Spatiotemporal pharmacometabolomics based on ambient mass spectrometry imaging to evaluate the metabolism and hepatotoxicity of amiodarone in HepG2 spheroids

Three-dimensional(3D)cell spheroid models combined with mass spectrometry imaging(MSI)enables innovative investigation of in vivo-like biological processes under different physiological and pathological conditions.Herein,airflow-assisted desorption electrospray ionization-MSI(AFADESI-MSI)was coupled with 3D HepG2 spheroids to assess the metabolism and hepatotoxicity of amiodarone(AMI).High-coverage imaging of>1100 endogenous metabolites in hepatocyte spheroids was achieved using AFADESI-MSI.Following AMI treatment at different times,15 metabolites of AMI involved in Ndesethylation,hydroxylation,deiodination,and desaturation metabolic reactions were identified,and according to their spatiotemporal dynamics features,the metabolic pathways of AMI were proposed.Subsequently,the temporal and spatial changes in metabolic disturbance within spheroids caused by drug exposure were obtained via metabolomic analysis.The main dysregulated metabolic pathways included arachidonic acid and glycerophospholipid metabolism,providing considerable evidence for the mechanism of AMI hepatotoxicity.In addition,a biomarker group of eight fatty acids was selected that provided improved indication of cell viability and could characterize the hepatotoxicity of AMI.The combination of AFADESI-MSI and HepG2 spheroids can simultaneously obtain spatiotemporal information for drugs,drug metabolites,and endogenous metabolites after AMI treatment,providing an effective tool for in vitro drug hepatotoxicity evaluation.

3D （Three-Dimensional） Caco-2 Spheroids： Optimized in vitro Protocols to Favor Their Differentiation Process and to Analyze Their Cell Growth Behavior

3D （Three-dimensional） Caco-2 spheroids closely recapitulating in vivo physiological organization of intestinal epithelial cells, provide an excellent in vitro model system to study their pathophysiology and their response to stressful stimuli. The objective of this technical note is to provide optimized in vitro experimental protocols for culturing 3D Caco-2 spheroids and for analyzing their cell growth features. An optimized 3D Caco-2 spheroid culturing technique based on a new configuration of the culture medium is provided A methodological approach to determine the distribution of the cell cycle phases in disaggregated Caco-2 spheroids by using cytofluorimetric analysis is also described. The optimized culturing protocol favors 3D Caco-2 spheroid differentiation process, as evaluated by the number of well-differentiated spheroids with a single hollow lumen. The cytofluorimetric analysis allows rapid collection of cell cycle phase data from high numbers of spheroid samples, thus, permitting to estimate their growth dynamics in a relatively short time. The optimized technical approaches described here can be applied in systematic manner to a variety of research activities utilizing 3D Caco-2 spheroids. Ease of use, time and economic saving advantages deriving from these protocols further highlight their potential.

Bioprinting-Based High-Throughput Fabrication of Three-Dimensional MCF-7 Human Breast Cancer Cellular Spheroids

Cellular spheroids serving as three-dimensional(3D) in vitro tissue models have attracted increasing interest for pathological study and drug-screening applications. Various methods, including microwells in particular, have been developed for engineering cellular spheroids. However, these methods usually suffer from either destructive molding operations or cell loss and non-uniform cell distribution among the wells due to two-step molding and cell seeding. We have developed a facile method that utilizes cellembedded hydrogel arrays as templates for concave well fabrication and in situ MCF-7 cellular spheroid formation on a chip. A custom-built bioprinting system was applied for the fabrication of sacrificial gelatin arrays and sequentially concave wells in a high-throughput, flexible, and controlled manner. The ability to achieve in situ cell seeding for cellular spheroid construction was demonstrated with the advantage of uniform cell seeding and the potential for programmed fabrication of tissue models on chips. The developed method holds great potential for applications in tissue engineering, regenerative medicine, and drug screening.

Changes of cell membrane fluidity for mesenchymal stem cell spheroids on biomaterial surfaces

BACKGROUND The therapeutic potential of mesenchymal stem cells(MSCs)in the form of threedimensional spheroids has been extensively demonstrated.The underlying mechanisms for the altered cellular behavior of spheroids have also been investigated.Cell membrane fluidity is a critically important physical property for the regulation of cell behavior,but it has not been studied for the spheroid-forming cells to date.AIM To explore the association between cell membrane fluidity and the morphological changes of MSC spheroids on the surface of biomaterials to elucidate the role of membrane fluidity during the spheroid-forming process of MSCs.METHODS We generated three-dimensional(3D)MSC spheroids on the surface of various culture substrates including chitosan(CS),CS-hyaluronan(CS-HA),and polyvinyl alcohol(PVA)substrates.The cell membrane fluidity and cell morphological change were examined by a time-lapse recording system as well as a highresolution 3D cellular image explorer.MSCs and normal/cancer cells were prestained with fluorescent dyes and co-cultured on the biomaterials to investigate the exchange of cell membrane during the formation of heterogeneous cellular spheroids.RESULTS We discovered that vesicle-like bubbles randomly appeared on the outer layer of MSC spheroids cultured on different biomaterial surfaces.The average diameter of the vesicle-like bubbles of MSC spheroids on CS-HA at 37℃ was approximately 10μm,smaller than that on PVA substrates(approximately 27μm).Based on time-lapse images,these unique bubbles originated from the dynamic movement of the cell membrane during spheroid formation,which indicated an increment of membrane fluidity for MSCs cultured on these substrates.Moreover,the membrane interaction in two different types of cells with similar membrane fluidity may further induce a higher level of membrane translocation during the formation of heterogeneous spheroids.CONCLUSION Changes in cell membrane fluidity may be a novel path to elucidate the complicated physiological alterations in 3D spheroid-forming cells.

Cartilage and bone tissue engineering using adipose stromal/stem cells spheroids as building blocks

Scaffold-free techniques in the developmental tissue engineering area are designed to mimic in vivo embryonic processes with the aim of biofabricating,in vitro,tissues with more authentic properties.Cell clusters called spheroids are the basis for scaffold-free tissue engineering.In this review,we explore the use of spheroids from adult mesenchymal stem/stromal cells as a model in the developmental engineering area in order to mimic the developmental stages of cartilage and bone tissues.Spheroids from adult mesenchymal stromal/stem cells lineages recapitulate crucial events in bone and cartilage formation during embryogenesis,and are capable of spontaneously fusing to other spheroids,making them ideal building blocks for bone and cartilage tissue engineering.Here,we discuss data from ours and other labs on the use of adipose stromal/stem cell spheroids in chondrogenesis and osteogenesis in vitro.Overall,recent studies support the notion that spheroids are ideal"building blocks"for tissue engineering by“bottom-up”approaches,which are based on tissue assembly by advanced techniques such as three-dimensional bioprinting.Further studies on the cellular and molecular mechanisms that orchestrate spheroid fusion are now crucial to support continued development of bottom-up tissue engineering approaches such as three-dimensional bioprinting.

Unexpected Occurrence of Fetal Hemophagocytic Syndrome in a Patient with Hereditary Diffuse Leukoencephalopathy with Spheroids

Colony stimulating factor-1 receptor (CSF1R) plays important roles in the differentiation and proliferation of macrophage and microglia in systemic organs and the brain. A genetic defect in CSF1R causes hereditary diffuse leukoencephalopathy with spheroids (HDLS). HDLS mainly affects the cerebral white matter and shows pre-senile cognitive decline, motor disturbance, and epilepsy. However, systemic manifestations outside the brain have not yet been described in patients with HDLS. Here, we report the case of a 41-year-old man with HDLS carrying the p. K793T mutation in CSF1R, who unexpectedly died of sepsis and hemophagocytic syndrome shortly after the onset of HDLS. The fetal sequence of sepsis and hemophagocytic syndrome was triggered by enterocolitis. An autopsy revealed that focal inflammation in the intestine had almost resolved. Most strikingly, massive infiltration of cluster of differentiation (CD) 68- and CD163-immunopositive macrophages with hemophagocytosis was observed in the bone marrow, spleen, and liver. Less abundant infiltration of CD68- and CD204-immunopositive macrophages without hemophagocytosis was also seen in the lung and intestine. At present, the pathogenetic link between CSF1R mutation and hemophagocytic syndrome in this patient is unclear. Our case, however, clearly shows that even in patients with HDLS, aberrant activation of functional macrophages can be induced under certain conditions in visceral organs.

Characterization of three-dimensional multipotent adipose-derived stem cell spheroids

Human adipose stem cells(hADSCs)are reliable sources for cell therapy.However,the clinical applications are limited by the decrease in activity during in vitro culture.We used a knockout serum replacement(KSR)medium,Eppendorf(EP)tube culture,and a simulated microgravity(SMG)culture system to establish hADSC spheroids.We found that hADSCs aggregated and formed spheroids in the KSR culture medium.The EP tube culture method revealed many biological cell characteristics,such as good cell viabilities,rough surfaces,polar growth,fusion phenomenon,and injectability.The findings show its advantages for hADSCs spherical cultures.When cultured in SMG,hADSC spheroids produced large-scale spheroids.Additionally,confocal examination and viability assays revealed that SMG-cultured hADSC spheroids had higher cell viabilities and looser spherical structures,relative to those cultured in EP tubes.hADSC spheroids in static EP tube culture had tighter structures and more dead cells with rough and irregular surfaces,while hADSC spheroids in dynamic SMG condition exhibited looser structures and better cell viabilities with flat and regular surfaces.Therefore,the KSR media promotes spherical formation by hADSCs,which showed polar growth,fusion,and injectability in vitro.The dynamic SMG culture enhances the formation of a looser structure and better cell viabilities for hADSC spheroids.

Formation Mechanism of Reduction Spheroids with Dark Cores in Cretaceous Red Beds in Jiaolai Basin, China

Red beds are not entirely red sometimes, in which grey-green spheroids or irregular spots can be found. However, the formation mechanism of grey-green spheroids or irregular spots in red beds is not clear so far. Samples taken from well JK1 in Jiaozhou area of Jiaolai Basin displayed that the reduction spheroids have more Vanadium (V) element, less TFe3O4 and Lead (Pb) element, almost the same content of other elements such as FeO and so on, comparing the red parts of the samples. The existence of organisms can explain the existence of green reductive spheres in the red beds formed under the oxidation environment.

Artificial Equilibrium Points in the Low-Thrust Restricted Three-Body Problem When Both the Primaries Are Oblate Spheroids

This paper studies the existence and stability of the artificial equilibrium points (AEPs) in the low-thrust restricted three-body problem when both the primaries are oblate spheroids. The artificial equilibrium points (AEPs) are generated by canceling the gravitational and centrifugal forces with continuous low-thrust at a non-equilibrium point. Some graphical investigations are shown for the effects of the relative parameters which characterized the locations of the AEPs. Also, the numerical values of AEPs have been calculated. The positions of these AEPs will depend not only also on magnitude and directions of low-thrust acceleration. The linear stability of the AEPs has been investigated. We have determined the stability regions in the xy, xz and yz-planes and studied the effect of oblateness parameters A1(0A1?and ?A2(0A2<1) on the motion of the spacecraft. We have found that the stability regions reduce around both the primaries for the increasing values of oblateness of the primaries. Finally, we have plotted the zero velocity curves to determine the possible regions of motion of the spacecraft.

MALDI coupled with laser-postionization and trapped ion mobility spectrometry contribute to the enhanced detection of lipids in cancer cell spheroids

Cancer cell spheroids(CCS) are a valuable three-dimensional cell model in cancer studies because they could replicate numerous characteristics of solid tumors. Increasing researches have used matrix-assisted laser desorption/ionization mass spectrometry imaging(MALDI-MSI) to investigate the spatial distribution of endogenous compounds(e.g., lipids) in CCS. However, only limited lipid species can be detected owing to a low ion yield by using MALDI. Besides, it is still challenging to fully characterize the structural diversity of lipids due to the existence of isomeric/isobaric species. Here, we carried out the initial application of MALDI coupled with laser-postionization(MALDI-2) and trapped ion mobility spectrometry(TIMS) imaging in HCT116 colon CCS to address these challenges. We demonstrated that MALDI-2 is capable of detecting more number and classes of lipids in HCT116 colon CCS with higher signal intensities than MALDI. TIMS could successfully separate numerous isobaric/isomeric species of lipids in CCS. Interestingly, we found that some isomeric/isobaric species have totally different spatial distributions in colon CCS. Further MS/MS imaging analysis was employed to determine the compositions of fatty acid chains for isomeric species by examining disparities in signal intensities and spatial distributions of product ions. This work stresses the robust ability of TIMS and MALDI-2 imaging in analyzing endogenous lipids in CCS, which could potentially become powerful tools for future cancer studies.

In situ biosynthesis of bacterial cellulose hydrogel spheroids with tunable dimensions

Bacterial cellulose(BC)hydrogel spheroid plays a significant role in diverse fields due to its spatial 3D structure and properties.In the present work,a series of BC spheroids with controllable size and shape was obtained via an in situ biosynthesis.Crucial factors for fabricating BC spheroid in-cluding inoculum concentration of 1.35×10^(3)CFU/mL,shaking speeds at 100 r/min,and 48-96 h incubation time during the biosynthetic process,were comprehensively established.An operable mechanism model for tuning the size of BC spheroids from 0.4 to 5.0 mm was proposed with a fresh feeding medium strategy of dynamic culture.The resulting BC spheroids exhibit an inter-active 3D network of nanofibers,a crystallinity index of 72.3%,a specific surface area of 91.2 m^(2)/g,and good cytocompatibility.This study reinforces the understanding of BC spheroid forma-tion and explores new horizons for the design of BC spheroids-derived functional matrix materials for medical care.

Magnetic hydroxyapatite nanobelt-stem cell hybrid spheroids for remotely patterning bone tissues

The low survival rate and poor differentiation efficiency of stem cells,as well as the insufficient integration of implanted stem cells,limit the regeneration of bone defects.Here,we have developed magnetic ferroferric oxidehydroxyapatitepolydopamine(Fe3O4-HAp-PDA)nanobelts to assemble mesenchymal stem cells(MSCs)into a three-dimensional hybrid spheroid for patterning bone tissue.These nanobelts,which are featured by their highaspect ratio and contain Fe3O4 nanospheres with a PDA coating,can be manipulated by a magnetic field and foster enhanced cell-nanobelt interactions.This strategy has been demonstrated to be effective for both bone marrow mesenchymal stem cells and adipose-derived mesenchymal stem cells,enabling remote manipulation of stem cell spheroids and efficient spheroid fusion,which in turn accelerates osteogenic differentiation.Consequently,this methodology serves as an efficient and general tool for bone tissue printing and can potentially overcome the low survival rate and poor differentiation efficiency of stem cells,as well as mismatched interface fusion issues.

Extracellular magnetic labeling of biomimetic hydrogel-induced human mesenchymal stem cell spheroids with ferumoxytol for MRI tracking

Labeling of mesenchymal stem cells(MSCs)with superparamagnetic iron oxide nanoparticles(SPIONs)has emerged as a potential method for magnetic resonance imaging(MRI)tracking of transplanted cells in tissue repair studies and clinical trials.Labeling of MSCs using clinically approved SPIONs(ferumoxytol)requires the use of transfection reagents or magnetic field,which largely limits their clinical application.To overcome this obstacle,we established a novel and highly effective method for magnetic labeling of MSC spheroids using ferumoxytol.Unlike conventional methods,ferumoxytol labeling was done in the formation of a mechanically tunable biomimetic hydrogel-induced MSC spheroids.Moreover,the labeled MSC spheroids exhibited strong MRI T2 signals and good biosafety.Strikingly,the encapsulated ferumoxytol was localized in the extracellular matrix(ECM)of the spheroids instead of the cytoplasm,minimizing the cytotoxicity of ferumoxytol and maintaining the viability and stemness properties of biomimetic hydrogel-induced MSC spheroids.This demonstrates the potential of this method for post-transplantation MRI tracking in the clinic.

Multicellular tumor spheroids bridge the gap between two-dimensional cancer cells and solid tumors: The role of lipid metabolism and distribution

Previous studies demonstrated that three-dimensional(3D) multicellular tumor spheroids(MCTS) could more closely mimic solid tumors than two-dimensional(2D) cancer cells in terms of the spatial structure, extracellular matrix-cell interaction, and gene expression pattern. However, no study has been reported on the differences in lipid metabolism and distribution among 2D cancer cells, MCTS, and solid tumors. Here, we used Hep G2 liver cancer cell lines to establish these three cancer models. The variations of lipid profiles and spatial distribution among them were explored by using mass spectrometry-based lipidomics and matrix-assisted laser desorption/ionization mass spectrometry imaging(MSI). The results revealed that MCTS, relative to 2D cells, had more shared lipid species with solid tumors. Furthermore,MCTS contained more comparable characteristics than 2D cells to solid tumors with respect to the relative abundance of most lipid classes and mass spectra patterns. MSI data showed that 46 of 71 lipids had similar spatial distribution between solid tumors and MCTS, while lipids in 2D cells had no specific spatial distribution. Interestingly, most of detected lipid species in sphingolipids and glycerolipids preferred locating in the necrotic region to the proliferative region of solid tumors and MCTS. Taken together, our study provides the evidence of lipid metabolism and distribution demonstrating that MCTS are a more suitable in vitro model to mimic solid tumors, which may offer insights into tumor metabolism and microenvironment.

Using pipette tips to readily generate spheroids comprising single or multiple cell types

Three-dimensional(3D)cell culture methods have been validated that can replicate the tumor environment in vivo to a large extent,providing an effective tool for studying tumors.In this study,we demonstrated the use of standard laboratory pipette tips as micro vessels for generating 3D cell spheroids.No microfabrication or wet-chemistry surface modifications were involved in the procedure.Spheroids consisting of single or multiple cell types were generated within 24 h just by pipetting and incubating a cell suspension in pipette tips.Scanning electron microscope and optical microscope proved that the cells grew together tightly,and suggested that while gravity force might have initiated the sedimentation of cells at the bottom of the tip,the active aggregation of cells to form tight cell-cell interactions drove the formation of spheroids.Using common laboratory micropipettes and pipette tips,the rate of spheroid generation and the generation reproducibility was characterized from five boxes each with 80 tips.The ease of transferring reagents allowed modeling of the growth of microvascular endothelial cells in tumor spheroids.Moreover,the pairing and fusion of tumor spheroids could be manipulated in the pipette tips,suggesting the potential for building and assembling heterogeneous micro-tumor tissues in vitro to mimic solid tumors in vivo.This study demonstrated that spheroids can be readily and cost-effectively generated in standard biological laboratories in a timely manner using pipette tips.

Therapeutic strategies of three-dimensional stem cell spheroids and organoids for tissue repair and regeneration

Three-dimensional(3D)stem cell culture systems have attracted considerable attention as a way to better mimic the complex interactions between individual cells and the extracellular matrix(ECM)that occur in vivo.Moreover,3D cell culture systems have unique properties that help guide specific functions,growth,and processes of stem cells(e.g.,embryogenesis,morphogenesis,and organogenesis).Thus,3D stem cell culture systems that mimic in vivo environments enable basic research about various tissues and organs.In this review,we focus on the advanced therapeutic applications of stem cell-based 3D culture systems generated using different engineering techniques.Specifically,we summarize the historical advancements of 3D cell culture systems and discuss the therapeutic applications of stem cell-based spheroids and organoids,including engineering techniques for tissue repair and regeneration.

Cellulose nanofibril matrix drives the dynamic formation of spheroids

Multicellular spheroids,which mimic the natural organ counterparts,allow the prospect of drug screening and regenerative medicine.However,their application is hampered by low processing efficiency or limited scale.This study introduces an efficient method to drive rapid multicellular spheroid formation by a cellulose nanofibril matrix.This matrix enables the facilitated growth of spheroids(within 48 h)through multiple cell assembly into size-controllable aggregates with well-organized physiological microstructure.The efficiency,dimension,and conformation of the as-formed spheroids depend on the concentration of extracellular nanofibrils,the number of assembled cells,and the heterogeneity of cell types.The above strategy allows the robust formation mechanism of compacted tumoroids and hepatocyte spheroids.

Function of hepatocyte spheroids in bioactive microcapsules is enhanced by endogenous and exogenous hepatocyte growth factor

The ability to maintain functional hepatocytes has important implications for bioartificial liver development,cell-based therapies,drug screening,and tissue engineering.Several approaches can be used to restore hepatocyte function in vitro,including coating a culture substrate with extracellular matrix(ECM),encapsulating cells within biomimetic gels(Collagen-or Matrigel-based),or co-cultivation with other cells.This paper describes the use of bioactive heparin-based core-shell microcapsules to form and cultivate hepatocyte spheroids.These microcapsules are comprised of an aqueous core that facilitates hepatocyte aggregation into spheroids and a heparin hydrogel shell that binds and releases growth factors.We demonstrate that bioactive microcapsules retain and release endogenous signals thus enhancing the function of encapsulated hepatocytes.We also demonstrate that hepatic function may be further enhanced by loading exogenous hepatocyte growth factor(HGF)into microcapsules and inhibiting transforming growth factor(TGF)-β1 signaling.Overall,bioactive microcapsules described here represent a promising new strategy for the encapsulation and maintenance of primary hepatocytes and will be beneficial for liver tissue engineering,regenerative medicine,and drug testing applications.

Porous nanofibrous dressing enables mesenchymal stem cell spheroid formation and delivery to promote diabetic wound healing

Delayed and nonhealing of diabetic wounds imposes substantial economic burdens and physical pain on patients.Mesenchymal stem cells(MSCs)promote diabetic wound healing.Particularly when MSCs aggregate into multicellular spheroids,their therapeutic effect is enhanced.However,traditional culture platforms are inadequate for the efficient preparation and delivery of MSC spheroids,resulting in inefficiencies and inconveniences in MSC spheroid therapy.In this study,a three-dimensional porous nanofibrous dressing(NFD)is prepared using a combination of electrospinning and homogeneous freeze-drying.Using thermal crosslinking,the NFD not only achieves satisfactory elasticity but also maintains notable cytocompatibility.Through the design of its structure and chemical composition,the NFD allows MSCs to spontaneously form MSC spheroids with controllable sizes,serving as MSC spheroid delivery systems for diabetic wound sites.Most importantly,MSC spheroids cultured on the NFD exhibit improved secretion of vascular endothelial growth factor,basic fibroblast growth factor,and hepatocyte growth factor,thereby accelerating diabetic wound healing.The NFD provides a competitive strategy for MSC spheroid formation and delivery to promote diabetic wound healing.

Spheroid construction strategies and application in 3D bioprinting

Tissue engineering has been striving toward designing and producing natural and functional human tissues.Cells are the fundamental building blocks of tissues.Compared with traditional two-dimensional cultured cells,cell spheres are threedimensional(3D)structures that can naturally form complex cell–cell and cell–matrix interactions.This structure is close to the natural environment of cells in living organisms.In addition to being used in disease modeling and drug screening,spheroids have significant potential in tissue regeneration.The 3D bioprinting is an advanced biofabrication technique.It accurately deposits bioinks into predesigned 3D shapes to create complex tissue structures.Although 3D bioprinting is efficient,the time required for cells to develop into complex tissue structures can be lengthy.The 3D bioprinting of spheroids significantly reduces the time required for their development into large tissues/organs during later cultivation stages by printing them with high cell density.Combining spheroid fabrication and bioprinting technology should provide a new solution to many problems in regenerative medicine.This paper systematically elaborates and analyzes the spheroid fabrication methods and 3D bioprinting strategies by introducing spheroids as building blocks.Finally,we present the primary challenges faced by spheroid fabrication and 3D bioprinting with future requirements and some recommendations.