Comparative Study of Two Common In Vitro Models for the Pancreatic Islet with MIN6

BACKGROUND

Islet transplantation is currently considered the most promising method for treating insulin-dependent diabetes. The two most-studied artificial islets are alginate-encapsulated β cells or β cell spheroids. As three-dimensional (3D) models, both artificial islets have better insulin secretory functions and transplantation efficiencies than cells in two-dimensional (2D) monolayer culture. However, the effects of these two methods have not been compared yet. Therefore, in this study, cells from the mouse islet β cell line Min6 were constructed as scaffold-free spheroids or alginate-encapsulated dispersed cells.

METHODS

MIN6 cell spheroids were prepared by using Agarose-base microwell arrays. The insulin secretion level was determined by mouse insulin ELISA kit, and the gene and protein expression status of the MIN6 were performed by Quantitative polymerase chain reaction and immunoblot, respectively.

RESULTS

Both 3D cultures effectively promoted the proliferation and glucose-stimulated insulin release (GSIS) of MIN6 cells compared to 2D adherent cells. Furthermore, 1% alginate-encapsulated MIN6 cells demonstrated more significant effects than the spheroids. In general, three pancreatic genes were expressed at higher levels in response to the 3D culture than to the 2D culture, and pancreatic/duodenal homeobox-1 (PDX1) expression was higher in the cells encapsulated in 1% alginate than that in the spheroids. A western blot analysis showed that 1% alginate-encapsulated MIN6 cells activated the phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase (AKT)/forkhead transcription factor FKHR (FoxO1) pathway more than the spheroids, 0.5% alginate-, or 2% alginate-encapsulated cells did. The 3D MIN6 culture, therefore, showed improved effects compared to the 2D culture, and the 1% alginate-encapsulated MIN6 cells exhibited better effects than the spheroids. The upregulation of PDX1 expression through the activation of the PI3K/AKT/FoxO1 pathway may mediate the improved cell proliferation and GSIS in 1% alginate-encapsulated MIN6 cells.

CONCLUSION

This study may contribute to the construction of in vitro culture systems for pancreatic islets to meet clinical requirements.

Quality evaluation of cell spheroids for transplantation by monitoring oxygen consumption using an on-chip electrochemical device

Three-dimensional cell spheroids are superior cell-administration form for cell-based therapy which generally exhibit superior functionality and long-term survival after transplantation. Here, we nondestructively measured the oxygen consumption rate of cell spheroids using an on-chip electrochemical device (OECD) and examined whether this rate can be used as a marker to estimate the quality of cell spheroids. Cell spheroids containing NanoLuc luciferase-expressing mouse mesenchymal stem cell line C3H10T1/2 (C3H10T1/2/Nluc) were prepared. Spheroids of high or low quality were prepared by altering the medium change frequency. After transplantation into mice, the high-quality C3H10T1/2/Nluc spheroids exhibited a higher survival rate than the low-quality ones. The oxygen consumption rate of the high-quality C3H10T1/2/Nluc spheroids was maintained at high levels, whereas that of the low-quality spheroids decreased with time. These results indicate that OECD-based measurement of the oxygen consumption rate can be used to estimate the quality of cell spheroids without destructive analysis of the spheroids.

Enhanced angiogenic potential of adipose-derived stem cell sheets by integration with cell spheroids of the same source

Background

Adipose-derived stem cell (ASC) has been considered as a desirable source for cell therapy. In contrast to combining scaffold materials with cells, ASCs can be fabricated into scaffold-free three-dimensional (3D) constructs to promote regeneration at tissue level. However, previous reports have found decreased expression of vascular endothelial growth factor (VEGF) in ASC sheets. In this study, we aimed to integrate ASC spheroids into ASC sheets to enhance the angiogenic capability of cell sheets.

Methods

ASCs were seeded in agarose microwells to generate uniform cell spheroids with adjustable size, while extracellular matrix deposition could be stimulated by ascorbic acid 2-phosphate to form ASC sheets. RNA sequencing was performed to identify the transcriptomic profiles of ASC spheroids and sheets relative to monolayer ASCs. By transferring ASC spheroids onto ASC sheets, the spheroid sheet composites could be successfully fabricated after a short-term co-culture, and their angiogenic potential was evaluated in vitro and in ovo.

Results

RNA sequencing analysis revealed that upregulation of angiogenesis-related genes was found only in ASC spheroids. The stimulating effect of spheroid formation on ASCs toward endothelial lineage was demonstrated by enhanced CD31 expression, which maintained after ASC spheroids were seeded on cell sheets. Relative to ASC sheets, enhanced expression of VEGF and hepatocyte growth factor was also noted in ASC spheroid sheets, and conditioned medium of ASC spheroid sheets significantly enhanced tube formation of endothelial cells in vitro. Moreover, chick embryo chorioallantoic membrane assay showed a significantly higher capillary density with more branch points after applying ASC spheroid sheets, and immunohistochemistry also revealed a significantly higher ratio of CD31-positive area.

Conclusion

In the spheroid sheet construct, ASC spheroids can augment the pro-angiogenesis capability of ASC sheets without the use of exogenous biomaterial or genetic manipulation. The strategy of this composite system holds promise as an advance in 3D culture technique of ASCs for future application in angiogenesis and regeneration therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02948-3.

Substrate coated with autologous decellularized extracellular matrix facilitates in vitro spreading of spheroid from adipose-derived stem cells through regulating ERK1/2-MMP2/9 pathway

Adipose-derived stem cells (ADSCs) are easily available and play an important role in regenerative medicine. In recent years, Cell spheroid models have been in the spotlight because of their various advantages and physiological proximity. Promoting the spreading of ADSCs spheroids may improve the therapeutic effect the transplanted ADSCs. In this study, we prepared autologous decellularized extracellular matrix (d-ECM) and ADSCs spheroids, and investigated in vitro spreading of the spheroids on the d-ECM-coated substrate. In addition, the effect of d-ECM powder (ECM-P) on the aggregation of ADSCs was analyzed in a three-dimensional (3D) culture system. The results showed that d-ECM accelerated the spreading of spheroids, and promoted the migration and proliferation of the surrounding monolayer cells, accompanied by ERK1/2 activation and an increase in the expression of MMP2 and MMP9. In addition, ECM-P facilitated the aggregation of free cells in 3D culture in a concentration-dependent way. The spheroid spreading and cell aggregation were both prevented by ERK1/2 selective inhibitor PD98059. Our data suggest that the d-ECM substrate and its derivant may regulate the transformation between ADSCs spheroids and the monolayer or free cells, and ERK1/2 signalling pathway may be involved in these processes.

Tissue mimetic hyaluronan bioink containing collagen fibers with controlled orientation modulating cell migration and alignment

Biofabrication is providing scientists and clinicians the ability to produce engineered tissues with desired shapes and gradients of composition and biological cues. Typical resolutions achieved with extrusion-based bioprinting are at the macroscopic level. However, for capturing the fibrillar nature of the extracellular matrix (ECM), it is necessary to arrange ECM components at smaller scales, down to the micron and the molecular level. Herein, we introduce a bioink containing the tyramine derivative of hyaluronan (HA; henceforth known as THA) and collagen (Col) type 1. In this bioink, similar to connective tissues, Col is present in the fibrillar form, and HA functions as a viscoelastic space filler. THA was enzymatically cross-linked under mild conditions allowing simultaneous Col fibrillogenesis, thus achieving a homogeneous distribution of Col fibrils within the viscoelastic HA-based matrix. The THA-Col composite displayed synergistic properties in terms of storage modulus and shear thinning, translating into good printability. Shear-induced alignment of the Col fibrils along the printing direction was achieved and quantified via immunofluorescence and second-harmonic generation. Cell-free and cell-laden constructs were printed and characterized, analyzing the influence of the controlled microscopic anisotropy on human bone marrow-derived mesenchymal stromal cell (hMSC) migration. Anisotropic HA-Col showed cell-instructive properties modulating hMSC adhesion, morphology, and migration from micropellets stimulated by the presence and the orientation of Col fibers. Actin filament staining showed that hMSCs embedded in aligned constructs displayed increased cytoskeleton alignment along the fibril direction. Based on gene expression of cartilage/bone markers and ECM production, hMSCs embedded in the isotropic bioink displayed chondrogenic differentiation comparable with standard pellet culture by means of proteoglycan production (safranin O staining and proteoglycan quantification). The possibility of printing matrix components with control over microscopic alignment brings biofabrication one step closer to capturing the complexity of native tissues.

Enzymatic outside-in cross-linking enables single-step microcapsule production for high-throughput three-dimensional cell microaggregate formation

Cell-laden hydrogel microcapsules enable the high-throughput production of cell aggregates, which are relevant for three-dimensional tissue engineering and drug screening applications. However, current microcapsule production strategies are limited by their throughput, multistep protocols, and limited amount of compatible biomaterials. We here present a single-step process for the controlled microfluidic production of single-core microcapsules using enzymatic outside-in cross-linking of tyramine-conjugated polymers. It was hypothesized that a physically, instead of the conventionally explored biochemically, controlled enzymatic cross-linking process would improve the reproducibility, operational window, and throughput of shell formation. Droplets were flown through a silicone delay line, which allowed for highly controlled diffusion of the enzymatic cross-linking initiator. The microcapsules' cross-linking density and shell thickness is strictly depended on the droplet's retention time in the delay line, which is predictably controlled by flow rate. The here presented hydrogel cross-linking method allows for facile and cytocompatible production of cell-laden microcapsules compatible with the formation and biorthogonal isolation of long-term viable cellular spheroids for tissue engineering and drug screening applications.

Fabrication of core-shell spheroids as building blocks for engineering 3D complex vascularized tissue

Cell spheroids as building blocks for engineering micro-tissue should be able to mimic the complex structure of natural tissue. However, control of the distribution of multiple cell populations within cell spheroids is difficult to achieve with current spheroid-harvest methods such as hanging-drop and with the use of microwell plates. In this study, we report the fabrication of core-shell spheroids with the ultimate goal to form 3D complex micro-tissue. We used endothelial cells and two types of stem cells (human turbinate mesenchymal stem cells (hTMSCs)/adipose-derived stem cells (ADSCs)). The stem cells and endothelial cells formed layered micro-sized cell sheets (µCSs) on polydopamine micro-patterned temperature-responsive hydrogel surfaces by a sequential seeding method, and these layered µCSs self-assembled to form core-shell spheroids by expansion of the hydrogels. The co-cultured spheroids formed a core-shell structure irrespective of stem cell type. In addition, the size of the core-shell spheroids was controlled from 90 ± 1 to 144 ± 3 µm by changing pattern sizes (200, 300, and 400 µm). The shell thickness gradually increased from 12 ± 3 to 30 ± 6 µm by adjusting the endothelial cell seeding density. Finally, we fabricated the micro-tissue by fusion of the co-cultured spheroids, and the spheroids with the core-shell structure rapidly induced in vitro vessel-like network in 3 days. Thus, the position of endothelial cells in co-cultured spheroids may be an important factor for the modulation of the vascularization process, which can be useful for the production of 3D complex micro-tissues using spheroids as building blocks. STATEMENT OF SIGNIFICANCE: This manuscript describes our work on the fabrication of core-shell spheroids as building blocks to form 3D complex vascularized micro-tissue. Stem cells (human turbinate mesenchymal stem cells (hTMSCs) or adipose-derived stem cells (ADSCs)) and endothelial cells formed layered micro-sized cell sheets (µCSs) on micro-patterned temperature-responsive hydrogel surfaces by a sequential seeding method, and these layered µCSs self-assembled to form core-shell spheroids (core - stem cells, shell - endothelial cells), irrespective of stem cell type. In addition, the size and shell thickness of the core-shell spheroids were controlled by modifying pattern size and endothelial cell seeding density. We fabricated the vascularized micro-tissue by fusion of the spheroids and demonstrated that the spheroids with a core-shell structure rapidly induced vessel-like network.

MicroRNA-205-5p inhibits three-dimensional spheroid proliferation of ErbB2-overexpressing breast epithelial cells through direct targeting of CLCN3

We previously reported that microRNA-205-5p (miR-205-5p) is significantly decreased in the ErbB2-overexpressing breast epithelial cell line MCF10A-ErbB2 compared with control cells. In this study, we identified a direct target of miR-205-5p, chloride voltage-gated channel 3 (CLCN3). CLCN3 expression was induced by ErbB2 overexpression; this induced expression was then reduced to control levels by the transfection of the miR-205-5p precursor. In RNA-binding protein immunoprecipitation with Ago1/2/3 antibody, CLCN3 was significantly enriched in 293T embryonic kidney cells with miR-205-5p mimic transfection compared with negative control mimic transfection. In luciferase reporter assays using CLCN3 3'-UTR constructs, the miR-205-5p mimic significantly decreased reporter activity of both wild-type and partial mutant constructs in MCF10A-ErbB2 cells. In contrast, no inhibitory effects of the miR-205-5p mimic were detected using the complete mutant constructs. Since miR-205-5p expression in exosomes derived from MCF10A-neo cells was substantially higher than in exosomes derived from MCF10A-ErbB2 cells, we next investigated whether an exosome-mediated miR-205-5p transfer could control CLCN3 expression. To this end, exosomal miR-205-5p derived from MCF10A-neo cells was functionally transferred to MCF10A-ErbB2 cells, which served to decrease the expression of CLCN3. To assess the roles of CLCN3 in breast cancer, we next performed three-dimensional (3D) spheroid proliferation analyses using MCF10A-ErbB2 cells treated with MCF10A-neo-derived exosomes or CLCN3 shRNA stably expressing SKBR3 and MDA-MB-453 breast cancer cells. Our results showed that both treatment with MCF10A-neo-derived exosome and CLCN3 shRNA expression suppressed 3D spheroid proliferation. Collectively, these novel findings suggest that CLCN3 may be a novel direct target of miR-205-5p and this CLCN3/miR-205-5p interaction may serve a pivotal role in regulating breast cancer cellular proliferation under physiological conditions.

3D multicellular model of shock wave-cell interaction

Understanding the interaction between shock waves and tissue is critical for advancing the use of shock waves for medical applications, such as cancer therapy. This work aims to study shock wave-cell interaction in a more realistic environment, relevant to in vitro and in vivo studies, by using 3D computational models of healthy and cancerous cells. The results indicate that for a single cell embedded in an extracellular environment, the cellular geometry does not influence significantly the membrane strain but does influence the von Mises stress. On the contrary, the presence of neighbouring cells has a strong effect on the cell response, by increasing fourfold both quantities. The membrane strain response of a cell converges with more than three neighbouring cell layers, indicating that a cluster of four layers of cells is sufficient to model the membrane strain in a large domain of tissue. However, a full 3D tissue model is needed if the stress evaluation is of main interest. A tumour mimicking multicellular spheroid model is also proposed to study mutual interaction between healthy and cancer cells and shows that cancer cells can be specifically targeted in an early stage tumour-mimicking environment.

STATEMENT OF SIGNIFICANCE

This work presents 3D computational models of shock-wave/cell interaction in a biophysically realistic environment using real cell morphology in tissue-mimicking phantoms and multicellular spheroids. Results show that cell morphology does not strongly influence the membrane strain but influences the von Mises stress. While the presence of neighbouring cells significantly increases the cell response, four cell layers are enough to capture the membrane strain change in tissue. However, a full tissue model is necessary if accurate stress analysis is needed. The work also shows that cancer cells can be specifically targeted in early stage tumour mimicking environment. This work is a step towards realistic modelling of shock-wave/cell interactions in tissues and provides insight on the use of 3D models for different scenarios.

Bone marrow-derived stem/stromal cells (BMSC) 3D microtissues cultured in BMP-2 supplemented osteogenic induction medium are prone to adipogenesis

Bone marrow-derived mesenchymal stem/stromal cells (BMSC) may facilitate bone repair through secretion of factors that stimulate endogenous repair processes or through direct contribution to new bone through differentiation into osteoblast-like cells. BMSC microtissue culture and differentiation has been widely explored recently, with high-throughput platforms making large-scale manufacture of microtissues increasingly feasible. Bone-like BMSC microtissues could offer an elegant method to enhance bone repair, especially in small-volume non-union defects, where small diameter microtissues could be delivered orthoscopically. Using a high-throughput microwell platform, our data demonstrate that (1) BMSC in 3D microtissue culture result in tissue compaction, rather than growth, (2) not all mineralised bone-like matrix is incorporated in the bulk microtissue mass and (3) a significant amount of lipid vacuole formation is observed in BMSC microtissues exposed to BMP-2. These factors should be considered when optimising BMSC osteogenesis in microtissues or developing BMSC microtissue-based therapeutic delivery processes.

Physicochemical properties of ionic and non-ionic biocompatible hydrogels in water and cell culture conditions: Relation with type of morphologies of bovine fetal fibroblasts in contact with the surfaces

Cationic, anionic and non-ionic hydrogels having acrylamide polymer backbones were synthesized via free radical polymerization with N,N-methylenebisacrylamide (BIS) as crosslinker. The chemical structures of the hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Physicochemical properties such as swelling kinetic, maximum swelling capacity, volume phase transition temperature (VPTT) and wettability (static water contact angle) of hydrogels swollen in aqueous and cell culture medium, at room and cell culture temperatures were studied. In order to correlate the surface properties of the hydrogels and cellular adhesivity of bovine fetal fibroblasts (BFFs), cellular behaviour was analyzed by inverted fluorescence optical microscopy and atomic force microscopy (AFM). MTT assay demonstrated that the number of viable cells in contact with hydrogels does not significantly change in comparison to a control surface. Flattened and spindle-shaped cells and cell spheroids were the adopted morphologies during first days of culture on different hydrogels. Cell spheroids were easily obtained during the first 5days of culture in contact with PNIPAM-co-20%HMA (poly (N-isopropylacrylamide-co-20%N-acryloyl-tris-(hydroxymethyl)aminomethane)) hydrogel surface. After 15days of culture all hydrogels showed high adhesion and visual proliferation. According to obtained results, non-ionic and hydrophilic surfaces with moderated wettability induce the formation of BFFs cell spheroids. These hydrogel surfaces could be used in clinical and biochemical treatments at laboratory level to cell growth and will allow generating the base for future biotechnologic platform.