Xeno-free pre-vascularized spheroids for therapeutic applications

Tumoroids, a valid preclinical screening platform for monitoring cancer angiogenesis

In recent years, biologists and clinicians have witnessed prominent advances in in vitro 3D culture techniques related to biomimetic human/animal tissue analogs. Numerous data have confirmed that unicellular and multicellular (tumoroids) tumor spheroids with dense native cells in certain matrices are sensitive and valid analytical tools for drug screening, cancer cell dynamic growth, behavior, etc. in laboratory settings. Angiogenesis/vascularization is a very critical biological phenomenon to support oxygen and nutrients to tumor cells within the deep layer of solid masses. It has been shown that endothelial cell (EC)-incorporated or -free spheroid/tumoroid systems provide a relatively reliable biological platform for monitoring the formation of nascent blood vessels in micron/micrometer scales. Besides, the paracrine angiogenic activity of cells within the spheroid/tumoroid systems can be monitored after being treated with different therapeutic approaches. Here, we aimed to collect recent advances and findings related to the monitoring of cancer angiogenesis using unicellular and multicellular tumor spheroids. Vascularized spheroids/tumoroids can help us in the elucidation of mechanisms related to cancer formation, development, and metastasis by monitoring the main influencing factors.

Vascular units as advanced living materials for bottom-up engineering of perfusable 3D microvascular networks

The timely establishment of functional neo-vasculature is pivotal for successful tissue development and regeneration, remaining a central challenge in tissue engineering. In this study, we present a novel (micro)vascularization strategy that explores the use of specialized "vascular units" (VUs) as building blocks to initiate blood vessel formation and create perfusable, stroma-embedded 3D microvascular networks from the bottom-up. We demonstrate that VUs composed of endothelial progenitor cells and organ-specific fibroblasts exhibit high angiogenic potential when embedded in fibrin hydrogels. This leads to the formation of VUs-derived capillaries, which fuse with adjacent capillaries to form stable microvascular beds within a supportive, extracellular matrix-rich fibroblastic microenvironment. Using a custom-designed biomimetic fibrin-based vessel-on-chip (VoC), we show that VUs-derived capillaries can inosculate with endothelialized microfluidic channels in the VoC and become perfused. Moreover, VUs can establish capillary bridges between channels, extending the microvascular network throughout the entire device. When VUs and intestinal organoids (IOs) are combined within the VoC, the VUs-derived capillaries and the intestinal fibroblasts progressively reach and envelop the IOs. This promotes the formation of a supportive vascularized stroma around multiple IOs in a single device. These findings underscore the remarkable potential of VUs as building blocks for engineering microvascular networks, with versatile applications spanning from regenerative medicine to advanced in vitro models.

Transplantation of olfactory mucosa mesenchymal stromal cells repairs spinal cord injury by inducing microglial polarization

STUDY DESIGN

Animal studies OBJECTIVES: To evaluate the therapeutic effect of olfactory mucosa mesenchymal stem cell (OM-MSCs) transplantation in mice with spinal cord injury (SCI) and to explore the mechanism by which OM-MSCs inhibit neuroinflammation and improve SCI.

SETTING

Xiangya Hospital, Central South University; Affiliated Hospital of Guangdong Medical University.

METHODS

Mice (C57BL/6, female, 6-week-old) were randomly divided into sham, SCI, and SCI + OM-MSC groups. The SCI mouse model was generated using Allen's method. OM-MSCs were immediately delivered to the lateral ventricle after SCI using stereotaxic brain injections. One day prior to injury and on days 1, 5, 7, 14, 21, and 28 post-injury, the Basso Mouse Scale and Rivlin inclined plate tests were performed. Inflammation and microglial polarization were evaluated using histological staining, immunofluorescence, and qRT-PCR.

RESULTS

OM-MSCs originating from the neuroectoderm have great potential in the management of SCI owing to their immunomodulatory effects. OM-MSCs administration improved motor function, alleviated inflammation, promoted the transformation of the M1 phenotype of microglia into the M2 phenotype, facilitated axonal regeneration, and relieved spinal cord injury in SCI mice.

CONCLUSIONS

OM-MSCs reduced the level of inflammation in the spinal cord tissue, protected neurons, and repaired spinal cord injury by regulating the M1/M2 polarization of microglia.

Metabolic Priming as a Tool in Redox and Mitochondrial Theragnostics

Theragnostics is a promising approach that integrates diagnostics and therapeutics into a single personalized strategy. To conduct effective theragnostic studies, it is essential to create an in vitro environment that accurately reflects the in vivo conditions. In this review, we discuss the importance of redox homeostasis and mitochondrial function in the context of personalized theragnostic approaches. Cells have several ways to respond to metabolic stress, including changes in protein localization, density, and degradation, which can promote cell survival. However, disruption of redox homeostasis can lead to oxidative stress and cellular damage, which are implicated in various diseases. Models of oxidative stress and mitochondrial dysfunction should be developed in metabolically conditioned cells to explore the underlying mechanisms of diseases and develop new therapies. By choosing an appropriate cellular model, adjusting cell culture conditions and validating the cellular model, it is possible to identify the most promising therapeutic options and tailor treatments to individual patients. Overall, we highlight the importance of precise and individualized approaches in theragnostics and the need to develop accurate in vitro models that reflect the in vivo conditions.

Engineering Cell Microenvironment Using Nanopattern-Derived Multicellular Spheroids and Photo-Crosslinked Gelatin/Hyaluronan Hydrogels

Cell cultures of dispersed cells within hydrogels depict the interaction of the cell-extracellular matrix (ECM) in 3D, while the coculture of different cells within spheroids combines both the effects of cell-cell and cell-ECM interactions. In this study, the cell co-spheroids of human bone mesenchymal stem cells/human umbilical vein endothelial cells (HBMSC/HUVECs) are prepared with the assistance of a nanopattern, named colloidal self-assembled patterns (cSAPs), which is superior to low-adhesion surfaces. A phenol-modified gelatin/hyaluronan (Gel-Ph/HA-Ph) hydrogel is used to encapsulate the multicellular spheroids and the constructs are photo-crosslinked using blue light. The results show that Gel-Ph/HA-Ph hydrogels with a 5%-to-0.3% ratio have the best properties. Cells in HBMSC/HUVEC co-spheroids are more favorable for osteogenic differentiation (Runx2, ALP, Col1a1 and OPN) and vascular network formation (CD31+ cells) compared to HBMSC spheroids. In a subcutaneous nude mouse model, the HBMSC/HUVEC co-spheroids showed better performance than HBMSC spheroids in angiogenesis and the development of blood vessels. Overall, this study paves a new way for using nanopatterns, cell coculturing and hydrogel technology for the generation and application of multicellular spheroids.

Automated Camera Lucida Method with Colored Images through Integration of Hardware and Software in Microscopic Zooming

Automating the camera Lucida method which is a standard way for focusing microscopic images is a very challenging study for many scientists. Hence, actually combining hardware and software to automate microscopic imaging systems is one of the most important issues in the field of medicine as well. This idea reduces scanning time and increases the accuracy of user's results in this field. Closed-loop control system has been designed and implemented in the hardware part to move the stage in predefined limits of 15°. This system produces 50 consecutive images from parasites at the mentioned spatial distances in two directions of the z-axis. Then, by introducing our proposed relational software with combining images, a high-contrast image can be presented. This colored image is focused on many subparts of the sample even with different ruggedness. After implementing the closed-loop controller, stages movement was repeated eight times with an average step displacement of 20 μm which were measured in two directions of the z-axis by a digital micrometer. On average, the movement's error was 1 μm. In software, the edge intensity energy index has been calculated for image quality evaluation. The standard camera Lucida method has been simulated with acceptable results based on experts' opinions and also mean squared error parameters. Mechanical movement in stage has an accuracy of about 95% which will meet the expectations of laboratory user. Although output-focused colored images from our combining software can be replaced by the traditional fully accepted Camera Lucida method.

Opposing MMP-9 Expression in Mesenchymal Stromal Cells and Head and Neck Tumor Cells after Direct 2D and 3D Co-Culture

Bone marrow-derived mesenchymal stromal cells (BMSCs) respond to a variety of tumor cell-derived signals, such as inflammatory cytokines and growth factors. As a result, the inflammatory tumor microenvironment may lead to the recruitment of BMSCs. Whether BMSCs in the tumor environment are more likely to promote tumor growth or tumor suppression is still controversial. In our experiments, direct 3D co-culture of BMSCs with tumor cells from the head and neck region (HNSCC) results in strong expression and secretion of MMP-9. The observed MMP-9 secretion mainly originates from BMSCs, leading to increased invasiveness. In addition to our in vitro data, we show in vivo data based on the chorioallantoic membrane (CAM) model. Our results demonstrate that MMP-9 induces hemorrhage and increased perfusion in BMSC/HNSCC co-culture. While we had previously outlined that MMP-9 expression and secretion originate from BMSCs, our data showed a strong downregulation of MMP-9 promoter activity in HNSCC cells upon direct contact with BMSCs using the luciferase activity assay. Interestingly, the 2D and 3D models of direct co-culture suggest different drivers for the downregulation of MMP-9 promoter activity. Whereas the 3D model depicts a BMSC-dependent downregulation, the 2D model shows cell density-dependent downregulation. In summary, our data suggest that the direct interaction of HNSCC cells and BMSCs promotes tumor progression by significantly facilitating angiogenesis via MMP-9 expression. On the other hand, data from 3D and 2D co-culture models indicate opposing regulation of the MMP-9 promoter in tumor cells once stromal cells are involved.

New Born Calf Serum Can Induce Spheroid Formation in Breast Cancer KAIMRC1 Cell Line

Three-dimensional (3D) cell culture systems have become very popular in the field of drug screening and discovery. There is an immense demand for highly efficient and easy methods to produce 3D spheroids in any cell format. We have developed a novel and easy method to produce spheroids from the newly isolated KAIMRC1 cell line in vitro. It can be used as a 3D model to study proliferation, differentiation, cell death, and drug response of cancer cells. Our procedure requires growth media supplemented with 10% new born calf serum (NBCS) and regular cell culture plates to generate KAIMRC1 spheroids without the need for any specialized 3D cell culture system. This procedure generates multiple spheroids within a 12–24-h culture. KAIMRC1 spheroids are compact, homogeneous in size and morphology with a mean size of 55.8 µm (±3.5). High content imaging (HCI) of KAIMRC1 spheroids treated with a panel of 240 compounds resulted in the identification of several highly specific compounds towards spheroids. Immunophenotyping of KAIMRC1 spheroids revealed phosphorylation of FAK, cJUN, and E-cadherin, which suggests the involvement of JNK/JUN pathway in the KAIMRC1 spheroids formation. Gene expression analysis showed upregulation of cell junction genes, GJB3, DSC1, CLDN5, CLDN8, and PLAU. Furthermore, co-culture of KAIMRC1 cells with primary cancer-associated-fibroblasts (CAFs) showcased the potential of these cells in drug discovery application.

Perspectives on scaling production of adipose tissue for food applications

With rising global demand for food proteins and significant environmental impact associated with conventional animal agriculture, it is important to develop sustainable alternatives to supplement existing meat production. Since fat is an important contributor to meat flavor, recapitulating this component in meat alternatives such as plant based and cell cultured meats is important. Here, we discuss the topic of cell cultured or tissue engineered fat, growing adipocytes in vitro that could imbue meat alternatives with the complex flavor and aromas of animal meat. We outline potential paths for the large scale production of in vitro cultured fat, including adipogenic precursors during cell proliferation, methods to adipogenically differentiate cells at scale, as well as strategies for converting differentiated adipocytes into 3D cultured fat tissues. We showcase the maturation of knowledge and technology behind cell sourcing and scaled proliferation, while also highlighting that adipogenic differentiation and 3D adipose tissue formation at scale need further research. We also provide some potential solutions for achieving adipose cell differentiation and tissue formation at scale based on contemporary research and the state of the field.

Heterotypic Multicellular Spheroids as Experimental and Preclinical Models of Sprouting Angiogenesis

Sprouting angiogenesis is the common response of live tissues to physiological and pathological angiogenic stimuli. Its accurate evaluation is of utmost importance for basic research and practical medicine and pharmacology and requires adequate experimental models. A variety of assays for angiogenesis were developed, none of them perfect. In vitro approaches are generally less physiologically relevant due to the omission of essential components regulating the process. However, only in vitro models can be entirely non-xenogeneic. The limitations of the in vitro angiogenesis assays can be partially overcome using 3D models mimicking tissue O2 and nutrient gradients, the influence of the extracellular matrix (ECM), and enabling cell-cell interactions. Here we present a review of the existing models of sprouting angiogenesis that are based on the use of endothelial cells (ECs) co-cultured with perivascular or other stromal cells. This approach provides an excellent in vitro platform for further decoding of the cellular and molecular mechanisms of sprouting angiogenesis under conditions close to the in vivo conditions, as well as for preclinical drug testing and preclinical research in tissue engineering and regenerative medicine.

Engineering injectable vascularized tissues from the bottom-up: Dynamics of in-gel extra-spheroid dermal tissue assembly

Modular tissue engineering approaches open up exciting perspectives for the biofabrication of vascularized tissues from the bottom-up, using micro-sized units such as spheroids as building blocks. While several techniques for 3D spheroid formation from multiple cell types have been reported, strategies to elicit the extra-spheroid assembly of complex vascularized tissues are still scarce. Here we describe an injectable approach to generate vascularized dermal tissue, as an example application, from spheroids combining fibroblasts and endothelial progenitors (OEC) in a xeno-free (XF) setting. Short-term cultured spheroids (1 day) were selected over mature spheroids (7 days), as they showed significantly higher angiogenic sprouting potential. Embedding spheroids in fibrin was crucial for triggering cell migration into the external milieu, while providing a 3D framework for in-gel extra-spheroid morphogenesis. Migrating fibroblasts proliferated and produced endogenous ECM forming a dense tissue, while OEC self-assembled into stable capillaries with lumen and basal lamina. Massive in vitro interconnection between sprouts from neighbouring spheroids rapidly settled an intricate vascular plexus. Upon injection into the chorioallantoic membrane of chick embryos, fibrin-entrapped pre-vascularized XF spheroids developed into a macrotissue with evident host vessel infiltration. After only 4 days, perfused chimeric capillaries with human cells were present in proximal areas, showing fast and functional inosculation between host and donor vessels. This method for generating dense vascularized tissue from injectable building blocks is clinically relevant and potentially useful for a range of applications.

Engineering microvasculature by 3D bioprinting of prevascularized spheroids in photo-crosslinkable gelatin

To engineer tissues with clinically relevant dimensions by three-dimensional bioprinting, an extended vascular network with diameters ranging from the macro- to micro-scale needs to be integrated. Extrusion-based bioprinting is the most commonly applied bioprinting technique but due to the limited resolution of conventional bioprinters, the establishment of a microvascular network for the transfer of oxygen, nutrients and metabolic waste products remains challenging. To answer this need, this study assessed the potential and processability of spheroids, containing a capillary-like network, to be used as micron-sized prevascularized units for incorporation throughout the bioprinted construct. Prevascularized spheroids were generated by combining endothelial cells with fibroblasts and adipose tissue-derived mesenchymal stem cells as supporting cells. To serve as a viscous medium for the bioink-based deposition by extrusion printing, spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) and Irgacure 2959. The influence of gelMA encapsulation, the printing process and photo-crosslinking conditions on spheroid viability, proliferation and vascularization were analyzed by live/dead staining, immunohistochemistry, gene expression analysis and sprouting analysis. Stable spheroid-laden constructs, allowing spheroid outgrowth, were achieved by applying 10 min UV-A photo-curing (365 nm, 4 mW cm^-2), while the construct was incubated in an additional Irgacure 2959 immersion solution. Following implantationin ovoonto a chick chorioallantoic membrane, the prevascular engineered constructs showed anastomosis with the host vasculature. This study demonstrated (a) the potential of triculture prevascularized spheroids for application as multicellular building blocks, (b) the processability of the spheroid-laden gelMA bioink by extrusion bioprinting and (c) the importance of photo-crosslinking parameters post printing, as prolonged photo-curing intervals showed to be detrimental for the angiogenic potential and complete vascularization of the construct post printing.

The Ultrastructural Analysis of Human Colorectal Cancer Stem Cell-Derived Spheroids and Their Mouse Xenograft Shows That the Same Cells Types Have Different Ratios

Spheroids from primary colorectal cancer cells and their mice xenografts have emerged as useful preclinical models for cancer research as they replicate tumor features more faithfully as compared to cell lines. While 3D models provide a reliable system for drug discovery and testing, their structural complexity represents a challenge and their structure-function relationships are only partly understood. Here, we present a comparative ultrastructural and flow citometric analysis of patient colorectal cancer-derived spheroids and their mice xenografts. Ultrastructural observations highlighted that multicellular spheroids and their xenografts contain the same cancer cell types but with different ratios, specifically multicellular spheroids were enriched in cells with a stem-like phenotype, while xenografts had an increased amount of lipid droplets-containing cells. The flow cytometric analysis for stem cell marker and activity showed enrichment of stem-like cells presence and activity in spheroids while xenografts had the inverse response. Our results evidence the effects on cancer cells of different in vitro and in vivo microenvironments. Those differences have to be paid into account in designing innovative experimental models for personalized drug testing.

Spheroid Coculture of Human Gingiva-Derived Progenitor Cells With Endothelial Cells in Modified Platelet Lysate Hydrogels

Cell coculture strategies can promote angiogenesis within tissue engineering constructs. This study aimed to test the angiogenic potential of human umbilical vein endothelial cells (HUVEC) cocultured with gingiva-derived progenitor cells (GPC) as spheroids in a xeno-free environment. Human platelet lysate (HPL) was used as a cell culture supplement and as a hydrogel matrix (HPLG) for spheroid encapsulation. HUVEC and HUVEC + GPC (1:1 or 5:1) spheroids were encapsulated in various HPLG formulations. Angiogenesis was assessed via in vitro sprouting and in vivo chick chorioallantoic membrane (CAM) assays. HUVEC revealed characteristic in vitro sprouting in HPL/HPLG and this was significantly enhanced in cocultures with GPC (p < 0.05). A trend for greater sprouting was observed in 5:1 vs 1:1 HUVEC + GPC spheroids and in certain HPLG formulations (p > 0.05). Both HUVEC and HUVEC + GPC spheroids in HPLG revealed abundant and comparable neoangiogenesis in the CAM assay (p > 0.05). Spheroid coculture of HUVEC + GPC in HPLG represents a promising strategy to promote angiogenesis.

Vascularized adipocyte organoid model using isolated human microvessel fragments

Tissue organoids are proving valuable for modeling tissue health and disease in a variety of applications. This is due, in part, to the dynamic cell-cell interactions fostered within the 3D tissue-like space. To this end, the more that organoids recapitulate the different cell-cell interactions found in native tissue, such as that between parenchyma and the microvasculature, the better the fidelity of the model. The microvasculature, which is comprised of a spectrum of cell types, provides not only perfusion in its support of tissue health, but also important cellular interactions and biochemical dynamics important in tissue phenotype and function. Here, we incorporate whole, intact human microvessel fragments isolated from adipose tissue into organoids to form both MSC and adipocyte vascularized organoids. Isolated microvessels retain their native structure and cell composition, providing a more complete representation of the microvasculature within the organoids. Microvessels expanded via sprouting angiogenesis within organoids comprised of either MSCs or MSC-derived adipocytes and grew out of the organoids when placed in a 3D collagen matrix. In MSC organoids, a ratio of 50 MSCs to 1 microvessel fragment created the optimal vascularization response. We developed a new differentiation protocol that enabled the differentiation of MSCs into adipocytes while simultaneously promoting microvessel angiogenesis. The adipocyte organoids contained vascular networks, were responsive in a lipolysis assay, and expressed the functional adipocyte markers adiponectin and PPARγ. The presence of microvessels promoted insulin receptor expression by adipocytes and modified IL-6 secretion following a TNF-alpha challenge. Overall, we demonstrate a robust method for vascularizing high cell-density organoids with potential implications for other tissues as well.

Strategies for re-vascularization and promotion of angiogenesis in trauma and disease

The maintenance of a healthy vascular system is essential to ensure the proper function of all organs of the human body. While macrovessels have the main role of blood transportation from the heart to all tissues, microvessels, in particular capillaries, are responsible for maintaining tissues' functionality by providing oxygen, nutrients and waste exchanges. Occlusion of blood vessels due to atherosclerotic plaque accumulation remains the leading cause of mortality across the world. Autologous vein and artery grafts bypassing are the current gold standard surgical procedures to substitute primarily obstructed vascular structures. Ischemic scenarios that condition blood supply in downstream tissues may arise from blockage phenomena, as well as from other disease or events leading to trauma. The (i) great demand for new vascular substitutes, arising from both the limited availability of healthy autologous vessels, as well as the shortcomings associated with small-diameter synthetic vascular grafts, and (ii) the challenging induction of the formation of adequate and stable microvasculature are current driving forces for the growing interest in the development of bioinspired strategies to ensure the proper function of vasculature in all its dimensional scales. Here, a critical review of well-established technologies and recent biotechnological advances to substitute or regenerate the vascular system is provided.

Morphological stability, cellular viability and stem cell marker expression of three-dimensional cultures of stem cells from bone marrow and periodontium

The aim of the present study was to evaluate the morphology, cellular viability and stem cell marker expression of three-dimensional cultures of bone marrow and gingiva-derived stem cells in different ratios. Stem cell spheroids were made with bone marrow and gingiva-derived stem cells using ratios of 6:0 (Group 1), 4:2 (Group 2), 3:3 (Group 3), 2:4 (Group 4) and 0:6 (Group 5), respectively. The viability of cell spheroids was analyzed using a Live/Dead kit assay and a Cell Counting Kit-8 assay. Total RNA extraction and reverse transcription-quantitative PCR were performed to detect the mRNA expression levels of Nanog and β-actin in each group. Stem cell spheroids were well formed in silicone elastomer-based concave microwells with different ratios of bone marrow and gingiva-derived stem cells. The shape of the spheroids and their viability were maintained throughout the entirety of the experimental procedure. Statistically significant increases in spheroid diameters were noted in Groups 4 and 5 on day 1 when compared with Group 1 on day 1. There was a significant increase in the cell viability values seen in Group 3 on day 1 when compared with Group 1 on day 1. Highest levels of Nanog expression was seen in Group 3 on day 10, but the increase was not significant when compared with Group 1 on day 1. Co-culturing with higher ratios of gingiva-derived stem cells produced stem cell spheroids with larger diameters and increased cellular viability. This co-culture technique may be used in stem cell therapy with allogenic stem cell transplantation.

Directed self-assembly of spheroids into modular vascular beds for engineering large tissue constructs

Spheroids can be used as building-blocks for bottom-up generation of artificial vascular beds, but current biofabrication strategies are often time-consuming and complex. Also, pre-optimization of single spheroid properties is often neglected. Here, we report a simple setup for rapid biomanufacturing of spheroid-based patch-like vascular beds. Prior to patch assembly, spheroids combining mesenchymal stem/stromal cells (MSC) and outgrowth endothelial cells (OEC) at different ratios (10:1; 5:1; 1:1; 1:5) were formed in non-adhesive microwells and monitored along 7 days. Optimal OEC retention and organization was observed at 1:1 MSC/OEC ratio. Dynamic remodelling of spheroids led to changes in both cellular and extracellular matrix components (ECM) over time. Some OEC formed internal clusters, while others organized into a peripheral monolayer, stabilized by ECM and pericyte-like cells, with concomitant increase in surface stiffness. Along spheroid culture, OEC switched from an active to a quiescent state, and their endothelial sprouting potential was significantly abrogated, suggesting that immature spheroids may be more therapeutically relevant. Non-adhesive moulds were subsequently used for triggering rapid, one-step, spheroid formation/fusion into square-shaped patches, with spheroids uniformly interspaced via a thin cell layer. The high surface area, endothelial sprouting potential, and scalability of the developed spheroid-based patches make them stand out as artificial vascular beds for modular engineering of large tissue constructs.

Extracellular vesicles from organoids and 3D culture systems

When discovered, extracellular vesicles (EVs) such as exosomes were thought of as junk carriers and a means by which the cell disposed of its waste material. Over the years, the role of EVs in cell communication has become apparent with the discovery that the nano-scale vesicles also transport RNA, DNA, and other bioactive components to and from the cells. These findings were originally made in EVs from body fluids of organisms and from in vitro two-dimensional (2D) cell culture models. Recently, organoids and other 3D multicellular in vitro models are being used to study EVs in the context of both physiologic and pathological states. However, standard, reproducible methods are lacking for EV analysis using these models. As a step toward understanding the implications of these platforms, this review provides a comprehensive picture of the progress using 3D in vitro culture models for EV analysis. Translational efforts and regulatory considerations for EV therapeutics are also briefly overviewed to understand what is needed for scale-up and, ultimately, commercialization.

Fibronectin rescues aberrant phenotype of endothelial cells lacking either CCM1, CCM2 or CCM3

Loss-of-function variants in CCM1/KRIT1, CCM2, and CCM3/PDCD10 are associated with autosomal dominant cerebral cavernous malformations (CCMs). CRISPR/Cas9-mediated CCM3 inactivation in human endothelial cells (ECs) has been shown to induce profound defects in cell-cell interaction as well as actin cytoskeleton organization. We here show that CCM3 inactivation impairs fibronectin expression and consequently leads to reduced fibers in the extracellular matrix. Despite the complexity and high molecular weight of fibronectin fibrils, our in vitro model allowed us to reveal that fibronectin supplementation restored aberrant spheroid formation as well as altered EC morphology, and suppressed actin stress fiber formation. Yet, fibronectin replacement neither enhanced the stability of tube-like structures nor inhibited the survival advantage of CCM3^-/- ECs. Importantly, CRISPR/Cas9-mediated introduction of biallelic loss-of-function variants into either CCM1 or CCM2 demonstrated that the impaired production of a functional fibronectin matrix is a common feature of CCM1-, CCM2-, and CCM3-deficient ECs.

Colorectal cancer triple co-culture spheroid model to assess the biocompatibility and anticancer properties of polymeric nanoparticles

Colorectal cancer (CRC) is the third most common and the second deadliest type of cancer worldwide, urging the development of more comprehensive models and of more efficient treatments. Although the combination of nanotechnology with chemo- and immuno-therapy has represented a promising treatment approach, its translation to the clinic has been hampered by the absence of cellular models that can provide reliable and predictive knowledge about the in vivo efficiency of the formulation. Herein, a 3D model based on CRC multicellular tumor spheroids (MCTS) model was developed by combining epithelial colon cancer cells (HCT116), human intestinal fibroblasts and monocytes. The developed MCTS 3D model mimicked several tumor features with cells undergoing spatial organization and producing extracellular matrix, forming a mass of tissue with a necrotic core. Furthermore, monocytes were differentiated into macrophages with an anti-inflammatory, pro-tumor M2-like phenotype. For a combined chemoimmunotherapy effect, spermine-modified acetalated dextran nanoparticles (NPs) loaded with the chemotherapeutic Nutlin-3a (Nut3a) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were produced and tested in 2D cultures and in the MCTS 3D model. NPs were successfully taken-up by the cells in 2D, but in a significant less extent in the 3D model. However, these NPs were able to induce an anti-proliferative effect both in the 2D and in the 3D models. Moreover, Nut3a was able to partially shift the polarization of the macrophages present in the MCTS 3D model towards an anti-tumor M1-like phenotype. Overall, the developed MCTS 3D model showed to recapitulate key features of tumors, while representing a valuable model to assess the effect of combinatorial nano-therapeutic strategies in CRC. In addition, the developed NPs could represent a promising approach for CRC treatment.

Spatial localization of endothelial cells in heterotypic spheroids influences Notch signaling

Cell-based therapeutic approaches are an exciting strategy to replenish compromised endothelial cell (EC) populations that contribute to impaired vasculogenesis. Co-cultures of ECs and mesenchymal stromal cells (MSCs) can enhance neovascularization over ECs alone, but the efficacy of cells is limited by rapid cell death upon implantation. Co-culture spheroids exhibit improved survival compared with monodisperse cells, yet little is known about the influence of spatial regulation of ECs within co-culture spheroids. We hypothesized that EC sprouting from co-culture spheroids is a function of EC spatial localization. We formed co-culture spheroids containing ECs and MSCs in two formats: ECs uniformly distributed throughout the spheroid (i.e., mixed) or seeded on the perimeter of the MSC core (i.e., shell). Qualitative observations suggested increased vasculogenesis for mixed co-culture spheroids compared with shell conformations as early as day 3, yet quantitative metrics did not reveal significant differences in network formation between these 3D structures. Notch3 expression demonstrated significant increases in cell-cell communication in mixed conformations compared with shell counterparts. Furthermore, knockdown of Notch3 in MSCs abrogated the vasculogenic potential of mixed spheroids, supporting its role in promoting EC-MSC contacts. This study highlights the direct impact of EC-MSC contacts on sprouting and provides insight to improve the quality of network formation. KEY MESSAGES: • Endothelial cell (EC) localization can be controlled in co-culture EC-MSC spheroids. • Mixed spheroids exhibit consistent networks compared to shell counterparts. • Differences in NOTCH3 were observed between mixed and shell spheroids. • NOTCH3 may be a necessary target for improved vasculogenic potential.

Advanced Bottom-Up Engineering of Living Architectures

Bottom-up tissue engineering is a promising approach for designing modular biomimetic structures that aim to recapitulate the intricate hierarchy and biofunctionality of native human tissues. In recent years, this field has seen exciting progress driven by an increasing knowledge of biological systems and their rational deconstruction into key core components. Relevant advances in the bottom-up assembly of unitary living blocks toward the creation of higher order bioarchitectures based on multicellular-rich structures or multicomponent cell-biomaterial synergies are described. An up-to-date critical overview of long-term existing and rapidly emerging technologies for integrative bottom-up tissue engineering is provided, including discussion of their practical challenges and required advances. It is envisioned that a combination of cell-biomaterial constructs with bioadaptable features and biospecific 3D designs will contribute to the development of more robust and functional humanized tissues for therapies and disease models, as well as tools for fundamental biological studies.

Analysis of the Effect of Increased α2,3-Sialylation on RTK Activation in MKN45 Gastric Cancer Spheroids Treated with Crizotinib

In the scenario of personalized medicine, targeted therapies are currently the focus of cancer drug development. These drugs can block the growth and spread of tumor cells by interfering with key molecules involved in malignancy, such as receptor tyrosine kinases (RTKs). MET and Recepteur d'Origine Nantais (RON), which are RTKs frequently overactivated in gastric cancer, are glycoprotein receptors whose activation have been shown to be modulated by the cellular glycosylation. In this work, we address the role of sialylation in gastric cancer therapy using an innovative 3D high-throughput cell culture methodology that mimics better the in vivo tumor features. We evaluate the response to targeted treatment of glycoengineered gastric cancer cell models overexpressing the sialyltransferases ST3GAL4 or ST3GAL6 by subjecting 3D spheroids to the tyrosine kinase inhibitor crizotinib. We show here that 3D spheroids of ST3GAL4 or ST3GAL6 overexpressing MKN45 gastric cancer cells are less affected by the inhibitor. In addition, we disclose a potential compensatory pathway via activation of the Insulin Receptor upon crizotinib treatment. Our results suggest that cell sialylation, in addition of being involved in tumor progression, could play a critical role in the response to tyrosine kinase inhibitors in gastric cancer.

3D microtissue-derived human stem cells seeded on electrospun nanocomposites under shear stress: Modulation of gene expression

OBJECTIVE

Different microenvironments trigger distinct differentiation of stem cells. Even without chemical supplementation, mechanical stimulation by shear stress may help to induce the desired differentiation. The cell format, such as three-dimensional (3D) microtissues (MTs), MT-derived cells or single cells (SCs), may have a pivotal impact as well. Here, we studied modulation of gene expression in human adipose-derived stem cells (ASCs) exposed to shear stress and/or after MT formation.

MATERIALS AND METHODS

Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) at a weight ratio of 60:40 were seeded with human ASCs as MTs or as SCs and cultured in Dulbecco's modified Eagle's medium without chemical supplementation. After 2 weeks of static culture, the scaffolds were cultured statically for another 2 weeks or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm^-2 min^-1. Stiffness of the scaffolds was assessed as a function of time. After 4 weeks, minimum stem cell criteria markers and selected markers of osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analysed by quantitative real-time polymerase chain reaction. Additionally, cell distribution within the scaffolds and the allocation of the yes-associated protein (YAP) in the cells were assessed by immunohistochemistry.

RESULTS

MTs decayed completely within 2 weeks after seeding on PLGA/aCaP. The osteogenic marker gene alkaline phosphatase and the endothelial cell marker gene CD31 were upregulated in MT-derived ASCs compared with SCs. Shear stress realised by fluid flow perfusion upregulated peroxisome proliferator-activated receptor gamma 2 expression in MT-derived ASCs and in SCs. The nuclear-to-cytoplasmic ratio of YAP expression was doubled under perfusion compared with that under static culture for MT-derived ASCs and SCs.

CONCLUSIONS

Osteogenic and angiogenic commitments were more pronounced in MT-derived ASCs seeded on bone biomimetic electrospun nanocomposite PLGA/aCaP than in SCs seeded without induction medium. Furthermore, the static culture was superior to the perfusion regimen used here, as shear stress resulted in adipogenic commitment for MT-derived ASCs and SCs, although the YAP nuclear-to-cytoplasmic ratio indicated higher cell tensions under perfusion, usually associated with preferred osteogenic differentiation.

Multicellular Human Gastric-Cancer Spheroids Mimic the Glycosylation Phenotype of Gastric Carcinomas

Cellular glycosylation plays a pivotal role in several molecular mechanisms controlling cell–cell recognition, communication, and adhesion. Thus, aberrant glycosylation has a major impact on the acquisition of malignant features in the tumor progression of patients. To mimic these in vivo features, an innovative high-throughput 3D spheroid culture methodology has been developed for gastric cancer cells. The assessment of cancer cell spheroids’ physical characteristics, such as size, morphology and solidity, as well as the impact of glycosylation inhibitors on spheroid formation was performed applying automated image analysis. A detailed evaluation of key glycans and glycoproteins displayed by the gastric cancer spheroids and their counterpart cells cultured under conventional 2D conditions was performed. Our results show that, by applying 3D cell culture approaches, the model cell lines represented the differentiation features observed in the original tumors and the cellular glycocalix underwent striking changes, displaying increased expression of cancer-associated glycan antigens and mucin MUC1, ultimately better simulating the glycosylation phenotype of the gastric tumor.

Fetal bovine serum-free culture of endothelial progenitor cells-progress and challenges

Two decades after the first report on endothelial progenitor cells (EPC), their key role in postnatal vasculogenesis and vascular repair is well established. The therapeutic potential of EPC and their growing use in clinical trials calls for the development of more robust, reproducible, and safer methods for the in vitro expansion and maintenance of these cells. Despite many limitations associated with its usage, fetal bovine serum (FBS) is still widely applied as a cell culture supplement. Although different approaches aiming at establishing FBS-free culture have been developed for many cell types, adequate solutions for endothelial cells, and for EPC in particular, are still scarce, possibly due to the multiple challenges that have to be faced when culturing these cells. In this review, we provide a brief overview on the therapeutic relevance of EPC and critically analyse the available literature on FBS-free endothelial cell culture methods, including xeno-free, serum-free, and chemically defined systems.