Encapsulation Of Mesenchymal Stem Cells Research Articles

Immunoregulatory potential of mesenchymal stem cells following activation by macrophage-derived soluble factors

BackgroundImmunoregulatory capacity of mesenchymal stem cells (MSC) is triggered by the inflammatory environment, which changes during tissue repair. Macrophages are essential in mediating the inflammatory response after injury and can adopt a range of functional phenotypes, exhibiting pro-inflammatory and anti-inflammatory activities. An accurate characterization of MSC activation by the inflammatory milieu is needed for improving the efficacy of regenerative therapies. In this work, we investigated the immunomodulatory functions of MSC primed with factors secreted from macrophages polarized toward a pro-inflammatory or an anti-inflammatory phenotype. We focused on the role of TNF-α and IL-10, prototypic pro-inflammatory and anti-inflammatory cytokines, respectively, as priming factors for MSC.MethodsSecretion of immunoregulatory mediators from human MSC primed with media conditioned by human macrophages polarized toward a pro-inflammatory or an anti-inflammatory phenotype was determined. Immunomodulatory potential of primed MSC on polarized macrophages was studied using indirect co-cultures. Involvement of TNF-α and IL-10 in priming MSC and of PGE2 in MSC-mediated immunomodulation was investigated employing neutralizing antibodies. Collagen hydrogels were used to study MSC and macrophages interactions in a more physiological environment.ResultsPriming MSC with media conditioned by pro-inflammatory or anti-inflammatory macrophages enhanced their immunomodulatory potential through increased PGE2 secretion. We identified the pro-inflammatory cytokine TNF-α as a priming factor for MSC. Notably, the anti-inflammatory IL-10, mainly produced by pro-resolving macrophages, potentiated the priming effect of TNF-α. Collagen hydrogels acted as instructive microenvironments for MSC and macrophages functions and their crosstalk. Culturing macrophages on hydrogels stimulated anti-inflammatory versus pro-inflammatory cytokine secretion. Encapsulation of MSC within hydrogels increased PGE2 secretion and potentiated immunomodulation on macrophages, attenuating macrophage pro-inflammatory state and sustaining anti-inflammatory activation. Priming with inflammatory factors conferred to MSC loaded in hydrogels greater immunomodulatory potential, promoting anti-inflammatory activity of macrophages.ConclusionsFactors secreted by pro-inflammatory and anti-inflammatory macrophages activated the immunomodulatory potential of MSC. This was partially attributed to the priming effect of TNF-α and IL-10. Immunoregulatory functions of primed MSC were enhanced after encapsulation in hydrogels. These findings may provide insight into novel strategies to enhance MSC immunoregulatory potency.

Encapsulated human mesenchymal stem cells (eMSCs) as a novel anti-cancer agent targeting breast cancer stem cells: Development of 3D primed therapeutic MSCs.

Breast cancer is a leading cause of mortality in women across the globe. The major reason for its recurrence and high mortality is due to the presence of a drug refractory and self-renewing population of cells, the cancer stem cells (CSCs). Mesenchymal stem cells (MSCs) have recently emerged as a promising cell-based therapeutic agent for the treatment of different cancer types. However, the anti-tumor effect of MSCs has been indicated to be substantially reduced by their in vivo tumor-trophic migration property and direct cell-to-cell integration with tumor stromal elements. To address this drawback, the present study uses a biomaterial, sodium alginate, for the encapsulation of MSCs from the perinatal tissue, Wharton's jelly (WJMSCs) into microbeads, to study the effect of WJMSCs beads on breast CSCs derived from two breast cancer cell lines, MDA-MB-231 and MCF7. Encapsulation with sodium alginate facilitated the prevention of direct cell-to-cell interaction and these microbeads provided a three-dimensional (3D) microenvironment for the encapsulated WJMSCs (eWJMSCs). Compared to two dimensional (2D) culture, eWJMSC increased proliferation of WJMSCs with an increase in pluripotency genes, epithelial to mesenchymal transition (EMT), immune-modulation, and angiogenesis. Interestingly, the tumor invasion suppressor protein E-cadherin was highly expressed in eWJMSCs as shown by Western blot analysis. In addition, eWJMSCs had an increased secretion of anti-inflammatory cytokines VEGF, TGF-β, TNF-α, IFN-γ, IL-10 and -6, and IL-3β when compared to 2D culture. Treatment of CSCs with eWJMSCs reduced cell viability, inhibited migration, and exerted an anti-angiogenic effect. eWJMSCs treatment of CSCs increased caspase 3/7 activity, nitric oxide production, and reactive oxygen species production, suggesting its anti-tumorigenic activity. Gene expression analysis revealed that CSCs treated with eWJMSCs had a downregulation of pro-proliferation markers, drug transporters, epithelial-mesenchymal transition-associated markers, and angiogenesis related genes. The mode of anti-proliferative action of WJMSCs beads was possibly through inhibition of the Wnt/β-catenin signaling pathway as indicated by the upregulation of the Wnt antagonists sFRP4 and DKK1. These data suggest that alginate-encapsulated WJMSCs could be an efficient cell contact-free system for developing stem cell-based therapies for CSCs.

Sequential Zonal Chondrogenic Differentiation of Mesenchymal Stem Cells in Cartilage Matrices.

The higher regenerative capacity of fetal articular cartilage compared with the adult is rooted in differences in cell density and matrix composition. We hypothesized that the zonal organization of articular cartilage can be engineered by encapsulation of mesenchymal stem cells in a single superficial zone-like matrix followed by sequential addition of zone-specific growth factors within the matrix, similar to the process of fetal cartilage development. The results demonstrate that the zonal organization of articular cartilage can potentially be regenerated using an injectable, monolayer cell-laden hydrogel with sequential release of growth factors.

Encapsulation of mesenchymal stem cells in glycosaminoglycans-chitosan polyelectrolyte microcapsules using electrospraying technique: Investigating capsule morphology and cell viability.

Polyelectrolyte microcapsules are modular constructs which facilitate cell handling and assembly of cell‐based tissue constructs. In this study, an electrospray (ES) encapsulation apparatus was developed for the encapsulation of mesenchymal stem cells (MSCs). Ionic complexation between glycosaminoglycans (GAGs) and chitosan formed a polyelectrolyte complex membrane at the interface. To optimize the capsules, the effect of voltage, needle size and GAG formulation on capsule size were investigated. It was observed that by increasing the voltage and decreasing the needle size, the capsule size would decrease but at voltages above 12 kV, capsule size distribution broadened significantly which yields lower circularity. Increase in GAG viscosity resulted in larger microcapsules and cell viability exhibited no significant changes during the encapsulation procedure. These results suggest that ES is a highly efficient, and scalable approach to the encapsulation of MSCs for subsequent use in bioprinting and other modular tissue engineering or regenerative medicine applications.

Dual-crosslinked homogeneous alginate microspheres for mesenchymal stem cell encapsulation

A smart hydrogel material was used in combination with custom microfluidic devices (MFDs) to create microspheres for human mesenchymal stem cell (MSC) encapsulation. Methods for fabricating homogeneous stimuli-responsive microspheres for MSC encapsulation and cell delivery have gained interest to increase viability and manipulate microencapsulation within microspheres 10-1000 µm in diameter. Herein, MFDs were combined with non-toxic smart hydrogel materials to tune both the size and mechanics of the microspheres. Traditional hydrogels have a single input/stimulus for crosslinking, utilize potentially toxic ultraviolet radiation, and fail to mimic surrounding musculoskeletal tissue mechanics. Thus, it is highly beneficial to encapsulate MSCs inside a mechanically-stable microsphere made from naturally-derived materials. The objectives of this research were to optimize microsphere fabrication techniques using custom microfluidic devices (MFDs), and to encapsulate viable MSCs within visible-light crosslinked smart-alginate microspheres, with tunable mechanical properties. Microsphere production was characterized optically, and MSC viability, post-encapsulation, was verified using a standard florescence assay. Cell viability was maintained in chemically-modified alginate homogenous microspheres post encapsulation, and after subsequent crosslinking via green light exposure.

Cell encapsulation enhances antidepressant effect of the mesenchymal stem cells and counteracts depressive-like behavior of treatment-resistant depressed rats

Despite the advances in pharmacological therapies, only the half of depressed patients respond to currently available treatment. Thus, the need for further investigation and development of effective therapies, especially those designed for treatment-resistant depression, has been sorely needed. Although antidepressant effects of mesenchymal stem cells (MSCs) have been reported, the potential benefit of this cell therapy on treatment-resistant depression is unknown. Cell encapsulation may enhance the survival rate of grafted cells, but the therapeutic effects and mechanisms mediating encapsulation of MSCs remain unexplored. Here, we showed that encapsulation enhanced the antidepressant effects of MSCs by attenuating depressive-like behavior of Wistar Kyoto (WKY) rats, which are considered as a promising animal model of treatment-resistant depression. The implantation of encapsulated MSCs (eMSCs) into the lateral ventricle counteracted depressive-like behavior and enhanced the endogenous neurogenesis in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus, whereas the implantation of MSCs without encapsulation or the implantation of eMSCs into the striatum did not show such ameliorative effects. eMSCs displayed robust and stable secretion of vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor, fibroblast growth factor-2, and ciliary neurotrophic factor (CNTF), and the implantation of eMSCs into the lateral ventricle activated relevant pathways associated with these growth factors. Additionally, eMSCs upregulated intrinsic expression of VEGF and CNTF and their receptors. This study suggests that the implantation of eMSCs into the lateral ventricle exerted antidepressant effects likely acting via neurogenic pathways, supporting their utility for depression treatment.

Colloidal gelatin microgels with tunable elasticity support the viability and differentiation of mesenchymal stem cells under pro‐inflammatory conditions

Despite a promising potential for mesenchymal stem cells (MSCs) in tissue regeneration, a major challenge in MSC-based therapy has been associated with poor cell survival and low levels of cell integration into host tissue following transplantation. The objective of this study was to develop a gelatin-based colloidal microgel platform that enables the encapsulation of viable MSCs as well as confer fine-tuning of mechanical stiffness and low cytotoxicity. In this study, we report a facile method of fabricating gelatin-based microgel spheres for the encapsulation of MSCs using a water-in-oil mini-emulsification method, which is covalently crosslinked by genipin. At a given seeding cell number, there was a positive correlation between the size of the microsphere and the number of encapsulated MSCs. Controlling the crosslinking degree of gelatin matrix enabled a fine-tuning of mechanical stiffness of gel microsphere. MSCs within softer microgel exhibit more spread morphology than the cells in the stiffer matrix, while cells within stiffer matrix become more elongated morphology. Importantly, we show that the colloidal gelatin microgel could support the viability and differentiation of encapsulated MSCs in a pro-inflammatory environment. This study demonstrates the feasibility of using genipin-crosslinked gelatin gel microspheres as an injectable carrier of MSCs for tissue engineering applications, which can be further explored for MSC-based cell therapy for tissue repair. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2753-2761, 2018.

Transformation of Amorphous Polyphosphate Nanoparticles into Coacervate Complexes: An Approach for the Encapsulation of Mesenchymal Stem Cells.

Inorganic polyphosphate [polyP] has proven to be a promising physiological biopolymer for potential use in regenerative medicine because of its morphogenetic activity and function as an extracellular energy-donating system. Amorphous Ca2+ -polyP nanoparticles [Ca-polyP-NPs] are characterized by a high zeta potential with -34 mV (at pH 7.4). This should contribute to the stability of suspensions of the spherical nanoparticles (radius 94 nm), but make them less biocompatible. The zeta potential decreases to near zero after exposure of the Ca-polyP-NPs to protein/peptide-containing serum or medium plus serum. Electron microscopy analysis reveals that the particles rapidly change into a coacervate phase. Those mats are amorphous, but less stable than the likewise amorphous Ca-polyP-NPs and are morphogenetically active. Mesenchymal stem cells grown onto the polyP coacervate show enhanced growth/proliferation and become embedded in the coacervate. These results suggest that the Ca-polyP coacervate, formed from Ca-polyP-NPs in the presence of protein, can act as an adaptable framework that mimics a niche and provides metabolic energy in bone/cartilage engineering.

Encapsulation of Mesenchymal Stem Cells Improves Vascularization of Alginate-Based Scaffolds.

Vascularization of bioartificial tissues can be significantly enhanced by the generation of an arteriovenous (AV) loop. Besides the surgical vascularization, the choice of the scaffold and the applied cells are indispensable cofactors. The combination of alginate dialdehyde and gelatin (ADA-GEL) and mesenchymal stem cells (MSCs) is a promising approach with regard to biocompatibility, biodegradation, as well as de novo tissue formation. In this study, we targeted the investigation of the vascularization of ADA-GEL with and in the absence of encapsulated MSCs in the AV loop model. A Teflon chamber filled with ADA-GEL microcapsules was placed in the groin of Lewis rats and an AV loop was placed into the chamber. Group A encompassed the ADA-GEL without MSCs, whereas group B contained 2 × 106 DiI-labeled MSCs/mL ADA-GEL. Four weeks postoperatively, tissue formation and vascularization were investigated by histology and microcomputed tomography. We were able to prove vascularization originating from the AV loop in both groups with statistically significant more vessels in group B containing MSCs. Moreover, encapsulated MSCs promoted biodegradation of the ADA-GEL microcapsules. In the present study, we were able to demonstrate for the first time, the successful vascularization of ADA-GEL microcapsules by means of the AV loop. Furthermore, ADA-GEL displayed a good biocompatibility and encapsulation of MSCs into ADA-GEL microcapsule-enhanced vascularization as well as biodegradation.

A MMP7-sensitive photoclickable biomimetic hydrogel for MSC encapsulation towards engineering human cartilage.

Cartilage tissue engineering strategies that use in situ forming degradable hydrogels for mesenchymal stem cell (MSC) delivery are promising for treating chondral defects. Hydrogels that recapitulate aspects of the native tissue have the potential to encourage chondrogenesis, permit cellular mediated degradation, and facilitate tissue growth. This study investigated photoclickable poly(ethylene glycol) hydrogels, which were tailored to mimic the cartilage microenvironment by incorporating extracellular matrix analogs, chondroitin sulfate and RGD, and crosslinks sensitive to matrix metalloproteinase 7 (MMP7). Human MSCs were encapsulated in the hydrogel, cultured up to nine weeks, and assessed by mRNA expression, protein production and biochemical analysis. Chondrogenic genes, SOX9, ACAN, and COL2A1, significantly increased with culture time, and the ratios of COL2A1:COL10A1 and SOX9:RUNX2 reached values of ∼20-100 by week 6. The encapsulated MSCs degraded the hydrogel, which was nearly undetectable by week 9. There was substantial deposition of aggrecan and collagen II, which correlated with degradation of the hydrogel. Minimal collagen X was detectable, but collagen I was prevalent. After week1, extracellular matrix elaboration was accompanied by a ∼twofold increase in compressive modulus with culture time. The MMP7-sensitive cartilage mimetic hydrogel supported MSC chondrogenesis and promoted macroscopic neocartilaginous matrix elaboration representative of fibrocartilage. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2344-2355, 2018.

Encapsulation of mesenchymal stem cells in chitosan/β-glycerophosphate hydrogel for seeding on a novel calcium phosphate cement scaffold

Due to its moldability, biocompatibility, osteoconductivity and resorbability, calcium phosphate cement (CPC) is a highly promising scaffold material for orthopedic applications. However, pH changes and ionic activity during the CPC setting reaction may adversely affect cells seeded directly on CPC. Moreover, a lack of macropores in CPC limits ingrowth of new bone. The objectives of this study were to prepare macroporous CPC scaffolds via porogen leaching, using mannitol crystals as the porogen and to evaluate the in vitro proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) encapsulated in chitosan/β-glycerophosphate (C/GP) hydrogel prior to exposure to the novel CPC scaffold. MSCs were found to be adhered to the surfaces of CPC macropores via scanning electron microscopy. The viability and osteogenic differentiation of MSCs in C/GP hydrogel with or without exposure to CPC constructs containing mannitol crystals indicated that coating with C/GP hydrogel protected the cells during cement mixing and setting. In conclusion, novel, macroporous CPC scaffolds were prepared, and our data indicate that a hydrogel encapsulation-based strategy can be used to protect cells during scaffold formation. Thus, the MSC-laden CPC scaffolds show promise for the delivery of stem cells to promote bone regeneration.

Electromagnetic manipulation enabled calcium alginate Janus microsphere for targeted delivery of mesenchymal stem cells

We prepared Janus microspheres based on sodium alginate for the encapsulation of mesenchymal stem cells (MSC) in one compartment and iron oxide nanoparticles (IONP) or a drug in the second compartment. 4% percent sodium alginate solution was allowed to pass through a septum-theta capillary device and react with 2.5% calcium chloride to allow crosslinking to occur in the solution, forming calcium alginate Janus microspheres. Physico-chemical characterization of microspheres was done by FTIR, TGA, and XRD after loading of stem cells and IONP/drug. The mechanical integrity of microspheres was tested at different time points, which showed that 4% alginate microspheres were mechanically stable for a long period of time. Live/dead staining of MSCs alone and the MTS assay of MSCs and DMSO co-loaded were performed, which showed less toxicity to MSC in the Janus configuration. IONP/MSC-loaded Janus microspheres were tested by magnetic manipulation for targeted MSC delivery for cartilage repair using an electromagnetic manipulation (EMM) device. Janus microspheres can be used for targeted stem cell/drug delivery using EMM for cartilage repair in the near future.

Encapsulated stem cells ameliorate depressive-like behavior via growth factor secretion.

As prevalence of depression continues to rise around the world, there remains a stagnation of available treatments as the affected population grows. The subset of treatment-resistant depression also is on the rise highlighting the need for innovative treatments to address this issue. Mesenchymal stem cells (MSCs) have been reported to attenuate depression-like behaviors, however, the effects of encapsulation of MSCs have yet to be investigated. Encapsulation of MSCs exhibited prolonged survival of exogenous cell injection accompanied with increased secretion of neurotrophic factors including vascular endothelial growth factor, ciliary neurotrophic factor, and others. The enhanced expression of these factors highlights the ability of encapsulated MSCs to upregulate the respective signaling pathways, which are associated with depression pathology and activation of neurogenesis. This treatment identifies a promising therapeutic option for depression, specifically treatment-resistant depression. Further, evaluation of long-term effects of the treatment is warranted. This paper is a review article. Referred literature in this paper has been listed in the references section. The datasets supporting the conclusions of this article are available online by searching various databases including PubMed. Some original themes in this article come from the laboratory practice in our research center and the authors’ experiences.

Triggered Formation of Anionic Hydrogels from Self-Assembling Acidic Peptide Amphiphiles

Peptide amphiphiles represent a growing class of self-assemblers capable of forming a wide array of superstructures that can display targeted function. The electrostatic charge of the amphiphile is an important design attribute that can greatly influence the physical, mechanical, and biological properties of the resultant self-assembled material in which the peptide is contained in high copy number. We have previously reported the design of cationic amphiphiles that assemble into highly positively charged hydrogels. Herein, we report a new class of anionic β-hairpin peptide amphiphiles that undergo pH- and temperature-triggered folding and self-assembly into negatively charged fibrillar hydrogels capable of shear-thin/recovery mechanical behavior. The influence of amino acid composition on material formation, local fibril morphology, and mechanical properties is defined and allowed the iterative design of gels capable of three-dimensional encapsulation of mesenchymal stem cells under physiological conditions.

Encapsulation of allogeneic mesenchymal stem cells in alginate extends local presence and therapeutic function.

Bone marrow derived mesenchymal stem cells (MSCs) have immunomodulatory and trophic capacities. For therapeutic application in local chronic inflammatory diseases, MSCs, preferably of allogeneic origin, have to retain immunomodulatory properties. This might be achieved by encapsulation of MSCs in a biomaterial that protects them from the host immune system. Most studies investigating the properties of MSCs for therapeutic application use short term cultures of cells in monolayer. Since the physical environment of MSCs can influence their functionality, we evaluated the feasibility of preserving the immunomodulatory properties of MSCs encapsulated in a three-dimensional alginate construct. After 5 weeks of implantation in immunocompetent rats, active allogeneic MSCs encapsulated in alginate were still detectable by Bio Luminescence Imaging and Magnetic Resonance Imaging of luciferase transduced and superparamagnetic iron oxide labelled MSCs. MSCs injected in saline were only detectable up to 1 week after injection. Moreover, the MSCs encapsulated in alginate responded to inflammatory stimuli similarly to MSCs in monolayer culture. In addition, MSC-alginate beads secreted immunomodulatory and trophic factors and inhibited T-cell proliferation after 30 d of in vitro culture. Our data indicate that allogeneic MSCs encapsulated in alginate persist locally and could act as an interactive immunomodulatory or trophic factor release system for several weeks, making this an interesting system to investigate for application in inflammatory disease conditions.

Data describing the swelling behavior and cytocompatibility of biodegradable polyelectrolyte hydrogels incorporating poly(L-lysine) for applications in cartilage tissue engineering.

This data article presents data associated with the research article entitled “Evaluation of cell-laden polyelectrolyte hydrogels incorporating poly(L-lysine) for applications in cartilage tissue engineering” (Lam et al., 2016) [1]. Synthetic hydrogel composites fabricated using oligo(poly(ethylene glycol) fumarate) (OPF) macromers were utilized as vehicles for the incorporation of poly(L-lysine) (PLL) as well as the encapsulation of mesenchymal stem cells (MSCs). PLL-laden and PLL-free hydrogels were fabricated to characterize the main and interaction effects of OPF molecular weight, PLL molecular weight, and PLL loading density on the swelling and degradation of synthetic OPF hydrogels. Cells were then encapsulated within such hydrogels for in vitro culture and examined for viability, biochemical activity, and chondrogenic gene expression. These data, which are supplementary to the associated research article (Lam et al., 2016) [1], are presented here.

Effect of mineral organization on mechanical properties of constructs composed of fused and actively mineralized micromodules

Event Abstract Back to Event Effect of mineral organization on mechanical properties of constructs composed of fused and actively mineralized micromodules Kevin B. Miles1, Tristan Maerz2 and Howard W. Matthew1 1 Wayne State University, Chemical Engineering and Materials Science, United States 2 Beaumont Health System – Research Institute, Orthopaedic Research Laboratories, United States Introduction: A modular bone tissue engineering (TE) approach that builds larger, implantable constructs from small cell laden modules could circumvent some pitfalls of traditional bone TE (limited cell migration, inadequate scaffold mineralization, etc.). One modular TE strategy relies on composites of natural polyelectrolytes, such as glycosaminoglycans (GAGs) and chitosan, to construct modular units. Chondroitin 4-sulfate (C4S), the primary GAG in bone, facilitates hydroxyapatite (HAP) nucleation in vitro [1]. In addition, exogenous HAP can stimulate osteogenesis of mesenchymal stem cells (MSCs) [2]. The modular TE design described here involves the encapsulation of mesenchymal stem cells (MSCs) and HAP in a polyelectrolyte membrane composed of C4S and chitosan (Ct) to create micromodular units capable of being fused into larger implantable constructs. The influence of the extent and location of mineral deposition within the micromodules on fused construct mechanical properties is presented here. Methods: HAP and MSCs were encapsulated in spherical C4S/ct micromodules by polyelectrolyte complexation [3]. Four conditions were investigated: micromodules formed without exogenous HAP cultured in standard medium (E) or osteogenic medium (O) for four weeks, and similar micromodules containing HAP microgranules (cultured in standard, EH or osteogenic, OH medium). After 4 weeks of culture, micromodules were fused by the deposition of additional C4S/chitosan polyelectrolyte complex between the micromodules, to create larger fused constructs. The extent and organization of mineral deposition within micromodules/constructs was determined by μCT analysis after 4 weeks of static culture. Yield stresses under uniaxial compression were determined for each construct. Results and Discussion: Complexation between C4S and chitosan was found to adequately fuse mineralized micromodules containing differentiating MSCs (Fig. 1a and 1b). μCT analysis demonstrated that significant mineral deposition occured on the C4S/chitosan membrane enveloping the HAP and osteogenic MSCs (Fig. 1c). Moreover, fused constructs fabricated from micromodules containing osteogenic MSCs (O and OH micromodules) exhibited significantly higher compressive yield points (Fig. 2), compared to micromodules containing standard cultured MSCs (EH and E). Including HAP in the micromodules significantly enhanced the mechanical properties of tissue constructs created from fused micromodules. Interestingly, the location of mineralization was the primary determinant of mechanical properties: constructs composed of actively mineralized micromodules without HAP (O) had significantly higher yield stresses than the non-mineralized constructs containing HAP (EH), possibly due to the localization of mineral deposition to the micromodule C4S/Ct membranes (Fig. 1d). This data strongly suggests that mineralization reinforces the C4S/chitosan membranes, so that compressive stresses are effectively dissipated across the micromodules, resulting in fused constructs with higher compressive strength. Conclusion: The mechanical properties demonstrate that the in vitro mineralization of the C4S/chitosan module membrane is the primary determinant of mechanical properties in the fused constructs. Results show this micromodular unit design can form the basis of a modular TE solution to regenerate mechanically robust bone.

Spatially defined stem cell-laden hydrogel islands for directing endothelial tubulogenesis.

The spatiotemporal coordination of angiogenesis in synthetic materials is important for mimicking natural tissue morphogenesis. Here we report patterned hydrogel encapsulation of mesenchymal stem cells to direct endothelial tubulogenesis in co-culture. Tubulogenesis occurs preferentially over MSC patterns, suggesting this strategy may prove useful in guiding the design of heterotypic engineered tissues.

Mesenchymal stem cell and gelatin microparticle encapsulation in thermally and chemically gelling injectable hydrogels for tissue engineering.

In this work, we investigated the viability and osteogenic differentiation of mesenchymal stem cells encapsulated with gelatin microparticles (GMPs) in an injectable, chemically and thermally gelling hydrogel system combining poly(N-isopropylacrylamide)-based thermogelling macromers containing pendant epoxy rings with polyamidoamine-based hydrophilic and degradable diamine crosslinking macromers. Specifically, we studied how the parameters of GMP size and loading ratio affected the viability and differentiation of cells encapsulated within the hydrogel. We also examined the effects of cell and GMP co-encapsulation on hydrogel mineralization. Cells demonstrated long-term viability within the hydrogels, which was shown to depend on GMP size and loading ratio. In particular, increased interaction of cells and GMPs through greater available GMP surface area, use of an epoxy-based chemical gelation mechanism, and the tunable high water content of the thermogelled hydrogels led to favorable long-term cell viability. Compared with cellular hydrogels without GMPs, hydrogels co-encapsulating cells and GMPs demonstrated greater production of alkaline phosphatase by cells at all time-points and a transient early enhancement of hydrogel mineralization for larger GMPs at higher loading ratios. Such injectable, in situ forming hydrogels capable of delivering and maintaining populations of encapsulated mesenchymal stem cells and promoting mineralization in vitro offer promise as novel therapies for applications in tissue engineering and regenerative medicine.

Process engineering of high voltage alginate encapsulation of mesenchymal stem cells

Encapsulation of stem cells in alginate beads is promising as a sophisticated drug delivery system in treatment of a wide range of acute and chronic diseases. However, common use of air flow encapsulation of cells in alginate beads fails to produce beads with narrow size distribution, intact spherical structure and controllable sizes that can be scaled up. Here we show that high voltage encapsulation (≥15kV) can be used to reproducibly generate spherical alginate beads (200–400μm) with narrow size distribution (±5–7%) in a controlled manner under optimized process parameters. Flow rate of alginate solution ranged from 0.5 to 10ml/h allowed producing alginate beads with a size of 320 and 350μm respectively, suggesting that this approach can be scaled up. Moreover, we found that applied voltages (15–25kV) did not alter the viability and proliferation of encapsulated mesenchymal stem cells post-encapsulation and cryopreservation as compared to air flow. We are the first who employed a comparative analysis of electro-spraying and air flow encapsulation to study the effect of high voltage on alginate encapsulated cells. This report provides background in application of high voltage to encapsulate living cells for further medical purposes. Long-term comparison and work on alginate–cell interaction within these structures will be forthcoming.