The story of Henrietta Lacks and her (unknowing) contribution to the advancement of science has recently been resurrected with the publication of The Immortal Life of Henrietta Lacks (reviewed in this issue). Despite the clear disenfranchisement of the Lacks family, HeLa cells have helped to revolutionize science as we know it. As someone who frequents a tissue culture hood on a daily basis, this book really sparked my curiosity about cell culture in general. Yes, I know what we do with cells today when using them as a model system to investigate numerous processes relating to health and disease, but how did it get to be this way? In this brief article, I hope to summarize some of the scientific breakthroughs that have brought us to both present day tissue culture theory and practice.

The principles of cell culture began over 100 years ago when the German zoologist Wilhelm Roux showed that the neural plate from chicken embryos could be removed and maintained in warm saline solution for several days¹. This novel concept was taken one step further by Ross Granville Harrison, an American born scientist and Yale professor who, in 1906, not only maintained amphibian nerve fibers ex vivo, but also developed conditions under which these nerve fibers were able to proliferate². The groundwork laid down by Harrison was built upon by Nobel Prize winning scientist Alexis Carrel who, at our very own Rockefeller University (then known as the Rockefeller Institute for Medical Research), was able to culture the heart of a chicken embryo for a period much longer than the normal lifespan of a chicken³. In fact, this experiment was quite sensational considering that this heart was kept alive for 34 years and actually outlived Dr. Carrel himself! These findings helped convince other scientists that in vitro experiments using animal cells were entirely possible and, thus, could be considered the cornerstone of tissue culture.

For the next several years, it was mainly tissue explants that were used for experimentation. However, due to the pioneering efforts of Katherine Sanford and colleagues, the concept of creating a population of cells from a single cell came to fruition⁴. In addition, Harry Eagle sealed the fate of the future of cell culture in 1955 by demonstrating that the tissue extracts used to grow cells could be replaced with a synthetic and defined nutrient mixture containing amino acids, vitamins, carbohydrates, salts, and serum⁵. Taken together, these technologies paved the way for a whole new approach to scientific investigation using in vitro systems including mutagenesis, cloning, and transformation. But, perhaps the largest impact on society, was the ability to use cell lines to grow purified viruses for vaccine production.

The idea that pure cell lines could be established and maintained indefinitely was finally concrete. These established cell lines mimicked, at least in part, the major functional and metabolic characteristics displayed by the cell from which they were originally obtained. Scientists were then able to study the cellular processes specific to particular organs and/or tissues with greater ease. Some examples of the cell lines established during this time were adrenal cells, pituitary cells, neurons, myocytes, and hepatocytes⁶. As more and more cell lines were “born,” scientists realized that each cell type required a specific nutrient mixture for optimal growth. Additionally, it was being discovered that serum could be replaced with specific proteins, hormones, and/or growth factors. As a result, experimental design became more complex and researchers began to ultra-specialize. As we all are aware, it is not uncommon for scientists to spend their entire careers studying one, or even one aspect, of a specific protein or pathway. This is likely how this came to be the norm.

The next major advancement in the history of cell culture occurred in the 1970s with the development of hybridoma cell lines, which could be used for the production of monoclonal antibodies⁷. This technology was developed by Cesar Milstein, Georges J. F. Köhler and Niels Kaj Jerne and resulted in an equally shared Nobel Prize in Medicine in 1984. Jumping ahead to the late 1990s, a time frame more in line with my own scientific existence (I was in kindergarten in 1984), we see the advent of stem cell biology and the associated bioethical debate. In my personal opinion, the enormous medical and commercial value as it relates to stem cells makes this a non-issue, but I digress from the point of this article. In 1998, stem-cell research was catapulted forward by the work of James Thomson (University of Wisconsin at Madison) and John Gearhart (Johns Hopkins University) who, independently of one another, pushed the limits of science by successfully growing human stem cells in culture. Currently, stem cell research is still in its adolescence and our understanding of how we can actually apply stem cell technologies is mediocre at best, although there are some very innovative (and inspiring) ideas out there. The hope, at the very least, is to generate entire tissues to aid in the treatment of some of the most devastating diseases. For example, scientists are working to generate insulin-producing pancreatic cells that can be used to cure type 1 diabetes.

What is on the horizon for tissue culture? Well, I would assume that the ultimate goal is to actually grow entire organs or organ systems. Is this even possible? Could transplant lists become a thing of the past? As this is being written, devoted researchers are trying to generate novel ways to utilize stem cells for improving human health. It is quite possible that we will see, in our very own lifetimes, the generation of new cardiac tissue to be used in heart attack victims and the ability for cancer patients undergoing chemotherapy and/or radiation treatments to receive replacement bone marrow and blood cells. Tissue engineering is the wave of the biomedical future. It was only one century ago that Wilhelm Roux maintained the first cells ex vivo. Considering where we are now, compared to the humble beginnings of cell culture, I do not foresee a negative impact on this inertia (barring any catastrophes resulting in major funding issues). Who knows, maybe we will see a breakthrough so instrumental that we will actually be around to see what will happen a hundred years from now. Now that’s truly becoming immortal.

References:

1. Hamburger V. Wilhelm Roux: visionary with a blind spot. J Hist Biol. 1997 Summer;30(2):229-38.
2. Nicholas JS. Ross Granville Harrison, 1870-1959. Yale J Biol Med. 1960 Jun;32:407-12.
3. Carrel A. On the Permanent Life of Tissues Outside of the Organism. J Exp Med. 1912 May 1;15(5):516-28.
4. Sanford KK, Earle WR, Likely GD. The growth in vitro of single isolated tissue cells. J Natl Cancer Inst. 1948 Dec;9(3):229-46.
5. Eagle H. Nutrition needs of mammalian cells in tissue culture. Science. 1955 Sep 16;122(3168):501-14.
6. Mather JP, Roberts PE. Introduction to cell and tissue culture : theory and technique. New York: Plenum Press; 1998.
7. Wade N. Hybridomas: the making of a revolution. Science. 1982 Feb 26;215(4536):1073-5.