What is the Difference Between Organoids and Spheroids?

Organoids and spheroids are both 3D cell culture models, but they differ in complexity, structure, and applications. Here are the main differences between the two:

1. Complexity: Spheroids are spherical cellular units that are generally cultured as free-floating aggregates and are considered to be of low complexity in mirroring tumor organization. Organoids, on the other hand, are more complex structures that partially resemble the organ in both structure and function.
2. Structure: Organoids are cells grown in 3D to form structural units that resemble the original tissue both histologically and genetically. Spheroids, however, are formed primarily via cell-to-cell adhesion, resulting in cell aggregates.
3. Culture Methods: Spheroids can be derived from immortalized cell lines, primary cells, or fragments of human tissue. Organoids are formed using stem cells that self-renew and differentiate in vitro, driven by their self-organizing properties.
4. Applications: Organoids are used for a wide range of applications in cancer research, including the study of carcinogenesis, drug development, and personalized medicine. Spheroids are often used in radio- and immuno-therapies to predict patient responses.
5. Limitations: Spheroids are generally more resilient and capable of growing in vitro, which can affect drug response and produce data that poorly translates to the clinic. Organoids are considered to be more faithful recapitulations of in vivo features due to their multicellular identity and the ability of stem cells to differentiate into multiple cell types.

Comparative Table: Organoids vs Spheroids

Here is a table comparing the differences between organoids and spheroids:

Organoids are more complex 3D cell cultures that can mimic the structure and function of an organ, while spheroids are a simpler model system ideal for certain applications.