Introduction: Introduction
Cells and tissues in the body experience environmental conditions that influence their architecture, intercellular communications, and overall functions. For in vitro cell culture models to accurately mimic the tissue of interest, the growth environment of the culture is a critical aspect to consider. Commonly used conventional cell culture systems propagate epithelial cells on flat two-dimensional (2D) impermeable surfaces. Although much has been learned from conventional cell culture systems, many findings are not reproducible in human clinical trials or tissue explants, potentially as a result of the lack of a physiologically relevant microenvironment.
Methods: 3D cell Culture
In previous years, three‑dimensional (3D) cell culture technology has become a focus of research in tumor cell biology, using a variety of methods and materials to mimic the in vivo microenvironment of cultured tumor cells ex vivo. These 3D tumor cells have demonstrated numerous different characteristics compared with traditional 2D culture. 3D cell culture provides a useful platform for further identifying the biological characteristics of tumor cells, particularly in the drug sensitivity area of the key points of translational medicine. A 3D cell culture is an artificially created environment in which biological cells are permitted to grow or interact with their surroundings in all three dimensions. Unlike 2D environments, a 3D cell culture allows cells in vitro to grow in all directions, similar to how they would in vivo. It promises to be a bridge between traditional 2D culture and animal experiments, and is of great importance for further research in the field of tumor biology. Agitation-based culture systems are commonly proposed as an alternative method for 3D cell culture.
Results: 3D Cell Culture in Spinning flasks
Spinning flasks culture is a cell agitation approach based on stirred suspensions. An impeller mixer in the reactor tank prevents cells sedimentation and also promotes cell–cell interaction in the culture medium, Figure 2D. The spinning mechanism allows for sufficient supply of nutrients and soluble factors to cells while facilitating the excretion of wastes. This method is suitable for long term culture. However, the major limitation is the production of non-uniform spheroids. Furthermore, method needs the specialized equipment and consumes a large amount of medium (100–300 mL). Finally, for drug screening purposes, this method requires manual selection of spheroids to obtain a population with similar size.
Conclusion: 3D Cell Culture in Rotating wall vessel Bioreactor
Rotating wall vessel Bioreactor was developed by NASA in 1992 to study cell growth under simulated microgravity condition. Instead of stirring, rotary bioreactor rotates itself to maintain cells in a continuous suspension. The culture chamber rotates along the horizontal axis to prevent cells to adherence to the chamber wall. The speed of the rotation can be adjusted to exert low shear force, and at the same time to promote the optimal cell–cell adherence for a larger 3D structure. Once 3D aggregates are formed, continuous rotation at a desired speed prevents coalescence of the spheroids. This method enables the development of spheroids with approximately uniform sizes. Rotating vessel method ideally suits for long-term culture of 3D spheroids, because easy replacement of medium allows for efficient supply of nutrient and removal of waste. The main disadvantage of this method is the requirement of specialized equipment.