3D culture

3D culture systems for disease modeling, drug screening, and regenerative medicine

Cell microenvironment consists of extracellular matrix, oxygen and nutrient gradients, and both cell-to-matrix and cell-to-cell interactions. In order to enhance biological research, the drug discovery process, and regenerative medicine applications, cells are now often cultured in a three-dimensional environment (3D) instead of two-dimensional monolayer cultures.

Recent advances in stem cell culture have made it possible to grow organoids; in vitro 3D tissues. Organoid protocols have been described for a variety of organs, including the digestive tract, kidney, and brain. The low success rate in clinical drug trials has shown the need for improved preclinical 3D culture systems that accurately represent in vivo conditions and tissue-specific characteristics, allowing drug safety and efficacy assessment from an earlier stage of drug development. 3D models applied to a high-throughput format are under development for large-scale screening systems.

Permeable Biosilk fiber network for defined and biocompatible 3D cell culture

Scientists have long been developing more reproducible 3D gel and network models in order to replace the previously commonly used xenogeneic matrix extracts, such as the ones derived from Engelbreth-Holm-Swarm mouse sarcoma tissue. Now scientists agree that these extracted matrices are too undefined and famously suffer from high batch-to-batch variability and xenogeneic origin, preventing robust protocols and clinical use. To accommodate these needs, Biolaminin and Biosilk products are animal origin-free and documented even for clinical use, in addition to giving prominent functional advantages for cell culture applications.

Biosilk is a recombinant spider silk biomaterial that has the ability to self-assemble into a microfibrous network, such as foam, and which can be easily biofunctionalized with different ECM proteins, like laminins. This helps to better recapitulate physiologically relevant aspects of developing human tissue. For example, Biosilk has been successfully used for the expansion of pluripotent stem cells and subsequent neural cell differentiation with additional Biolaminin 521 (Biosilk 521). A reproducible ventral midbrain organoid model, with functionally mature cells even in the core of the organoids, was generated with Biosilk and Biolaminin 111 (Fiorenzano et al. 2021).

The fibrillar Biosilk network allows the formation of channels throughout the 3D culture, which facilitates diffusion of oxygen, medium, and patterning factors (Åstrand et al. 2020). This enables long-term differentiation protocols and makes it possible to generate larger organoids with uniform cellular specialization and organization, without an increased risk of getting necrotic centers. Besides these advantages, Biosilk is also a biodegradable and non-immunogenic biomaterial, which facilitates future use in clinical applications. These advantages make Biosilk a great choice for successful 3D applications.

Hydrogel models with Biolaminin

Full-length laminins have proven to be crucial components for proper organoid formation also in gel models. For example, Gjorevski and co-authors (2016) showed that only the full-length laminin-111, and not laminin-derived peptides, is sufficient for intestinal organoid formation in a defined hydrogel matrix. By using different Biolaminin products, many culture systems can be fine-tuned to meet the tissue-specific characteristics of an in vivo-like microenvironment.

Dobre and co-authors (2021) developed a 3D culture system with a defined matrix composition that reflects the complexity of the native ECM, where growth factors in combination with Biolaminin isoforms give more natural cellular processes. The authors incorporated the full-length Biolaminin 521, 332, and 411 proteins into a synthetic polymer network with controlled physicochemical properties, and showed examples of hMSC osteogenesis and neurite growth in this 3D microenvironment. The study appreciated the tissue-specific interactions between full-length laminin isoforms and growth factors – laminins do not only support cell function by interacting directly, but also by binding with a large range of growth factors and presenting them effectively to the cells. This property makes laminins even more important components for tissue engineering.

Ye and coauthors (2020) reported a defined, nonimmunogenic hydrogel matrix utilizing Biolaminin-111 as a bioactive component for liver organoid culture. The authors show that LEC, which is derived from mouse sarcoma, can be replaced with the human recombinant Biolaminin-111 resulting in similar proliferative potential. This makes the liver organoid expansion system completely synthetic and potentially applicable even for clinical applications.

An economical and automated platform for the generation of human liver spheres was developed by Lucendo-Villarin and co-authors (2020). Stem cell-derived liver tissues with hepatic progenitors, endothelial cells, and hepatic stellate cells, differentiated with the help of Biolaminin 521, permit the study of human liver biology and can be scaled for drug screening. A detailed protocol for this effective model system was also published (Meseguer-Ripolles et al. 2021).