The encapsulation of stem cells into alginate microspheres is an important aspect of tissue engineering or bioprinting which ensures cell growth and development. We previously demonstrated the encapsulation of stem cells using the hanging drop method. However, this conventional process takes a relatively long time and only produces a small-volume droplet. Here, an experimental approach for alginate emulsification in multistage microfluidics is reported. By using the microfluidic method, the emulsification of alginate in oil can be manipulated by tuning the flow rate for both phases. Two-step droplet emulsification is conducted in a series of polycarbonate and polydimethylsiloxane microfluidic chips. Multistage emulsification of alginate for stem cell encapsulation has been successfully reported in this study under certain flow rates. Fundamental non-dimensional numbers such as Reynolds and capillary are used to evaluate the effect of flow rate on the emulsification process. Reynolds numbers of around 0.5-2.5 for alginate/water and 0.05-0.2 for oil phases were generated in the current study. The capillary number had a maximum value of 0.018 to ensure the formation of plug flow. By using the multistage emulsification system, the flow rates of each process can be tuned independently, offering a wider range of droplet sizes that can be produced. A final droplet size of 500-1000 µm can be produced using flow rates of 0.1-0.5 mL/h and 0.7-2.4 mL/h for the first stage and second stage, respectively.

Mesenchymal stem cells (MSCs) have gained increasing attention in various biomedical applications. However, conventional therapeutic approaches, such as direct intravenous injection, are associated with low cell survival due to the shear force during injection and the oxidative stress microenvironments in the lesion area. Herein, a photo-crosslinkable antioxidant hydrogel based on tyramine- and dopamine-modified hyaluronic acid (HA-Tyr/HA-DA) was developed. Meanwhile, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) were encapsulated in HA-Tyr/HA-DA hydrogel using a microfluidic system to create size-controllable microgels (hUC-MSCs@microgels). The HA-Tyr/HA-DA hydrogel was demonstrated to have good rheology, biocompatibility, and antioxidant properties for cell microencapsulation. The hUC-MSCs encapsulated in microgels showed a high viability and a significantly improved the survival rate under oxidative stress conditions. Therefore, the presented work provides a promising platform for MSCs microencapsulation, which may further improve the stem cell-based biomedical applications.

Navigating the coronavirus disease-2019 (COVID-19, now COVID) pandemic has required resilience and creativity worldwide. Despite early challenges to productivity, more than 2,000 peer-reviewed articles on islet biology were published in 2021. Herein, we highlight noteworthy advances in islet research between January 2021 and April 2022, focussing on 5 areas. First, we discuss new insights into the role of glucokinase, mitogen-activated protein kinase-kinase/extracellular signal-regulated kinase and mitochondrial function on insulin secretion from the pancreatic β cell, provided by new genetically modified mouse models and live imaging. We then discuss a new connection between lipid handling and improved insulin secretion in the context of glucotoxicity, focussing on fatty acid-binding protein 4 and fetuin-A. Advances in high-throughput \"omic\" analysis evolved to where one can generate more finely tuned genetic and molecular profiles within broad classifications of type 1 diabetes and type 2 diabetes. Next, we highlight breakthroughs in diabetes treatment using stem cell-derived β cells and innovative strategies to improve islet survival posttransplantation. Last, we update our understanding of the impact of severe acute respiratory syndrome-coronavirus-2 infection on pancreatic islet function and discuss current evidence regarding proposed links between COVID and new-onset diabetes. We address these breakthroughs in 2 settings: one for a scientific audience and the other for the public, particularly those living with or affected by diabetes. Bridging biomedical research in diabetes to the community living with or affected by diabetes, our partners living with type 1 diabetes or type 2 diabetes also provide their perspectives on these latest advances in islet biology.

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

Mesenchymal stem cells derived from adipose tissue have become a widely investigated cell source to use in tissue engineering applications. However, an optimal delivery scaffold for these cells is still needed. A rapidly gelling, injectable chitosan sponge was proposed in this study as a potential candidate for a suitable delivery scaffold. The results demonstrated the ability to encapsulate the stem cells at a 97.6% encapsulation efficiency and that the cells maintain their viability within the sponge. With the potential of using this scaffold for bone tissue engineering, ALP activity assay and fluorescent imaging for osteocalcin proved the ability to differentiate the encapsulated cells into the osteogenic lineage. Furthermore, co-encapsulation of pyrophosphatase within the sponge was investigated as a method to overcome the inhibitory effects that the sponge degradation by-products have on mineralization. Alizarin Red S staining demonstrated the beneficial effects of adding pyrophosphatase, where a significant increase in mineralization levels was achieved.

Hydrogels derived from decellularized extracellular matrix (ECM) have been widely used as a bioactive matrix for facilitating functional bone tissue regeneration. However, its poor mechanical strength and fast degradation restricts the extensive use for clinical application. Herein, we present a crosslinked decellularized bone ECM (DBM) and fatty acid modified chitosan (oleoyl chitosan, OC) based biohybrid hydrogel (DBM/OC) for delivering human amnion-derived stem cells (HAMSCs) for bone regeneration. DBM/OC hydrogel were benchmarked against collagen-I/OC (Col-I/OC) based hydrogel in terms of their morphological characteristics, rheological analysis, and biological performances. DBM/OC hydrogel with its endogenous growth factors recapitulates the nanofibrillar 3D tissue microenvironment with improved mechanical strength and also exhibited antimicrobial potential along with superior proliferation/differentiation ability. HAMSCs encapsulation potential of DBM/OC hydrogel was established by well spread cytoskeleton morphology post 14 days of cultivation. Further, ex-vivo chick chorioallantoic membrane (CAM) assay revealed excellent neovascularization potential of DBM/OC hydrogel. Subcutaneously implanted DBM/OC hydrogel did not trigger any severe immune response or infection in the host after 21 days. Also, DBM/OC hydrogels and HAMSCs encapsulated DBM/OC hydrogels were implanted at the tibial defect in a rabbit model to assess the bone regeneration ability. Quantitative micro-CT and histomorphological analysis demonstrated that HAMSCs encapsulated DBM/OC hydrogel can support more mature mineralized bone formation at the defect area compared to DBM/OC hydrogel or SHAM. These findings manifested the efficacy of DBM/OC hydrogel as a functional cell-delivery vehicle and osteoinductive template to accelerate bone regeneration.

We previously reported a new approach for micromanipulation and encapsulation of human stem cells using a droplet-based microfluidic device We demonstrated the possibility of encapsulating and culturing difficult-to-preserve primary human hematopoietic stem cells using an engineered double layered bead composed by an inner layer of alginate and an outer layer of puramatrix constructed using a soft technology without the use of any external force. In this work, we use this micro manipulation technique to build a 3D scaffold as a biomimetic model to recapitulate the niche of patient-derived multiple myeloma cells (MM cell) using a multilayered 3D tissue scaffold constructed in a microfluidic device and cultured in 10% FBS culture medium. In the current study, we included the use of this biomimetic model comprising supporting human Mesenchymal stem cells to show the mid-term survival of MM cells in the proposed structures. We found that the generated microniches were suitable for the maintenance of MM cells with and without supporting cells. Additionally, cultured MM cells in droplets were exposed to both Bortezomib and Lenalidomide to test their toxicity in the cultured patient derived cells. Results indicate that the maintained MM cells were consistently responding to the applied medication, opening a wide field of possibilities to use the presented micro device as an ex vivo platform for drug screening.

Enhancements to the mechanical properties of modular designs for bone tissue engineering could increase their clinical applications. In this study, bone marrow mesenchymal stem cells (MSCs) and hydroxyapatite (HAP) microgranules were encapsulated in polyelectrolyte complex membranes composed of chondroitin 4-sulfate (C4S), carboxymethyl cellulose (CMC) and chitosan. Microcapsules were formed with and without HAP microgranules, and cultured in either osteoinduction medium (Osteo) or expansion medium (Exp) to produce four microcapsule conditions: Osteo, Osteo+HAP, Exp, and Exp+HAP. Microcapsules facilitated alkaline phosphatase secretion and deposition of bone specific proteins (osteocalcin and osteopontin) by encapsulated MSCs over 28 days of osteogenic culture. SEM and micro-CT analysis showed cell-deposited mineral covering the surfaces of the HAP microgranules and interior of the microcapsule membrane. The mineralized microcapsules could be combined and fused into cylindrical constructs (4 × 5 mm, W × H), and uniaxial compression tests confirmed that microcapsule mineralization greatly enhanced the yield stresses of Osteo and Osteo+HAP fused constructs (10.4 ± 4.4 MPa and 6.4 ± 2.8 MPa), compared to only HAP microgranules (Exp+HAP, 0.5 ± 0.3 MPa). The C4S/CMC/Chitosan microcapsules provide a platform allowing pre-mineralization of microcapsules in vitro for later assembly of larger load-bearing constructs, or for use as an injectable bone regeneration strategy. STATEMENT OF SIGNIFICANCE: Clinical translation of bone tissue engineering is limited by the difficulty of generating space filling implants that both resist compressive loading, and simultaneously deliver cells throughout the bone defect. Here, we present the design of a microcapsule system containing both stem cells capable of rebuilding bone tissue, and a mechanically tough bone-like mineral, that imparts compression resistance to the microcapsules. The microcapsules support stem cell differentiation to an osteogenic phenotype, that can mineralize the microcapsule membrane and interior. The mineralized microcapsules can be assembled into larger bone constructs, and have mechanical properties on par with trabecular bone.

Protein-based hydrogels have emerged as promising alternatives to synthetic hydrogels for biomedical applications, owing to the precise control of structure and function enabled by protein engineering. Nevertheless, strategies for assembling 3D molecular networks that carry the biological information encoded in full-length proteins remain underdeveloped. Here we present a robust protein gelation strategy based on a pair of genetically encoded reactive partners, SpyTag and SpyCatcher, that spontaneously form covalent isopeptide linkages under physiological conditions. The resulting \"network of Spies\" may be designed to include cell-adhesion ligands, matrix metalloproteinase-1 cleavage sites, and full-length globular proteins [mCherry and leukemia inhibitory factor (LIF)]. The LIF network was used to encapsulate mouse embryonic stem cells; the encapsulated cells remained pluripotent in the absence of added LIF. These results illustrate a versatile strategy for the creation of information-rich biomaterials.