Large-Scale, Automated Production of Adipose-Derived Stem Cell Spheroids for 3D Bioprinting

Adipose-derived stromal/stem cells (ASCs) are a subpopulation of cells found in the stromal vascular fraction of human subcutaneous adipose tissue ...

Federal University of Rio de Janeiro

National Institute of Metrology, Quality and Technology (Inmetro)

Unigranrio

Top-down tissue engineering aims to produce functional tissues using biomaterials as scaffolds, thus providing cues for cell proliferation and differentiation. Conversely, the bottom-up approach aims to precondition cells to form modular tissues units (building-blocks) represented by spheroids. In spheroid culture, adult stem cells are responsible for their extracellular matrix synthesis, re-creating structures at the tissue level. Spheroids from adult stem cells can be considered as organoids, since stem cells recapitulate differentiation pathways and also represent a promising approach for identifying new molecular targets (biomarkers) for diagnosis and therapy. Currently, spheroids can be used for scaffold-free (developmental engineering) or scaffold-based approaches. The scaffold promotes better spatial organization of individual spheroids and provides a defined geometry for their 3D assembly in larger and complex tissues. Furthermore, spheroids exhibit potent angiogenic and vasculogenic capacity and serve as efficient vascularization units in porous scaffolds for bone tissue engineering. An automated combinatorial approach that integrates spheroids into scaffolds is starting to be investigated for macro-scale tissue biofabrication.

Adult Stem Cells Spheroids to Optimize Cell Colonization in Scaffolds for Cartilage and Bone Tissue Engineering.

Human adipose stem/stromal cell (ASC) spheroids were used as a serum-free in vitro model to recapitulate the molecular events and extracellular matrix organization that orchestrate a hypertrophic cartilage phenotype. Induced-ASC spheroids (ø = 450 µm) showed high cell viability throughout the period of culture. The expression of collagen type X alpha 1 chain (COLXA1) and matrix metallopeptidase 13 (MMP-13) was upregulated at week 2 in induced-ASC spheroids compared with week 5 (P < .001) evaluated by quantitative real-time PCR. In accordance, secreted levels of IL-6 (P < .0001), IL-8 (P < .0001), IL-10 (P < .0001), bFGF (P < .001), VEGF (P < .0001), and RANTES (P < .0001) were the highest at week 2. Strong in situ staining for collagen type X and low staining for TSP-1 was associated with the increase of hypertrophic genes expression at week 2 in induced-ASC spheroids. Collagen type I, osteocalcin, biglycan, and tenascin C were detected at week 5 by in situ staining, in accordance with the highest expression of alkaline phosphatase (ALPL) gene and the presence of calcium deposits as evaluated by Alizarin Red O staining. Induced-ASC spheroids showed a higher force required to compression at week 2 (P < .0001). The human ASC spheroids under serum-free inducer medium and normoxic culture conditions were induced to a hypertrophic cartilage phenotype, opening a new perspective to recapitulate endochondral ossification in vivo.

Scaffold- and serum-free hypertrophic cartilage tissue engineering as an alternative approach for bone repair.

Scaffold-free techniques in the developmental tissue engineering area are designed to mimic  embryonic processes with the aim of biofabricating, , 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 . 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.

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

The new coronavirus (2019-nCoV) or the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was officially declared by the World Health Organization (WHO) as a pandemic in March 2020. To date, there are no specific antiviral drugs proven to be effective in treating SARS-CoV-2, requiring joint efforts from different research fronts to discover the best route of treatment. The first decisions in drug discovery are based on 2D cell culture using high-throughput screening. In this context, spheroids and organoids emerge as a reliable alternative. Both are scaffold-free 3D engineered constructs that recapitulate key cellular and molecular events of tissue physiology. Different studies have already shown their advantages as a model for different infectious diseases, including SARS-CoV-2 and for drug screening. The use of these 3D engineered tissues as an in vitro model can fill the gap between 2D cell culture and in vivo preclinical assays (animal models) as they could recapitulate the entire viral life cycle. The main objective of this review is to understand spheroid and organoid biology, highlighting their advantages and disadvantages, and how these scaffold-free engineered tissues can contribute to a better comprehension of viral infection by SARS-CoV-2 and to the development of in vitro high-throughput models for drug screening.

Spheroids and organoids as humanized 3D scaffold-free engineered tissues for SARS-CoV-2 viral infection and drug screening.

As an alternative to the classical tissue engineering approach, bottom-up tissue engineering emerges using building blocks in bioassembly technologies. Spheroids can be used as building blocks to reach a highly complex ordered tissue by their fusion (bioassembly), representing the foundation of biofabrication. In this study, we analyzed the biomechanical properties and the fusion capacity of human adipose stem/stromal cell (ASC) we spheroids during an in vitro model of hypertrophic cartilage established by our research group. Hypertrophic induced-ASC spheroids showed a statistically significant higher Young's modulus at weeks 2 (P < .001) and 3 (P < .0005) compared with non-induced. After fusion, non-induced and induced-ASC spheroids increased the contact area and decreased their pairs' total length. At weeks 3 and 5, induced-ASC spheroids did not fuse completely, and the cells migrate preferentially in the fusion contact region. Alizarin red O staining showed the highest intensity of staining in the fused induced-ASC spheroids at week 5, together with intense staining for collagen type I and osteocalcin. Transmission electron microscopy and element content analysis (X-ray Energy Dispersive Spectroscopy) revealed in the fused quartet at week 3 a crystal-like structure. Hypertrophic induction interferes with the intrinsic capacity of spheroids to fuse. The measurements of contact between spheroids during the fusion process, together with the change in viscoelastic profile to the plastic, will impact the establishment of bioassembly protocols using hypertrophic induced-ASC spheroids as building blocks in biofabrication.

The hypertrophic cartilage induction influences the building-block capacity of human adipose stem/stromal cell spheroids for biofabrication.

Cancer is considered one of the most predominant diseases in the world and one of the principal causes of mortality per year. The cellular and molecular mechanisms involved in the development and establishment of solid tumors can be defined as tumorigenesis. Recent technological advances in the 3D cell culture field have enabled the recapitulation of tumorigenesis , including the complexity of stromal microenvironment. The establishment of these 3D solid tumor models has a crucial role in personalized medicine and drug discovery. Recently, spheroids and organoids are being largely explored as 3D solid tumor models for recreating tumorigenesis . In spheroids, the solid tumor can be recreated from cancer cells, cancer stem cells, stromal and immune cell lineages. Organoids must be derived from tumor biopsies, including cancer and cancer stem cells. Both models are considered as a suitable model for drug assessment and high-throughput screening. The main advantages of 3D bioprinting are its ability to engineer complex and controllable 3D tissue models in a higher resolution. Although 3D bioprinting represents a promising technology, main challenges need to be addressed to improve the results in cancer research. The aim of this review is to explore (1) the principal cell components and extracellular matrix composition of solid tumor microenvironment; (2) the recapitulation of tumorigenesis  using spheroids and organoids as 3D culture models; and (3) the opportunities, challenges, and applications of 3D bioprinting in this area.

Gabriela S. Kronemberger

Nucleus of Multidisciplinary Research in Biology (Numpex-Bio)

Federal University of Rio de Janeiro

Large-Scale, Automated Production of Adipose-Derived Stem Cell Spheroids for 3D Bioprinting

Gabriela S. Kronemberger

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Nucleus of Multidisciplinary Research in Biology (Numpex-Bio)

Federal University of Rio de Janeiro

Large-Scale, Automated Production of Adipose-Derived Stem Cell Spheroids for 3D Bioprinting

Nucleus of Multidisciplinary Research in Biology (Numpex-Bio)