Effect of alginate encapsulation on the cellular transcriptome of human islets

Attenuated Angiogenesis and Macrophage Infiltration during Adipose Tissue Regeneration in Megavolume Human Fat Grafting

BACKGROUND

Survival and regeneration mechanisms of large (>250 mL) fat grafts remain incompletely understood. In fat grafts from volunteers with megavolume fat transfer breast augmentation, neovascularization and inflammatory cell infiltration decreased within 7 days according to histologic analysis. The authors further investigated this phenomenon using a nude mouse model.

METHODS

To simulate clinical contexts, chambers containing 1 mL of human fat were implanted into nude mice. Chambers allowed selective transfer of tissue fluid from recipient nude mice into chambers, but not capillaries or macrophages. Seven days later, fat was removed from the chamber and reimplanted into a new nude mouse in the open-chambered fat group (OCFG) ( n = 45). Adipose samples from volunteers and explanted grafts from OCFG were subjected to histologic analyses. Graft weight, vascularization, and immune response were also compared between the OCFG and conventional direct fat grafting (control group [CG]).

RESULTS

Percentage tissue integrity, percentage fibrosis, adipocyte viability, and neovascularization did not significantly differ between volunteer samples and OCFG grafts at day 7. On day 90, OCFG retention rate was decreased relative to the CG, and the fibrosis area was larger in the OCFG than in the CG. However, the macrophage and capillary counts were lower in the OCFG group relative to the CG at days 7 and 14 after transplantation.

CONCLUSIONS

The present study provides histologic analyses of megavolume fat grafts sampled from clinical breast augmentation tissues and a xenograft nude mouse model. However, these preliminary results in a small clinical cohort should be further assessed in large allogeneic animal models.

CLINICAL RELEVANCE STATEMENT

The results of this study will help surgeons understand the early regeneration of transplanted fat after large volume fat grafting for breast augmentation.

The potential of the incorporated collagen microspheres in alginate hydrogel as an engineered three-dimensional microenvironment to attenuate apoptosis in human pancreatic islets

BACKGROUND

Tissue engineering is considered as a promising tool for remodeling the native cells microenvironment. In the present study, the effect of alginate hydrogel and collagen microspheres integrated with extracellular matrix components were evaluated in the decrement of apoptosis in human pancreatic islets.

MATERIALS/METHODS

For three-dimensional culture, the islets were encapsulated in collagen microspheres, containing laminin and collagen IV and embedded in alginate scaffold for one week. After that the islets were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through glucose-induced insulin and C-peptide secretion assay. In order to evaluate the structure of the scaffolds and the morphology of the pancreatic islets in three-dimensional microenvironments, we performed scanning electron microscopy.

RESULTS

Our findings showed that the designed hydrogel scaffolds significantly improved the islets viability using the reduction of activated caspase-3 and TUNEL positive cells.

CONCLUSIONS

The reconstruction of the destructed matrix with alginate hydrogels and collagen microspheres might be an effective step to promote the culture of the islets.

A Low-Cost Open Source Device for Cell Microencapsulation

Microencapsulation is a widely studied cell therapy and tissue bioengineering technique, since it is capable of creating an immune-privileged site, protecting encapsulated cells from the host immune system. Several polymers have been tested, but sodium alginate is in widespread use for cell encapsulation applications, due to its low toxicity and easy manipulation. Different cell encapsulation methods have been described in the literature using pressure differences or electrostatic changes with high cost commercial devices (about 30,000 US dollars). Herein, a low-cost device (about 100 US dollars) that can be created by commercial syringes or 3D printer devices has been developed. The capsules, whose diameter is around 500 µm and can decrease or increase according to the pressure applied to the system, is able to maintain cells viable and functional. The hydrogel porosity of the capsule indicates that the immune system is not capable of destroying host cells, demonstrating that new studies can be developed for cell therapy at low cost with microencapsulation production. This device may aid pre-clinical and clinical projects in low- and middle-income countries and is lined up with open source equipment devices.

Growth and survival of microencapsulated probiotics prepared by emulsion and internal gelation

Efficient microencapsulation of probiotics by most existing methods is limited by low throughput. In this work, Saccharomyces boulardii and Enterococcus faecium were microencapsulated by a method based on emulsion and internal gelation. The growth and survival of microencapsulated microbes under different stressors were investigated using free non-encapsulated ones as a control. The results showed that the prepared micro-beads by emulsion and internal gelation exhibited a spherical and smooth shape, with sizes between 300 and 500 μm. Both S. boulardii and E. faecium grew well and survived better when encapsulated in micro-beads. The survival rates were increased 25% and 40% for microencapsulated S. boulardii and E. faecium respectively when compared with non-encapsulated controls under high temperature and high humidity. The increases of survival rates were 60% for microencapsulated S. boulardii and 25% for E. faecium in simulated gastric juice. And the increases were 15% and 20% respectively when the survival rates of the microencapsulated S. boulardii and E. faecium were determined in simulated intestinal juice. The microencapsulation by emulsion and internal gelation offers an effective way to protect microbes in adverse in vitro and in vivo conditions and is promising for the large-scale production of probiotics microencapsulation.

Current and Future Perspectives on Alginate Encapsulated Pancreatic Islet

Transplantation of pancreatic islets in immune protective capsules holds the promise as a functional cure for type 1 diabetes, also about 40 years after the first proof of principal study. The concept is simple in using semipermeable capsules that allow the ingress of oxygen and nutrients, but limit the access of the immune system. Encapsulated human islets have been evaluated in four small clinical trials where the procedure has been evaluated as safe, but lacking long-term efficacy. Host reactions toward the biomaterials used in the capsules may be one parameter limiting the long-term function of the graft in humans. The present article briefly discusses important capsule properties such as stability, permeability and biocompatibility, as well as possible strategies to overcome current challenges. Also, recent progress in capsule development as well as the production of insulin-producing cells from human stem cells that gives promising perspectives for the transplantation of encapsulated insulin-producing tissue is briefly discussed. Stem Cells Translational Medicine 2017;6:1053-1058.

Insight into microenvironment remodeling in pancreatic endocrine tissue engineering: Biological and biomaterial approaches

The treatment of diabetes mellitus, as a chronic and complicated disease, is a valuable purpose. Islet transplantation can provide metabolic stability and insulin independence in type 1 diabetes patients. Diet and insulin therapy are only diabetes controllers and cannot remove all of the diabetes complications. Moreover, islet transplantation is more promising treatment than whole pancreas transplantation because of lesser invasive surgical procedure and morbidity and mortality. According to the importance of extracellular matrix for islet viability and function, microenvironment remodeling of pancreatic endocrine tissue can lead to more success in diabetes treatment by pancreatic islets. Production of bioengineered pancreas and remodeling of pancreas extracellular matrix provide essential microenvironment for re-vascularization, re-innervation and signaling cascades triggering. Therefore, islets show better viability and function in these conditions. Researchers conduct various scaffolds with different biomaterials for the improvement of islet viability, function and transplantation outcome. The attention to normal pancreas anatomy, embryology and histology is critical to understand the pancreatic Langerhans islets niche and finally to achieve efficient engineered structure. Therefore, in the present study, the status and components of the islets niche is mentioned and fundamental issues related to the tissue engineering of this structure is considered. The purpose of this review article is summarization of recent progress in the endocrine pancreas tissue engineering and biomaterials and biological aspects of it.

Microencapsulation of tumor lysates and live cell engineering with MIP-3α as an effective vaccine

The combination of several potential strategies so as to develop new tumor vaccines is an attractive field of translational medicine. Pulsing tumor lysates with dendritic cells (DCs), in-vivo attraction of DCs by macrophage inflammatory protein 3α (MIP-3α), and reversion of the tumor suppressive microenvironment have been tested as strategies to develop tumor vaccines. In this study, we generated an alginate microsphere (named PaLtTcAdMIP3α) that encapsulated tumor lysates, live tumor cells engineering with a recombinant MIP-3α adenovirus and BCG. We used PaLtTcAdMIP3α as a model vaccine to test its antitumor activities. Our results showed that PaLtTcAdMIP3α expressed and excreted MIP-3α, which effectively attracted DCs ex vivo and in vivo. Injection of PaLtTcAdMIP3α into tumor-bearing mice effectively induced both therapeutic and prophylactic antitumor immunities in CT26, Meth A, B16-F10 and H22 models, but without any ensuing increase in adverse effects. Both tumor-specific cellular and humoral immune responses, especially the CD8(+) T cell-dependent cytotoxic T immunity, were found in the mice injected with PaLtTcAdMIP3α. The anti-tumor activity was abrogated completely by depletion of CD8(+) and partially by CD4(+) T lymphocytes. In addition, the number of IFN-γ-producing CD8(+) T cells in spleen and tumor tissues was significantly increased; but the number of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) in tumor tissues was decreased. These data strongly suggest that a combination of multi-current-using strategies such as the novel approach of using our PaLtTcAdMIP3α microspheres could be an effective tumor model vaccine.

Encapsulated islets for diabetes therapy: history, current progress, and critical issues requiring solution

Insulin therapy became a reality in 1921 dramatically saving lives of people with diabetes, but not protecting them from long-term complications. Clinically successful free islet implants began in 1989 but require life long immunosuppression. Several encapsulated islet approaches have been ongoing for over 30 years without defining a clinically relevant product. Macro-devices encapsulating islet mass in a single device have shown long-term success in large animals but human trials have been limited by critical challenges. Micro-capsules using alginate or similar hydrogels encapsulate individual islets with many hundreds of promising rodent results published, but a low incidence of successful translation to large animal and human results. Reduction of encapsulated islet mass for clinical transplantation is in progress. This review covers the status of both early and current studies including the presentation of corporate efforts involved. It concludes by defining the critical items requiring solution to enable a successful clinical diabetes therapy.

Advances in biocompatibility and physico-chemical characterization of microspheres for cell encapsulation

Cell encapsulation has already shown its high potential and holds the promise for future cell therapies to enter the clinics as a large scale treatment option for various types of diseases. The advancement in cell biology towards this goal has to be complemented with functional biomaterials suitable for cell encapsulation. This cannot be achieved without understanding the close correlation between cell performance and properties of microspheres. The ongoing challenges in the field of cell encapsulation require a critical view on techniques and approaches currently utilized to characterize microspheres. This review deals with both principal subjects of microspheres characterization in the cell encapsulation field: physico-chemical characterization and biocompatibility. The up-to-day knowledge is summarized and discussed with the focus to identify missing knowledge and uncertainties, and to propose the mandatory next steps in characterization of microspheres for cell encapsulation. The primary conclusion of this review is that further success in development of microspheres for cell therapies cannot be accomplished without careful selection of characterization techniques, which are employed in conjunction with biological tests.

A Technology Platform to Test the Efficacy of Purification of Alginate

Alginates are widely used in tissue engineering technologies, e.g., in cell encapsulation, in drug delivery and various immobilization procedures. The success rates of these studies are highly variable due to different degrees of tissue response. A cause for this variation in success is, among other factors, its content of inflammatory components. There is an urgent need for a technology to test the inflammatory capacity of alginates. Recently, it has been shown that pathogen-associated molecular patterns (PAMPs) in alginate are potent immunostimulatories. In this article, we present the design and evaluation of a technology platform to assess (i) the immunostimulatory capacity of alginate or its contaminants, (ii) where in the purification process PAMPs are removed, and (iii) which Toll-like receptors (TLRs) and ligands are involved. A THP1 cell-line expressing pattern recognition receptors (PRRs) and the co-signaling molecules CD14 and MD2 was used to assess immune activation of alginates during the different steps of purification of alginate. To determine if this activation was mediated by TLRs, a THP1-defMyD88 cell-line was applied. This cell-line possesses a non-functional MyD88 coupling protein, necessary for activating NF-κB via TLRs. To identify the specific TLRs being activated by the PAMPs, we use different human embryonic kidney (HEK) cell-line that expresses only one specific TLR. Finally, specific enzyme-linked immunosorbent assays (ELISAs) were applied to identify the specific PAMP. By applying this three-step procedure, we can screen alginate in a manner, which is both labor and cost efficient. The efficacy of the platform was evaluated with an alginate that did not pass our quality control. We demonstrate that this alginate was immunostimulatory, even after purification due to reintroduction of the TLR5 activating flagellin. In addition, we tested two commercially available purified alginates. Our experiments show that these commercial alginates contained peptidoglycan, lipoteichoic acid, flagellin, and even lipopolysaccharides (LPS). The platform presented here can be used to evaluate the efficacy of purification procedures in removing PAMPs from alginates in a cost-efficient manner.

Microfluidic synthesis of tail-shaped alginate microparticles using slow sedimentation

This study reports the synthesis of tail-shaped alginate particles using a microfluidic platform combined with a sedimentation strategy. By utilizing microfluidic emulsification in the cross-junction channel, the formation of regular droplets was achieved. Following a facile and convenient sedimentation process and an ionic crosslinking process, sodium-alginate droplets became tail-shaped and then gradually developed into calcium-alginate microparticles. The effects of the concentration of the CaCl(2) crosslinker and the viscosity of the alginate solution on the shape and/or size of the particles were further investigated. The proposed synthesis methodology has the advantages of actively controlling the tail-shape formation, having a narrow size distribution, as well as being a facile and convenient process with a high throughput. This approach can be applied to many applications in the pharmaceutical and biomedical arena.