Tissue culture is the ability to grow living cells in the laboratory, outside the body of the plant or animal from which the cells have been taken. By growing cells in a controlled environment, researchers can relatively easily manipulate, analyze and thus, better understand biological processes and their malfunction in disease.
A History Of Tissue Culture
Tissue culture was first performed in the early 20th century by the American scientist Ross Harrison. Harrison got his initial training in 1890 at Johns Hopkins under W. K. Brookes. Brookes was a meticulous and highly ethical researcher. Once he was informed by a visitor to his lab that he better hurry, since another scientist in France was doing the same work as he, and may soon publish. To most scientists, the thought of getting "scooped" this way would be a cause for grave concern (and rush to publish!). Brookes paused for a moment and remarked that he could never see a reason to rush research. If the French scientist did a better job, it was fine with him. If some thing was left out by the Frenchman, he would publish that part of his research so that it will complement the Frenchman's work. Harrison took this philosophy with him for the rest of his life.
In 1907, Harrison cultured embryonic frog nerve cells under aseptic conditions and maintained them nearly for a week, and later for about four weeks. He demonstrated that the nerve fibre is an outgrowth of the nerve cell itself. He was so elated by his discovery that he failed to realize for a long time that more important than his discovery of the origin of nerve fibre was his discovery of the method by which he could maintain embryonic nerve cells alive for weeks. In the latter half of 1907, Harrison was offered the Bronson professorship of Comparative Anatomy and chairmanship of the Department of Zoology at Yale. He remained at Yale for the rest of his long career. He continued to employ tissue culture techniques in his research and freely taught visiting scientists the methods he had developed.
In 1917, the Nobel Prize committee recommended Harrison for the prize. However due to the ongoing First World War, the Nobel Institute decided not to award a prize in physiology and medicine that year. Strangely it did award prizes for physics, literature and peace(!) that year. In 1933, his name was again short listed by Nobel committee along with T. H. Morgan for the prize. Morgan was awarded the prize (deservedly) but Harrison's claim was rejected on the flimsy ground that too many years had elapsed since the 1907 discovery. The Nobel committee did belatedly rectify this foolish notion of denying awards on the basis of passage of time by awarding the prize to Rous and then again to Chandrashekhar, decades after their seminal discoveries. However, this belated wisdom did not nullify the injustice to Harrison. Nobel or no Nobel, the discovery of tissue culture can be regarded as one of the ten greatest discoveries in the last 100 years in the field of Medicine. When Nichols, his successor at Yale wrote his memoirs of Harrison he ended it with a quotation from Psalm:1 --" Whatsoever he doeth shall prosper ".
Most people outside the tissue culture field and some tissue culturists also are under the impression that it was the French surgeon Alexis Carrel who pioneered the technique of tissue culture. Carrel was born and educated in Lyons,France, where later he headed the Department of Surgery in the medical school. In 1902, he made his most valuable contribution to medicine by inventing the first technique for suturing the cut ends of an artery and used it to perform a coronary bypass. Due to his difficult personality and extreme arrogance he had to leave France. He migrated to Montreal, Canada and then to the Hull Physiological Laboratories, Chicago. Carrel sent his assistant Dr. Montrose Burrows toYale to learn the tissue culture technique from Harrison. He published his first article on tissue culture in 1911 and made sure that it received world wide media attention. He cultured live embryonic Chicken heart cells and claimed that he could maintain them year after year on culture. Thus was born the legend of the immortal chicken heart. News paper editors used to call Carrel every New Year's day to find out how the chicken heart cells were doing. They published annual editorials celebrating the Immortal Chicken Heart. In 1912 Carrel was awarded the Nobel Prize for his surgical discoveries although the public at large and most scientists believed that it was awarded for his work on tissue culture. Many scientists accused Carrel of betraying Harrison and for accepting a prize which was rightfully Harrison's. But Harrison, being a thorough gentleman, defended Carrel's eligibility as he was aware that the prize was given for inventing a method for suturing cut ends of an artery.
The legend of the immortal chicken heart was put to an end by Leonard Hayflick. Hayflick began growing normal human cells and found that they could not survive on culture after certain fixed number of generations even if conditions are ideal. Later Carrel's technician confessed that Carrel's lab was introducing new live chicken heart cells to the culture regularly. The chicken heart cells were after all not immortal.
Although Carrel was a publicity seeking scientist, he was indirectly responsible for making people aware of Harrison's discovery of tissue culture. Carrel was a eugenicist. He believed in preserving the white race which he considered to be superior. He believed in getting rid of the inferior stock namely poor, uneducated and nonwhite. He later praised Hitler and collaborated with the Vichy government in France. However he died in 1944, before he could be indicted for his political crimes. Thus the problem of finding cells which could grow on a culture medium for ever under ideal conditions still remained unsolved. It was here that George and Margaret Gey entered the picture.
George Gey was head of tissue culture research at the Johns Hopkins Hospital in Baltimore. He, along with his wife Margaret, had spent three decades working to grow malignant human cells outside the body with the hope that this may help in finding cause and cure for cancer. In 1943 scientists at the National Institutes of Health had demonstrated that mouse cancer cells can be grown indefinitely in culture medium. The Geys wanted to grow first immortal human cells but had had little luck. In February 1951, when the samples from a cancer patient were received by Gey, his assistant Mary Kubicek was entrusted the job of growing these cells. She found that contrary to her expectations, these cells were growing at a very healthy rate and filled as much space as she gave them. Soon the Geys had millions of these cells and as long as nutrients were available in ideal conditions, they divided and redivided every 24 hours. It was then that the Geys realized that they had an immortal cell line. On 10th April 1951, in a television interview, George Gey announced that they had the ability to grow human cancer cells in very large numbers and they were using these cells to find ways to stop cancer. These are the so-called "HeLa" cells.
60 Years OF HeLa Cells
HeLa cells are named after Henrietta Lacks. She was (at the time of cell collection) a 31 year old black female suffering from cancer cervix. Her cervical cancer tumor was the original source of HeLa cells. In Johns Hopkins Hospital, Baltimore, Dr. TeLinde and his assistant Howard Jones were conducting a study on cancer cervix. Lacks was admitted to public ward of this hospital in February 1951. On 9th Feb. 1951, Dr. Lawrence Wharton collected two samples of tissue from cervix of Henrietta Lacks, one sample from her tumor and another sample from healthy cervical tissue nearby. As per instructions of TeLinde, the samples were given to George Gey who was the head of tissue culture research at Johns Hopkins, for growing the tissue in laboratory. As was quite customary in those days, consent of Henrietta Lacks for culturing her tissue was not taken. The patients from public wards often provided free material for medical research in those days and scientists regarded this as fair practice because they were treated free in these wards.
It was known that normal cells do not grow in culture for long periods. Even under ideal conditions, with adequate nutrient supply, normal cells can not divide forever on a culture medium. Usually, most normal cells die within a week or at the most a few weeks when they have undergone division for a certain number of generations. The HeLa cells were the first immortal human cells to be grown in laboratory. In culture medium, under ideal conditions, the HeLa cells divide and divide continuously and have been doing so since last 60 years. They are still growing in thousands of labs around the world. They proved to be so hardy that they could be mailed anywhere in world in viable condition. The mail packages containing HeLa cells were famously termed as "HeLagrams". Scientists all over the world loved these cells. Because they grew and multiplied very rapidly, they were perfect for experiments. It is believed that HeLa cell culture is one of the most important things that happened in the field of medicine in the 20th century. However there is another aspect of HeLa cells which is little known even to many biologists and biochemists. HeLa cells are cross-contaminants in a large number of tissue cultures, that is, they grow like a weed in culture of other cells. Moreover they grow so vigorously that they overwhelm the other cells. Therefore, they are a bane of researchers working with cell lines other than HeLa cells. They also interfere seriously in development and production of pure antivirus vaccines.
The HeLa Cells And Their Munificence
Soon the Geys started sending HeLa cells to any scientist who might use them for cancer research. Shipment of HeLa cells was made to almost every country in the world on scientific map. When scientists visited Geys lab, they learnt the technique to grow HeLa cells and while returning back took a vial or two of HeLa cells. According to some estimates weight of all HeLa cells ever grown is of the order of 50 million metric tons. The HeLa cells were so precious because experiments which could not be performed with living human body could be performed using them. Thus the HeLa cells were exposed to toxins, radiations,infectious agents and various anti-cancer drugs. They were useful in-
1)development of many chemotherapeutic drugs for cancer
2)study of immune suppression and cancer growth
3)development of vaccines, like the polio vaccine
4)development of methods of cloning
5)developing drugs for herpes, leukemia, influenza, hemophilia, Parkinsonism and several other disorders
6)study of aging and human longevity
7)study of gene mapping. Their chromosomes and genes have been extensively studied and some of their chromosomal bands serve as important markers. There are a number of other applications -some major and others minor like the study of lactose digestion.
HeLa Cells - The Other Face Of Janus
In 1966 Stanley Gartler, a geneticist from University of Washington, Seattle discovered an enzyme that occurred only in the cells of some black people. It was found to be present in the HeLa cells as well. Much to Gartler's astonishment, he found the same enzyme in at least 18 supposedly pure Caucasian cell lines. These cell lines were present in the cell bank established in Washington D.C. Some of them were incorrectly classified as tumours of the liver and other organs where as actually they were HeLa cells! Researchers who had been working on these 18 cell lines were furious as it would mean that their work of years would be flushed down the drain. Hence the claims of Gartler were termed as "wild and insolent " and he was completely ostracized. The Tissue Culture Association appointed two independent research teams to evaluate all the cell lines in the National Cell Bank. Out of 34 cell lines, 24 cell lines proved to be HeLa cells, thereby vindicating Gartler's claim.
Walter Nelson-Rees, a Cuban scientist working at National Cancer Institute, Oakland, was sent samples of some Russian cell lines for analysis during the Nixon era. He found that these cell lines were in fact HeLa cells. These cell lines were developed from contaminated cell samples which were sent to the soviet union by the US. The Nixon administration was worried that Nelson-Rees' conclusion may adversely affect the US-USSR dialogue and hence wanted to suppress the result. However Nelson-Rees disagreed and conveyed the result to the visiting soviet scientists. Instead of being upset , the Russians were pleased and sent him an invitation to visit Russia. Inspire of this,every Journal to which Nelson-Rees submitted his results rejected the paper fearing political consequences.
On another occasion Nelson-Rees discovered that five cell lines that were sent to him by various researchers were in fact HeLa cells. He sent a paper describing his results to "Science" -- the foremost scientific journal of the US. One reviewer said his data was correct. Another reviewer said the results were extremely important, and yet, the editor rejected the paper for no apparent reason. Later one of the cell culturists whose cell line Nelson-Rees had identified as HeLa confirmed Nelson-Rees finding. He sent a letter to twenty other researchers to whom he had sent the cell line admitting his mistake. A copy of the letter was also sent to Nelson-Rees. Now Nelson-Rees resubmitted the paper to "Science" along with a copy of the letter. The entire episode somehow also reached the media. This time the paper was accepted. However, it was printed in the very last pages of the journal. Later Nelson-Rees found more supposedly pure cell lines which were contaminated by HeLa cells. He claimed that as many as a third of the cell lines in the world were contaminated by HeLa cells. He wrote another article for "Science" enlisting the contaminated cell lines and added the name of the concerned researcher to the cell line. It can be imagined that Nelson-Rees immediately became an outcast and a pariah. Due to the stress to which he was continuously subjected Nelson-Rees voluntarily retired in 1981. In 1982, the excellent cell culture facility which he had established was closed by the federal government. The entire Nelson-Rees episode explodes the myth of objectivity in science. Like any other human activity the 'subjective' always asserts itself in scientific deliberations and judgement, too.
The contamination of cell lines by HeLa cells is not just an academic debate. It has serious consequences for the public at large. For example, we use normal cell cultures to determine permissible limits for exposure to radiation. We know that HeLa cells are highly resistant to radiation. If the normal cell culture is contaminated by HeLa cells then recommendations made on this basis will result in the exposure of patients to a higher radiation level than what is safe. It is estimated that the HeLa cell contamination has cost humanity millions and millions of dollars in wasted research. The HeLa cell contamination of cultures continues through out the world even today. Thus the HeLa cells have been a boon as well as a curse for tissue culturists. They also teach us that many of our discoveries have a flip side to them and therefore there is a need to handle new techniques and new technologies with great caution.
References :-
1)Conspiracy of cells-Michael Gold (Suny press)
2)Medicine's ten greatest discoveries -Friedman and Friedland
(University press)
3)immortal life of Henrietta Lacks-Rebecca Skloot(Crown publi. House)
4) www.yalealumnimagzine.com/issue02_02/old_yale
---an unsung hero of medical research
5)Ross Granville Harrison --Wikipedia
6)Alexis Carrel--Wikipedia
7)www.layers of learning.com/2011/01.../mad-scientist-Alexis-carrel.html
8)Walter Nelson-Rees--- Wikipedia
9)articles.sfgate.com/2009-01-28/bay-area/17197541_c-cells-uc-ber
10)HeLa --Wikipedia
Interesting historical sketch.
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