Andrew Pelling has a new application for the apple, but it is not the latest i-gizmo from Cupertino, CA. Pelling and colleagues at the University of Ottawa have come up with a possible solution to the limitations of traditional, two-dimensional (2D) cell culture, which does not reproduce the microenvironment and tissue architecture that surrounds cells in a living organism—the apple, the one-a-day fruit that keeps the doctor away and is an essential ingredient to the All-American pie. Pelling believes that apples have something to offer beyond health benefits; apples could revolutionize the fields of cell culture and tissue engineering by providing a low-cost and sustainable alternative to synthetic three-dimensional (3D) culture systems. The fruit tissue of apples can be manipulated into reliable 3D culture scaffolding, say the researchers, who have recently published their findings in PLoS One. Such applications would also be easily scalable for high-throughput screening.
They did not start with apples though. “We looked at different vegetables…plants with very nice tissue, but not so much the fleshy fruits.” Pelling notes, “and potatoes are too starchy, which may cause cytotoxicity.” He got the idea to explore vegetables as a scaffold for 3D cell culture from an approach he refers to as “biohacking,” which he describes as, “making things happen that do not exist in nature.” He adds that the idea for using apples came from a graduate student who “just happened to see one of our undergraduates eating one.”
Pelling and his colleagues bought some McIntosh apples, placed them at -20°C to make them easier to slice, then cored and sliced them into 0.5-mm sections with a kitchen mandolin. They then cut the slices into pieces small enough to fit in a 24-well culture dish and treated them with a 0.5% SDS solution that removed any cells and nucleic acids, but left the 3D cellulose matrix of the fruit intact.
After washing the apple sections and equilibrating them in culture media, the group compared the growth and morphology of three cell lines, representing different cell types: NIH3T3 (fibroblasts), C2C12 (myoblasts), and HeLa (epithelial), cultured on this scaffolding over a period of 12 weeks. They also observed the effects of changing the elasticity of the decellularized apple matrix by treating it with collagen or glutaraldehyde. In all cases, the cells migrated into the apple matrix and proliferated to densities comparable to those observed for cells cultured on other natural or synthetic matrices, and exhibited normal morphology.
The decellularized apple matrix consists mostly of cellulose, the glycosidic bonds of which are not easily digested and thus do not contribute much nutritional energy to the culture media. This property, in addition to the apple matrix’s porosity, which allows for efficient gas exchange and nutrient transport, make the apple well suited as a 3D cell culture scaffold. “Apples are a very low-impact and renewable resource, and there already are products out there derived from cellulose that have been used for 2D culture,” adds Pelling.
The ease with which the elasticity of the apple matrix can be controlled is important for cell migration and differentiation studies. Pelling mentions recent work where stem cells were observed to change their differentiation programs in response to changes in the elasticity of the culture scaffold: “There are mechanical properties in the cell’s microenvironment at the nano or micro level. We would like to change these properties and see how much we can control.”
Pelling considers the abundance of apples, however, to be their most promising attribute as 3D cell culture scaffolding. “We think of these as open source biomaterials. There are a lot of proprietary biomaterials out there and the cost is prohibitive, especially for people working in developing countries who want to do tissue engineering.”
The apple that hit Newton on the head revolutionized the field of mechanics. Could this simple fruit now have a similar impact on cell culture? Again, Pelling and his group aren’t just limiting themselves to apples. “Carrots also seem to have good physical characteristics for supporting cell proliferation.” Perhaps Bugs Bunny will be the Newton of cell culture.
Modulevsky DJ, Lefebvre C, Haase K, Al-Rekabi Z, & Pelling AE (2014). Apple derived cellulose scaffolds for 3D mammalian cell culture. PloS one, 9 (5) PMID: 24842603
About the Author:
Nicholas is a freelance science writer.