function of islet microcapsules and reducing the number of islets required for normoglycemia.

MIN6 cells-enclosing aminopropyl-silicate membrane templated by alginate gels differences in guluronic acid content

Mouse insulinoma (MIN6) cells were encapsulated into aminopropyl-silicate membrane deposited on calcium alginate gel beads via the sol-gel synthesis. Two alginates with different guluronic acid (G) contents, high and intermediate, but with the same molecular weights were used. Viability of the cells in the membrane templated by the alginate with an intermediate content of guluronic acid (intermediate-G) was approximately 10% higher than those in the membrane templated by the alginate with a high content of guluronic acid immediately after encapsulation. Growth of cells in vitro was hindered in case of encapsulation in the aminopropyl-silicate membrane deposited on the high-G alginate gel. The MIN6 cells in the microcapsule made from high-G alginate needed a longer period to establish a normoglycemic in recipients than those in the microcapsule made from intermediate-G alginate despite the same number of viable cells implantation. Recipients of the microcapsule with the core made from the intermediate-G alginate maintained their blood glucose values less than 300 mg/dl for a longer period.

Encapsulation of individual pancreatic islets by sol-gel SiO2: a novel procedure for perspective cellular grafts

Pancreatic rat islets are encapsulated by a siliceous layer deposited on the surface of single islets upon reaction with gaseous siliceous precursors. The process preserves original islet dimensions and does not suppress viability or function. The encapsulated material is homogeneously distributed on the islet surface, and layer thickness can be controlled in the 0.1-2.0 microm interval. Dynamic perfusion experiments with glucose stimulation were carried out in both encapsulated and non-encapsulated islets. Results were treated according to a kinetic model presented here for the analysis of perfusion data; the model tested by literature data, was used to substantiate the diffusion features of the siliceous layer, which does not affect mass transfer of insulin but which modifies the texture of the islet surface tissue. The clinical potential of silica encapsulation was demonstrated by in vivo experiments using encapsulated islets transplanted into diabetic rats. Transplantation was carried out in both inbred and outbred rats and indicated prolonged restoration of normal glycaemia levels and protection from immunological attack.

Thyrocyte integration, and thyroid folliculogenesis and tissue regeneration: perspective for thyroid tissue engineering

The thyroid gland is composed of many ball-like structures called thyroid follicles, which are supported by the interfollicular extracellular matrix (ECM) and a capillary network. The component thyrocytes are highly integrated in their specific structural and functional polarization. In conventional monolayer and floating culture systems, thyrocytes cannot organize themselves into follicles with normal polarity. In contrast, in 3-D collagen gel culture, thyrocytes easily form stable follicles with physiological polarity. Integration of thyrocyte growth and differentiation results ultimately in thyroid folliculogenesis. This culture method and subacute thyroiditis are two promising models for addressing mechanisms of folliculogenesis, because thyroid-follicle formation actively occurs both in the culture system and at the regenerative phase of the disorder. The understanding of the mechanistic basis of folliculogenesis is prerequisite for generation of artificial thyroid tissue, which would enable a more physiological strategy to the treatment of hypothyroidism caused by various diseases and surgical processes than conventional hormone replacement therapy. We review here thyrocyte integration, and thyroid folliculogenesis and tissue regeneration. We also briefly discuss a perspective for thyroid tissue regeneration and engineering.

Bioartificial pancreas: materials, devices, function, and limitations

The term "bioartificial endocrine pancreas" (BEP) was introduced by Anthony Sun in 1980. It was in 1968, however, that Thomas Chang proposed the use of microencapsulated islets as artificial beta-cells. By applying a semipermeable membrane on the top of microcapsules, a system can be produced that is impermeable to viable islet cells and large effector molecules of the immune system, thus providing a protection for transplanted islets against rejection. Since then, the term BEP has not often appeared in papers. Instead, the term "bioartificial pancreas" (BAP) has gained widespread use. In a broader sense, BAP would include an application of suitable endocrine cells and protective polymeric vehicles, but not necessarily providing a filtration barrier of precisely defined properties (e.g., cells injected into a gel of hyaluronate).