Reviewed by New Harvest Journal Club’s Tom Ben Arye and Francis Runge.
Abstract: To satisfy a growing global demand for animal meat and to alleviate animal suffering, alternatives to current methods of meat production are necessary. In vitro, or cultured meat, is one such alternative. While the idea of growing meat, or muscle, has been around for approximately 70 years, it is only recently that the search for viable solutions has intensified. Prospects for in vitro meat are encouraging, but are still far from reality, on an industrial scale. Researchers are pursuing scaffold-based and self-organizing techniques, and early results are promising, especially with regards to scaffold-based solutions. The engineering of animal muscle for consumption is not as difficult as the engineering of muscle for clinical purposes. Processed meat looks to be less difficult to produce than unprocessed meat, due to a lesser need for vascularization and nutrition. Research must now be focused on what the environmental cues are that are needed to promote myofiber development.
Overview: This paper provides a brief overview of cultured meat advancements until 2005. It discusses the cells that are involved, types of scaffolds, growth medium, bioreactors and the effect of different types of fields on the cells. Should we use embryonic stem cells or embryonic myoblast and satellite cells? Should we use scaffolds? How do we get rid of the serum? From where do we get the essential growth factors? These questions are discussed in the paper.
Key Points:
- Production: Scaffold-based and Self-organizing. Although scaffolds are used more often, it is probably more suited for processed meat. Scaffolds should be made from edible substance.
- Cells: Embryonic myoblasts/satellite cells, as of now (2005), are the most practical cell source. In order to replicate taste and texture of unprocessed meat we may need to add endothelial cells[1] for vascularization and fibroblasts (make the ECM[2] and connective tissue) to our cell culture in addition to the muscle and fat cells. Hayflick limit[3] of in farm animals not well established.
- Fields: Mechanical, electromagnetic, gravitational, and fluid flow fields have shown to be of assistance in proliferation and differentiation.
- Scaffolds: Flexible substratum or scaffold is needed. Processed meat could use sheets of membrane or narrowly spaced fibers. Unprocessed meat could use branching networks made from edible, elastic, and porous materials, or possibly angiogenesis[4] techniques.
- Growth factors: Since Serum containing media is expensive and animal based, serum free media (SFM) is needed for cultured meat production. The article notes few options. Lowering levels of mitogenic[5] growth factors assist in differentiation and fusion of myoblasts[6].
- Bioreactors: Though research is not at the industrial level, physics of current system should present no barriers to scaling up. Low-shear particle-based biofilm reactors are currently available for industrial scale. Current (2005) bioreactor can support macro scale tissues 1cm long.
- Conclusions: Cultured meat is technically feasible. However, significant challenges remain before it could be produced economically. Future research should be focused on developing scaffold-based techniques and affordable serum-free-media.
Notable Statistics:
- 79% proliferation of explant surface area when placed in culture containing dissociated goldfish skeletal muscle cells.
- Single-parent cell with Hayflick limit of 75 could satisfy current annual global demand for meat.
References
[1] Endothelial cells lines the interior surface of blood vessels.
[2] ECM – extracellular matrix – gel like environment in which cells live inside. Comprised of water, proteins and carbohydrates.
[3] Hayflick limit – the number of doublings a cell can undergo. If a cell can divide 10 times, it means that out of one cell we can get 2^10 = 1024 cells. It tells us how much meat we could get from a biopsy taken from animals.
[4] Angiogenesis – a process in which new blood vessels are formed.
[5] Mitogen – a chemical that promotes cell division
[6] Muscles tissues are usually made of myofibers – thousands of myoblast cells which are fused together.
